Reading...
Play button
Play button
Use LEFT and RIGHT arrow keys to navigate between flashcards;
Use UP and DOWN arrow keys to flip the card;
H to show hint;
A reads text to speech;
319 Cards in this Set
- Front
- Back
|
What distinguishes a prokaryote from a eukaryote (3)?
|
1. Packaging of DNA - no nucleus, no histones
2. Cell wall composition - peptidoglycan 3. No complex, membrane-bound organelles for internal structures |
|
|
What are the contents of all bacterial cells?
|
1. Cell membrane
2. ribosomes 3. one or more chromosomes 4. majority have cell wall |
|
|
Flagella
|
- long, thin, helical filament
- allows for motility and chemotactical response - may contribute as virulence factors by promoting spread of infx and attachment |
|
|
What is the significance of flagellins (proteins that make up flagella)?
|
Can be used as serologic markers (H antigens)
|
|
|
a. Periplasmic flagella
b. ex |
a.
- Enclosed in a sheath (internal structures) - not antigenic - attached to and wound around long axis of cell b. spirochetes including treponemes and borrelia |
|
|
What are the 2 appendages for attachment and mating?
|
1. fimbriae
2. pilus |
|
|
What is a fimbriae
|
- thin, hair-like filaments
- straighter and shorter than flagella - over entire cell surface - on many gram (-); few gram (+) |
|
|
How is a fimbriae a virulence factor?
|
Mediates attachment (acts as receptors/adhesins) to host tissues and allows colonization
|
|
|
Wht is a pilus
|
Structure of gram (-) involved in transferring DNA (conjugation)
|
|
|
What are the 3 names for bacterial surface coating?
|
1. glycocalyx
2. capsule 3. K antigen |
|
|
1. What is the glycocalyx?
2. What is it composed of? 3. What is its serological designation? |
1. Slime layer and capsules
2. Polysaccharides/proteins or both secreted from gram (+/-) that adhere to cell wall 3. K antigen |
|
|
What is the function of the capsule (3)?
|
Increase virulence of pathogen by:
1. conferring resistance to phagocytosis 2. role in adherence and development of biofilms 3. help protect from antibodies |
|
|
What is the difference b/w gram (-) and gram (+) cell envelope?
|
Gram (+) has 2 layers - cell wall and cytoplasmic membrane
Gram (-) has 3 layers - cell wall, cytoplasmic membrane and outer membrane |
|
|
Characteristics of cell wall (6)
|
1. determine shape of bacterium
2. strong structural support 3. rigid due to peptidoglycan content 4. prevents lysis from pressure changes 5. target of antibiotics (cell wall disrupted --> lysis) 6. affected by lysozyme |
|
|
Peptidoglycan
|
linear polymers of NAG and NAM linked with beta-1,4 bond
|
|
|
Gram positive cell wall
|
Thick, homogeneous sheath of peptidoglycan. Contains tightly bound acidic polysacchaides
|
|
|
What is the significance of aicid polysaccharides in gram positive cell wall?
|
Virulence factors (techoic and lipoteichoic acids)
|
|
|
Gram negative wall
|
single, thin sheet of peptidoglycan surrounded by periplasmic space
|
|
|
1. What are examples of 3 non-typical cell walls?
2. How are they different? |
1. mycobacterium, nocardia and mycoplasmas
2. - mycobacterium and nocardia contain lipids (mycolic acids) along with peptidoglycan (use acid-fast stain) - mycoplasmas lack cell wall and antibiotics that target peptidoglycan are not effective |
|
|
How is gram (-) outer membrane different from the cell membrane?
|
Contains specialized polysaccharides and proteins
|
|
|
What do the two layers of gram (-) bacteria contain?
|
outer layer - lipopolysaccharide and porin
inner layer - phospholipid |
|
|
1. What is LPS?
2. What is it composed of? 3. What is its role in infxn? |
1. endotoxin found in all gram (-) bacteria
2. lipid A, core polysaccharide and O-specific polysaccharide 3. causes shock and fever (gram (-) shock or endotoxic shock) |
|
|
What is the importance of porin?
|
Form a channel that allows passage of small molecules (PCN)
|
|
|
How is the innermost layer anchored to peptidoglycan layer below?
|
Lipoproteins anchor phospholid layer to peptidoglycan layer below
|
|
|
Which bacteria can take up CV-I complex?
|
Both gram (+/-)
|
|
|
What happens when CV-I complex is used to stan gram (+)?
|
Complex trapped by dehydration and reduced porosity of thick cell wall when washed with ethanol.
|
|
|
1. Why does CV-I complex not stick to gram (-)?
2. What is applied? |
1. Thin peptidoglycan and outer membrane layer does not prevent extraction
2. safranin is added |
|
|
Staining of:
1. gram (+) 2. gram (-) |
1. purple
2. pink/red |
|
|
Characteristics of cytoplasmic membrane?
|
- made of lipid bilayer w/ imbedded proteins
- very thin - contains primarily phospholipids and proteins |
|
|
Functions of cytoplasmic membrane (3)?
|
1. active transport
2. energy transducing systems 3. biosynthesis of phospholipids, peptidoglycan (peptidases [PCN binding proteins] link polymers of NAG and NAM) and glycocalyx material |
|
|
What are the 2 sources of genetic material?
|
1. bacterial chromosomes
2. plasmids |
|
|
Characteristics of bacterial chromosome?
|
1. Single circular strand of DNA
2. aggregated in dense are of cell (nucleoid) |
|
|
1. What are plasmids?
2. What are some important functions? |
1. nonessential pieces of circular ds-DNA
2. Confer protective traits such as drug resistance (R-plasmids) or production of toxins and enzymes |
|
|
Ribosomes:
1. Action of ribosome? 2. Made from? 3. Significance in terms of drug therapy? |
1. Site of protein synthesis
2. ribosomal RNA and protein 3. targets for different classes of antibiotics (e.g. aminoglycosides, tetracyclines, macrolides) |
|
|
Why can transcription and translation occur simultaneously?
