Identification of Persistent Infection in Experimental Syphilis by PCR

Abstract

The studies described herein were designed to evaluate the usefulness of the PCR in detecting persistent syphilitic infection. Three groups of animals were used: a nonimmune group infected withTreponema pallidum (NI/TP), a nonimmune group injected with heat-killed treponemes (NI/HKTP), and an immune and reinfected group (I/TP). All animals were inoculated with similar numbers of organisms distributed at 10 sites on the clipped back and in both testes. The persistence of the treponemes was examined by PCR and the rabbit infectivity test (RIT). The kinetic studies and statistical analysis of their results demonstrated that the rate of bacterial clearance from the NI/TP group was very low and incomplete at 4 months after infection. It was significantly different from those of both the NI/HKTP (P < 0.001) and I/TP (P < 0.05) groups. No statistically significant differences in treponemal elimination were found between the NI/HKTP and I/TP groups. PCR can detect the DNA of dead organisms, but the latter are eliminated by the host relatively quickly (15 to 30 days) as compared to elimination of live treponemes (>120 days). PCR results correlated well with RIT results. These data suggest that PCR-positive specimens obtained from an untreated patient(s) or collected weeks after treatment indicate persistent infection. They also show that the process of elimination ofT. pallidum from primary sites of infection is prolonged and incomplete.

Cytokine gene expression in skin of susceptible guinea‐pig infected with Treponema pallidum

“…Careful examination of primary syphilitic lesions in rabbit 6 and guinea‐pig ( Fig. 4) revealed a variable but consistent presence of true eosinophils (larger than pseudo‐eosinophils and containing three‐ to fourfold larger eosinophilic granules), in addition to the mononuclear cell infiltration.…”

“…2,3 The pathogen is not fully eradicated, allowing the occurrence of secondary and tertiary stages of reactivation in a substantial number of untreated individuals. 3 The local and systemic persistence of the pathogen far beyond the healing of local lesions and establishment of ‘chancre immunity’ has been reported by several investigators 4,5 and confirmed in the rabbit 6 and guinea‐pig models of syphilis (submitted for publication). We have shown that the guinea‐pig is a suitable host for studies of experimental syphilis, 7,8 and delineation of mechanisms of immunity.…”

Prevalence and Clinical Manifestations of Penile Gonococcal Cutaneous and Accessory Gland Infections in Men With Gonorrhea

“…Thus, this patient might have been infected with gonococcus in the secretions of the partner's pharynx because of the trauma on the inner plate of the prepuce during oral sex. Because of limited conditions, we were unable to perform PCR detection of T. pallidum 25,26 ; however, 2 dark-field microscopic examinations for T. pallidum showed negative results.…”

A critical analysis of research methods and experimental models to study the root canal microbiome

“…Because root canal samples are usually taken in a cross‐sectional study design, it is not possible to assume that bacteria that have died during the course of the infection have not participated in the disease aetiology. Besides, bacterial DNA is rapidly cleared from different host sites after cell death (Aul et al, 1998; Malawista et al, 1994; Post et al, 1996; Wicher et al, 1998), especially when it is released in an environment with active infection, because of the fast degradation by DNases released by the other viable bacteria (Brundin et al, 2010; Leduc et al, 1995). Serum, which also contains DNases, can rapidly decompose free DNA to levels below the detection limit of molecular methods (Brundin et al, 2010).…”