Genomic analysis of virulence factors of nosocomial MDR A. baumannii from a tertiary care hospital.

UNLABELLED: Acinetobacter baumannii has evolved over the years into predominant nosocomial multidrug-resistant (MDR) pathogen, especially associated with ventilator-associated pneumonias (VAPs). About one-third of VAPs can cause bloodstream infections. MDR A. baumannii causing VAP is associated with significant longer hospital stays and mortality. We carried out the genomic analysis of MDR A. baumannii by whole-genome sequencing (WGS) to study the various virulence factors involved in biofilm formation and pathogenic mechanisms. A total of 44 MDR A. baumannii isolates recovered from respiratory and blood specimens of patients on mechanical ventilators are included in the study. All isolates were identified by Vitek2 and matrix-assisted laser desorption/ionization-time of flight mass spectrometry and confirmed by WGS. Different virulence factor (VF) genes identified by WGS were analyzed. The most common VF genes found in all isolates of A. baumannii were ompA (97.7%) and lps-o gene (100%) related to adherence, adeF (100%), adeG (95.5%), and adeH (97.7%) (AdeFGH efflux pump-related VF genes) and pgaA and pgaD (100%), pgaB and pgaC (97.7%) related to biofilm formation, plc and plcD (100%) related to enzyme and immune evasion related capsular gene (100%) and lpsB, lpxA, lpxC, lpxD, lpxL, and lpxM found in all isolates respectively. This study is amongst a few such studies done using WGS in India. These findings have improved our understanding of the various pathogenic mechanisms underlying A. baumannii. This study will also give some insight into how hindering the pathways of virulence mechanism can be used to develop treatment strategies for MDR A. baumannii.

IMPORTANCE: Acinetobacter baumannii is a significant cause of mortality in nosocomial infections, particularly ventilator-associated pneumonia (VAP). The evolution of A. baumannii from an avirulent organism to a multidrug-resistant (MDR) nosocomial pathogen is very interesting. The acquisition of multiple drug-resistant genes is also accompanied by the acquisition of many virulence genes. Information regarding genomic studies of different virulence factors in such MDR strains, prevalent in this geographical region, were not performed in the past. The strains of A. baumannii may vary depending on the geographical location and use of antibiotics in those hospital setups. Control of A. baumannii nosocomial infections requires taking strict hospital infection control measures. We trust that this would suggest some new insights into the control of A. baumannii in our intensive care units to reduce the burden of such a dreadful nosocomial pathogen.