Bacterial flora and antibiotic resistance in a clinical haematology unit

Infections are among the most serious complications in neutropenic patients and are associated with an increased morbidity and mortality. Ongoing surveillance of infection in neutropenic patients is essential to detect changes in epidemiology and to guide better empirical antibiotic regimens and infection control policies. The aim of this study is to analyze the bacterial flora and the antibiotic resistance of isolates in a clinical haematology unit during three years period. From 1 January 2003 to 31 December 2005, 437 strains were isolated from different specimens. Antimicrobial susceptibility testing has been carried out by disk diffusion method as referred to the French Society of Microbiology. All susceptibility data were stored in a laboratory data base using Whonet software. Duplicate isolates defined as the same bacterial species for the same patient with the same profile of susceptibility were excluded. Gram negative bacilli [GNB] rate was 47.1% and Gram positive cocci [GPC] rate 52.9%.The most frequently identified species were coagulase negative staphylococci [CNS]: 29.3%, Escherichia coli:14%, Staphylococcus aureus: 10.7%, Klebsiella pneumoniae: 9.1% and Pseudomonas aeruginosa:7.5%. The global rate of methicillin resistant staphylococci was 27.7% for S. aureus and 61.4% for CNS, no GISA [glycopeptide intermediate S.aureus] was detected during the study period. For E. coli, the frequencies of resistance to ceftazidime, ciprofloxacin and amikacin were respectively: 45%, 26. 3% and 21.3%.Concerning K. pneumoniae, 84, 8% of strains were resistant to ceftazidime and were producing extended spectrum,-lactamase [BLSE]. The trends of resistance showed an increasing rate of K. pneumoniae BLSE: 57.1% in 2003 versus 95.5% in 2005. However; all isolates remained susceptibles to imipenem and colistin. Concerning P. aeruginosa, 50% were resistant to ceftazidime, 50% to imipenem, 51.6% to ciprofloxacin and 54.5% to amikacin. An increasing rate of imipenem resistance in P. aeruginosa was observed from 2003 to 2005[28. 6% in 2003 versus 45. 5% in 2005]. Following this study, a restriction use of ceftazidime [substituted by piperacillin-tazobatam] was instaured in the unit. A further study should be conducted to evaluate the impact of piperacillin-tazobactam as a first line treatment in neutropenic patients