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RMT AUG 2024 > MICRO EXAMS > Flashcards

MICRO EXAMS Flashcards

1
Q

A single ASO titer is considered to be moderately elevated if the titer is at least _____ Todd units in a child.

A

320 Todd Units

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2
Q

In addition to Enterococcus faecalis, which other streptococci will grow in 6.5% salt broth?

A

Group B streptococci

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3
Q

When streaking a throat culture on 5% sheep blood agar, stabbing the agar plate provides enhanced detection for:

A

Streptolysin O - subsurface hemolysis

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4
Q

Susceptibility testing performed on quality control organisms using a new media lot number yielded zone sizes that were too large for all antibiotics tested. The testing was repeated using media from a previously used lot number, and all zone sizes were acceptable. Which of the following best explains the unacceptable zone sizes?

A

The depth of the media was too thin

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5
Q

In a disk diffusion susceptibility test, which of the following can result if disks are placed on the inoculated media and left at room temperature for an hour before incubation?

A

Zones of larger diameter would result

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6
Q

Gram stain examination from a blood culture bottle shows dark blue, spherical organisms in clusters. Growth on sheep blood agar shows small, round, pale yellow colonies. Further tests should include:

A

Catalase production and coagulase test

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7
Q

Which of the following tests should be used to differentiate Staphylococcus aureus from Staphylococcus intermedius?

A

Acetoin

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8
Q

Streptolysin O:

A

Antigenic

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9
Q

Neufeld reaction Quellung capsular swelling replaced by

A

Molecular test

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10
Q

Tumbling motility is characteristic of:

A

Listeria

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11
Q

Peptococcus and Peptostreptococcus are both:

A

Anaerobic gram-positive cocci

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12
Q

Propionobacteria are:

A

Anaerobic gram-positive rods

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13
Q

Transgrow is a transport medium for:

A

Gonococci and meningococci

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14
Q

The unique chemical structure of the cell wall of Mycobacterium spp. is associated with the presence of:

A

N-glycolylmuramic acid and an increase in lipid content

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15
Q

The heat resistance of bacterial spores, such as those of Bacillus anthracis, is partly attributable to their dehydrated state and partly to the presence of large amounts of:

A

Calcium dipicolinate

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16
Q

The use of 0.1% fuchsin substituted for safranin in the Gram-stain procedure may enhance the visibility of the organisms:

A

Legionella

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17
Q

The Schaeffer–Fulton stain can be used for demonstration of:

A

Spores

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18
Q

The Schaeffer–Fulton stain can be used for demonstration of:

A

Spores

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19
Q

The Leifson stain can be used for demonstration of:

A

Flagella

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20
Q

Which statement correctly describes the mode of action of the antibiotic listed for modified Thayer-Martin medium?

A

Nystatin inhibits fungi and molds

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21
Q

Select the medium best suited for the recovery of Yersinia enterocolitica from a patient with gastroenteritis:

A

Cefsulodin–Irgasan–Novobiocin (CIN) agar

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22
Q

Which procedure is appropriate for culture of genital specimens in order to recover Chlamydia spp.?

A

Inoculate cycloheximide-treated McCoy cells

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23
Q

PYR test

A

pyrrolidonyl arylamidase

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24
Q

Substrate of PYR

A

L-pyrrolidonyl-B-naphthylamide

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25
Q

Skin test for Pneumococcal antibodies

A

Francis test

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26
Q

Assoc disease of S.bovis

A

Gastrointestinal malignancy

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27
Q

Special agar for nutritional variant streptococci

A

Agar with Cysteine or Pyridoxal Vitamin B6

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28
Q

Satelliting streptococci
Thiol requiring streptoco

A
  1. Strep adjacens
  2. Strep defectivus
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29
Q

Satellitism: dew drop
Staph streak test

A

H.influenzaw around S.aereus

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30
Q

Factor to convert immunoglobulin value from mg/dL to g/L:

A

0.01

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31
Q

Anaerobe

A

• 0-0% - O2
• 5-10% - CO2
• 5-10% - H2
• 80-90% - N2

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32
Q

Capnophilic

A

• O2 - 15%
• CO2 - 5-10%

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33
Q

Capnophilic

A

• O2 - 15%
• CO2 - 5-10%

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34
Q

Microaerophile

A

• O2 - 10%

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35
Q

Aerobic

A

• O2 - 21%
• CO2 - 0.03%

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36
Q

Seventy (70) % recirculated to the cabinet work area through HEPA; 30% balance can be exhausted through HEPA back into the room or to outside through a canopy unit:
*

A

BSC Class II: A1

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37
Q

Thirty (30) % recirculated, 70% exhausted. Exhaust cabinet air must pass through a dedicated duct to the outside through a HEPA filter:

A

BSC Class II: B1

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38
Q

CSF specimens must be transported in the laboratory:

A

Less than 15mins

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39
Q

Cerebrospinal fluid from a febrile 25-year-old man with possible meningitis is rushed to the laboratory for a stat Gram stain and culture. While performing the Gram stain, the technologist accidentally spills most of the specimen. The smear shows many neutrophils and no microorganisms. Since there is only enough CSF to inoculate one plate, the technologist should use a:

A

Chocolate agar plate: Enriched media such as chocolate agar has no inhibitory effects on bacterial growth and contains additional nutrients that support the growth of fastidious organisms such as H. influenzae and Neisseria.

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40
Q

A urine Gram stain shows gram-positive cocci in clusters. The organism tested catalase positive. To speciate this organism from culture, the technician should perform a coagulase test and a/an:

A

Novobiocin susceptibility: Between CoNs agad mga staph. S.aereus- Coag +
Novobio S - S.epid
Novobio R - S.sapro

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41
Q

Which of the following tests should be used to differentiate Staphylococcus aureus from Staphylococcus intermedius?

A

Acetoin: imvic

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42
Q

Streptolysin O:

A

Oxygen labile
Antigenic
Non surface

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43
Q

A vaginal/rectal swab is collected from a pregnant patient to screen for group B Streptococcus colonization. What is the best medium to use for specimen inoculation?

A

LIM broth (Todd-Hewitt broth with colistin and nalidixic acid): The swab(s) should be inoculated into a selective broth medium such as LIM broth (Todd-Hewitt broth with colistin and nalidixic acid). The use of vaginal/rectal swabs and selective broth medium greatly increases the recovery of GBS.

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44
Q

In addition to Enterococcus faecalis, which other streptococci will grow in 6.5% salt broth?

A

Group B streptococci

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45
Q

Xylose lysine deoxycholate (XLD) agar is a highly selective medium used for the recovery of which bacteria?

A

Enterobacteriaceae from gastrointestinal specimens:

XLD agar is selective for gram-negative coliforms because of a high concentration (0.25%) of deoxycholate, which inhibits gram-positive bacteria.

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46
Q

SITUATION: A group of elementary students became ill after eating undercooked ground beef prepared in the school cafeteria. The suspected pathogen, E. coli serotype 0157:H7, is usually recovered using which of the following media?

A

MacConkey agar with sorbitol

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47
Q

A positive Simmons citrate test is seen as a:

A

Blue color in the medium after 24 hours of incubation at 35°C

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48
Q

Which of the following reagents is added to detect the production of indole?

