MICRO FINALS 9,10,11,12,18

(C) During placement of the central venous catheter

The most likely portal of entry for the organism in Question 14 is (A) During gynecologic surgery (B) Aspiration (C) During placement of the central venous catheter (D) During placement of IV line for administration of antibiotics (E) Intubation while under anesthesia

(E) S. aureus

The organism most likely to be responsible for the patient's disease (Question 6) is (A) E. coli (B) C. diphtheriae (C) C. perfringens (D) N. meningitidis (E) S. aureus

(E) Inactivation of elongation factor 2

The primary mechanism in the pathogenesis of the boy's disease (Question 4) is (A) A net increase in intracellular cyclic adenosine monophosphate (B) Action of pyrogenic exotoxin (a superantigen) (C) Inactivation of acetylcholine esterase (D) Action of enterotoxin A (E) Inactivation of elongation factor 2

(D) 6 weeks

The reported incubation period for inhalational anthrax can be up to (A) 2 days (B) 10 days (C) 3 weeks (D) 6 weeks (E) 6 months

(D) Nocardia species

Three months ago, a 53-year-old woman had surgery and chemotherapy for breast cancer. Four weeks ago, she developed a cough occasionally productive of purulent sputum. About 2 weeks ago, she noted a slight but progressive weakness of her left arm and leg. On chest examination, rales were heard over the left upper back when the patient breathed deeply. Neurologic examination confirmed weakness of the left arm and leg. Chest radiography showed a left upper lobe infiltrate. Contrast- enhanced computed tomography showed two lesions in the right hemisphere. Gram-stain of a purulent sputum specimen showed branching Gram-positive rods that were partially acid fast. Which of the following organisms is the cause of this patient's current illness? (A) Actinomyces israelii (B) Corynebacterium ulcerans (C) Aspergillus fumigatus (D) Nocardia species (E) Erysipelothrix rhusiopathiae

(A) Nocardia brasiliensis

Which of the following aerobic Gram-positive bacilli is modified acid-fast positive? (A) Nocardia brasiliensis (B) Lactobacillus acidophilus (C) Erysipelothrix rhusiopathiae (D) Listeria monocytogenes

(D) Inhibits elongation factor 2

Which of the following best describes the mechanism of action of diphtheria toxin? (A) Forms pores in red blood cells causing hemolysis (B) Degrades lecithin in eukaryotic cell membranes (C) Causes release of tumor necrosis factor (D) Inhibits elongation factor 2 (E) Causes increased adenylate cyclase activity

(D) Honey

Which of the following food items is most frequently associated with infant botulism? (A) Corn syrup (B) Canned infant formula (C) Liquid multivitamins (D) Honey (E) Jarred baby food

(A) Airway colonization in a cystic fibrosis patient with a mucoid (alginate-producing) strain of P. aeruginosa

Which of the following is most likely to be associated with the formation of a bacterial biofilm? (A) Airway colonization in a cystic fibrosis patient with a mucoid (alginate-producing) strain of P. aeruginosa (B) Urinary tract infection with E. coli (C) Meningitis with N. meningitidis (D) Tetanus (E) Impetigo caused by S. aureus

(A) Heat-labile toxin

Which of the following is not a recognized virulence factor of B. pertussis? (A) Heat-labile toxin (B) Filamentous hemagglutinin (C) Tracheal cytotoxin (D) Pertussis toxin (E) Dermonecrotic toxin

(D) F. tularensis

Which of the following pathogens discussed in this chapter is on the select agent list? (A) H. influenzae (B) A. aphrophilus (C) B. pertussis (D) F. tularensis (E) All of the above

(A) It interacts with macrophages and monocytes yielding release of cytokines.

Which of the following statements about lipopolysaccharide is correct? (A) It interacts with macrophages and monocytes yielding release of cytokines. (B) The toxic component is the O side chain. (C) It forms holes in red blood cell membranes yielding hemolysis. (D) It causes hypothermia. (E) It causes paralysis.

