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Smart Book > UWorld-Microbiology > Flashcards

UWorld-Microbiology Flashcards

1
Q

what stage of the malaria life cycle does primaquine attack

what part of the life cycle does chloroquine attack

A

primaquine attacks the intrahepatic stage (this is why it’s useful against latent ovale and vivax infections)

chloroquine attacks the erythrocytic stage

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2
Q

the tetanus vaccine is specific to what aspect of the pathogenesis of tetanus

A

vaccine to tetanus toxoid (leading to development of antibodies against the toxin)

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3
Q

what aspect/ characteristic of H. flu contributes most to its virulence

A

capsule (type b is particularly virulent because its capsule contains ribose instead of hexose, which prevents phagocytosis and intracellular killing)

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4
Q

what does coccidioides immitis look like on histology

A

sphrules containing endospores

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5
Q

what does histoplasma capsulatum look like on histology

A

small oval yeast forms within macrophages

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6
Q

what’s the difference between transformation and transduction in bacteria

A

bacterial transformation involves direct uptake of naked DNA from environment while bacterial transduction involves phage-mediated transfer of DNA

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7
Q

which bacteria are known for having the capability for transformation

A

S. pneumo, H. flu, Neisseria gonorrhoeae and meningitidis

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8
Q

which catalase negative gram positive coccus is pyrrolidonyl arylamidase (PYR) positive

A

S. pyogenes

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9
Q

fever, vesiculoulcerative gingivostomatitis and cervical LAD should make you think of what infection

A

HSV-1

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10
Q

what do you call a smear of an oral ulcer scraping and what stain is most commonly used

A

Tzanck preparation;

Wright-Giemsa stain

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11
Q

what is P-glycoprotein

A

multidrug resistance protein 1 (MDR1);

it is expressed by some cancers to pump out toxins, including chemotherapeutic agents

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12
Q

list the relative amounts of pathogen needed to innoculate a host for the following:
Salmonella, Vibrio cholera, ETEC, Shigella, C. perfringens

A

Salmonella= 10^7; V. cholera=10^6; ETEC=10^8-10^10; Shigella= 10-200; C. perfringens= 500

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13
Q

which gram positive, catalase negative organism grows in 6.5% NaCl

A

Enterococcus (grows in bile also, as does S. bovis, but S. bovis doesn’t grow in 6.5% NaCl)

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14
Q

antibodies against polyribitol ribose phosphate indicate infection with what pathogen

A

Haemophilus influenzae (PRP is part of the capsule)

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15
Q

the main bacterial cause of epiglottitis is

A

Haemophilus influenzae

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16
Q

ether and organic solvents inactivate what kind of viruses

A

enveloped

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17
Q

S. epidermidis is a common cause of foreign body infections (e.g. prosthetic devices) due to what particular survival advantage/ trait

A

ability to produce extracellular polysaccharide matrix known as biofilm

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18
Q

which bacteria produces lecinthinase

A

lecithinase (aka C. perfringens alpha toxin aka phospholipase C) is produced by C. perfringens

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19
Q

what is the mechanism of action of C. diphtheriae AB exotoxin;
which other toxin acts via this mechanism

A

AB exotoxin from C. diphtheriae ribosylates and thereby inactivates elongation factor 2 (EF-2);
Protein A from P. aeruginosa has the same MOA

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20
Q

what is the primary site of complement production

A

the liver

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21
Q

complement C3 deficiency vs. C5-9 predisposes to what particular infections

A

C3 deficiency leads to recurrent infections of encapsulated bacteria
C5-9 predisposes to N. gonorrheae and meningitidis infections

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22
Q

list the top 3 causes of osteomyelitis in sickle cell patients from most common to least common

A
  1. Salmonella (most common)
  2. E. coli
  3. Staph aureus
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23
Q

a woman with rubella will most likely experience what sequelae of the disease

A

polyarthralgia and polyarthritis

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24
Q

a maculopapular rash beginning at the head and neck and spreading downward is characteristic of what two viral infections

A

Measles (rubeola) and German measles (rubella)

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25
Q

first trimester infection with rubella can lead to what neonatal medical issues

A

sensorineural deafness, cardiac abnormalities (e.g. patent ductus arteriosus), and cataracts

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26
Q

when in the course of Hepatitis B infection does anti-HBsAg IgG appear in the patient’s serum

A

after successful vaccination or successful clearance of the virus

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27
Q

what kinds of viruses tend to reproduce polycistronic gene via host production of a polypeptide that is subsequently cleaved

A

+ sense, ssRNA, linear, non-segmented viruses (e.g. echovirus)

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28
Q

50% of all UTI’s in sexually active women is caused by what gram positive organism

A

S. saprophyticus

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29
Q

what are the symptoms of mononucleosis

A

fever, hepatosplenomegaly, pharyngitis and LAD (especially post-cervical nodes)

