Microbiology USMLE 2011

225 terms by akattan 

Create a new folder

Advertisement Upgrade to remove ads

Pulled from FA, notes from Goljan RR, and Robbins, and USMLE World practice questions

what are the four virulence factors of neisseria meningitidis?

polysaccharide capsule, LPS endotoxin, pilli (for attaching to resp. mucosa), and IgA protease (so its pilli can do its job)

what does the vaccine to n. meningitidis include?

polysaccharide capsule and peptide conjugated to it

which bugs have heat killed bacteria in their vaccines?

bordatella pertussis, vibrio cholera, and yersinia pestis

which bugs have recombinant bacterial protein in their vaccines?

borrellia burgdorferi

which bugs have inactive toxin in their vaccines?

corynebacterium diptheriae and clostridium tetani

what is the BCG vaccine used for? what does it contain?

TB; contains LIVE organisms (attenuated) of different myocbacterium

Other than TB, which bugs use live attenuated organisms in their vaccines?

salmonella typhi and francisella tularensis

what color do gram positive stain? gram negative?

blue; red

which has a thinner cell wall gram negative or gram positive?

gram negative

which has periplasmic space, gram positive or gram negative?

gram negative

T/F only gram negative can secrete capsules.

false!

what does a capsule do?

protect against phagocytosis

what can be found in the periplasmic space of gram negative bugs?

beta lactamases

what is the cell wall of bacteria made of ? which bacteria have it- gram negative or positive?

peptidoglycan (sugar backbone crosslinked by peptide side chains); both

what is the purpose of the cell wall in bacteria?

protect against osmotic pressure and give rigid support

what is the major cell antigen for gram positive bacteria? where is it found?

teichoic acid; both in the cell wall and cell membrane

what does teichoic acid induce? and how?

shock via TNF and IL 1

what is the major cell antigen for gram negatives? where is it found?

polysaccharid "O" found in the Lipopolysaccharide (LPS) in the outer membrane

what is Lipid A and where is it found?

it induces TNF and IL 1 and is found in the gram negative cell wall LPS (lipopolysaccharide- the lipo part)

what does the plasma membrane of bacteria have? what occurs there?

site of oxidative and transport enzymes (including peptidotransferase)

what are the subunits of ribosome of bacteria?

50s and 30s

what does a capsule provide? what bacteria is the exception to the rule that capsules are made out of polysaccaride? how does the immune system get rid of bacteria with capsules?

protection from phagocytosis; bacillus anthracis- D glutamate; opsonization and when gets filtered in spleen then fixed macrophages attack

T/F the pilus/fimbria provide motility

false; the flagellum do

T/F the flagellum provide adherence to cell surfaces and attachment for conjugation

false; the pilus/fimbriae do

which is longer the pilus or the flagellum? which is made out of glycoprotein? which only protein?

flagellum; pilus; flagellum

which bacteria has flagella that are periplasmic? are the gram negative or positive? what is required to visualize one of these species?

spirochetes; gram negative; dark field microscopy for treponema

what is the spore made of? what does it protect the bacteria from?

keratin like coat made of dipicolinic acid; dehydration, heat and chemicals

what is a glycocalyx? what is it made of? what does it help bacteria with?

a biofilm; polysaccharide; foreign surfaces

what is the prototypical bacteria that uses a glycocalyx capsule for a biofilm formation? is it streptococcus or staphylococcus?

s. epidermitis; staphyloccus

which bacteria do not gram stain well?

intracellular: chlymadia, rickettsia, legionella (fac);no cell wall: mycoplasma; too much lipid: mycobacteria; too small: treponema

other than dark field microscopy , what else can be used to confirm treponema presence?

flourescent antibody staining

what is used to visualize legionella since they dont gram stain well?

silver stain

other than being intracellular, what else makes it difficult to gram stain chlymadia?

lack muramic acid in cell wall

what bugs can be stained with giemsa?

borrelia, plasmodium, trypanosomes, chlamydia

which bugs can be stained with PAS?

