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

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

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

Putrescine is an alkaline amine product of which bacterial enzyme?

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

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

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

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

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:

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

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

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

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

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

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

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

The drugs of choice for treatment of infections with Enterobacteriaceae are:A. Aminoglycosides, trimethoprim–sulfamethoxazole, third-generation cephalosporins

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

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?

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?

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?

Following a 2-week camping trip to the Southwest (US), a 65-year-old male patient was hospitalized with a high fever and an inflammatory swelling of the axilla and groin lymph nodes. Several blood cultures were obtained, resulting in growth of gram-negative rods resembling “closed safety pins.” The organism grew on MacConkey’s agar showing non–lactose-fermenting colonies. Testing demonstrated a nonmotile rod that was biochemically inert. What is the most likely identification?

Direct spread of pneumonic plague disease occurs by which route?