(B) A toxin with A and B subunits

A 15-year-old Bangladeshi girl develops severe watery diarrhea. The stool looks like "rice water." It is voluminous—more than 1 L in the last 90 minutes. She has no fever and seems otherwise normal except for the effects of loss of fluid and electrolytes. The most likely cause of her illness is (A) Clostridium difficile enterotoxin (B) A toxin with A and B subunits (C) S. dysenteriae type 1 that produces Shiga toxin (D) Enterotoxigenic E. coli that produces heat-labile and heat stable toxins (E) Staphylococcal enterotoxin F

(E) Breathing aerosolized droplets containing the microorganism

A 22-year-old woman who works in a plant nursery presents with a history of fever and cough for 2 months. Over this period of time she has lost 5 kg. Chest radiography shows bilateral upper lobe infiltrates with cavities. A stain of her sputum shows acid-fast bacilli. The likely means by which the patient acquired her infection is (A) Sexual activity (B) Ingesting the microorganisms in her food (C) Holding onto contaminated hand rails when she takes public transportation (D) Handling potting soil (E) Breathing aerosolized droplets containing the microorganism

(D) E. coli with P-pili (fimbriae)

A 23-year-old woman has a history of recurrent urinary tract infections, including at least one episode of pyelonephritis. Blood typing shows the P blood group antigen. Which of the following is likely to be the primary cause of her infections? (A) E. coli that produce heat-stable toxin (B) E. coli with K1 (capsular type 1) antigen (C) E. coli O139 (lipopolysaccharide O antigen 139) (D) E. coli with P-pili (fimbriae) (E) E. coli O157:H7 (lipopolysaccharide O antigen 157; flagellar antigen 7)

(E) Lactobacillus species

A 26-year-old woman visits her physician because of an unusual vaginal discharge. On examination, the physician observes a thin, homogeneous, white-gray discharge that adheres to the vaginal wall. The pH of the discharge is 5.5 (normal, <4.3). On Gramstain, many epithelial cells covered with Gram-variable rods are seen. Bacterial vaginosis is diagnosed. Which one of the following normal genital flora microorganisms is greatly decreased in bacterial vaginosis? (A) Corynebacterium species (B) Staphylococcus epidermidis (C) Prevotella species (D) Candida albicans (E) Lactobacillus species

(C) A toxin that is a superantigen

A 27-year-old man had a rhinoplasty. A nasal tampon was placed to control the bleeding. Approximately 8 hours later, he developed headache, muscle aches, and abdominal cramps with diarrhea. He then developed an erythematous rash (resembling sunburn) over much of his body, including the palms and soles. His blood pressure is 80/50 mm Hg. The nasal tampon remained in place. His liver enzyme tests were elevated, and there was evidence of moderate renal failure. This patient's illness was likely to be caused by which of the following? (A) Lipopolysaccharide (B) Peptidoglycan (C) A toxin that is a superantigen (D) A toxin that has A and B subunits (E) Lecithinase (alpha toxin)

(B) B. pertussis

A 3-month-old infant is brought to the pediatric emergency department in severe respiratory distress. The child appears dehydrated, and there is a prominent peripheral lymphocytosis. The chest radiograph reveals perihilar infiltrates. The child's grandmother, who watches the infant now that the mother has returned to work, has had a dry hacking cough for about 2 weeks. The most likely causative agent is (A) H. influenzae type b (B) B. pertussis (C) Streptococcus agalactiae (D) C. pneumoniae (E) B. bronchiseptica

(E) About 20% of H. influenzae organisms have a plasmid that encodes for β-lactamase

A 3-year-old child develops H. influenzae meningitis. Therapy is begun with cefotaxime. Why is this third generation cephalosporin used rather than ampicillin? (A) About 80% of H. influenzae organisms have modified penicillin- binding proteins that confer resistance to ampicillin. (B) The drug of choice, trimethoprim-sulfamethoxazole, cannot be used because the child is allergic to sulfonamides. (C) It is easier to administer intravenous cefotaxime than intravenous ampicillin. (D) There is concern that the child will rapidly develop a penicillin (ampicillin) allergy. (E) About 20% of H. influenzae organisms have a plasmid that encodes for β-lactamase

(B) Erysipelothrix rhusiopathiae

A 45-year-old fisherman imbedded a fishhook into his right forefinger. He removed it and did not seek immediate medical therapy. Five days later, he noted fever, severe pain, and nodular-type swelling of the finger. He sought medical therapy. The violaceous nodule was aspirated, and after 48 hours of incubation, colonies of a Gram-positive bacillus that caused greenish discoloration of the agar and formed long filaments in the broth culture were noted. The most likely cause of this infection is (A) Lactobacillus acidophilus (B) Erysipelothrix rhusiopathiae (C) Listeria monocytogenes (D) Rhodococcus equi (E) Nocardia brasiliensis

