Properties of methicillin‐resistant staphylococci now endemic in Australia

Antimicrobial resistance of Staphylococcus aureus: genetic basis.

“…This idea is supported by the observations that Tn4002 (Pc9) and pT181 (Tcr) each occupied a common site in all strains tested (157; Gillespie and Skurray, unpublished data; Jones and Pattee, personal communication). Such evidence also supports the notion that many Mcr strains have a common origin (223,255) and that the "new" multiresistant hospital staphylococci are in fact "old" staphylococci that have acquired additional chromosomal resistance determinants by integration as well as by mutation, as in the case of rifampin and fusidic acid resistances (149,259,506). In contrast to IS256, IS257 sequences occur at limited sites on the chromosome and so far only in conjunction with the determinants for methicillin, mercury, and tetracycline resistance (28; Matthews et al, submitted; Gillespie, et al, submitted).…”

“…There may well be other properties encoded by these plasmids, the maps of which are far from genetic saturation, which endow their hosts with a selective advantage. For example, it is not known if any of the plasmids carried by these contemporary strains, including the small phenotypically cryptic plasmids (293), influence their host's apparent propensity to colonize patients; it may be noted that these strains do not show enhanced resistance to either linolenic acid (307), a component of skin lipid which is inhibitory for S. aureus (267), or desiccation (149). Further, in the development of a multiresistant chromosome, it…”

Outcome and Attributable Mortality in Critically Ill Patients With Bacteremia Involving Methicillin-Susceptible and Methicillin-Resistant Staphylococcus aureus

“…Several experimental, in vitro studies tried to find stronger virulence attributes in MRSA strains. 18,19,[36][37][38][39][40][41][42] Of all these laboratory investigations, only 1 reported a higher production of lipase in MRSA strains, 42 and one found MRSA strains to have a lesser ability to bind to fibronectin compared with MSSA strains. 18 These data make us conclude that the virulence of staphylococci is more closely tied to particular strains than to methicillin resistance.…”

Remodeling of pSK1 Family Plasmids and Enhanced Chlorhexidine Tolerance in a Dominant Hospital Lineage of Methicillin-Resistant Staphylococcus aureus

“…Early ST239 MRSA isolates were first recognized in Australia because they displayed resistance to gentamicin (16–18), encoded by a bifunctional acetyltransferase-phosphotransferase gene [ aac(6′)-aph(2ʺ) ] commonly carried on pSK1-like plasmids as part of the composite transposon Tn 4001 (19, 20). pSK1 represents a family of intermediate-sized (20- to 40-kb), theta-replicating staphylococcal plasmids that have been recovered in Australia and the United Kingdom (19, 21–24).…”