Tropheryma whippelii, some fungi and some amoeba

what does PAS stand for? what is it? what does it visualize?

period acid schiff; a special stain to visualize to certain bugs and glycogen and mucopolysaccharides

What is Ziehl Neelsen? what is it used for?

a stain; to visualize acid fast organisms (mycobacterium, nocardia, cryptosporidium)

What is India ink? what is it used for?

a special stain; to visualize encapsulated organisms (not just bacteria- cryptococcus neoformans also!)

what is mucicarmine? what is it used for?

a stain; also can stain capsules (turns red) (and adenocarcinomas)

what two stains can be used for visualizing capsules?

india ink and mucicarmine

what is silver stain used for?

legionella, and fungi (specifically pneumocystis and candida)

what is another name for silver stain?

methenamine stain

what special culture requirement is needed for H. influenzae? with what factors? what bug can provide what factor?

Chocolate agar with factors V and X (NAD+ and hematin); s. aureus can provide V (NAD+)

What special stain is needed for N. gonorrhea? what is in it?

Thayer_martin media aka VPN (vanc, polymyxin, nystatin)

in stains, where can you sometimes find N. gonnorrhea?

inside the WBCs!

what special culture requirement is needed for N. meningitidis?

chocolate agar

what special culture requirement is needed for B. pertussis?

Bordget-Gengou (potato) agar

what special culture requirements are necessary for Corynebacterium diptheriae?

tellurite plate (potassium); lofflers media

what special culture requirements are required for mycobacterium tuberculosis?

Lowenstein-Jensen agar

what special culture requirements are required for mycoplasma pneumonia?

Eatons agar

What culture is required for lactose fermenting enterics? what color does the agar turn?

MacConkeys agar; pink

other than Macconkeys agar, what else can be used to culture E. coli? what color does the agar turn?

Eosin Methylene Blue (EMB); blue black

what special culture requirement is needed for legionella?

charcoal yeast buffered with cysteine and iron

what special requirement is needed for fungi?

Sabourauds agar

what determines whether a bug is anaerobic or aerobic?

whether it has enzymes like catalase or superoxide dismutase to deal with O2 FR

which are the obligate aerobes?

mycobacterium tuberculosis, pseudomonas aeruginosa, nocardia, bacillus cereus

is bacillus anthracis an obligate aerobe?

no facultative

what are the obligate anaerobes?

actinomyces, clostridium, bacteroides

what are some characteristics of obligate anaerobes? what drugs can they can not be used for these bugs?

produce gas in tissue CO2 and H2 (crepitus) and generally foul smelling (d/t short chain fatty acids) and are difficult to culture; aminoglycosides because they require O2 to enter cells

why are rickettsia and chlymadia obligate intracellular? what age group do they have the worst presentation in and why?

because cant make own ATP; neonatal because require cell mediated immunity

what are the facultative intracellular bacteria? why is this property considered a virulence factor?

salmonella, legionella, neisseria, brucella, mycobacterium, listeria, francisella; because can evade immune system by living unnoticed inside cells

what are the classical examples of encapsulated bacteria? what reaction is used to visualize them? why are they very virulent to asplenic patients?

N. meningitidis, S. pneumonia, H. influenzae, Klebsiella pneumoniae, Salmonella, group B S. agalacteiae; quellung reaction- Ab binds to capsule and then swells; because the way to overcome this virulence factor is to opsonize them where the spleen then phagocytoses them

T/F N. gonorrhea does not have capsule is not a facultative intracellular

false! it is a fac. intracellular (but no capsule)

what is the antigen used for encapsulated organism vaccines?

the capsule conjugated to a peptide (diptheriae toxoid!)

Why are vaccines conjugated to a protein? If not, what would happen?

to activate the T system and then B cell class switching; only IgM antibodies would be produced because T cells dont recognize only the polysaccharide

what four bugs are urease positive? what kind of environment do they create? how?

