Brainscape's Knowledge GenomeTM

Browse over 1 million classes created by top students, professors, publishers, and experts.


See full index

Microbiology > Clinical Final Study Guide > Flashcards

Clinical Final Study Guide Flashcards

You may prefer our related Brainscape-certified flashcards:
Biology 101 flashcards
1
Q

When is the best time to collect stool samples and why is refrigeration a poor method of preservation?

A

early in the day; temperature-sensitive organisms such as Shigella will die off, and any trophs present in the stool will begin to lyse once the specimen cools

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
2
Q

What should be done with a sputum sample if it cannot be cultured immediately?

A

refrigerate it

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
3
Q

How are genital swabs handled?

A

they require special collection swabs if their transport to the lab is delayed more than a few minutes; they can also be cultured at the bedside and incubated in the proper environment until they can be taken to the lab

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
4
Q

What special considerations should be taken when collecting wound swabs?

A

take care not to contaminate with normal skin flora, and be sure to collect two separate swabs (one for the cultures and one for the smear)

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
5
Q

What test differentiates S. aureus from non-pathogenic staphylococci?

A

coagulase test (S. aureus is +)

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
6
Q

What is the principle of the catalase test?

A

Catalase is an enzyme produced by microorganisms living in oxygenated environments to neutralize toxic forms of oxygen metabolites - mediates the breakdown of H2O2 into water and oxygen gas. Small inoculums of bacterial isolates are mixed with H2O2 solution; the production of bubbles indicates the organism is catalase +.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
7
Q

What test is use to distinguish coliform bacteria from the enteric pathogens?

A

lactose fermentation (coliforms are non-fermenters)

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
8
Q

How can Listeria monocytogenes be differentiated from Corynebacterium species?

A

motility (Corynebacterium is non-motile); sugar fermentation (Listeria is glucose/lactose/sucrose +, Corynebacterium is glucose/maltose +); nitrate reduction (Listeria does not reduce nitrates)

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
9
Q

How is alpha streptococci differentiated from S. pneumoniae?

A

optochin test (S. pneumoniae is sensitive)

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
10
Q

What agar is used for the Kirby-Bauer sensitivity test?

A

Mueller-Hinton

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
11
Q

Which enteric pathogen would be least likely to survive if the stool is left at room temperature for an extended period of time, or if it is refrigerated?

A

Shigella

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
12
Q

What organisms are known to cause food poisoning/food infections?

A

Salmonella, norovirus, Campylobacter, E. coli, Listeria, Clostridium perfringens

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
13
Q

Which organism is a Gram=, motile, oxidase+ rod with a grape-like odor?

A

Pseudomonas aeruginosa

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
14
Q

Which genus contains chromogenic, Gram= motile rods which have been implicated in septicemia, pulmonary infections, and UTIs?

A

Escherichia

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
15
Q

What is the most common organism in the human intestine?

A

Bacteroides

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
16
Q

Which genus and species is best cultured in an alkaline peptone medium and causes a severe type of diarrhea producing “rice-water” stools?

A

Vibrio cholera

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
17
Q

To which Lancefield group do most human pathogens that are beta-hemolytic streptococci belong?

A

Group A

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
18
Q

How is Enterobacter differentiated from Klebsiella?

A

Klebsiella is non-motile; Enterobacter is motile

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
19
Q

How is the TSI test interpreted?

A

yellow color means acid, purple color means alkaline, blackening indicates H2S production, and bubbles indicate gas production; A/A (glucose, lactose, and sucrose fermentation), K/A (glucose fermenter only), K/K (non-fermenter)

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
20
Q

What are the characteristics of a Gram+ cell wall?

A

several layers of peptidoglycan, which forms a thick, rigid structure; contains teichoic acid and lipteichoic acid (unique to Gram+); resistant to decolorization in Gram staining

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
21
Q

What are the characteristics of a Gram= cell wall?

A

much thinner peptidoglycan layer, and a unique outer membrane of proteins, lipids, and lipopolysaccharides (LPS); LPS has three regions - antigenic O-specific polysaccharide, core polysaccharide, and inner lipid A (exotoxin); exotoxin produces the fever and shock conditions in Gram= infections; does not contain teichoic acid and is more susceptible to mechanical breakdown

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
22
Q

The “satellite phenomenon” indicates that staphylococci produces which factor?

A

Factor V (not a Roman numeral)

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
23
Q

What is beta-lactamase?

A

enzyme produced by many species of bacteria that disrupts the 4-membered beta-lactam ring of penicillin and cephalosporin groups of antibiotics, detroying their antimicrobial activity

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
24
Q

What sugar is fermented by all Enterobacteriaceae?

A

glucose

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
25
Q

Meningitis due to Haemophilus influenzae is most common in what age group?

A

infants and young children

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
26
Q

Which genera of Enterobacteriaceae are non-motile?

A

Klebsiella

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
27
Q

Which genera of Enterobacteriaceae are resistant to many antibiotics and are frequently found in nosicomial infections?

