ABSTRACT
Methicillin-resistant strains susceptible to gentamicin (Gm
s
MRSA) have emerged since 1993 in several French hospitals. To study whether particular clones have spread in various French cities and whether some clones are related to gentamicin-resistant (Gm
r
) MRSA strains, various methods (antibiotyping, phage typing, determination of
Sma
I macrorestriction patterns before and after hybridization with IS
256
transposase and
aacA-aphD
probes) were used to compare 62 Gm
s
MRSA strains isolated from 1995 to 1997 in nine cities and 15 Gm
r
MRSA strains. Eighteen major
Sma
I genotypes were identified, of which 11 included only Gm
s
MRSA strains and 5 included only Gm
r
MRSA strains. Each of the Gm
r
MRSA strains contained 6 to 13
Sma
I fragments hybridizing with the insertion sequence IS
256
, of which a single band also hybridized with the
aacA-aphD
gene. No such hybridizing sequences were detected in 60 of the 62 Gm
s
MRSA strains. Thus, the divergence between Gm
r
and Gm
s
MRSA strains is revealed, not only by their distributions in distinct
Sma
I genotypes but also by the differences in hybridization patterns. Two of the 62 Gm
s
MRSA strains had the uncommon feature of carrying several
Sma
I bands hybridizing with IS
256
, suggesting that they are possibly related to the Gm
r
MRSA strains grouped in the same
Sma
I genotype. Five of the 11
Sma
I genotypes including only Gm
s
MRSA strains contained strains from diverse cities, isolated during different years and with different antibiograms, suggesting that some clones have spread beyond their cities of origin and persisted.
Molecular Typing of Methicillin Resistant Staphylococcus aureus Strains Isolated from Cows and Farm Workers
