Increased Vancomycin Minimum Inhibitory Concentrations of Methicillin-Resistant Staphylococcus aureus Nosocomial Isolates in Southwestern Saudi Arabia

Ahmed Morad Asaad^1, and Mohamed Ansar Qureshi¹

¹Department of Microbiology, College of Medicine, Najran University, Najran, Saudi Arabia

Cite this paper:
Ahmed Morad Asaad and Mohamed Ansar Qureshi. Increased Vancomycin Minimum Inhibitory Concentrations of Methicillin-Resistant Staphylococcus aureus Nosocomial Isolates in Southwestern Saudi Arabia. American Journal of Epidemiology and Infectious Disease. 2013; 1(4):59-62. doi: 10.12691/ajeid-1-4-6

Abstract

This study aimed to determine the distribution of vancomycin (VAN) MIC values and antimicrobial resistance patterns of MRSA nosocomial isolates from a Saudi tertiary care hospital and evaluate the presenting clinical and demographic features of different infections caused by these isolates. A total of 104 non-duplicating MRSA nosocomial strains were isolated. VAN MICs were determined by standard Etest and the Etest macromethod (MET). Among all isolates, 7.7% had a MIC = 2 µg/ml, 70.2% had a MIC = 1 µg/ml and 22.1% had a MIC = 0.5 µg/ml. No heterogeneous VAN-intermediate S. aureus (hVISA) were detected. Patients infected with high VAN MRSA nosocomial isolates were of significantly older age (p = 0.035), presented more often with bacteraemia (p = < 0.0001) and had longer hospital stays (p = < 0.0001). The presence of high VAN MICs of some MRSA isolates in our hospital is worrying and a cause for concern due to the possibility of the potential failure of treatment of these isolates. Moreover, accurate MIC testing using MET simultaneously or as a supplement to automated systems (i.e. Vitek) is important.

Keywords:
MRSA vancomycin MIC Etest macromethod nosocomial

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