1. ¹Department of Medicine, The University of Texas Health Science Center at San Antonio, San Antonio, TX, USA
2. ²Department of Medicine, Division of Hematology, The University of Texas Health Science Center at San Antonio, San Antonio, TX, USA
3. ³School of Pharmacy, The University of Texas at Austin, Austin, TX, USA
4. ⁴Department of Psychiatry, The University of Texas Health Science Center at San Antonio, San Antonio, TX, USA
5. ⁵Department of Clinical Pharmacy and Pharmacology, University of Texas Health Science Center at San Antonio, San Antonio, TX, USA
6. ⁶Department of Medicine, South Texas Veterans Health Care System, San Antonio, TX, USA
7. ⁷Department of Medicine, Division of Infectious Diseases, The University of Texas Health Science Center at San Antonio, San Antonio, TX, USA

Correspondence: Dr J Cadena, Division of Infectious Diseases, University of Texas Health Science Center at San Antonio, 7703 Floyd Curl Drive, Mail Code 7881, San Antonio, TX 78229, USA. E-mail: cadenazuluag@uthscsa.edu

Received 15 January 2007; Revised 10 April 2007; Accepted 11 April 2007; Published online 28 May 2007.

Abstract

Multidrug-resistant pathogens have important effects on clinical outcomes. Antibiotic cycling is one approach to control anti-microbial resistance, but few studies have examined cycling in hematology–oncology units. Antibiotic cycling was implemented in January 1999 at our hematology–oncology unit, alternating piperacillin-tazobactam (pip-tazo) and cefepime in 3 months periods, until June 2004. Clinical isolates were compared in post- and pre-intervention periods and with the susceptibility among the solid organ transplant intensive care unit (TICU) isolates. The rate of Gram-negative isolates remained stable. Among Gram-negatives, susceptibility to cefepime and pip-tazo remained stable. There was an increase in Enterococcus spp. (P=0.007), and susceptibility to ampicillin and vancomycin decreased (odds ratio (OR): 0.04, 95% confidence interval (CI): 0.17–0.89 and OR: 0.23, 95% CI: 0.09–0.58). Compared with the TICU, there was increased susceptibility to pip-tazo and cefepime among enterics (OR: 7.32, 95% CI: 4.44–12.07 and OR: 8.82, 95% CI: 2.1–37.13) and Pseudomonas aeruginosa (OR: 4.27, 95% CI: 1.47–12.4 and OR: 4.61, 95% CI: 1.75–12.1) and decreased susceptibility to ampicillin and vancomycin among enterococci (OR: 0.44, 95% CI: 0.30–0.63 and OR: 0.38, 95% CI: 0.26–0.56). Cycling was associated with preserved antibiotic susceptibility among Gram-negatives, but with an increase in Enterococcus spp. and vancomycin and ampicillin resistance among enterococci.