Investigation of cell wall thickness and coagulation activity in vancomycin resistance S. aureus

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Investigation of cell wall thickness and coagulation activity in vancomycin resistance S. aureus


Author: Chong, Yu-cheung Eugene
Title: Investigation of cell wall thickness and coagulation activity in vancomycin resistance S. aureus
Degree: M.Sc.
Year: 2012
Subject: Vancomycin resistance.
Staphylococcus aureus.
Hong Kong Polytechnic University -- Dissertations
Department: Dept. of Health Technology and Informatics
Pages: 91 leaves : ill. (some col.) ; 30 cm.
Language: English
Abstract: Vancomycin intermediate Staphylococcus aureus (VISA) and heterogeneous vancomycin intermediate Staphylococcus aureus (hVISA) are increasingly reported and caused glycopeptide treatment failure. Cell wall thickening had been found to be a common feature of the VISA/hVISA phenotype. However, the underlying genetic resistant mechanism remains undetermined. Besides, reduced coagulation activity had also been found in some VISA strains. The objective of this study is to find out the relationship of cell wall thickness and coagulation activity to vancomycin resistant. Six S. aureus strains had been induced to achieve various vancomycin resistant levels. Cell wall thickness of the samples was directly measured via electron microscopy, while coagulation activity was determined by traditional tube coagulation test. The cell wall thickness and coagulation time were then correlated with vancomycin MIC. Laboratory findings showed that cell wall thickness of 4/6 S. aureus strains were positively correlated with vancomycin MIC. Moreover, a minimal increment in one third of cell wall volume had been found in resistant stain with MIC>2ug/ml. Apart from cell wall thickening, coagulation time was also correlated with vancomycin MIC. At least 30% increment of coagulation time was found in vancomycin non-susceptible strains. In conclusion, increased cell wall thickness seems to have contribution for S. aureus to gain vancomycin resistance. The serial isogenic sample strains with different vancomycin MIC in this study can provide materials for further investigation of the underlying genetic resistant pathway. Also, increased vancomycin MIC resulted in prolonged coagulation time. Hence, tube coagulation test may become a novel phenotypic method on screening S. aureus with reduced vancomycin resistance.

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