Genotyping of Treponema pallidum in patients with early syphilis in Guangxi province

Abstract

Objective To investigate genotyps of Treponema pallidum (Tp) in several cities in Guangxi province. Methods A total of 300 patients with suspected early syphilis were enrolled from STD clinics in Guangxi between January 2012 and July 2016, and tissue fluid samples were collected from skin lesions. Silver staining was performed to detect Tp, and PCR to amplify the Tp polA gene for the diagnosis of early syphilis. Positive samples were subjected to PCR amplification of a 60-bp tandem repeat region within the arp gene, restriction fragment length polymorphism (RFLP) analysis of the tpr Ⅱ gene after digestion with Mse Ⅰ enzyme and tp0548 genotyping. Results Finally, 215 patients were diagnosed with early syphilis, including 210 (97.7%) patients positive for PCR and 105 (48.8%) patients positive for silver staining, and the positive rate significantly differed between the two methods (χ2= 103.01, P < 0.05) . Among the PCR-positive samples, 190 could be genotyped by analysis of three target genes, and 17 genotypes were identified. The genotype 14d/f was predominant (45.3%, 86/190) , followed by 15d/f (13.7%, 26/190) , 16d/f (11.6%, 22/190) , 17d/f (7.4%, 14/190) , 13d/f (6.8%, 13/190) , 10d/f (4.2%, 8/190) , 18d/f (1.6%, 3/190) , 16a/f (1.6%, 3/190) , 5d/f (1.1%, 2/190) , 7d/f (1.1%, 2/190) , 12d/f (1.1%, 2/190) , 16d/e (1.1%, 2/190) , 14a/f (1.1%, 2/190) , 9h/c (1.1%, 2/190) , 15l/f (0.5%, 1/190) , 25a/e (0.5%, 1/190) , 15i/f (0.5%, 1/190) . Conclusion Tp genotypes are diversified in patients with early syphilis in Guangxi, and the genotype 14 d/f is predominant. Key words: Syphilis; Treponema pallidum; Genotyping techniques; Polymerase chain reaction; Silver staining