|
There is no physical separation by nuclear membrane
|
|
|
What are inclusions or granules?
|
Storage bodies; some serve as nutrient reserves and include polysaccharides, lipids or polyphospates
|
|
|
1. What are bacterial endospores?
2. What is the term for the other phase of the bacterial life cycle? 3. What induces sporulation? |
1. extremely resistant stage; dormant bodies
2. vegitative cell 3. environmental conditions; depletion of nutrients |
|
|
Medical significance of endospores (5 examples)
|
1. Bacillus anthracis (anthrax)
2. Clostridium botulinum (botulism) 3. Clostridium perfringens (gas gangrene) 4. Colstridium difficile (pseudomembranous colitis) 5. Clostridium tetani (tetanus) |
|
|
What are the 3 general shapes of bacteria?
|
1. coccus
2. bacillus 3. curved or spiral forms |
|
|
1. Describe coccus
2. types/examples of coccus (3) |
1. roughly spherical
2. - diplococci are pairs (Neisseria; G-) - streptococci are chains (Streptococcus; G+) - staphylococci are irregular clusters (Staphylococcus; G+) |
|
|
1. Describe bacillus
2. types/examples (3) |
1. rod-shaped; variations occur
2. - coccobacillus - short and plump (Haemophilus; G-) - fusiform - tapered ends (Fusobacterium; G-) - coryneform - club-shaped (Corynebacterium; G+) |
|
|
1. types/examples (4) of curved or spiral forms
|
- vibrio - gently curved (Vibrio; G-)
- spirochete - spiral form (Treponema; G-) - leptospira - tightly wound spiral (Leptospira; G-) - borrelia - very tightly wound spirals (Borrelia; G-) |
|
|
Define pleomorphism
|
When cells of single species vary to some extent in shape and size
|
|
|
Early vs. current methods for bacterial classifications?
|
Early - phenotypic traits of bacteria
current - combines phenotypic info w/ rRNA sequencing |
|
|
What are the 5 approaches to taxonomy?
|
1. phenotypic characteristics
2. serologic reactivity 3. bacteriophage typing 4. antibiotic sensitivity 5. genetic classification |
|
|
What are the 5 different phenotypic characteristics?
|
1. colony morphology
2. direct examination 3. growth characteristics 4. culture and biochemical characteristics 5. biochemical tests - inc. patterns of substrate utilization, metabolic product formation, sugar fermentation and unique chemical constituents |
|
|
What is colony morphology?
|
colony morphology - different bacterial colonies vary in size, shape, color, odor, texture
|
|
|
What is direct examination?
|
direct examination - microscopic morphology; staining reactions
|
|
|
What are growth characteristics?
|
growth characteristics - O2 requirements, temp of incubation, pH
|
|
|
What are culture and biochemical characteristics?
|
culture and biochemical characteristics - isolation on various culture media or cell lines
|
|
|
What do biochemical tests include?
|
biochemical tests - inc. patterns of substrate utilization, metabolic product formation, sugar fermentation and unique chemical constituents
|
|
|
How is serologic reactivity used to classify serotype strains of a particular species?
|
By testing for presence of specific cell wall (O), flagellar (H), capsular (K) antigens and/or other components which serve as antigens (e.g. Escherichia coli O157:H7)
|
|
|
How is bacteriophage typing used for classification?
|
Different strains of identical species susceptible to one or more different strains or types of species-specific bacterial viruses
|
|
|
What are the 2 components of genetic classification?
|
1. genus/species - G+C content, DNA/RNA homology, DNA/RNA sequencing
2. subspecies (for epidemiology) - nucleic acid probe, nucleotide digests, plasmid profiles |
|
|
What is a family?
ex. |
group of related genera
ex. Enterobacteriaceae |
|
|
What is a genus?
ex. |
group of related species
ex. Escherichia |
|
|
Define species
ex. |
A distinct organism with distinguishing features
or a group of bacteria resembling each other by having similar distinctive features ex. coli |
|
|
What is a type strain?
|
"Common joe" strain - permanent example of the species
|
|
|
Subspecies, strain, or type designate bacteria of the ??same/different?? species that have ??similar/differing?? characteristics
|
Same; differing
|
|
|
What are serotypes?
ex. |
Members of a species that stimulate distinct antibodies, because of distinct surface molecules
ex. O157:H7; Escherichia coli O157:H7 |
|
|
What are 2 examples of medically significant prokaryotic groups with unusual characteristics (obligate intracellular parasites)?
|
1. Rickettsias - agents for spotted fevers; alternate b/w mammalian host and blood-sucking arthropods
2. Chlamydias - agents for STDs, trachoma, and pneumonia |
|
|
What are chemoheterotrophs?
|
Derive nutrients from cells or tissues of a host; aka pathogens because they cause damage/death to tissue
|
|
|
What are the 4 types of chemoheterotrophs/describe them.
|
1. ectoparasites - live on the body
2. endoparasites - live in organs and tissues 3. intracellular parasites - live w/in cells 4. obligate parasites - unable to grow outside of living hosts |
|
|
What are the 3 environmental factors that influence microbes?
|
1. temperature adaptations
2. gas requirements 3. effects of pH |
|
|
What are the 3 classifications of bacteria based on temperature adaptations?
|
1. psychrophile
2. mesophile 3. thermophile |
|
|
1. What is the temperature range for psychrophiles?
2. What is the optimal temperature for growth? 3. ex of psychrophile and temp range? |
1. optimum temp. below 15C and capable of growth at 0C
2. grow slowly in cold, but optimally at 20C 3. Listeria monocytogenes (neonatal "early-onset disease") is capable of growth 1-45C |
|
|
Optimal growth temperature for mesophiles?
|
20-40C
|
|
|
Most human bacterial pathogens are?
|
mesophiles
|
|
|
Optimal growth temp for thermophiles?
