CNS qs - guest78

[ArchivalUser]

Q1 AAAA.


This patient has transfusion-related West Nile virus encephalitis. Most cases of West Nile virus infection are subclinical, and the virus remains in the circulation for as long as 28 days. Blood products occasionally become infected, and cases have been documented in which West Nile virus was transmitted via donated blood. Although donated blood is tested using nucleic acid amplification techniques, this study is not 100% sensitive.

Bacterial infection should always be considered early in the course of a patient with a suspected central nervous system infection, but this patient's clinical course and cerebrospinal fluid findings more strongly support a diagnosis of West Nile virus infection. Both pneumococcal and meningococcal meningitis are unlikely because of the absence of leukocytosis and the lack of characteristic findings associated with bacterial meningitis in the cerebrospinal fluid. Staphylococcal sepsis is also unlikely because the patient has no signs of a localized bacterial infection and does not have leukocytosis. Although aseptic meningitis should also be included in the differential diagnosis, this patient's muscle symptoms and findings suggestive of encephalitis (e.g., severe headache, mental status changes) are more consistent with West Nile virus infection.

[ArchivalUser]

Q2 AAAA

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.
Bibliography

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Q3.AAA

The 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]

Q4..DDD

Vancomycin should be started per rectum. In a patient with marked paralytic ileus, oral medications are unlikely to be transported to the colon in sufficient quantity to be therapeutic. In addition, metronidazole, which has extensive enterohepatic circulation, is equally unlikely to reach the colon.

Clindamycin is inappropriate because Clostridium difficile is uniformly resistant to this antibiotic. Clindamycin is also likely to cause colitis. Ciprofloxacin, either orally or rectally, has little or no effect on C. difficile, and some studies report that ciprofloxacin is one of the most common antibiotics associated with nosocomial outbreaks of C. difficile colitis.


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