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222 Cards in this Set
- Front
- Back
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Who was responsible for the thought of epidemics, infection; founder of tuberculosis?
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Hippocrates
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Who found that epidemic diseases are caused by transferable tiny particles or "spores" via direct or indirect contact?
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Fracastoro
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Who was the founder of the transmission of syphilis & gonorrhea?
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John Hunter
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Who figured out that washing hands is of significant importance?
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Semmelweis
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Who demonstrated the contagiousness of cholera through contaminated water?
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Snow
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What are Koch's Postulates?
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To establish that an organism is the cause of a dz, it must be:
1.) Found in all cases of the dz examined, while absent in healthy organisms 2.) Prepared & maintained in a pure culture 3.) Capable of producing the original infection, even after several generations in culture. 4.) Retrievable from an inoculated animal & cultured again |
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Who is the "father of microscopy"?
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Leeuwenhoek
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Who founded that microbes are the cause of fermentation: invented a process in which liquids such as milk were heated to kill most bacteria & molds already present within them (pasteurization). Known as the father of germ theory & bacteriology
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Pasteur
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What is the cause of infection?
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Microbes
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What is described as the natural habitat for the organism in which it must propagate. Any person, animal, plant, soil or substance in which an infectious agent normally lives & multiplies?
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Reservoir of infection
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What is the habitat from which the organism is transmitted and in which it must survive but may or may not propagate. ie. feces, nasal secretions, vaginal secretions, semen, blood, pustules, etc.
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Immediate source of infection
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What are 7 modes of transmission?
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1.) Individual to individual spread
2.) Food-Borne Infections 3.) Waterborne Infections 4.) Airborne Infections 5.) Soil 6.) Hospital Acquired Infections (HAIs) 7.) Indirect via a vector |
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What are 7 ways microbes from individual to individual is spread?
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1.) Skin-to-skin contact
2.) Droplets during coughing, sneezing, or kissing 3.) Stool-to-mouth (fecal-oral) via dirty hands or utensils 4.) Sexually transmitted 5.) Blood-to-blood contact 6.) Spread from mother to fetus 7.) Autoinfection |
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The individual at risk of infection
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Susceptible host
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Describe the morphology of viruses.
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Acellular microbes; Not capable of any of the activities of other microbes such as metabolism; numerous shapes; enveloped/non-enveloped; only capable of replicating when they have infected particular cell types
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Comprised of cell capsule (+/-), cell wall & cytoplasmic membrane. Surrounds the cytoplasm of the prokaryotic cell
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Cell Envelope
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Amorphous, polymeric, often-gelatinous materials lying outside the cell wall.; antiphagocytic property; may prolong survival in the environment; antigenically diverse which is important in vaccine production & in lab diagnosis
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Capsule
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Basic differences b/t Gm + and Gm - bacteria. Give the organism its shape & a rigid structure protecting the cell's internal structures. Rigidity is provided by peptidoglycans; permeable.
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Cell wall
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Phospholipid bilayer; selectively permeable; involved in active transport of nutrients, respiration, excretion & chemoreception
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Cytoplasmic membrane (plasma membrane, cell membrane)
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A region in which the chromosome is physically located within the cell
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Nucleoid
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Bacterial surface layers; one of most abundant cell envelope surface components; simple structure composed of either a single protein or glycoprotein depending on the species
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S-layers
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Long whiplike structures of locomotion; comprised of 3 parts: filament, hook and basal body; highly antigenic; role in virulence - chemotaxis
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Flagella
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Shorter, straighter, and thinner than flagella; composed of protein pilin/fimbrin; role as receptor & adherence
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Pili or fimbriae (plural) (Pilus or fimbria is singluar)
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DNA, single circular structure with no nuclear membrane
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Chromosome
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RNA & protein; involved in protein synthesis; an attack site for some antibiotics such as tetracycline & gentamicin
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Ribosomes
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Important for transfer of antimicrobial resistance, virulence factors, etc.
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Plasmids
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Viruses that attack bacteria; insert their DNA into bacterial DNA for purposed of replication & may lyse or just replicate along with it. Can also transfer antimicrobial resistance, virulence factors, bacterial antigens, etc.
