Molecular fingerprinting of mupirocin-resistant methicillin-resistant Staphylococcus aureus from a burn unit.
OBJECTIVE
To characterize mupirocin-resistant methicillin-resistant Staphylococcus aureus (MRSA) isolated from patients in a burn unit by pulsed-field gel electrophoresis and plasmid contents.


METHODS
A total of 53 methicillin-resistant S. aureus, consisting of 48 mupirocin-resistant and 5 mupirocin-susceptible MRSA were compared by plasmid content and pulsed-field gel electrophoresis of Sma I digested genomic DNA.


RESULTS
Of the 48 mupirocin-resistant isolates, 39 expressed high-level, and 9 expressed low-level mupirocin resistance. Plasmids were detected in all of the 53 isolates; however, only the high-level mupirocin-resistant isolates contained a 38 kb-conjugative plasmid that encoded high-level mupirocin resistance. Pulsed-field gel electrophoresis divided the isolates into four patterns designated types I to IV. Forty-three isolates consisting of 34 high-level, 5 low-level mupirocin-resistant and 4 mupirocin-susceptible isolates defined the type-I pattern. Eight isolates, five high-level and three low-level mupirocin-resistant isolates had the type-II pulsed-field pattern. The type-III and type-IV pulsed-field patterns consisted of a single isolate each. The type-I and type-II pulsed-field patterns were related and only differed by four Sma I bands.


CONCLUSIONS
Results of typing the mupirocin-resistant MRSA from the burn unit with pulsed-field gel electrophoresis indicated that closely related MRSA clones previously circulating in the unit had acquired a high-level mupirocin-resistant plasmid, and spread aided by mupirocin use.
Udo
E E
EE
Department of Microbiology, Faculty of Medicine, Kuwait University, Safat, Kuwait. EDET@hsc.kuniv.edu.kw
Farook
V S
VS
Mokadas
E M
EM
Jacob
L E
LE
Sanyal
S C
SC
D000900:Anti-Bacterial Agents / Q000494:pharmacology; D002053:Burn Units; D016172:DNA Fingerprinting; D004352:Drug Resistance, Microbial; D016521:Electrophoresis, Gel, Pulsed-Field; D005798:Genes, Bacterial / Q000235:genetics; D006801:Humans; D016106:Methicillin Resistance; D016712:Mupirocin / Q000494:pharmacology; D010957:Plasmids / Q000032:analysis / Q000235:genetics; D013211:Staphylococcus aureus / Q000145:classification / Q000187:drug effects / Q000235:genetics*
D000900:Anti-Bacterial Agents; D016712:Mupirocin