Molecular epidemiology of PER-1 enzyme in nosocomial gram-negative bacteria

Objectives: To investigate the prevalence of PER-1 beta-lactamase over a five-year periodamong ceftazidime resistant Gram-negative bacteria isolated at Dokuz Eylul UniversityHospital and to analyse the genetic location of blaPER-1Methods: blaPER-1 presence was sought by PCR in 289 ceftazidime resistant Gram-negativebacteria isolated between 1998 and 2003. Clonal relationship of PER-1 producers wasdetermined by ERIC-PCR. Genetic location of blaPER-1 was investigated by conjugation,plasmid-curing experiments and integron-PCR. Integron-location of blaPER-1 was analysedby PCR combining primers specific for conserved region of class-1 integrons and blaPER-1,in representatives of each ERIC-PCR pattern. Direct sequencing of PCR-products wasperformed on both strands.Results and Conclusion: PER-1 production rates were 32.3 %, 33.9 %, 14.9 % and 37.9 %in 98-2000 period, 2001, 2002 and 2003, respectively. blaPER-1 was detected 46.2 % and35.9 % of ceftazidime resistant P. aeruginosa and A. baumannii isolates, respectively. An A.faecalis strain was also found to possess. blaPER-1. ERIC-PCR results revealed disseminationof two endemic clones for both P. aeruginosa (X and Y) and A. baumannii (A and B) wasresponsible for the high prevalence. Results of the conjugation tests and plasmid curingexperiments suggested that blaPER-1 was located on the chromosome in the representativestrains. PCR product obtained by combining class-1 integron and blaPER-1 specific primersin an P. aeruginosa isolate and confirmatory tests, indicated that blaPER-1 was integronassociated. We concluded that; the prevalence of PER-1-production among ceftazidime-resistant P. aeruginosa and A. baumannii isolates is high in our hospital and PER-1 producersare being transmitted horizontally as most of the isolates are clonally related. It is also shownthat, blaPER-1 was associated with class-1 integron in a clinical isolate for the first time, andthis could facilitate dissemination of blaPER-1 among bacteria.