Bacterial Pathogenesis C103 Flashcards

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psychrophile

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grows optimally at cold temperatures

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mesophile

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grows optimally at medium temperatures

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koch's postulates

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1. bacteria should be found in all diseased animals, but not healthy animals
2. bacteria should be grown and isolated in pure culture
3. bacteria from culture should cause disease in a healthy animal
4. same bacteria should be re-isolated from diseased animal

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thermophile

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grows optimally at high termperatures

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hyperthemophile

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grows optimally at really high temperatures

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nonhalophile

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cannot tolerate high osmolarity

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halotolerant

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can tolerant high salt conditions

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halophile

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grows optimally at high salt concentrations

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extreme halophile

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grows optimally at really high salt concentrations

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obligate aerobes

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require oxygen for growth

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facultative aerobes

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do not require oxygen for growth but grow better with it

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microaerophillic

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likes a little bit of oxygen and requires reduced oxygen conditions

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obligate anaerobes

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little to no tolerance for oxygen

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aerotolerant anaerobes

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do not use oxygen for respiration and do not require it for growth

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complex broth

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made from extracts of yeast and tissues (cell extracts); rich in nutrients, can grow many kinds of bacteria

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minimal media

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specific and defined nutrients, nutrient poor compared to complex broth, only works for some bacterial species and not others

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fastidious organisms

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require special addition to media such as blood or another component

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prototroph

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bacterial strain with no unusual nutritional requirements

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auxotroph

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Strain that carries a mutation that causes a nutritional requirement

Ex. e. coli mutant requiring certain amino acids (leucine - ) would need leucine for growth; Can be less virulent than parental, prototrophic strain

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formula for ideal exponential growth in culture

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N = N(0)2^(n)

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generation time

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t/n

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lag phase

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adjustment to new culture conditions

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log phase

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period of exponential growth

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stationary phase

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phase where cell number is relatively constant over time

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death phase

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bacteria run out of nutrients in culture and can't survive

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acidophiles

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grow optimally under acidic conditions

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akaliophiles

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grow optimally under basic conditions

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acid tolerant

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tolerates acidic conditions

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complement

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group of proteins in blood that bind to pathogens and promote inflammation

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pathogen

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a microoganism capable of producing pathology (disease) in a percentage of normal (non immune individuals)

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oppotunistic pathogen

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a microorganism that does not cause disease in a healthy host but only in individuals whose normal defense mechanisms have been compromised

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nosocomial infections

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secondary infections that are a result of treatment in a hospital

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virulence

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quantitative measure of pathogenesis

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LD 50

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lethal dose 50; the number of microorganisms required to kill 50% of the test animals

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ID 50

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infectious dose 50 is the number of organisms (or amount of a toxin) required to produce an infection in 50% of the test animals

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stages in pathogenesis

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1. encounter
2. entry
3. colonization
4. multiplication
5. invasion
6. evasion of host immunity
7. transmission

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virulence factor

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components of the pathogen responsible for its ability to cause an infection

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obligate pathogen

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cannot be found anywhere but in association with its host

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facultative pathogen

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one that can grow/survive in environment or in its host

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stealth strategy

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pathogens try to avoid being recognized (capsules)

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offensive strategies

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pathogens try to kill immune cells or interfere with cellular communication

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infiltrate

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pathogens live inside immune cells

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effector molecules of pathogenesis

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proteins that specifically interact with the host

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coccus

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round shaped

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rod

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rod shaped

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spirillum

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spiral shaped

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gram positive

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stains purple in gram staining

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gram negative

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stains red

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molecular phylogenetic classification

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use differences in sequences of genes in bacteria to see evolutionary relationships between species of bacteria (ex. 16s rRNA sequences) and construct a phylogentic tree based on those relationships

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classification of bacteria

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done by cell shape, gram positive vs. gram negative, molecular phylogenetic classification, and whether it is spore forming or not

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cytoplasmic membrane

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encloses the cytoplasm; composed of lipids and alphanoids; represents a permeability barrier to hydrophyllic molecules

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bacterial cell wall

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bacterial cell wall is composed of peptidoglycan; functions to provide support and prevent osmotic lysis

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glycan tetrapeptide

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building block of peptidoglycan

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what cleaves peptidoglycan?