|
>45C
|
|
|
1. What are the two atmospheric gases that have the most influence in microbial growth?
2. Which has the greater impact? |
1. O2 and CO2
2. O2 |
|
|
1. What happens as O2 is metabolized by bacteria?
2. What do most cells have to counteract the products? |
1. transformed into toxic products
2. superoxide dismutase and catalase - enzymes that scavenge and neutralize the chemicals |
|
|
Difference b/w streptococcus and staphylococcus (toxin neutralizing)
|
Streptococcus can't produce catalase
Staphylococcus is catalase + |
|
|
What is an aerobe?
|
Can use gaseous O2 in metabolism and possesses enzymes that process O2 toxins
|
|
|
What is an obligate aerobe?
|
Can't grow without O2
|
|
|
What is a facultative anaerobe?
|
Aerobe that does not require O2 for metabolism and is capable of growth in absence of O2
|
|
|
In a mixed infection w/ both facultative and aerotolerant anaerobes, which is a precursor for the success of the other?
|
Facultatives create an environment allowing aerotolerant to grow
|
|
|
What is a microaerophile?
|
Can't grow at normal [atmospheric] of O2 but requires a small amount for metabolism
|
|
|
What is an anaerobe?
|
Lacks metabolic enzyme systems for using O2 in respiration
|
|
|
1. What is a strict/obligate anaerobe?
2. Knowing this, what is a therapeutic method used for some anaerobic infections? |
1. lacks enzymes for processing toxic O2 and can't tolerate free O2 in immediate environment - will die
2. hyperbaric O2 |
|
|
What is an aerotolerant anaerobe?
|
Does not utilize O2, but can survive/grow to limited extent in it
|
|
|
1. What are capnophiles?
2. ex. of capnophile? |
1. grow best at higher [CO2]
2. Neisseria gonorrhoeae |
|
|
1. What is the optimal pH range for the majority of bacteria?
2. Ex of bacteria that can survive and lower pH and how? 3. Ex of bacterial species that are found in vaginal tract of health females? |
1. 6 - 8
2. Helicobacter pylori; by producing urease 3. Lactobacillus species that are acidogenic |
|
|
What are the 2 levels of microbial growth?
|
1. cell synthesizes new cell components and increases in size
2. number of cells in population increases |
|
|
What is the process by with replication occurs?
|
Binary fission
|
|
|
1. What is generation time?
2. By what factor does each new cycle increase population? |
1. time required for complete fission cycle; measure of growth rate of organism
2. factor of 2 |
|
|
1. What is the avg. generation time under optimal conditions?
2. What is the shortest time of generation? 3. ex of bacterial generation w/ times |
1. 30 - 60 mins
2. 10 - 12 mins 3. Mycobacterium leprae - time of 10-13 days; Salmonella enteriditis - time of 20-30 mins |
|
|
What is a population growth curve?
|
Depiction of population changes in bacterial culture
|
|
|
What are the 4 stages in normal growth curve?
|
1. lag phase - physiological adjustment period
2. exponential/log phase - maximal division rate 3. stationary phase - rate of cell inhibition or death = rate of multiplication rate 4. death phase - cell death at exponential rate |
|
|
What is the practical importance of curve?
|
implications in microbial control and infxn; growth patterns can account for stages of infxn
|
|
|
What are 2 measurements of growth?
|
1. turbidity assessment
2. Enumeration of bacteria - viable count, direct count, Coulter count |
|
|
1. What is the importance of microbial exoenzymes in disease?
2. What are the exoenzymes called? 3. Examples (3) |
1. some help avoid host defense or promote multiplication in tissues
2. virulence factors or toxins 3. - streptokinase: Streptococcus pyogenes - elastase and collagenase: Pseudomonas aeruginosa - lecithinase C: Clostridium perfringens |
|
|
Final electron acceptor in:
1. aerobic metabolism 2. anaerobic metabolism |
1. O2
2. other organic/inorganic compound |
|
|
What are the 4 methods of catabolism used by bacteria?
|
1. glycolysis
2. aerobic respiration 3. anaerobic respiration 4. fermentation |
|
|
What is the most frequently need nutrient and what pathway is used to obtain this nutrient?
|
Glucose; glycolysis
|
|
|
1. What is aerobic respiration?
2. For what 3 processes is O2 a terminal electron acceptor |
1. glucose oxidized to CO2 and H2O
2. glycolysis, Krebs cycle, respiratory chain |
|
|
What are 2 biochemical tests related to aerobic respiration?
|
1. oxidase
2. catalase |
|
|
What is the biochemical test oxidase?
|
Based on production of oxidase enzyme -> catalyzes oxidation of reduced cytochrome by molecular O2.
Oxidase test reagents are artifical electron acceptors e.g. Kovacs' reagent |
|
|
What is the biochemical test catalase?
|
Byproduct of aerobic resp. is H2O2 -> toxic at high concentrations
Catalase uses H2O2 as oxidant and reductant to convert into water and ground-state O2 |
|
|
Describe anaerobic resp.
1. How is glucose oxidized and what are the terminal e- acceptors? 2. How is it similar to aerobic cytochrome system? |
1. glucose oxidized via glycolysis, Krebs cycle and anaerobic resp. w/ NO3-, SO4 -2, CO3 -2 as terminal electron acceptors
2. utilizes O2-containing ions rather than free O2 as final e- acceptor |
|
|
1. What is a large group of facultative anaerobic respirers?
|
1. Nitrate reducers e.g. Escherichia coli & Staphylococcus aureus
|
|
|
1. What does the nitrate reduction test determine?
2. What antibiotic are nitroreductase producers sussceptible to? |
1. the ability of organisms to reduce nitrate to nitrites or free N2 gas
2. metronidazole |
|
|
What types of microbes use this pathway to generate energy?
|
obligate anaerobes, aerotolerant anaerobes, facultative anaerobes
|
|
|
What occurs during fermentation?
