The relationship between the use of flucloxacillin, vancomycin, aminoglycosides and ciprofloxacin and the susceptibility patterns of coagulase-negative staphylococci recovered from blood cultures

Antibiotic use is a cause of selection of multiresistant bacterial strains. Over three years (1990-1992) we studied the relation between the use of flucloxacillin, vancomycin, aminoglycosides and ciprofloxacin and the susceptibility of coagulase-negative staphylococci (CNS) recovered from blood cultures. Although there was no increase in the use of flucloxacillin, the susceptibility of CNS to this antibiotic decreased from 25% to 6%. No increase in aminoglycoside use was seen, though the use in the non-surgical intensive care unit was 40 times the average use in the hospital. The susceptibility to gentamicin declined from 36% to 15% for the rest of the hospital and to zero for the non-surgical intensive care unit. Vancomycin use did not change in the hospital as a whole, but the use in the haematological unit was about ten times that in the rest of the hospital. No single resistant strain (vancomycin MIC > or = 4 mg/L) was found. A three-fold increase in ciprofloxacin use was seen. After a decline in the susceptibility to ciprofloxacin from 72% to 58% in 1991, there was a small recovery to 62% in 1992. The use in the haematological unit was about 20 times that in the rest of the hospital. Ciprofloxacin susceptibility declined from 40% to 25% in that unit in 1991. In 1992 there was a small recovery to 29%.