Access Type

Open Access Thesis

Date of Award

January 2014

Degree Type

Thesis

Degree Name

M.S.

Department

Pharmaceutical Sciences

First Advisor

Emily T. Martin

Abstract

COMPARATIVE STUDY OF THE PREVALENCE OF PSK41 IN HETEROGENOUS VANCOMYCIN-INTERMEDIATE STAPHYLOCOCCUS AUREUS ISOLATES AGAINST NON- HETEROGENOUS VANCOMYCIN-INTERMEDIATE STAPHYLOCOCCUS AUREUS ISOLATES AND THE PREVALENCE BY PATIENT SEVERITY

by

POORVA DIVEKAR

December 2014

Advisor: Dr. Emily T. Martin

Major: Pharmaceutical Sciences

Degree: Master of Science

Earlier studies have reported that pSK41 plays an important role in the transfer of vancomycin resistance from Vancomycin-resistant Enterococci (VRE) to S. aureus. This transfer leads to the development of Vancomycin-resistant S. aureus (VRSA). Thirteen VRSA cases have been reported in the United States since 2002. To determine and compare the prevalence of pSK41 in hVISA isolates against non-hVISA isolates and the comparison of the prevalence of pSK41 by patient severity and spa type.

Samples were collected from patients presenting for the care of blood stream infection. Collection was done in Michigan, New York, Pennsylvania and Ohio. DNA was extracted from all the samples and checked for the presence of pSK41 using pSK41 marker genes. After confirming the final number of pSK41-positive isolates, the prevalence of pSK41 was compared between hVISA isolates and non-hVISA isolates. Secondly, the prevalence of pSK41 was compared by patient severity. Lastly, the distribution of pSK41 isolates among various spa types was studied by performing spa typing.

Out of 144 samples, 10 (6.9%) samples were found to contain pSK41. Eight pSK41-positive isolates were hVISA and two were non-hVISA. The pSK41 plasmid was found to be a low-prevalence plasmid in both hVISA, and non-hVISA isolates. There was no significant association between the presence of pSK41 and patient severity. Also, the presence was pSK41 was observed in many spa types.

The pSK41 plasmid is found at a low prevalence in hVISA isolates, and non-hVISA isolates recovered from patients with bloodstream infection. Even though a low prevalence of this plasmid was observed, 6.9% of the total isolates in the study carried pSK41. This number can't be ignored as it might indicate future development of VRSA. Secondly, pSK41 can be found in patients that are at high and low clinical severity. However, more work is needed to produce robust data regarding this association. Lastly, we can also conclude that the presence of pSK41 can be found in many spa types. The pSK41 plasmid does not appear to be associated with any particular spa type.

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