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Bacteriophages (phages)
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Chemical composition variable; present in some bacterial cells; may be composed of polyphosphate, poly-beta-hydroxybutyrate, glycogen
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Storage granules or inclusions
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Bacterial structure associated w/ invagination of the plasma membrane. Is the site of the respiratory enzymes; may also form as an artifact of fixation
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Mesosome
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What are the 5 basic morphologic forms of bacteria?
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Coccus, Rod, Spiral, Filamentous, Appendaged
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Spherical or ovoid
Staphylococci, Streptococci |
Coccus
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Straight and cylindrical
Pasteurella, Brucella, Haemophilus |
Rod
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Series of twists or turns & are tightly or loosely coiled
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Spiral
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Long, thin cells or chains of cells
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Filamentous
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Have extensions from the cell that are smaller than the diameter of the organism & contain cytoplasm & bound by the cell wall
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Appendaged
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Very rigid structure; some possess techoic acids; Staphylococcus, Streptococcus, Lactobacillus, Bacillus spp.
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Gram positive
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Polymers of glycerol phosphate or ribitol; attach to N-acetylmuramic acid, important in phage attachment and regulation of cell growth. Provide rigidity to the cell wall; dominant cell antigen in some bacteria
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Techoic acid
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Attached to glycolipid in the cell membrane; may serve as an anchor for the peptidoglycan. Amphiphiles, are excreted as vesicles thought to be involved in protein secretion, and exhibit at high concentrationss many of the lss toxic properties of endotoxins. Produce IL-6 and IL-10
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Lipoteichoic acids
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High in lipid content, thinner walled, appear as a unite membrane, thus it is called the outer membrane; have 3 layers in their cell walls & much less peptidoglycan; Borrelia, Treponema, Mycoplasma
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Gram-negative
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Proteins in the outer membrane that form pores or diffusion channels that allow the passage of small hydrophilic molecules
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Porins
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Contains porins and receptors for phages; may contain proteases & other enzymes, aggressins, evasins, and toxins for host cells; shields from lysozyme. Less permeable to hydrophobic and amphipathic molecules thus making Gm- bacteria less susceptible to antibiotics.
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Outer Membrane
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What is the toxic component of the lipid moiety of lipopolysaccharides (LPS)
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Lipid A
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Substitutes dark-field condensor for the conventional condenser, which obliquely reflects a powerful source of light onto a wet preparation, where small objects scatter light and can be seen brilliant images against a dark background
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Dark-field microscopy
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Light waves passing through transparent objects, such as cells, emerge in different phases, depending on the properties of the material through which they pass. Useful in studying the fine detail of unstained living microorganisms
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Phase-contrast microscopy
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Detects microorganisms that are stained with various fluorescent dyes; widely used in clinical microbiology for the identification of microorganisms
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Fluorescent microscopy
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Instead of visible light, a beam of electrons is focused by an electromagnetic field instead of by glass lenses; short wavelength
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Electron microscopy
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Used for demonstrating morphology & size of stained bacteria & fungi; stained bacterial smears & wet mounts; staining affinity may allow preliminary classification of bacteria & the morphology of fungal structures permits identification of the genus; has 3 objectives
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Brightfield Microscopy
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Types of stains used on bacteria that can be visualized using Brightfield microscopy
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Gram stain, Kinyoun stain for partial acid fast bacteria, and Ziehl-Neelsen stain for true acid-fast organisms
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Differentiates b/t Gm+ and Gm- organisms on the basis of differences in the structure of their cell wall. Gm + blue, thick cell wall composed of mainly peptidoglycan & teichoic acids. Gm- stain red, outer membrane & periplasmic space with small amount of peptidoglycan
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Gram Stain
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Gram Stain procedure
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1) Fixed by heat
2) Crystal/methyl violet 3) iodine solution (mordent); rinse with water 4) decolorize with acetone/ethyl alcohol 5) counterstain with safranin |
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organisms retain the basic dye following decolorization & appear deep violet
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Gram +
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Organisms do not retain the basic dye but take up the counterstain (safranin) and stain red/pink
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Gram -
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"seed"; have capacity to produce highly resistant, thick-walled spores; occur when vegetative cells are deprived of some factor or nutrient necessary for growth
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Spores
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Describe the formation of spores
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1) Realignment of DNA materials into filaments & invagination of plasma membrane, forming forespore
2) Forespore surrounded by plasma membrane 3) Forming endospore surrounded by double membrane 4)The facing side of the 2 plasma membranes is the peptidoglycan synthesizing side, and spore cortex 5) Spore coat is formed outside the spore cortex 6) Once spore formation is complete, mature spore is released by the disintegration of the envelope of the mother cell (sporangium) |
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Each spore germinates into how many vegetative cells when conditions for growth are favorable?