(D) Tetanus

A 45-year-old man who immigrated to the United States 5 years ago sustained a puncture injury to the lower part of his right leg when his rotary lawn mower threw a small stick into his leg. Six days later, he noticed spasms in the muscles of his right leg; on day 7, the spasms increased. Today—day 8—he had generalized muscle spasms, particularly noticeable in the muscles of his jaw. He was unable to open his jaw and came to the emergency department (ED). In the ED, you see a man who is alert and lying quietly in bed. A door slams down the hall, and suddenly he has general muscle spasm with arching of his back. The correct diagnosis is which of the following? (A) Botulism (B) Anthrax (C) Gas gangrene (D) Tetanus (E) Toxic shock syndrome

(E) F. tularensis

A 55-year-old game warden in Vermont found a dead muskrat on the bank of a stream. He picked up the animal, thinking it might have been illegally trapped or shot; it was not, and the game warden buried it. Four days later, he developed a 1.5-cm painful ulcer on the index finger of his right hand, a 1-cm ulcer on his right forehead, and pain in his right axilla. Physical examination also revealed right axillary lymphadenopathy. This patient is most likely infected with (A) Brucella species (B) Rickettsia rickettsii (C) Salmonella Typhi (D) H. ducreyi (E) F. tularensis

(B) Polymerase chain reaction amplification and sequencing of an appropriate segment of DNA

A 55-year-old man presents with gradually increasing weight loss, abdominal pain, diarrhea, and arthropathy. During the evaluation process, a small bowel biopsy is done. After processing, examination of the specimen by light microscopy reveals periodic acid-Schiff-positive inclusions in the bowel wall. Which of the following tests could be done to confirm the diagnosis of Whipple disease caused by T. whipplei? (A) Culture on agar media (B) Polymerase chain reaction amplification and sequencing of an appropriate segment of DNA (C) Cocultivation with E. coli (D) In situ hybridization (E) Direct fluorescent antibody test

(C) A. aphrophilus

A 55-year-old man with severe dental caries presented with 1 month of fever, malaise, and back pain and now presents with moderately severe shortness of breath. The examination reveals a febrile man who appears pale and dyspneic. Other physical findings include conjunctival petechiae, a grade III/VI systolic murmur, and an enlarged spleen. Blood cultures grow a pleomorphic Gram-negative rod that is not hemolytic and that when tested is X and V factor negative. The most likely causative pathogen is (A) H. influenzae (B) H. ducreyi (C) A. aphrophilus (D) Actinobacillus hominis (E) H. parainfluenzae

(E) The complex molecular interactions within the biofilm make it difficult to provide effective antimicrobial therapy, and it is likely the catheter will have to be removed to cure the infection

A 65-year-old woman has a long-term central venous catheter for intravenous therapy. She develops fever and subsequently has multiple blood cultures positive for S. epidermidis. All of the S. epidermidis isolates have the same colony morphology and antimicrobial susceptibility pattern, suggesting that they are the same strain. An S. epidermidis biofilm is thought to be present on the catheter. Which one of the following statements about such an infection is correct? (A) The biofilm containing the S. epidermidis is likely to wash off the catheter. (B) Production of an extracellular polysaccharide inhibits growth of the S. epidermidis, limiting the infection. (C) The S. epidermidis in the biofilm are likely to be more susceptible to antimicrobial therapy because the bacteria have decreased rates of metabolism. (D) The quorum-sensing ability of S. epidermidis results in increased susceptibility to antimicrobial therapy. (E) The complex molecular interactions within the biofilm make it difficult to provide effective antimicrobial therapy, and it is likely the catheter will have to be removed to cure the infection

(D) Candida albicans

A 65-year-old woman was admitted with squamous cell carcinoma of the cervix. She underwent extensive gynecologic surgery and was maintained postoperatively on broad-spectrum intravenous antibiotics. The patient had a central venous catheter placed on the day of surgery. Beginning 3 days postoperatively, the patient became febrile. On day 8, cultures of blood and of the tip of the central line both grew Gram-positive organisms that were ovoid and reproduced by budding. Which of the following microorganisms is most likely responsible for the patient's condition? (A) Staphylococcus aureus (B) Staphylococcus epidermidis (C) Enterococcus faecalis (D) Candida albicans (E) Saccharomyces cerevisae

