Prevalence of Metallo-β-Lactamases Genes and Integrons in Acinetobacter baumannii Isolates

Acinetobacter baumannii
Acinetobacter baumannii
Researchers conducted a study to detect the genes encoding metallo-β-lactamases and integrin structures in Acinetobacter baumannii isolates obtained from patients with burns.

Isolates of multi-drug resistant (MDR) Acinetobacter baumannii obtained from patients with burns had a high prevalence of genes encoding for metallo-β-lactamases (MBL) enzymes, according to study results published in BMC Infectious Diseases.

The most common mechanism for antimicrobial resistance in A baumannii are MBLs, which are usually associated with gene cassettes of integrons that are easily passed between bacteria. Researchers investigated the presence of class 1 integrons and associated gene cassettes, as well as MBL-encoding genes such as blaVIM and blaIMP, in isolates obtained from patients with burns in Tehran.

A total of 106 unique A baumannii isolates were analyzed, all of which (100%) were MDR. All isolates were sensitive to colistin (minimum inhibitory concentration [MIC], ≤2 mcg/mL) and resistant to imipenem (MIC, ≥ 8 mcg/mL). Class 1 integrons were identified in 62 (58.5%) of the isolates, of which 49 (79.0%) had at least 1 gene cassette. Mapping of integrons showed 3 different gene cassettes including, arr2, cmlA5, and qacE1 which occurred in 44 (70.9%) isolates; arr-2, ereC, aadA1, cmlA7, and qacE1 which occurred in 2 (3.2%) isolates; and aac(3)-Ic and cmlA5, which occurred in 3 (4.8%) isolates. Among the 106 A baumannii isolates, the frequency of blaVIM and blaIMP was 102 (96.2%) and 62 (58.5%), respectively, And 60 isolates (56.6%) carried both genes.

According to the researchers, the study was limited by its cross-sectional design and lack of resources. In addition, this was the first time the gene cassette arrays cmlA5 and cmlA7 were detected in strains of A baumannii in Iran. “The data obtained in the present study may provide a basis for future studies,” the researchers concluded.


Nikibakhsh M, Firoozeh F, Badmasti F, Kabir K, Zibaei M. Molecular study of metallo-β-lactamases and integrons in Acinetobacter baumannii isolates from burn patients. BMC Infect Dis. 2021;21(1):782. doi: 10.1186/s12879-021-06513-w