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autolysins and lysozyme

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LPS Structure

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Consists of three parts:
1. Lipid A: fatty acid + N-acetylglucosamine phosphate
2. core polysaccharide: KDO (2-keto deoxyoctanoic acid), heptoses, other sugars
3. O-antigen: some unusual sugars, heterogenous

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what linkage does lysozyme cleave on peptidoglycan?

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the Beta 1,4 glycosidic linkage

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Components in gram positive cell surface

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about 25 layers of peptidoglycan, teichoic acid, lipoteichoic acid (LTA)

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Components in gram negative cell surface

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outer membrane composition: composed of lipopolysaccharide (LPS), lipid A, core polysaccharide, O-antigen

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lipid A

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toxin that affects eukaryotes (called endotoxin)

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core polysaccharide

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composed of unusual sugars

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O-antigen

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composed of unusual sugars; can be heterogeneous between species or even between a variety of same species; can be recognized by immune system

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capsule

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coat of polysaccharide; functions for protection and fooling white blood cells, helps bacteria to stick

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flagellin

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protein that is in flagella of bacteria

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peritrichous flagella

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flagella around entire surface of bacterium

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polar flagella

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flagella centered at one "pole" of bacterium

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gene expression

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pathogen response to environment

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protein secretion

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pathogen influence over environment

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RNA polymerase

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core enzyme; carries out polymerization of RNA

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sigma factor

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initiates transcription; bacteria can have a few to 50 sigma factors

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promoter

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site where the initiation of transcription occurs

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intrinsic terminators

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sequence that promotes termination of transcription

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stem loop in RNA

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binds to polymerase and knocks RNA polymerase off DNA and causes transcription termination

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operon

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found only in prokaryotes; complete unit of transcription

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regulon

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co-regulated operons in response to environmental changes

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polar effect

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genetic phenomenon that arises when a mutation in an upstream gene in an operon can stop transcription or can stop transcription/translation of downstream genes

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global control systems

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regulate many operons all at the same time

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phosphotransfer

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phosphate group transferred is an Asp group (response regulator)

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accessory secretory pathways

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possessed only by gram negative bacteria

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Type III secretion pathway

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contact dependent pathway; injectisome

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bactericidal

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antibiotic kills bacteria (bug doesn't lyse)

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bacteriostatic

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antibiotic doesn't kill pathogen but prevents growth

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bacteriolytic

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antibiotic causes the bacteria to die and lyse

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MIC

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minimal inhibitory concentration; the amount need of an antibiotic to stop bacterial growth

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MBC

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minimal bactericidal concentration; the amount needed of an antibiotic to cause bacteria to die (concentration that kills bacteria)

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antibiotic antagonism

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together, two antibiotics work worse

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antibiotic synergism

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together, two antibiotics work better

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broad spectrum antibiotics

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hit lots of bacterial targets

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narrow spectrum antibiotics

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hit few or one type of bacterial targets

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selective toxicity

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relative toxicity to the bacteria compared to the host

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targets of antibiotics

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antibiotics target essential bacterial machines of macromolecular biosynthesis such as: cell wall synthesis, protein synthesis (majority of antibiotics), nucleic acid biosynthesis, folic acid metabolism

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Beta lactam antibiotics

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Includes penicillins, ampicillin, cephalosporins; name derived from the 4 member beta lactam ring they all have in common; bacteriocidal (kill only growing bacteria); only negative aspect is development of allergic reactions; structural analogs of D-alanyl-D-alanine. Act by binding to enzymes involved in peptidoglycan biosynthesis which blocks transpeptidation and promotes activity of autolysins and lysis

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vancomycin

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glycopeptide that inhibits peptidoglycan synthesis; binds D-ala-D-ala; extremely important in treatment of gram positive bacteria and is the last line of defense against them

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aminoglycosides

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protein synthesis inhibitor; target the 30s subunit resulting in misreading of mRNA and are cidal. Examples are streptomycin, kanamycin, and gentamycin; don't penetrate membranes

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erythromycin

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macrolide that targets the 50s subunit. Can be cidal or static