|
Glucose oxidized via glycolysis and pyruvate is oxidized w/ organic compound serving as terminal e- acceptor
|
|
|
What types of microbes can be fermentative?
|
Obligate, aerotolerant and facultative anaerobes
|
|
|
Fermentative byproducts can be produced by various heteropropic bacteria - lactic acid, ethanol, acetid acid, butyric acid, butanol, propionic acid or acetone
What is the clinical significance of these byproducts? |
Useful for biochemical identification
|
|
|
How do anaerobic bacteria degrade exogenous proteins?
|
Produce proteases that hydrolyze proteins to peptides. Peptidases break down peptides to a.a.'s which are catabolized.
|
|
|
What occurs during breakdown of proteins that is commonly associated w/ anaerobic bacterial infxn?
|
Foul odors
|
|
|
Genomic sizes of:
1. smallest virus 2. Escherichia coli 3. human cell |
1. 4/5 genes
2. 4,288 genes 3. 20,000 - 25,000 genes |
|
|
How does fluoroquinolone inhibit bacterial DNA replication?
|
Targets bacterial gyrase and topoisomerase
|
|
|
1. What is transcription?
2. What is translation? 3. What is the gene-protein connection? |
1. DNA -> RNA
2. RNA -> protein 3. triplet code and relationship of proteins |
|
|
1. Examples of antibiotics that affect transcription?
2. Examples of antibiotics that affect translation? |
1. rifampin (Mycobacterium tuberculosis)
2. erythromycin, streptomycin |
|
|
What is bacterial recombination?
|
Process in which progeny bacteria possess combination of genes which are different (hybrid) than those present in parental bacteria
|
|
|
What are the 3 mechanisms of recombination?
|
1. conjugation
2. transformation 3. transduction |
|
|
What is conjugation (bacteria sex)
|
Transfer of DNA by direct contact b/w cells through cytoplasmic bridge
|
|
|
How is sexual differentiation determined?
|
Presence or absence of sex factor "F" which is an extrachromosomal, autonomously replicating DNA molecule
|
|
|
1. What does the F factor promote?
2. What does the F factor contain? |
1. promotes conjugation and gene exchange
2. information for synthesis of sex-specific pili |
|
|
What allows recognition of recipient cells and close interaction by initiating wall-wall contact?
|
Sex pili
|
|
|
How is a male bacterium defined? Female?
|
F+; F-
|
|
|
What are some variations in conjugation F factor?
|
F factor transfer; Hfr (high frequency recombinant transfer)
|
|
|
1. What are R factors?
2. What is the magnitude of information that is transferred? |
1. Carry genes for resisting antibiotics
2. can confer multiple resistance to antibiotics to 1 strain |
|
|
What else can R factors carry?
|
Resistance to heavy metals or for synthesizing virulence factors
|
|
|
What is transformation?
|
Naked DNA derived from one cell/virus is taken up by another cell and recombines with genome
|
|
|
What is competency?
|
Ability to incorporate DNA in the manner of transformation
|
|
|
When does transformation occur?
|
A short period during log phase growth
|
|
|
What bacteria was transformation observed in?
|
Streptococcus pneumoniae in R vs. S strains
|
|
|
1. What is transduction?
2. What do bacteriophages replicate as? 3. What can occur with host DNA during this process? |
1. DNA of one cell introduced into another by virus infection.
2. obligate intracellular parasites 3. cellular DNA can accidentally be incorporated into new infectious viruses |
|
|
What are the 2 variations of transduction?
|
generalized and specialized tranduction
|
|
|
What is generalized transduction?
|
- viral infxn of donor bacterium causes denaturation and fragmentation of bacterial DNA
- replication & maturation may result in incorporation of any portion of bacterial genome into viral capsid - viral capsid containing bacterial DNA can infect and introduce DNA into recipient bacterium - can be incorporated into nucleoid and expressed |
|
|
What is specialized tranduction?
|
- viral infxn of donor bacterium includes insertion of viral genome into specific locations in bacterial genome
- excision of viral DNA may result in accidental incorporation of bacterial DNA - hybrid DNA may be incorporated into viral capsid (bacterial DNA limited to location of insertion) - viral capsid with hybrid DNA can infect and introduce DNA into recipient - may be incorporated into nucleoid and expressed |
|
|
Examples of virulence strains that produce toxins coded for by bacteriophage genes from transduction
|
Corynebacterium diphtheriae, Clostridium spp, Streptococcus pyogenes
|
|
|
Which genetic elements cause genotypic and phenotypic changes?
|
1. plasmids
2. transposons 3. insertion sequences 4. gene cloning |
|
|
What are plasmids?
|
- extrachromosomal genetic elements capable of autonomous replication
|
|
|
Besides genes for own replication, what other genes do plasmids carry (other phenotypic characteristics)?
|
- antibiotic resistance
- biodegradative enzymes - enterotoxin and hemolysin production |
|
|
What is the primary cause of increasing incidence of antibiotic resistant pathogens?
|
spread of antibiotic resistant plasmids
|
|
|
How can the genome of plasmids be classified?
|
DS, circular molecules
|
|
|
What are transposons?
|
Segments of DS DNA that can move from place to place w/in genome or b/w genomes or plasmids or phage genomes
|
|
|
How is a mutation caused with transposons?
|
Insertion into a new site in DNA
|
|
|
How are transposons similar to plasmids?
|
Can carry genes for wide variety of phenotypic characteristics
|
|
|
How are transposons different from plasmids?
|
- Do no carry genes controlling own replication
- possess insertion sequence elements responsible for transposability |
|
|
What are insertion sequences?
|
- small segment of DS DNA code for side specific recombination
- fnxn/activity altered when integrated into a gene |
|
|
What is gene cloning?
|
- isolation of specific genes in hybrid replicons
- cloning vectors used to introduce recomb DNA into suitable hosts - products used in diagnosis and therapy of disease |
|
|
What are the 3 goals for diagnosis?
