A patient with a peptic ulcer was admitted to the hospital and a gastric biopsy was performed. The tissue was cultured on a chocolate agar, incubated in a micraerophilic environment at 37 F for 5 to 7 days. At 5 days of incubation, colonies appeared on the plate and were curved, Gram-negative rods, oxidase-positive. The most likely identity of this organism is

An experimental compound is discovered that prevents the activation of adenyl cyclase and the resulting increase in cyclic AMP. The toxic effects of which of the following

An inhibitor was designed to block a biologic function in H. influenzae. If the goal of the experiment was to reduce the virulence of H. influenzae, the most likely target would be

A 21-year-old college student complained of malaise, low-grade fever, and a harsh cough, but not of muscle aches and pains. An x-ray revealed a diffuse interstitial pneumonia in the left lobes of the lung. The WBC count was normal. The student has been ill for a week.
Based on the information given, the most likely diagnosis is

There are millions of cases of leprosy (Hansen’s disease) worldwide, but predominately in Asia and Africa. The clinical spectrum of Hansen’s disease is best characterized by

At a church supper in Nova Scotia, the following meal was served: baked beans, ham, coleslaw, eclairs, and coffee. Of the 30 people who attended, 4 senior citizens became ill in 3 days; 1 eventually died. Two weeks after attending the church supper, a 19-year-old girl gave birth to a baby who rapidly became ill with meningitis and died in 5 days. Epidemiologic investigation revealed the following percentages of people who consumed the various food items: baked beans, 30%; ham, 80%; coleslaw, 60%; eclairs, 100%; and coffee, 90%. Which of the following statements is true?

Microbiologic analysis revealed no growth in the baked beans, ham,
or coffee; many Gram-positive beta-hemolytic, short, rod-shaped bacteria
in the coleslaw; and rare Gram-positive cocci in the eclairs. The most likely
cause of this outbreak is

A 21-year-old college student complained of malaise, low-grade fever, and a harsh cough, but not of muscle aches and pains. An x-ray revealed a diffuse interstitial pneumonia in the left lobes of the lung. The WBC count was normal. The student has been ill for a week.
Based on the information given, which of the following laboratory tests would most rapidly assist you in making the diagnosis?

A 21-year-old college student complained of malaise, low-grade fever, and a harsh cough, but not of muscle aches and pains. An x-ray revealed a diffuse interstitial pneumonia in the left lobes of the lung. The WBC count was normal. The student has been ill for a week.
The following laboratory data were available within 2 days: cold agglutinins—negative; complement fixation (M. pneumoniae)—1:64; viral culture—pending, but negative to date; bacterial culture of sputum on blood agar and MacConkey’s agar—normal oral flora. In order to confirm the diagnosis, which of the following procedures could be ordered to achieve a specific and sensitive diagnosis?

Pathogenic mechanisms involved in tuberculosis can be primarily attributed to which of the following?

The class of antibiotics known as the quinolones are bactericidal. Their mode of action on growing bacteria is thought to be

Vancomycin-indeterminate S. aureus (VISA) has recently been reported in the United States. Which one of the statements concerning VISA is the most correct?

A sputum sample was brought to the laboratory for analysis. Gram stain revealed the following: rare epithelial cells, 8 to 10 polymorphonuclear leukocytes per high-power field, and pleomorphic Gram-negative rods. As the laboratory consultant, which of the following interpretations should you make?

An isolate from a wound culture is a Gram-negative rod identified as Bacteroides fragilis. Anaerobic infection with B. fragilis is characterized by

Virtually all prokaryotic cells (bacteria, both Gram-positive and Gramnegative) contain peptidoglycan as well as specific enzymes for its synthesis. All of the following statements concerning Gram-positive and Gram-negative bacteria are true except

L. monocytogenes causes a variety of diseases, including food poisoning. Listeria are small, Gram-positive, motile rod-shaped bacteria. Which of the following best describes these microorganisms?

A 30-year-old male patient was seen by the emergency service and reported a 2-week history of a penile ulcer. He noted that this ulcer did not hurt. Which one of the following conclusions/actions is most valid?

A 30-year-old male patient was seen by the emergency service and reported a 2-week history of a penile ulcer. He noted that this ulcer did not hurt. The laboratory reports that the Venereal Disease Research Laboratory (VDRL) test performed on the above patient is reactive at a dilution of 1:4 (4 dils). The patient also reports to you that he has recently been diagnosed with hepatitis A. Which one of the following actions would be most appropriate?

