Molecular characterization of Treponema pallidum pallidum in children with acquired syphilis by nonsexual contact by multilocus sequencing

GARCIA, LUCIANA; MORANDO, NICOLAS; OTERO, ADRIAN VLADIMIR; MORONI, SAMANTA; MOSCATELLI, GUILLERMO; GONZALEZ, NICOLAS; LASCANO, FERNANDA; PANDO, MARIA ANGELES; ALTCHEH, JAIME

Mendoza

Congreso; XIX Congreso Latinoamericano de Infectología Pediátrica; 2021

Syphilis is caused by Treponema pallidum pallidum (TPA). The scarce data about the biology of TPA during the complex clinical stages and the multiple routes of transmission allows syphilis tocause a large proportion of morbidity in children. The use of molecular biology techniques (MBT) in the diagnosis of syphilis is in the beginnings. In 2019 we initiate a multicenter clinical study evaluating the implementation of MBT for the diagnosis of syphilis in children. Our aim is evaluate the performance of real time PCR (qPCR) in blood and swab samples for the detection of dnaA gen and the characterization of TPA by multilocus sequence typing (MSLT). A strict evaluation detected 4 cases of congenital syphilis, 16 cases of acquired secondary syphilis transmitted through nonsexual contact and 12 cases of acquired secondary syphilis transmitted through sexual contact in teenagers (total=42). Of these, 99 samples were processed for DNA extraction (QIAGEN, Germany) followed by qPCR usingTaqman probes. The global efficiency per patient was: Sensitivity (Se)=78.1, Specificity(Sp)=100, Positive predictive value(PPV)=100, Negative predictive value(NPV) = 69.6; with lowest values in blood samples (16.1/100/100/38.1 )and highest in swab samples (88.5/100/100/70). So far, 8 patients have been studied for MSLT. Edition and alignment were performed compared to the reference sequences of SS14 (CP004011.1), Nichols (CP004010.2) andEscherichia coli 23s rRNA genes at the positions 2058 and 2059 (V00331) for azithromycin (AZ) resistant mutation. All samples except one, predicted to be AZ sensitive based on 23S A2058 allele.Nichols-like samples (n=5) belong to the 9.7.3 allelic profile while SS14-like samples (n=3) belong to the 1.1.1 allelic profile. These preliminary data support the use of qPCR methods as confirmatorytechniques in children syphilis and bring important data of TPA genome in these populations, which is an urgent need for prevention policies and vaccine development.