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

Chapter 12: Aerobic Non–Spore-Forming Gram-Positive Bacilli: Corynebacterium, Listeria, Erysipelothrix, Nocardia, and Related Pathogens

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 pseudodiphtheriticum

(C) Aspergillus fumigatus

(D) Nocardia farcinica

(E) Erysipelothrix rhusiopathiae

The drug of choice to treat this patient’s infection is

(A) Penicillin G

(B) Trimethoprim–sulfamethoxazole

(C) Gentamicin

(D) Amphotericin B

(E) A third-generation cephalosporin

It is particularly difficult to differentiate Erysipelothrix rhusiopathiae from

(A) Corynebacterium diphtheriae

(B) Bacillus cereus

(C) Actinomyces israelii

(D) Nocardia asteroides

(E) Lactobacillus species

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

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

The primary mechanism in the pathogenesis of the boy’s disease 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

Corynebacterium jeikeium is

(A) Catalase negative

(B) Gram negative

(C) Often multidrug resistant

(D) Motile

(E) Common but clinically unimportant

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

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

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

A biochemical reaction that is useful in the identification of the causative agent of the infection is

(A) Catalase positivity

(B) Acid fastness using modified Kinyoun stain

(C) Esculin hydrolysis

(D) Tumbling motility

(E) Production of H₂S

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.

After recovery on laboratory media, the aerobic Actinomycetes are best identified by

(A) An automated system used in the laboratory

(B) Classical biochemicals

(C) Antigen detection tests such as an ELISA

(D) Molecular methods such as 16SrRNA gene sequencing

Which of the following statements regarding Rhodococcus equi is 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.

A hospitalized patient who had an indwelling urinary catheter develops fever, chills, suprapubic pain, and difficulty voiding 48 hours after the catheter is removed. His bladder appears obstructed, and he has white blood cells and bacteria on a urinalysis. Cystoscopy reveals a large bladder stone, and the urine culture grows greater than 10,000 CFU/mL of a short, irregular gram-positive rod. The most likely organism causing this infection is

(A) Corynebacterium urealyticum

(B) Nocardia brasiliensis

(C) Actinomadura

(D) Erysipelothrix rhusiopathie

(E) Lactobacillus acidophilus

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Chapter 12: Aerobic Non–Spore-Forming Gram-Positive Bacilli: Corynebacterium, Listeria, Erysipelothrix, Nocardia, and Related Pathogens

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Chapter 12: Aerobic Non–Spore-Forming Gram-Positive Bacilli: Corynebacterium, Listeria, Erysipelothrix, Nocardia, and Related Pathogens

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