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30
Q

Waterhouse-Friedrichson syndrome is associated with what pathogen and involves what symptoms

A

caused by N. meningitidis;

involves hemorrhagic destruction of the adrenal glands, DIC and shock

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31
Q

describe the route of N. meningitidis from primary entry site to the meninges (4 steps)

A

pharynx –> blood –> choroid plexus –> meninges

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32
Q

in order for naked RNA to be infectious on its own what qualities must it have

A

positive sense ssRNA (not negative sense or double stranded RNA)

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33
Q

what is the quelling reaction

A

swelling of the capsule seen on microscopy after addition of anti-capsular antibodies

34
Q

gram positive rods with tumbling motility are likely to be contracted how?
what illnesses do they commonly cause?

A

Listeria monocytogenes is an opportunistic pathogen usually contracted in contaminated food (unpasteurized milk, undercooked meat);
cause sepsis, meningitis and neonatal meningitis

35
Q

unilateral vesicular rash in an older patient is most likely what condition?
what sequelae usually arises afterwards?

A

herpes zoster due to reactivation of VZV in a dorsal root ganglion;
post-herpetic neuralgia is the most common neurologic complication of VZV and is more common as age increases

36
Q

list the live attenuated vaccines

A

MMR (measles, mumps, rubella), Sabin polio, intranasal influenza, varicella and yellow fever

37
Q

list the killed or inactivated vaccines

A

cholera, hepatitis A, Salk polio, influenza infection, rabies

38
Q

what acts as endotoxin in N. meningitidis infection

A

lipooligosaccharide (LOS)

39
Q

where does Candida tend to be found

A

skin and mucus membranes (mouth, vagina, intestines)

40
Q

why can’t the body mount a sufficient response against hepatitis C envelope antigen

A

hepatitis C envelope is constantly changing its antigenic structure via mutation because it has a hypervariable region and there is no 3’ to 5’ exonuclease activity in the virally encoded RNA polymerase

41
Q

what does cryptococcus neoformans look like under the microscope

A

yeast only; round or oval encapsulated cells with narrow-based budding

42
Q

what is the most common cause of hematogenous osteomyelitis

A

S. aureus (then S. epidermitis)

43
Q

what are two major symptoms associated with acute-streptococcal glomerulonephritis

A

facial edema and dark urine

44
Q

what is the most common site of colonization for MRSA and MSSA?

A

the nares

45
Q

LPS in E.coli causes what two diseases and what is the mechanism of action

A

causes pneumonia and neonatal meningitis;

LPS activates macrophages which leads to widespread release of IL-1, IL-6 and TNF-alpha

46
Q

95% of cases of gas gangrene are due to what organism?

how is it contracted and what else does it cause?

A

Clostridium perfringens;
found in soil;
also causes transient watery diarrhea

47
Q

what are the two main components of the H. flu type b vaccine

A

PRP (polyribose-ribitol-phosphate) from Hib capsule conjugated to either diptheria or tetanus toxin

48
Q

what is cold agglutinins and what conditions can it indicate

A

cold agglutinins are antibodies that cause RBC agglutination at cold temperatures;
they can be seen in infection with Mycoplasma pneumoniae and EBV or in cases of hematologic malignancy

49
Q

mucicarmine stain is used to detect which pathogen

A

the mucicarmine-rich polysaccharide capsule of cryptococcus neoformans appears red on mucicarmine stain

50
Q

how can recurrence of genital herpes (HSV-2) be prevented

A

daily valacyclovir, acyclovir or famciclovir

51
Q

in the U.S. how is Hep A virus commonly contracted

A

contaminated shellfish

52
Q

facial pain and headache in a patient with DKA is suggestive of….?
how is it diagnosed?

A

mucormycosis (Mucor, Rhizopus or Absidia);

diagnosed by mucosal biopsy

53
Q

where is the primary focus of cryptococcal infection usually located

A

in the lungs

54
Q

what virus-related malignancy are HIV patients at increased risk for

A

EBV-associated diffuse B-cell non-Hodgkin’s lymphoma (note: 90% of people have latent EBV)

55
Q

what are Koplik spots and what disease do they suggest?

what symptom usually follows 1-2 days later?

