Emergence of Staphylococcus aureus with reduced susceptibility to vancomycin in Asia

Abstract

Staphylococcus aureus is one of the most important bacterial pathogens causing various infections from mild skin and skin structure infections to potentially fatal systemic illnesses such as endocarditis and sepsis. S. aureus has developed antimicrobial resistance to various antibiotics since the introduction of modern chemotherapeutic agents in the 1940s. Particularly, the emergence and dissemination of methicillin-resistant S. aureus (MRSA) has become a global concern since the first report in 1961. Nowadays, MRSA is the most common nosocomial pathogen in many hospitals. MRSA is also emerging in the community in many countries in recent years. The high rate of MRSA infections has led to an increasing use of vancomycin in clinical practice during the past two decades. Since the early 1990s, there have been some concern about the emergence of S. aureus with reduced susceptibility to vancomycin, as vancomycin-resistant enterococci (VRE) has rapidly emerged in many countries. Furthermore, conjugative transfer of the vanA gene from VRE to S. aureus was demonstrated in the laboratory (Noble et al., 1992). This theoretical concern became a reality in 1996 when the first strain of S. aureus with intermediate resistance to vancomycin was found from a 4-month-old infant patient who underwent open heart surgery in Japan (Hiramatsu et al., 1997). Subsequently, infections with vancomycin-intermediate S. aureus (VISA) strains have been reported in patients from the United States, Europe, and Asia. Growing concern of vancomycin resistance in S. aureus was deepened by the emergence of high-level vancomycin-resistant S. aureus (VRSA) strains from the United States since 2002 (CDC, 2002a, b, 2004; Tenover and McDonald, 2005). The third type of reduced susceptibility to vancomycin in S. aureus is heterogenous vancomycin-intermediate resistance (hVISA), which had been first reported by Hiramatsu et al. in 1997. These various types of reduced susceptibility to vancomycin could lead to clinical failures of vancomycin treatment. This review will summarize the current epidemiology of S. aureus with reduced susceptibility to vancomycin, especially in Asian countries, as well as the resistance mechanism, clinical implications, and infection control measures. © 2008 Springer US.