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Single
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What is germination of spored brought about by? (4)
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1) Heat
2) Aging 3) Damage to coat 4) Presence of adequate moisture |
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The remarkable resistence of spores is thought to be due to what 4 things?
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1) layered structure
2) dehydrated state 3) negligible metabolic activity 4) high content of dipicolinic acid |
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Not found in vegetative cells, occurs in spore wall in combo with large amounts of calcium
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Dipicolinic acid
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Resist heat & can be boiled; resist disinfectants; relatively impervious; not susceptible to antibiotics; can be destroyed with certainty only by moist heat at 121C for 15 minuts
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Spores
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Used for identifying microorganisms at the species and strain levels. Restriction enzymes are used to cut a molecule of DNA at locations where a specific base sequence occurs. Resulting restriction fragments are separated by gel electrophoresis
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DNA fingerprinting
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Genes & operons controlled by the same regulator constitute what?
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a regulon
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Distinct class of genomic islands located on bacterial chromosomes or may be part of a plasmid; acquired by horizontal gene transfer (transformation, transduction, bacterial conjugation)
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Pathogenicity islands (PAIs)
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Mobile DNA elements that can capture & carry genes, particularly those responsible for antibiotic resistance; do so by site-specific recombination. The antibiotic resistence genes they capture are located on gene cassettes.
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Integrons
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Science of classifying organisms
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Taxonomy
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Groups of organisms with similar genetic & metabolic characteristics
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Species
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Group of related genera; classified based on constitutive characteristics,cellular characteristics, cultural characteristics, & biochemical characteristics
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Family (aceae)
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group of related species. also subgenera
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genus
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contains strains of bacteria that have many characteristics in common
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Species
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Further subdivision of some species on the basis of small but consistent differences
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Subspecies
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Consists of descendants (clone) of a single isolate in pure culture; for each species, there is a type strain, which usually is the particular culture from which the species description was originally made
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Strain
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Strain with special biochemical or physiologic properties; differentiated on the basis of some type of biological difference
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Biovar, biotypes
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Strain with distinctive antigenic properties. Differentiated on the basis of their antigens
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Serovar
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Latin: Firmus, strong & cutis, skin, referring to the cell wall: Gm + bacteria
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Division Firmicutes
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Gram-negative bacteria
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Division Gracilicutes
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Gram-negative cell wall free bacteria
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Division Tenericutes
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Capable of living & reproducing either inside or outside cells
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Facultative intracellular parasite
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Cannot reproduce outside their host cell, parasites reproduction is entirely reliant on intracellular resources
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Obligate intracellular parasite
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Classified based on constitutive characteristics, cellular characteristics (Gm -), cultural characteristics (facultative anaerobic, growth on blood agar, growth on MAC agar) & biochemical characteristics (oxidase-negative, saccharolytic). Normal enteric flora
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Family Enterobacteriaceae
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what are 3 genera characteristics?
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1) Gram stain
2) cellular morphology 3) atmospheric growth requirements |
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Strains with distinctive antigenic properties; differentiated on the basis of their antigens
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Serovars
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Name and describe the 4 bacterial antigens
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1) Capsular (K): Carbohydrate, a surface antigen external to the cell wall
2) Fimbriae (F): Protein 3) Flagellar (H): Protein 4) Somatic (O): Carbohydrate, antigen located in cell wall |
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Constitutive components of gram negative cell wall-free bacteria
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1) Lack cell wall
2) Cytoplasm w/ chromosome & ribosomes 3) Cytoplasmic membrane composed of proteins & sterols. Cholesterol in membrane provides for osmotic stability |
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Changes in cell wall composition, induced by the action of lysozyme or of antibiotics leaves structures that remain bound by the cytoplasmic membrane only and are called what? They lack rigidity and are susceptible to osmotic change
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Protoplasts (Gm +) or Spheroplasts (Gm -)
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Pathogenic bacteria w/out cell walls
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L forms
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Well-defined structure closely adherent to the cell wall. Amorphous, polymeric, often-gelatinous materials lying outside the cell wall. Most composed of polysaccharide, but those of several species consist of polypeptide; some have both. They are antigenically diverse. Main function is for protection of the bacterium from adverse environmental conditions. Antiphagocytic.
