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Step 1 (Steffanie) > Gram + Micro > Flashcards

Gram + Micro Flashcards

1
Q

Alpha hemolytic bacteria

A 
Streptococcus pneumoniae
Viridans streptococci (S. mutans, S. mitis)
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2
Q

Beta hemolytic bacteria

A 
Staphylococcus aureus
Streptococcus pyogenes (group A strep)
Streptococcus agalactiae (group B strep)
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3
Q

Gram +, beta hemolytic, catalase +, coagulase + cocci in clusters

A

Staphylococcus aureus

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4
Q

Protein A

A

Staph aureus. Binds Fc-IgG, inhibiting complement activation and phagocytosis

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5
Q

TSST-1

A

Superantigen that binds to MHC II and T cell receptor, resulting in polyclonal T-cell activation

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6
Q

Staph aureus food poisoning

A

Due to ingestion of preformed toxin (2-6 hr)

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7
Q

Diseases caused by staph aureus

A

Inflammatory disease - skin infections, pneumonia (often after influenza), organ abscesses, endocarditis, septic arthritis, osteomyelitis.
Toxin mediated disease - toxic shock syndrome, scalded skin syndrome, rapid onset food poisoning.
MRSA

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8
Q

Gram +, catalase +, coagulase -, urease + cocci in clusters. Novobiocin sensitive. Does not ferment mannitol.

A

Staphylococcus epidermidis

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9
Q

Gram +, catalase +, coagulase -, urease + cocci in clusters. Novobiocin resistant.

A

Staphylococcus saprophyticus

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10
Q

Gram +, catalase -, alpha hemolytic, lancet shaped diplococci. Encapsulated. IgA protease. Optochin sensitive

A

Streptococcus pneumonia

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11
Q

Strep pneumo is the most common cause of which conditions?

A

Meningitis
Otitis media (in children)
Pneumonia
Sinusitis

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12
Q

Gram +, catalase -, alpha hemolytic cocci. Resistant to optochin.

A

Viridans group streptococci

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13
Q

Where are viridans group streptococci located? What can they cause?

A

Normal flora of the oropharynx. Streptococcus mutans and S mitis cause dental caries. S. sanguinis causes subacute bacterial endocarditis.

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14
Q

Gram +, catalase -, beta hemolytic cocci in chains. Bacitracin sensitive. PYR +.

A

Streptococcus pyogenes (group A streptococci)

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15
Q

What kind of infections are caused by group A strep?

A

Pyogenic - pharyngitis, cellulitis, impetigo, erysipelas
Toxigenic - scarlet fever, toxic shock-like syndrome, necrotizing fasciitis
Immunologic - rheumatic fever, glomerulonephritis

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16
Q

Virulence factors for group A strep

A

Hyaluronic acid capsule and M protein inhibit phagocytosis

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17
Q

Blanching, sandpaper like body rash, strawberry tongue, and circumoral pallor in setting of group A strep pharyngitis (Erythrogenic toxin +)

A

Scarlet fever

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18
Q

Gram + cocci, beta hemolytic, bacitracin resistant. Produces CAMP factor, which enlarges the area of hemolysis by S. aureus. Hippurate test +. PYR -

A

Streptococcus agalactiae (group B strep)

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19
Q

What infections does group B strep cause?

A

Colonizes vagina. Causes pneumonia, meningitis, and sepsis, mainly in babies

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20
Q

When are pregnant women screen for group B strep? What is done if they are positive?

A

Screen at 35-37 weeks gestation. Pts with + culture receive intrapartum penicillin prophylaxis

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21
Q

Gram + cocci, catalase -, no hemolysis, does not grow in 6.5% NaCl

A

Streptococcus bovis

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22
Q

S. bovis is associated with?

A

Colon cancer

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23
Q

Gram + cocci, catalase -, grows in 6.5% NaCl, PYR+, variable hemolysis

A

Enterococci

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24
Q

What infections do enterococci cause?

A

Normal colonic flora. Penicillin G resistant and cause UTI, biliary tract infections, and subacute endocarditis (following GI/GU procedures). VRE are an important cause of nosocomial infection

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25
Q

Gram + spore forming rod. Produces anthrax toxin. Aerobic

A

Bacillus anthracis

26
Q

Only bacterium with a polypeptide capsule (contains D-glutamate)

A

Bacillus anthracis

27
Q

Bacillus cereus

A

Causes food poisoning. Emetic type usually seen with rice and pasta, nausea and vomiting within 1-5 hr, caused by cereulide (preformed toxin). Diarrheal type - watery, nonbloody diarrhea and GI pain within 8-18 hrs.

