Nida S K, Ferretti J J
Infect Immun. 1982 May;36(2):745-50. doi: 10.1128/iai.36.2.745-750.1982.
Phage conversion of group A streptococci to produce streptococcal exotoxins was shown to occur more widely than has been previously reported. Toxigenic conversion was found in 19 newly constructed lysogenic and pseudolysogenic strains resulting in synthesis of exotoxin types A and B. Conversion was accomplished by a positive conversion effector, which was a phage characteristic expressed by the prophage and vegetatively reproducing phage. Exotoxin production was determined by the rabbit skin test and by countercurrent immunoelectrophoresis with type-specific antisera. New lysogens and pseudolysogens were constructed with strains which failed to produce at least one exotoxin type. Phages were obtained from toxigenic strains isolated from cases of scarlet fever. Conversions were consistent and repeatable; loss of the recently introduced phage was accompanied by loss of the newly acquired toxin productivity. Conversion resulted in production of additional exotoxin type or types and never affected existing toxin synthesis. Converting phages were characterized by electron microscopy and negatively stained preparations and were all found to be of morphological class B1. All phage nucleic acid was double-stranded DNA. Though similar in structure, each converting phage had a different host range, and the nine new converting phages identified here did not react with antiserum prepared against the originally reported converting phage.
A群链球菌通过噬菌体转化产生链球菌外毒素的现象比之前报道的更为普遍。在19株新构建的溶原性和类溶原性菌株中发现了产毒转化，导致A型和B型外毒素的合成。转化是由一种阳性转化效应因子完成的，该因子是原噬菌体和增殖噬菌体所表达的噬菌体特征。通过兔皮试和用型特异性抗血清进行对流免疫电泳来测定外毒素的产生。用至少不能产生一种外毒素类型的菌株构建新的溶原菌和类溶原菌。噬菌体从猩红热病例中分离出的产毒菌株中获得。转化是一致且可重复的；最近引入的噬菌体的丢失伴随着新获得的毒素产生能力的丧失。转化导致产生额外的一种或多种外毒素类型，且从不影响现有的毒素合成。通过电子显微镜和负染制剂对转化噬菌体进行了表征，发现它们均属于形态学B1类。所有噬菌体核酸均为双链DNA。尽管结构相似，但每种转化噬菌体具有不同的宿主范围，此处鉴定出的9种新的转化噬菌体与针对最初报道的转化噬菌体制备的抗血清不发生反应。