|
1. gather info for selection of correct therapeutic procedure
2. ID of pathogen and establish potential for spread 3. seek common source to prevent widespread transmission by determining epidemiology |
|
|
What are 3 general methods to survey microbial diseases?
|
1. phenotypic methods
2. genotypic methods 3. immunologic methods |
|
|
What are 3 specific types of phenotypic methods?
|
1. microscopic morphology
2. macroscopic morphology 3. physiological/biochemical characteristics |
|
|
What are the 2 possible ways to collect specimen?
|
1. direct specimen collection
2. indirect collection |
|
|
What is direct specimen collection?
|
collected from normally sterile tissues
|
|
|
Ex of direct specimen collection?
|
CSF, needle aspiration of abscess to surgical biopsy
|
|
|
What are indirect specimen samples?
|
specimen for inflammatory exudate
|
|
|
Examples of indirect samples?
|
sputum and urine
|
|
|
Describe site of origin of indirect specimen and the places through which they pass
|
- Site of origin is usually sterile
- Pass through sites known to be colonized w/ normal flora * assessment requires knowledge of potential contaminating flora |
|
|
How are samples from normal flora sites differentiated?
|
- Tests selective for organisms known to cause infxn
- not normally found at infected site |
|
|
- Examples of places where there is normal flora?
- Example of microbe that can be found in normal flora? |
- pharynx or large intestine
- Campylobacter jejuni |
|
|
What are the methods of specimen collection?
|
1. sterile swab most common
2. best specimen is 5-10 mL of infected fluid/tissue 3. should be transported ASAP 4. transport media stabilize condition and prevent drying |
|
|
What are the 2 general types of phenotypic methods?
|
1. direct examination
2. cultivation of specimen |
|
|
When is direct examination used?
|
For morphology and staining reactions
|
|
|
What are 3 examples of direct method?
|
1. light microscopy
2. dark-field microscopy 3. fluorescence microscopy |
|
|
When is light microscopy used?
|
gram stain and acid fast stain
|
|
|
- What is dark field microscopy?
- What type of bacteria used for? - ex of bacteria used for? |
- condenser focuses light diagonally on specimen
- thin bacteria - Treponema pallidum |
|
|
What is fluorescence microscopy?
|
Similar to dark-field except light source is UV and bacteria stained w/ fluorescent dyes
|
|
|
- What is cultivation of specimen?
- What characteristics are determined from cultivation? |
- agar-containing plate streaking for isolation and colonial morphology
- size, shape, color, texture, odor, degree adherence to medium |
|
|
What are 3 types of isolation media?
|
1. nutrient media
2. selective media 3. indicator media |
|
|
What is nutrient media?
|
include components for growth to permit isolation and propagation
|
|
|
What is selective media?
|
contains chemicals or antimicrobics that inhibit growth of unwanted bacteria but allows growth of specific antigens
|
|
|
What are selective media used?
|
When sample taken from sites with normal flora
|
|
|
What is indicator media?
|
contain materials that demonstrate biochemical characteristics
|
|
|
Examples of when indicator media used?
|
- pH indicators for fermentation
- whole red blood cells for hemolysin production - beta-hemolytic Streptococcus pyogenes |
|
|
What are 3 examples of biochemical testing?
|
- carb fermentation (acid and/or gas)
- enzyme actions such as catalase, oxidase and coagulase - by-products of metabolism |
|
|
What are ex. of misc tests?
|
1. phage typing
2. animal inoculation 3. antimicrobial sensitivity |
|
|
What is phage typing?
|
Virus susceptibility to determine epidemiology
|
|
|
What is minimum inhibitory concentration (MIC)?
|
Lowest concentration of antimicrobial agent that can inhibit growth of test bacterium
|
|
|
What are 3 methods for determining drug susceptibility of microorganisms?
|
1. Kirby-Bauer method (disk agar diffusion DAD)
2. Etest 3. micro-broth dilution |
|
|
Describe Kirby-Bauer method
|
- bacterial applied to agar plate
- paper disks w/ antimicrobial agents placed on agar surface - zone (inhibition) size examined and classified as : susceptible, indeterminate or resistant |
|
|
Describe Etest method
|
- paper strips w/ gradient of antimicrob. agent placed on innocu. agar surface
- elliptical zone of inhibiton form as antimicrobial inhibits growth - MIC read where groth and strip intersect |
|
|
Describe micro-broth dilution
|
- agent suspended in medium to given concentration and added in 2-fold dilution to microtiter plate w/ broth medium and agar w/ innocu.
- MIC determined as concentration visibily inhibiting growth |
|
|
What are 3 types of genotype methods?
|
1. DNA analysis w/ genetic probes
2. nucleic acid sequencing and rRNA analysis 3. PCR |
|
|
How is hybridization used for DNA analysis?
|
Can ID bacterial species by analyzing segments of its DNA
|
|
|
What are probes?
|
Small fragments of single-stranded DNA or RNA - complementary to specific sequences of DNA form particular microbe
|
|
|
- What genotypic method can be fine tuned to ID at species level?
- Ex of this? |
- nucleic acid sequencing and rRNA analysis
- restriction fragment length polymorphisms (RFLP) |
|
|
Define immunogenic methods
|
Characteristics of Ab's can reveal history of pt's contact w/ microorganisms or other antigens
|
|
|
What are 5 general immunologic methods?
|
1. agglutination testing
2. percipitation testing 3. fluorescent ab and immunofluorescence testing 4. immunoassays 5. in vivo tests |
|
|
What are 3 types of agglutination tests?
|
1. rapid plasma reagin test for syphilis
2. weil-felix test for rickettsial disease 3. latex agglutination test |
|
|
What is latex agglutination test?
|
- Either antigen or IgG antibody is absorbed to surface of latex polystyrene beads
- kits available for some Lancefield streptococci groups: Streptococcus pneumoniae, Neisseria gonorrhoeae, N. meningitidis, Staphylococcus aureus, Candida |
|
|
What is a precipitation test?
