Genetic diversity of arginine catabolic mobile element in Staphylococcus epidermidis.
BACKGROUND
The methicillin-resistant Staphylococcus aureus clone USA300 contains a novel mobile genetic element, arginine catabolic mobile element (ACME), that contributes to its enhanced capacity to grow and survive within the host. Although ACME appears to have been transferred into USA300 from S. epidermidis, the genetic diversity of ACME in the latter species remains poorly characterized.


RESULTS
To assess the prevalence and genetic diversity of ACME, 127 geographically diverse S. epidermidis isolates representing 86 different multilocus sequence types (STs) were characterized. ACME was found in 51% (65/127) of S. epidermidis isolates. The vast majority (57/65) of ACME-containing isolates belonged to the predominant S. epidermidis clonal complex CC2. ACME was often found in association with different allotypes of staphylococcal chromosome cassette mec (SCCmec) which also encodes the recombinase function that facilities mobilization ACME from the S. epidermidis chromosome. Restriction fragment length polymorphism, PCR scanning and DNA sequencing allowed for identification of 39 distinct ACME genetic variants that differ from one another in gene content, thereby revealing a hitherto uncharacterized genetic diversity within ACME. All but one ACME variants were represented by a single S. epidermidis isolate; the singular variant, termed ACME-I.02, was found in 27 isolates, all of which belonged to the CC2 lineage. An evolutionary model constructed based on the eBURST algorithm revealed that ACME-I.02 was acquired at least on 15 different occasions by strains belonging to the CC2 lineage.


CONCLUSIONS
ACME-I.02 in diverse S. epidermidis isolates were nearly identical in sequence to the prototypical ACME found in USA300 MRSA clone, providing further evidence for the interspecies transfer of ACME from S. epidermidis into USA300.
Miragaia
Maria
M
Laboratory of Molecular Genetics, Instituto de Tecnologia Química e Biológica, Universidade Nova de Lisboa (ITQB/UNL), Oeiras, Portugal.
de Lencastre
Herminia
H
Perdreau-Remington
Francoise
F
Chambers
Henry F
HF
Higashi
Julie
J
Sullam
Paul M
PM
Lin
Jessica
J
Wong
Kester I
KI
King
Katherine A
KA
Otto
Michael
M
Sensabaugh
George F
GF
Diep
Binh An
BA
D002412:Cations; D003001:Cloning, Molecular; D004251:DNA Transposable Elements; D004352:Drug Resistance, Microbial; D005798:Genes, Bacterial; D005821:Genetic Techniques; D014644:Genetic Variation; D005838:Genotype; D006867:Hydrolases / Q000235:genetics; D055624:Methicillin-Resistant Staphylococcus aureus / Q000235:genetics; D005810:Multigene Family; D016133:Polymerase Chain Reaction; D012150:Polymorphism, Restriction Fragment Length; D013212:Staphylococcus epidermidis / Q000235:genetics*; D014774:Virulence
D002412:Cations; D004251:DNA Transposable Elements; D006867:Hydrolases; C019723:arginine deiminase