Genetic features of Pseudomonas aeruginosa isolates associated with eye infections referred to Farabi Hospital, Tehran, Iran.

BACKGROUND: Pseudomonas is the most common cause of microbial keratitis especially in people who use contact lens. The virulence of Pseudomonas aeruginosa in different eye infections is associated with different virulence factors . METHODS: In this study, 54 P. aeruginosa isolates including 39 isolates from keratitis and 15 isolates from conjunctivitis were evaluated for their ability to form biofilm, production of protease, elastase, alkaline protease and their antibiotic-resistant patterns. The distribution of the exoS and exoU genes in the test strains were determined using PCR assays. RESULTS: Most of the eye infections (90.74%) were seen in people who used contact lenses, and in most of patients (72.22%), the infection was presented as keratitis. None of the isolates were resistant to a single antibiotic as tested. Multidrug resistance (MDR) was detected in two isolates (3.5%) which were resistant to more than one category of antibiotics. The exoU+/exoS+ isolates were in majority although in total, compared to exoS, there were more exoU in a greater number of samples. Most of the strains produce elastase but among all of ocular isolates, only 5.8% of the strains showed alkaline protease activity. Most of the ocular isolates were not capable of producing biofilm. CONCLUSIONS: In our study, a high prevalence of virulence factors was observed in P. aeruginosa isolates from contact lens wearer with keratitis. As the P. aeruginosa isolates from different infection origins and different geographic region may have different virulence factors, having a better perception of these differences could help to improve development of clinical instructions for the control of keratitis.

Different Genotypes of Adhesion Operon Genes in Staphylococcus epidermidis Isolates From Various Ocular Infections.

BACKGROUND: Staphylococcus epidermidis is one of the common causes of bacterial keratitis and post-operation infections. One of the most important virulence factors of S. epidermidis is biofilm formation. Poly-N-acetylglucosamine (PNAG) production is critical for biofilm formation in S. epidermidis. The intercellular adhesion (ica) operon is formed by icaA, icaD, icaB, and icaC genes, which participate in the biosynthesis of PNAG. Strains of S. epidermidis from different infections show different genotypes in relation to adhesion operon genes. Therefore, regarding the fact that the pathogenic strain in each community has unique genotypes, this study investigated the relation between ica operon genotypes and various ocular infections. However, the correlation between the ica operon genes and the mecA gene was analyzed in the isolates. METHODS: For this study, samples of the conjunctiva, cornea, and intraocular fluid of patients with ocular infection were collected. After culture and incubation, detection of S. epidermidis was performed using biochemical and coagulase tests. The antibiotic susceptibility of the bacteria was evaluated by the disk diffusion method. After this, DNA was extracted from the bacteria and the presence of icaA, icaD, is256, and mecA genes was analyzed using polymerase chain reaction. RESULTS: All 50 coagulase-negative Staphylococcus samples isolated from different eye infections were characterized as S. epidermidis. Most of the samples (36%) were isolated from the cornea and the others were, respectively, from the conjunctiva (24%), vitreous (20%), anterior chamber (8%), eyelid (6%), and nasolacrimal duct (6%). The icaA, icaD, and is256 genes were detected with different genotypes in isolates from keratitis and endophthalmities compared with conjunctivitis. Overall, the most isolated genotype from ocular infections was icaA+. icaD+. is256+. (46%). Most of the isolates (82.60%) had mecA, icaA, and icaD genes simultaneously, which indicates a strong relationship between the adhesion genes and the antibiotic resistance gene. CONCLUSIONS: The adhesion operon genes were observed with different genotypes in S. epidermidis samples isolated from various ocular infections.