Genetic analysis of high- and low-level Mupirocin-resistant MRSA isolated in Kuwaiti hospitals
Abstract number: 1733_1077
Noronha C., Udo E., Al-Sweih N., Mathew B.
Background: Mupirocin resistance in Staphylococci is expressed either as high-level (MIC >512 mg/L) or low-level (MIC 8256 mg/L) resistance. The prevalence of high-level mupirocin resistance has been increasing in MRSA isolated in Kuwait in recent years. This necessitated monitoring MRSA isolated in Kuwaiti hospitals at regular intervals for changes in their mupirocin resistance patterns.
Objective: To monitor the prevalence of mupirocin resistance in MRSA isolated in Kuwait hospitals and determine its genetic location.
Methods: MRSA isolated from six hospitals between January 2000 and December 2005, were tested for susceptibility to antibacterial agents by disk diffusion. Mupirocin MICs was determined with Etest strips. The presence of mupA genes that encodes high-level mupirocin resistance (mupH) was investigated by PCR. Pulsed-field gel electrophoresis (PFGE) was used to study their genetic relatedness. Curing and transfer experiments were used to determine the plasmid or chromosomal location of mupirocin resistance.
Results: A total of 4,982 MRSA isolates were investigated. The prevalence of mupH declined from 22% in 2000 to 1.8% in 2005. In contrast, the prevalence of low-level resistance increased from 3.6% in 2000 to 90.8% in 2004 before decreasing to 65.7% in 2005. Transfer experiments revealed that mupH was located on a 38-kb conjugative plasmid while the low-level resistance was chromosomal. The mupA gene was detected only in the mupH isolates. PFGE analysis revealed that the low-level mupirocin-resistant isolates belonged to six different clones. Two of these clones, constituting 87.6% of the isolates, were detected in all six hospitals and were related to isolates that expressed high-level resistance.
Conclusions: This study revealed a dramatic shift in the prevalence of high- and low-level mupirocin resistance among Kuwait MRSA isolates. The relatedness of some low-level mupirocin-resistant isolates to those expressing high-level resistance suggests that these isolates have arisen by the loss of the 38-kb mupA plasmid. The study also highlights the value of regular surveillance in detecting changes in resistance and clonal patterns of MRSA isolates in healthcare environments
|Session name:||European Society of Clinical Microbiology and Infectious Diseases|
|Location:||ICC, Munich, Germany|
|Back to top|