A 30-year-old male patient was seen by the emergency service and reported a 2-week history of a penile ulcer. He noted that this ulcer did not hurt. The laboratory reports that the Venereal Disease Research Laboratory (VDRL) test performed on the above patient is reactive at a dilution of 1:4 (4 dils). The patient also reports to you that he has recently been diagnosed with hepatitis A. Which one of the following test combinations for syphilis is most appropriate?

Assume that the patient absolutely denied any contact, sexual or otherwise, with a person who had syphilis. Assume also that both the RPR and the FTA Abs were positive on this patient. Which one of the following tests could be used to show that this patient probably does not have syphilis?

A 55-year-old man who is being treated for adenocarcinoma of the lung is admitted to a hospital because of a temperature of 38.9°C (102°F), chest pain, and a dry cough. Sputum is collected. Gram’s stain of the sputum is unremarkable and culture reveals many small Gram-negative rods able to grow only on a charcoal yeast extract agar. This organism most likely is

A patient was hospitalized after an automobile accident. The wounds became infected and the patient was treated with tobramycin, carbenicillin, and clindamycin. Five days after antibiotic therapy was initiated, the patient developed severe diarrhea and pseudomembranous enterocolitis. Antibiotic-associated diarrhea and the more serious pseudomembranous enterocolitis can be caused by

Assuming that the average achievable serum level of gentamicin is 6 to 8 mcg/mL, which of the following bacteria is susceptible to gentamicin?

A child comes to an emergency room because of an infected dog bite. The wound is found to contain small Gram-negative rods. The most likely cause of infection is

A patient complained to his dentist about a draining lesion in his mouth. A Gram’s stain of the pus showed a few Gram-positive cocci, leukocytes, and many branched Gram-positive rods. The most likely cause of the disease is

A man who has a penile chancre appears in a hospital’s emergency service. The VDRL test is negative. The most appropriate course of action for the physician in charge would be to

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

Cholera is a toxicogenic dysenteric disease common in many parts of the world. In the treatment of patients who have cholera, the use of a drug that inhibits adenyl cyclase would be expected to

A box of ham sandwiches with mayonnaise prepared by a person with a boil on his neck was left out of the refrigerator for the on-call interns. Three doctors became violently ill approximately 2 h after eating the sandwiches. The most likely cause is

S. aureus causes a wide variety of infections, ranging from wound infection to pneumonia. Treatment of S. aureus infection with penicillin is often complicated by the

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

In people who have sickle cell anemia, osteomyelitis usually is associated with which of the following organisms?

The treatment of choice for a patient with C. jejuni enterocolitis is

A hyperemic edema of the larynx and epiglottis that rapidly leads to respiratory obstruction in young children is most likely to be caused by

A 70-year-old female patient was readmitted to a local hospital with fever and chills following cardiac surgery at a major teaching institution. Blood cultures were taken and a Gram-positive coccus grew from the blood cultures within 24 hours. Initial tests indicated that this isolate was resistant to penicillin. The most likely identification is

Acute hematogenous osteomyelitis is often diagnosed by isolation of the organism from the blood and is caused most often by

Diphtheria toxin is produced only by those strains of C. diphtheriae that are

A 28-year-old menstruating woman appeared in the emergency room with the following signs and symptoms: fever, 104°F (40°C); WBC, 16,000/ μL; blood pressure, 90/65 mmHg; a scarlatiniform rash on her trunk, palms, and soles; extreme fatigue; vomiting; and diarrhea.
The patient described in the case above most likely has

Culture of the menstrual fluid in the case of a woman with Toxic Shock Syndrome (TSS) would most likely reveal a predominance of

A new latex agglutination (LA) reagent for H. influenzae polysaccharide antigen in cerebrospinal fluid was evaluated. Results were compared with the isolation of H. influenzae from the CSF. Results were as follows:
LA POS, CULT POS: 25
LA POS, CULT NEG: 5
LA NEG, CULT POS: 5
LA NEG, CULT NEG: 95
The sensitivity of LA is

A new latex agglutination (LA) reagent for H. influenzae polysaccharide antigen in cerebrospinal fluid was evaluated. Results were compared with the isolation of H. influenzae from the CSF. Results were as follows:
LA POS, CULT POS: 25
LA POS, CULT NEG: 5
LA NEG, CULT POS: 5
LA NEG, CULT NEG: 95
The specificity of LA is

A new latex agglutination (LA) reagent for H. influenzae polysaccharide antigen in cerebrospinal fluid was evaluated. Results were compared with the isolation of H. influenzae from the CSF. Results were as follows:
LA POS, CULT POS: 25
LA POS, CULT NEG: 5
LA NEG, CULT POS: 5
LA NEG, CULT NEG: 95
The negative predictive value of LA is

The incidence of H. influenzae meningitis in the general population is less than 1%. If during an epidemic the incidence rose to 3%, the negative predictive value of the LA test would

Methicillin-resistant S. aureus (MRSA) was isolated from 7 patients in a 14-bed intensive care unit. All patients were isolated and the unit closed to any more admissions. Which one of the following reasons best explains these rigorous methods to control MRSA?