(C) Clostridium difficile toxins

A 67-year-old man had surgery for a ruptured sigmoid colon diverticulum with an abscess. A repair was done, and the abscess was drained. He was treated with intravenous gentamicin and ampicillin. Ten days later and 4 days after being discharged from the hospital, the patient developed malaise, fever, and cramping abdominal pain. He had multiple episodes of diarrhea. His stool was positive for occult blood and the presence of polymorphonuclear cells. On sigmoidoscopy, the mucosa was erythematous and appeared to be inflamed, and there were many raised white to yellowish plaques 4-8 mm in diameter. Which of the following is the likely cause of the patient's problem? (A) Staphylococcus aureus enterotoxin (B) Bacillus cereus toxin (C) Clostridium difficile toxins (D) Clostridium perfringens toxin (E) Enterohemorrhagic Escherichia coli

(D) Brucella species

A 68-year-old woman was seen in the clinic because she had felt feverish and had been experiencing increasing pain and swelling in her left knee during the past 3 weeks. Four years earlier, a prosthetic joint had been placed in her left knee. On examination, the knee was swollen, and fluid could be detected. An aspirate of the fluid was obtained. There were 15,000 polymorphonuclear cells/mL in the fluid. No organisms were seen on Gram-stain. A routine culture was done. On the fourth day of incubation, colorless colonies smaller than 1 mm in diameter were seen on the blood and chocolate agar plates. The organism was a tiny Gram-negative coccobacillus that was catalase positive and oxidase positive. A urea slant was inoculated and was positive for urease activity after overnight incubation. The patient was probably infected with which of the following microorganisms? (A) H. influenzae (B) H. ducreyi (C) F. tularensis (D) Brucella species (E) Staphylococcus aureus

(A) Mixed normal gastrointestinal flora

A 70-year-old man with a history of diverticulosis of the sigmoid colon experiences a sudden onset of severe left lower quadrant abdominal pain. Fever develops. The severe pain gradually subsides and is replaced by a constant aching pain and marked abdominal tenderness. A diagnosis of probable ruptured diverticulum is made, and the patient is taken to the operating room. The diagnosis of ruptured diverticulum is confirmed, and an abscess next to the sigmoid colon is found. The most likely bacteria to be found in the abscess are (A) Mixed normal gastrointestinal flora (B) Bacteroides fragilis alone (C) Escherichia coli alone (D) Clostridium perfringens alone (E) Enterococcus species alone

(D) Normal oral nasal flora

A 9-year-old girl develops fever and severe pain on the right side of her throat. On examination, redness and swelling in the right peritonsillar area are seen. A peritonsillar abscess is diagnosed. The most likely organisms to be cultured from this abscess are (A) Staphylococcus aureus (B) Streptococcus pneumoniae (C) Corynebacterium species and Prevotella melaninogenica (D) Normal oral nasal flora (E) Viridans streptococci and Candida albicans

(E) Production of H2S

A biochemical reaction that is useful in the identification of the causative agent of the infection in Question 8 is (A) Catalase positivity (B) Acid fastness using modified Kinyoun stain (C) Esculin hydrolysis (D) Tumbling motility (E) Production of H2S

(A) Fried rice

A food commonly associated with Bacillus cereus food poisoning is (A) Fried rice (B) Baked potato (C) Hot freshly steamed rice (D) Green beans (E) Honey

(C) Botulism

A housewife who lives on a small farm is brought to the emergency department complaining of double vision and difficulty talking. Within the past 2 hours, she noted a dry mouth and generalized weakness. Last night she served home-canned green beans as part of the meal. She tasted the beans before they were boiled. None of the other family members are ill. On examination, there is symmetrical descending paralysis of the cranial nerves, upper extremities, and trunk. The correct diagnosis is which one of the following? (A) Tetanus (B) Strychnine poisoning (C) Botulism (D) Morphine overdose (E) Ricin intoxication

(E) Clostridium perfringens

A young man sustains major soft tissue injury and open fractures of his right leg after a motorcycle accident. One day later, he has a temperature of 38°C, increased heart rate, sweating, and restlessness. On examination, the leg is swollen and tense, with thin, dark serous fluid draining from the wounds. The skin of the leg is cool, pale, white, and shining. Crepitus can be felt in the leg. His hematocrit is 20% (∼50% of normal), and his circulating hemoglobin is normal. His serum shows free hemoglobin. Which of the following microorganisms is the most likely cause of this infection? (A) Clostridium tetani (B) Staphylococcus aureus (C) Escherichia coli (D) Bacillus anthracis (E) Clostridium perfringens

