WorksheetsOther bacteria
Total questions: 23
Worksheet time: 46mins
Name
Class
Date
1.
Your patient is a 25-year-old homeless man who complains of a cough for the past month. The cough is now productive of several tablespoons of blood-streaked sputum per day. The sputum is not foul-smelling. He has lost 10 pounds but says that he doesn’t eat regularly. On physical exam, temperature is 38°C, and coarse rales are heard in the apex of the left lung. An acid-fast stain of the sputum reveals acid-fast rods. Culture of the sputum shows no growth at 7 days, but buff-colored colonies are visible at 21 days. Of the following organisms, which one is most likely to be the cause of this infection?
a)
(A) Mycobacterium fortuitum-chelonae
b)
(B) Mycobacterium leprae
c)
(C) Mycobacterium marinum
d)
(D) Mycobacterium tuberculosis
2.
Which one of the following regimens is optimal initial treatment for the patient in Question 1?
a)
(A) Isoniazid for 9 months
b)
(B) Isoniazid and gentamicin for 2 weeks
c)
(C) Isoniazid and rifampin for 4 months
d)
(D) Isoniazid, rifampin, ethambutol, and pyrazinamide for 2 months
3.
Your patient is a 70-year-old man with progressive weakness in both legs that began about a week ago. He reports back pain and fever for the past month. Magnetic resonance imaging (MRI) of the spine revealed destruction of the seventh thoracic vertebra and a paravertebral mass. Surgical decompression and debridement were performed. Histologic examination of the mass revealed caseating granulomas, and Langhans’ giant cells were observed in the granulomas. Gram stain revealed no organisms, but an acid-fast stain showed red rods. Culture showed no growth at 7 days, but growth was seen at 28 days. Of the following, which one is the most likely cause?
a)
(A) Mycobacterium fortuitum-chelonae
b)
(B) Mycobacterium leprae
c)
(C) Mycobacterium marinum
d)
(D) Mycobacterium tuberculosis
4.
Your patient is a 30-year-old woman who is infected with HIV and has a low CD4 count. She now has the findings of pulmonary tuberculosis, but you are concerned that she may be infected with Mycobacterium avium-intracellulare (MAI). Regarding MAI, which one of the following is most accurate?
a)
(A) Disseminated disease caused by MAI is typically the result of decreased antibody production, whereas disseminated disease caused by M. tuberculosis is typically caused by reduced cell-mediated immunity.
b)
(B) Immigrants from Southeast Asia are more likely to be infected with MAI than with M. tuberculosis.
c)
(C) In the clinical laboratory, MAI forms colonies in 7 days, whereas M. tuberculosis colonies typically require at least 21 days of incubation for colonies to appear.
d)
(D) MAI is typically susceptible to a drug regimen of isoniazid and rifampin, whereas M. tuberculosis is often resistant.
e)
(E) The natural habitat of MAI is the environment, whereas the natural habitat of M. tuberculosisis humans.
5.
Regarding the patient in Question 4, if MAI was shown to be the cause of her symptoms, which one of the following is the best choice of antibiotics to prescribe?
a)
(A) Amikacin and doxycycline
b)
(B) Clarithromycin, ethambutol, and rifabutin
c)
(C) Dapsone, rifampin, and clofazimine
d)
(D) Isoniazid and gentamicin
e)
(E) Isoniazid, rifampin, ethambutol, and pyrazinamide
6.
Your patient is a 20-year-old man with a single, slowly expanding, nonpainful scaly lesion on his chest for the past 2 months. The lesion is nonpruritic, and he has lost sensation at the site of the lesion. He is otherwise well. He is a recent immigrant from Central America. An acid-fast stain of a scraping of the lesion is positive. Which one of the following diseases is he most likely to have?
a)
(A) Cutaneous tuberculosis
b)
(B) Fish tank granuloma
c)
(C) Lepromatous leprosy
d)
(D) Scrofula
e)
(E) Tuberculoid leprosy
7.
Your patient is a 75-year-old woman with fever and a painful nodule on her forearm. She also has a nonproductive cough that she says is worse than her usual smoking-related cough. She is taking high-dose corticosteroids (prednisone) for an autoimmune disease. Chest X-ray reveals a nodular lesion in the right upper lobe. A biopsy of the nodule on her arm was obtained. Gram stain of the specimen showed filaments of gram-positive rods. The rods were also weakly acid-fast. Regarding the causative organism, which one of the following is most accurate?
a)
(A) Culture of the organism should be done under anaerobic conditions.
b)
(B) The natural habitat of the organism is the soil.
c)
(C) It produces an exotoxin that inhibits protein synthesis by ADP-ribosylation.
d)
(D) Sulfur granules are often seen in the skin lesion.
e)
(E) The vaccine against this organism contains the capsular polysaccharide as the immunogen.
