Ten-year surveillance of nosocomial bloodstream infections: trends of aetiology and antimicrobial resistance in a comprehensive cancer centre

BACKGROUND: Bloodstream infections (BSIs) are one of the major life-threatening infectious conditions in cancer patients and are responsible for prolonged hospital stays, high healthcare costs and significant mortality. Several clinical trials have reported an improved survival in patients treated with appropriate empirical broad-spectrum antibiotic therapy. Early detection of pathogens and determination of their susceptibility are essential for the optimization of treatment. Variability between hospitals is substantial and requires the individual analysis of local trends. The aim of this study is to assess the local epidemiology of BSI in a single cancer centre over a 10-year period. METHODS: Retrospective microbiological surveillance of all febrile/infective episodes occurring in oncological and surgical patients in a high-volume cancer centre between January 1999 and December 2008 were considered. Patients’ data were collected, processed and analyzed using the epidemiological resource of the Virtuoso Plus software (Metafora Informatica Srl, Milano, Italy). Spearman’s rank correlation coefficient, including the two-tailed test of significance, was used to investigate trends of incidence and rate of antibiotic resistance over the 10-year period. RESULTS: A total of 13,058 blood cultures (BCs) were performed in 2,976 patients. BCs were positive in 2,447 tests, representing 740 infective/febrile episodes: 358 (48%) in medical oncology and 382 (52%) in surgical wards. Gram-positives were responsible for the majority of episodes in oncological and surgical divisions (about 63% and 55%, respectively). Gram-positives were also the most common organism in non-catheter-related BSIs (CRBSIs) both in medical oncology (75%) and in surgical divisions (50%). Enterococci showed an increased resistance to levofloxacin, from 5.6% to 25.7% (p = 0.02) and to erythromycin, from 41.7% to 61.4%, (p = 0.05). Similarly, coagulase negative staphylococci (CoNS) developed resistance to levofloxacin and ciprofloxacin, passing from 33.9% to 67.4% (p = 0.01) and from 5.6% to 25.7% (p = 0.01), respectively. CONCLUSIONS: Gram-positives are the main pathogens of BSIs; there is no difference in aetiology of CRBSIs between surgical and oncological patients. The lower incidence of gram-positive non-CRBSIs in surgical patients was probably due to gram-negative infections secondary to surgical complications.