SPREAD OF BETA-LACTAM-RESISTANT PSEUDOMONAS-AERUGINOSA IN A CYSTIC-FIBROSIS CLINIC

Background Pseudomonas aeruginosa colonisation of the airways of patie nts with cystic fibrosis (CF) is associated with considerable respirat ory morbidity. Although segregation of colonised patients from non-col onised patients to prevent cross-infection has been recommended, there is little evidence that such cross-infection is widespread. We observ ed that a high proportion of children attending our CF clinic were col onised with P aeruginosa that was resistant to ceftazidime and other b eta-lactam antibiotics. We used two genomic fingerprinting techniques to see whether this may have arisen from epidemic spread of a single s train. Methods The prevalence of P aeruginosa colonisation and the ant ibiotic susceptibility of the organisms was determined from review of laboratory reports in the case-notes of 120 children with CF. Isolates were cultured from the sputum of 65 children colonised with ceftazidi me-resistant P aeruginosa. Polymorphisms in total bacterial DNA from 9 2 isolates were analysed with two molecular fingerprinting techniques- pulsed-field gel electrophoresis after restriction enzyme digestion an d assessment of flagellin gene polymorphisms by amplification of the w hole gene and restriction enzyme digestion. Results 92 (76.7%) of 120 children were colonised with P aeruginosa, and 65 of the 92 harboured isolates that were resistant to ceftazidime. Only three of the 92 chil dren had never been treated with ceftazidime. The results of the two m olecular-fingerprinting techniques were concordant and showed that 55 of 65 children harboured the same epidemic strain. This strain was res istant to ceftazidime, azlocillin, and imipenem, and sensitive to tobr amycin and ciprofloxacin. Interpretation This study provides the first molecular evidence of a long-term outbreak of P aeruginosa in a CF ce ntre. We suggest that careful surveillance of the prevalence of antibi otic resistance in CF centres should be instituted with measures to pr event cross-infection. We believe that antipseudomonal monotherapy sho uld be considered with caution.