(B) Unpasteurized goat's cheese

After the culture (Question 1) turned positive, additional history was obtained. Approximately 4 weeks before the onset of her knee pain, the patient had visited relatives in Israel and traveled to other countries in the Mediterranean area. She had a particular fondness for one food product that was the probable vehicle for her infection. The product most likely was (A) Bananas (B) Unpasteurized goat's cheese (C) Rare hamburger (D) Fresh orange juice (E) Green tea

(C) B. pertussis

All of the following cause zoonotic infections except (A) F. tularensis (B) B. melitensis (C) B. pertussis (D) Bacillus anthracis (E) Leptospira interrogans

(D) The vaccine is approved only for young children and adolescents.

All of the following statements regarding acellular pertussis vaccines are correct except (A) All formulations of the vaccine contain at least two antigens. (B) The acellular vaccine has replaced the whole cell vaccine in the childhood vaccine series. (C) All children should receive five doses of the vaccine before school entry. (D) The vaccine is approved only for young children and adolescents. (E) The vaccine is safer than and as immunogenic as whole cell vaccines.

(C) The organism grows well on standard chocolate agar.

All of the following statements regarding the etiologic agent of chancroid are correct except (A) The organism is a small Gram-negative rod. (B) The organism requires X factor but not V factor. (C) The organism grows well on standard chocolate agar. (D) On Gram-stain of lesions, the organism occurs in strands. (E) The organism is susceptible to erythromycin.

(A) Brucella species

An 11-year-old boy from Peru was referred to the Brain Tumor Institute. Three months earlier he had developed headaches and then slowly progressive right-sided weakness. A CT scan showed a mass lesion in the left hemisphere. He was thought to have a brain tumor. A lumbar puncture was not done because of concern about increased intracranial pressure and brain herniation through the tentorium cerebelli. During surgery, a mass lesion in the left hemisphere was found. Frozen sections of the tissue were done while the patient was in the operating room. Microscopy of the sections showed a granulomatous inflammatory reaction. No tumor was seen. Tissue was submitted for culture for M. tuberculosis. Middlebrook 7H9 broth medium was used. Six days after the culture was set up, the automated machine detected that the culture result was positive. Results of an acid-fast stain and a Gram stain were both negative. Subcultures were done. Two days later, very small colonies were seen on the sheep blood agar plate. The organism was a tiny Gramnegative coccobacillus that was catalase positive and oxidase positive. It showed urease activity after 2 hours of incubation on urea-containing medium. This child had infection with (A) Brucella species (B) M. tuberculosis (C) F. tularensis (D) H. influenzae (E) Moraxella catarrhalis

(B) Infants 2 months to 2 years of age do not immunologically respond to polysaccharide vaccines that are not conjugated to a protein.

An 18-month-old boy has been playing with a child who develops H. influenzae meningitis. The boy's parents consult his pediatrician, who says she is comfortable that the child will be fine because he has been fully immunized with the poly ribitol ribose phosphate (PRP) protein conjugate vaccine. For what reason is it necessary to immunize infants of 2 months to 2 years of age with polysaccharide-protein conjugate vaccines? (A) The conjugate protein is diphtheria toxoid, and the goal is for the infant to develop simultaneous immunity to diphtheria. (B) Infants 2 months to 2 years of age do not immunologically respond to polysaccharide vaccines that are not conjugated to a protein. (C) The conjugate vaccine is designed for older children and adults as well as infants. (D) Maternal (transplacental) antibodies against H. influenzae are gone from the infant's circulation by 2 months of age. (E) None of the above.

(D) A club-shaped Gram-positive bacillus

An 8-year-old boy, who recently arrived in the United States, develops a severe sore throat. On examination, a grayish exudate (pseudomembrane) is seen over the tonsils and pharynx. The differential diagnosis of severe pharyngitis such as this includes group A streptococcal infection, Epstein-Barr virus (EBV) infection, Neisseria gonorrhoeae pharyngitis, and diphtheria. The cause of the boy's pharyngitis is most likely: (A) A Gram-negative bacillus (B) A single-stranded positive-sense RNA virus (C) A catalase-positive, Gram-positive coccus that grows in clusters (D) A club-shaped Gram-positive bacillus (E) A double-stranded RNA virus