H. pylori, Ureaplasma, Klebsiella, Proteus; alkaline environment; by splitting urea to make ammonium

what are two virulence factors of klebsiella?

urease, encapsulated

what are the four pigment producing bacteria? what colors?

actinomyces- yellow sulfur granules; s. aureus- yellow pigment; pseudomonas- blue green pigment; serratia- red

what are two virulent factors of proteus?

flagellated and urease

what other virulence factor (other than capsule) evades phagocytosis? what bug has this?

protein A by binding Fc region of Ig- prevents both phagocytosis and opsonization; S. aureus

what is an IgA protease? what bugs have it? what does it allow?

it cleaves secretory IgA (dimer) so that pili can bind to mucosal surfaces or bug can generally colonize it; Neisseria, S. pneumonia, H. influenzae type B

which bacteria has the virulence factor "M" protein? and what does it do?

group A streptococcus; helps prevent phagocytosis

T/F only gram negative bacteria can secrete exotoxin

False

which gram positive bacteria also has endotoxin? what other virulence factor does this bacteria have?

listeria monocytogenes; fac. intracellular

where are the genes of exotoxin located? endotoxin?

plasmid or bacteriophage; bacterial chromosome

T/F Endotoxin has greater toxicity than extoxin

false! endotoxin has higher fatal dose

T/F Endotoxin is more antigenic than exotoxin

False. high titer antibodies called antitoxins are induced in exotoxins; endotoxin in poorly antigenic (some TLR bind to it)

T/F Exotoxin have vaccines but endotoxin does not.

true. toxoids used as vaccines

what is the exception to the rule that exotoxins are destroyed rapidly at 60?

staph aureus enterotoxin

at what temperature are endotoxins destroyed?

they are stable at 100 degrees for one hour!

name three examples of bugs that use pilli as virulence factors.

N. gonorrhea, S. pyogenes, E. coli

what is a superantigen? what two bugs use them?

its an exotoxin that binds directly to MHC II and T cell receptor simultaneously crosslinking to activate large numbers of CD4 th2 cells to release massive amounts of IFN gamma and IL2

which bug has the TSST 1 superantigen and causes toxic shock syndrome?

s. aureus

what is scarlet fever? what bug causes it and how?

toxic shock like syndrome caused by s. pyogenes by secreting erythrogenic toxin

what are ADP ribosylating toxins?

they interfere with the host cells function; the B component binds to a receptor on the surface of the cell which enables endocytosis- A comp then attaches an ADP ribosyl to a host cell protein (ADP ribosylation) which alters the host cells function

What is exotoxin A? which two bugs have it?

It is an ADP ribosylating AB toxin that inactivates EF 2; Corynebacterium diptheriae and Pseudomonas Aeurginosa

what type of exotoxin does Vibrio cholera have? what does it do? what toxins are similar?

ADP ribosylating AB exotoxin; ADP ribosylation of Gs protein which activates adenylyl cyclase which increase pumping of CL out into gut (and decrease NA reabsorption) [upregulates CFTR]; ST and LT of ETEC

What type of exotoxin does E. Coli have? what do they do? how are they different?

both are ADP ribosylation AB exotoxins: heat labile exotoxin stimulates adenylate cyclase and heat stable stimulate guanine cyclase

what type of exotoxin does bordetella pertussis secrete? what does it do?

ADP ribosylation AB exotoxin; inhibits G alpha inhibitor resulting in increase of cAMP which causes an inhibition of chemokine receptor causing lymphocytosis (no neutrophils or macrophages come)

what type of enzymes inhibit cAMP?

phosphodiesterases

what type of toxin does clostridium perfringens have? what does it do?

alpha toxin exotoxin; a lecithinase that acts as a phospholipase to cleave cell membrane and cause gas gangrene

what type of hemolysis does the alpha toxin of clostridium perfringens do on blood agar?

double zone! (d/t alpha toxin lecithinase that acts as a phospholipase)

what type of toxin does clostridium tetani release?

an exotoxin that blocks the release of GABA and glycine (inhibitory neurotransmitters) in Renshaw interneurons which causes lockjaw

what type of toxin does clostridium botulinum release?

an exotoxin that blocks the release of acetylcholine and causes anticholinergic symptoms, CNS paralysis, especially in cranial nerves (ptosis, difficulty swallowing)

what type of exotoxin does Clostridium dificile have?

