#2 microbiology

Question 1

Haemophilus will not grow on sheep agar unless Staph aureus is plated, why?

Answer 1

S. aureus, beta-hemolytic, will lyse RBCs and free hematin (X) and secrete NAD+ (V), which is necessary for H. flu growth

Question 2

3 types of botulinism

Answer 2

1. foodborne - eating foods w/ botulism toxin (i.e. canned)
2. wound botulism - toxin production in a wound infected w/ c. botulinum
3. infant botulism - consumes c. botulinum spores, mature into vegetative toxin producing cells in intestine (i.e. contaminated honey)

all three forms can be fatal – medical emergency

Question 3

3 most common clinical manfifestation of botulinism, and Rx?

Answer 3

3 D’s – dipolpia, dysphagia, dysphonia. 12-46 hrs later. antitoxin to sequester circulating toxin, but can’t stop toxin already in cells. supportive.

Question 4

most common bacterial causes of acute otitis media, sinusitis, AND bacteria conjunctivitis are… name 3

Answer 4

1. strep pnemoniae
2. nontypable haemophilus influenza
3. moraxella cattarrhalis

Question 5

what fraction of the body’s total immunoglobulis are produced by splenic B cells

Answer 5

nearly 50%

Question 6

acute rheumatic fever and acute post streptococcal glomerulonephritis are both post-strep infections, following what TYPE of infxn?

Answer 6

1. APSGN: either strep skin infxn (impetigo) or strep pharyngeal infxn
2. rheumatic fever: only with GAS throat infxn

Question 7

classic triad of arthritis, uveitis/conjunctivitis, urethritis

Answer 7

reactive arthritis (HLA-B27 related)

Question 8

strep pnemoniae cannot grow in the presence of…

Answer 8

bile or optochin

Question 9

commonly used clinical disinfectants [4]? which are sporicidal?

what is formaldehyde/glutaraldehyde used for?

Answer 9

1. alcohols (isopropanol, ethanol) - disrupt membrane, denature proteins. NOT sporicidal
2. chlorhexidine - disrupt membrane, coagulate cytoplasm. NOT sporicidal
3. hydrogen peroxide - produces free radicals. SPORICIDAL
4. Iodine - halogenation of proteins & nucleic acids. SPORICIDAL

formaldehyde/glutaraldehyde – alkylating and cross-linking DNA, sterilize hospital equipment that can’t stand autoclave (high pressure steam

Question 10

which anti-malarial drug treats hypnozites?

Answer 10

primaquine (p=prevent relapse). no effect on merozites!

Question 11

most serious long-term adverse effect of chloroquine

Answer 11

retinopathy!! (primaquine doesn’t have this)

Question 12

chloroquine resistant malaria rx: [2]

Answer 12

mefloquine or quinine/doxycycline

Question 13

48hour cycle malaria

Answer 13

p. vivax or ovale (which have hepatic latent stages)

Question 14

lechithinase (or phospholipase C) toxin released by?

Answer 14

Clostridium perfringens - degrades phospholipids. gas gangrene

Question 15

pertussis toxin

Answer 15

exotoxin by bordetella pertussis – stimulates G-proteins to increase cAMP production. increased insulin (hypoglycemia), lymphocyte & neutrophil dysfunction, and increased histamine sensitivity

Question 16

shiga toxin (shigella) and shiga-like toxin (e. coli)

Answer 16

inactivate 60s ribosomal subunit

Question 17

microbes that can cause necrotizing fasciitis [5]

Answer 17

• step pyogenes
• staph aureus
• clostridium perfinges
• strep agalactiae
• aeromonas hydrophila (gram neg rod, non-lactose, oxidase +)

Question 18

coag -, cat-, PYR+, hyaluronidase, m-protein (prevents complement fixation)

Answer 18

strep pyogenes

(s aureus is PYR -)posi

Question 19

positive cAMP test

Answer 19

enhancement of s. agalactiae beta-hemolysis when plated perpendicular to s. aureus

Question 20

medium for isolation of N. gonorrhoeae

Answer 20

thayer-martin;

chocolate agar +

• vancomycin (inhibit gram +,
• colistin (polymixin) to inhibit gram negative (inclu other neisserias),
• nystatin to inhibit yeast, and trimethoprim to inhibit proteus

Question 21

what do nonspecific treponemal test look for (VDRL, RPR)

Answer 21

cardiolipin, by product of treponemal infxn

Question 22

though it is too thin to see on gram stain, treponema is..

