Elwell L P, De Graaff J, Seibert D, Falkow S
Infect Immun. 1975 Aug;12(2):404-10. doi: 10.1128/iai.12.2.404-410.1975.
Four ampicillin-resistant, beta-lactamase-producing strains of Haempohilus influenzae type b were examined for the presence of plasmid deoxyribonucleic acid (DNA). Three resistant strains contained a 30 x 10-6-dalton (30Mdal) plasmid and one resitant strain contained a 3-Mdal plasmid. The ampicillin-sensitive Haemophilus strains examined did not contain plasmid DNA. Transformation of a sensitive H. influenzae strain to ampicillin resistance with isolated plasmid DNA preparations revealed that the structural gene for beta-lactamase resided on both plasmid species. DNA-DNA hybridization studies showed that the 30-Mdal Haemophilus plasmid contained the ampicillin translocation DNA segment (TnA) found on some R-factors of enteric origin of the H. influenzae plasmids.
对4株产β-内酰胺酶的b型流感嗜血杆菌氨苄西林耐药菌株进行了质粒脱氧核糖核酸（DNA）检测。3株耐药菌株含有一个30×10⁻⁶道尔顿（30Mdal）的质粒，一株耐药菌株含有一个3Mdal的质粒。所检测的氨苄西林敏感流感嗜血杆菌菌株不含质粒DNA。用分离的质粒DNA制剂将一株敏感流感嗜血杆菌菌株转化为氨苄西林耐药，结果显示β-内酰胺酶的结构基因存在于两种质粒上。DNA-DNA杂交研究表明，30Mdal的流感嗜血杆菌质粒含有在某些肠道来源的R因子上发现的氨苄西林易位DNA片段（TnA）以及流感嗜血杆菌质粒。