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Capsule
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What are the requirements to destroy spores?
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Moist heat at 121 C for 15 minutes
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Thin delicate covering made of protein
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Exosporium
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Composed of layers of spore specific proteins
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Spore Coat
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Composed of loosely linked peptidoglycan & contains dipicolinic acid (DPA).
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Cortex
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Contains cell wall, cytoplasmic membrane, nucleoid, & cytoplasm. Only has 10-30% of water content of vegetative cells, so is in a gel state. Survives in acidic environments
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Core
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Formed during sporulation & bind to DNA in the core. Protect DNA from UV light, desiccation, & dry heat. Serve as a carbon energy source during germination
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Small acid soluble spore proteins (SASPs)
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Process of converting a spore back to a vegetative cell
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Germination
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When the vegetative cell forms the endospore
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Sporogenesis
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3 stages of germination
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1) Activation: occurs in response to factors such as brief exposure to heat, abrasion of spore coat or environmental acidity.
2) Initiation: Occurs if other environmental conditions (presence of adequate nutrients favorable). Spore cortex & coat are degraded, water is absorbed, calcium dipicolinate is released & outgrowth develops. 3) Outgrowth: period of active biosynthesis & terminate w/ division of the new vegetative cell |
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Long, filamentous appendages that arise at the level of the cytoplasmic membrane & extend through the wall into the surrounding medium. Responsible for motility. Usually found in rod-shaped Gm - bacteria
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Flagella
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How do flagella differ in their numbers & arrangements on cells?
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1) Polar
2) Peritrichous 3) Periplasmic |
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Single polar flagellum
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Monotrichous
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2 or more flagella originating at one pole or point
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Lophotrichous
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Single flagellum located at 2 diff points or poles
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Amphitrichous
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2 or more (a tuft) flagella at 2 points or poles of the cell
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Amphilophotrichous
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FLagella arising over the entire cell surface
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Peritrichous
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Gram - spriochetes. Aids in motility by rorating the spriochete
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Periplasmic
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3 parts to a flagella
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1) Filament
2) Hook 3) Basal Body |
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Composed of protein flagellin to form a hollow cylinder. Monomers of the protein are synthesized & passed through the lumen of the cylinder, at the growing tip of the flagellum helix, the monomer undergoes a conformational change & becomes added to the distal end of the flagellum
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Flagellar filament
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Acts as a sleeve from which flagellar filament emerges; allows the transmission of a rotary motion from the basal body to the filament
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Hook
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Composed of complex rings connected by a rod-shaped structure; Ring structure attached to cell membrane rotates as a part of an energy-dependent reaction, causing the rigid flagellar helix to turn like a propellar
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Basal Body
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Ability of a flagellated organism to alter the expressed antigenic type of flagella they produce; differential expression of genes coding for variously structured flagellin proteins
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Phase variation
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Flagellar antigens in Gm - bacteria are referred to as what?
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"H antigens"
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Smaller appendages found on the surface of many Gm - bacteria. Serve as attachment sites for bacteriophages
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Fimbriae/Pili
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Any non-flagellar hairlike appendages
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Fimbriae
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Used to denote the fimbriae of Gm - bacteria that function specifically in the transfer of DNA form one cell to another during conjugation
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Pili
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Function as organelles for attachment to cells or mucosal surfaces
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Adhesions
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The only mechanism of genetic exchange between bacteria that requires cell-to-cell contact
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Conjugation
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How do Gm - bacteria transfer genetic material?
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They possess a plasmid called the F plasmid that codes for a sex pilus
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How do Gm + bacteria transfer genetic material?
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Via a co-aggregation of the organisms in response to production of pheromones by the donor bacterium. Under stimulation by these pheromones, potential recipient bacteria synthesize a receptor molecule that is specific for a conjugative adhesin present on the donor cell. Aggregation results in the establishment of the cell-to-cell connections necessary for plasmid mobilization to occur.
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Is there conjugation b/t Gm - and Gm + bacteria?
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No
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The exchange of genetic info via bacteriophages
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Transduction
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Uptake of free exogenous dsDNA from the surrounding environment
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Transformation
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Describe Gm - bacterial conjugation with the F plasmid.
