Comparison of antimicrobial use and resistance of bacterial isolates in a haematology ward and an intensive care unit.

The objective of the study presented here was to compare antimicrobial use and resistance of bacterial isolates in the haematology ward and the intensive care unit of Bolzano General Hospital. The bacterial organisms isolated most frequently from patients in the two wards (coagulase-negative staphylococci, Enterococcus spp., and Pseudomonas aeruginosa) were investigated for antimicrobial resistance. Isolates obtained from patients in the haematology ward were more often resistant to antimicrobial agents than isolates obtained from patients in the intensive care unit, and the agents against which the highest rates of resistance were found were third- and fourth-generation cephalosporins, carbapenems and monobactams, quinolones, aminoglycosides, and trimethoprim-sulfamethoxazole. These classes of antimicrobial agents were also used more frequently in the haematology ward than in the intensive care unit. Conversely, penicillinic beta-lactam antibiotics, rifamycins, macrolides and lincosamides were used less frequently in the haematology ward than in the intensive care unit, and the rates of resistance against these classes of antimicrobial agents were significantly lower in the haematology ward than in the intensive care unit. The results support the hypothesis that a causal relationship exists between antimicrobial use and the development of resistance and indicate that careful monitoring of antimicrobial use in hospitals is required to identify situations in which prescription patterns are contributing to the development of resistance.