Microbiology Test

The aseptic collection of blood cultures requires that the skin be cleansed with:

When cleansing the skin with alcohol and then iodine for the collection of a blood culture, the iodine (or iodophor) should remain intact on the skin for at least:

What is the purpose of adding 0.025%–0.050% sodium polyanetholsulfonate (SPS) to nutrient broth media for the collection of blood cultures?

A flexible calcium alginate nasopharyngeal swab is the collection device of choice for recovery of which organism from the nasopharynx?

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

Select the method of choice for recovery of anaerobic bacteria from a deep abscess.

7. Select the primary and differential media of choice for recovery of most fecal pathogens.

8. Select the media of choice for recovery of Vibrio cholerae from a stool specimen.

Colistin–nalidixic acid agar (CNA) is used primarily for the recovery of:

10. In the United States, most blood agar plates are prepared with 5% or 10% red blood cells (RBCs) obtained from:

All of the following are appropriate when attempting to isolate N. gonorrhoeae from a genital specimen except:

Chocolate agar and modified Thayer–Martin agar are used for the recovery of:

Cycloserine–cefoxitin-fructose agar (CCFA) is used for the recovery of:

Deoxycholate agar (DCA) is useful for the isolation of:

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

A sheep blood agar plate is used as a primary isolation medium when all of the following organisms are to be recovered from a wound specimen except:

Prereduced and vitamin K1-supplemented blood agar plates are recommended isolation media for:

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

Specimens for virus culture should be transported in media containing:

Cerebrospinal fluid (CSF) should be cultured immediately, but if delayed the specimen should be:

The most sensitive method for the detection of β-lactamase in bacteria is by the use of:

The breakpoint of an antimicrobial drug refers to:

Which of the following variables may change the results of an MIC?

According to the Kirby–Bauer standard antimicrobial susceptibility testing method, what should be done when interpreting the zone size of a motile, swarming organism such as a Proteus species?

Which class of antibiotics is used for the treatment of serious gram-negative infections as well as infections with Mycobacterium tuberculosis?

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

A suspected case of plague requires which of the following procedures in order to confirm Yersinia pestis?

SITUATION: Abdominal pain, fever, vomiting, and nausea prompted an elderly male to seek medical attention. A watery stool specimen producing no fecal leukocytes or erythrocytes was cultured and grew a predominance of gram-negative fermentative bacilli. The colonies were beta-hemolytic on blood agar and cream
colored on MacConkey agar. The colonies were both oxidase and catalase positive. What is the most likely identification?

29. SITUATION: Several attendees of a medical conference in the Gulf coast area became ill after frequenting a seafood restaurant. A presumptive identification of Vibrio cholera was made after stool specimens from several subjects grew clear colonies on MacConkey agar and yellow colonies on TCBS agar. Which key tests would help eliminate Aeromonas and Plesiomonas spp.?

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?

Biochemically, the Enterobacteriaceae are gram-negative rods that:

The ortho-nitrophenyl-β-galactopyranoside (ONPG) test is most useful when differentiating:

he Voges–Proskauer (VP) test detects which end product of glucose fermentation?

At which pH does the methyl red (MR) test become positive?

A positive Simmons citrate test is seen as a:

In the test for urease production, ammonia reacts to form which product?

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

Decarboxylation of the amino acids lysine, ornithine, and arginine results in the formation of:

Lysine iron agar (LIA) showing a purple slant and a blackened butt indicates:

Putrescine is an alkaline amine product of which bacterial enzyme?

Which genera are positive for phenylalanine deaminase?

Kligler iron agar (KIA) differs from triple-sugar iron agar (TSI) in the:

The malonate test is most useful in differentiating which members of the Enterobacteriaceae?

Which genera of the Enterobacteriaceae are known to cause diarrhea and are considered enteric pathogens?

An isolate of E. coli recovered from the stool of a patient with severe bloody diarrhea should be tested for which sugar before sending it to a reference laboratory for serotyping?

Care must be taken when identifying biochemical isolates of Shigella because serological cross reactions occur with:

Which species of Shigella is most commonly associated with diarrheal disease in the United States?

Which of the following tests best differentiates Shigella species from E. coli?

Which genera of Enterobacteriaceae are usually nonmotile at 36°C?

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:

Cold enrichment of feces (incubation at 4°C) in phosphate-buffered saline prior to subculture onto enteric media enhances the recovery of:

Which group of tests, along with colonial morphology on primary media, aids most in the rapid identification of the Enterobacteriaceae?

A routine, complete stool culture procedure should include media for the isolation of E. coli O157:H7 as well as:

Which group of tests best identifies the Morganella and Proteus genera?

Which group of tests best differentiates Enterobacter aerogenes from Edwardsiella tarda?

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

Members of the genus Cedecea are best differentiated from Serratia spp. by which test result?

Which of the following organisms is often confused with the Salmonella species biochemically and on plated media?

A gram-negative rod is recovered from a catheterized urine sample from a nursing home
patient. The lactose-negative isolate tested positive for indole, urease, ornithine decarboxylase, and phenylalanine deaminase and negative for H2S. The most probable identification is:

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

Which of the following organisms, found in normal fecal flora, may be mistaken biochemically for the genus Yersinia?

Why might it be necessary for both pink (lactose-positive) and colorless (lactose-negative) colonies from an initial stool culture on MacConkey agar to be subcultured and tested further for possible pathogens?

Which agar that is used for routine stool cultures is the medium of choice for the isolation of Yersinia strains from stool specimens?

