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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.

Objective: 

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.

Conclusion: 

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 Details

Date: 01/08/2007
Time: 00:00-00:00
Session name: XXIst ISTH Congress
Subject:
Location: Oxford, UK
Presentation type:
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