Antibiotic Resistance Patterns and Detection of OXA-23 and OXA-48 Genes in Acinetobacter baumannii Isolated from Ventilator Associated Pneumonia

     Acinetobacter baumannii is one of the important causes of nosocomial infection worldwide. Patients who use ventilator are in high risk of ventilator association pneumonia (VAP) caused by nosocomial pathogens such as A. baumannii.  Carbapenem is one of the last lines of antibiotic therapy in MDR A. baumannii infections. Then, carbapenem resistant strains are a very important challenge for physicians. OXA types carbapenemase enzymes are important mechanisms to carbapenem resistance in A. baumannii. The aim of this study was to determine oxa-23 and oxa-48 producing A. baumannii isolated from VAP. 

      In this cross-sectional study, 51 sputum specimens from VAP in hospitalized patients in Hazrat-E-Rasul Hospital, Tehran, Iran were used. Antibiotic susceptibility testing was done after identification according to CLSI 2018. DNA extraction was done by boiling assay and oxa-23 and oxa-48 genes were detected by PCR. Thirty- two (63%) A. baumannii were confirmed according to microbiological and biochemical tests.  

      The highest resistance was observed against Piperacillin, Cefotaxime, Ciprofloxacin and Ceftazidime with 97% antibiotic resistance, and ampicillin/Sulbactam was the most effective antibiotic (78% sensitivity). Generally, 31 isolates of A. baumannii harbored the oxa-23 gene and none of them had oxa-48. The high prevalence of MDR A. baumannii in VAP is a great problem, especially for the nosocomial infection committee in hospitals.

     Rapid detection of MDR and carbapenemase producing strains can be the first step in preventing their spread in hospitals.