Abstract
BackgroundInvestigation of two independent outbreaks of post cataract surgery endophthalmitis identified the reservoir of epidemic strains of P. aeruginosa.MethodsPatient isolates cultured from vitreous fluid of all the nine cases and from the peripheral devices of phacoemulsification machine were subjected to high-resolution Fluorescent Amplified Fragment Length Polymorphism (FAFLP) analysis.ResultsFAFLP based genotyping of the isolates confirmed nosocomial transmission. Although biochemical characterization and antibiotic susceptibility profiles grouped all the isolates together, FAFLP based genotyping revealed that, all the outbreak isolates were derived from 2 different strains, with independent origins. One group of isolates was traced to phacoprobe and the second one to the internal tubing system of the phacoemulsification machine used in cataract surgery. In silico analysis indicated possible evolution in both the clusters of P. aeruginosa isolates due to genetic polymorphisms. The polymorphisms were mapped to gene products (cell envelope, outer membrane proteins) possibly having significant role in pathogenesis.ConclusionThe present study is probably the first one to apply FAFLP typing successfully to investigate outbreaks of postoperative endophthalmitis (POE) in an ophthalmic setting, which was able to identify the source, and helped to make rational decisions on sterilization procedures that halted more cases of infection in these hospitals.
Highlights
Investigation of two independent outbreaks of post cataract surgery endophthalmitis identified the reservoir of epidemic strains of P. aeruginosa
We report the evaluation of two outbreaks of postoperative endophthalmitis (POE) that were investigated for detection of the source of infection using fluorescent amplified fragment length polymorphism (FAFLP)
At the time of first outbreak, on June 8, 2003, the Infection Control Committee (ICC) at the LV Prasad Eye Institute (LVPEI), Hyderabad, India was alerted about a possibility of outbreak of POE in 4 of 14 patients undergoing cataract surgery
Summary
Investigation of two independent outbreaks of post cataract surgery endophthalmitis identified the reservoir of epidemic strains of P. aeruginosa. The incidence has reduced to 0.06%, largely owing to the advances made in sterilization procedures and understanding of the modes of post surgical infections [1]. Tools of source detection in an outbreak of postoperative endophthalmitis (POE) have moved much beyond culture of suspected samples and antibiotic sensitivity testing of the underlying organisms. We report the evaluation of two outbreaks of POE that were investigated for detection of the source of infection using fluorescent amplified fragment length polymorphism (FAFLP). Apart from demonstrating the utility of a FAFLP technique in outbreak investigations, this report seeks to emphasize the threat of POE resulting from break in sterility during phacoemulsification procedures, even under best of circumstances
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