Reemergence of gentamicin-susceptible strains of methicillin-resistant Staphylococcus aureus in France: a phylogenetic approach

Abstract

The reemergence of gentamicin-susceptible (Gen(s)) methicillin-resistant Staphylococcus aureus (MRSA) isolates in France between 1992 and 1996 was investigated using a phylogenetic approach (multiprimer randomly amplified polymorphic DNA typing). Eighty-six percent (65 of 85) of the French strains were grouped into one phylogenetic cluster within which all but one Gen(s) strain were grouped into a subcluster. Thus, the reemergence of Gen(s) MRSA strains in France was likely due to the spread of one specific clone which belonged to a cluster comprising most French gentamicin-resistant (Gen(r)) strains. This suggests that the Gen(s) clone has emerged from a Gen(r) strain of this cluster.

FIG. 1

Dendrogram (derived using the unweighted pair-group method with arithmetic averages) based on the Jaccard's distance matrix of RAPD results from 100 MRSA strains (75 from France and 25 from other European countries). The susceptibilities to gentamicin (Gen^s and Gen^r are represented as Gn s and Gn r) and the year, country, and department of France in which each MRSA strain was isolated are indicated.

FIG. 2

PFGE typing of Gen^s and Gen^r strains from RAPD clusters 2 and 2a. The Dice coefficient was used to calculate the similarity between each pair of strains.