|
soluble antigen precipitated by an antibody
- ex. VDRL for syphilis |
|
|
What are types of fluorescent antibody and immunofluorescence testing?
|
1. direct
2. indirect |
|
|
Ex of immunoassay?
|
ELISA
|
|
|
Ex of in vivo tests?
|
Tuberculin test - uses skin reactions to PPD
|
|
|
What are the 4 ways to control microorganisms?
|
1. sterilization
2. disinfection 3. antisepsis 4. decontamination |
|
|
Define sterilization?
|
Destruction of all microbial life
|
|
|
Define disinfection?
|
Destroys most microbial life, reducing contamination of inanimate surfaces
|
|
|
Define antisepsis?
|
Destroys most microbial life, reducing contamination on a living surface
|
|
|
Define decontamination?
|
Mechanical removal of most microbes from an animate or inanimate surface
|
|
|
What microbial forms have the highest resistance?
|
prions, endospores
|
|
|
What microbial forms have moderate resistance?
|
Protozoan cysts, sexual fungal spores, naked viruses, Mycobacterium
|
|
|
What microbial forms have the least resistance?
|
Most bacterial vegetative cells, ordinary fungal spores, enveloped viruses, yeasts, and protozoan trophozoites
|
|
|
Sepsis
|
Growth of microorganisms in blood and other tissue
|
|
|
Asepsis
|
Any practice that prevents entry of infectious agents into sterile tissues
|
|
|
Antiseptics
|
applied directly to exposed body surfaces to destroy or inhibit vegetative pathogens
|
|
|
bactericide
|
chemical that destroys bacteria (not endospores)
|
|
|
fungicide
|
chemical that cal kill fungal spores, hyphae, and yeasts
|
|
|
virucide
|
chemical that inactivates viruses
|
|
|
microbicide
|
chemical agents that kill microorganisms
|
|
|
bacteristatic
|
prevent growth of bacteria
|
|
|
microbistatic
|
materials used to control microorganisms in body
|
|
|
What are the 4 modes of action of antimicrobial agents?
|
1. effects on cell wall
2. effects on cell membrane 3. affect protein and nucleic acid synthesis 4. alter protein function - denature |
|
|
How do antimicrobial agents affect cell walls?
|
Block synthesis, digest, break down its surface
ex. detergents and alcohol *** esp. gram - |
|
|
What are the two ways that antimicrobials can affect nucleic acid synthesis?
|
1. ribosome function - bind and stop translation
2. DNA and RNA function - bind irreversibly to DNA preventing transcription and translation (mutagenic agents) |
|
|
What is the goal of antimicrobial chemotherapy?
|
Administer a drug to an infected person which destroys the infective agent w/o harming host cells
|
|
|
What are the origins of antimicrobial drugs?
|
Bacteria
eg. Streptomyces, Bacillus, mold, Penicillium, Cephalosporium |
|
|
What are the 2 ways that microbes acquire drug resistance?
|
1. spontaneous mutations in critical chromosomes
2. new genes or sets of genes are acquired through transfer from another species |
|
|
What are 4 specific mechanisms of drug resistance?
|
1. drug inactivation mechanisms
2. decreased drug perm. or increased drug elim. (pumps) 3. change of drug receptors 4. change in metabolic patterns |
|
|
Describe drug inactivation mechanism
|
beta-lactamases inactive PCNs and cephalosporins (staph aureus and PPNG)
|
|
|
Describe change of drug receptors
|
Erythromycin alteration on 50S ribosomal binding site
PCN - alteration in binding proteins in cell wall |
|
|
Describe changes in metabolic patterns
|
Development of alternative pathways or enzymes eg. folic acid synthesis
|
|
|
Natural selection and drug resistance, in association w/ inappropriate/overuse of antibiotics
|
- Some members of population of microbes are drug resistant from mutation or genetic transfer
- when exposed to drug, survival of fittest and propagation |
|
|
What are 4 new approaches to antimicrobial therapy?
|
1. iron-scavenging capabilities
2. riboswitches - inhibitors of translation 3. probiotics and prebiotics - growth of good bacteria 4. lantibiotics - antibiotics produced by bacteria |
|
|
What is an allergic response to drugs?
|
Drug acts on antigen and stimulates allergic response including:
skin rash, resp inflammation, and anaphylaxis |
|
|
What is a biota?
|
- normal colonists or residents of healthy body surface
- harmless or beneficial - small # can be pathogenic - broad spectrum antimicrobials can destroy some beneficial specimen |
|
|
What is a superinfection?
|
When beneficial species destroyed, microbes kept in small number can overgrow -> cause disease
|
|
|
Give 2 examples of superinfection
|
1. cephalosporine used for UTI, destroys lactobacilli in vagina -> Candida albicans proliferate and case yeast infx or nL flora can cause bacterial vaginosis
2. oral therapy w/ tetracyclines, lindamycin and PCNs/cephalosporins a/w antibiotic-associated colitis - Clostridium difficile |
|
|
What is "disease"?
|
pathologic state that results in damage or disruption of organs or tissues
|
|
|
What is "infectious disease"?
|
Disruption of tissue or organ caused by microbes and their products
|
|
|
What are variables that cause biota to fluctuate?
|
1. general health
2. age 3. variations in diet 4. diet 5. hygiene 6. hormones 7. drug therapy |
|
|
What is the Human Microbiome Project?
|
Metagenomics being used to identify the microbial profile inside/on humans
|
|
|
What do most areas of the body in contact with the outside environment harbor?
|
Biota
|
|
|
How can bacterial biota benefit human host?
ex? |
By preventing overgrowth of harmful microbes
ex. lactobacilli keeps pH in vagina acidic by glycogen ferm. AND prevents overgrowth of variety of normal flora bacteria and Candidia albicans |
|
|
What is microbial antagonism?
|
Bacterial biota that prevent overgrowth of harmful microorganisms
|
|
|
In what situation would normal biota be harmful to the host and lead to infection?
