The relationship between resistance in bacteria and antibiotic use in neurology and haematology units

Sir, This study examines the association between the consumption of antibiotics by patients and the antibiotic resistance in organisms from two separate hospital units, haematology (10 beds) and neurology (24 beds). The average length of stay in the Haematology Unit was 12.2 days and 8.2 days in the Neurology Unit; the average turn-round time was 1.3 days in haematology and 0.7 days in neurology. There were therefore 28 patients/bed/ year in the Haematology Unit and 37 patients/bed/year in the Neurology Unit. It is generally accepted that the prevalence of antibiotic resistant bacteria relates to the use of antibiotics due to the resulting selective pressure in the environment [1,2]. The present study measured resistance to meropenem and ciprofloxacin over a 10 week period in environmental Gram negative coliform bacilli isolated from these two units and infected patients on the wards, and related this to the use of meropenem and ciprofloxacin. In the Haematology Unit 256 g of meropenem and 340 g of ciprofloxacin were prescribed during the period October to December 1999. In contrast no meropenem nor any other carbapenem was used in the Neurology Unit and only 43 g of ciprofloxacin were used. There were 78 isolates of Enterobacteriaceae from the environment of the Haematology Unit of which 22 (28%) were resistant to meropenem and five (7%) to ciprofloxacin. In the Neurology Unit 11 of 82 strains from the environment (13%) (PB0.03) were resistant to meropenem and 19 (23%) (PB0.006) were resistant to ciprofloxacin (Table 1.). The P values were derived using the x test; PB0.05 was considered statistically significant. From both units there were 11 isolates from infected patients, all of which were sensitive to both meropenem and ciprofloxacin. Thus in contrast to some other studies [1,2] we found no correlation between the amount of antimicrobials used in the units, in this case meropenem and ciprofloxacin, and the occurrence of resistant isolates in the environment. There was also no evidence that resistant environmental flora was related to patient infection, as reported in at least two studies [3,4] as no patients‘ isolates were resistant to either antibiotic. Y. Krupova Trnava University, School of Public Health, Hornoptocna 23, Trnava, Slovakia J.C. Gould Western General Hospital, Edinburgh, Scotland