| salmonella typhi resistant to chloramphenicol, ampicillin, and other antimicrobial agents: strains isolated during an extensive typhoid fever epidemic in mexico. | during 1972 a large epidemic, in excess of 10,000 cases, of typhoid fever occurred in mexico city, pachuca, and other communities of mexico. the main characteristic of the epidemic, in addition to the large number of persons affected, was the prevalence of a strain of salmonella typhi which was highly resistant to chloramphenicol both in vivo and in vitro, and which belonged to a single phage type, vi degraded approaching type a. of 493 strains of s. typhi studied during the outbreak, 452 (91.7% ... | 1973 | 4602828 |