Acta Tropica 80 (2001) 155–161 The spread of a mupirocin-resistant/methicillin-resistant Staphylococcus aureus clone in Kuwait hospitals E.E. Udo *, L.E. Jacob, B. Mathew Department of Microbiology, Faculty of Medicine, Kuwait Uniersity, PO Box 24923, Safat 13110, Kuwait Received 29 May 2000; received in revised form 23 March 2001; accepted 30 April 2001 Abstract High-level mupirocin- and methicillin-resistant Staphylococcus aureus (MRSA) isolated from five hospitals in Kuwait were studied by pulsed-field gel electrophoresis (PFGE) to determine their relatedness to one another and to high-level mupirocin-resistant MRSA isolated previously in a Burns Unit. The genetic location of mupirocin resistance determinant was also determined. All of the isolates were resistant to gentamicin, kanamycin, streptomycin, tetracycline and cadmium, and contained plasmids of 38, 26 and 2.8 kb. Two isolates contained additional 4.4-kb plasmids. Transfer experiments demonstrated that the 38-kb plasmid encoded high-level mupirocin resistance and the 4.4-kb plasmid encoded chloramphenicol resistance. PFGE typing of representative isolates from the five hospitals demonstrated that the majority of them had identical or closely related pulsed-field patterns suggesting that they had a common origin. However, they differed from high-level mupirocin-resistant MRSA isolated previously in the Burns Unit in their resistance and pulsed-field patterns. Whereas the majority of the previous isolates were susceptible to ciprofloxacin and resistant to trimethoprim and chloramphenicol, the majority of the current isolates were susceptible to trimethoprim and chloramphenicol, and resistant to ciprofloxacin. Only one of the current isolates had identical pulsed-field pattern to the majority of isolates obtained previously in the Burns Unit. The results suggested that a previously dominant clone of high-level mupirocin-resistant MRSA has been replaced in the Burns Unit by a new clone, which also spread in four other hospitals. © 2001 Elsevier Science B.V. All rights reserved. Keywords: Mupirocin resistance; Pulsed-field gel electrophoresis; Methicillin-resistant Staphylococcus aureus ; Conjugative plasmid www.parasitology-online.com 1. Introduction Mupirocin (Bactroban) is a topical narrow spectrum antibiotic that is active against Gram- positive pathogens especially Staphylococcus au - reus including methicillin-resistant S. aureus (MRSA). Mupirocin has been used successfully to eradicate colonization of MRSA in patients as well as in hospital workers (Hill et al., 1988; Rode et al., 1989; Denning and Haiduven-Griffiths, 1988; Strock et al., 1990; Cookson, 1998; Bastos et al., 1999). Two types of mupirocin resistance have been observed and classified into low- and high-level resistance. Low-level resistance is char- acterized by minimum inhibitory concentrations (MICs) of 8–256 mg/l and high-level resistance is characterized by higher MIC values ( 512 mg/l). * Corresponding author. Fax: +965-533-2719. E-mail address: edet@hsc.kuniv.edu.kw (E.E. Udo). 0001-706X/01/$ - see front matter © 2001 Elsevier Science B.V. All rights reserved. PII:S0001-706X(01)00171-1