Answer 22

gram negative

Question 23

haemophilus ducreyi

Answer 23

forms “chancroid”. similar primary lesion to chancre in syphilis, but painful and swollen regional lymph nodes

Question 24

histoplasma capsulatum

Answer 24

mississippi and ohio river valley. bird and bat droppings. chicken coops and caves.

pulmonary – similar to tuberculosis (lung granulomas w/ calcifications). disseminate to lung, spleen, liver.

hides in macrophages

Question 25

blastomycoses dermatitidis

Answer 25

great lakes. mississippi and ohio river valley. doubly refractive wall, single broad-based bud

Question 26

coccidioides immitis

Answer 26

southwestern states (desert areas). thick-walled spherules w/ endospores. pulmonary flu-like. disseminated skin, bones, meninges

Question 27

paracoccidiodes basiliensis

Answer 27

also dimorphic. mucocutaneous or cutaneous ulcers. progress to lymph nodes and lung. central and south america.

Question 28

two most common causes of hematogenous osteomyelitis

Answer 28

1. staph aureus | 2. strep pyogenes

Question 29

organs affected by cryptococcus neoformas. where is it found?

Answer 29

1. first pulmonary, but often asymptomatic 2. meningitis pigeon droppings! test: red on mucicarmine stain, india ink, serologic testing (latex agglutination) capsular antigen. thick polysacc capsule can form pulmonary nodules.

Question 30

hot tub folliculitis

Answer 30

superficial pseudomonas infection of hair follicle

Question 31

common source of pseudomonas infection

Answer 31

water! hot tub folliculitis, swimmer's ear

Question 32

psuedomonas characterestics

Answer 32

``` gram neg non lactose fermenting oxidase + motile produce pigment (pyocyanin, pyoverdin) ```

Question 33

which viruses acquire membrane from host nucleus

Answer 33

CMV and EBV (herepesviridae family)

Question 34

describe where gp160 is from?

Answer 34

encoded from env gene, glycosylated. proteolytically cleaved in ER and golgi to make gp120 and gp41. both needed to bind to CD4 receptor

Question 35

s. epidermidis causing opportunistic infections in which two scenarios?

Answer 35

1. endocarditis in pts w/ prosthetic valves | 2. septic arthritis in pts w/ prosthetic joints

Question 36

which staff can ferment mannitol?

Answer 36

s. aureus

Question 37

neonates born to HBsAg and HBeAg moms have 1. what risk of chronic infxn 2. replicative rate 3. severity of hepatic injury

Answer 37

1. high risk for chronic infxn 2. high replicative rate 3. MILD hepatic injury (not inherently cytopathic)

Question 38

Guillan-Barre key finding and associated pathogen

Answer 38

loss of deep tendon reflexes, ascending paralysis associated w/ history of camplyobacter jejuni infxn (diarrhea) demyelinating syndrome of peripheral nerves. ascending muscle weakness and paralysis.

Question 39

b. anthracis virulence factors: anthrax exotoxin (edema, lethal, protective) & capsule

Answer 39

1. edema factor: increase cAMP, edema 2. lethal factor: zinc-dependent protease, inhibits MAPK signaling, causes apoptosis, multisystemic physiologic disruption 3. protective antigen -- translocates edema and lethal factor into cytosol antiphagocytic poly-y-D-glutamic acid capsule

Question 40

b. pertussis: (1) pertussis toxin and (2) adenylate cyclase toxin

Answer 40

- pertussis toxin: disinhibits adenylate cyclase through Gi ADP ribosylation, increasing cAMP, edema & phagocyte dysfxn - adenylate cyclase: increased cAMP, edema & phagocytosis two toxins, same end effect

Question 41

c. difficile (toxin A and toxin B)

Answer 41

toxin A: recruits & activates neutrophils, cytokine release --> mucosal inflammation, fluid loss & diarrhea toxin B: induces actin depolymerization; mucosal cell death, bowel wall necrosis, pseudomembrane formation

Question 42

s. pyogenes (pyrogenic exotoxin and streptolysis O&S)

Answer 42

pyrogenic exotoxin: superantigen, induces fever & shock --> scarlet fever and toxic shock streptolysin O & S: damages erythrocytes, beta-hemolysis

Question 43

treatment of acute C. diptheriae infection

Answer 43

1. diptheria antitoxin 2. penicillin / erythromycin 3. DPT vaccine toxin infects neural and cardiac tissue. acute infxn affects naso and oropharynx

Question 44

most common cause of death post-C. diptheriae infxn

Answer 44

cardiomyopathy. (late neuro effects as well)

Question 45

schistosomiasis [3 types]

Answer 45

s. haematobium, urinary s. mansoni, intestinal s. japonicum, hepatic contact w/ freshwater snails, penetrate skin, enter vascular / lymphatics clinical manifestations --> Th2 mediated immune response against eggs: granulomatous inflammation w/ fibrosis

Question 46

s. haematobium [location and symptoms]

Answer 46

north africa, sub-saharan africa, middle east urinary schistosomiasis: terminal hematuria, dysuria, freq urination, hydronephrosis, pyleonephritis, squamous cell carcinoma of bladder

Question 47

s. mansoni [location and symptoms]

Answer 47

sub-saharan africa, middle east, south america, caribbean intestinal schistosomiasis: diarrhea, abdominal pain, ulceration -> iron deficiency anemia

Question 48

s. japonicum

Answer 48

asia [china, philippines, japan] hepatic schistosomiasis: hepatosplenomegaly, periportal fibrosis, portal hypertension PIPSTEM FIBROSIS: pathognomonic for hepatic schistosomiasis, caused by eggs settled into presinuosoidal radicals of the portal vein & fibrosis --> portal hypertension

Question 49

diphtheria toxin (exotoxin w/ AB subunits)

Answer 49

B -- binds growth factor receptor on cardiac and neural cells, induces endocytosis A -- ADP-ribosylation of EF-2

Question 50

nonpulmonary sequelae of mycoplasma pneumonia infection

Answer 50

hemolysis, due to antigenic similarity between cell membranes. COLD AGGLUTINATION! stimulates cross-reactive antibodies.

Question 51

how does Diphtheria acquire virulence?

Answer 51

bacteriopage-mediated infection w/ tox gene

Question 52

how does strep pneumonia acquire virulence?

Answer 52

transformation, ability to produce capsules

Question 53

which bacteria can undergo transformation, take up naked DNA from environment

Answer 53

s. pneumoniae, h. flu, neisseria SHiN

Question 54

complications of herpes zoster

Answer 54

1. post-herpetic neuralgia (rx: topiramate) | 2. herpes zoster ophthalmicus, when VZV is in trigeminal n. v1

Question 55

polyprotein viral product that must be cleaved, often made by which family?

Answer 55

picornaviridae, i.e. echovirus. typically, single stranded, positive sense, linear, nonsegmented RNA

Question 56

gram-positive cocci able to synthesize dextrans from glucose?

Answer 56

