GENOME ORGANIZATION OF STAPHYLOCOCCUS-AUREUS ISOLATES FROM DIFFERENT POPULATIONS

Isolates from three different Staphylococcus aureus populations were e xamined for restriction fragment length polymorphisms (RFLPs) of total DNA digested with the endonuclease SmnI, The populations were: commun ity S, aureus isolates collected at random from healthy individuals (3 8 isolates); methicillin-resistant S, aureus (MRSA) type strains invol ved in separate outbreaks of infection in Melbourne (1982) and Canberr a (1990) (two isolates); and a collection of clinical methicillin-sens itive S, aureus (MSSA) causing hospital infection (20 isolates), RFLPs with CspI and SmaI and hybridisation analyses of both, showed that th e community and the MSSA isolates were not genetically closely related , and, accordingly, they could not be grouped into clusters as seen wi th the MRSA types, However, a few MSSA isolates were found to be close ly related to each other and appeared to be similar to the standard st rain S. aureus 8325-4 and to some MRSA types, Although there was subst antial variability between the three groups, physical mapping with gen omic DNA fragments from the standard strain S. aureus 8325-4 to probe large fragments generated with CspI and SmaI from the chromosomes of s elected community and MRSA isolates, demonstrated a well conserved gen ome organisation between representative isolates from the three groups .