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Year : 2011  |  Volume : 29  |  Issue : 3  |  Page : 312-313

High oxacillin, vancomycin and fluoroquinolone resistance amongst biofilm forming Staphylococcus aureus isolates from ulcerative keratitis infections

Department of Microbiology, CSJM University, Kanpur, Uttar Pradesh, India

Date of Submission14-Mar-2011
Date of Acceptance13-Jun-2011
Date of Web Publication17-Aug-2011

Correspondence Address:
S D Kaistha
Department of Microbiology, CSJM University, Kanpur, Uttar Pradesh
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Source of Support: None, Conflict of Interest: None

DOI: 10.4103/0255-0857.83921

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How to cite this article:
Singh S, Katiyar R, Kaistha S D. High oxacillin, vancomycin and fluoroquinolone resistance amongst biofilm forming Staphylococcus aureus isolates from ulcerative keratitis infections. Indian J Med Microbiol 2011;29:312-3

How to cite this URL:
Singh S, Katiyar R, Kaistha S D. High oxacillin, vancomycin and fluoroquinolone resistance amongst biofilm forming Staphylococcus aureus isolates from ulcerative keratitis infections. Indian J Med Microbiol [serial online] 2011 [cited 2021 Jan 26];29:312-3. Available from:

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.
Table 1: Antibiotic resistance and biofi lm formation in ulcerative keratitis isolates

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 ~ Acknowledgement Top

Financial support from DST and DAE, Government of India, is gratefully acknowledged.

 ~ References Top

1.Behlau I, Gilmore MS. Microbial Biofilms in Ophthalmology and Infectious Disease. Arch Ophthalmol 2008;126:1572-81.   Back to cited text no. 1
2.Schaefer F, Bruttin O, Zografos L, Guex-Crosier Y. Bacterial keratitis: A prospective clinical and microbiological study. Br J Ophthalmol 2001;85:842-7.  Back to cited text no. 2
3.Clinical Laboratory Standards Institute. Performance Standards for Antimicrobial Disc Susceptibility Tests, CLSI. 2008;28:1  Back to cited text no. 3
4.O'Toole GA, Kotler R. Initiation of biofilm formation in Pseudomonas fluorescens WCS365 proceed via multiple, convergent signaling pathways: A genetic analysis. Mol Microbiol 1998;28:449-61.  Back to cited text no. 4
5.Holt JG, Krieg NR, Sneath PH, Staley JT, Williams ST. Staphylococcus spp. In: Bergey's Manual of Determinative Bacteriology, 9th Ed. Baltimore, Maryland: Williams and Wilkins; 1994. p. 544-51.  Back to cited text no. 5


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Minh Giao Long Bui,John D. Turnidge,Stephen P. Kidd
Microbes and Infection. 2014;
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