(D) 108/g

Anaerobic bacteria such as Bacteroides fragilis occur in the sigmoid colon in a concentration of about 1011/g of stool. At what concentration do facultative organisms such as Escherichia coli occur? (A) 1011/g (B) 1010/g (C) 109/g (D) 108/g (E) 107/g

(D) Clostridium difficile

Antimicrobial therapy can decrease the amount of susceptible bowel flora and allow proliferation of relatively resistant colonic bacteria. Which one of the following species can proliferate and produce a toxin that causes diarrhea? (A) Enterococcus species (B) Staphylococcus epidermidis (C) Pseudomonas aeruginosa (D) Clostridium difficile (E) Bacteroides fragilis

(C) Mycobacterium tuberculosis

Certain microorganisms are never considered to be members of the normal flora. They are always considered to be pathogens. Which one of the following organisms fits into that category? (A) Streptococcus pneumoniae (B) Escherichia coli (C) Mycobacterium tuberculosis (D) Staphylococcus aureus (E) Neisseria meningitidis

(A) Biofilm formation

Dental plaque and periodontal disease can be thought of as a continuum of what type of physiological process? (A) Biofilm formation (B) Normal aging (C) Abnormal digestion (D) Exaggerated immune response (E) Chewing gum

(B) V. cholerae type O139 (lipopolysaccharide O antigen 139)

During a pandemic of a well-characterized disease, a group of 175 airline passengers flew from Lima, Peru, to Los Angeles. Lunch on the plane included crab salad, which was eaten by about two-thirds of the passengers. After landing in Los Angeles, many of the passengers transferred to other flights with destinations in other parts of California and other Western states. Two of the passengers who stayed in Los Angeles developed severe watery diarrhea. The status of the other passengers was unknown. The likely cause of the diarrhea in the two passengers is (A) E. coli O157:H7 (lipopolysaccharide O antigen 157; flagellar antigen 7) (B) V. cholerae type O139 (lipopolysaccharide O antigen 139) (C) Shigella dysenteriae type 1 (D) Campylobacter jejuni (E) Entamoeba histolytica

(C) Lecithinase

For the patient described in Question 3, which of the following is likely to be responsible for the hemolysis? (A) Elongation factor (B) Tetanospasmin (C) Lecithinase (D) Streptolysin O (E) Toxin B

(D) Helicobacter pylori

Hundreds of phylotypes have been identified in the human stomach; however, the only microorganism that has been shown to persist is (A) Lactobacillus casei (B) Lactobacillus acidophilus (C) Escherichia coli (D) Helicobacter pylori (E) Bifidobacteria

(C) An A/B structured toxin

In Question 11, the factor responsible for the profound lymphocytosis is (A) A hemagglutinin (B) A polysaccharide capsule (C) An A/B structured toxin (D) A heat-labile toxin

(D) All of the above are correct.

Listeria monocytogenes is frequently a foodborne pathogen because (A) It can survive at 4°C. (B) It survives under conditions of low pH. (C) It survives in the presence of high-salt concentrations. (D) All of the above are correct.

(A) Inducing host cell actin polymerization

Movement of Listeria monocytogenes inside of host cells is caused by (A) Inducing host cell actin polymerization (B) The formation of pili (fimbriae) on the listeriae surface (C) Pseudopod formation (D) The motion of listeriae flagella (E) Tumbling motility

(D) They directly inject bacterial proteins into host cells across bacterial and host cell membranes, promoting pathogenesis of infections.

Regarding bacterial type III secretions systems, which of the following statements is correct? (A) They are commonly found in Gram-positive commensal bacteria. (B) They play an important role in the pathogenesis of toxin induced diseases of Clostridium species, tetanus, botulism, gas gangrene, and pseudomembranous colitis. (C) They cause release of effectors of pathogenesis into the extracellular environment, promoting bacterial colonization and multiplication. (D) They directly inject bacterial proteins into host cells across bacterial and host cell membranes, promoting pathogenesis of infections. (E) Mutations that prevent the bacterial type III secretion from functioning enhance pathogenesis.