A patient with AIDS returned from Haiti with acute diarrhea. The stool revealed an oval organism (8 to 9 μm in diameter) that was acid-fast and fluoresced blue under ultraviolet light. The most likely identification of this organism is

A 2-year-old infant is brought to the emergency room with hemolytic uremic syndrome and thrombocytopenia. Which one of the following bacteria would most likely be isolated from a stool specimen?

E. coli causes disease by a variety of different methods. Which one of the following E. coli types is characterized by the presence of LT (heat-labile) and ST (heat-stable) proteins?

Yersinia pestis, the causative agent of plague, is enzootic in the United States west of the one-hundredth meridian. Human plague can be bubonic or pneumonic. The primary epidemiologic difference between the two clinical forms of plague is

A 9-year-old child is brought to the emergency room with the chief complaint of enlarged, painful axillary lymph nodes. The resident physician also notes a small, inflamed, dime-sized lesion surrounding what appears to be a small scratch on the forearm. The lymph node is aspirated and some pus is sent to the laboratory for examination. A Warthin-Starry silver impregnation stain reveals many highly pleomorphic, rod-shaped bacteria. The most likely cause of this infection is

Recently, there have been sensational media reports of patients infected with invasive, “flesh-eating” bacteria that spread rapidly through the tissues. This necrotizing fasciitis is usually caused by

The most effective noninvasive test for the diagnosis of Helicobacter-associated gastric ulcers is

The following test results were observed in a woman tested in November who reported being in the woods in Pennsylvania during the past summer, was bitten by a tick, and now has Bell’s palsy: Lyme IgG antibody 1:1280; Lyme IgM antibody negative. Which one of the following courses of action is most appropriate?

Mycobacterium avium is a major opportunistic pathogen in AIDS patients. M. avium from AIDS patients can be best characterized by which one of the following statements?

Rheumatic fever (RF) is a disease seen in children and young adults. Which one of the following statements best typifies the disease?

Bacteria cause disease in a number of ways. One mechanism of pathogenesis is the secretion of potent protein toxins. All the following diseases are caused by microbial protein toxins, but one toxin has been used for a variety of maladies. It is

A 2-year-old child was admitted to the hospital with acute meningitis. The Gram stain revealed Gram-positive short rods, and the mother indicated that the child had received “all” of the meningitis vaccinations. What is the most likely cause of the disease?

The most common portal of entry for C. tetani, the cause of tetanus, is the

The most common way in which tuberculosis is acquired is via the

Shigellosis is common in travelers to developing countries. Infection is commonly acquired through the

A person who contracts gonorrhea is most likely to have acquired it via the

There are a variety of “unusual” bacteria that infect humans. While rare, disease caused by these microorganisms is serious and occasionally difficult to identify. Branhamella is best characterized as

Cardiobacterium is best characterized as

Capnocytophyga is best characterized as

An enterococcus (E. faecium) was isolated from a urine specimen (100,000 cfu/mL). Treatment of the patient with ampicillin and gentamicin failed. The most clinically appropriate action is

A patient with symptoms of urinary tract infection had a culture taken, which grew 5 × 103 E. coli. The laboratory reported it as “insignificant.” The most clinically appropriate action is

A patient appeared in the emergency room with a submandibular mass. A smear was made of the drainage and a bewildering variety of bacteria were seen, including branched, Gram-positive rods. The most clinically appropriate action is

The antibiotic therapy of choice for legionellosis is

The antibiotic of choice for pneumococcal pneumonia is

The antibiotic of choice for Lyme disease is

The antibiotic of choice for streptococcal pharyngitis is

The therapy of choice for pseudomembranous enterocolitis is

C. jejuni is best described as

V. cholerae, the causative agent of cholera, is best described as

V. parahaemolyticus, first described in Japan, is best characterized as

Vibrio vulnificus, which can be found in the oceans and bays in temperate and tropical climates, is best characterized as

Y. enterocolitica, formerly a Pasteurella, is best described by which of the following statements?

Brucella abortus, one of the three species causing brucellosis, a possible bioterrorism agent, is best described by which of the following statements?