Transferable Resistance to Antibiotics in Gram-Negative Bacteria Isolated in a Hospital for Infectious Diseases: II. Frequency of R Factors and their Transmission between Patients and Personnel in a Salmonella-Shigella Ward

Faecal samples of 35 patients admitted for salmonella or shigella infection to Roslagstull Hospital for Infectious Diseases were examined for antibiotic-resistant gram-negative pathogenic and non-pathogenic bacteria. All 16 shigella strains were multiresistant already at the first isolation, these resistance patterns being transferable in 13 strains. Of 20 salmonella strains 8 had transferable antibiotic resistance on admission. Coexistence of pathogenic and non-pathogenic bacteria carrying the same type of resistance was observed only in 3 of 35 patients. After 1–2 weeks in the hospital all shigella strains but one and 13 of 20 salmonella strains had transferable resistance. The majority of salmonella (18/19) and shigella (11/16) patients carried R+ antibiotic-resistant E. coli or klebsiella-enterobacter strains. The resistance patterns exhibited by these strains and the isolation of strains with similar resistance patterns also from 6 of 14 members of the staff, caring for these patients in the hospital, strongly suggest that the R factors detected are of common origin, possibly from the R+ shigella strains. In a second group of salmonella patients treated with high doses of pirampicillin in an isolation ward, 50% harboured enterobacteria with R factors, mostly transferring resistance only to tetracycline or tetracycline and ampicillin.