Jarolmen H, Kemp G
J Bacteriol. 1969 Aug;99(2):487-90. doi: 10.1128/jb.99.2.487-490.1969.
Experimental infections were induced in weanling pigs orally both with nalidixic acid (NA)-sensitive and -resistant strains of Salmonella choleraesuis var. kunzendorf, designated RC221 and RC221NA, respectively. Prior to the time of infection, cultures of normal bacterial flora were isolated from swine fecal matter and screened for the presence of R factors. A majority of these bacterial isolates harbored transferable resistances. Both strains RC221 and RC221NA have been shown to be competent recipients in vitro of the R factors present in the normal intestinal flora. The property of NA resistance greatly facilitated recovery of the infecting organism. After infection, salmonellae from liver, lung, spleen, lymph node, intestine, and feces were screened for the presence of R factors. Transfer of drug resistance in vivo was a rare occurrence; however, if infected specimens, particularly intestinal, were incubated in nutrient broth prior to plating, R factor transfer occurred, presumably in the test tube. Changes in recipient cultures were frequently observed after introduction of R factors from organisms of pig origin into the S. choleraesuis var. kunzendorf test organisms. Alterations include changes in typing reaction, granular growth in broth, differences in colony form, and reduction of virulence.
分别用对萘啶酸（NA）敏感和耐药的猪霍乱沙门氏菌昆岑多夫变种菌株（分别命名为RC221和RC221NA）经口感染断奶仔猪。在感染前，从猪粪便中分离出正常细菌菌群培养物，并筛选R因子的存在情况。这些细菌分离株中的大多数都带有可转移的耐药性。RC221和RC221NA这两种菌株在体外均已被证明是正常肠道菌群中R因子的有效受体。对NA的耐药特性极大地促进了感染菌的恢复。感染后，对肝脏、肺、脾脏、淋巴结、肠道和粪便中的沙门氏菌进行R因子的筛选。体内耐药性的转移很少发生；然而，如果感染标本，特别是肠道标本，在接种前在营养肉汤中培养，R因子转移就会发生，大概是在试管中发生。将来自猪源生物体的R因子引入猪霍乱沙门氏菌昆岑多夫变种试验生物体后，经常观察到受体培养物的变化。变化包括分型反应的改变、肉汤中的颗粒状生长、菌落形态的差异以及毒力的降低。