(D) Synovial fluid

Resident flora is absent from the (A) Pharynx (B) Lungs (C) Small intestine (D) Synovial fluid (E) Conjunctiva

(B) Urethra

Resident flora is commonly found in the (A) Liver (B) Urethra (C) Kidneys (D) Salivary glands (E) Gallbladder

(D) Results in protective antitoxin levels in most children by the time they are 6-8 years old

Skin diphtheria as occurs in children in tropical areas typically (A) Does not occur in children who have been immunized with diphtheria toxoid (B) Is clinically distinct from skin infections (pyoderma, impetigo) caused by Streptococcus pyogenes and Staphylococcus aureus (C) Is also common in northern latitudes (D) Results in protective antitoxin levels in most children by the time they are 6-8 years old (E) Yields toxin-mediated cardiomyopathy

(B) Nasopharynx

Streptococcus pneumoniae can be part of the normal flora of 5-40% of people. At what anatomic site can it be found? (A) Conjunctiva (B) Nasopharynx (C) Colon (D) Urethra (E) Vagina

(C) Release of inhibitory glycine and γ-aminobutyric acid

Tetanus toxin (tetanospasmin) diffuses to terminals of inhibitory cells in the spinal cord and brainstem and blocks which of the following? (A) Release of acetylcholine (B) Cleavage of SNARE proteins (C) Release of inhibitory glycine and γ-aminobutyric acid (D) Release of protective antigen (E) Activation of acetylcholine esterase

(B) Trimethoprim-sulfamethoxazole

The drug of choice to treat this patient's infection (Question 1) is (A) Penicillin G (B) Trimethoprim-sulfamethoxazole (C) Gentamicin (D) Amphotericin B (E) A third-generation cephalosporin

(D) B. anthracis

The first microorganism to satisfy Koch's postulates (in the late 19th century) was (A) T. pallidum (B) S. maltophilia (C) M. leprae (D) B. anthracis (E) N. gonorrhoeae

(D) To treat her with fluid and electrolyte replacement

The most important thing that can be done to treat the patient (Question 11) is (A) To give her ciprofloxacin (B) To give her a toxoid vaccine (C) To give her the appropriate antitoxin (D) To treat her with fluid and electrolyte replacement (E) To culture her stool to make the correct diagnosis and then treat specifically

(E) Tetanus toxin acts on inhibitor interneuron synapses.

Which of the following statements about tetanus and tetanus toxoid is correct? (A) Tetanus toxin kills neurons. (B) Tetanus toxoid immunization has a 10% failure rate. (C) The mortality rate of generalized tetanus is less than 1%. (D) Double vision is commonly the first sign of tetanus. (E) Tetanus toxin acts on inhibitor interneuron synapses.

(A) Lipopolysaccharide is part of the cell wall of E. coli.

Which of the following statements is correct? (A) Lipopolysaccharide is part of the cell wall of E. coli. (B) Cholera toxin is attached to the flagella of V. cholerae. (C) The lecithinase of C. perfringens causes diarrhea. (D) Toxic shock syndrome toxin-1 is produced by hemolytic stains of S. epidermidis.

(C) It is a rare cause of pulmonary infection in humans.

Which of the following statements regarding Rhodococcus equiis correct? (A) It is transmitted person to person. (B) It causes tuberculosis in cattle. (C) It is a rare cause of pulmonary infection in humans. (D) It produces a black pigment on sheep blood agar.

(B) Recombinant vaccine trials have shown good safety and efficacy.

Which of the following statements regarding vaccination for Bacillus anthracis is correct? (A) It is routinely available for all citizens of the United States. (B) Recombinant vaccine trials have shown good safety and efficacy. (C) The current vaccine is well tolerated. (D) A single dose is adequate after exposure to spores. (E) Vaccination of animals is not useful.

(A) tularensis

Which of the following subspecies of F. tularensis is the most virulent for humans? (A) tularensis (B) holarctica (C) mediasiatica (D) novicida

(A) Protective antigen

Which one of the following is an important virulence factor of Bacillus anthracis? (A) Protective antigen (B) Lipopolysaccharide (C) Pili (D) A toxin that inhibits peptide chain elongation factor EF-2 (E) Lecithinase

(E) Group B streptococci

Which one of the following microorganisms can be part of the normal vaginal flora and cause meningitis in newborns? (A) Candida albicans (B) Corynebacterium species (C) Staphylococcus epidermidis (D) Ureaplasma urealyticum (E) Group B streptococci

(B) Streptococcus mutans

Which one of the following microorganisms is closely associated with dental caries? (A) Candida albicans (B) Streptococcus mutans (C) Prevotella melaninogenica (D) Neisseria subflava (E) Staphylococcus epidermidis