title: R factors in strains of Salmonella typhi and Shigella dysenteriae 1 isolated during epidemics in Mexico: classification by compatibility.
abstract: All 17 Salmonella typhi strains tested from the epidemic in Mexico carried R factors of compatibility group H, conferring resistance to chloramphenicol, streptomycin, tetracycline, and sulfonamides. Some S. typhi strains carried, in addition, non-conjugative, ampicillin resistance plasmids and R factors of the I or A-C complex. All 20 Shigella dysenteriae 1 strains tested of epidemic origin carried O-group R factors. Ampicillin resistance in S. dysenteriae 1 was not proved to be plasmid borne. R factors of group H were not identified in any of the tested Mexican isolates other than S. typhi, but R factors of group O were identified in Escherichia coli, Shigella flexneri, and one strain of S. typhi, as well as in the epidemic S. dysenteriae. An R factor was identified which seemed to have two compatibility specificities, groups Iomega and O.
mesh_terms: D004196:Disease Outbreaks; D004352:Drug Resistance, Microbial; D004405:Dysentery, Bacillary / Q000453:epidemiology / Q000382:microbiology; D004926:Escherichia coli / Q000187:drug effects; D005111:Extrachromosomal Inheritance; D007194:India; D008800:Mexico; D012475:Salmonella / Q000187:drug effects*; D012762:Shigella dysenteriae / Q000187:drug effects*; D013019:South Africa; D014435:Typhoid Fever / Q000453:epidemiology / Q000382:microbiology