ADP ribosylation AB toxin- A toxin results in actin depolymerization and loss of cytoskeletal structure- cytotoxicity and necrosis

what type of toxin does bacillus anthracis have?

exotoxins that are called "edema factor" and "lethal factor"; edema factor causes edema because it is a bacterial adenylase cyclase itself; lethal cactor causes an increase in TNF alpha and IL 1

what kind of toxin does Shigella have? what other bacteria secretes this toxin?

exotoxin that cleaves host cell rRNA 60S and enhances cytokine release; molecular mimicry can result in HUS; E. coli O157:H7

What type of exotoxin does group A s. pyogenes have?

streptolysin O is a hemolysin and the antigen for ASO antibody, which is used for diagnosis of rheumatic fever

what are the five camp inducers? how do they do it?

vibrio Cholera (by ADP ribosylating Gs), bacillus anthracis (exotoxin is a bacterial adenyly cyclase itself), e.coli heat labile toxin (activates adenylyl cyclase), pertussis exotoxin inhibits Gi causing Whooping cough and lymphocytosis by inhibiting chemokine receptors

what toxins activate cGMP?

heat stable toxin of E. coli (ETEC), yersinia pestis, and B. cereus

other than S. epidermitis on prosthetic valves, what other bacteria forms biofilms?

P. aeuriginosa in CF patients in respiratory system

what are three actions of lipid A of endotoxin?

1) activates macrophages: IL1, TNF, NO
2) activates complement via alternate pathway: C3a (hypotension and edema), C5a (neutrophil chemotaxis)
3) activates Hageman factor (coagulation cascade activator and DIC)

what is the lag phase in the bacterial growth curve?

metabolic activity without division

what is the log phase in the bacterial growth curve?

rapid cell division

what is the stationary phase in bacterial growth curve?

nutrient depletion slows growth or spore formation

what is the death phase in the bacterial growth curve?

prolonged nutrient depletion and building of waste products lead to death

how do bacteria replicate?

binary fission

how do bacteria exchange genetics?

transformation, conjugation, transduction or transposition

T/F bacteria are diploid

false - haploid

what does it mean for a bacteria to be "competent"?

it means it can take part in transformation- or it has the membrane proteins that allow it to take up DNA of the same species from the enviroment

which bacteria can transform?

SHiN

what is the most common type of genetic exchange in bacteria?

conjugation

in F+x F-conjugation, which is the F+ plasmid? can more than the plasmid DNa get transferred in this type of conjugation

the one that contains the genes required for the conjugation process; Plasmid DNA is the only thing that is transferred

what is the difference between Hfr x F- conjugation and F+ x F-?

in the former, F+ plasmid can become incorporated into bacterial chromosomal DNA, replication of incorporated plasmid DNA may include some flanking chromosomal DNA and the so the next transfer may include plasmid and chrom genes

what is transposition?

segment of DNA gets excised and reincorporated from one location to another- from plasmid to chrom for ex.

T/F transposition is a way that chrom genes are transmitted from one bacteria to another

true- excision of chrom DNA can jump into plasmidal DNA and then transferred into another bacterium

other than staph. epidermitis and pseudomonas aer. what else can form biofilms? on what?

systemic candidiasis on IV, catheters, peritoneal dialysis

what are neutropenic patients (and thus CGD patients) really susceptible to?

candidiasis and aspergillosis (and the other opportunistic fungi) and staphylococcus

what are the two types of nucleocapsids for viruses?

icosahedral and helical

what viruses can be helical?

