Translocating Mycobacterium ulcerans: An experimental model

Abstract

Mycobacterium ulcerans is a non-tuberculous environmental mycobacterium responsible for extensive cutaneous and subcutaneous ulcers in mammals, known as Buruli ulcer in humans. M. ulcerans has seldom been detected in the faeces of mammals and has not been detected in human faeces. Nevertheless, the detection and isolation of M. ulcerans in animal faeces does not fit with the current epidemiological schemes for the disease. Here, using an experimental model in which rats were fed with 109 colony-forming units of M. ulcerans, we detected M. ulcerans DNA in the faeces of challenged rats for two weeks and along their digestive tract for 10 days. M. ulcerans DNA was further detected in the lymphatic system including in the cervical and axillary lymph nodes and the spleen, but not in any other tissue including healthy and broken skin, 10 days post-challenge. These observations indicate that in some herbivorous mammals, M. ulcerans contamination by the digestive route may precede translocation and limited contamination of the lymphatic tissues without systemic infection. These herbivorous mammals may be sources of M. ulcerans for exposed populations but are unlikely to be reservoirs for the pathogen.

Experimental infection of ringtail possums with Mycobacterium ulcerans, the agent of Buruli ulcer

“…Body weight also remained relatively stable throughout the experiment, although two animals did experience a drop in body condition just prior to euthanasia which may have been an early indication of the considerably morbidity and mortality that ringtail possums experience under natural conditions 9 . Weight loss has been observed previously in a horse naturally infected with MU and in human patients with unusual BU disease manifestations [19][20][21] , but not in most human patients or in experimentally infected rats or mice 22,23 . Infected humans do not shed MU DNA in their feces 24 and whilst fecal shedding has been observed in rats, mice and naturally infected possums, the impact of MU infection on fecal production has not been assessed previously.…”

“…ingestion). Rats that were orally challenged with high doses of MU subsequently expressed MU DNA both within and beyond their digestive systems, with samples of cervical, mesenteric and axillary lymph nodes, serum and spleen testing PCR positive 22 .…”

Understanding the transmission of Mycobacterium ulcerans: A step towards controlling Buruli ulcer

“…In most cases, rodents likely ingest M . ulcerans while consuming aquatic plants without developing systemic infections [ 101 , 102 ]. There is minimal evidence that other animals in West Africa may be hosts of M .…”