Genetic relatedness between sporadic and epidemic methicillin-resistant Staphylococcus aureus in Belgian hospitals
Abstract number: p517
Hallin M., De Mendonca R., Denis O., Deplano A., De Ryck R., Rottiers S., Struelens M.J.
The objective was to compare the genetic backgrounds of sporadic MRSA isolates with those of successful epidemic MRSA clones.
Material and methods:
30 strain representative of the nine most frequent Belgian epidemic clones and 20 sporadic strains were selected from the ULB-Staphylococcus Reference Laboratory collection (MRSA isolates recovered from patients hospitalised in Belgian acute-care hospitals from 1992 to 2003) based on their pulsed field gel electrophoresis (PFGE) type after SmaI macrorestriction. A PFGE pattern was considered as sporadic if there was a difference of >6 DNA fragment with any other PFGE pattern in the entire database (~2500 strains). Strains were further characterised by Multilocus Sequence Typing (MLST), spa typing and SCCmec typing.
Results (See table):
The 20 sporadic isolates were classified by MLST in 9 Sequence Types (ST) all but one belonging to the 5 same Clonal Complexes as epidemic clones (CC5, 8, 45, 22 and 30). SCCmec type distribution among sporadic strains was as follow: type I: 9 isolates, type IV: 7, type III: 2, type II and V: 1 isolate each. SCCmec type IV was associated with the greatest number of different STs (5). Based on MLST combined with SCCmec typing, 12 clonal types were identified, only 5 of which were identical to those of major Belgian epidemic clones. The 20 sporadic isolates belonged to 16 spa types of which up to 6 were shared with epidemic strains.
The majority of sporadic and epidemic MRSA strains identified over a 11-year period in Belgian hospitals share common genetic background. Although, only half of sporadic MRSA strains belong to the same ST-SCCmec type as epidemic strains, suggesting that resistance cassette type and other epigenetic markers are involved in conferring the epidemic behaviour of MRSA.
|Session name:||XXIst ISTH Congress|
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