engleski

Occurence of OXA-107 and Isaba1 in carbapenen-resistant isolates of Acinetobacter bauannii from Croatia

Recently a dramatic increase in the prevalence of carbapenem resistant Acinetobacter baumannii isolates was observed in University Hospital Split. The aim of the study was the molecular characterization of oxacillinases conferring carbapenem resistance in A. baumannii isolates from Split. In total, 106 carbapenem resistant isolates of Acinetobacter baumannii were obtained from different intensive care units inside University Hospital of Split, Croatia, during six years (2002-2007) study period. The susceptibility to a wide range of antibiotics was determined by disc-diffusion and broth microdilution method according to CLSI. BlaOXA genes were detected by PCR using conditions and protocols as described previously. Amplicons of the selected representative strains were subjected to sequencing of blaOXA-genes. Genetic relatedness of the isolates was determined by pulsed-field gel electrophoresis. All isolates of A. baumannii displayed susceptible or resistant profile to imipenem (MICs 2-32 mg/L) and intermediate or resistant profile to meropenem (MICs 8-128 mg/L) with higher MICs values to meropenem. Susceptibility testing found all isolates to be resistant to all tested antibiotics except of colistin. Carriage of genes encoding oxacillinases (group D carbapenemases) was associated in previous investigations with elevated MICs of imipenem. In present study we found OXA-51 group of oxacillinases in all tested isolates by PCR. Sequencing data confirmed presence of new OXA-107 enzyme in six representative strains. The most of isolates with carbapenem resistance profile (100/106) were found to possess ISAba1 insertion sequence located upstreams of blaOXA-51 gene. According to PFGE all isolates were clonally related with similarity cut-off value of 85% and were assigned into three PFGE clusters. Changes in antibiotic policy are recommended to reduce selection pression which favours spread of carbapenem resistant A. baumanii isolates in the hospital environment.

Acinetobacter baumannii; carbapenems; oxacillinases

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