Adv Micro exam 1

An oxidase positive, gram negative rod has been isolated. It is indole positive, non-motile, and produces yellow-pigmented colonies. the most likely genus is

Elizabethkingia (Chryseobacterium)

Stenotrophomonas maltophilia is usually susceptible to which of the following drugs?

SXT

The only non glucose fermenter that is indole positive is:

Elizabethkingia (Chryseobacterium)

An anaerobic long thin gram negative rod that is sensitive to penicillin and kanamycin is most likely

Fusobacterium nucleatum

Growth on the anaerobic blood agar plate from a wound culture shows flat irregular colonies with a double zone of hemolysis. The lecithinase reaction is positive. Gram stain of the colonies would most likely show:

Large Gram Positive Rods (‘boxcar’ shape) with spores

An anaerobe that is a gram negative rod grows in the presence of 20% bile and is resistant to kanamycin and penicillin is:

Bacteroides fragilis

A direct smear from a brain abscess which revealed gram negative slender rod with tapered ends might lead the technologist to suspect which of the following anaerobes?

Fusobacterium spp.

Anaerobic infections differ from aerobic infections in which of the following ways?

They are usually polymicrobic

In which of the following types of specimens are anaerobic bacteria normally present in sufficiently large numbers so that specific anaerobic cultures should not be performed?

Feces, vaginal discharge, and upper respiratory secretions

Which test group BEST differentiates Acinetobacter spp. from Pseudomonas aeruginosa?

Oxidase, motility, and growth at 42 C

The most noted difference between Pseudomonas aeruginosa and Stenotrophomonas maltophilia is:

Oxidase

A gram negative rod has been isolated on MacConkey. It is oxidase negative, non-motile, and does not reduce nitrate. the most likely genus is

Acinetobacter

An anaerobic gram + rod that may be tentatively identified by the appearance of a double zone of hemolysis around its colony on blood agar is:

Clostridium perfringens

On gram stain from a positive blood culture bottle a diphtheroid appearing gram positive rod is seen. In subsequent subcultures it is found to grow anaerobically only. Other results include: Catalase positive. Indole positive. The organism is most likely:

Cutibacterium (Propionibacterium) acnes

A presumptive identification of Bacteroides fragilis is essential to the treatment of a patient because:

It can be resistant to antibiotics

Small anaerobic gram negative cocci are isolated from the blood of a patient post-surgery for repair of a fractured jaw. what is the probable genus?

Veillonella

Why are certain body specimens such as stool or vaginal generally NOT acceptable for anaerobic culture?

Anaerobes are part of the normal flora here

Which of the following tests is most appropriate for the rapid identification of Clostridium difficile?

Toxin assay kit

Match the following organisms with their expected results for motility and oxidase:
Moraxella
Acinetobacter calcoaceticus var anitratus
Stenotrophomonas maltophilia
Pseudomonas aerginosa

Moraxella: oxidase pos motility neg. Acinetobacter calcoaceticus var anitratus: oxidase neg, motility neg
Stenotrophomonas maltophilia: oxidase neg, motility pos
Pseudomonas aeruginosa: oxidase pos, motility pos

Infant botulism

Occurs after ingestion of spores but not toxin

Which of the following is LEAST likely to be caused by anaerobic bacteria?

Cystitis

The preferred way to collect a specimen for culture of anaerobes is by:

Aspiration or tissue

An anaerobic non-spore forming gram positive rod that is catalase positive and produces indole is:

Cutibacterium (Propionibacterium) acnes

Sulfur granules found in material discharged from a subcutaneous facial abscess, which have thin radiating branching rods on their periphery, are characteristic of infection due to

actinomyces israelii

What are the most appropriate screening tests to presumptively differentiate the non-glucose fermenting gram negative rods from the Enterobacteriaceae?

Oxidase, TSI, nitrate reduction, and growth on MacConkey agar

Gas gangrene is caused by:

C. perfringens

A draining lesion developed following a human bite. Gram stain of the pus showed gram positive bacilli with a tendency to branch. Anaerobic cultures were positive for organisms with the same morphology. The most likely identification is:

Actinomyces israelii

An anaerobic gram positive rod has been isolated from a peritoneal abscess. The gram stain revealed subterminal spores. What genus does this organism belong to?

Clostridium

Which of the following statements about botulinum toxin is correct

Food-borne botulism is most common

Yellow colonies of an indole positive gram negative rod isolated from a hospital water bath are most likely:

Elizabethkingia meningoseptica

Upon examining plates and broth media from a wound culture at 48 hours, you detect no growth on BAP, Choc, and MAC but the broth media is very cloudy. Select the most appropriate action to complete the culture workup

Gram stain the broth and plate aerobically and anaerobically

The best-known treatment for persons suffering from food poisoning due to Clostridium botulinum is with:

Specific type antitoxin

The pathogenic anaerobic bacteria most frequently isolated in the clinical laboratory is:

Bacteroides fragilis

An anaerobic gram-positive rod that may be tentatively identified by the appearance of a double zone of hemolysis around its colony on blood agar is:

Clostridium perfringens

Anaerobic blood agar containing kanamycin and vancomycin would be selective for:

