Dissemination of Classes 1, 2, and 3 Integrons in Acinetobacter baumannii Strains Recovered from Intensive Care Units Using Polymerase Chain Reaction-Restriction Fragment Length Polymorphism

Acinetobacter baumannii as the most important nosocomial pathogen can cause various types of clinical infections. Multidrug resistance in A. baumannii strains has significantly limited the choice of available therapeutic options for treatment of patients and is a serious threat to hospitalized patients, especially those in intensive care units.
The present study was performed to investigate the frequency of classes 1, 2, and 3 integrons in A. baumannii strains isolated from selected hospital ICUs.
A total of 105 A. baumannii isolates were collected between October 2015 and April 2016 from 4 medical centers located in different regions of Tehran, Iran. The resistance rate to different classes of antimicrobial agents was assessed using Epsilometer test. Conventional PCR was performed for the detection of blaOXA-51-like gene and integrase gene. Restriction Fragment Length Polymorphism technique using RsaI and HinfI restriction enzymes was used to detect integron classes.
All the isolates were observed to be susceptible to colistin and polymixin B and inhibited at similar minimum inhibitory concentration (MIC) 50 (MIC50) and MIC90 1 µg/mL. All the tested A. baumannii isolates were multidrug resistant. The rate of extensive drug-resistance among these clinical isolates was 71.4%. The highest and the lowest levels of resistance were observed to be related to ciprofloxacin (96.2%) and netilmicin (40%), respectively. Resistance rates to other antibiotics tested were between 43.8% and 80%. The prevalence of classes 1 and 2 integrons was found to be 66.7% and 20%, respectively. Class 3 integron was reported, for the first time, in three A. baumannii strains (2.9%) isolates from Tehran, the capital of Iran.
The results revealed that the dissemination of multi-drug resistance among A. baumannii isolates may be associated with the presence of integrons. The findings highlighted the need for continuous surveillance to monitor integrons among A. baumannii strains. 