A

Klebsiella

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
28
Q

Which organism is frequently isolated from dog or cat bites?

A

Pasteurella multocida

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
29
Q

From what type of specimen are members of the genus Lactobacillus isolated?

A

urine (it is normal in the GI tract and the vagina)

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
30
Q

How is Campylobacter identified in the laboratory?

A

grows best on blood agar or other enriched media; requires decreased oxygen and increased (10%) CO2; Gram=, but stain weakly with traditional methods; “bat wing” or “seagull” morphology; motile by means of single polar flagella

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
31
Q

Why are antibiotics added to modified Thayer-Martin media?

A

prevents the overgrowth of Gram+ bacteria, and Gram= bacteria and yeast OTHER than N. gonorrhoeae and N. meningitidis

32
Q

What are facultative organisms?

A

organisms that can grow with or without the presence of oxygen

33
Q

What effect would the omission of iodine have on a Gram stain?

A

would eliminate the attachment point for the primary stain, so Gram+ organisms would decolorize more easily and the stain would be inaccurate

34
Q

Which organisms can be normal in the upper respiratory tract?

A

staphylococci, Corynebacteria, streptococci, Neisseria, certain Gram= rods and cocci

35
Q

What sterilization method is the most effective and useful for the clinical lab?

A

autoclave

36
Q

Which body fluid is often cultured in an effort to trace Salmonella typhi carriers?

A

urine or bile

37
Q

What is the appearance of an encapsulated organism on blood agar and what effect does the capsule have on an organism’s virulence?

A

large, grey mucoid colonies; increases the virulence

38
Q

What is the principle of the decarboxylase test?

A

special broth tests for the production of the enzyme decarboxylase, which removes the carboxyl group from an amino acid (typically one of either arginine, lysine, or ornithine); if the media does not change color or turns yellow, the test is = (dextrose fermentation); purple color change is +; used to differentiate Enterobacteriaceae

39
Q

What terms are used to describe the morphology of members of the Corynebacterium genus?

A

“picket fence” or “Chinese letters”

40
Q

What are the characteristics of bacterial spores?

A

protective, dehydrated, dormant state resistant to drying, heat, chemical disinfectants, and radiation; germinates when environment is favorable again; NOT reproductive

41
Q

What are the biochemical characteristics of E. coli?

A

A/A on TS, citrate =, indole +, lysine and ornithine decarboxylase +, motility +, urea =

42
Q

What is the colonial morphology and pathogenicity of K. pneumoniae?

A

large, mucoid, pink, stringy (on Mac); causative agent of bronchial pneumonia (Friedlander’s pneumonia or Friedlander’s Bacillus); can be found in the oropharynx of 1-6% normal patients; infections more common in patients with underlying debilitating conditions (diabetes, alcoholism, and COPD); can be very destructive (extensive hemorrhaging and necrosis, thick mucoid sputum production); also causes enteritis and meningitis (in infants), UTI, and sepsis; isolates are usually resistant to ampicillin and penicillin

43
Q

What screening test is used in the laboratory to differentiate E. coli O157:H7 from normal strains?

A

culturing on special Mac agar that contains 1% D-sorbitol instead of lactose - O157:H7 is sorbitol = and will appear colorless

44
Q

What test can be used to differentiate the two main species of Proteus?

A

indole (P. mirabilis =, P. vulgaris +) and citrate (opposite of indole)

45
Q

Which species might be considered contaminants if they were isolated from a blood culture?

A

normal skin flora, such as S. aureus - confirm with a redraw

46
Q

If two organisms are to be used as quality controls, should their reactions be the same or different?

A

different

47
Q

What are the designations for the cell wall, flagellar, and capsular antigens in bacteria?

A

flagellar (H), capsule (K or Vi), cell wall (O)

48
Q

Which bacterial antigen can mask the cell wall antigen in serological typing?

A

K/Vi

49
Q

On what type of laboratory media should suspected anaerobic organisms be cultured?

A

anaerobic SBA plates, or other suitable media that is plated and incubated in an anaerobic environment

50
Q

What is the Gram stain morphology of Bacteroides and Fusobacterium?

A

Bacteroides (Gram =, non-endospore-forming bacilli); Fusobacterium (Gram =, similar to Bacteroides, individual rods have pointed ends)

51
Q

What types of specimens are suitable for anaerobic culture?

A

wounds or abscesses; tissue and biopsy; trans-tracheal aspirate; blood; body fluids from normally sterile areas; suprapubic urine; aseptically collected uterine specimens

52
Q

What specimens are unsuitable for anaerobic culture, and why?

A

non-trans-tracheal respiratory cultures; routine urines; fecal specimens; vaginal specimens (anaerobes are normal in all of these except urines, which cannot prevent being exposed to air)

53
Q

What is the Gram stain morphology of N. meningitidis and what sugars are utilized by this organism?

A

Gram =, coffee-bean shaped diplococci; dextrose and maltose +

54
Q

What stains are used for members of the Mycobacterium genus?

