الفهرس 
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Abstract
Staphylococci are the leading ocular isolates worldwide among the Gram-positive bacteria, and P. aeruginosa is the major Gram-negative bacteria isolated from ocular infections. Thus, the aim of our work was to study the bacterial profile of the two most common forms of ocular infections (keratitis and endophthalmitis) in order to come up with concrete information for effective management of such infections and to investigate the relation between eye diseases and virulence factors of both P. aeruginosa and S. aureus using PCR technique. In addition, the antimicrobial susceptibility patterns of clinically isolated P. aeruginosa and S. aureus were determined by the disk-diffusion method. Fifty three P. aeruginosa isolates and fifty S. aureus isolates were recovered from 180 specimens isolated from patients suffering different ocular infections who were admitted to MOC and EH. Regarding P. aeruginosa isolates, 39 of them were isolated from BK and 16 from BE. Regarding S. aureus isolates, 19 of them were isolated from BK and 31 from BE. The antimicrobial susceptibility patterns of P. aeruginosa isolates were done using disc diffusion method against a panel of anti-pseudomonal antimicrobials as follows: ceftazdime (CAZ, 30 µg), cefepime (FEP, 30 µg), lomefloxacin (LOM, 30 µg), ofloxacin (OFX, 5 µg), ciprofloxacin (CIP, 5 µg), polymyxin B (PB, 300 units), gentamycin(CN, 10 µg) and tobramycin (TOB, 10 µg). Cefepime was the least effective antibiotic where, BK and BE isolates exhibited 75.6% and 93.75% resistance to this antibiotic, respectively, followed by lomefloxacin (58.4%). On contrast, polymyxin B was the most effective antimicrobial agent against all P. aeruginosa isolates. Regrading gentamicin, ciprofloxacin, ofloxacin, tobramycin and ceftazidime, they showed nearly similar resistance percent with moderate activity ranged from (42%-56%). Indeed, 62% and 50% of BK and BE P. aeruginosa isolates were MDR respectively. The prevalence of different virulence genes of P. aeruginosa was determined by PCR. Our results showed that the order of the virulence genes among P. aeruginosa BK isolates from highest to lowest was PeIA, AprA, Exo-Y, Exo-S, ToxA, Exo-U and then LasB. Regarding BE isolates, our results revealed that the order from highest to lowest was Exo-S, AprA, PeIA, Exo-U, Exo-Y, LasB and then ToxA. Generally, alkaline protease encoding gene (AprA) and biofilm encoding gene (PelA) were the most predominant among our isolates. On the contrary, ToxA and lasB were the least prevalent genes. For P. aeruginosa isolated from BK, Exo-Y was amplified in (72%) isolates, while Exo-U and Exo-S were amplified in (64.8% and 70.2%) isolates respectively. While in case of BE, the most prevalent of type three secretion genes was Exo-S (93%), while Exo-Y and Exo-U both were harbored by same percent (75%). In case of S.aureus isolated from BE, IcaD was the most common gene as it was amplified in 90.32% of isolates. While Hla gene was the least detected toxin gene as it was amplified by 48.38%. It was noticed that biofilm encoding gene were ampilifed by (90.32 and 83.8%) for IcaD and IcaA respectively. Concerning geh was amplified by 80.6% and Cna was amplified by 48.3%.