Distribution of mercury resistance among Staphylococcus aureus isolated from a hospital community.

Results from clinical isolations confirmed that mercury resistance is common among antibiotic-resistant strains of Staphylococcus aureus present in a large general hospital although the correlation is not as high as that found by Moore (1960).The distribution of mercury-resistant strains among infections and carriers in surgical, medical, obstetric and geriatric patients and staff was studied. Attention was directed to the distribution among carriers since there are fewer extraneous factors operating among them, and a statistical analysis was made on the total number of mercury-resistant strains and the number of non-endemic strains; this latter figure was obtained by subtracting the dominant type 80/81, which is nearly always mercury-resistant and antibiotic-resistant, from the total. Analysis showed the geriatric patients to have a significantly higher proportion of mercury-resistant strains in both cases, and obstetric patients to have a significantly lower proportion when the total number of mercury-resistant strains was considered. Among the surgical, medical and staff categories, no significant difference in proportions could be found although a trend, in that order, of decreasing proportions of mercury-resistant strains present was noted.In those cases infected on admission with tetracycline-resistant strains, although mercury-resistant strains still predominate, mercury-sensitive strains make a sizeable contribution. This is a reflexion of their dominance in the non-hospital environment.