Occurrence and molecular characterization of metallo-β-lactamases (MBLs) among Acinetobacter baumannii isolates from cancer patients

Background: During the last decade, the prevalence of carbapenem-resistant infection associated with multidrug resistant (MDR) Acinetobacter baumanniiin patients has been continuously increasing.  This prospective study aimed to determine the occurrence and molecular characterization of metallo-β-lactamases (MBLs) and carbapenem hydrolyzing oxacillinases among A. baumannii isolates from cancer patients over a period of 6-month. Methods:Antimicrobial susceptibility profile of 70 randomly collected A. baumannii isolates was first determined using disc diffusion test, and second, the MICs of 45 representative multidrug resistant (MDR) isolates were tested to useful drugs in treatment of their infections using E-test.  PCR assays were used to detect the common four types of class D carbapenem hydrolyzing oxacillinases, two types of class A carbapenemases, four types of class B metallo-β –lactamases, and prevalence of Class 1 Integron among MDR isolates. Results: All 70 isolates were MDR, including 100% resistance to meropenom, aztreonem, piperacillin/tazobactum and 99% to carbapenem.  All isolates carried blaOXA-23 and blaOXA-51, but none carried a blaOXA-24 like or blaOXA-58. The isolates also were positive for NDM-1, NDM, VIM, GES, KPC and SPM at the rates of 29%, 20%, 29%,19%,7% and 2%, respectively.  Class 1 Integron was positive in 82% of A. baumanniiisolates. The clonal relationship of 42 MDR A. baumanniiisolates using ERIC-PCR and constructed dendrogram showed 3 major genotype clusters of genetically related isolates. These include 4 genotype groups, each composed of 2 isolates with 100 % similarity of DNA bands.  Conclusion:This study demonstrates that A. baumannii colonize frequently cancer patients in association with antibiotic treatment. The organism is mostly carrying wide spectrum of antibiotic resistance genetic factors, especially many types of ESBLs and MBLs and Class 1 Integron. This fact should be considered when therapy is selected for treatment of patients infected with MDR A. baumannii. Key words. Acinetobacter baumannii, ESBLs, MBLs, Class 1 Integron, Jordanian cancer patients.