mksap inf dis questions - step2ck270

[ArchivalUser]

* Oseltamivir and zanamivir are both active against influenza A and B.
* Because zanamivir may induce bronchospasm, it is contraindicated in patients with asthma.

[ArchivalUser]

Colonization with extended-spectrum β-lactamases (ESBLs) is endemic in nursing homes (about 40% of nursing-home residents are colonized with such strains). The carbapenems (imipenem, meropenem, ertapenem) are the most appropriate empiric agents for treating infections due to ESBL“producing gram-negative bacilli such as Klebsiella species.

Klebsiella isolates that are resistant to ceftriaxone are also likely to be resistant to other cephalosporins because of the presence of ESBLs. Because the plasmid that carries the ESBL gene also carries other resistance determinants, most ESBL-producing strains are also resistant to aminoglycosides and sulfa compounds. About half are resistant to fluoroquinolones. Therefore, administration of ceftazidime, ampicillin“sulbactam, trimethoprim“sulfamethoxazole, or moxifloxacin will be ineffective. In addition, this patient's recent exposure to a fluoroquinolone also increases her risk of having a resistant organism. Finally, moxifloxacin does not achieve adequate therapeutic levels in the urine.

[ArchivalUser]

* Antiretroviral therapy should be initiated for a treatment-naïve patient with HIV infection and a CD4 cell count less than 200/µL (0.2 × 109/L), even if the patient is asymptomatic.
* A regimen containing lamivudine, efavirenz, and tenofovir is appropriate for a treatment-naïve patient with HIV infection who also has chronic hepatitis B.

[ArchivalUser]

1A 52-year-old woman has a 2-month history of shortness of breath and a 1-month history of a nonproductive cough. Both symptoms are increasing. The patient has no allergies or exposures to occupational or environmental pulmonary contaminants. Medical history is unremarkable, and her only medication is an H2-receptor antagonist.

On physical examination, she appears dyspneic. Examination is otherwise normal except for a large healing bruise on her thigh that developed when she slipped in a hot tub.

A chest radiograph is normal. Pulmonary function tests show moderate obstructive disease with a slightly low diffusing capacity for carbon monoxide (DLCO). A sputum culture is positive for mycobacteria.

Which of the following most likely explains this patient's positive sputum culture?

A Mycobacterium avium complex hypersensitivity pneumonitis
B Tuberculous pneumonia
C Nocardia pneumonia
D Rhodococcus pneumonia
E A contaminant in the sputum culture

[ArchivalUser]

1The patient has a subacute illness that could be either pneumonia or pulmonary hypersensitivity. The overwhelming likelihood is that her illness is related to hot tub exposure and that an aerosol of Mycobacterium avium complex (MAC) is causing hypersensitivity pneumonitis. MAC is present in the water supply in most areas of the United States, which explains why people who use hot tubs (and, less frequently, showers) sometimes develop this form of hypersensitivity pneumonitis. What is not understood is why more people do not develop this infection.

Although the patient's pulmonary function tests are somewhat abnormal, she does not have tuberculosis because of the normal chest radiograph. Nocardia species can cause pneumonia. However, the most common Nocardia lung syndrome is nodular and tends to occur in patients with defects in cell-mediated immunity. Infection with Rhodococcus species is a rare cause of pneumonia in patients with reduced cell-mediated immunity and does not induce bronchitis. Although contamination of the sputum sample is possible, the clinical presentation is quite consistent with MAC hypersensitivity pneumonitis.

[ArchivalUser]

In immunosuppressed transplant recipients and other persons at high risk for developing active tuberculosis, a tuberculin skin test result of >5 mm of induration is considered a positive test.