Prevalence of carbapenem-hydrolyzing OXA-type ß-lactamases among Acinetobacter baumannii in patients with severe urinary tract infection.

Acinetobacter baumannii produces carbapenemase-hydrolyzing class D ß-lactamases (CHDLs) as one of the major drug resistance mechanisms. This investigation is thus aimed to assess the prevalence and to characterize the CHDL-producing strains of A. baumannii by both phenotypic assays and genotypic characterization. A total of 73 isolates of A. baumannii were phenotypically and genotypically characterized from patients (N = 1,000) with severe urinary tract infection. Tested strains were subjected to double disk synergy testing by Kirby-Bauer disk diffusion method with modified Hodge test (MHT) for carbapenemase production. Plasmid DNA was molecularly screened for CHDL-encoding blaoxa-51, blaoxa-23, and blaoxa-143 genes by polymerase chain reaction. Carbapenem-resistant profile showed 100%, 61.64%, and 67.12% resistance by Kirby-Bauer disk diffusion method that correlated with MHT positivity for 100% (n = 73), 80% (n = 36), and 78% (n = 38) of the isolates against imipenem, doripenem, and meropenem, respectively. The blaoxa-51 and blaoxa-23 were observed in 41.09% (n = 30) and 35.61% (n = 26) with co-occurrence in 4.10% (n = 3) of the isolates. MHT-positive isolates showed 100%, 91.66%, and 71.4% for blaoxa-51 and 91.78%, 51.11%, and 34.69% for blaoxa-23 with imipenem, doripenem, and meropenem resistance, respectively. None of the strains yielded blaoxa-143 gene. The findings of this study showed prevalence of carbapenem resistance and high frequency of blaoxa-51 and blaoxa-23 among A. baumannii.

Prevalence of VIM- and GIM-producing Acinetobacter baumannii from patients with severe urinary tract infection.

Carbapenems are administered as the final drug of choice for treating complicated nosocomial infections caused by multidrug-resistant Acinetobacter baumannii strains. It is currently a worldwide issue that metallo-ß-lactamases (MBLs) as carbapenem-hydrolyzing enzymes are one of the major drug resistance mechanisms. This investigation is thus aimed to assess the prevalence and characterize the MBL-producing strains of A. baumannii both by phenotypic assays and by genotypic characterization. A total of 73 isolates of A. baumannii were phenotypically and genotypically characterized from patients (N = 1,000) with severe urinary tract infection. Tested strains were subjected to double disc synergy testing (DDST) by Kirby-Bauer disc diffusion method with imipenem (IMP) and IMP/EDTA combination discs. Plasmid DNA was molecularly screened for MBL-encoding blaIMP, blaVIM, blaGIM, and blaNDM genes by PCR for the genetic relatedness of the MBL genes with carbapenem resistance. Carbapenem resistance profile showed 100%, 45%, and 49% non-susceptibility against imipenem, doripenem, and meropenem, respectively. Altogether 42.46% (n = 31) of the isolates showed MBL production upon double disc phenotypic test with IMP and IMP/EDTA discs. The blaVIM and blaGIM were detected in 34.24% (n = 25) and 16.43% (n = 12) of the isolates, respectively, while the co-occurrence of blaVIM and blaGIM was 2.73% among the isolates. DDST-positive isolates showed 21.19% and 9.58% strains positive for blaVIM and blaGIM, respectively, whereas 1.36% of the strains for both genes. None of the strains yielded blaIMP and blaNDM genes. The findings of this study showed prevalence of carbapenem resistance among A. baumannii from urine samples and the frequency of blaVIM and blaGIM.