Susceptibility to ciprofloxacin of nosocomial gram-negative bacteria and staphylococci isolated in the UK.

At the end of 1989 the Division of Hospital Infection of the Central Public Health Laboratory completed five years of continuous surveillance of ciprofloxacin susceptibility amongst strains of Staphylococcus aureus and Pseudomonas aeruginosa. The strains studied were referred from many different UK laboratories for epidemiological or other typing. Between 1987 and 1989, referred cultures of coagulase-negative staphylococci, Klebsiella spp. and Enterobacter spp. were also examined. In total, 25,728 cultures from 254 different laboratories were included in the study, and S. aureus was the most common species amongst the survey material. Resistance to non-quinolone antimicrobials was common amongst the isolates. Over the study period there has been a gradual decline in the percentage of cultures received that were fully susceptible to ciprofloxacin and an increase in the number of laboratories referring strains with resistance or reduced sensitivity. Full susceptibility of S. aureus to ciprofloxacin has declined from 99.6% of 8981 cultures isolated in the two years before launch to 92.8% of 1968 cultures isolated during 1989. Amongst the coagulase-negative staphylococci there has been a similar decline in susceptibility from 99.4% of 658 cultures examined in 1987 to 92.6% of 433 cultures studied in 1989. There was also a decrease in susceptibility of P. aeruginosa isolates to ciprofloxacin from 98.6% of 2579 cultures isolated in 1985 and 1986 to 86.3% of 1152 cultures examined during 1989. Most of this decrease was attributable to the appearance of strains of intermediate susceptibility to ciprofloxacin (MICs 2 or 4 mg/l). Virtually no resistance to ciprofloxacin was observed amongst isolates of Klebsiella spp. and Enterobacter spp. referred between 1987 and 1989. The emergence of ciprofloxacin resistance, and by implication cross resistance to many of the other fluoroquinolones, is a worrying development and suggests that caution should be exerted in the use of these compounds for the treatment of infections due to staphylococci and P. aeruginosa.