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Once contact of an F+ cell with an F- cell is established by the sex pilus, the circular F plasmid begins to be replicated. During this process, one of the single strands of the plasmid DNA is passed through the pilus into the recipient cell. The single strand that is passed begins to be repliacted as it enters the recipient cell, and the end result is 2 cells that contain complete conjugative plasmids (both become F+ cells)
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After infecting the bacterial cell, the phage regulatory genes "take over" the cellular biosynthetic machinery, resulting in the expression of phage structural genes & the production of new phage particles that are released on lysis & death of the host bacterium.
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Lytic bacteriophages
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Genetic material of the bacteriophage becomes incorporated into the host cell DNA as a "prophage" & replicates along with the bacterial chromosome
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Temperate bacteriophage (lysogenic bacteriophage)
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Any time a lysogenic bacterium is exposed to adverse conditions, the lysogenic state can be terminated. This is called what?
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Induction
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Name some conditions which favor the termination of the lysogenic state.
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1) Desiccation
2) Exposure to UV or ionizing radiation 3) Exposure to mutagenic chemicals |
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What are the components of a bacteriophage?
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Head
Collar Tail Base plate Fibrils |
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Small genetic elements located in the cytoplasm & can replicate independently. Majority are circular & composed of dsDNA. Can carry multiple genes.
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Plasmids
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Plasmid of bacteria or viral DNA that can integrate itself into the chromosomal DNA of the host organism
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Episome
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Plasmids can carry genes encoding for what?
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1) Antibiotic resistance
2) Virulence factors 3) Metabolic activities 4) Cryptic plasmids (plasmids without any functional genes) |
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Require oxygen for growth. Use oxygen to oxidize substance in order to obtain energy. Incapable of supporting growth from the energy supplied by fermentation. All accomplish a respiratory type of metabolism & use only oxygen as a terminal electron acceptor. Have the advantage of yielding more energy than obligate anaerobes, but face high levels of oxidative stress.
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Obligate aerobic bacteria
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Bacteria grow in either the presence or absence of air, but they grow better when oxygen is present. Can be found on the skin or in the gut
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Facultative anaerobic bacteria
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Organisms lack the ability to grow in the presence of air & often even small amounts of oxygen are toxic. Ex: Bacteroides, Clostridium, Fusobacterium. Lack ability to remove toxic forms of oxygen.
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Obligate anaerobic bacteria
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Used to determine the atmospheric requirements of the obligate aerobic bacteria, facultative anaerobic bacteria & obligate anaerobic bacteria.
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Aerotolerance tests
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Air + Carbon Dioxide. Require the presence of CO2 to survive but require low concentrations of oxygen. Can be found in intestinal tract, respiratory tract, etc.
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Capnophilic
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Candle jar, oxygen is less than atmosphere
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Microaerophilic
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Atmosphere for anaerobic bacteria
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10% CO2, 10%H, 80%N
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Organic molecule is final hydrogen receptors, 2ATP + acids, alcohols, etc.
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Fermentation
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Oxygen is final hydrogen receptor, 38ATP, CO2, H2O
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Aerobic Respiration
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Other inorganics, besides oxygen, are final hydrogen receptor, 34 ATP + NH3 + H2S, etc.
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Anaerobic Respiration
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Organisms that are incapable of using either light or inorganic compounds as an energy source or of using CO2 as a sole carbon source. Require more complex materials such as sugars, AAs, FAs, or NAs as sources of energy & carbon sources for growth. (An organism that cannot synthesize its own food & is dependent on complex organic substances for nutrition)
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Heterotrophs
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Heterotrophs that live on dead or decaying organic matter.
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Saprophytes
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Live on or in another living organism and derive nutrition from the host
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Parasites
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Doesn't cause disease
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Commensal parasite
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Normally harmless in their usual environment but cause dz when they gain access to other sites or tissues
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Opportunist parasite
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Must cause dz in order to be transmitted from one host to another. Must also infect a host in order to survive. (ex: Mycobacterium tuberculosis & Treponema pallidum)
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Obligate pathogen
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Bacteria that can obtain carbon & energy by hydrolysis of carbohydrate molecules
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Saccharolytic bacteria
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INability to metabolize carbohydrates
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Asaccharolytic Bacteria
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Optimum growth from 25C to 40C (77-104F) Contains most known organsims
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Mesophilic bacteria
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Optimal incubation temp <20C (<68F)
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Psychrophilic bacteria
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Optimal incubation temp >40C (>104F)
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Thermophilic bacteria
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Optimal incubation temp >100C (>212F)
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Hyperphilic bacteria
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What is the optimal pH range for bacterial growth?