A

p-Dimethylaminobenzaldehyde

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49
Q

Fever, abdominal cramping, watery stools, and fluid and electrolyte loss preceded by bloody stools 2–3 days before is characteristic of shigellosis but may also result from infection with:

A

Campylobacter spp.

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50
Q

A liquid fecal specimen from a three-month-old infant is submitted for microbiological examination. In addition to culture on routine media for Salmonella and Shigella, this specimen should be routinely:

A

Examined for the presence of Campylobacter sp

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51
Q

Enterobacter sakazakii can best be differentiated from Enterobacter cloacae by which of the following characteristics?

A

Yellow pigmentation and negative sorbitol fermentation

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52
Q

Which single test best separates Klebsiella oxytoca from K. pneumoniae?

A

Indole

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53
Q

Three blood cultures taken from a 30-year-old cancer patient receiving chemotherapy and admitted with a urinary tract infection grew lactose-negative, motile, gram-negative rods prior to antibiotic therapy. Given the following biochemical reactions, which is most likely organism?

A

Proteus vulgaris

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54
Q

Which tests are most appropriate to differentiate between Pseudomonas aeruginosa and Pseudomonas putida?

A

Mannitol, nitrate reduction, growth at 42°C

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55
Q

Which Pseudomonas is usually associated with a lung infection related to cystic fibrosis?

A

P. aeruginosa

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56
Q

Which of the listed Pseudomonas spp. is associated with the following virulence factors: exotoxin A, endotoxins, proteolytic enzymes, antimicrobial resistance, and production of alginate?

A

P. aeruginosa

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57
Q

A blood culture bottle with macroscopic signs of growth is Gram stained and the technician notes small, curved gram-negative bacilli resembling “gull wings.” It is subcultured to blood and chocolate agar, and incubated aerobically and anaerobically. After 24 hours, no growth is apparent. The next step should be to:

A

Subculture the bottle, and incubate in microaerophilic conditions

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58
Q

A gastroenterologist submits a gastric biopsy from a patient with a peptic ulcer. To obtain presumptive evidence of Helicobacter pylori, a portion of the specimen should be added to which media?

A

Urea broth

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59
Q

Which group of tests best differentiates Helicobacter pylori from C. jejuni?

A

Urease, nitrate, and hippurate hydrolysis

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60
Q

Smooth gray colonies showing no hemolysis are recovered from an infected cat scratch on blood and chocolate agar but fail to grow on MacConkey agar. The organisms are gram-negative pleomorphic rods that are both catalase and oxidase positive and strongly indole positive. The most likely organism is:

A

Pasteurella spp.

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61
Q

Which of the following plates should be used in order to identify Haemophilus haemolyticus and Haemophilus parahaemolyticus?

A

Horse blood agar and Mueller–Hinton agar with X and V strips

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62
Q

Which Haemophilus species is difficult to isolate and recover from genital ulcers and swollen lymph nodes?

A

H ducreyi

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63
Q

A gram-negative, fastidious bacillus that has been isolated from air-conditioning towers:

A

Legionella pneumophila

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64
Q

“Chocolate cake” or “burnt chocolate” smell

A

Proteus spp.

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65
Q

Fruity or grapelike smell, corn tortilla-like odor:

A

Pseudomonas aeruginosa

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66
Q

Fruity or grapelike smell, corn tortilla-like odor:

A

Pseudomonas aeruginosa

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67
Q

Musty or mushroom odor:

A

Pasteurella multocida

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68
Q

Smell of ammonium cyanide (almond-like):

A

Chromobacterium violaceum

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69
Q

Oxidase and urease positive:

A

B. bronchiseptica

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70
Q

Oxidase negative, urease positive

A

B. parapertussis

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71
Q

Semisolid transport media such as Amies, Stuart, or Cary–Blair are suitable for the transport of swabs for culture of most pathogens except:

A

Specimens for culture of N. gonorrhoeae are best if plated immediately or transported in a medium containing activated charcoal to absorb inhibitory substances that hinder their recovery.

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72
Q

Putrescine is an alkaline amine product of which bacterial enzyme?

A

Ornithine

Putrescine is the amine product of the decarboxylation of ornithine.

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73
Q

Which of the following organisms are transmitted to animals and humans after a tick bite?

A

Ehrlichia and Anaplasma spp.

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74
Q

The manganous chloride–urea test is used for the identification of which organism?

A

Ureaplasma urealyticum

U. urealyticum is the only human mycoplasma that hydrolyzes urea. The manganous chloride–urea test utilizes manganous chloride (MnCl2) in the presence of urea. Urease produced by the organism hydrolyzes the urea to ammonia.

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75
Q

Which test is the most reliable for the detection of Mycoplasma pneumoniae in serum and for the confirmation of diagnosis?

A

EIA testing and direct antigen testing

Adults may fail to produce an IgM response especially in recurrent infections, so the best confirmatory approach is a combination of EIA and direct antigen testing.

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76
Q

Which organism typically produces “fried-egg” colonies on agar within 1–5 days of culture from a genital specimen?

A

Mycoplasma hominis

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77
Q

Primary atypical pneumonia is caused by:

A

Mycoplasma pneumoniae

A common cause of respiratory tract illness, M. pneumoniae, generally causes a self-limited infection (3–10 days) and usually does not require antibiotic therapy. M. pneumoniae can be cultured from the upper and lower respiratory tracts onto specially enriched (diphasic) media, but is most frequently diagnosed by the change in antibody titer from acute to convalescent serum using enzyme immunoassay or other serological methods.

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78
Q

Which is the test of choice for the confirmation of Chlamydia trachomatis infection in urine?

A

PCR is both sensitive and specific and may be performed on urine.

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79
Q

Which procedure is appropriate for culture of genital specimens in order to recover Chlamydia spp.?

A

Inoculate cycloheximide-treated McCoy cells

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80
Q

Routine laboratory testing for Treponema pallidum involves:

A

Serological analysis

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81
Q

The diagnostic method most commonly used for the identification of Lyme disease is:

A

Serology

Serological analysis using immunofluorescence or an enzyme immunoassay is the method of choice for diagnosis of Lyme disease.

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82
Q

Which of the following Mycobacterium spp. would be most likely to grow on a MacConkey agar plate?

A

M. chelonae–fortuitum complex

Mycobacteria growing on MacConkey agar are usually nonpathogens. M. chelonae and M. fortuitum are both nonpathogenic rapid growers that will grow on MacConkey agar (with no crystal violet) within 5 days.

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83
Q

Which of the following Mycobacterium species is diagnosed by means other than culture?

A

M. leprae

M. leprae and M. microti are different from all other mycobacteria because they cannot be cultured in vitro.

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84
Q

Which mycobacterium is associated with Crohn’s disease?

A

M. paratuberculosis

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85
Q

Which mycobacterium is associated with Crohn’s disease?

A

M. paratuberculosis

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86
Q

Which nonpathogenic Mycobacterium specie is isolated most often from clinical specimens and is called the “tapwater bacillus”?

A

M. gordonae

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87
Q

Which M. avium complex (MAC) organism is the most frequently isolated mycobacterium from AIDS patients?

A

M. avium

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88
Q

Which of the following Mycobacterium spp. is best differentiated by the rapid hydrolysis of Tween 80?

