Macrolide resistance in yaws

Low genetic diversity of Treponema pallidum ssp. pertenue (TPE) isolated from patients' ulcers in Namatanai District of Papua New Guinea: Local human population is infected by three TPE genotypes

Yaws is an endemic disease caused by Treponema pallidum subsp. pertenue (TPE) that primarily affects children in rural regions of the tropics. The endemic character of yaws infections and the expected exclusive reservoir of TPE in humans opened a new opportunity to start a yaws eradication campaign. We have developed a multi-locus sequence typing (MLST) scheme for TPE isolates combining the previously published (TP0548, TP0488) and new (TP0858) chromosomal loci, and we compared this typing scheme to the two previously published MLST schemes. We applied this scheme to TPE-containing clinical isolates obtained during a mass drug administration study performed in the Namatanai District of Papua New Guinea between June 2018 and December 2019. Of 1081 samples collected, 302 (28.5%) tested positive for TPE DNA, from which 255 (84.4%) were fully typed. The TPE PCR-positivity in swab samples was higher in younger patients, patients with single ulcers, first ulcer episodes, and with ulcer duration less than six months. Non-treponemal serological test positivity correlated better with PCR positivity compared to treponema-specific serological tests. The MLST revealed a low level of genetic diversity among infecting TPE isolates, represented by just three distinct genotypes (JE11, SE22, and TE13). Two previously used typing schemes revealed similar typing resolutions. Two new alleles (one in TP0858 and one in TP0136) were shown to arise by intragenomic recombination/deletion events. Compared to samples genotyped as JE11, the minor genotypes (TE13 and SE22) were more frequently detected in samples from patients with two or more ulcers and patients with higher values of specific TP serological tests. Moreover, the A2058G mutation in the 23S rRNA genes of three JE11 isolates was found, resulting in azithromycin resistance.

Trial of Three Rounds of Mass Azithromycin Administration for Yaws Eradication

BACKGROUND

Treponema pallidum subspecies pertenue causes yaws. Strategies to better control, eliminate, and eradicate yaws are needed.

METHODS

In an open-label, cluster-randomized, community-based trial conducted in a yaws-endemic area of Papua New Guinea, we randomly assigned 38 wards (i.e., clusters) to receive one round of mass administration of azithromycin followed by two rounds of target treatment of active cases (control group) or three rounds of mass administration of azithromycin (experimental group); round 1 was administered at baseline, round 2 at 6 months, and round 3 at 12 months. The coprimary end points were the prevalence of active cases of yaws, confirmed by polymerase-chain-reaction assay, in the entire trial population and the prevalence of latent yaws, confirmed by serologic testing, in a subgroup of asymptomatic children 1 to 15 years of age; prevalences were measured at 18 months, and the between-group differences were calculated.

RESULTS

Of the 38 wards, 19 were randomly assigned to the control group (30,438 persons) and 19 to the experimental group (26,238 persons). A total of 24,848 doses of azithromycin were administered in the control group (22,033 were given to the participants at round 1 and 207 and 2608 were given to the participants with yaws-like lesions and their contacts, respectively, at rounds 2 and 3 [combined]), and 59,852 doses were administered in the experimental group. At 18 months, the prevalence of active yaws had decreased from 0.46% (102 of 22,033 persons) at baseline to 0.16% (47 of 29,954 persons) in the control group and from 0.43% (87 of 20,331 persons) at baseline to 0.04% (10 of 25,987 persons) in the experimental group (relative risk adjusted for clustering, 4.08; 95% confidence interval [CI], 1.90 to 8.76). The prevalence of other infectious ulcers decreased to a similar extent in the two treatment groups. The prevalence of latent yaws at 18 months was 6.54% (95% CI, 5.00 to 8.08) among 994 children in the control group and 3.28% (95% CI, 2.14 to 4.42) among 945 children in the experimental group (relative risk adjusted for clustering and age, 2.03; 95% CI, 1.12 to 3.70). Three cases of yaws with resistance to macrolides were found in the experimental group.

CONCLUSIONS

The reduction in the community prevalence of yaws was greater with three rounds of mass administration of azithromycin at 6-month intervals than with one round of mass administration of azithromycin followed by two rounds of targeted treatment. Monitoring for the emergence and spread of antimicrobial resistance is needed. (Funded by Fundació "la Caixa" and others; ClinicalTrials.gov number, NCT03490123.).