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7.2-7.4
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Organisms damage tissues while they are outside phagocytes & other cells. They do not have the capacity to survive for long periods in phagocytic cells (Ex: Klebsiella & Pasteurella sp)
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Extracellular pathogens
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Not confined to cells, but they can survive, and in some instances multiply, in phagocytic cells. Phagocytes may also destroy the parasite & prevent or ultimately eliminate infection
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Facultative Intracellular pathogens
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Chlamydia, rickettsia, and viruses. Can only propagate within cells
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Obligate Intracellular pathogens
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What is happening in the lag phase for bacterial growth?
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Following innoculation of bacterial cells into fresh broth medium. 2 important characteristics of this phase:
1) Cells are rapidly making new DNA & RNA and inducing the synthesis of new enzymes needed for cell division & thus, there is a great deal of metabolic activity taking place 2) There is no increase in cell numbers. |
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What is happening in the logarithmic or exponential growth phase?
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Cell division occurs at a maximum rate for the growth conditions provided by the medium & environmental conditions. Cell numbers are increasing (doubling) at an exponential rate
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What is taking place in the stationary growth phase?
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Cells may run out of nutrients, or cell waste products may build up to toxic levels, or the population density may become so great that the rate of diffusion of nutrients b/t cells becomes limiting. Then the rate of cell division slows below exponential levels.
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What happens during the decline or death growth phase?
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Eventually, cells begin to die, initiating the decline or death phase. Rate of cell death in the population is exponential.
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Loss of a cell's ability to form a colony when transferred to a plate
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Cell Death
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Rate of cell division during exponential growth. Time it takes for one doubling in cell numbers.
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Generation Time or Doubling Time
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An asexual process that divides bacteria into two equal progeny cells. The chromosomes, which have doubled in number preceding the division, are distributed equally to the 2 daughter cells.
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Binary Fission
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A microbe capable of causing dz
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Pathogen
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The capacity of a microbe to produce dz
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Pathogenicity
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Degree of pathogenicity
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Virulence
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Microbial products that permit a pathogen to cause dz
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Virulence factor (or Determinant)
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4 routes of exposure to pathogenic bacteria
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1) Inhalation, ingestion
2) Sexual, other direct contact 3) Wounds, other injuries 4) Insect, animal bites |
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6 bacterial interactions with the host:
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1) Adherence (fimbriae/pili)
2) Invasion 3) Initial multiplication 4) Evasion of defense - specific, nonspecific 5) Spread of infection 6) Damaging the host |
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Bacterial virulence factors include?
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1) Surface structures
2) Antigenic variation 3) Invasive pathogens 4) Endotoxins 5) Toxins 6) Extracellular enzymes 7) Iron (essential nutrient for growth & metabolism of nearly all microorganisms) 8) Intracellular pathogens |
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Bacterial surface structures/virulence factors:
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1) Capsules: Antiphagocytic
2) Fimbriae: Colonization of tissues 3) Cell Wall Antigen: Gm - & Bm + 4) Cytoplasmic membrane: Gm -, cell wall-free bacteria |
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The capsules of mucoid strains of Pasteurella multocida & Steptococcus equi consist almost wholly of what?
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Hyaluronic acid.
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What are the 2 types of virulence factors needed to develop dz enterotoxigenic E. coli?
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1) Fimbrial adhesions
2) Enterotoxins |
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Responsible for bovine contagious pyelonephritis. Members possess fimbriae which allow attachment to the urogenital mucosa
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Corynebacterium renale
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Virulent strains, when isolated form cases of infectious bovine keratoconjunctivitis, are fimbriate, haemolytic & grow into the agar. Virulence is attributed to fimbriae, which allow adherence of the organisms to the cornea, circumventing the protective effects of lacrimal secretions & blinking
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Moraxella bovis
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4 bacterial adherence attachment sites:
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1) Keratinized or mucosal epithelium
2) Specialized epitheilum (ocular, aural) 3) Chitin 4) Cell membrane components |
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Most important protein of the cell wall, which is responsible for virulence. Responsible for type-specific immunity, inhibits phagocytosis & has an immunotoxic effect on polymorphs and platelets
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M Protein
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What are the main components of LPS molecules?
