Survey of resistance of Pseudomonas aeruginosa from UK patients with cystic fibrosis to six commonly prescribed antimicrobial agents

Background: Respiratory infection with Pseudomonas aeruginosa is very common in patients with cystic fibrosis (CF) but antimicrobial resistance rates of CF isolates across the UK are largely unknown. Methods: The susceptibility of 417 CF patient isolates of P aeruginosa from 17 hospitals to six commonly prescribed antibiotics were examined. Isolates were tested by an agar break point dilution method and E-tests according to British Society of Antimicrobial Chemotherapy guidelines. Genotyping of isolates was performed by Xbal DNA macrorestriction and pulsed field gel electrophoresis. Results: 38% of isolates were susceptible to all of the agents tested; almost half were resistant to gentamicin compared with ceftazidime (39%), piperacillin (32%), ciprofloxacin (30%), tobramycin (10%), and colistin (3%). Approximately 40% were resistant to two or more compounds with ceftazidime in combination with gentamicin, piperacillin or ciprofloxacin being the most common cross resistances. Resistance rates were generally similar to those reported recently from the USA and Germany. A selection of resistant isolates proved to be predominantly genotypically distinct by Xbal DNA macrorestriction but six pairs from three centres had similar genotypes. Conclusions: The level of resistance to front line antipseudomonal agents, with the exception of colistin, is disturbingiy high. The prudent use of antimicrobial drugs and closer monitoring of accumulation of resistant strain populations should be actively considered.