Changes in Inflammatory Markers in Patients Treated for Buruli Ulcer and Their Ability to Predict Paradoxical Reactions

Abstract

Mycobacterium ulcerans causes Buruli ulcer, the third most frequent mycobacterial disease after tuberculosis and leprosy. Transient clinical deteriorations, known as paradoxical reactions (PRs), occur in some patients during or after antibiotic treatment. We investigated the clinical and biological features of PRs in a prospective cohort of 41 patients with Buruli ulcer from Benin. Neutrophil counts decreased from baseline to day 90, and interleukin 6 (IL-6), granulocyte colony-stimulating factor, and vascular endothelial growth factor were the cytokines displaying a significant monthly decrease relative to baseline. PRs occurred in 10 (24%) patients. The baseline biological and clinical characteristics of the patients presenting with PRs did not differ significantly from those of the other patients. However, the patients with PRs had significantly higher IL-6 and tumor necrosis factor alpha (TNF-α) concentrations on days 30, 60, and 90 after the start of antibiotic treatment. The absence of a decrease in IL-6 and TNF-α levels during treatment should alert clinicians to the possibility of PR onset.

Keywords: Mycobacterium ulcerans; Buruli ulcer; inflammatory response; paradoxical reaction.

Figure 1.

Study flowchart. Abbreviation: PR, paradoxical reaction.

Figure 2.

White blood cell (WBC) counts in the whole cohort from baseline to day 90 (horizontal lines represent medians, boxes are drawn from quartiles 1 to 3, and whiskers indicate the minimum to the maximum). Statistical analyses were performed with paired, nonparametric Wilcoxon test (Benjamini–Hochberg false discovery rate method). *P < .05, **P < .01, ****P < .0001.

Figure 3.

Change in biomarker levels for the whole cohort from baseline to day 90 (horizontal lines represent medians, boxes are drawn from quartiles 1 to 3, and whiskers indicate the minimum to the maximum). Statistical analyses were performed with paired, nonparametric Wilcoxon test (Benjamini–Hochberg false discovery rate method). *P < .05, **P < .01, ****P < .0001. Abbreviations: FGF, fibroblast growth factor; G-CSF, granulocyte colony-stimulating factor; IFN-γ, interferon gamma; IL, interleukin; IP-10, interferon-γ–induced protein 10; PDGF-β, platelet-derived growth factor beta; TNF-α, tumor necrosis factor alpha; VEGF, vascular endothelial growth factor.

Figure 4.

A, Leukocyte counts from baseline to day 90, plotted for the paradoxical reaction (PR) and no-PR groups. B, Changes in monocyte counts from baseline (start of antibiotic treatment) to day 90 in the PR and no-PR groups. Individual ratios of monocyte counts from baseline for the PR and no-PR groups (horizontal lines represent medians, boxes are drawn from quartiles 1 to 3, and whiskers indicate the minimum to the maximum). Statistical analyses were performed with unpaired, nonparametric Mann–Whitney tests. **P < .01.

Figure 5.

A, Changes in the levels of immune biomarkers between baseline and day 90 in the PR and no-PR groups. Statistical analyses were performed with unpaired, nonparametric Mann–Whitney tests. *P < .05, **P < .01. B, Heatmap of normalized values for each soluble immune marker, with a comparison of median values at baseline and on days 30, 60, and 90. ▴ indicates significant difference for day 30 relative to day 0; ♦ indicates significant difference for day 60 relative to day 0; ★ indicates significant difference for day 90 relative to day 0. Abbreviations: FGF, fibroblast growth factor; G-CSF, granulocyte colony-stimulating factor; IFN-γ, interferon gamma; IL, interleukin; IP-10, interferon-γ–induced protein 10; MIP-1, macrophage inflammatory protein 1; PDGF-β, platelet-derived growth factor beta; PR, paradoxical reaction; TNF-α, tumor necrosis factor alpha; VEGF, vascular endothelial growth factor.

Figure 6.

Levels of interleukin 6 and tumor necrosis factor alpha between patients with Buruli ulcer (BU) and control groups. Results for BU patients (n = 31) were obtained at day 0, before antibiotic treatment. Non-BU patients (n = 60) are patients managed for another condition contemporaneously in the same hospital. Healthy controls (n = 19) are healthy blood donors sampled in France. Comparisons were performed with Kruskal–Wallis test with Dunn test for multiple comparisons. *P < .05, ***P < .001. Abbreviations: BU, Buruli ulcer; FGF, fibroblast growth factor; G-CSF, granulocyte colony-stimulating factor; IL, interleukin; IP-10, interferon-γ–induced protein 10; TNF-α, tumor necrosis factor alpha.