Paradoxical reactions in Buruli ulcer after initiation of antibiotic therapy: Relationship to bacterial load

Abstract

Background: We investigated the relationship between bacterial load in Buruli ulcer (BU) lesions and the development of paradoxical reaction following initiation of antibiotic treatment.

Methods: This was a longitudinal study involving BU patients from June 2013 to June 2017. Fine needle aspirates (FNA) and swab samples were obtained to establish the diagnosis of BU by PCR. Additional samples were obtained at baseline, during and after treatment (if the lesion had not healed) for microscopy, culture and combined 16S rRNA reverse transcriptase/ IS2404 qPCR assay. Patients were followed up at regular intervals until complete healing.

Results: Forty-seven of 354 patients (13%) with PCR confirmed BU had a PR, occurring between 2 and 42 (median 6) weeks after treatment initiation. The bacterial load, the proportion of patients with positive M. ulcerans culture (15/34 (44%) vs 29/119 (24%), p = 0.025) and the proportion with positive microscopy results (19/31 (61%) vs 28/90 (31%), p = 0.003) before initiation of treatment were significantly higher in the PR compared to the no PR group. Plaques (OR 5.12; 95% CI 2.26-11.61; p<0.001), oedematous (OR 4.23; 95% CI 1.43-12.5; p = 0.009) and category II lesions (OR 2.26; 95% CI 1.14-4.48; p = 0.02) were strongly associated with the occurrence of PR. The median time to complete healing (28 vs 13 weeks, p <0.001) was significantly longer in the PR group.

Conclusions: Buruli ulcer patients who develop PR are characterized by high bacterial load in lesion samples taken at baseline and a higher rate of positive M. ulcerans culture. Occurrence of a PR was associated with delayed healing.

Trial registration: ClinicalTrials.gov NCT02153034.

Fig 1. Flowchart of study participants, 2013–2017.

Fig 2. Typical paradoxical reactions in Buruli ulcer following antibiotic treatment.

A: New nodular lesion on the left thigh of a patient with an indurated lesion before antibiotic treatment, B: Paradoxically enlarged ulcer of lesion A during antibiotic therapy at week 4. C: Multiple new lesions (red arrows) around the original lesion on the left elbow (blue arrow) at week 5 of antibiotic treatment.

Fig 3. Increased bacterial load at baseline in patients who developed paradoxical reaction (PR+) in comparison to those who did not (PR-).

Higher viable M. ulcerans in lesions of patients who subsequently developed paradoxical reaction post treatment as measured by 16S rRNA at baseline compared those who did not. Each point represents the number of copies per milliliter (log₁₀) of sample. The horizontal bars show the means and standard deviations of each group.

Fig 4. Images of 2 patients (A and B) who had positive 16S rRNA and culture results after 8 weeks of antibiotic treatment.

Patient A; Presented with a plaque on the right thigh with surrounding induration (week 0) which reduced significantly after antibiotic treatment (week 8). A new lesion appeared on the right knee at week 10 at the same time as the original lesion on the right thigh re-ulcerated (PR at week 10). Patient B; Presented with an ulcer on the left elbow (week 0), there was improvement after antibiotic treatment as evidenced by formation of clean granulation tissue with some epithelization (week 8). A new lesion was seen close to the initial lesion (PR at week 11).

Fig 5. Kaplan Meier analysis for time to complete healing in Buruli ulcer patients who developed paradoxical reaction and those who did not following antibiotic treatment.

Broken lines indicate the median healing time (weeks) for each group.