1. Department of Clinical Microbiology and Infectious Diseases, Faculty of Health Sciences, School of Pathology, University of Witwatersrand, Johannesburg 2193, South Africa
2. Department of Pathology, University of Tennessee Health Science Center, Memphis, TN 38163, USA
3. Infection Control Unit, Charlotte Maxeke Johannesburg Academic Hospital, National Health Laboratory Service, Johannesburg 2193, South Africa