engleski

Acinetobacter baumannii from a sewage of a nursing home in Croatia

Aim: In the previous studies the predominance of OXA-24/40 and OXA-23 β-lactamase was reported among Acinetobacter baumannii in both the hospitals and long-term care facilities (LTCF) in Croatia. The aim of this study was to determine antibiotic susceptibility, mechanisms of antibiotic resistance and molecular epidemiology of A. baumannii isolates recovered from sewage of a nursing home in Zagreb. Materials/methods: In April 2017, ten A. baumannii isolates were collected from sewage of two nursing homes in Zagreb. Antibiotics susceptibility was determined by broth microdilution method. The presence of carbapenemases of class A, B and D and extended- spectrum β-lactamases genes was explored by PCR. The occurrence of the ISAba1 upstream of the blaOXA-51-like or blaOXA-23- like was determined by PCR mapping. Conjugation and transformation experiments were performed as previously described. Plasmid incompatibility groups were determined by PBRT. Genotyping was performed by sequence group determination using multiplex PCR, PFGE and MLST. Results: Eight isolates were resistant to gentamicin and ciprofloxacin, three to ceftazidime and cefepime and two to carbapenems. There was uniform susceptibility to colistin. All isolates were positive for chromosomal blaOXA-51 whereas two carbapenem- resistant isolates were found to possess also blaOXA-23 genes. ISAba1 was found upstream of blaOXA-51 in seven out of ten isolates. Attempts to transfer imipenem resistance were unsuccessful indicating chromosomal location of blaOXA-23 gene. The plasmids extracted from isolates positive for OXA-23 belonged to Inc group 6 encoding aci6- replicase gene. Two OXA-23 positive isolates belonged to SG 1 (IC2) whereas the rest of the isolates susceptible to carbapenems were allocated to SG 2 (IC1). Additional MLST analysis corroborated that two OXA-23 and carbapenem- resistant isolates belong to the ST-195 clustering into the CC92 within the IC2, commonly reported worldwide. The susceptible isolates belonging to IC1 were found to be clonally related by PFGE, but different from the carbapenem- resistant. Conclusions: This study showed dissemination of OXA-23 producing A. baumannii from the nursing home into the urban sewage. Disinfection of nursing home sewage should be recommended in order to prevent the spread of resistance genes into the community sewage and consequently the nature.

carbapenem ; OXA-23 ; resistance, long-term care facility ; Croatia

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