A

M kansaii

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89
Q

Growth inhibition by thiophene-2-carboxylichydrazide (T2H) is used to differentiate M. tuberculosis from which other Mycobacterium sp.:

A

M. bovis

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90
Q

Which organism, associated with tuberculosis in cattle, causes tuberculosis in humans, especially in regions where dairy farming is prevalent?

A

Mycobacterium bovis

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91
Q

All of the following Mycobacterium spp. produce the enzyme required to convert niacin to niacin ribonucleotide except:

A

M. tuberculosis

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92
Q

A gram-positive (gram-variable), beaded organism with delicate branching was recovered from the sputum of a 20-year-old patient with leukemia. The specimen produced orange, glabrous, waxy colonies on Middlebrook’s agar that showed partial acid-fast staining with the modified Kinyoun stain. What is the most likely identification?

A

Nocardia spp.

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93
Q

Establishing the pathogenicity of a microorganism isolated from a child’s throat and identified as Corynebacterium diphtheriae would depend upon:

A

A positive toxigenicity test

In order to determine if an isolate of Corynebacterium diphtheriae produces toxin, testing for the presence of diphtheria toxin must be performed using methods such as Elek test or PCR.

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94
Q

Methods other than packaged microsystems used to identify anaerobes include:

A

Gas–liquid chromatography (GLC)

Anaerobic bacteria can be identified by analysis of metabolic products using gas–liquid chromatography. Results are evaluated along with Gram staining characteristics, spore formation, and cellular morphology in order to make the identification.

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95
Q

Identification of Clostridium tetani is based upon:

A

Clinical findings

The culture and Gram stain of the puncture wound site usually does not produce any evidence of C. tetani. The diagnosis is usually based upon clinical findings, which are characterized by spastic muscle contractions, lockjaw, and backward arching of the back caused by muscle contraction.

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96
Q

Which spore type and location is found on Clostridium tetani?

A

Round, terminal spores

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97
Q

Which mechanism is responsible for botulism in infants caused by Clostridium botulinum?

A

Ingestion of spores in food or liquid

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98
Q

The classic form of foodborne botulism is characterized by the ingestion of:

A

Preformed toxin in food

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99
Q

Which of the following organisms will display lipase activity on egg yolk agar?

A

LIPASE + C. botulinum, C. sporogenes and C. novyi.

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100
Q

Feather-edged colonies usually surrounded by zone of green discoloration; produces a highly characteristic, fruity odor resembling apples or strawberries:

A

Alcaligenes faecalis

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101
Q

Which method is most useful for confirmation that a culture isolate is Group B streptococcus?

A

Direct hybridization

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102
Q

Salmonella-Shigella (SS) Agar is a modification of:

A

DCA

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103
Q

Possible cause of bulky or frothy stool:

A

Pancreatic disorder

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104
Q

Fruity or grapelike smell, corn tortilla-like odor:

A

P. aeroginosa

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105
Q

Fruity or grapelike smell, corn tortilla-like odor:

A

P. aeroginosa

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106
Q

Smell of ammonium cyanide (almond-like):

A

Chromobacterium violaceum

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107
Q

A gram-negative diplococcus that grows on modified Thayer-Martin medium can be further confirmed as Neisseria gonorrhoeae if it is:

A

Oxidase positive and glucose positive, maltose negative

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108
Q

Known as Koch’ bacillus

A

Mycobacterium tuberculosis

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109
Q

What is thr virulence factor of M. tb?

A

Cord factor

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110
Q

Serpentine cords

A

M.tb

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111
Q

Granulomatos lesions seen xray surrounded by fibroid cells

A

Ghon cells

112
Q

Skin test for TB

A

Purified protein derivative
Mantoux test

113
Q

Mantoux tuberculin test diameter of induration

A

5-10mm

114
Q

What is the meaning of DOTS

A

Direct observed treatment strategy

115
Q

Detection rate of mtb dots

A

70%

116
Q

Cure rate of mtb

A

85%

117
Q

Specimens of mtb (SB CUP)

A

Sputum
Blood
CSF
Urine
3Ps : pericardial, pleural, pericarditis

118
Q

Specimens of mtb (SB CUP)

A

Sputum
Blood
CSF
Urine
3Ps : pericardial, pleural, pericarditis

119
Q

AFB grading NATIONAL standard
REPORT: No seen AFB/300 fields

A

0

120
Q

1-9 AFB seen/100 fields

A

+n

121
Q

10-99 afb per 100 fields

A

1+

122
Q

1-10 AFB/50 fields

A

2+

123
Q

> 10 AFB per field NATIONAL GRADING

A

3+

124
Q

National TB GRADING
1 OR MORE per OIF

A

3+ (numerous)

125
Q

National grading: TB association
10 or more per slide

A

2+ (few)

126
Q

Digesting/mucolytic agent of MTB lab diagnosis

A

NALC - N-acetyl-L-cystein

127
Q

Decontaminant for mycobacterium

A

2-4% NaOH

128
Q

Other decontam and digestant of mycobacterium spp

A
  1. Trisodiun phosphate benzalkonium chloride (Zephraim)
  2. Dithiothreitol and NaOH
129
Q

Inhibitory of normal flora in egg based agar medium

A

Malachite green

130
Q

Media used for M.bovis highly concentrated of Malachite green

A

Petragnani

131
Q

Agar medium based in mycobacterium clear media for AST

A

Middlebrooke 7H10, 7H11

132
Q

Liquid medium for Mycobacterium

A

Middlebrooke 7H9/7H12

133
Q

Specimen for IGRA

A

Heparinized whole blood

134
Q

PCR BASED NAAT for detection of MTB from sputum. Detects rifampicin resistance

A

GeneXpert

135
Q

Rapid growers Mycobacterium
(PFaSC)

A

Mycobacterium
• phlei
• fortuitum
• smegmatid
• chelonei

136
Q

Yellow bacillus, causes pneumonia
A photochromogens (MASK)

A

M.kansasii (mas☆K)

137
Q

Photochromogen (MASK)
AGENT of swimming pool granuloma growth at 30°C

A

M.marinum (☆M- ask)

M -marinum
A - asiaticum
S - simiae
K - kansasii

138
Q

A scotochromogen (SSX Gordon)
Causes scrofola : urease positive

A

M. scrofulaceum

139
Q

A scotochromogen (SSX Gor)
Known aa the tap water bacillus

A

M.gordonae

140
Q

A nonphotochrom causes Lady Windermere syndrome

A

M.avium

141
Q

Mycobacterium causes pneumonia in HIV patients

A

M.avium-intracellulare complex

142
Q

Nonphotochrom mycobacterium known as inert bacillus, causes Buruli Ulcers

A

M.ulcerans

143
Q

Nonphotochrom known as Raddish bacillilus

A

M.terrae-triviale

144
Q

Hansens disease

A

M.leprae

145
Q

What is the specimen of leprosy?

