Characterization of Carbapenem-resistant biofilm forming Acinetobacter baumannii isolates from clinical and surveillance samples.

Background A. baumannii is an important nosocomial pathogen responsible for a wide range of human infections. The emergence of multi-drug resistance causes life-threatening hospital-acquired infections. Also, the formation of biofilm helps it survive on abiotic surfaces and transfer through health care workers, thereby causing nosocomial infections like ventilator-associated pneumonia and catheter-associated urinary tract infections. Hence, we undertook to study the current scenario of antibiotic resistance patterns and virulence factors in our clinical and colonizing isolates. Materials and methods A total of 92 isolates (44 colonizing and 48 clinical) of Acinetobacter baumannii were included in the study. These isolates were from clinical and surveillance samples (nasal and throat swabs) taken from patients. Antibiotic susceptibility testing was performed by VITEK 2. Biofilm formation was assessed by the tissue culture plate method. PCR for oxacillinases, MBLs and biofilm-associated genes were performed. Results 42 (87.5%) of the clinical and 44 (97.7%) of the colonizing isolates were resistant to meropenem. A strong adherent biofilm was produced by 11 (22.91%) of the clinical and 12 (27.27%) of the colonizing isolates. No statistically significant difference was observed between strong biofilm-producing and meropenem-resistant isolates (p value = 0.75). Biofilm-associated genes, omp A, bap and csu E were present in all the colonizing isolates and 45 (93.7%), 47 (97.9%) and 44 (91.6%) of the clinical isolates respectively. bla _{OXA−51−like} was present in all the isolates. bla _OXA23−like was more prevalent in colonizing 43 (97.7%) than clinical isolates 42 (87.5%). bla _{OXA−58−like} was present in 9 (20.4%) and 6 (12.5%), bla _{OXA−24−like} was present in 1 (2.3%) and 2 (4.1%) of the colonizing and clinical isolates respectively. The presence of MBLs was observed to be lower than oxacillinases. NDM1 was present in 15.29%, SIM in 27%, GIM in 14.11%, VIM in 32.9%, SPM in 5.8% and IMP in 1.2% of the meropenem-resistant isolates. Conclusion Carbapenem resistance (XDR) is increasing in Acinetobacter baumannii . Biofilm formation is an important virulence factor responsible for its survival in the hospital environment and causes nosocomial infections. Biofilm-producing isolates were also found to be Carbapenem-resistant. Strict disinfection procedures are to be followed to prevent its spread in the hospital.