Ubiquitous Presence of amecAHomologue in Natural Isolates ofStaphylococcus sciuri

Abstract

In an effort to explore the origin and/or reservoirs of the genetic determinant(s) of methicillin resistance in Staphylococcus aureus, we examined over 200 strains representing 13 different species within the genus Staphylococcus for the presence of the mecA gene, using a DNA probe internal to this gene prepared from a methicillin-resistant strain of S. aureus. Occasional mecA- positive isolates were detected among several staphylococcal species. On the other hand, each one of the 134 isolates of Staphylococcus sciuri, a species considered taxonomically the most primitive among staphylococci and found primarily on rodents and primitive mammals, gave positive reaction with the DNA probe when tested under conditions of high stringency. About two thirds (99) of these isolates, all of which belonged to S. sciuri subspecies "sciuri," as well as 9 of the 11 species carnaticum isolates, showed only marginal, if any, resistance to methicillin (minimal inhibitory concentration of 0.75-6.0 micrograms/ml), while most of the remaining isolates that belonged to the subspecies "rodentius" (13 isolates in all) expressed antibiotic resistance with a heterogeneous phenotype similar to those seen in many methicillin-resistance strains of S. aureus In SmaI digests of chromosomal DNA isolated from such "methicillin-resistant S. aureus-like" strains, the mecA probe hybridized with DNA fragments in the range of 145-180 kb, while in subspecies "sciuri" and carnaticum isolates the mecA hybridizing fragment was located in the SmaI fragment with the highest molecular size (> or = 400 kb). A DNA probe comprising an internal sequence to the regulatory gene mecI from Staphylococcus epidermidis identified the presence of sequences with low degree of homology in isolates of the three S. sciuri subspecies. The mecA-reacting sequences in these bacteria differed from mecA of S. aureus in several respects (e.g., by the absence of a ClaI restriction site from mecA of subspecies "sciuri" and carnaticum, and in some isolates of subspecies "rodentius." The uniform presence of mecA in each one of a large number of S. sciuri strains belonging to distinct ribotypes and macrorestriction patterns and recovered over a 20-year period from a wide variety of animal sources and geographic sites suggests that mecA may be a native genetic element with an as yet unidentified physiologic function in this staphylococcal species.

Methicillin resistance in Staphylococcus aureus requires glycosylated wall teichoic acids

“…Polyvalent scaffolding by glycopolymers (glycolipids and glycoproteins) is a known mechanism for organizing proteins in a variety of biological processes (38,39). Whereas there are no genes of high homology to tarS in Staphylococcus sciuri, the organism from which PBP2a was speculated to derive (40,41), all deposited S. aureus strain sequences in the National Center for Biotechnology Information contain tarS. It is possible that PBP2a may exploit β-OGlcNAcylated WTAs by binding to them directly or by interacting with other cellular factors that are scaffolded by these polymers.…”

Antibiotic Resistance in the Environment, with Particular Reference to MRSA

“…aureus (MSSA) homologue exists (Archer and Neimeyer, 1994) it has been suggested that it was transferred horizontally from a coagulase-negative staphylococcus (CoNS) such as S. sciuri (Couto et al, 1996;Couto et al, 2003). The conjugative transposon containing tetM (tetracycline resistance) has been suggested to pass between Clostridia and staphylococci (Ito et al, 2003), and empirical support for the movement of mobile elements between staphylococci and other low GC gram negative bacteria (Gill et al, 2005), and the potential transfer of vanA (vancomycin resistance) from Enterococcus faecalis to S. aureus (Weigel et al, 2003) lends weight to the possibility of a common gene pool available to many bacterial species (Hanssen et al, 2004).…”

Staphylococcus hominis subsp. novobiosepticus subsp. nov., a novel trehalose- and N-acetyl-D-glucosamine-negative, novobiocin- and multiple-antibiotic-resistant subspecies isolated from human blood cultures

“…The proportion of S. hominis in the Staphylococcus community is often higher on the glabrous skin of the arms and legs than on other body regions. Strains of S. hominis colonize the skin of a person for relatively short periods of time, usually several weeks to several months, compared to many of the strains of the predominant species Staphylococcus epidermidis that persist for one to several years (Kloos, 1986b;Kloos et al, 1992 1971 1972 1971 1971 1972 1971 1972 1971 1973 1981 198 1 1984 1984 1984 1984 1985 1985 1985 1985 1985 1985 1985 1985 1987 1987 1987 1987 1987 1992 Unknown Unknown Unknown Unknown 1992-1 993 1992-1 993 1992-1 993 1992-1 993 1992-1993 1991 1989 1992-1993 1992-1993 1992-1993 1992-1 993 1992-1 993 1992-1 993 1992-1993 1992-1 993 1992-1 993 1992-1993 1992-1 993 1992-1993 19921992Unknown 1994199619961996 Unknown 1992-1 993…”