28
Q

Gram + facultative intracellular rod. Aerobic.

A

Listeria monocytogenes

29
Q

How is listeria acquired

A

Ingestion of unpasteurized dairy products and cold deli meats, via transplacental transmission, or by vaginal transmission during birth

30
Q

What conditions can listeria cause?

A

Amnionitis, septicemia, and spontaneous abortion in pregnant women; granulomatosis infantiseptica; neonatal meningitis; meningitis in immunocompromised; mild, self limited gastroenteiritis in healthy individuals

31
Q

How is infection with listeria treated?

A

Ampicillin

32
Q

Gram +, spore forming, obligate anaerobic rods

A

Clostridia

33
Q

Tetanospasmin

A

An exotoxin causing tetanus

34
Q

Tetanus toxin mechanism

A

Protease that cleaves SNARE proteins for neurotransmitters. Blocks release of inhibitory neurotransmitters, GABA and glycine, from Renshaw cells in spinal cord

35
Q

Spastic paralysis, trismus, risus sardonicus, opisthotonus

A

Tetanus

36
Q

How is tetanus treated?

A

Antitoxin +/- vaccine booster, antibiotics, diazepam (for muscle spasms), and wound debridement

37
Q

Heat labile toxin that inhibits ACh release at the neuromuscular junction

A

C botulinum

38
Q

Diplopia, dysarthria, dysphagia, dyspnea

A

Botulism

39
Q

alpha toxin

A

Lecithinase, a phospholipase. Toxin produced by C perfringens that can cause myonecrosis and hemolysis.

40
Q

Toxins produced by C difficile

A

Toxin A, an enterotoxin, binds to brush border of gut and alters fluid secretion. Toxin B, a cytotoxin, disrupts cytoskeleton via actin depolymerization. Both toxins lead to diarrhea and pseudomembranous colitis.

41
Q

Which antibiotics commonly cause C difficile?

A

Clindamycin or ampicillin

42
Q

How is C difficile treated?

A

Metronidazole or oral vancomycin

43
Q

Gram + rod; transmitted via respiratory droplets

A

Corynebacterium diphtheriae

44
Q

How does C. diphtheriae cause diphtheria

A

Via exotoxin encoded by beta-prophage. Inhibits protein synthesis via ADP-ribosylation of EF-2.

45
Q

Symptoms of diphtheria

A

Pseudomembranous pharnygitis, with lymphadenopathy, myocarditis, and arrhytmias

46
Q

Gram + long branching filaments, weakly acid fast, aerobe

A

Nocardia

47
Q

What does nocardia cause?

A

Pulmonary infections in immunocompromised; cutaneous infections after trauma in immunocompetent; can spread to CNS

48
Q

How is infection with Nocardia treated?

A

Sulfonimides (TMP-SMX)

49
Q

Where is Nocardia found?

A

Soil

50
Q

Gram + long branching filaments, anaerobe, not acid fast

A

Actinomyces

51
Q

Where is Actinomyces found?

A

Normal oral, reproductive, and GI flora

52
Q

What can Actinomyces cause?

A

Oral/facial abscesses that drain through sinus tracts; often associated with dental caries/extraction and other maxillofacial trauma. Can cause PID with IUDs

53
Q

How is Actinomyces treated?

A

Penicillin

54
Q

Mycobacterium avium

A

Causes disseminated, non-TB disease in AIDS. Often resistant to multiple drugs

55
Q

Prophylaxis for M avium

A

Azithromycin when CD4+ count <50 cells/mm3

56
Q

Mycobacteria scrofulaceum

A

Cervical lymphadenitis in children

57
Q

Mycobacteria marinum

A

Hand infection in aquarium handlers

58
Q

Cord factor

A

Virulence factor in M tuberculosis strains; activates macrophages (promoting granuloma formation) and induces release of TNF-alpha

59
Q

Sulfatides

A

Surface glycolipids. Inhibit phagolysosomal fusion. Present in M tuberculosis

60
Q

Yellow sulfur granules

A

Actinomyces

Step 1 (Steffanie) (21 decks)

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