July 2003: Case Study 2

CP, a 45-year-old paraplegic, is transferred from the nursing home to the local hospital with the diagnosis of pneumonia. In the hospital, she receives intravenous ceftriaxone while culture and sensitivity results are pending.

On day 3 of her hospitalization, the sputum culture reveals Klebsiella pneumoniae.The sensitivity results are reported as follows:

Ampicillin

Resistant

Ampicillin/sulbactam

Resistant

Aztreonam

Resistant

Cefotaxime

Susceptible

Ceftazidime

Resistant

Ceftriaxone

Resistant

Piperacillin/tazobactam

Intermediate

Sulfamethoxazole/trimethoprim

Intermediate

Gentamicin

Resistant

Tobramycin

Intermediate

Amikacin

Susceptible

Ciprofloxacin

Intermediate

Imipenem

Susceptible

The resident following CP?s case notices that the bacteria in her sputum are resistant to the ceftriaxone she has received since her admission. He decides to change her antibiotic regimen according to the sensitivity results. After "tossing a coin," he writes an order for CP to receive imipenem, rather than cefotaxime plus amikacin.

When the pharmacist receives the imipenem order, she must verify that CP meets the hospital?s criteria for the use of this antibiotic. After reviewing CP?s chart, should the pharmacist agree with the resident?s decision to prescribe imipenem?

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The pharmacist should agree with the decision to prescribe imipenem. CP?s Klebsiella pneumoniae is an extended-spectrum beta-lactamase (ESBL)?producing strain. Beta-lactamase?producing bacteria will hydrolyze amoxicillin and ampicillin; ESBL producers will hydrolyze even extended-spectrum beta-lactams, such as third-generation cephalosporins. As shown by the sensitivity report, not all beta-lactams are hydrolyzed to the same extent. The report shows that cefotaxime maintains susceptibility. Yet, for treatment purposes, in the presence of an ESBL-producing bacterium, all third- and fourth-generation cephalosporins should be considered resistant. The treatment of choice for an ESBL-producing bacterium is a carbapenem, such as imipenem.

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