In vitro assay to demonstrate high-level erythromycin resistance of a clinical isolate of Treponema pallidum

Abstract

We have previously demonstrated that cells of Treponema paUidum freshly extracted from infected rabbit testes can be intrinsically radiolabeled with [35S]methionine to very high specific activities. In this study we used the inhibition of [35S]methionine incorporation into trichloroacetic acid-precipitable protein in vitro as an assay to test the susceptibilities of three different pathogenic treponemal strains to various antibiotics. In general, the results correlated very well with the known efficacies of these antibiotics in treating human patients with syphilis. One of the strains tested, however, a clinical isolate of T. paUidum designated street strain 14, was found to exhibit high-level resistance to erythromycin and a closely related macrolide, roxithromycin (RU 965). Street strain 14 was originally isolated from a human patient with active secondary syphilis who failed to respond to erythromycin therapy. Thus, our results indicate that an erythromycin-resistant strain of T. paUidum can be responsible for erythromycin treatment failure. In addition, street strain 14 treponemes were found to be generally less susceptible by this assay to a variety of antibiotics than were treponemes of the T. pallidum Nichols strain. These findings suggest that the outer envelope of street strain 14 treponemes may be generally less permeable to antibiotics than is that of Nichols strain treponemes.

Molecular Typing of Treponema pallidum in the Czech Republic during 2011 to 2013: Increased Prevalence of Identified Genotypes and of Isolates with Macrolide Resistance

“…The A2058G mutation encodes resistance to azithromycin, clarithromycin, erythromycin, and roxithromycin but not resistance to spiramycin (30)(31)(32). In contrast, A2059G is likely associated with resistance to all commonly used macrolides, including spiramycin (10).…”

“…The reaction mixture was supplemented with PCR-grade water to a final volume of 25 l. All sets of specimens were first PCR tested with 1 l of isolated DNA. PCRnegative reaction mixtures were repeatedly tested with 10 l of isolated DNA from a total volume of 100 l. PCR amplification of polA and tmpC was performed under the following cycling conditions: 94°C (1 min); 94°C (30 Statistical methods. Analysis of statistical significance was performed with Fisher's exact two-tailed test with STATISTICA software v. 12 (StatSoft, Tulsa, OK).…”

Syphilis: using modern approaches to understand an old disease

“…The first macrolide-resistant strain of T. pallidum (Street strain 14) was isolated in 1977 (117,118), and no other such resistant strains were reported until 2004. Street strain 14 is highly resistant to both erythromycin and azithromycin (117, 119) by virtue of an adenine-to-guanine (A→G) mutation at the position cognate to A2058 in the E. coli 23S rRNA gene…”

Efficacy of cefmetazole in the treatment of active syphilis in the rabbit model

“…Currently recommended alternatives, tetracycline and erythromycin (4), have several disadvantages: (i) patient compliance may be poor because of required four-timesdaily dosing for periods of 2 to 4 weeks; (ii) both tetracycline (10) and erythromycin (8) exhibit poor CNS penetration and their therapeutic efficacy in inapparent or known neurological involvement has not been closely examined; and (iii) neither drug is appropriate for treatment of syphilis in pregnant women. Furthermore, the treatment failure rate is higher in patients treated with erythromycin (3,7,28) and an erythromycin-resistant strain of T. pallidum has been isolated (30). For these reasons, new alternatives to penicillin should be sought.…”