Molecular characterisation of methicillin-resistant Staphylococcus aureus (MRSA) from keratitis patients: a microbiological analysis

• Published in: British journal of ophthalmology Vol. 94; no. 8; pp. 994 - 998
• Main Authors: Khan, Mohd A, Ahmad, S, Banu, N
• Format: Journal Article
• Language: English
• Published: BMA House, Tavistock Square, London, WC1H 9JR BMJ Publishing Group Ltd 01.08.2010; BMJ Publishing Group; BMJ Publishing Group LTD
• Subjects: Adolescent; Adult; Antibiotics; Bacterial Typing Techniques - methods; biochemistry; Biological and medical sciences; Cloning; Cornea - microbiology; Deoxyribonucleic acid; Diseases of cornea, anterior segment and sclera; DNA; DNA, Bacterial - isolation & purification; Drug Resistance, Multiple, Bacterial; Electrophoresis, Gel, Pulsed-Field; Epidemiology; Eye Infections, Bacterial - microbiology; Female; genetics; Humans; infection; Keratitis - microbiology; keratitis PFGE; Laboratories; Male; Medical sciences; Methicillin-Resistant Staphylococcus aureus - classification; Methicillin-Resistant Staphylococcus aureus - genetics; Methicillin-Resistant Staphylococcus aureus - isolation & purification; Microbial Sensitivity Tests - methods; microbiology; Middle Aged; Miscellaneous; MRSA; Nosocomial infections; Ophthalmology; Pain; Polymerase Chain Reaction - methods; SCCmec type II cassette; Staphylococcal Infections - microbiology; Staphylococcus infections; Surgery; Young Adult; India; Human; Keratitis; β-Lactams; Keratopathy; Meticillin; Penicillin derivatives; Eye disease; Antibiotic; Analysis; Bacteria; Micrococcales; Micrococcaceae; Ophthalmology; Antibacterial agent; Anterior segment disease; Staphylococcus aureus
• ISSN: 0007-1161; 1468-2079; 1468-2079
• DOI: 10.1136/bjo.2009.161893

BackgroundIn order to diagnose and characterise a major corneal infection, ‘keratitis,’ which can lead to blindness, molecular studies were conducted to assess the prevalence of methicillin-resistant Staphylococcus aureus (MRSA) strains in patients suffering from keratitisMethodsThe selected culture positive for strains of S aureus were subjected to 18 antimicrobial drugs for their sensitivity behaviour, and the minimum inhibitory concentration (MIC) of oxacillin was determined by the microdilution method as recommended by the National Committee for Clinical Laboratory Standards. Further, S strains were characterised using molecular tools.ResultsAmong the 202 cases included in the present study, 64 (31.2%) cases were found to be S aureus-positive, of which only six strains were MRSA. The highest resistance was observed for penicillin (65.6%) which was followed by a significant number of bacterial isolates showing resistance to methicillin (9.3%), while all organisms were susceptible to vancomycin. The minimum inhibitory concentrations of oxacillin for MRSA strains ranged between 16 and 128 μg/ml. A multiplex PCR assay for Staphylococcal Cassette Chromosome mec complex (SCCmec) of MRSA strains (N=6) showed that five MRSA strains had a Type III cassette, and one had a Type II cassette. The pulsed field gel electrophoresis of three MRSA strains showed closely related band patterns.ConclusionThe close relatedness among bacterial strains as observed by employing different typing techniques suggests that the clonal characteristics of multiresistant MRSA isolates could be deciphered. The presence of Type II SCCmec in keratitis subjects is probably the first report from India, as it has not been reported earlier.