A

Tissue juice earlobe/nasal scrapping

146
Q

Test for M.leprae

A
  1. Fernandez test (early)- 2days
  2. Mitsuda (late) - 3-4 weeks
147
Q

Niacin accumulation test is between what mycobacterium

A

Yellow (+) - M.tuberculosis
Negative(-) M.bovis

148
Q

Most useful biochem test for M.kansasii

A

Tween 80 HOH (pneumoniae)
(-) M.avium intracellulare: HIV pneumonia

149
Q

Positive isolates in pyrazinamidase

A

MTB and M.marinum
(-) M.bovis snd M.kansasii

150
Q

The mycobacterium susceptible in T2H Test

A

M.bovis

M.tb (R)

151
Q

Tropheryma whipplei disease

A

Whipples disease

152
Q

Which M. avium complex (MAC) organism is the most frequently isolated mycobacterium from AIDS patients?

A

M.avium

153
Q

A gram-positive branching filamentous organism recovered from a sputum specimen was found to be positive with a modified acid-fast stain method. What is the most likely presumptive identification?

A

Nocardia

154
Q

A CSF sample obtained from a 2-week old infant with suspected bacterial meningitis grew gram-negative rods on blood and chocolate agars. The following results were noted:

MacConkey agar = No growth
Glucose (open) OF = +
Glucose (closed) OF = Neg
Indole = +
Motility = Neg
42° C growth = Neg
ONPG = +
Urease = Neg
Catalase = +
Oxidase = +
Pigment = Yellow

A

Chryseobacterium meningosepticum

155
Q

Anaerobic gram-negative rods were recovered from the blood of a patient after gallbladder surgery. The bacteria grew well on agar containing 20% bile, but were resistant to kanamycin and vancomycin. What is the most likely identification?

A

B. fragilis is the most often isolated gram-negative anaerobic bacillus. It is resistant to many antibiotics. A good screening agar is a 20% bile plate that does not support the growth of Prevotella spp. or Porphyromonas spp.

156
Q

Large gram-positive bacilli (boxcar shaped) were recovered from a blood culture taken from a 70-year-old female diabetic patient. The following results were recorded:

Aerobic growth = Neg

Anaerobic growth = +

Spores = Usually absent (requires enhancement)

Lecithinase = +

Motility = Neg

Hemolysis = β (double zone)

GLC (volatile acids) = acetic acid and butyric acid

A

Clostridium perfringens

C. perfringens is an anaerobic gram-positive rod that is often isolated from the tissue of patients with gas gangrene (myonecrosis). Spore production is not usually seen with this organism, which may also stain gram negative.

157
Q

A Haemophilus spp., recovered from a throat culture obtained from a 59-year-old male patient undergoing chemotherapy, required hemin (X factor) and NAD (V factor) for growth. This species also hemolyzed horse erythrocytes on blood agar. What is the most likely species?

A

H. haemolyticus

H. haemolyticus requires both X and V factors for growth and lyses horse erythrocytes.

158
Q

A Haemophilus spp., recovered from a throat culture obtained from a 59-year-old male patient undergoing chemotherapy, required hemin (X factor) and NAD (V factor) for growth. This species also hemolyzed horse erythrocytes on blood agar. What is the most likely species?

A

H. haemolyticus

H. haemolyticus requires both X and V factors for growth and lyses horse erythrocytes.

159
Q

A patient with a human bite wound on the
right forearm arrived at the clinic for treatment. The wound was inflicted 36 hours earlier, and a culture was taken by the physician on duty. After 48 hours, the culture results were:

Gram-stain smear = Gram-negative straight, slender rods

Chocolate agar plate = “Pitting” of the agar by small, yellow, opaque colonies

Oxidase = +

Motility = Neg

Glucose = +

Growth in increased CO2 = +

A
160
Q

Eikenella corrodens

E. corrodens is part of the normal flora of the human mouth and typically “pits” the agar. This organism is capnophilic (needing increased CO2).

A

A patient with a human bite wound on the
right forearm arrived at the clinic for treatment. The wound was inflicted 36 hours earlier, and a culture was taken by the physician on duty. After 48 hours, the culture results were:

Gram-stain smear = Gram-negative straight, slender rods

Chocolate agar plate = “Pitting” of the agar by small, yellow, opaque colonies

Oxidase = +

Motility = Neg

Glucose = +

Growth in increased CO2 = +

161
Q

Eikenella corrodens

E. corrodens is part of the normal flora of the human mouth and typically “pits” the agar. This organism is capnophilic (needing increased CO2).

A

A patient with a human bite wound on the
right forearm arrived at the clinic for treatment. The wound was inflicted 36 hours earlier, and a culture was taken by the physician on duty. After 48 hours, the culture results were:

Gram-stain smear = Gram-negative straight, slender rods

Chocolate agar plate = “Pitting” of the agar by small, yellow, opaque colonies

Oxidase = +

Motility = Neg

Glucose = +

Growth in increased CO2 = +

162
Q

A sputum culture from a 13-year-old cystic fibrosis patient grew a predominance of short, gram-negative rods that tested oxidase negative. On MacConkey, chocolate, and blood agar plates, the organism appeared to have a lavender-green pigment. Further testing showed:

Motility = +

Glucose = + (oxidative)

Lysine decarboxylase = +

DNase = +

Maltose = + (oxidative)

Esculin hydrolysis = +

A

Stenotrophomonas maltophilia

S. maltophilia is the third most frequently isolated nonfermentative gram-negative rod in the clinical laboratory. Cystic fibrosis patients are at greater risk for infections because of previous antimicrobial treatment and recurrent pneumonia and because some strains may be colonizers.

163
Q

Bartonella quintana has been known to cause:

A

Trench fever

ROCHALIMEA/BARTONELLA QUINTANA: TRENCH FEVER
Trench fever, caused by B. quintana, was largely considered a disease of the past. Clinical manifestations of trench fever range from a mild influenza-like headache and bone pain to splenomegaly (enlarged spleen) and a short-lived maculopapular rash.

164
Q

For nonspecific staining of Rickettsia the recommended stain is:

A

Gimenez stain

Direct microscopic examination for Rickettsia organisms is possible using such stains as Giemsa, Machiavello, or Gimenez. The recommended procedure is the nonspecific Gimenez stain, which colors the organisms a brilliant red against a green background.

165
Q

The causative agent of endemic or murine typhus is:

A

Rickettsia typhi

Murine typhus is transmitted to humans by fleas infected with Rickettsia typhi. Prevalent in the southern U.S., it is primarily a disease of rodents and is sometimes transmitted to humans. Control of disease outbreaks is related to rodent (rat) control and the related rat flea population.

166
Q

The mild type of typhus fever that is caused by recrudescence of an initial attack of epidemic typhus is known as:

A

Brill-Zinsser disease

167
Q

Transmission of Orientia tsutsugamushi is associated with what vector?

A

Chiggers

O. tsutsugamushi
Scrub typhus
Vector: chiggers

168
Q

Which triad of symptoms is associated with rickettsial infections?

A

Fever, headache, and rashRickettsias are suspected when the triad of fever, headache, and rash is the primary clinical manifestation in patients with an exposure to insect vectors.

Infections caused by these organisms may be severe and are sometimes fatal.

169
Q

Which serovar of Chlamydia trachomatis causes lymphogranuloma venereum?

A

L1

trachomatis serovars L1, L2, L2b, and L3 are invasive causing LGV, in contrast to C. trachomatis serovars A-K, leaving the mucosa to spread to the regional lymph nodes.