RNA

what is the nucleocapsid shape of DNA viruses? what is the exception?

icosahedral; POX virus (complex)

what is the surface protein made of on viruses? where is it located?

glycoprotein (usually pulled from membrane they burst out of!); the envelope

what is the only virus that doesnt have an envelope from a plasma membrane? where is it from?

herpesviridae family; nuclear membrane

what is recombination?

a form of viral genetics between two chromosomes by crossing over within regions of base sequence homology

what kind of viral genetics results in antigenic drifts?

recombination

what is reassortment?

a form of viral genetics between two viruses with segmented genomes- they exchange segments and is a form of high frequency recombination

what is the cause of worldwide pandemics?

reassortment

what is the cause of antigenic drifts?

reassortment

what is complementation?

a form of viral genetics; when one virus in a cell has a defunct protein and another virus comes in and saves it with its own protein that serves both viruses

what the phenotypic mixing?

a form of viral genetics when two viruses infect the same cell and one virus' genes is covered in another virus' surface proteins- the result is that the virus genes are taken to a place it usually doesnt go (to whereever the glycoproteins of the other virus directed to)

what are the live attenuated viral vaccines?

Sabin's polio, adeno, small pox, yellow fever, chickenpox (VZV), MMR

what are the killed viral vaccines?

Rabies, influenza, Salk polio, and HAV

what are the recombinant viral vaccines?

HBV (antigen is a recomb HbsAg), HPV (6,11,16,18)

what is the only live attenuated vaccine you can give to HIV positive patients? can you give it to pregnant women?

MMR; no

are boosters needed for live attenuated vaccines?

no

what is the difference in immunity induced between a live attenuated and a killed vaccine?

live attenuated make both humoral and cell mediated immunity whereas killed vaccines only make humoral

what is the drawback to live attenuated vaccines?

they are dangerous to give to immunocompromised because they chance to revert to virulence (killed vaccines are stable)

which DNA genomes are not linear?

Polyoma, Papilloma, Hepadna (circular)

which RNA viruses are ds?

Reo and Rota (part of Reo fam)

which RNA viruses are double stranded?

retroviridae, Togavirus, Flaviviruses, corona , hep E virus, calicivirus, picornavirus

are naked nucleic acids of (-) ssRNA viruses infectious? how about naked dsRNA nucleic acids of viruses?

no; no; they require enzymes in complete virion

are naked nucleic acids of +ssRNA and dsDNA viruses infectious? what are the exceptions?

yes; POX and HBV

T/F all viruses are haploid

FAlse- all are except retroviruses which have 2 identical ssRNA molecules

T/F All RNA viruses replicate in the cytoplasm

false- all except influenza and retroviruses

T/F All DNA viruses replicate in the nucleus

False-all except POX

which viruses are naked? ie no envelope?

Naked CPR PAPP: Calicivirus, Picornavirus, Reovirus, Parvovirus, Adenovirus, Papilloma, and Polyoma

what is the exception the rule that viruses get their envelopes from the plasma membranes they lyse out of?

herpes family gets it from the nuclear membrane they leave out of

what is the virus with the bullet shaped nucleocapsid?

rabies

are enteroviruses enveloped are not?

no

See More

Please allow access to your computer’s microphone to use Voice Recording.

Having trouble? Click here for help.

We can’t access your microphone!

Click the icon above to update your browser permissions above and try again

Example:

Reload the page to try again!

Reload

Press Cmd-0 to reset your zoom

Press Ctrl-0 to reset your zoom

It looks like your browser might be zoomed in or out. Your browser needs to be zoomed to a normal size to record audio.

Please upgrade Flash or install Chrome
to use Voice Recording.

For more help, see our troubleshooting page.

Your microphone is muted

For help fixing this issue, see this FAQ.

Star this term

You can study starred terms together

NEW! Voice Recording

Create Set