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Microbiology > LAB > Flashcards

LAB Flashcards

1
Q

Staphylococcus
gram stain/shape:
in clinical specimens generally appear:
catalase:

A

stain shape: GPC
in clinical specimens generally appear: in clusters (or short chains, pairs and singles)
catalase: positive

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2
Q

the most useful way of distinguishing S. aureus from other Staph?

A

coagulase positive test (after the catalase test distinguishes it from other GPC)

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3
Q

Coagulase negative Staph

A

S. saprophyticus and S. epidermidis

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4
Q

S. aureus cases what clinical manifestations

A

skin abcesses to pneumonia and endocarditis

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5
Q

S. epidermidis is often caused by

A

a cause of baceremia in neutrophenic patients relating to indwelling catheters, shunts and prosthetic devices

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6
Q

a common cause of UTIs in young, sexually active women?

A

S. saprophyticus

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7
Q

how do you distinguish between S. saprophyticus and S. epidermitis (both GPC, Cat +, coag negative)

A

Novobiocin:
S. epidermidis is “Se”nsitive
S. Saprophyticis is resistant

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8
Q

Micrococcus

A

species closely related to Staph that at cat + and coag neg. they are rarely pathogenic, but like S. epidermidis they can infect prosthetic hardware/be difficult to treat in this setting

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9
Q

All Strep and Enteroccoci are
Gram stain:
catalase:
in clinical specimens and fluid culture they grow in:

A

GPC
cat neg
grow in straps or pairs

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10
Q

S. pneumoniae (pneumococcus) is a frequent cause of:

A

pneumonia, meningitis and sepsis

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11
Q

S pyogenes, group A strep, is a frequent cause of

A

pharyngitis, cellulitis, and rheumatic fever

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12
Q

S. agalactiae (grp B strep) is a common cause of

A

neonatal meningitis

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13
Q

Enteroccoci are normally found in the

A

colon

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14
Q

unlike Strep, Enterococci can grow in…

A

hile bile, high salt envts (strep only grows in high bile envt)

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15
Q

Enterococcal infections are often associated with

A

UTIs and GI disorders

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16
Q

Haemophilus
size:
Gram stain/shape:

A

Haemophilus
size: small
Gram stain/shape: pleomorthic gram-neg rods

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17
Q

how can you distinguish between different Haemophilus species?

A

the nutrient growth factors required for them to grow

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18
Q

X factor

A

hemin- comes from blood or its constituents and it’s presence is required for the growth of some Haemophilus and not others

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19
Q

V factor

A

NAD- comes from blood or its constituents and it’s presence is required for the growth of some Haemophilus and not others

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20
Q

does H influenzae, the most common Haemophilus pathogen, require factor V, factor X or both for growth? what about the often isolated, but rarely pathogenic H. Parainfluenzae?

A

H. Influenzae: Both

H. Parainfluenzae: requires only V

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21
Q

Neisseria
Gram/shape:
aerobic/anaerobic/other:
oxidase:

A

Gram/shape: Gram neg diplococci
aerobic/anaerobic/other: strict aerobes
oxidase: positive

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22
Q

Nisseria species most difficult to grow. Why?

A

N. Gonorrhoea, because it thrives in a limited T range and needs ample moisture, CO2 and rich non-acidic medium

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23
Q

N mengitidis requires what to grow:

A

rich media and extra CO2

24
Q

Moraxella:

Gram/shape:

A

like Nisserai, they’re:
Gram/shape: Gram neg diplococci
aerobic/anaerobic/other: strict aerobes
oxidase: positive

25
Q

Moraxella Catarrhalis, once considered a nonpathogenic Neisseria and a part of normal mouth flora, now appears to be an occasional cause of:

A

sinusitis and other serious disease

26
Q

how are Neisseria and Moraxella distinguished given that they’re both gram neg diploccoci, strict aerobes that are oxidase positive?

A

sugar fermentation tests

27
Q

Bacitracin is used to distinguish between what and what?

A 
Beta-hemolytic Strep (Group A vs Group B)
B-Bras
Bacitracin
B-strep (agalaciae)
Resistant
A-strep (pyogenes)
Sensitive
28
Q

most bacteria that can grow aerobically and have a high O2 tolerance posses what in contrast to streptococci or enterococci which are facultative anaerobes that are incapable of using oxygen metabolically

A

catalase- a heme enzyme that decomposes hydrogen peroxide into H2O and O2

29
Q

S. aureus colonies are the only Staph that usually look…

A

yellow or beige (as the name aureus implies)

30
Q

How do these look different on an blood agar
Alpha-hemolysis:
beta hemolysis:
Gamma-hemolysis

A

Alpha-hemolysis: green
beta hemolysis: clear
Gamma-hemolysis: the absence of any rxn on blood cells in the agar

31
Q

Optochin test

A

differentiates between S. pneumoniae (susceptible) from other alpha-hemolytic strep (resistant)

32
Q

oxidase test

A

put test species on a piece of bibulous paper, add a few drops of oxidase reagens, if the culture is oxidase positive, the dye will be oxidized and the colonies will turn pink to red to black

33
Q

Cystein tryptic agar (CTA) differentiates between Nisseria and Moraxella by

A

because it shows if you can produce acid from metabolizing glucose, maltose, sucrose and lactose. acid production is indicated by the presence of yellow

