Ocular Propionibacterium Acnes: A Study On Antibiotic Susceptibility Profiling And Their Epidemiological Pattern

摘要

Purpose: To identify the antibiotic pattern of commonly used P. acnes isolates and to analyse the epidemiological patterns using Random Amplification of Polymorphic DNA (RAPD) technique. Methods: One hundred P. acnes isolates (90 % extraocular and 10% intraocular) recovered from ocular clinical specimens identified by conventional method were studied. MIC of ciprofloxacin, norfloxacin, nalidixic acid, clindamycin, penicillin G, vancomycin and metronidazole, cefotaxime and imepenum were carried out for 100 P. acnes ophthalmic isolates by spot inoculation technique. Results: Six distinct RAPD patterns were observed among these isolates of which the 4th pattern was the most predominant one (41%), which was isolated mostly from conjunctival swabs. Of the 100 clinical anaerobic P. acnes isolates, highest resistant antibiotic pattern was seen among conjunctival swabs isolates for metronidazole (100%). Following it was the clindamycin (79%) and penicillin G (64%). Conclusion: This study has proven that RAPD is a reproducible, powerful technique for P. acnes genomic typing and may definitely play a vital role in identifying epidemiology of P. acnes. There was no correlation between the antibiotic pattern and the corresponding RAPD fingerprinting results in our study. Resistance to Vancomycin, the most commonly used intravitreal antibiotic is emerging among P. acnes is being reported for the first time. Studies at molecular level with vancomycin resistant isolates will help to understand the mechanism of resistance. Introduction Propionibacterium acnes is a major inhabitant of the adult human skin and conjuctival sac.1, 2 Currently, routine diagnostic practices underestimate the clinical importance of this anaerobic organism due to inefficient detection and isolation procedures, along with the traditionally held view that, the organism has low virulence; its presence in clinical samples reflects contamination with normal flora. 3 However the organism is gaining clinical importance. P. acnes is responsible for post surgical delayed endophthalmitis4, lacrimal sac and/or nasolacrimal duct obstruction5, infections of prosthetic implants6, intraocular lenses (IOLs)7, keratitis.8 It is not known whether P. acnes that reside as normal flora and that isolated from disease sites have any genetic variations. Very few studies have been published on the epidemiology of P. acnes isolates. Random amplification of polymorphic DNA (RAPD) technique, a modification of Polymerase Chain Reaction (PCR), in which a single primer is able to anneal and prime at multiple locations in a genome, can be of great epidemiological value.9 The success of this method is due to the fact that no prior information about the target sequence is needed. These primers detect polymorphisms in the absence of variations and may work as genetic markers that are used in epidemiologic studies.Increasing prevalence of antimicrobial resistance to P. acnes has been documented since last 20 years.10 To treat such infections adequately, empirical therapy usually relies on the use of Beta-lactams (penicillin’s, third-generation cephalosporins) combined with metronidazole and/or vancomycin. Depending on the circumstances, other antibiotics such as clindamycin or fluoroquinolones may also be used.11 P. acnes is the most predominant anaerobe isolated from ocular specimens in our hospital set up. Since there are very few reports for understanding the epidemiological pattern of P. acnes available in literature and their correlation with the antibiotic pattern of P. acnes, the current study was undertaken. This is the first study carried out in India with the P. acnes isolates recovered from ocular specimens. Materials And Methods Bacterial strainsOne hundred P. acnes isolates recovered from ocular clinical specimens (conjunctival swab - 65, conjunctival scraping – 1, corneal scraping – 13, lid abscess – 3, iris tissue - 2, corneal button-5, vitreous chamber tap – 1, anterior chamber tap - 2,