Bacteroides

The only non-glucose fermenter that is indole positive is:

Elizabethkingia (Chryseobacterium)

Morphologically on gram stain – Acinetobacter is most likely confused with:

Neisseria

An anaerobic gram + rod that may be tentatively identified by the appearance of a double zone of hemolysis around its colony on blood agar is:

Clostridium perfringens

After 48 hours of anaerobic incubation the colonies on a blood agar plate fluoresce brick red under UV light. After 2 more days of incubation, the colonies on the plate are black. The organism is

Prevotella melaninogenicus

Methylene blue is used in:

Anaerobic indicators

An organism isolated from the surface of a skin burn is found to produce a diffusible green pigment on tech agar. Further studies would most likely show the organism to be:

Oxidase positive and resistant to most antibiotics

The presumptive tests used for the identification of Pseudomonas spp. Are:

Oxidase, O/F glucose, motility, and pigment production

A vaginal swab specimen in anaerobic transport media for anaerobic culture is submitted to the lab from a patient with suspected endometriosis. The proper action would be to:

Do not culture – request a properly collected specimen, explaining that anaerobes are normal flora in that site

Why are certain body specimens such as stool or vaginal generally NOT acceptable for anaerobic culture?

Anaerobes are part of the normal flora here

The following anaerobic infection is preventable by administering a vaccine.

Tetanus

The initial step in identification of colonies growing on anaerobic culture plates is:

Verification that the isolate is anaerobic by subculture and incubation aerobically and anaerobically

Food poisoning due to improperly home canned vegetables and meats is most likely caused by:

Clostridium botulinum

Certain clinical signs often suggest the presence of an anaerobic infection. Which of the following indicate the presence of anaerobic bacteria?

Infection secondary to human bite

Which of the following specimen types would be considered MOST appropriate for the culture of anaerobes?

Peritoneal abscess

Which of the following most often causes antibiotic associated pseudomembranous colitis?

Clostridium difficile

A swab from a facial abscess was sent to the lab and the following results were obtained: Direct smear: Many WBCs, Many gram positive rods with a tendency to branch. BAP: No growth at the end of 48 hours. Anaerobic chopped meat glucose broth: Growth in the bottom half of the tube in discrete colonies with no gas. Gram stain of broth: Branching gram positive rods

actinomyces

The BBL gas pak used in an anaerobic system produces hydrogen which is important because:

Hydrogen removes oxygen by forming H2O

A distinguishing characteristic of Mycoplasma is that they:

Utilize sterols for growth

Specimen of choice for the isolation of Ureaplasma urealyticum is:

Vaginal

An acid fast bacillus has been isolated which has an orange pigment when grown in either the light or the dark. The organism is:

A scotochromogen

Select the Mycobacterium species which best fits the following description: non-photochrome, tellurite +, often isolated from HIV patients

M. avium complex

Select the Mycobacterium species which best fits the following description: scotochrome, catalase +, Tween =, urease +

M. scrofulaceum

An acid fast bacillus has been isolated which produces a yellow pigment after exposure to light. The organism is:

A photochromogen

The most common cause of Community acquired bacterial pneumonia is:

Streptococcus pneumoniae

Select the diseases for which Streptococcus pyogenes is responsible:

Acute glomerulonephritis, scarlet fever

Which of the following sputum specimens is LEAST acceptable for bacteriologic culture as determined by the following direct smear results?

10 Leukocytes, 30 squamous epithelial cells/LPF

The body's major defense against bacterial infection of the lungs (pneumonia) is:

Sweeping action of the muco-ciliary lining of the respiratory tract

Specimen(s) of choice for the isolation of Mycoplasma pneumoniae is (are):

Sputum

The slow growing photochromogenic organism typically isolated from a chronic skin lesion on the leg of a scuba diver is:

Mycobacterium marinum

An acid fast photochromogen isolated from a sputum specimen grows slowly at 35°C; It is strongly catalase positive niacin negative and nitrate positive. The MOST probable identity is:

Mycobacterium kansasii

Which of the following Mycobacteria is included in the Runyoun group IV rapid growers?

M. fortuitum/chelonei

The organism that is a significant isolate in cystic fibrosis patients is:

Burkholderia cepacia

Normal flora of a sputum specimen may include:

Haemophilus aphrophilus, Strep viridans, non-pathogenic Neisseria

A slow-growing acid fast bacillus has been isolated from the sputum of an HIV patient. The growth is non-photochromogenic, niacin negative, tellurite positive, and resistant to most antimycobacterial antibiotics. which of the following best fits this description

Mycobacterium avium complex

Which of the following is the best method of obtaining a sputum specimen devoid of contaminating upper respiratory tract flora:

Transtracheal aspiration

A sputum sample was submitted for culture. The direct smear revealed many WBC/LPF < 5 Epithelial cells/LPF many gram negative rods moderate gram positive cocci in chains and clusters and few gram negative diplococci. The culture would most likely reveal:

Significant growth of a gram negative rod

The Scotochromogens are acid-fast organisms belonging to:

Group II pigmented in the light and dark