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96 Cards in this Set
- Front
- Back
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Which staph are normal flora of the skin?
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S. epidermis
S. lugdenensis S. haemolyticus |
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What is diagnostic for S. aureus?
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beta-hemolysis on BAP
yellowish to golden pigmented colony |
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What is diagnostic for S. epidermis and S. saprophyticus?
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non-pigmented colonies
NO hemolysis |
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In which phase of the bacterial growth curve does exotoxin production increase?
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stationary
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In which phase of bacterial growth do adaptive changes take place?
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stationary phase
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During the lag phase of bacterial growth, what is a virulence factor that may be produced as the bacteria adapts to the culture medium?
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siderophore - iron chelator released to bind iron with HIGH affinity
solubilize ferric iron and return with iron to receptor on bacteria virulent factor because can steal iron from the host's transferrin and lactoferrin |
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Why are bacteria especially affected by environment?
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no specialized cells for homeostasis
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What are some examples of species that are obligate aerobes?
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bacillus
psuedomonas mycobacterium |
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In the TCA cycle in bacteria how many NAD and FAD act as electron acceptors?
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3 NAD
1 FAD |
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In bacteria undergoing aerobic respiration what is the order of the electron transfer chain?
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NADH
flavoproteins cyt b cyt c cyt a O2 - oxygen final electron acceptor! |
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Why is iron so essential for bacteria?
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Their cytochromes contain iron and undergo reversible Fe(II)-Fe(III) valence changes to carry the electrons toward oxygen
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In bacteria undergoin fermentation what is the source of ATP?
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substrate level phosphorylation (NO electron transport)
organic compounds serve as both electron donors and acceptors |
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What are 2 alkylating agents used for bacterial sterilization?
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ethylene oxide
formaldehyde |
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What are some oxidizing agents used for bacterial sterilization?
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hydrogen peroxide
iodine (activity reduced by organic compounds, clean skin first) chlorine compounds (oxidize sulfhydryl groups) |
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What are some membrane disrupting agents used to sterilize?
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quartenary compounds
alcohols soaps/detergents |
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What is the MOA of penicillins and cephalosporins?
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inhibit bacterial cell wall (murein) formation
BACTERICIDAL |
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What is the MOA of nalidixic acid and quinolones?
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bind bacterial gyrase to prevent DNA replication
BACTERICIDAL |
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What is the MOA of aminoglycosides?
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bind bacterial 30S ribosomal subunit and inhibit elongation because subunits held together more tightly
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What is the MOA of rifampin?
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bacteriostatic that binds bacterial RNA polymerase and prevents transcription
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What is the MOA of chloramphenicol, lincomycin, and erthromycin?
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bacteriostatic that bind bacterial ribosomes and inhibit peptide bond formation
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When do mutations occur?
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BEFORE selection
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What is a cistron?
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genetic units composed of several genes encoding proteins in the same pathway; enzymatic pathways may consist of several cistrons
single mutation can inactivate the WHOLE pathway |
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Why do bacteria have circular DNA?
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because have lots of exonucleases that would degrade ends of linear DNA
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Which bacteriophages contain both DNA and RNA?
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NONE
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What are the stages of the lytic cycle of a bacteriophage?
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replication
transcription assembly release |
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What is the lysogenic cycle?
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stable association of bacterial and viral DNA; viral DNA replicate as part of bacterial chromosome and prevented from lytic cycle by production of its own repressor protein
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What can induce a lysogenic phage into lytic growth?
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UV light
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What is the difference between a gamma and a mu phage?
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both are lysogenic phages
gamma prophage integrates into a specific site on chromosome OR remains as plasmid mu prophage integrates at many sites, like a transposon |
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What constitutes the bacterial "immune system"?
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restriction enzymes: degrade DNA with a different methylation pattern
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What is OBED?
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acronym for the genes phages carry:
O antigen control (salmonella) Botulinum toxin (C. botulinum) Erythrogenic toxin (S. pyogenes) Diphtheria toxin (C. diphtheriae) |
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What is a transducing phage?
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phage that has mistakenly incorporated piece of bacterial DNA
generalized transducing phage because every gene had equal chance of being incorporated |
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What is necessary for new combinations to be made after infection with transducing phage?
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recA gene to complete homologous recombination
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What is site-specific recombination?
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mechanism for combining circular pieces of DNA
NO homology required; NO DNA lost requires restriction endonuclease |
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What is homologous recombination?
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mechanism for incorporating linear pieces of DNA into chromosome
MUST be some sequence homology recombinase A (recA) required exchange of DNA |
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What is transformation?
