Survey of Integron Types and Carbapenem Resistance Encoding Genes in Acinetobacter Baumannii Isolated from Burn Wound Samples

  Acinetobacter baumannii is one of the most important pathogenic bacteria that causes nosocomial infections, especially in burned patients. In recent years, Carbapenems have been considered as a selective antibiotic in the treatment of multi-drug resistant A. baumannii, but the rapid appearance of carbapenem-resistant A. baumannii has been reported worldwide. The purpose of this study was to investigate different classes of integron and Carbapenem-resistance encoding genes in A. baumannii isolated from burn wound samples in Shahid Motahari Hospital in Tehran.
Material and In this descriptive cross-sectional study, 70 samples of A. baumannii were collected from burn injured patients referred to the Motahari Hospital. After identification and confirmation of strains, an antibiotic susceptibility test was performed using disk diffusion agar test. Also, metallo-β-lactamases producing isolates were identified using combined disk and E-test. BlaKPC producing strains were also identified using modified Hodge test. Finally, in order to evaluate genomic strains, after DNA extraction using boiling method, the PCR reaction for intI, intII, intIII, IMP, VIM, NDM, OXA-23-like, OXA-24-like, OXA genes -85-like, OXA-51-like and KPC. In this study, all A. baumannii isolates were resistant to ciprofloxacin, cefotaxime, piperacillin and Trimethoprim/sulfamethoxazole. Out of 67 imipenem-resistant isolates, 57 (85.1%) and 61 (91%) isolates were considered as MBL producing in combination phenotypic tests and E-test. 44 (65.6%), 21 (31.3%) and 1 (1.5%) isolates were positive for blaVIM, blaIMP and blaNDM genes, respectively. So, 52 (77.6%) and 27 (40.3%) had OXA-23 and OXA-24 genes. 11 (15.7%) isolates were positive for KPC production in the Modified Hodge Test, but only 27.3% (3 strains out of 11 isolates) were carrying blaKPC gene. Also, 12 (17.1%), 54 (77.1) and 3 (4.3%) isolates, were carrying intI, intII and intIII genes, respectively. The increased frequency of carbapenem-resistant A. baumannii in burn patients suggests choosing an appropriate antibiotic regimen based on the antibiotic susceptibility pattern of the isolates. The rapid identification of carbapenemase-producing strains is helpful to select suitable options for antimicrobial therapy and prevent the further spread of their encoding genes