170
Q

Corneal scrapings are collected and examined microscopically using a direct fluorescent test to detect inclusion bodies for the diagnosis of infection caused by:

A

Chlamydia trachomatis,

a leading cause of blindness, can be detected in corneal scrapings of suspected cases of trachoma and inclusion conjunctivitis.

171
Q

Chlamydia trachomatis causes which of the following?

A

Inclusion conjunctivitis

Chlamydia trachomatis is the causative agent of inclusion conjunctivitis, trachoma, and genital tract infections, including lymphogranuloma venereum

172
Q

Spirochetes often detected in the hematology laboratory, even before the physician suspects the infection, are:

A

Borrelia spp.

are often seen on Wright’s-stained smears of peripheral blood as helical bacteria with 3–10 loose coils. They are gram negative but stain well with Giemsa’s stain.

173
Q

Spirochetes often detected in the hematology laboratory, even before the physician suspects the infection, are:

A

Borrelia spp.

are often seen on Wright’s-stained smears of peripheral blood as helical bacteria with 3–10 loose coils. They are gram negative but stain well with Giemsa’s stain.

174
Q

Borrelia burgdorferi, a spirochete transmitted by Ixodes dammini in the northeastern U.S., is the etiologic agent of:

A

Lyme disease

175
Q

Borrelia burgdorferi, a spirochete transmitted by Ixodes dammini in the northeastern U.S., is the etiologic agent of:

A

Lyme disease

176
Q

The etiologic agent of epidemic relapsing fever is Borrelia recurrentis, which is commonly transmitted by:

A

Lice

The human body louse, Pediculus humanus, is the vector for Borrelia recurrentis. Pathogenic species not only have specific vectors but also well-defined geographical distributions.

177
Q

During the first week of leptospirosis, the most reliable way to detect the presence of the causative agent is by the direct:

A

Culturing of blood

Leptospira spp. are most reliably detected during the first week of illness by the direct culturing of a blood sample. The media of choice are Fletcher semisolid and Stuart liquid medium, both of which are supplemented with rabbit serum.

178
Q

Serious congenital infections are associated with:

A

Treponema pallidum subsp. pallidum

Hutchinson’s triad: a triad of symptoms that comprises Hutchinson’s (notched) teeth, interstitial keratitis, and deafness and occurs in children with congenital syphilis

Syphilis is caused by Treponema pallidum subsp. pallidum. Congenital syphilis occurs when a pregnant woman has a septicemia, and the spirochetes cross the placenta and infect the fetus. Infection can affect fetal development and cause premature birth or fetal death, or the pregnancy may go to term. Following in utero infection, the infant is most often born with lesions characteristic of secondary syphilis; perinatal death is not an uncommon consequence of infection.

179
Q

Detection of antibody against cardiolipin is useful for the diagnosis of which of the following diseases?

A

Syphilis

Cardiolipin is a tissue lipid produced as a byproduct of treponemal infection. Nontreponemal tests for syphilis take advantage of antibodies made to cardiolipin. The most commonly used tests are the rapid plasma reagin (RPR) for serum and the Venereal Disease Research Laboratory (VDRL) for cerebrospinal fluid.

180
Q

Spirillum minus also causes rat-bite fever in humans and is referred to as:

A

Sodoku

Spirillum minus also causes rat-bite fever in humans and is referred to as sodoku. The clinical signs and symptoms are similar to those caused by Streptobacillus moniliformis, except that arthritis is rarely seen in patients with sodoku and swollen lymph nodes are prominent; febrile episodes are also more predictable in sodoku.

181
Q

“Lumpy jaw” is caused by:

A

Actinomyces israelii

LOCK JAW: C. tetani
LUMPY JAW: Actinomyces

182
Q

Sulfur granules in a clinical specimen indicate the presence of:

A

Actinomyces spp.

Direct examination and the macroscopic presence in purulent exudate of “sulfur granules,” which reveal gram-positive filaments when crushed, is diagnostic for an infection with Actinomyces spp.

183
Q

Which Nocardia sp. causes more than 80% of human infections?

A

N. asteroides

Infections caused by Nocardia spp. can occur in immunocompetent and immunocompromised individuals. N. asteroides, N. brasiliensis, and N. otitidiscaviarum are the major causes of these infections, with N. asteroides causing greater than 80% of infections.

184
Q

Which actinomycete is partial acid-fast, has extensive aerial hyphae, and is lysozyme resistant?

A

Nocardia sp.

185
Q

Which organisms may stain partially acid-fast when stained with a modified acid-fast stain?

A

If the modified acid-fast stain results are positive, the isolate is a probable partially acid-fast aerobic actinomycete (i.e., Nocardia, Rhodococcus, Tsukamurella, or Gordonia sp).

186
Q

Susceptibility to thiophene-2-carboxylicacid hydrazide (T2H) is characteristic of which of the following mycobacteria?

A

M. bovis

187
Q

Growth inhibition by thiophene-2-carboxylichydrazide (T2H) is used to differentiate M. tuberculosis from which other Mycobacterium specie?

A

M. bovis

188
Q

Mycobacterium fortuitum, a rapidly growing Mycobacterium, grows on MacConkey agar in 5 days. Which other species of Mycobacterium is able to demonstrate growth within the same time period on MacConkey agar?

A

M. chelonei

The MacConkey agar used for mycobacteria identification is a different formulation than that used for enterics, in that crystal violet is omitted. A MacConkey agar plate is inoculated with a 7-day broth culture of the test organism. The inoculated plate is then incubated at 37°C. Plates are checked for growth at 5 days, and if no growth is detected, they are checked daily until day 11, at which time they are discarded as negative. M. fortuitum and M. chelonei are the only mycobacteria able to grow on MacConkey agar in 5 days.

189
Q

A slowly growing, orange-pigmented, acid-fast bacillus was isolated from a cervical lymph node of a child with symptoms of cervical adenitis. The most likely etiologic agent in this case would be:

A

Mycobacterium scrofulaceum

190
Q

Which of the following is a fluorescent stain for mycobacteria?

A

Auramine-rhodamine

Auramine-rhodamine is a fluorescent stain used to visualize the mycobacteria. The bacteria retain the stain and will appear bright yellow against a black background.

Because it is easier to see the bacilli, this stain is more sensitive than a fuschin-based stain (e.g., Ziehl-Neelsen).

191
Q

Mycobacteria can be examined by using the:

A

Kinyoun stain

Acid-fast bacilli can be demonstrated in stained smears of clinical material using the Ziehl-Neelsen or Kinyoun acid-fast stains. The Kinyoun carbol-fuchsin method uses a higher concentration of phenol in the primary stain to accelerate the staining process. Therefore, unlike the Ziehl-Neelsen stain, the Kinyoun stain does not need to be heated.

192
Q

Which of the following media would not be routinely used to culture Mycobacterium spp.?

A

Chocolate agar

193
Q

Mycobacteria have a large amount of a component in their cell wall that other bacteria lack. That component is:

A

Lipids

Mycobacteria characteristically possess a high lipid content, unlike gram-positive cocci and gram-negative bacteria. The high lipid content acts to protect these organisms from dehydration and the lethal effects of alkali, various germicides, alcohol, and acids. Thus, these bacteria do not stain well with the Gram stain, and an acid-fast staining technique must be used.

