Iraqi Postgraduate Medical Journal

Abstract

ABSTRACT:
BACKGROUND:
Pseudomonas aeruginosa (P. aeruginosa) is the most frequently isolated bacteria in clinical cases of ulcerative keratitis. P. aeruginosa produces several proteases and toxins, the best characterized being exotoxin, elastase, alkaline protease and IV. These are all important factors in the establishment of bacterial infection and the amount of damage caused by the infection to the cornea.
OBJECTIVE:
The aim of the present study was to study the role of P. aeruginosa proteases ( elastase ( LasB) , LasA, Alkaline protease, and protease IV ) in corneal ulceration by using Real - time PCR.
METHODS :
One hundred - twenty clinical samples (corneal scraping) were collected from patients suspected with bacterial keratitis presenting to Ibn –Alhaytham Teaching Hospital from May 2013 until November 2013. Methods for isolation and identifying P. aeruginosa based upon culture coupled with biochemical tests and confirmed by new technique called Vitek 2 compact system. The role of proteases enzymes ( elastase ( LasB), LasA, alkaline protease and protease IV ) of P. aeruginosa in the corneal ulceration was studied by Real – time PCR.
RESULTS :
Real time aalysis demonstrated that three bacterial isolates of P. aeruginosa were possessed elastase gene (11.5%), one bacterial isolate was harbored LasA gene (3.8%), twenty bacterial isolates were possessed protease IV gene ( 76.9%) , and all bacterial isolates were possessed alkaline protease gene (100%).
CONCLUSION:
The presence of the alkaline protease and protease IV genes in almost bacterial isolates of P. aeruginosa improved the fact that these enzymes were not only tissue damaging but also very important colonizer agents to cornea.
KEY WORDS: Pseudomonas aeruginosa proteases, Corneal ulceration, Real – time PCR.