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Indian Journal of Medical Microbiology, Vol. 29, No. 3, July-September, 2011, pp. 312-313 Correspondence High oxacillin, vancomycin and fluoroquinolone resistance amongst biofilm forming Staphylococcus aureus isolates from ulcerative keratitis infections S Singh, R Katiyar, SD Kaistha Department of Microbiology, CSJM University, Kanpur, Uttar Pradesh, India Date of Submission: 14-Mar-2011 Code Number: mb11075 PMID: 21860118 DOI: 10.4103/0255-0857.83921 Dear Editor, Increasing antibiotic resistance in Staphylococcus aureus, a leading cause of ulcerative keratitis in the developing world, is of great concern. [1] Its ability to form biofilms on ocular surfaces enhances antibiotic resistance through several mechanisms. [2] Understanding of the resistance patterns amongst clinical isolates is a prerequisite for devising better treatment strategies and measures to mitigate emerging antibiotic resistance. A total of 42 independent Staphylococcus isolates from cases of ulcerative keratitis around Kanpur were evaluated for antibiotic resistance using antibiotic discs (Hi Media, Mumbai, India) as per CLSI guidelines. [3] The ability of the isolates to form biofilms was characterised using the static microtitre plate assay. [4] Microbiological and biochemical characterisation of the isolates was performed as per Bergey′s determinative bacteriology. [5] Of these, 75% (30/40) isolates were S. aureus and 23.8% (10/42) were coagulase-negative Staphylococcus epidermis and 4.7% (2/42) were Micrococcus sp. 85.72% (36/42) of the isolates were found to be high biofilm formers and 83% (35/42) were biofilm forming, multiple drug resistant (resistant to three or more classes of antibiotics). Pearson′s correlation between biofilm formation and antibiotic resistance was found for S. aureus isolates of 0.6. [Table - 1] details the percentage resistance of total and biofilm forming isolates to the various antibiotics. Of the total isolates, 83.3% (35/42) were found to be oxacillin resistant, 57.14% (24/42) were ceftriazone resistant, 54.7% (23/42) were vancomycin resistant and 47.6% (20/42) were tobramycin resistant. It is alarming to note the high percentage of resistance to a number of antibiotics preferentially used for treatment of ocular infections, such as fluoroquinolones. Frequent usage of moxifloxacin in the treatment of ocular infections may be the cause of 76.2% (32/42) resistance to the fourth-generation fluoroquinolone moxifloxacin over ofloxacin (30.9%; 13/42) and levofloxacin (40.4%; 17/42). Low resistance is reported to gentamicin (26.1%; 11/42) which is less frequently used in ocular infections due to problems of poor ocular penetration. Low resistance to extended b lactamase antibiotic imipenem (4.7%; 2/42) is likely a consequence of drug usage only in emergency situations. Judicious use of emerging drugs is advisable as high antibiotic resistance is being measured in biofilm forming, methicillin-resistant S. aureus (MRSA) ocular infections to the most commonly used ophthalmic drugs. Acknowledgement Financial support from DST and DAE, Government of India, is gratefully acknowledged. References
Copyright 2011 - Indian Journal of Medical Microbiology The following images related to this document are available:Photo images[mb11075t1.jpg] |
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