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free pieces of DNA taken up by competent bacteria; one strand degraded while other enters
homologous recombination replaces host DNA strand but NO net addition of DNA |
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How does recombination frequency affect DNA transmission?
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the closer 2 genes are on the chromosome, more likely they are to be co-transmitted in random fragment
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What enables a bacteria to be competent?
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becomes competent when environmental conditions are harsh
mechanism: release of small protein that acts to expose a DNA binding protein on the surface of its neighbors |
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What is an example of transformation occuring in vivo?
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type-specific change of capsular polysaccharide of S. pneumoniae
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What is transduction?
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bacteriophage mediated exchange of DNA; generalized or specialized (when phage takes adjacent gene with it during excision)
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What is conjugation?
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direct plasmid transfer between bacteria through the sex pilus in gram negative
gram positive clump instead |
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What encodes for sex pili in E. coli?
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F plasmid
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How do nonconjugative plasmids get transferred during conjugation?
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since they do not promote their own transfer can only be mobilized by a conjugative plasmid in the same cell
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What is high frequency recombination?
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when the F plasmid is integrated into the donor bacterium genome
the genome adjacent to plasmid can be transferred during conjugation genes closest to plasmid origin of transfer are transferred first, plasmid fertility genes transferred last |
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Can an F+ bacteria conjugate with another F+ bacteria?
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NO only conjugate with F-
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What is the tra operon?
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plasmid operon containing genes for sex pili, conjugal DNA metabolism, etc.
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What causes a sex change after bacterial conjugation?
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the transfer of the tra region, so Hfr x F- mating causes no sex change since tra never gets transferred
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What are insertion sequences?
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transposable genetic elements that ADD new DNA
short, inverted terminal repeats; the DNA between the inverted repeats code for genes needed for transposition - transposase the insertion often disrupts a gene, inactivating it and causing mutation |
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What are transposons?
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transposable genetic elements that are larger than insertion sequences and carry extra genes
have IS-like elements at ends |
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What are some functions encoded by tansposons?
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heat stable enterotoxin of E. coli
ampicillin resistance of H. influenzae, N. gonorrhoeae bacteriophages like mu |
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How do plasmids obtain multiple antibiotic resistance?
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collect transposons
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How do streptococci obtain energy?
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by fermentation, sugar fermentation patterns used for identification
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Do streptococci produce lactic acid?
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yes
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What is the Lancefield classification based on?
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C carbohydrate of cell wall
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Which streptococci group is the most virulent of them all?
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group A
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What is unique about the group A strep capsule?
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contains hyaluronic acid - same substance in human connective tissues so is antiphagocytic but NOT anitgenic
virulence factor! |
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How does M-protein contribute to group A strep virulence?
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long protein that extends through wall, has high affinity for factor H, collects this on its wall and thus collects complement inhibiting factors on its wall
antiphagocytic! m-protein target of immune system in post-infectious sequelae |
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What is lipoteichoic acid?
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product of group A strep that functions as an adhesin: binds organisms to host cell membranes
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What does streptokinase and streptodornase do?
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streptokinase degrades fibrin
streptodornase degrades DNA together they liquefy pus |
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What is one of the most important virulence factors of group A strep?
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protease! leads to its invasiveness
hyaluronic acid on capsule and M-protein also virulent factors |
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What are the extracellular products of group A strep?
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streptolysin O and S
streptokinase streptodornase hyaluronidase pyrogenic exotoxins c5a peptidase protease |
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Which group A strep product is the basis for the ASO titer?
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streptolysin O
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Which group A strep product is the basis for the ABD titer?
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streptodornase
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What are superficial infections caused by s. pyogenes?
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pharyngitis: strep throat
impetigo |
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What are some invasive infections caused by s. pyogenes?
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puerperal sepsis
erysipelas and necrotizing fasciitis lymphangitis and lymphadenitis strep sepsis strep toxic shock syndrome |
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What is acute rheumatic fever?
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immune-mediated disease following group A strep pharyngitis
causes arthritis, carditis, and sydenham's chorea concepts of pathogenesis: humoral autoimmunity, cellular autoimmunity, superantigens |
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What are used to diagnose post-infectious sequelae of group A strep?
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ASO and ADB titers, make diagnosis of recent infection
remember streptolysin O is basis for ASO streptodornase basis for ADB |
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Which drug is used for treatment and prophylaxis in group A strep infections?
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penicillin - used long term as prophylaxis for patients who have had acute rheumatic fever
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What is the most important cause of neonatal sepsis and meningitis?
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Strep agalactiae - group B strep
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What is the CAMP test clinically useful for?
