ABSTRACT
ObjectiveTo evaluate the performance of a three-gene typing system in the determination of Treponema pallidum (Tp) genotypes.MethodsTo determine the genotypes of Tp,three targets were assessed,including the number of 60 base-pair repeats,restriction fragment length polymorphism(RFLP) pattem of tprEGJ gene after MseI digestion and the sequence of tp0548 gene.The DNA extracted from the Nichols strain of Tp served as the positive control,and that from the moist ulcer of patients with genital herpes and negative RPR or TPPA test results served as the negative control.To validate the typing method,clinical specimens were collected from the moist skin lesions of patients with primary or secondary syphilis,and subjected to the amplification of polA gene by PCR.The enhanced molecular typing system was used to determine the genotypes of Tp in Tp DNA-positive specimens.ResultsThe Nichols strain harbored a genotype of 14a/a.No amplification of any of the three target genes was found in the negative control.The arp gene,tprEGJ gene and tp0548 gene were amplified from 94.1％,91.2％ and 94.1％ of the 40 clinical specimens,and the genotype was successfully determined by the three-gene typing system for 91.2％ of the clinical Tp strains.The predominant type of arp,tprEGJ and tp0548 genes was 14 repeats,d and f,respectively in these clinical Tp isolates.ConclusionThe enhanced molecular tying method for Tp exhibits high sensitivity,specificity and discrimination potential.
ABSTRACT
Objective To make a nationwide external quality assessment for drug sensitivity testing of Neisseria gonorrhoeae, analyze the problems in and factors associated with the drug sensitivity testing, and to enhance the quality of drug sensitivity testing of N. gonorrhoeae at different monitoring sites. Methods Samples were uniformly delivered to monitoring sites by express mail service. Test results were analyzed in the National Center for STD Control, and the evaluation results were fed back to these monitoring sites. Results A total of 105 quality control samples were delivered from 2007 to 2009, with a response rate of 88.57% (93/105). Thirteen monitoring sites were enrolled in the external quality assessment, including 9 laboratories in 2007, 9 in 2008 and 13 in 2009. The total percentage amounted to 77.42% (24/31) for qualified laboratories during the 3 years, including 6 laboratories in 2007, 7 in 2008 and 11 in 2009. The coincidence rate increased for the detection of penicillinase-producing N. gonorrhoeae (PPNG), N. gonorrhoeae with chromosome-mediated ciprofloxacin resistance, and N. gonorrhoeae with chromosome-mediated spectinomycin resistance, and declined for the detection of N. gonorrhoeae with plasmid-mediated high level tetracycline-resistance (TRNG) and N. gonorrhoeae with chromosome-mediated ceftriaxone resistance. Conclusions The 3-year external quality assessment reveals an improvement in the overall quality of drug sensitivity testing of N. gonorrhoeae at national monitoring sites; the accuracy is improved markedly for the detection of PPNG, N. gonorrhoeae with resistance to spectinomycin and ciprofloxacin, but is needed to increase for the detection of ceftriaxone-resis- tant N. gonorrhoeae and TRNG.