Secondary bacterial infections of buruli ulcer lesions before and after chemotherapy with streptomycin and rifampicin

Buruli ulcer (BU), caused by Mycobacterium ulcerans is a chronic necrotizing skin disease. It usually starts with a subcutaneous nodule or plaque containing large clusters of extracellular acid-fast bacilli. Surrounding tissue is destroyed by the cytotoxic macrolide toxin mycolactone produced by microcolonies of M. ulcerans. Skin covering the destroyed subcutaneous fat and soft tissue may eventually break down leading to the formation of large ulcers that progress, if untreated, over months and years. Here we have analyzed the bacterial flora of BU lesions of three different groups of patients before, during and after daily treatment with streptomycin and rifampicin for eight weeks (SR8) and determined drug resistance of the bacteria isolated from the lesions. Before SR8 treatment, more than 60% of the examined BU lesions were infected with other bacteria, with Staphylococcus aureus and Pseudomonas aeruginosa being the most prominent ones. During treatment, 65% of all lesions were still infected, mainly with P. aeruginosa. After completion of SR8 treatment, still more than 75% of lesions clinically suspected to be infected were microbiologically confirmed as infected, mainly with P. aeruginosa or Proteus miriabilis. Drug susceptibility tests revealed especially for S. aureus a high frequency of resistance to the first line drugs used in Ghana. Our results show that secondary infection of BU lesions is common. This could lead to delayed healing and should therefore be further investigated

Implementing (and evaluating) peer support with people living with noncommunicable diseases in humanitarian settings.

In line with the peer reviewers comments, the authors have added highlights in stead of an abstract. It was felt that it was better able to capture the findings and is more in line with the paper's target audience

Histopathological analysis of tissue from two patients excised weeks after SR8 treatment respectively.

<p>Histological sections were stained with Ziehl-Neelsen (acid fast bacteria) and methylene blue (DNA, secondary infection). A: clinical presentation of patient 9 presenting with a large lesion on the right foot. B: overview over excised tissue specimen (open ulcer surface) revealing the presence of an infection (blue band, box). C/D: higher magnification confirming the presence of densely packed rods. E: clinical presentation of patient 16 presenting with a large lesion covering the left leg. F: overview over excised tissue specimen revealing an epidermal hyperplasia as well as a strong edema. G/H: secondary infection with rods of the dermal and subcutaneous tissue.</p

Antibiotic susceptibility pattern of different bacterial species isolated from BU wounds.

<p>Antibiotic susceptibility pattern of different bacterial species isolated from BU wounds.</p

Histopathological analysis of tissue excised before start of SR8 treatment.

<p>Histological sections were stained with Ziehl-Neelsen (acid fast bacteria) and methylene blue (DNA, secondary infection). A: Overview over excised tissue specimen revealing infection at the lower end of the specimen (box), as well as BU characteristic histopathological features, including fat cell ghosts, necrosis and epidermal hyperplasia. B/C: higher magnification revealing the presence of cocci. D: clinical presentation of the lesion on the belly.</p

Presentation of wounds that were clinically infected after SR8 compared to microbiology and histology findings.

<p>We compared the clinical presentation to microbiological categorization based on quantification and histological findings. Lesions with a bacterial load less than 10⁶ CFU/ml (or CFU/g) were categorized as contaminated, while lesions with bacterial loads above were considered as infected.</p>1<p>WHD = Wound healing delay.</p>2<p>SGF = Skin grafting failure.</p><p>n/d = not done.</p