8.
Your patient is a 20-year-old man who was in a fist fight in a bar about 3 weeks ago. He took a punch that broke his left second molar. He now has a 3-cm inflamed area on the skin overlying the broken tooth that is draining pus. A Gram stain of the pus reveals gram-positive filamentous rods. The rods did not appear red in the acid-fast stain. Regarding the causative organism, which one of the following is most accurate?
a)
(A) Infections caused by this organism occur primarily in the Ohio and Mississippi River Valley area.
b)
(B) The natural habitat of the organism is the soil.
c)
(C) This organism is resistant to both penicillins and aminoglycosides.
d)
(D) Sulfur granules are often seen in the pus located at the orifice of the sinus tract in the skin lesion.
e)
(E) The vaccine against this organism contains a toxoid as the immunogen.
9.
Mycoplasma pneumoniae is an important cause of atypical pneumonia. Regarding this organism, which one of the following is the most accurate?
a)
(A) Amoxicillin is the drug of choice for pneumonia caused by this organism.
b)
(B) Antibody in a patient’s serum will agglutinate human red blood cells at 4°C, but not at 37°C.
c)
(C) Gram stain of the sputum reveals small gram-negative rods.
d)
(D) It is an obligate intracellular parasite that can only grow within human cells in the clinical laboratory.
e)
(E) People with cystic fibrosis are predisposed to pneumonia caused by this organism.
10.
Which one of the following is the drug of choice for atypical pneumonia caused by M. pneumoniae?
a)
(A) Amoxicillin
b)
(B) Azithromycin
c)
(C) Ceftriaxone
d)
(D) Gentamicin
e)
(E) Vancomycin
11.
Your patient is a 65-year-old man with gradually increasing confusion and unsteadiness while walking. A lumbar puncture revealed clear spinal fluid, a normal glucose, and an elevated protein. There were 96 cells/μL, of which 86% were lymphocytes. Gram stain of the cerebrospinal fluid (CSF) was negative. Magnetic resonance imaging (MRI) of the brain was normal. A sample of CSF reacted with beef heart cardiolipin at a titer of 1/1024. Regarding the causative organism of his infection, which one of the following is most accurate?
a)
(A) It is transmitted by tick bite.
b)
(B) Resistance to penicillin G is common, so ceftriaxone should be used.
c)
(C) It has never been grown on bacteriologic media in the clinical laboratory.
d)
(D) It is unlikely to be eradicated because beef cattle are a major reservoir for the organism.
e)
(E) A confirmatory test for this organism utilizes an agglutination reaction with the capsular polysaccharide of the organism.
12.
Your patient is a 20-year-old man with an erythematous, macular, nonpainful rash on the right arm for the past 4 days. The rash is approximately 10 cm in diameter. He also has a fever to 100°F and a mild headache. He reports hiking on several weekends recently in New York State. You suspect the rash is erythema migrans and that he has Lyme disease. Which one of the following is the best approach to confirm your clinical diagnosis?
a)
(A) Detect IgM antibodies in an ELISA assay
b)
(B) Determine the titer in a VDRL test
c)
(C) Gram stain and culture on blood agar incubated aerobically
d)
(D) Gram stain and culture on blood agar incubated anaerobically
e)
(E) Grow on human cells in cell culture and identify with fluorescent antibody
13.
Assume the patient in the last question does have Lyme disease. Which one of the following antibiotics is the most appropriate to treat his infection?
a)
(A) Azithromycin or trimethoprim-sulfamethoxazole
b)
(B) Doxycycline or amoxicillin
c)
(C) Gentamicin or amikacin
d)
(D) Metronidazole or clindamycin
e)
(E) Penicillin G or levofloxacin
14.
Regarding syphilis, which one of the following is most accurate?
a)
(A) The characteristic lesion of primary syphilis is a painful vesicle on the genitals.
b)
(B) In secondary syphilis, the number of organisms is low, so the chance of transmitting the disease to others is low.
c)
(C) In secondary syphilis, both the rapid plasma reagin (RPR) and the fluorescent treponemal antibody-absorbed (FTA-ABS) tests are usually positive.
d)
(D) The antibody titer in the FTA-ABS test typically declines when the patient has been treated adequately.
e)
(E) In congenital syphilis, no antibody is formed against T. pallidum because the fetus is tolerant to the organism.
15.
