Falbo V, Famiglietti M, Caprioli A
Laboratorio di Ultrastrutture, Istituto Superiore di Sanità, Rome, Italy.
Infect Immun. 1992 Jun;60(6):2182-7. doi: 10.1128/iai.60.6.2182-2187.1992.
Cytotoxic necrotizing factors (CNFs) are Escherichia coli protein toxins causing cell multinucleation and enlargement in tissue cultures and necrosis in rabbit skin. In E. coli isolates causing urinary tract infections in humans, the production of CNF1 is closely associated with hemolysin production. In this study, we obtained data suggesting that this phenotypic association is due to the genetic linkage of the determinants of the two toxins on the chromosome of uropathogenic E. coli. The genes encoding hemolysin and CNF1 were shown to be closely linked in a 37-kb cloned DNA fragment from an E. coli urinary tract isolate of serotype O4:K12:H5 (E-B35). A DNA region encoding CNF1 production but not hemolysin production was further subcloned as a 12-kb SalI-EcoRI fragment and used as a CNF1-specific gene probe. DNA hybridization experiments indicated that the CNF1 and hemolysin determinants were closely linked on the chromosomes of isolate E-B35 and six additional extraintestinal isolates belonging to serogroups O2, O4, O6, O22, O75, and O85.
细胞毒性坏死因子（CNFs）是大肠杆菌蛋白毒素，可在组织培养中导致细胞多核化和肿大，并在兔皮中引起坏死。在引起人类尿路感染的大肠杆菌分离株中，CNF1的产生与溶血素的产生密切相关。在本研究中，我们获得的数据表明，这种表型关联是由于尿路致病性大肠杆菌染色体上两种毒素的决定因素存在遗传连锁。编码溶血素和CNF1的基因在来自血清型O4:K12:H5（E-B35）的大肠杆菌尿路分离株的37 kb克隆DNA片段中显示紧密连锁。一个编码CNF1产生但不编码溶血素产生的DNA区域进一步亚克隆为12 kb的SalI-EcoRI片段，并用作CNF1特异性基因探针。DNA杂交实验表明，CNF1和溶血素决定因素在分离株E-B35以及属于血清群O2、O4、O6、O22、O75和O85的另外六种肠道外分离株的染色体上紧密连锁。