A

small whitish, bluish or grayish spots on the buccal mucosa near the molars;
Koplik spots are pathognemonic of rubeola (measles);
a maculopapular rash will develop in 1-2 days

56
Q

what is the classic triad of congenital toxoplasmosis

A

hydrocephalus, intracranial calcifications and chorioretinitis

57
Q

what is the main toxin of C. perfringens and what does it do

A

lecithinase, also known as phospholipase C or alpha toxin;

it breaks down phospholipids

58
Q

what is the most common cause of Candida vaginitis

A

antibiotic use

59
Q

name a non-infective envelope glycoprotein of a hepatitis-causing virus that forms spheres and tubules 22nm in diameter

A

HBsAg

60
Q

how does M. pneumoniae cause anemia

A

cold agglutinins are antibodies that cross-react between the bacteria and RBCs;
they bind RBCs and can cause hemolysis

61
Q

what is ecthyma gangrenosum; its associated pathogen; and the virulence factors that mediate this presentation

A 
a cutaneous necrotic disease presenting with dots of purpuric/necrotic lesions on the skin;
P. aeruginosa;
exotoxin A (inhibits protein synthesis), phospholipase C (destroys membranes), elastase, pyocyanin (generates ROS)
62
Q

is HAV infection in children more commonly icteric or anicteric

A

anicteric; in children HAV is commonly subclinical or asymptomatic

63
Q

which HIV structural gene is glycosylated and then cleaved to produce gp120 and gp41

A

env

64
Q

what is cord factor and what does it correlate with

A

cord factor is a mycoside (composed of mycolic acids) found in virulent strains of Mycobacterium;
correlates with virulence because it inhibits neutrophils, destroys mitochondria and induces release of TNF

65
Q

which virus(es) obtain(s) its envelope from the host nuclear membrane instead of the host plasma membrane

A

herpesviruses (1-8)

66
Q

most common cause of viral meningitis in children

A

enteroviruses (poliovirus, echovirus, coxsakievirus, enterovirus)

67
Q

explain the acid fast stain

A

carbolfuschin (an aniline dye) is used to stain mycolic acid red; then hydrochloric acid and alcohol is added to decolorize (dissolve outer cell membranes); mycolic acids prevents decolorization; methylene blue is added after as a counterstain; red= acid fast (has mycolic acid), blue= not acid fast

68
Q

which bacteria are acid-fast

A

mycobacterium and nocardia

69
Q

what is the causative bacterium and characteristics of chancroid

A

caused by haemophilus ducreyi;

deep, painful ulcers with gray/yellow base

70
Q

Donovan bodies (deeply staining gram-negative intracytoplasmic cysts) are seen in what disease and with what pathogen?

A

donovanosis aka granuloma inguinale;

Klebsiella inguinale

71
Q

list 3 unique facts about L. monocytogenes with respect to culture

A

can be cultured at 4 degrees Celcius
shows tumbling motility at 22 degrees Celcius
has a narrow zone of beta-hemolysis on blood agar

72
Q

how is M. leprae transmitted and what are the symptoms of the two forms

A

transmitted via respiratory droplets; armadillo reservoir
lepromatous form= more severe, lion facies, hypopigmented plaques, focal sensory paresis and loss of sensation, testicular destruction, blindness
tuberculoid form=self-limited due to cell-mediated response; hypopigmented plaque with diminished sensation

73
Q

why must HDV coinfect with HBV

A

HDV needs the viral coat of HBV (HBsAg) in order to infect hepatocytes

74
Q

which bacterial toxins increase intracellular cAMP

A

ETEC heat labile toxin, B. cereus heat labile enterotoxin, B. anthracis edema factor, cholera toxin, C. jejuni enterotoxin, pertussis toxin

75
Q

list the three things needed to treat diptheria (in order of most important to least)

A
  1. antitoxin (provides passive immunity, but doesn’t affect toxins that have already reached cardiac and CNS)
  2. erythromycin or azithromycin
  3. DPT vaccine
76
Q

a patient with defective NADPH oxidase has what disease?

what pathogens is the patient easily infected with?

A

chronic granulomatous disease;

infected by catalse positive organisms: pseudomonas cepacia, staph aureus, serratia marcecens, nocardia, aspergillus

77
Q

what two viruses causes maculopapular rashes that start at the head and spread downward;
which is more often associated with postauricular LAD

A

rubeola (measles) and rubella (German measles);

rubella is more associated with postauricular LAD

78
Q

which toxin acts via the same mechanism of action as edema factor

A

adenylate cyclase toxin of Bordatella pertusis also acts as a calmodulin-dependent adenylate cyclase
(other toxins that increase cAMP: cholera toxin and labile toxin of ETEC permanently activate Gs; pertussis toxin inactivates Gi)

79
Q

this virus causes self-limited hepatitis, but has a high rate of mortality in pregnant women

A

hepatitis E virus; a hepevirus

80
Q

pharyngitis with pharyngeal exudates, cervical lymphadenopathy and myocarditis suggests what pathogen

A

Corynebacterium diptheriae

81
Q

what does the HIV protein gag encode

A

nucleocapsid proteins p24 and p7

82
Q

list the most common causes of post-viral bacterial PNA in order

A

most common: S. pneumo
then S. aureus
then H. flu

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