A

acid-fast or fluorochrome

55
Q

Why is N-acetly-L-cysteine (NALC) the most common agent used for sputum concentration for AFE cultures?

A

NALC acts as a mucolytic agent that breaks up the specimen to enhance organism recovery

56
Q

What is the colonial morphology of M. tuberculosis on Lowenstein-Jensen medium?

A

buff in color, flat, spreading, friable with rough appearance; may show the “string of pearls” effect

57
Q

What can be used as a clearing agent to remove protein material from a mycology specimen?

A

KOH prep

58
Q

What is the procedure of choice for demonstrating Cryptococcus in CSF?

A

India ink prep

59
Q

What is the single best medium for the primary isolation of fungi?

A

Sabouraud’s

60
Q

What is the (1) macroscopic and (2) microscopic appearance of genus Aspergillis?

A

(1) varies; A. fumigatis is flat, white, and filamentous with blue-green powdery surface and a colorless reverse; A. niger produces pitch black spores; A. flavus produces yellow-green spores so numerous they weigh down the mycelium. (2) can vary, but all species have branching septate hyphae, with conidia on terminal conidiophores with swellings or vesicles that have flask-like philiades (sterigmata)

61
Q

What is the (1) macroscopic and (2) microscopic appearance of genus Penicillium?

A

(1) forward is grey-green; growth appears granular due to the number of spores and may have radial folds; no reverse pigment. (2) conidiophores from septate hyphae, with phialides that bear conidia; “skeleton hand” appearance due to no vesicles

62
Q

What is the (1) macroscopic and (2) microscopic appearance of genus Rhizopus?

A

(1) white and fluffy with long aerial mycelium, black spores (“salt and pepper”). (2) hyaline, broad, branching, non-septate hyphae; rhizoids where sporangiophores come off the mycelium; spores borne in cellophane-like sporangium

63
Q

What stage in the development of a parasite is best demonstrated by a permanent stained smear?

A

trophs and cysts

64
Q

For which organisms is the sedimentation method of stool concentration best?

A

trematode ova, infertile Ascaris, D. latum ova, Strongyloides larvae

65
Q

For which organisms is the flotation method of stool concentration best?

A

protozoan cysts, cestode ova (not D. latum), nematode ova (not Ascaris)

66
Q

What is the appearance of the cyst of Entamoeba histolytica?

A

can have more than one nucleus (max. 4), with evenly distributed peripheral chromatin and small central karyosomes; will see cigar-shaped chromotoidal bars with rounded ends

67
Q

What is the microscopic appearance of the Giardia lamblia troph?

A

it is the only bilaterally symmetrical troph; pear-shaped with 2 nuclei; ventral sucking disc; spoon-shaped from the side; vertical axostlye; parabasal body with 4 pairs of flagella; “monkey” or “smiley” face appearance; “falling leaf” motility

68
Q

What are the distinctive features of Plasmodium vivax?

A

chills and fever every third day (benign tertian); red cells appear enlarged (infects reticulocytes), amoeboid extensions of the cytoplasm as it grows; Shuffner’s dots; 16-18 merozoites

69
Q

What are the distinctive features of Plasmodium ovale?

A

also benign tertian; similar to P. vivax, with irregular or fimbriated red cell edges; only around 8 merozoites

70
Q

What are the distinctive features of Plasmodium malariae?

A

chills and fever every fourth day (quartian malaria); early ring form resembles P. vivax, but it is smaller and more compact, less irregular, and deeper blue; band forms; red cells are the same size or smaller than non-infected red cells; no Shuffner’s dots; 8-10 merozoites (“daisy head” or “segmenter” formation)

71
Q

What are the distinctive features of Plasmodium falciparum?

A

fever and chills every 36-48 hours (malignant tertian); only ring forms, trophs, and gametocytes seen in the peripheral blood; can see more than one ring form in a single infected red cell (multi-infection); applique/accolade forms; split-ring forms with double chromatin dots are frequent; immature gametocytes are elliptical, maturing into a banana or crescent shape; Mauer’s dots

72
Q

What are the biochemical reactions of S. epidermidis?

A

catalase +; reduces nitrates to nitrites; glucose +, mannitol =; coagulase =; salt tolerant; DNase =; produces penicillinase; no toxic metabolites

73
Q

Which genera are oxidase +?

A

Pseudomonaceae, Neisseria, Moraxella, Helicobacter pylori, Vibrio cholera, Campylobacter jejuni, Legionella pneumophilia

74
Q

Which growth factors are required by the various species of Haemophilus?

A

X and V (not Roman numerals)

75
Q

Which fungi are dimorphic?

A

Histoplasma capsulatum, Blastomyces dermatitidis, Coccidioides immitis, Paracoccidioides braziliensis, Sporothrix schenckii

Microbiology (3 decks)

Brainscape helps you reach your goals faster, through stronger study habits.
© 2024 Bold Learning Solutions. Terms and Conditions