Drug resistance profile and biofilm forming potential of Pseudomonas aeruginosa isolated from contact lenses in Karachi-Pakistan

Abstract

Background: The contaminated contact lens provides Pseudomonas aeruginosa an ideal site for attachment and biofilm production. Continuous contact of the eye to the biofilm-infested lens can lead to serious ocular diseases, such as keratitis (corneal ulcers). The biofilms also prevent effective penetration of the antibiotics, which increase the chances of antibiotic resistance.

Methods: For this study, 22 Pseudomonas aeruginosa isolates were obtained from 36 contact lenses and 14 contact lens protective fluid samples. These isolates were tested against eight commonly used antibiotics using Kirby-Bauer disk diffusion method. The biofilm forming potential of these isolates was also evaluated using various qualitative and quantitative techniques. Finally, a relationship between biofilm formation and antibiotic resistance was also examined.

Results: The isolates of Pseudomonas aeruginosa tested were found resistant to most of the antibiotics tested. Qualitative and quantitative biofilm analysis revealed that most of the isolates exhibited strong biofilm production. The biofilm production was significantly higher in isolates that were multi-drug resistant (p < 0.0001).

Conclusion: Our study indicates that multi-drug resistant, biofilm forming Pseudomonas aeruginosa isolates are mainly involved in contact lens associated infections. This appears to be the first report from Pakistan, which analyzes both antibiotic resistance profile and biofilm forming potential of Pseudomonas aeruginosa isolates from contact lens of the patients with contact lens associated infections.

Figure 1

Antibiogram for Pseudomonas aeruginosa isolates. Antibiotic resistance or susceptibility profile was developed by testing Pseudomonas aeruginosa isolates against eight commonly prescribed antibiotics. Light grey bar represents number of susceptible pathogens while dark grey bar shows number of resistant pathogens.

Figure 2

Qualitative analysis of biofilm formation by Pseudomonas aeruginosa. Pictures showing A) dense matt formed at the Air-liquid interface in glass tube (pointed by arrow), B) microorganisms adhered to the surface of polystyrene surface stained with Crystal Violet. A and B) The experiment was performed using tube method. Biofilm formation by Pseudomonas aeruginosa as observed C) under inverted microscope using Air-liquid interface assay, D) under compound microscope using Air-Liquid interface cover slip assay. Dense matt formation and microbial aggregation is clearly evident in the C) wells and D) on the slides.

Figure 3

Quantitative analysis of biofilm formation by Pseudomonas aeruginosa. Graph showing different OD obtained for each isolate as calculated by 96- well microtitre plate assay. The experiment was performed in duplicate and the error bars represents standard error of their mean.