Genotypic characterisation of methicillin- resistant : Staphylococcus aureus

June, Junnie (2008) Genotypic characterisation of methicillin- resistant : Staphylococcus aureus. Masters thesis, University of Malaya.

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GENOTYPIC CHARACTERISATION OF METHICILLIN RESISTANT Staphylococcus aureus Abstract.pdf

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Official URL: http://dspace.fsktm.um.edu.my/handle/1812/496

Abstract

Background: Methicillin-Resistant Staphylococcus aureus (MRSA) is a serious cause of nosocomial infection in Malaysia. Sixty-six MRSA isolates recovered from patients from Universiti Malaya Medical Centre, KL over a 4-year period (2003-2007) were studied to determine the clonal relationship of sporadic (year 2004 and 2007) and outbreak and outbreak elated (year 2003) isolates and sulfamethoxazole-trimethroprim- tetracyclineerythromycin (SXT-TE-E) sensitive isolates Methods: Polymerase chain reaction was carried out on the isolates to detect the mecA gene which is primarily responsible for the methicillin resistance in Staphylococcus aureus. Pulsed-field gel electrophoresis (PFGE) of SmaI-digested chromosomal DNA and antimicrobial susceptibility tests were carried out. Results: Antimicrobial susceptibility tests generated 34 antibiograms with 100% of isolates being susceptible to vancomycin. Majority of the isolates showed susceptibility towards fusidic acid (89%), clindamycin (81%), vancomycin (100%) and rifampicin (89%), indicating that these antibiotics will be/are effective in treating MRSA infections. A dendrogram based on the clustering of the antibiograms showed two major clusters (AM1 and AM2). Most of the sporadic isolates and all SXT-TE-E susceptible isolates were clustered in AM 2. The majority of outbreak isolates were clustered in AM1. Fiftyeight isolates (88%) were mecA positive while 8 (12%) were mecA negative. These 8 isolates however showed phenotypic resistance to methicillin. Genotyping by PFGE showed 55 profiles, consisting of 13-17 bands. Among the 25 outbreak and outbreak related isolates, 22 PFGE profiles were obtained, suggesting that the outbreak originated from multiple sources or was a multiple subtype outbreak. Majority (93%) of isolates from year 2007 were clustered together. The diversed PFGE profiles obtained from the sporadic isolates indicated that MRSA were genetically diverse (F=0.31-1.00). Isolates susceptible to amikacin, gentamicin, erythromycin, sulfamethoxazole-trimethoprim (SXT) and tetracycline gave distinctly different PFGE profiles, and were clustered together. Chi-square or Fishers exact test showed that there was a significant difference (p<0.05) in antimicrobial resistance between sporadic and outbreak and related isolates for SXT, tetracycline, netilmicin and clindamycin. Conclusion: The genetic relatedness of outbreak, sporadic and SXT-TE-E susceptible isolates were 69-100%, 31-100% and 15-100% respectively, indicating that sporadic isolates were genetically more diversed than outbreak isolates. The outbreak was caused by multiple subtypes of MRSA, and not a single subtype. The reemergence of SXT-TE-E susceptible isolates may denote presence of MRSA in the community where such antibiotic exposure is minimal. There were no vancomycin resistant isolates.

Item Type: Thesis (Masters)
Subjects: Q Science > Q Science (General)
Depositing User: MS SITI NUR ATIKAH MOHAMAD RUSDI
Date Deposited: 31 Jul 2013 03:13
Last Modified: 31 Jul 2013 03:13
URI: http://repository.um.edu.my/id/eprint/1132

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