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Tetracycline

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targets the 30s subunit and is static. Use of tetracycline and beta-lactam antibiotic together can result in antagonism. Beta lactam and aminoglycoside is synergistic; wonderful pharmacology, drawbacks include resistance and side effects on the developing teeth of children

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ciprofloxicin

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nucleic acid synthesis inhibitor; quinolone antibiotic and drug of choice for treatment of anthrax

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trimethoprim

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inhibitor of folic acid metabolism, folate analogue blocks another step in the tetrahydrofolic acid pathway, this time dihydrofolate reductase

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sulfonamides

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structurally similiar to paraaminobenzoic acid, a substrate for the first enzyme in the tetrahydrofolic acid pathway; inhibitor of folic acid metabolism

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chloramphenicol

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antibiotic that is a protein synthesis inhibitor

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mechanisms of antibiotic resistance

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endogenous, multi-drug transport, spontaneous, inactivating enzymes, target

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Satellites

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bugs that aren't resistant to a certain antibiotic in a plate but grow because they are in a non-antibiotic area due to the presence of a bug that is antibiotic resistant

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non-phagocytic cells

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don't normally eat bacteria in the environment

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phaogocytes

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eat bacteria; neutrophiles, macrophages, dendritic cells

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Phagocytosis

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process for cellular eating, specialized to eat bacteria

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chemotaxis

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directed movement that is controlled by a gradient of chemical attractant

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chemokines

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call other cells to infected/wounded areas

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why is the permeability of LPS/L bilayer of OM so low?

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Bridging by divalent cations, of anionic groups in LPS

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spontaneous acquired resistance

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when a bacterium suddenly acquires resistance to a antibiotic; may have arisen due to the following explanations:
1. Some particularly robust cells in the population might adjust to the harsh environment
2. exposure to the toxic conditions might produce rare resistant mutations in the population of bacteria (i.e. induced mutations)
3. spontaneous mutants might have occurred in the bacterial population prior to exposure to the toxic conditions yielding resistant progeny cells
4. single point mutations to drug resistance that arise at normal mutation frequency (10^(-6) to 10^(-9)

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why is spontaneous resistance not clinically significant for most pathogens?

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this is because a spontaneous resistance usually results in the reduced virulence of the pathogen

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antibiotic resistance acquired by genetic exchange

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plasmids and transposons may encode one or more different antibiotic resistances and thus selection for one antibiotic can lead to resistance to other antibiotics

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how does erythromycin resistance work?

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erythromycin resistance is mediated by methylation of an adenine on the 23 rRNA

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how does vancomycin resistance work?

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mediated by changing the terminal D-ala-D-ala to D-ala-D-lactate or D-ala-D-serine

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approximately how many pounds of antibiotics are used each year?

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50 million pounds

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polarization step

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controlled by Cdc42

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protrusion step

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controlled by Rac

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Adhesion

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controlled by Rho

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Translocation

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controlled by Rho

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what drives protrusion?

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polymerization

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adenylate cyclase

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converts ATP to cAMP

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fMLP

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formylmethionine- unique to bacteria

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complement

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C5a complement component

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chemoattractants

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attract cells that are sensitive to the attract

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heterotrimeric GTP binding proteins

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GTPases

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actin cytoskeleton

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made up of actin protein

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stages of conversion from G-actin to F-actin

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1. nucleation
2. elongation
3. depolymerization

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Zipper mechanism of induced phagocytosis in non-phagocytic cells

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actin polymerizes only immediately around bacterium

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trigger (splash) mechanism

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induced by type III secretion effectors. Actin polymerizes in broad area around bacterium

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opsinized

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coated

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plasmids

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extrachromosomal DNa that can vary in size; most bacteria from wild have one or more plasmids; not rare but cryptic

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plasmid encoded properties

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1. replication functions
2. fertility
3. antibiotic resistance
4. heavy metal resistance
5. virulence genes
6. bacteriocims- protein made by 1 bacterium that kill other bacteria
7. alternative Fe acquisition

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characteristics of plasmids

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1 kB to 300 kb in size (1 gene to 3000 genes); host range is either narrow or broad; copy number can range from one per chromosome equivalent to high copy number

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curing

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loss of a plasmid

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conjugation

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mediated by transfer (tra) proteins that encode pili.