194
Q

Pregnant women and immunocompromised patients should avoid eating which of the following foods to prevent Listeria infection?

A

Feta cheese

The general population should always properly wash raw vegetables and thoroughly cook vegetables and meat to prevent listerosis.

195
Q

A 1-week-old newborn develops meningitis. Short, gram-positive rods are isolated. History reveals that the mother had eaten unpasteurized cheese from Mexico during pregnancy, and she recalled having a flu-like illness. Which of the following is the most likely etiologic microorganism?

A

Listeria monocytogenes

Listeria multiplies both extra-cellularly and intracellularly, but under most circumstances, a competent immune system eliminates Listeria. As expected, listeriosis is seen in the very young and the very old, and in people with compromised immune systems.

196
Q

A Gram stain of organisms of Loeffler agar showed pleomorphic gram-positive bacilli. The organism should be subcultured to:

A

Potassium tellurite

Media containing potassium tellurite is used for the recovery of Corynebacterium diphtheriae

197
Q

Symptoms of C. botulinum food poisoning include double vision, inability to speak, and respiratory paralysis. These symptoms are consistent with:

A

Ingestion of a neurotoxin

198
Q

Symptoms of C. botulinum food poisoning include double vision, inability to speak, and respiratory paralysis. These symptoms are consistent with:

A

Ingestion of a neurotoxin

199
Q

A fastidious gram-negative bacillus was isolated from a case of periodontal disease, which upon darkfield examination was noted to have GLIDING MOTILITY. The most likely identification of this etiologic agent would be:

A

Capnocytophaga

Capnocytophaga spp. are fermentative gram-negative bacteria that inhabit the oral cavity of humans. These organisms have been identified as a cause of disease in the oral cavity, and in compromised hosts they have been implicated in systemic disease isolated from cerebrospinal fluid, pleural fluid, and pulmonary secretions. The gliding motility is best observed during the log phase of growth and can be demonstrated by darkfield microscopy and on sheep blood agar by the production of concentrically spreading growth around primary colonies.

200
Q

An environmental sampling study of respiratory therapy equipment produced cultures of a yellow, nonfermentative (at 48 hours), gram-negative bacillus from several of the nebulizers, which would most likely be species of:

A

Chryseobacterium spp.

are ubiquitous in the environment and are especially associated with moist soil and water. Chryseobacterium (formerly Flavobacterium) meningosepticum, a known nosocomial pathogen, has been implicated in outbreaks of meningitis in hospitals and is associated with the use of contaminated respiratory therapy equipment.

201
Q

Which of the following is NOT required for growth of Streptobacillus moniliformis?

A

Cystine

Streptobacillus moniliformis is a gram-negative bacillus that requires media containing blood, serum, or ascites fluid as well as incubation under carbon dioxide (CO2) for isolation from clinical specimens. This organism causes rat-bite fever and Haverhill fever in humans.

202
Q

When Streptobaccilus moniliformis is acquired by ingestion, the disease is called:

A

Haverhill fever

Streptobacillus moniliformis is a gram-negative bacillus that requires media containing blood, serum, or ascites fluid as well as incubation under carbon dioxide (CO2) for isolation from clinical specimens. This organism causes rat-bite fever and Haverhill fever in humans.

203
Q

Which of the following conditions is viewed as a risk factor for systemic disease caused by Pasteurella multocida subsp. multocida?

A

Liver cirrhosis

P. multocida subsp. multocida is most commonly encountered in clinical specimens. Reported virulence factors for this subspecies include lipopolysaccharide, cytotoxin, six serotypes of the antiphagocytic capsule, surface adhesins, and iron-acquisition proteins.

204
Q

The best medium for culture of Francisella tularensis is:

A

Cystine glucose blood agar

Francisella tularensis is fastidious and not readily recovered in culture. Cysteine blood glucose agar is an enriched medium with beef heart infusion, peptones, glucose and rabbit blood. It also includes cystine, which is required by F. tularensis for growth.

205
Q

Media used to support growth of Legionella pneumophila should contain which of the following additives?

A

Charcoal and yeast extract

206
Q

Milk has classically been the primary food associated with the transmission of some diseases, especially for those diseases of cattle transmissible to humans, such as:

A

Brucellosis

Brucella infects cattle and may be transmitted to humans by the ingestion of contaminated milk or other dairy products. Milk is able to support the growth of many clinically significant microorganisms, which may often be ingested in unpasteurized dairy products.

207
Q

Fever of unknown origin in a farmer who raises goats would most likely be caused by which of the following organisms?

A

Brucella melitensis

Brucella are small, aerobic, Gram-negative coccobacilli. Of the four well-characterized species of Brucella, only one—B. melitensis—characteristically infects both goats and humans. Brucellosis may be associated with gastrointestinal and neurologic symptoms, lymphadenopathy, splenomegaly, hepatitis, and osteomyelitis.

208
Q

Which of the following characteristics best differentiates Bordetella bronchiseptica from Alcaligenes species?

A

Rapid hydrolysis of urea

209
Q

Colonies that are said to resemble “droplets of mercury” are characteristic of:

A

Bordetella pertussis

Bordetella pertussis is the etiologic agent of pertussis, or whooping cough. On Bordet-Gengou or Regan-Lowe agars, the organism forms small, round colonies that resemble mercury droplets. A nasopharyngeal swab is recommended as the optimal specimen for the recovery of this agent.

210
Q

The best medium for culture of Bordetella pertussis is:

A

Regan-Lowe agar

211
Q

A positive hippurate hydrolysis is a characteristic of:

A

Campylobacter jejuni

212
Q

Which of the following has been recognized in postinfectious complications of a Campylobacter jejuni infection?

A

Guillain-Barré syndrome

213
Q

The optimal incubator temperature for isolation of the Campylobacter jejuni/coli group is:

A

42C

214
Q

Which of the following media can be used to culture Campylobacter jejuni?

A

Skirrow medium

215
Q

All of the following organisms require X and V factors, except:

A

Aggregatibacter aphrophilus

H. aphrophilus is the only species that does not require X or V factors.

H. aphrophilus is an uncommon cause of endocarditis and is the H member of the HACEK group of bacteria associated with slowly progressive (subacute) bacterial endocarditis.

216
Q

Into which genus have Haemophilus aphrophilus and Haemophilus paraphrophilus been recently reclassified?

A

Aggregatibacter

Haemophilus aphrophilus and Haemophilus paraphrophilus have been reclassified as a single species based on multilocus sequence analysis.

Aggregatibacter aphrophilus now includes both the hemin-dependent and hemin-independent isolates.

217
Q

An unimmunized, 2-year-old boy presents with drooling from the mouth, elevated temperature, and enlarged tonsils. During attempts at intubation, no gray-white membrane is observed but the epiglottis appears “beefy” red and edematous. Which of the following is the most likely organism?

A

Haemophilus influenzae

218
Q

The porphyrin (D-ALA) test was devised to detect strains of Haemophilus capable of:

A

Synthesis of hemin

219
Q

Which organism has large, smooth, glistening colonies with a lavender pigment and smells like ammonia?