|
Immunosupression such as AIDS
|
|
|
What is endogenous infxn?
|
Infection that occurs when normal biota introduced to sterile site
|
|
|
What are the various ways that newborns are exposed to biota, to start new colonization?
|
1st - breaking of fetal membranes (vaginal microbes enter womb)
2nd - passage through birth canal 3rd - large intestine microbiota from milk -- bottle fed - coliforms, lactobacilli, enteric streptococci, staphylococci -- breast fed - Bifidobacterium |
|
|
What specific regions of human body have biota?
|
human skin
GI -- mouth, large intestine, resp tract, GU tract |
|
|
What is a pathogen?
|
Microbe whose relationship w/ its host is parasitic and results in infection and disease
|
|
|
What does the type and severity of the infection by pathogen depend on?
|
Pathogenicity of organism
Condition of host |
|
|
Pathogenicity
|
Organism's potential to cause infxn or disease
|
|
|
What is a true pathogen?
|
Capable of causing disease in healthy individuals w/ normal immune function
|
|
|
What is an opportunistic pathogen?
|
Cause disease when the host's defenses are compromised or when they become established in a part of the body that is not natural to them
( burn pts - Pseudomonas) |
|
|
What is virulence?
|
Degree of pathogenicity, determined by its ability to establish itself in host and cause damage
|
|
|
What are virulence factors?
|
Any characteristics or structure of the microbe that contributes to its virulence
|
|
|
What are pathogenicity islands?
|
Large inserts of DNA that include virulence genes not found in nonpathogenic members of the genera
|
|
|
What is quorum sensing?
|
Population density determines regulation of virulence genes, inc. pathogenicity islands
|
|
|
What are the 3 steps for bacteria to become established?
|
1. portal of entry (exogenous/endogenous)
2. attaching to host 3. Surviving host defenses (escaping phagocytosis) |
|
|
How do microbes enter through skin?
|
Nicks, abrasions, and punctures
intact skin is very tough to enter through |
|
|
How do microbes enter through GI tract?
|
Pathogens contained in food, drink and other ingested substances
can be adapted to survival in digestive enzymes and pH changes |
|
|
What portal of entry allows for the entry of the greatest # of pathogens?
|
Respiratory portal
|
|
|
What portal of entry allows for entrance through unbroken surfaces?
|
GU portal
|
|
|
What pathogens infect during pregnancy?
|
T toxoplasmosis
O others such as hep R rubella C cytomegalovirus H herpes simplex virus |
|
|
What is ID (infectious dose)?
|
The amount of microbe necessary for infection to proceed
|
|
|
Microorganisms w/ smaller IDs have ??greater/lesser?? virulence
|
Greater
|
|
|
How is the virulence of a bacteria increased in regards to cell surface?
|
Attachment mechanisms that allows colonization of the host's surface
|
|
|
What is required for adhesion?
|
Bacterial adhesin and host receptor
|
|
|
What are examples of adhesins?
|
1. fimbriae - many bacteria can express several types (adapt to diff. environments)
2. portions of glycocalyx 3. lipoteichoic acids 4. outer membrane proteins |
|
|
What is a biofilm?
|
Structured community of bacterial cells enclosed in self-produced polymeric matrix and adherent to inert or living surface
|
|
|
What are the essential components of a biofilm?
|
1. bacteria
2. glycocalyx 3. surface |
|
|
What is an ultrastructure?
|
Composed of single species or mixed species
|
|
|
How do ultrastructures most commonly occur?
|
As a group of microcolonies
|
|
|
How are biofilms assembled?
|
- Planktonic bacteria explore env.
- decision to settle causes upregulation of genes involved in matrix prod - control is quorum sensing |
|
|
What is quorum sensing w/ biofilms?
|
cell-cell comm, via signal genes
ex. pathogenicity islands, plasmid transfer and 2ndary metabolisms, inc. glycocalyx prod |
|
|
Advantages of biofilm for bacteria?
|
- Structure acts as anchor
- traps nutrients - helps protect from biocides, antibiotics and antibiodies |
|
|
What are human infxns involving biofilms?
|
native valve endocarditis
central venous catheter urinary catheter intrauterine devices contact lenses |
|
|
How is bacterial chemotaxis important?
|
Capacity to move towards host surface (w/ flagella) is highly advantageous
**invasion by typhoid fever requires flagella, motility and chemotaxis |
|
|
What are 3 methods of surviving host defense?
|
1. leukocidins
2. glycocalyx 3. survival once ingested |
|
|
What are leukocidins?
|
membrane active exotoxins that kill certain white blood cells
|
|
|
How is the glycocalyx helpful in survival?
|
Makes it difficult for phagocyte to engulf microbe
|
|
|
What are examples of extracellular enzyme virulence factors that contribute to tissue damage?
|
1. collagenase
2. hyaluronidase 3. coagulase 4. kinase 5. urease |
|
|
What is collagenase?
|
Spreading factor that breaks down connective tissue of muscle
|
|
|
What is hyaluronidase?
|
spreading factor that affects the ability of the pathogen to penetrate the tissues of the host by hydrolyzing hyaluronic acid
|
|
|
What is coagulase?
|
- Causes coagulation of fibrinogen
- fibrin coats the cell walls of bacteria, protecting them against phagocytes - involved in walling off process |
|
|
What are kinases?
|
- Breaks down fibrin
- dissolves clots formed by body to isolate infxn |
|
|
What is urease?
|
splits urea to form ammonium hydroxide, which raises pH of urine and facilitates formation of struvite calculi
|
|
|
What are endotoxins?
|
LPS in gram - bacteria
|
|
|
What are characteristics of endotoxins?
|
1. active portion is Lipid A
2. induce fever 3. initiate complement cascade 4. activate B lymphocytes 5. stimulate production of tumor necrosis factor, IL-1, and prostaglandins 6. effects of exposure to LPS include fever, hypotension, shock and death |
|
|
What other components of cell wall stimulate endotoxin like pyrogenic acute phase responses?
