Emergence and epidemiology of vancomycin-resistant enterococci in Australia

Enterococci with acquired resistance to vancomycin and other glycopeptides (VRE) have emerged and spread rapidly through Europe and the United States since 1988. The first isolate of VRE in Australia occurred in 1994. Only one case was noted in 1995. Since March 1996 there has been a steady increase in the number of reports of VRE throughout the country. To August 1998 there have been 69 documented strains or clusters of strains detected in patients with documented infection, and about 3 times as many strains have been detected through screening procedures of contacts or in risk groups. 19% of strains whose source was known were blood isolates, while 34% came from urine and 47% came from other specimens. The strains have been found in 26 institutions in 10 widely separated cities or regions of the country (in 6/8 states or territories), without any obvious temporal associations in their appearance. All strains appear to have arisen locally except for one strain imported from the United Kingdom. Furthermore there was no direct evidence of interhospital transfer of strains. All clinical strains were examined by PCR to confirm species and to test for the presence of known vancomycin-resistance genes. Of the 69 strains, 42 were vanB E. faecium, 12 were vanA E. faecium, 9 were vanB E. faecalis, 3 were vanA E. faecalis. Three were negative for vanA, vanB, vanC1, vanC2/C3 and vanD. PGFE profiles on 38 strains have revealed at least 8 types of vanB E. faecium, 6 of vanA E. faecium, 4 of vanB E. faecalis and 2 of vanA E. faecalis. Isolates containing vanA always had different profiles from those containing vanB. Clinical clustering was confirmed by PFGE, and supported by extended antibiogram. 14 of 15 E. faecalis were ampicillin susceptible compared to only 2 of 54 E. faecium. One E. faecalis strain was beta-lactamase positive. The epidemiology of VRE in Australia appears to be different from that of Europe or the United States, since vanB E. faecium predominates and strains have appeared in diverse locations independently and are highly polyclonal