Resistome, virulome and genomic insights into the silent dissemination of Acinetobacter baumannii during the COVID-19 pandemic in Brazil.

INTRODUCTION

Acinetobacter baumannii is a Gram-negative opportunistic pathogen frequently associated with severe nosocomial infections, particularly in immunocompromised patients. Its remarkable ability to acquire and disseminate antimicrobial resistance mechanisms promotes its persistence in hospital environments, representing a major challenge for infection control.

METHODS

This study aimed to characterize clinical A. baumannii strains recovered from colonization samples of patients with laboratory-confirmed SARS-CoV-2 infection in Brazil between May 2021 and April 2022, focusing on antimicrobial resistance profiles, virulence determinants, and genomic diversity. A total of 16 clinical strains obtained from nasopharyngeal, tracheal, and blood samples were analyzed. The strains were identified by MALDI-TOF mass spectrometry, subjected to antimicrobial susceptibility testing by disk diffusion, and subsequently characterized by whole-genome sequencing.

RESULTS

Among the 16 strains analyzed, 15 (93.8%) were classified as multidrug-resistant (MDR) and exhibited carbapenem resistance, being classified as carbapenem-resistant A. baumannii (CRAB). Resistance to imipenem and meropenem was observed in 93.8% (n=15) and 87.5% (n=14) of the strains, respectively. Whole-genome sequencing revealed the presence of important resistance determinants, including blaOXA-23-like, armA, tet(B), and mph(E)/msr(E). Analysis of virulence factors identified genes associated with pilus formation and cellular adhesion, a complete pga operon involved in biofilm production in most strains, as well as widely distributed quorum sensing systems and iron acquisition mechanisms.

DISCUSSION: Collectively, the results demonstrate the widespread dissemination of MDR/CRAB A. baumannii lineages during the COVID-19 pandemic in Brazil, supported by a diverse repertoire of genetic determinants associated with antimicrobial resistance and virulence. These findings highlight the importance of continuous genomic surveillance and strengthened infection prevention and control strategies to mitigate the risk of hospital outbreaks caused by this pathogen.