``` strep viridans (s. mutans and sanguis). able to produce insoluble extracellular polysaccharides (dextrans) using sucrose as a substrate). help adhere to surfaces ```

Question 57

what causes anterior uveitis (inflammation of the iris) [4]

Answer 57

- herpes virus - syphilis - lyme disease - inflammatory conditions like GLA-B27 related diseases and sarcoid

Question 58

K. pneumoniae is a leading cause of what things

Answer 58

- UTI (e. coli is most common - spontaneous bacterial peritonitis - nosocomial pneumonia

Question 59

HIV-1 provirus. describe 3 structural genes and 6 regulatory genes

Answer 59

structural genes: [needed for virion assembly] 1. gag - antigens in virion core, like nucleocapsid proteins p24 and p7 2. pol - reverse transcriptase, integrase, protease 3. env - envelope proteins gp160 regulatory genes: 1. tat - needed for repl; transcriptionally activates other viral genes. contributes to virulence 2. rev - needed for repl; facilitates transport of unspliced viral transcripts out of nucleus 3. vif 4. vpr 5. nef - enhance viral repl, downreg cd4 & mhcI expression 6. vpu

Question 60

common organisms for.. - urethritis - cystitis - pyelonephritis

Answer 60

urethritis: - n. gonorrhoeae, c. trachomatis cystitis: - e.coli, s. saphrophyticus, p. mirabilis, klebsiella, enterococci pyelonephritis: -same as cystitis

Question 61

common demographic for enterococcal endocarditis in men? women? (i.e. post what procedure)

Answer 61

elderly men who have recently undergone manipulation of areas colonized by this organism, such as GI or GU tract. in women, post-obstetrical procedure GU is usu sterile, but can be contaminated w/ colonic flora in perineum

Question 62

cold agglutination associated w/ which 2 infxn?

Answer 62

- mycoplasma pneumonia - EBV infection and hematologic malignancy

Question 63

name cellular receptor: CMV

Answer 63

cellular integrins

Question 64

name cellular receptor: EBV

Answer 64

CR2 (CD21)

Question 65

name cellular receptor: HIV

Answer 65

CD4 and CXCR4/CCR5

Question 66

name cellular receptor: rabies

Answer 66

nAcR (nicotinic acetylcholine receptor) on peripheral nerve

Question 67

name cellular receptor: rhinovirus

Answer 67

ICAM1 (CD54)