A

Stenotrophomonas maltophilia

Large, smooth, glistening colonies with uneven edges and lavender-green to light purple pigment; greenish discoloration underneath growth; ammonia smell

220
Q

If present, a characteristic that is helpful in separating Pseudomonas aeruginosa from other members of the Pseudomonas family is:

A

Growth at 42ºC

Pseudomonas aeruginosa grows at 42˚C but this temperature is inhibitory for other Pseudomonas species

221
Q

Which organisms are plump coccobacilli that may resist decolorization and may be mistaken for Neisseria spp?

A

Acinetobacter spp

Acinetobacter spp. are plump coccobacilli that tend to resist alcohol decolorization; they may be mistaken for Neisseria spp.

222
Q

A wound (skin lesion) specimen obtained from a newborn grew predominantly β-hemolytic colonies of gram-positive cocci on 5% sheep blood agar. The newborn infant was covered with small skin eruptions that gave the appearance of a “scalding of the skin.” The gram-positive cocci proved to be catalase positive. Which tests should follow for the appropriate identification?

A

Coagulase, glucose fermentation, DNase

S. aureus is the cause of “scalded skin” syndrome in newborn infants. The production of a potent exotoxin (exfoliatin) causes the epidermis to slough off, leaving the newborn’s skin with a red, raw texture
or a burned, scalded look.

223
Q

An isolate of Staphylococcus aureus was cultured from an ulcer obtained from the leg of a diabetic 79-year-old female patient. The organism showed resistance to methicillin. Additionally, this isolate should be tested for resistance or susceptibility to:

A

Vancomycin

MRSA isolates are usually tested for susceptibility or resistance to vancomycin, a glycopeptide.

224
Q

A 65-year-old female outpatient was requested by her physician to submit a 24-hour urine specimen for protein and creatinine tests. He also requested testing for mycobacteria in the urine. Should the microbiology laboratory accept this 24-hour specimen for culture?

A

No, the specimen is unsuitable for the recovery of mycobacteria

225
Q

To read the hemolytic reaction on a blood agar plate accurately, the technologist must hold the plate up to the light and observe the plate with:

A

Transmitted light

226
Q

Staphylococcus aureus toxin which disrupts the smooth muscle in blood vessels and is toxic to erythrocytes, leukocytes, hepatocytes, and platelets:

A

Alpha toxin

Most strains of S. aureus produce ALPHA toxin, which disrupts smooth muscle in blood vessels and is toxic to erythrocytes, leukocytes, hepatocytes, and platelets.

227
Q

Composition of McFarland standard:

A

1% sulfuric acid and 1.175% barium chloride

McFarland turbidity standards, prepared by mixing 1% sulfuric acid and 1.175% barium chloride to obtain a solution with a specific optical density, are commonly used.

228
Q

The 0.5 McFarland standard, which is commercially available, provides an optical density comparable to the density of a bacterial suspension of:

A

1.5 x 10 8th CFU/mL

229
Q

Bone marrow toxicity is the major side effect associated with:

A

Chloramphenicol

230
Q

Monobactams

A

Inhibits cell wall synthesis

231
Q

Interferes with folic acid pathway by binding the enzyme dihydropteroate synthase:

A

Sulfonamides

232
Q

Media employ some factor (or factors) that allows colonies of one bacterial species or type to exhibit certain metabolic or culture characteristics that can be used to distinguish it from other bacteria growing on the same agar plate:

A

Differential media

233
Q

Moderate growth; growth is out to the third quadrant:

A

3+

Numbers of organisms present can subse- quently be graded as 4+ (many, heavy growth) if growth is out to the fourth quadrant, 3+ (moderate growth) if growth is out to the third quadrant, 2+ (few or light growth) if growth is in the second quadrant, and 1+ (rare) if growth is in the first quadrant

234
Q

CSF collected from a shunt

A

BAP, CAP, THIO

CSF
BA, CA (Routine)
BA, CA, thio (Shunt)

235
Q

An outbreak of Staphylococcus aureus has occurred in a hospital nursery. In order to establish the epidemiological source of the outbreak, the most commonly used typing method is:

A

Pulsed-field gel electrophoresis

The most commonly used method to determine the relatedness of 2 or more bacterial strains is pulsed-field gel electrophoresis.

236
Q

During the past month, Staphylococcus epidermidis has been isolated from blood cultures at 2-3 times the rate from the previous year. The most logical explanation for the increase in these isolates is that:

A

There has been a break in proper skin preparation before drawing blood for culture

Appropriate skin antisepsis is the most important factor in preventing contaminated blood cultures. Staphylococcus epidermidis is a common blood culture contaminant because it is a common inhabitant of the skin.

237
Q

In a quality control procedure on a new batch of Mueller-Hinton plates using a stock culture of Staphylococcus aureus (ATCC 25923), all the disk zone sizes are too small. The most likely reason for this is that the:

A

Bacterial suspension was not diluted to the proper concentration

Quality control zone sizes that are too small could indicate that the organism inoculum is too high, plate were poured too thick or that the potency of the antibiotic disks is too low.

238
Q

To quality control the autoclave, a vial of Bacillus stearothermophilus is autoclaved and should than be:

A

Incubated at 56C

Bacillus stearothermophilus is commonly used as an indicator organism for the appropriate functioning of autoclaves.

Unlike most Bacillus species, B. stearothermophilus grows at 56˚C.

239
Q

Which of the following is the most important variable in the recovery of organisms in patients with bacteremia?

A

The volume of blood cultured

The volume of blood collected is the single most important variable in the recovery of organisms in patients with bloodstream infections.

240
Q

Quality control results for disk diffusion susceptibility tests yield the following results: aminoglycoside zones too small and penicillin zones too large. This is most likely due to the:

A

pH of Mueller-Hinton agar being too low

Mueller-Hinton Agar used for disk diffusion is standardized at pH 7.2 to 7.4.

241
Q

Which of the following tests is used to monitor bactericidal activity during antimicrobic therapy in cases of endocarditis?

A

Schlichter

The serum bactericidal, or Schlichter test can be used to assess the activity of patient’s serum when they are receiving long term therapy for endocarditis or osteomyelitis. High titers of antibacterial activity in the serum suggest adequate dosing, a non-tolerant isolate or normal elimination of the antibiotic.

242
Q

A 21-year-old patient presents with pharyngitis. A throat swab is collected and submitted for anaerobic culture. This specimen should be:

A

Rejected as unacceptable

Many anaerobic bacteria are commensal flora in the oropharynx. Anaerobic bacteria do not cause pharyngitis. The most common cause of pharyngitis is Streptococcus pyogenes. Other causes include Arcanobacterium haemolyticum, Corynebacterium diphtheriae, Neisseria gonorrhoeae and viruses.

243
Q

A 21-year-old patient presents with pharyngitis. A throat swab is collected and submitted for anaerobic culture. This specimen should be:

A

Rejected as unacceptable

Many anaerobic bacteria are commensal flora in the oropharynx. Anaerobic bacteria do not cause pharyngitis. The most common cause of pharyngitis is Streptococcus pyogenes. Other causes include Arcanobacterium haemolyticum, Corynebacterium diphtheriae, Neisseria gonorrhoeae and viruses.

244
Q

A patient exhibits fever, chills, abdominal cramps, diarrhea, vomiting, and bloody stools 10 to 12 hours after eating. Which organisms will most likely grow from this patient’s stool culture?