|
teichoic and lipoteichoic acids
|
|
|
How are exotoxins different from endotoxins?
|
- site of action more localized than endotoxin
|
|
|
List 3 types of exotoxins
|
1. A-b exotoxins
2. membrane-active exotoxin 3. super-antigens |
|
|
What are A-B exotoxins?
|
- 2 general domains
- A portion determines mech. of action - B subunit is a/w binding specificity to host cell |
|
|
Examples of A-B exotoxins?
|
- neurotoxins like tetanus; botulinum toxins
- cytotoxin such as diphtheria toxin inhibits protein synth - enterotoxin such as cholera toxin and enterotoxins of e. coli cause diarrhea and/or vomiting |
|
|
What is the action of cholera toxin?
|
1. b unit binds to host
2. a unit increases adenylate cyclase activity 3. inc. [cAMP] results in loss of ions and water 4. results in diarrhea |
|
|
What are membrane-active exotoxins?
|
Act directly on host cell's surface to lyse and kill
|
|
|
Ex. of membrane-active exotoxins?
|
- Leukocidins
- lecithinase - hemolysins |
|
|
What are leukocidins?
|
Damage membranes of neutrophils and macrophages
|
|
|
What is lecithinase?
|
destroys plama membrane, esp. around RBCs (phospholipase)
e.g. the alpha toxin of Clostridium perfringens |
|
|
What are hemolysins?
|
destroy RBCs and other tissue cells by producing pores in membrane
|
|
|
What is a super-antigen?
|
- Bacterial proteins that bind to MHC class II on antigen-presenting cells and T cells
- results in the release of high levels of cytokines - ex. staphylococcus aureus mediated TSST-1 - ex. streptococcus pyrogenes pyrogenic exotoxin A (SPE type A) |
|
|
WHat are the different patterns of infxn?
|
- localized infxn
- systemic infxn - focal infxn - mixed infxn - primary and secondary infxn - acute and chronic infxns |
|
|
What is a sign?
|
any objective evidence of disease as noted by observer
|
|
|
What is a symptom?
|
subjective feelings that are verbalized by the patient
|
|
|
What is a syndrome?
|
combination of sign and symptoms
|
|
|
Signs and symptoms of inflammation?
|
1. edema
2. granulomas and abscesses 3. lymphadenitis 4. rash 5. lesion |
|
|
Signs of infxn in blood?
|
1. leukocytosis
2. leukopenia 3. septicemia 4. bacteremia 5. viremia |
|
|
Asymptomatic?
|
infxns that go unnoticed; subclinical or inapparent
|
|
|
Portals of exit?
|
1. resp and salivary portals
2. skin scales 3. fecal exit 4. UG tract 5. removal of blood or bleeding |
|
|
What are two types of persistence of microbes?
|
1. chronic infxn and latency
2. sequelae |
|
|
What are some chronic infxns?
|
herpes simplex
herpes zoster hep B AIDS Epstein-Barr |
|
|
What are sequelae?
|
long term or permanent damage to tissues or organs
|
|
|
What are reservoirs?
|
Places where pathogens persist
|
|
|
Reservoir vs. source
|
- Reservoir is primary habitat in natural world from which pathogens originate
- source is the ind. or object from which infxn is actually acquired |
|
|
What are types of living reservoirs?
|
1. carriers
2. animals |
|
|
What are carriers?
|
individual who inconspicuously shelters a pathogen and spreads it to others w/o any notice
|
|
|
What are types of carriers?
|
1. asymptomatic carrier
2. incubation carrier 3. convalescent carrier 4. chronic carrier 5. passive carrier |
|
|
What are biological vectors?
|
Actively participates in a pathogen's life cycle
|
|
|
What are mechanical vectors?
|
Transport infxous agent w/o being infected
|
|
|
What are zoonosis?
|
infxn indigenous to animals but naturally transmissible to humans
|
|
|
What are nonliving reservoirs?
|
human hosts in reg. contact w/ environmental sources (soil, water)
|
|
|
What are communicable diseases?
|
- when an infected host can transmit the infectious agent to another host and establish infxn in that host
- transmission can be direct/indirect - highly communicable |
|
|
What is a noncommunicable disease?
|
Does not arise through transmission of infectious agent from host to host
- acquired through some other, special circumstance |
|
|
What are examples of noncommunicable diseases?
|
1. compromised person invaded by his own microbiota
2. ind. has accidental contact w/ microbe in nonliving reservoir |
|
|
What are the patterns of transmission in comm. diseases?
|
1. contact transmission - direct (kissing, touching), droplets, vertical (mother to fetus), vector
2. indirect transmission |
|
|
What are routes of indirect transmission of comm. ds.?
|
through vehicle - contaminated materials; food, water, bio products, fomites; air; droplet nuclei; aerosols
|
|
|
What is a vehicle?
|
any inanimate material commonly used by humans that can transmit infectious agents
|
|
|
What are nosocomial infections?
|
Hospital as source of ds; 2-4 mill cases a year; importance of medical asepsis
|
|
|
Koch's postulates to determine etiology
|
1. identify microbe by evidence in pt
2. isolate and cultivate microbes 3. inoculate suitable test subject 4. reisolate agent in test subject |
|
|
What is epidemiology?
|
Study of the frequency and distribution of ds and other health-related factors in defined human populations
|
|
|
prevalence?
|
tot. number of existing cases w/ respect to entire pop.
|
|
|
incidence
|
# of new cases over certain time period
|
|
|
mortality rate
|
tot. num of deaths in pop. due to certain ds
|
|
|
morbidity rate
|
num of person afflicted w/ infectious disease
|
|
|
endemic
|
restricted to a locality or region
|
|
|
sporadic
|
occurring occasionally or scattered
|
|
|
epidemic
|
affecting a large number of people w/in a population
|
|
|
pandemic
|
occurring over a large geographical area
|