Regarding Borrelia burgdorferi and Lyme disease, which one of the following is most accurate?
a)
(A) Borrelia burgdorferi infects a larger percentage of the rodent reservoir in western states, such as California, than in northeastern states, such as New York.
b)
(B) Pathogenesis of Lyme disease is based on the production of an exotoxin that induces interleukin-2 production by T-helper cells.
c)
(C) The vaccine against Lyme disease contains the capsular polysaccharide of all four serotypes as the immunogen.
d)
(D) Close family members of those infected with Borrelia burgdorferi should be given ciprofloxacin.
e)
(E) Borrelia burgdorferi is transmitted to humans by the bite of ticks of the genus Ixodes.
16.
Benzathine penicillin G is used to treat primary and secondary syphilis rather than procaine penicillin G. Which one of the following is the best reason for this choice?
a)
(A) Patients allergic to procaine penicillin G are not allergic to benzathine penicillin G.
b)
(B) Benzathine penicillin G has a higher minimal inhibitory concentration than procaine penicillin G.
c)
(C) Benzathine penicillin G penetrates the central nervous system to a greater degree than procaine penicillin G.
d)
(D) Benzathine penicillin G is a depot preparation that provides a long-lasting, high level of drug that kills the slow-growing Treponema pallidum.
17.
Your patient is a 20-year-old man with a urethral discharge. Gram stain of the pus reveals many neutrophils but no bacteria. You suspect this infection may be caused by C. trachomatis. Which one of the following is the laboratory result that best supports your clinical diagnosis?
a)
(A) Gram stain of the pus reveals small gram-positive rods.
b)
(B) The organism produces β-hemolytic colonies on blood agar plates when incubated aerobically.
c)
(C) The organism produces α-hemolytic colonies on blood agar plates when incubated anaerobically.
d)
(D) Fluorescent antibody staining demonstrates cytoplasmic inclusions in epithelial cells in the exudate.
e)
(E) There is a fourfold or greater rise in antibody titer against C. trachomatis.
18.
Regarding chlamydiae, which one of the following is the most accurate?
a)
(A) Lifelong immunity usually follows an episode of disease caused by these organisms.
b)
(B) The reservoir host for the three species of chlamydiae that cause human infection is humans.
c)
(C) Their life cycle consists of elementary bodies outside of cells and reticulate bodies within cells.
d)
(D) They can only replicate within cells because they lack the ribosomes to synthesize their proteins.
e)
(E) The vaccine against C. pneumoniae contains the capsular polysaccharide as the immunogen conjugated to a carrier protein.
19.
Which one of the following is the drug of choice for sexually transmitted disease (urethritis, cervicitis) caused by C. trachomatis?
a)
(A) Ampicillin
b)
(B) Azithromycin
c)
(C) Ciprofloxacin
d)
(D) Metronidazole
e)
(E) Rifampin
20.
Your patient is a 40-year-old woman with the sudden onset of fever to 40°C, severe headache, and petechial rash over most of her body including the palms. Blood cultures are negative. Unfortunately, despite antibiotics and other support, she dies the day after presentation. An autopsy is performed, and immunohistochemical tests on her brain tissue reveal an infection by Rickettsia rickettsii. Of the following, which one is the most accurate?
a)
(A) It is likely she lives in Colorado and was bitten by a tick.
b)
(B) It is likely she lives in Colorado and was bitten by a mosquito.
c)
(C) It is likely she lives in Virginia and was bitten by a tick.
d)
(D) It is likely she lives in Virginia and was bitten by a flea.
e)
(E) It is likely she lives in Connecticut and was bitten by a mosquito.
21.
Regarding Q fever, which one of the following is most accurate?
a)
(A) The causative organism is transmitted by tick bite.
b)
(B) The natural habitat of the causative agent is the white-footed mouse.
c)
(C) The diagnosis is made primarily by Gram stain and culture on chocolate agar.
d)
(D) Occupations that predispose people to Q fever include veterinarians and abattoir workers.
e)
(E) Patients with Q fever often have a petechial rash involving the palms.
22.
Regarding Haemophilus ducreyi, which one of the following is most accurate?
a)
(A) It requires both X and V factors to grow on MacConkey’s agar.
b)
(B) Gram stain of exudate from the lesion shows large gram-positive rods.
c)
(C) Penicillin G is the drug of choice to treat infections caused by H. ducreyi.
d)
(D) It causes chancroid, which is characterized by a painful ulcer on the genitals.
23.
Regarding Yersinia enterocolitica, which one of the following is most accurate?
a)
(A) It causes mesenteric adenitis, which can mimic appendicitis.
b)
(B) It is a gram-negative diplococcus found primarily within neutrophils.
c)
(C) It is the most common cause of enterocolitis in the United States.
d)
(D) Its natural habitat is the human oropharynx, and there is no animal reservoir.
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