Recent changes in bacterial epidemiology and the emergence of fluoroquinolone-resistant Escherichia coli among patients with haematological malignancies:: results of a prospective study on 823 patients at a single institution

Background: Regular monitoring of bacterial epidemiology allows evaluation of antibacterial strategies adopted. The aim of this study was to disclose evolving trends in the epidemiology of infections and emerging antibiotic resistance in unselected inpatients with haematological cancers. Methods: Febrile/infectious episodes occurring in 823 patients consecutively admitted to a single institution during a 16 month period were analysed. Levofloxacin prophylaxis was used in patients with > 7 days expected neutropenia. Results: Fever developed in 364 patients (44.2%) and an infection was documented in 187 (22.7%), either clinically (6.1%) or microbiologically (16.6%). Levofloxacin prophylaxis, used in 39.4% of cases, caused a reduction in febrile episodes only among neutropenic patients and no difference in the frequency of documented infections. Among 164 pathogens isolated, Gram-negative (49.4%) outweighed Gram-positive bacteria (40.9%), Escherichia coli being most frequent (23.2%). Fluoroquinolone resistance and methicillin resistance were the most frequent types of antibiotic resistance, occurring in 56.1% of bacterial isolates and in 66.7% of staphylococci, respectively. Fluoroquinolone-resistant E. coli accounted for 20.1% of all isolates and for 86.8% of E. coli. Multivariate analysis of risk factors for fluoroquinolone resistance identified prophylaxis (P < 0.001) and neutropenia > 7 days (P = 0.02) as independent. Methicillin resistance was independently associated with prophylaxis (P = 0.041) and central venous catheters (P = 0.036). Infections by fluoroquinolone-resistant strains did not show a worse outcome. Conclusions: A shift towards Gram-negative bacteria has been occurring in recent years in the bacterial epidemiology of haematological patients. Fluoroquinolone resistance is emerging as a major type of antibacterial resistance, particularly among E. coli strains. Further investigation is needed to explore the consequences of such epidemiological changes.