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Core polysaccharides bound to lipid A & long external polysaccharide side chains
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What do the polysaccharide side chains do for the LPS molecule?
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Sitmulate antibody production & correspond to the somatic (O) antigens used for serotyping of Gm - bacteria.
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Full-length O chains render the bacterial cell (smooth/rough)?
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Smooth
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Absence or shortening of the O chain renders the bacterial cell (smooth/rough)?
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Rough
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Which bacterial cell strain is more antiphagocytic? Smooth or rough?
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Smooth strains
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Repeat unit; highly immunogenic in a vertebrate animal
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O antigen
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Genetic makeup of an organism or group of organisms with reference to a single trait, set of traits, or an entire complex of traits
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Genotype
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Observable constitution of an organism; the appearance of an organism resulting from the interaction of the genotype & the environment
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Phenotype
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Why is it an advantage for an organism to exist on or near the surface of a eukaryotic cell?
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From this location it can produce toxins & derive nutrients while avoiding most of the mechanisms of the humoral acid cellular immune systems
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Organisms that reside outside of eukaryotic cells; are readily killed once phagocytized
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Extracellular parasites
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Those organisms that have the capacity to grow & survive both inside & outside of eukaryotic cells. May survuve long periods of time inside cells
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Facultative Intracellular parasites
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those which can grow only within cells
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Obligate or strict intracellular parasites
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List (& give examples) of ways bacteria may gain entry to deeper tissues:
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1) Trauma/puncture: Clostridium tetani
2) Endocytosis: Salmonella typhimurium 3) Receptor mediated endocytosis: Chlamydophila psittaci 4) Uptake by antigen sampling sites: Salmonella 5) Disruption by cytotoxins: Salmonella 6) Direct penetration: Leptospira |
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An acute infectious dz caused by bacteria Corynebacterium diphtheriae. The throat infection causes a gray to black, tough, fiber-like covering pseudomembrane which can block the airways
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Diphtheria
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Cell damage & death are ultimately dependent on what 3 things?
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1) What cells are involved: neural, heart, skin, etc.
2) How many cells are infected: mild vs. fulminating 3) How fast the infection proceeds; rate of damage vs rate of repair |
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Endotoxins do not act directly on cells. Rather, they bind to what?
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CD14
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If the CD14 is on the surface of a macrophage, the macrophage is stimulated to produce what? What is it responsible for?
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TNFalpha. Responsible for the cascade of events (fever, acidosis, hypotension, DIC, shock, death) that most importantly end in vascular permeability & possible death of the host.
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3 immunologic effects of LPS:
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1) Acts as an adjuvant
2) T-independent mitogen that produces polyclonal B-cell activation & a predominantly IgM response. 3) Activates complement via both classical & alternative pathways |
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LPS role in dz production:
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When septicemic Gm - infections occur, endotoxin is major cause of death. Definitely dose related, but even in low quantities, endotoxin is a potent stimulator of cytokine release
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Often produced within the body & exert their effects either locally or systemically. Some cause cell death either by digesting lipids in cytoplasmic membranes or by insertion into the membranes, forming protein pores. They are soluble proteins produced & excreted by both Gm - & Gm + bacteria. Strongly antigenic. Much more toxic. Most are heat labile. Can be converted to toxoids, neutralized by antibodies
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Exotoxins
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What are 3 groups of exotoxins based on mechanisms of action?
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1) Cytolytic toxins
2) Toxins with intracellular activity 3) Others (includes those w/ unknown mechanism) |
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A toxin of a pathogenic organism treated so as to destroy its toxicity but leave it capable of inducing the formation of antibodies on injection
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Toxoid
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A toxin responsible for gas gangrene and myonecrosis in infected tissues. The toxin also possesses hemolytic activity.
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Alpha toxin
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2 toxins that uncouple protein synthesis by NAD-dependent ADP-ribosylation of elongation factor 2?
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Cornybacterium diphtheriae toxin & Pseudomonas aeruginosa exotoxin A
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Anthrax toxin is a heterotrimeric protein consist of what 3 things?
