Emergence and spread of gentamicin-susceptible strains of methicillin-resistant Staphylococcus aureus in Belgian hospitals.
The aim of this study was to follow the evolution of the clonal distribution and antimicrobial susceptibility of clinical strains of methicillin-resistant Staphylococcus aureus (MRSA) recovered from Belgian hospitals between 1995 and 1997-1998. MRSA strains were genotyped by inter-IS256 spacer length polymorphism PCR and SmaI macrorestriction analysis. MICs of 18 antimicrobials were determined by the agar dilution method. MRSA strains from the 1997-1998 survey were further tested by vancomycin screen agar, E-test, broth microdilution methods, and population analysis. Between 1995 and 1997-1998, epidemic group A strains decreased in proportion from 73% to 44%, whereas MRSA Group B and C strains increased from 17% to 38% and from 5% to 8%. The proportion of strains susceptible to gentamicin increased between the surveys from 22% to 48%. This was associated with a higher proportion of group B and C strains in the last survey. Heterogeneous vancomycin-intermediate S. aureus (hetero-VISA) strains were found in 2% isolates from 1997 to 1998. These hetero-VISA isolates were genotypically related to the MRSA group A strains and were resistant to gentamicin. In conclusion, two emerging epidemic MRSA genotypes, susceptible to gentamicin, have spread among Belgian hospitals during the 1990s. Hetero-VISA were present at low frequency among MRSA strains belonging to a widespread endemic genotype.
Denis
Olivier
O
Laboratoire de Référence MRSA-Staphylocoques, Department of Microbiology, Hôpital Erasme, Université Libre de Bruxelles, Brussels, Belgium. odenis@ulb.ac.be
Deplano
Ariane
A
De Ryck
Raf
R
Nonhoff
Claire
C
Struelens
Marc J
MJ
D000368:Aged; D000900:Anti-Bacterial Agents / Q000494:pharmacology*; D001530:Belgium; D015169:Colony Count, Microbial; D016521:Electrophoresis, Gel, Pulsed-Field; D005260:Female; D005838:Genotype; D005839:Gentamicins / Q000494:pharmacology*; D006761:Hospitals / Q000639:trends*; D006801:Humans; D008297:Male; D016106:Methicillin Resistance / Q000235:genetics*; D008826:Microbial Sensitivity Tests; D016133:Polymerase Chain Reaction; D013211:Staphylococcus aureus / Q000187:drug effects* / Q000235:genetics / Q000302:isolation & purification
D000900:Anti-Bacterial Agents; D005839:Gentamicins