Which organism is sometimes mistaken for Salmonella and will agglutinate in Salmonella polyvalent antiserum?

A bloody stool cultured from a 26-year-old woman after 3 days of severe diarrhea showed the following results at 48 hours after being plated on the following media:

MacConkey agar: little normal flora with many non–lactose-fermenting colonies
Hektoen enteric agar: many blue-green colonies
Campylobacter blood agar and C. difficile agar: no growth
Clear colonies (from MacConkey agar) tested negative for oxidase, indole, urease, motility, and H2S

The most likely identification is:

Which of the following organisms are generally positive for β-galactosidase?

In the Kauffmann–White schema, the combined antigens used for serological identification of the Salmonella spp. are:

The drugs of choice for treatment of infections with Enterobacteriaceae are:

The Shiga-like toxin (verotoxin) is produced mainly by which Enterobacteriaceae?

Infections caused by Yersinia pestis are rare in the United States. Those cases that do occur are most frequently located in which region?

A leg culture from a nursing home patient grew gram-negative rods on MacConkey agar as pink to dark pink oxidase-negative colonies. Given the following results, which is the most likely organism?

TSI = A/A
Indole = Neg
MR = Neg
VP = +
Citrate = +
H2S = Neg
Urease = +
Motility = Neg

Antibiotic susceptibility: resistant to carbenicillin and ampicillin

Four blood cultures were taken over a 24-hour period from a 20-year-old woman with severe diarrhea. The cultures grew motile (room temperature), gram-negative rods. A urine specimen obtained by catheterization also showed gram-negative rods, 100,000 col/mL. Given the following results, which is the most likely organism?

TSI = A/A gas
Indole = +
VP = Neg
MR = +
H2S = Neg
Citrate = Neg
Urease = Neg
Lysine decarboxylase = +
Phenylalanine deaminase = Neg

A stool culture from a 30-year-old man suffering from bloody mucoid diarrhea gave the following results on differential enteric media:

MacConkey agar = clear colonies
XLD agar = clear colonies
Hektoen agar = green colonies
Salmonella–Shigella agar = small, clear colonies

Which tests are most appropriate for identification of this enteric pathogen?

A leg-wound culture from a hospitalized 70-year-old diabetic man grew motile, lactose-negative colonies on MacConkey agar. Given the following biochemical reactions at 24 hours, what is the most probable organism?

H2S (TSI) = Neg
Indole = Neg
MR = Neg
VP = +
DNase = +
Citrate = +
Urease = Neg

Phenylalanine deaminase = Neg
Ornithine and lysine decarboxylase = +
Arginine decarboxylase = Neg
Gelatin hydrolysis = +

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 the most likely organism?

H2S (TSI) = +
Indole = +
MR = +
VP = Neg
Citrate = Neg
Urease = +
DNase = +
Phenylalanine deaminase = +
Gelatin hydrolysis = +
Ornithine decarboxylase = Neg

Three consecutive stool cultures from a 25-year-old male patient produced scant normal fecal flora on MacConkey and Hektoen agars. However, colonies on CIN agar (cefsulodin–irgasan–novobiocin) displayed “bulls-eye” colonies after 48 hours incubation. The patient had been suffering from enterocolitis with fever, diarrhea, and abdominal pain for 2 days. What is the most likely identification of this gram-negative rod?

A 6-year-old female patient was admitted to the hospital following 2 days of severe diarrhea. Cultures from three consecutive stool samples contained blood and mucus. Patient history revealed a hamburger lunch at a fast-food
restaurant 3 days earlier. Which pathogen is most likely responsible for the following results?

Growth on:
XLD agar = yellow colonies
HE agar = yellow colonies
Mac agar = light pink and dark pink colonies
Mac with sorbitol agar – few dark pink and many colorless colonies

A leg culture from a nursing home patient grew gram-negative rods on MacConkey agar as pink to dark pink oxidase-negative colonies. Given the following results, which is the most likely organism?

TSI = A/A
Indole = Neg
MR = Neg
VP = +
Citrate = +
H2S = Neg
Urease = +
Motility = Neg
Antibiotic susceptibility: resistant to carbenicillin and ampicillin

Four blood cultures were taken over a 24-hour period from a 20-year-old woman with severe diarrhea. The cultures grew motile (room temperature), gram-negative rods. A urine specimen obtained by catheterization also showed
gram-negative rods, 100,000 col/mL. Given the following results, which is the most likely organism?

TSI = A/A gas
Indole = +
VP = Neg
MR = +
H2S = Neg
Citrate = Neg
Urease = Neg
Lysine decarboxylase = +
Phenylalanine deaminase = Neg

A stool culture from a 30-year-old man suffering from bloody mucoid diarrhea gave the following results on differential enteric media:

MacConkey agar = clear colonies;
XLD agar = clear colonies;
Hektoen agar = green colonies;
Salmonella–Shigella agar = small, clear colonies

Which tests are most appropriate for identification of this enteric pathogen?

A leg-wound culture from a hospitalized 70-year-old diabetic man grew motile,
lactose-negative colonies on MacConkey agar. Given the following biochemical reactions at 24 hours, what is the most probable organism?

H2S (TSI) = Neg
Indole = Neg
MR = Neg
VP = +
DNase = +
Citrate = +
Urease = Neg
Phenylalanine deaminase = Neg
Ornithine and lysine decarboxylase = +
Arginine decarboxylase = Neg
Gelatin hydrolysis = +