Characterization of virulence factors, antimicrobial resistance patterns and biofilm formation of Pseudomonas aeruginosa and Staphylococcus spp. strains isolated from corneal infection

Abstract

Infectious keratitis is a serious ocular infection that can lead to severe visual impairment and blindness. Bacterial pathogens are responsible for nearly half of infectious keratitis cases. This study was performed to determine the virulence factors, antimicrobial resistance patterns, and biofilm formation ability of Pseudomonas aeruginosa and Staphylococcus spp. strains isolated from corneal infections. A total of 56 corneal scraping samples were collected over 8 months. P.aeruginosa and staphylococcal strains were identified by phenotypic and genotypic methods. Determination of multidrug resistance was performed according to its definition of multidrug resistance (MDR). Detection of antimicrobial resistance genes and determinants of virulence were also performed using standard procedures. Biofilm formation ability of the isolates was determined by colorimetric microtitration plate assay and Modified Congo red agar (MCRA). In the present study, P.aeruginosa, MSSA, MRSA, MS-CoNS and MR-CoNS strains were isolated from corneal infections. Multidrug resistance was observed in 42.9% and 57.1% of P.aeruginosa and Staphylococcus spp., respectively. The most frequent virulence genes among P.aeruginosa strains were exoA and exoS (100%) followed by exoU (71.4%) and lasB (28.6%). All the P.aeruginosa isolates were biofilm producers and carried the algD gene (100%). All staphylococcal strains were negative for pvl gene amplification. Biofilm formation was also observed in 4 (57.1%) isolates. Both icaA and icaD genes were detected in the biofilm producers. Our results indicated that P.aeruginosa and Staphylococcus spp. were the most prevalent bacterial agents that cause corneal infections. However, their virulence traits and biofilm formation ability were noteworthy.