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F-pilus

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complex retractable organelle that mediates bacterium-bacterium interaction

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mobilization

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piggy-back transfer mediated by mob and an Origin of transfer (ori)

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Rec A

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signature gene involved recombination and is a major part of natural transformation

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Rec-dependent recombination

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general or homologous recombination results from the genetic exchange between homologous DNA from two different sources. Rec A is an enzyme necessary for this process

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competence (competent bacteria)

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state of readiness to accept naked DNA

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electroporation

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method for introduction of plasmid DNA into many different bacterial species simply by inducing holes in the cell membrane via electronic pulses

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unnatural transformation of plasmid DNA

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calcium and cold-shocked induced; works great for e. coli but not in most

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Transposons

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jumping genes and are important in the evolution of multiple antibiotic resistance

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General properties of transposons

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ubiquitous in nature, found on chromosome, plasmids, and phage; Rec-independent, transposons hop at a frequency of 10^(-3) to 10^(-7), encode transposase, have inverted terminal repeats at their ends, minimal target sequence specifically bordering on random, often confer antibiotic resistance, regulated (controlled by transposase and repressor), generate polar mutations due to presence of transcriptional terminators

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conservative transposon

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copy number doesn't increase upon transposition but can result in two copies per chromosome

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replicative transposon

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Tn is copied upon transposition resulting in two copies

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conjugative

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transposon encodes plasmid-like tra functions: excises, transfers by conjugation to another host and re-inserts

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transformation (genetic exchange)

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DNase-sensitive DNA uptake. RecA-dependent for chromosomal markers, not plasmids

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conjuation (genetic exchange)

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DNase-insensitive, contact dependent, RecA-independent

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Transposition

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DNase-insensitive, recA-independent, contact independent within bacterium, but dependent between bacteria

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Transduction (genetic exchange)

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filterable, RecA-dependent

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pathogenicity islands

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often have different G+C content than chromosomal DNA and usually have virulence genes on them

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transposon mutagenesis

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transposable elements that can be introduced into the genome of bacteria where they insert somewhat randomly causing insertion mutations

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transposon library

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collection of bacteria that contains multiple individuals each with a single transposon insertion

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reporter

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used in biological systems to quantitate gene or protein expression. usually an enzyme with easy properties to measure

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transcriptional fusions

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rely on the promoter of a target gene but contain own ribosome binding site and start codon.

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translational fusions

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in-frams fusions between two proteins so that the promoter, ribosome binding site, start codon and some or all of the coding sequence are fused in frame with another protein

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Tnlac

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transcriptional or translational fusions

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TnPhoA

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Translational fusions to identicy genes encoding proteins with signal sequences

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forward genetics

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use transposon library; select for mutatnts affecting phenotype, identify site of insertion

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reverse genetics (biased)

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start with a genomic sequence, identify gene based on homology that you hypothesize has important phenotype
introduce mutation: insertion, deletion or point
score phenotype

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Transposon site hybridization

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to identify genes that are expressed under one condition relative to another

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cytokines

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are a category of signaling molecules that, like hormones and neurotransmitters, are used extensively in cellular communication. They are proteins, peptides or glycoproteins. The term cytokine encompasses a large and diverse family of polypeptide regulators that are produced widely throughout the body by cells of diverse embryological origin.[1]

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chemokines

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subset of cytokines that make cells move towards them

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PAMP's

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pathogen associated molecular patterns

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Prr's

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pattern recognition receptors

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NLR's

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nod-like receptors

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Nalips, Naips, Ipat

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activate inflammasome

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inflammasome

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activates protease called caspase one that cleaves pro-IL-1 to IL-1

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complement

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group of proteins in blood, bind pathogen and promote inflammation; C1 to C9

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antigen

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any molecule that can be recognized by the immune system; some small piece of protein, cell wall, etc. that will be recognized by a receptor on a B or T cell

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IgM

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good at activating complement

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IgA

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easy to secrete across epithelial barriers and mucosal surfaces

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IgG

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promotes phagocytosis