Resistance pattern and distribution of carbapenemase and antiseptic resistance genes among multidrug-resistant Acinetobacter baumannii isolated from intensive care unit patients.

PURPOSE: Nosocomial infections caused by multidrug resistant Acinetobacter baumannii have emerged as a serious problem in healthcare settings worldwide.

METHODOLOGY: A total of 100 A. baumannii clinical isolates from immunocompromised patients hospitalized in ICUs in Iran were investigated for antimicrobial susceptibility and the presence of carbapenemase and antiseptic resistance genes.

RESULTS: All isolates were resistant to one or more antibiotics, with the most frequent resistance found against ciprofloxacin and imipenem (100 %) and piperacillin (99 %). The MICs of biocides were determined by the agar dilution method. No apparent resistance to biocides was seen among the 100 A. baumannii isolates. All isolates were effectively inhibited by the user's defined concentrations of cetrimide, benzalkonium chloride and glutardaldehyde. The intrinsic β-lactamase gene, blaOXA-51-like, was detected in all A. baumannii isolates. Coexistence of blaOXA-51 andblaOXA-23 was encountered in 89 % of isolates. However, genes blaOXA-58, blaSIM and blaIMP were not detected in any isolates. While A. baumannii isolates were sensitive to biocides, they carried qac genes with the qacEΔ1 gene being the most common, at a frequency of 91 %.

CONCLUSION: Our study revealed the high frequency of multidrug- and carbapenem-resistant isolates of A. baumannii in ICU patients, with a high prevalence of the genes blaOXA-23 and blaOXA-51. However, no apparent biocide resistance was seen in A. baumannii isolates. It appears that appropriate surveillance and control measures are essential to prevent the emergence and transmission of MDR A. baumannii in Iran.