Prevalence of β-lactamase-encoding genes and molecular typing of Acinetobacter baumannii isolates carrying carbapenemase OXA-24 in children

Background: beta-Lactam antibiotics have been broadly used for the treatment of Acinetobacter baumannii infections, resulting in development of beta-lactam inactivating beta-lactamases. Here, we described antibiotic resistance rate, prevalence of beta-lactamase-encoding genes, and clonal relationships of A. baumannii strains isolated from children referred to Children's Medical Center in Tehran, Iran, during 2019-2020. Methods: A total of 60 non-replicate A. baumannii isolates were recovered from clinical specimens of pediatric patients. Antibiotic susceptibility testing was done by the disc diffusion method. Colistin susceptibility of isolates was performed by the broth microdilution method. beta-lactamase-encoding genes were characterized by PCR. The presence of ISAba1 element upstream of the several oxacillinase genes was also checked. Genetic relatedness of isolates was determined by using random amplification of polymorphic DNA (RAPD) typing. Results: The antimicrobial susceptibility tests showed that 83.3% of A. baumannii isolates were MDR, and 40% XDR. Both MDR and XDR A. baumannii isolates were susceptible to colistin. The frequency of bla(OXA-51-like), bla(OXA-23-like), bla(TEM), bla(OXA-24-like), bla(PER), bla(SHV), bla(CTX-M), bla(OXA-58-like), and bla(IMP) was 100, 93.33, 60, 36.67, 28.33, 8.33, 5, 3.33, and 1.67%, respectively. Coexistence of ISAba1/bla(OXA-23-like) and ISAba1/bla(OXA-51-like) was observed in 65% and 85% of isolates, respectively. RAPD analysis revealed 4 common types and 2 single types of A. baumannii isolates. Conclusions: The multiple clones harboring bla(OXA-23-like), ISAba1-bla(OXA-51-like), and ISAba1-bla(OXA-23-like) were responsible for the spread of A. baumannii isolates in our clinical wards. Dissemination of the well-established clones is worrisome and would become therapeutic challenges due to the possible transferring genetic elements associated with resistance.

Automated summary

The study examined the antibiotic resistance, prevalence of beta-lactamase-encoding genes, and clonal relationships of Acinetobacter baumannii strains isolated from pediatric patients in Tehran, Iran. The results showed high rates of multi-drug resistant and extensively drug-resistant isolates, with certain beta-lactamase genes being prevalent. The presence of well-established clones poses a potential therapeutic challenge due to genetic elements associated with resistance.