Staphylococcus aureus with reduced glycopeptide susceptibility in Liverpool, UK

Journal of Antimicrobial and Chemotherapy April 2010 V.65 N.4 P.721-724

Andrew Kirby1,*, Robert Graham2, Nicola J. Williams3, Mandy Wootton4, Caroline M. Broughton1, Mishaal Alanazi1, James Anson2, Timothy J. Neal2 and Christopher M. Parry1

1School of Infection and Host Defence,DuncanBuilding,UniversityofLiverpool,Daulby Street,LiverpoolL69 3GA,UK

2Department of Medical Microbiology, Royal Liverpool andBroadgreenUniversityHospitalTrust,Prescot Street,LiverpoolL7 8XP,UK

3School of Veterinary Science, National Centre for Zoonoses Research, University of Liverpool, Leahurst, Chester High Road, Neston, Wirral CH64 7TE, UK

4Specialist Antimicrobial Chemotherapy Unit, NPHSCardiff,UniversityHospitalofWales,HeathPark,CardiffCF14 4XW,UK

*Corresponding author. Tel: +44-151-706-4396/4410; Fax: +44-151-706-5805; E-mail: amk@liv.ac.uk

Abstract

Objectives

To investigate if colonization with heterogeneous glycopeptide-intermediate Staphylococcus aureus (hGISA) is associated with hGISA bacteraemia.

Methods

Isolates of methicillin-resistant S. aureus (MRSA) from blood cultures and from swabs to detect MRSA colonization were screened for reduced susceptibility to glycopeptides by an agar incorporation method. Isolates detected by this screen were tested for glycopeptide resistance by MacroEtest, standard MIC Etest methods and population analysis profile–AUC (PAP–AUC) analysis. S. aureus isolates with and without reduced glycopeptide susceptibility were characterized by PFGE and spa typing.

Results

MRSA isolates with reduced susceptibility to glycopeptides, as identified by the MacroEtest method, were detected in the colonization screens of 86 of 2550 MRSA-positive patients. The isolates were confirmed by Etest MIC and PAP–AUC analysis as hGISA. A total of 82/86 of the hGISA colonizing isolates were EMRSA-16 by PFGE; the remainder were EMRSA-15. Bacteraemia with hGISA was identified in five patients during the study period; two isolates were EMRSA-16 and three were EMRSA-15. hGISA colonization could not be linked to hGISA bacteraemia and hGISA bacteraemia could not be linked to hGISA colonization. Four of the five hGISA bacteraemias developed following teicoplanin therapy for a central venous catheter-associated MRSA bacteraemia.

Conclusions

Laboratory strategies to reduce morbidity associated with hGISA should focus on testing for hGISA in bacteraemic (rather than colonizing) MRSA isolates in patients with recurrent S. aureus bacteraemia following glycopeptide exposure.

abstract

http://jac.oxfordjournals.org/content/65/4/721.abstract

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