Olarte J, Galindo E
Antimicrob Agents Chemother. 1973 Dec;4(6):597-601. doi: 10.1128/AAC.4.6.597.
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%) were resistant to chloramphenicol (CM), tetracycline (TC), streptomycin (SM), and sulfonamides (SU). The epidemic strain owes its resistance to an R factor which is easily transferable to Escherichia coli K-12 and which appears to be stable. In the third month of the outbreak, a strain of S. typhi resistant to CM, TC, SM, SU, ampicillin (AM), and kanamycin (KM) was isolated from a patient with severe typhoid fever. During the following 9 months, six additional strains of S. typhi resistant to AM, CM, TC, SM, and SU were also isolated. Transfer experiments to E. coli K-12 indicate that these strains are infected with two different R factors, one causing CM, TC, SM, and SU resistance and the other causing AM or AM and KM resistance. The frequency of transfer of the resistance in overnight crosses was in the order of 10(-4) for CM, TC, SM, and SU and 10(-6) for AM or AM, and KM. The appearance of these strains resistant both to chloramphenicol and ampicillin was a cause for concern for the clinicians; fortunately, they have remained an infrequent cause of disease.
1972年期间，墨西哥城、帕丘卡及墨西哥其他社区爆发了一场大规模伤寒疫情，病例超过10000例。此次疫情的主要特点，除了受影响人数众多外，是一株伤寒沙门氏菌的流行，该菌株在体内和体外对氯霉素均具有高度抗性，且属于单一噬菌体类型，即Vi降解接近A型。在疫情爆发期间研究的493株伤寒沙门氏菌中，452株（91.7%）对氯霉素（CM）、四环素（TC）、链霉素（SM）和磺胺类药物（SU）耐药。流行菌株的耐药性归因于一种R因子，该因子易于转移至大肠杆菌K - 12，且似乎很稳定。在疫情爆发的第三个月，从一名重症伤寒患者身上分离出一株对CM、TC、SM、SU、氨苄青霉素（AM）和卡那霉素（KM）耐药的伤寒沙门氏菌。在接下来的9个月里，又分离出另外6株对AM、CM、TC、SM和SU耐药的伤寒沙门氏菌。对大肠杆菌K - 12的转移实验表明，这些菌株感染了两种不同的R因子，一种导致对CM、TC、SM和SU耐药，另一种导致对AM或AM和KM耐药。在过夜杂交中，CM、TC、SM和SU耐药性的转移频率约为10^(-4)，而AM或AM和KM耐药性的转移频率为10^(-6)。这些对氯霉素和氨苄青霉素均耐药的菌株的出现引起了临床医生的关注；幸运的是，它们仍然是罕见的致病原因。