A

E. coli O157:H7 or Shigella spp.

Both E. coli O157:H7 and Shigella spp. are invasive and cause bloody stools.

245
Q

The primary isolation of Neisseria gonorrhoeae requires:

A

Neisseria gonorrhoeae requires an enhanced CO2 atmosphere for optimal growth.

246
Q

Characteristics of the HACEK group of bacteria include:

A

Requirement of 5 to 10% CO2 for growth

The HACEK group of organisms are gram negative bacilli that require increased CO2 for growth.

247
Q

A child was bitten on the arm by her sibling and the resulting would grew a slender gram-negative bacilli that has the following characteristics:

A

Eikenella corrodens

“Pitting of agar” and the bleach smell of the colonies are hallmark characteristics of Eikenella corrodens

248
Q

Acinetobacter lwoffii differs from Neisseria gonorrhoeae in that the former:

A

Will grow on MacConkey and EMB media

Both organisms are gram negative, Neisseria gonorrhoeae is fastidious and does not grow on MacConkey or EMB agar, but Acinetobacter does. Neisseria is oxidase positive and Acinetobacter is oxidase negative.

249
Q

In the optochin (ethylhydrocupreine hydrochloride) susceptibility test, if there is a zone of inhibition of 19 to 30 mm surrounding the disk following overnight incubation at 37°C, the colony most likely consists of:

A

Pneumococci

250
Q

Which of the following is the most appropriate specimen source and primary media battery?

A

Endocervical - chocolate, Martin Lewis

Chocolate agar and chocolate agar based selective media (Martin Lewis) are routinely used for the recovery of Neisseria gonorrhoeae from genital specimens.

251
Q

CSF from a febrile 25-year-old man with possible meningitis is rushed to the laboratory for a stat Gram stain and culture. While performing the Gram stain, the technologist accidentally spills most of the specimen. The smear shows many neutrophils and no microorganisms. Since there is only enough CSF to inoculate one plate, the technologist should use a:

A

Chocolate agar plate

252
Q

Which biochemical tests should be performed in order to identify colorless colonies growing on MacConkey agar (swarming colonies on blood agar) from a catheterized urine specimen?

A

Indole, phenylalanine deaminase, and urease

253
Q

Direct spread of pneumonic plague disease occurs by which route?

A

Inhalation of contaminated airborne droplets

254
Q

Nutritionally variant streptococci (NVS) require specific thiol compounds, cysteine, or the active form of vitamin B6. Which of the following tests supplies these requirements?

A

Staphylococcal cross-streak test

255
Q

Which organism is the most often recovered gram-positive cocci (catalase negative) from a series of blood cultures obtained from individuals with endocarditis?

A

Enterococcus faecalis

256
Q

Resistance to which drug categorizes a strain of Staphylococcus aureus as methicillin-resistant Staphylococcus aureus (MRSA)?

A

Oxacillin

Oxacillin is the drug used to screen staphylococci for resistance to antibiotics having the β-lactam ring. Included in this group are penicillin, cephalosporin, monobactam, and carbapenem. MRSA defines strains of staph that are resistant to all of these antibiotic groups. MRSA strains are treated with vancomycin or oxazolidinone

257
Q

During childbearing years, the normal flora of the vagina is predominantly:

A

Lactobacillus

258
Q

Stains the cell wall of fungi:

A

Calcofluor white

259
Q

What step in the Gram stain distinguishes between gram-positive and gram-negative organisms?

A

Decolorization using alcohol or acetone

260
Q

What is the stain that binds to the nucleic acid of organisms but does not discriminate between gram-positive or gram-negative organisms called?

A

Acridine orange stain

The fluorochrome acridine orange binds to nucleic acid. This staining method can be used to confirm the presence of bacteria in blood cultures when Gram stain results are difficult to interpret or when the presence of bacteria is highly suspected but none are detected using light microscopy.

261
Q

Patient preparation for fungal culture:

A

Wipe nails or skin with 70% alcohol

NOTE:
PATIENT PREPARATION: Nails or skin: wipe with 70% alcohol
FOR MICROSCOPY/VISUALIZATION OF FUNGAL ELEMENTS: KOH

262
Q

Cerebrospinal fluid from a febrile 25-year-old man with possible meningitis is rushed to the laboratory for a stat Gram stain and culture. While performing the Gram stain, the technologist accidentally spills most of the specimen. The smear shows many neutrophils and no microorganisms. Since there is only enough CSF to inoculate one plate, the technologist should use a:

A

Enriched media such as chocolate agar has no inhibitory effects on bacterial growth and contains additional nutrients that support the growth of fastidious organisms such as H. influenzae and Neisseria.

263
Q

For ova and parasites (O&P), collect ____ specimens every other day at a minimum for outpatients.

A

Three specimens

264
Q

Unpreserved stool should be transported to the laboratory in:

A

Less than 1 hour at room temperature

265
Q

For patient preparation, wipe abscess with:

A

Sterile saline or 70% alcohol

266
Q

This cabinet is selected if radioisotopes, toxic chemicals, or carcinogens will be used:

A

Biological safety cabinet class IIB

267
Q

The exhaust air in class ___ cabinets is discharged outside the building.

A

Biological safety cabinet class IIB

The exhaust air in class IIB cabinets is discharged outside the building.

A class IIB cabinet is selected if radioisotopes, toxic chemicals, or carcinogens will be used

268
Q

Cabinet is self-contained, and 70% of the air is recirculated:

A

Biological safety cabinet class IIA

269
Q

Cabinets allow room (unsterilized) air to pass into the cabinet and around the area and material within, sterilizing only the air to be exhausted:

A

Biological safety cabinet class I

270
Q

Filtration of air is accomplished using high-efficiency particulate air (HEPA) filters designed to remove organisms _______ μm from isolation rooms, operating rooms, and biologic safety cabinets (BSCs).

A

Larger than 0.3 um

Filtration of air is accomplished using high-efficiency particulate air (HEPA) filters designed to remove organisms larger than 0.3 μm from isolation rooms, operating rooms, and biologic safety cabinets (BSCs).

271
Q

Safest method to ensure that no infective materials remain in samples or containers when disposed:

A

Incineration is the most common method of treating infectious waste. Hazardous material is literally burned to ashes at temperatures of 870° to 980°C. Incineration is the safest method to ensure that no infective materials remain in samples or containers when disposed.

272
Q

Genes encoded in extrachromosomal genetic elements, such as PLASMIDS and TRANSPOSONS, may be transferred by:

A

Conjugation

In addition to chromosomal DNA, genes encoded in extrachromosomal genetic elements, such as plasmids and transposons, may be transferred by conjugation.

273
Q

Synthesis of protein

A

Replication - duplication of DNA

Transcription - synthesis of RNA from a DNA template

Translation - synthesis of protein

274
Q

Synthesis of RNA from a DNA template:

A

Replication - duplication of DNA

Transcription - synthesis of RNA from a DNA template

Translation - synthesis of protein

275
Q

Which 2 diseases are usually preceded by infection with beta-hemolytic streptococci?

A

Glomerulonephritis, rheumatic fever

RMT AUG 2024 (12 decks)

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