Characteristics of initial compared with subsequent bacterial infections among hospitalised haemato-oncological patients

Surveys of bacterial infections among neutropenic cancer patients frequently report pooled antibiotic susceptibility data. Management guidelines address initial antibiotic regimens for febrile neutropenia. In this study, rates of bacterial infection and antibiotic susceptibilities among initial and subsequent or breakthrough episodes of fever were analysed. Prospective surveillance of fever of unknown origin (FUO), clinically documented infection and microbiologically documented infection (MDI) was conducted in the haemato-oncology and haematopoietic stem cell transplantation wards in a single cancer centre in Israel. Subsequent infections were defined as those developing during or after broad-spectrum antibiotic treatment. A total of 567 febrile episodes were documented among 271 patients. Bacterial MDIs were documented in 104/162 (64%) initial febrile episodes and 75/405 (19%) subsequent episodes and Gram-negative bacteria predominated (64% and 71%, respectively). Escherichia coli was the most common species isolated. Higher antibiotic susceptibilities were observed for initial compared with subsequent MDIs for Gram-negative bacteria [ceftazidime 80% vs. 45%, piperacillin/tazobactam (TZP) 86% vs. 40% and meropenem 95% vs.76%] and Gram-positive bacteria. TZP monotherapy was the most commonly used antibiotic and its susceptibility decreased to 22.2% following its use. Appropriate empirical antibiotic treatment was administered in 71/97 (73%) initial and 40/74 (54%) subsequent episodes (P = 0.009) and was significantly associated with mortality (adjusted odds ratio = 0.4, 95% confidence interval 0.18-0.87). We conclude that previous antibiotic exposure significantly impacts antibiotic susceptibility and that pooled reporting of all infections can be misleading. Treatment guidelines should address the antibiotic treatment of breakthrough fever.