Correlation between Extended Spectrum Beta-lactamase Production and Biofilm Formation in Gram-negative Bacteria: A Laboratory-based Pilot Study

Abstract

Introduction: Gram-negative bacteria are among the most common causes of community-acquired, nosocomial,
and opportunistic infections. The recent increase in biofilm formation and extended-spectrum beta-lactamase
(ESBL) production in bacteria has led to widespread multidrug resistance, creating significant treatment challenges.
This study aimed to investigate the antibiotic susceptibility profile, biofilm formation, and molecular detection of
ESBL-encoding genes in clinical gram-negative isolates. Materials and Methods: Thirty Gram-negative isolates
were collected from a tertiary care hospital, and the Kirby-Bauer disk diffusion method was used to assess antibiotic
susceptibility. The double-disk synergy test phenotypically confirmed the production of ESBL. Biofilm formation
was evaluated using the crystal violet microtiter plate method. Molecular characterization of ESBL genes (blaTEM,
blaSHV, blaCTX-M, and blaCTX-M-15) was performed using polymerase chain reaction. Results: Of the 30 isolates,
8 (26.7%) were phenotypically confirmed as ESBL producers. All isolates (100%) carried the blaTEM gene, while
blaSHV, blaCTX-M, and blaCTX-M-15 were detected in 30%, 33.3%, and 50% of isolates, respectively. Notably, blaCTX-M
was absent in Acinetobacter baumannii and Klebsiella pneumoniae. Resistance to gentamicin was observed in 100%
of isolates, whereas Escherichia coli and K. pneumoniae showed lower resistance rates to amoxicillin-clavulanate.
Regarding biofilm formation, 15 isolates (50%) were identified as biofilm producers. Conclusion: This study
concluded that isolates were extensively drug resistant, and biofilm producers tended to be less drug-resistant.