Antimicrobial susceptibility and detection of β-lactamases in gram-negative bacilli causing neonatal infections

Abstract

Introduction: Neonatal gram-negative bacillus infections are on the rise and are associated with increased morbidity and mortality.

Objective: Describe the behavior of resistance to therapeutically important antimicrobials in the management of neonatal infections by gram-negative bacilli, identify the mechanisms involved in resistance to beta-lactams, and determine the frequency of multidrug-resistant, extreme drug-resistant, and pandrug-resistant isolates.

Methods: During the months of February to December 2021, a retrospective descriptive cross-sectional study was carried out at the National Reference Laboratory of Healthcare Associated Infections of the Tropical Medicine Institute “Pedro Kourí”, which included 120 isolates of gramnegative bacilli causing neonatal infection in 6 Gyneco-Obstetric and Pediatric Hospitals in Havana, which are part of the culture collection of the laboratory itself, and were received between September 2017 and July 2020. Antimicrobial susceptibility was evaluated by the Kirby- Bauer Method. Production of Extended Spectrum Betalactamases (ESBL), AmpC-type β-lactamases, and metallo-β-lactamase-type carbapenemases were determined by the discs combined with inhibitors method. Finally, the isolates were classified according to their antibiotype into multidrug-resistant, extreme drug-resistant, and pandrug-resistant.

Results: The isolated Gram-negative bacilli showed high resistance to aminopenicillins, third-generation cephalosporins, ciprofloxacin, and gentamicin. Production of β-lactamases was detected in 38.4 %, ESBL predominated with 32 %, followed by AmpC with 5 % and metallo-β-lactamases with 2 %. Carbapenems and colistin were found to be 100 % sensitive against ESBL- and AmpC-producing organisms. Among of the isolates with β-lactamase production, 96 % were MDR and 4.2 % XDR.

Conclusions: The results of the study suggest that antimicrobial resistance in gram-negative bacilli that cause infections in newborns constitutes a health problem in Havana hospitals, and reveal the need for continuous monitoring of the antimicrobial susceptibility of these pathogens.