Treponema pallidum subsp. pallidum strains DAL-1 and Philadelphia 1 differ in generation times in vitro as well as during experimental rabbit infection

• Published in: PloS one Vol. 19; no. 5; p. e0304033
• Main Authors: Bosák, Juraj, Mikalová, Lenka, Hrala, Matěj, Pospíšilová, Petra, Faldyna, Martin, Šmajs, David
• Format: Journal Article
• Language: English
• Published: United States Public Library of Science 24-05-2024; Public Library of Science (PLoS)
• Subjects: Animals; Comparative analysis; Disease control; Erythema; Experiments; Health aspects; Infection; Infections; Inoculation; Inoculum; Male; Medical laboratories; Microscopy; Nutrient availability; Nutrients; Pathogenicity; Pathogens; Physiological aspects; Rabbits; Syphilis; Syphilis - microbiology; Syphilis - pathology; Testes; Testis - metabolism; Testis - microbiology; Treponema pallidum; Virulence; Pennsylvania; Mexico; Czech Republic; Chicago Illinois; United States > US
• ISSN: 1932-6203; 1932-6203
• DOI: 10.1371/journal.pone.0304033

In this work, we determined that Treponema pallidum subsp. pallidum (TPA) DAL-1 (belonging to Nichols-like group of TPA strains) grew 1.53 (± 0.08) times faster compared to TPA Philadelphia 1 (SS14-like group) during in vitro cultivations. In longitudinal individual propagation in rabbit testes (n = 12, each TPA strain), infection with DAL-1 manifested clinical symptoms (induration, swelling, and erythema of testes) sooner than Philadelphia 1 infection, which resulted in a significantly shorter period of the experimental passages for DAL-1 (median = 15.0 and 23.5 days, respectively; p < 0.01). To minimize the confounding conditions during rabbit experiments, the growth characteristics of DAL-1 and Philadelphia 1 strains were determined during TPA co-infection of rabbit testes (n = 20, including controls). During two weeks of intratesticular co-infection, DAL-1 overgrew Philadelphia 1 in all twelve testes, regardless of inoculation ratio and dose (median of relative excess DAL-1 multiplication = 84.85×). Moreover, higher DAL-1 to Philadelphia 1 inoculum ratios appeared to increase differences in growth rates, suggesting direct competition between strains for available nutrients during co-infection. These experiments indicate important physiological differences between the two TPA strains and suggest growth differences between Nichols-like and SS14-like strains that are potentially linked to their virulence and pathogenicity.