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identifying unknown beta-hemolytic strep
group B strep tests positive, group A negative group B strep ONLY gram positive cocci to give positive test (amplified hemolysis when streaked next to staph aureus) |
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What bacteria are part of the group D streptococci and which diseases are they generally associated with?
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enterococcus and strep. bovis
can cause UTI, peritonitis, subacute bacterial endocarditis |
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A bacteria species is able to grow on bile esculin and 6.5% NaCl, which could it be?
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enterococci
ALL group D can grow on bile esculin but only enterococci can also grow in the high salt medium, strep bovis can not |
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All enterococci have "intrinsic" resistance to which group of antibiotics?
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cephalosporins
so usually treated with ampicillin and gentamicin together |
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What is the most common cause of subacute bacterial endocarditis?
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viridans streptococci
also most important cause of dental caries, can get transient bacteremia from dental work leading to SBE |
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How are viridans streptococci identified in the lab?
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basically an alpha hemolytic strep that is not strep pneumoniae
optochin resistant, strep pneumoniae is sensitive |
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What is the pathogenesis of dental caries from viridans strep?
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metabolism ( ie of sucrose) leads to lactic acid production which dissolves the tooth
able to stay on teeth because readily forms biofilms |
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What is the quelling reaction?
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observable microscopic swelling of strep pneumoniae capsule in presence of type specific antibody
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What is the antigenic target of C-reactive protein?
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C antigen of strep pneumoniae
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What are some tests that differentiate strep pneumoniae from other alpha hemolytic strep?
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optochin - pneumo sensitive, alpha resistant
mouse virulence - pneumo +, alpha - inulin fermentation - pneumo +, alpha - bile solubility - pneumo +, alpha - |
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What is the most common cause of ear infection?
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strep pneumoniae
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What are the antigenic structures characteristic of N. meningitidis?
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polysacchardide capsule - major virulence factor
lipooligosaccharide - endotoxin like have pili to help attach to human cells |
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What is Waterhouse-Friderichsen syndrome?
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circulatory collapse which can result from meningococcemia
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What drugs are used to treat N. meningiditis?
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penicillin and third generation cephalosporins
developed resistance to sulfanilamides |
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How does the endotoxin of N. meningiditis cause septic shock?
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stimulates release of lymphokines which cause the septic shock, ie tumor necrosis factor, platelet activating factor
lipooligosaccharide is the endotoxin like cell wall antigen |
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How are the neisseria species differentiated?
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by fermentation
GMLS for glucose, maltose, lactose, and sucrose and gonorrhea, meningiditis, lactamica, sicca |
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What media is used to test for presence of N. gonorrhoeae from a non-sterile site?
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Thayer-Martin medium - vancomycin, colistin, and nystatin inhibit growth of normal flora
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How are the pili of N. gonorrhoeae important?
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contribute to virulence by allowing it o attach to epithelium and resist phagocytosis
type 1 and 2 colonies have pili type 3 and 4 colonies avirulent because have no pili |
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There are 3 outer membrane protein types associated with N. gonorrhoeae, what is significant about protein I?
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associated with lipooligosaccharide, serves as a porin
may facilitate enfocytosis and certain variants associated with human serum resistance |
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How do N. gonorrhoeae alter the local immune response?
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have extracellular IgA protease
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What is ophthalmia neonatorum and how is it prevented?
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infection of the eyes of a newborn by N. gonorrhoeae from vaginal tract
all newborns treated with 1% silver nitrate (crede's procedure) or erythromycin ointment, tetracycline |
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What are the most common manifestations of gonococcal sepsis?
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arthritis and dermatitis
(disseminated gonococcal infection DGI) |
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How is N. gonorrhoeae developing penicillin resistance?
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transfer of penicillinase plasmid by conjugation and transformation
so now use ceftriaxone and spectinomycin |
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What is moraxella catarrhalis?
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can be confused with neisseria
respiratory tract pathogen associated with tracheobronchitis, sinusitis, and otitis media increasing resistance to penicillin |
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What is the significance of coagulase?
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used to differentiate S. aureus from other staph
different from clumping factor which is bound! works with coagluase reacting factor (CRF) to convert fibrinogen to fibrin clot |
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What are some distinguishing lab characteristics of S. saprophyticus?
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novobiocin resistant
coagulase negative no hemolysis |
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What are some distinguishing lab characteristics of S. epidermidis?
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novobiocin sensitive!
coagulase negative no hemolysis |
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What is significant about protein A?
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only found on staph aureus
binds Fc portion of Ig so inhibits opsonization and phagocytosis |