Determination of Lekethromycin, a Novel Macrolide Lactone, in Rat Plasma by UPLC-MS/MS and Its Application to a Pharmacokinetic Study

Lekethromycin, a new macrolide lactone, exhibits significant antibacterial activity. In this study, a reliable analytical ultrahigh-performance liquid chromatography electrospray ionization quadrupole Orbitrap high-resolution mass spectrometry (UPLC-ESI-Orbitrap-MS) method was established and validated for the detection of lekethromycin in rat plasma. After a simple acetonitrile (ACN)-mediated plasma protein precipitation, chromatographic separation was performed on a Phenomenex Luna Omega PS C18 column (30 × 2.1 mm i.d. particle size = 3 μm) conducted in a gradient elution procedure using 0.5% formic acid (FA) in ACN and 0.5% FA in water as the mobile phase pumped at a flow rate of 0.3 mL/min. Detection was carried out under positive electrospray ionization (ESI+) conditions in parallel reaction monitoring (PRM) mode with observation of m/z 804.5580 > 577.4056 for lekethromycin and 777.5471 > 619.4522 for gamithromycin (internal standard, IS). The linear range was 5–1000 ng/mL (r² > 0.99), and the lower limit of quantification (LLOQ) was 5 ng/mL. The intra- and inter-day precision (expressed as relative standard deviation, RSD) values were ≤7.3% and ≤6.3%, respectively, and the accuracy was ≥90% ± 5.3%. The mean extraction recovery RSD valWeue was <5.1%. Matrix effects and dilution integrity RSD values were <5.6% and <3.2%, respectively. Lekethromycin was deemed stable under certain storage conditions. This fully validated method was effectively applied to study the pharmacokinetics of lekethromycin after a single intravenous administration of 5 mg/kg in rats. The main pharmacokinetic parameters were T_1/2λz, CL_obs and V_Z_obs were 32.33 ± 14.63 h, 0.58 ± 0.17 L/h/kg and 25.56 ± 7.93 L/kg, respectively.

Strain diversity of Treponema pallidum subsp. pertenue suggests rare interspecies transmission in African nonhuman primates

In our most recent study, we found that in Tanzania infection with Treponema pallidum (TP) subsp. pertenue (TPE) is present in four different monkey species. In order to gain information on the diversity and epidemiological spread of the infection in Tanzanian nonhuman primates (NHP), we identified two suitable candidate genes for multi-locus sequence typing (MLST). We demonstrate the functionality of the MLST system in invasively and non-invasively collected samples. While we were not able to demonstrate frequent interspecies transmission of TPE in Tanzanian monkeys, our results show a clustering of TPE strains according to geography and not host species, which is suggestive for rare transmission events between different NHP species. In addition to the geographic stability, we describe the relative temporal stability of the strains infecting NHPs and identified multi-strain infection. Differences between TPE strains of NHP and human origin are highlighted. Our results show that antibiotic resistance does not occur in Tanzanian TPE strains of NHP origin.

Advances in the Treatment of Yaws

Yaws is one of the three endemic treponematoses and is recognised by the World Health Organization as a neglected tropical disease. Yaws is currently reported in 15 countries in the Pacific, South-East Asia, West and Central Africa, predominantly affects children, and results in destructive lesions of the skin and soft tissues. For most of the twentieth century penicillin-based treatment was the standard of care and resistance to penicillin has still not been described. Recently, oral azithromycin has been shown to be an effective treatment for yaws, facilitating renewed yaws eradication efforts. Resistance to azithromycin is an emerging threat and close surveillance will be required as yaws eradication efforts are scaled up globally.

Community-based mass treatment with azithromycin for the elimination of yaws in Ghana-Results of a pilot study

INTRODUCTION

The WHO yaws eradication strategy consists of one round of total community treatment (TCT) of single-dose azithromycin with coverage of > 90%.The efficacy of the strategy to reduce the levels on infection has been demonstrated previously in isolated island communities in the Pacific region. We aimed to determine the efficacy of a single round of TCT with azithromycin to achieve a decrease in yaws prevalence in communities that are endemic for yaws and surrounded by other yaws-endemic areas.

METHODS

Surveys for yaws seroprevalence and prevalence of skin lesions were conducted among schoolchildren aged 5-15 years before and one year after the TCT intervention in the Abamkrom sub-district of Ghana. We used a cluster design with the schools as the primary sampling unit. Among 20 eligible primary schools in the sub district, 10 were assigned to the baseline survey and 10 to the post-TCT survey. The field teams conducted a physical examination for skin lesions and a dual point-of-care immunoassay for non-treponemal and treponemal antibodies of all children present at the time of the visit. We also undertook surveys with non-probabilistic sampling to collect lesion swabs for etiology and macrolide resistance assessment.

RESULTS

At baseline 14,548 (89%) of 16,287 population in the sub-district received treatment during TCT. Following one round of TCT, the prevalence of dual seropositivity among all children decreased from 10.9% (103/943) pre-TCT to 2.2% (27/1211) post-TCT (OR 0.19; 95%CI 0.09-0.37). The prevalence of serologically confirmed skin lesions consistent with active yaws was reduced from 5.7% (54/943) pre-TCT to 0.6% (7/1211) post-TCT (OR 0.10; 95% CI 0.25-0.35). No evidence of resistance to macrolides against Treponema pallidum subsp. pertenue was seen.

DISCUSSION

A single round of high coverage TCT with azithromycin in a yaws affected sub-district adjoining other endemic areas is effective in reducing the prevalence of seropositive children and the prevalence of early skin lesions consistent with yaws one year following the intervention. These results suggest that national yaws eradication programmes may plan the gradual expansion of mass treatment interventions without high short-term risk of reintroduction of infection from contiguous untreated endemic areas.