Reduction in the incidence of methicillin-resistant Staphylococcus aureus and ceftazidime-resistant Klebsiella pneumoniae following changes in a hospital antibiotic formulary

In 1995, changes in our hospital formulary were made to limit an outbreak of vancomycin-resistant enterococci and resulted in decreased usage of cephalosporins, imipenem, clindamycin, and vancomycin and increased usage of β-lactam/β-lactamase-inhibitor antibiotics. In this report, the effect of this formulary change on other resistant pathogens is described. Following the formulary change, there was a reduction in the monthly number (mean ± SD) of patients with methicillin-resistant Staphylococcus aureus (from 21.9 ± 8.1 to 17.2 ± 7.2 patients/1,000 discharges; P = .03) and ceftazidime- resistant Klebsiella pneumoniae (from 8.6 ± 4.3 to 5.7 ± 4.0 patients/1,000 discharges; P = .02). However, there was an increase in the number of patients with cultures positive for cefotaxime-resistant Acinetobacter species (from 2.4 ± 2.2 to 5.4 ± 4.0 patients/1,000 discharges; P = .02). Altering an antibiotic formulary may be a possible mechanism to contain the spread of selected resistant pathogens. However, close surveillance is needed to detect the emergence of other resistant pathogens.