The evolution of methicillin resistance in Staphylococcus aureus: Similarity of genetic backgrounds in historically early methicillin-susceptible and-resistant isolates and contemporary epidemic clones
Mi. Crisostomo et al., The evolution of methicillin resistance in Staphylococcus aureus: Similarity of genetic backgrounds in historically early methicillin-susceptible and-resistant isolates and contemporary epidemic clones, P NAS US, 98(17), 2001, pp. 9865-9870
Citations number
33
Categorie Soggetti
Multidisciplinary
Journal title
PROCEEDINGS OF THE NATIONAL ACADEMY OF SCIENCES OF THE UNITED STATES OF AMERICA
The key genetic component of methicillin resistance, the mecA determinant,
is not native to Staphylococcus aureus. Thus, the evolution of methicillin-
resistant S. aureus (MRSA) must have begun with the acquisition of the mer-
A determinant from an unknown heterologous source sometime before the first
reported appearance of MRSA isolates in clinical specimens in the U.K. and
Denmark (in the early 1960s). We compared the genetic backgrounds and phen
otypes of a group of methicillin-susceptible S. aureus (MSSA) isolates to t
he properties of MRSA strains isolated in Denmark and the U.K. during the s
ame time period, and also to the genetic profiles of contemporary epidemic
clones of MRSA. All early MRSA isolates resembled a large group of the earl
y MSSA blood isolates in phenotypic and genetic properties, including phage
group, antibiotype (resistance to penicillin, streptomycin, and tetracycli
ne), pulsed-field gel electrophoresis pattern, and spaA type and multilocus
sequence type, strongly suggesting that the early MSSA examined here repre
sented the progeny of a strain that served as one of the first S. aureus re
cipients of the methicillin-resistance determinant in Europe. The genetic b
ackground of this group of early MSSA isolates was also very similar to tha
t of the widely disseminated contemporary "Iberian clone" of MRSA, suggesti
ng that genetic determinants present in early MSSA and essential for some a
spects of the epidemicity and/or virulence of these strains may have been r
etained by this highly successful contemporary MRSA lineage.