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Protective antigen
Lethal factor Edema factor |
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Classically detected by their effects on RBC membranes (hemolysis)
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Hemolysins
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What is the role of hemolysin in disease?
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Cytolytic toxins may lyse cells or merely produce membrane effects that result in permeability changes
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Staphylocci, where the alpha hemolysin causes complete hemolysis (_____ hemolysis) and the beta hemolysin causes incomplete hemolysis (_____ hemolysis)
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beta; alpha
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Name and describe the 4 hemotoxins
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1) alpha: complete hemolysisl Mechanism of action is through hexamers forming transmembrane channels (pores)
2) beta: incomplete. Phospholipase C activity 3) Gamma: proteins A, B, & C are encoded & these pair as A&B and C&B. Complete hemolysis 4) Delta: Complete hemolysis. Has strong detergent-like activity. |
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Major components of plasma membrane of mammalian cells. Act on different substrates. Lyse erythrocytes. Some act on selected Eukaryotic cells.
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Phospholipases
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An endopeptidase that primarily interferes with the release of inhibitory neurotransmitter at nerve synapses. Tonic muscular contractions.
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Tetanus neurotoxin
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Some of the most potent toxins known. Ultimately block the release of acetylcholine from cholinergic endings resulting in flaccid paralysis. Flaccid paralysis is the main, lethal effect
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Clostridium botulinum neurotoxin
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Intracellular survival & spread are mediated in large part by production of what?
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Exotoxins
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Converts fibrinogen to fibrin. Clots
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Coagulase
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Hydrolyzes hyaluronic acid in connective tissue & may contribute to spread of the organism in the host.
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Hyaluronidase.
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Hydrolyzes lipids
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Lipase
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Hydrolyzes deoxyribonuclei acid (DNA)
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Nuclease
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Break the peptide bonds in collagen. Assist in destroying extracellular structures in pathogenesis of bacteria such as Clostridium
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Collagenase
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Catalyzes the hydrolysis of urea to ammonia & CO2. Helicobacter pylori uses this to adjust pH of stomach to aid in colonization
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Urease
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An important component of the hosts innate immune response against invading microorganisms. Family of enzymes with antimicrobial activity characterized by the ability to damage the cell wall of bacteria. Can be found in body secretions & tears
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Lysozyme
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"Blue pus" (Pyocyanin) is a characteristic of suppurative infections caused by what?
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Pseudomonas aeruginosa.
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What is pyocyanin?
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Blue pigment, impairs the normal function of human nasal cilia, disrupts the respiratory epithelium, & exerts a proinflammatory effect on phagocytes.
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A siderophore that is produced under low-iron conditions to sequester iron from the environment for growth of the pathogen
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Pyochelin
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What type of epithelium is characterized by the following?
1) Transient interaction 2) Some produce keratin-hydrolyzing enzymes 3) Usually crossed via breaks, burns 4) Moisture facilitates entry 5) Importance of skin best illustrated by its loss |
Keratinized Epithelium
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What are some defenses of keratinized epithelium?
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1) Low pH (fatty acids), drying
2) keratinocytes (most of epidermis)' maintain low pH; ingest/kill bacteria 3) Adapted flora, mainly G+ 4) Cell sloughing 5) Lysozyme protects pores, follicles |
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What type of epithelium is characterized by the following?
1) Single layer, multiple cell types, functions 2) Tight junctions connect cells, few bacteria can disrupt 3) Turnover of mucosal cells 4) Mucus composed of proteins, polysaccharides 5) Lubrication, entrapment |
Mucosal epithelium
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What are some defenses of mucosal epithelium?
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1) lung architecture: speed of particle
2) mucociliary ladder in lungs 3) cough, sneeze stimulated by histamine 4) uterus protected by cervix 5) Microflora - upper respiratory tract, lower genitourinary tract 6) GI microflora: great competitors, make antibacterial products 7) Low O2 (difficult for aerobes) 8) Detergent effect of bile salts 9) Macrophages/phagocytosis |
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Certain protein antigens are able to bind directly to the variable beta region of the T-cell & stimulate large #s of T-cells to release IL-2 & IL-4. A massive overstimulation of the immune system results and in many cases this is life-threatening. An example would be the Toxic Shock Syndrome Toxin (TSST1)
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Superantigen
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