34
Q 
S. aureus:
cellular morphology:
colonial morphology:
hemolytic rxn:
catalase:
identifying tests:
A 
S. aureus:
cellular morphology: GPC in clusters
colonial morphology: creamy to yellow
hemolytic rxn: Beta
catalase: +
identifying tests: coagulase
35
Q 
S. epidermidis
cellular morphology:
colonial morphology:
hemolytic rxn:
catalase:
identifying tests:
A 
cellular morphology: GPC in clusters
colonial morphology: white
hemolytic rxn: none
catalase: +
identifying tests: coag neg, novobiocin sensitive
36
Q 
S. saprophyticus
cellular morphology:
colonial morphology:
hemolytic rxn:
catalase:
identifying tests:
A 
cellular morphology: white to yellow
colonial morphology: white to yellow
hemolytic rxn: none
catalase: +
identifying tests: coag neg, novobiacin resistant
37
Q 
S. pyogenes (Group A)
cellular morphology:
colonial morphology:
hemolytic rxn:
catalase:
identifying tests:
A

cellular morphology: gram + cocci in chains
colonial morphology: grayish to white translucent
hemolytic rxn: Beta
catalase: negative
identifying tests: bacitracin sensitive

38
Q 
Group B strep (agalactiae)
cellular morphology:
colonial morphology:
hemolytic rxn:
catalase:
identifying tests:
A

cellular morphology: gram + cocci in chains
colonial morphology: grayish to white translucent
hemolytic rxn: Beta
catalase: negative
identifying tests: bacitracin resistant

39
Q 
S. pneumoniae
cellular morphology:
colonial morphology:
hemolytic rxn:
catalase:
identifying tests:
A

S. pneumoniae
cellular morphology: gram + cocci in pairs
colonial morphology: grayish to white translucent
hemolytic rxn: alpha
catalase: negative
identifying tests: optochin sensitive (unlike all the other alpha hemolytic or viridans grp)

40
Q 
Non-hemolytic Strep and Enterococcus
cellular morphology:
colonial morphology:
hemolytic rxn:
catalase:
identifying tests:
A

cellular morphology: gram + cocci in chains
colonial morphology: grayish to white translucent
hemolytic rxn: non-hemolytic (gamma)
catalase: negative
identifying tests: bile esculin (+ for gamma strep and enterococcus) and high NaCL (positive growth for enterococcus but not group d strep)

41
Q 
H influenzae
cellular morphology:
colonial morphology:
hemolytic rxn:
catalase:
identifying tests:
A

H influenzae
cellular morphology: gram + coccobaccili, pleomorphic
colonial morphology: gray, translucent, small
hemolytic rxn: gamma
identifying tests: factor X (hemin) +, Factor V (NAD) +

42
Q 
H. haemolyticus
cellular morphology:
colonial morphology:
hemolytic rxn:
catalase:
identifying tests:
A

H. haemolyticus
cellular morphology: gram + coccobaccili, pleomorphic
colonial morphology: gray, translucent, small
hemolytic rxn: beta
identifying tests: factor X (hemin) +, Factor V (NAD) +

43
Q 
H. parainfluenzae
cellular morphology:
colonial morphology:
hemolytic rxn:
catalase:
identifying tests:
A

cellular morphology: gram + coccobaccili, pleomorphic
colonial morphology: gray, translucent, small
hemolytic rxn: gamma
identifying tests: factor X (hemin) -, Factor V (NAD) +

44
Q

what is the cause?
5 yo w/sore hroat, fever, swollen glands. Redness, edema and grayish white exudate

culture: GPC, beta hemolytic, bacitran sensitive

A

Grp A strep (pyogenes), which can also cause cellulitis and necrotizing fasciitis

45
Q

what is the cause:
elderly (79 yo) woman w/ chest pain, difficulty breathing, cough and fever

sputum culture: GPC in pairs, alpha hemolysis, optichin sensitive

A

S. pneumoniae

46
Q

what is the cause:
hospitalized pt with urinary catheter dvps a UTI

urine culture: GPC in chains, cat neg, bile +, NaCL +

A

Enterococcus

47
Q

what is the cause:
2 days post surgery, pt notices area around incision = red and swollen and extremely painful

culture cloudy fluid from wound: GPC in clusters, cat +, coag +

A

S aureus– common on skin and gets in via an encision

48
Q

what is the cause:
hospitalized pt with an IV catheter dvps a fever. Skin arnd IV entry site is red and swollen

culture from the tip of the catheter: GPC, cat +, coag -, novobiocin -

A

S. epidermidis– grows on biofilms on plastics

49
Q

what is the cause:
young, sexually active woman dvps abdo pain/dysuria (pain upon peeing)

urine culture: GPC, cat +, coag -, novobiocin resistant

A

S. saprophyticus

50
Q

what is the cause:
23 yo mas with dysuria and urethral discharge

discharge = cultured: gram neg diplococci, doesn’t ferment maltose, oxidase +

A

N. gonnhorhea– diplococci (“the clap”)

51
Q

what is the cause:
55 yo w/hist of rheumatic fever who presents with fever, malaise and splinter hemorrhage (sign of endocarditis)

culture: GPC, y-hemolytic, bile +, NaCl -

A

Grp D. strep

52
Q

what is the cause:
a bad sinus infection sends an 18 yo pt to doctor

culture: GP coccobacilli, gray, translucent, small culture, gamma hemolytic, required factor V and X

A

H. influenzae

53
Q

HMS student- upper respiratory infection

culture: Gram neg, no growth on blood agar, growth on chocolate agar, small gray and translucent, grows around factor V

A

H. parainfluenzae

54
Q

N gonorrhea is gram neg. diplococci, looks gray, white or yellowish, is y-hemolytic, is oxidase negative and metabolizes which sugars?

A

just glucose

55
Q

N meningitidis is gram neg. diplococci, looks gray, white or yellowish, is y-hemolytic, is oxidase negative and metabolizes which sugars?

A

glucose and maltose

56
Q

Moraxella is gram neg. diplococci, looks gray, white or yellowish, is y-hemolytic, is oxidase negative and metabolizes which sugars?

A

NONE!

Microbiology (11 decks)

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