Home Books Jawetz, Melnick, & Adelberg’s Medical Microbiology, 27e

Chapter 9: Pathogenesis of Bacterial Infection

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

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) Escherichia coli O157:H7 (lipopolysaccharide O antigen 157; flagellar antigen 7)

(B) Vibrio cholerae type O139 (lipopolysaccharide O antigen 139)

(C) Shigella dysenteriae type 1

(D) Campylobacter jejuni

(E) Entamoeba histolytica

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 Staphylococcus 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.

The first microorganism to satisfy Koch’s postulates (in the late 19th century) was

(A) Treponema pallidum

(B) Stenotrophomonas maltophilia

(C) Mycobacterium leprae

(D) Bacillus anthracis

(E) Neisseria gonorrhoeae

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.

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)

The organism most likely to be responsible for the patient’s disease is

(A) E coli

(B) Corynebacterium diphtheriae

(C) Clostridium perfringens

(D) Neisseria meningitidis

(E) Staphylococcus aureus

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

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.

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.

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) Shigella dysenteriae type 1 that produces Shiga toxin

(D) Enterotoxigenic E coli that produces heat-labile and heat-stable toxins

(E) Staphylococcal enterotoxin F

The most important thing that can be done to treat the patient 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

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)

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 Tropheryma 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

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

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Chapter 9: Pathogenesis of Bacterial Infection

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