Risk factors for Mycobacterium ulcerans infection, southeastern Australia

Buruli/Bairnsdale ulcer (BU) is a severe skin and soft tissue disease caused by Mycobacterium ulcerans. To better understand how BU is acquired, we conducted a case-control study during a sustained outbreak in temperate southeastern Australia. We recruited 49 adult patients with BU and 609 control participants from a newly recognized BU-endemic area in southeastern Australia. Participants were asked about their lifestyle and insect exposure. Odds ratios were calculated by using logistic regression and were adjusted for age and location of residence. Odds of having BU were at least halved for those who frequently used insect repellent, wore long trousers outdoors, and immediately washed minor skin wounds; odds were at least doubled for those who received mosquito bites on the lower legs or lower arms. This study provides new circumstantial evidence that implicates mosquitoes in the transmission of M. ulcerans in southeastern Australia.

Paradoxical exacerbation of psoriasis in AIDS: proposed explanations including the potential roles of substance P and gram-negative bacteria

Psoriasis, a TH1-induced disorder, is not more common in human immunodeficiency virus (HIV) infection than in the general population. However, it may appear for the first time or pre-existing psoriasis may worsen and be difficult to treat in HIV disease. The paradoxical exacerbation of psoriasis in AIDS has not been fully explained. Various explanations have been proposed including (a) the reduction of Langerhans' cells (LCs) in HIV disease, (b) the direct epidermal proliferative effect of HIV, (c) the altered cytokine profile in HIV disease, (d) HIV-induced macrophage nitric oxide (NO) production, (e) the increased CD8/CD4 T-cell ratio in HIV infection and (f) the increased colonization of skin by Staphylococcus aureus. However, the observations that (a) LCs cells play an important role in the pathogenesis of psoriasis and a variety of topical and systemic psoriasis treatments cause a reversible decrease in LC function, (b) psoriasis may improve in end-stage HIV infection, (c) overproduction of some TH2 cytokines and underproduction of IL-2 in HIV infection, and (d) the presence of NO favors a TH2 response over a TH1 response make the first four explanations difficult to interpret. Since psoriasis is exacerbated in HIV infection possibly due to the increased staphylococcal colonization, and psoriatic keratinocytes could aggravate HIV infection through production of TNF-alpha, it could be reasoned that in HIV-positive psoriatics a strong vicious cycle is present between the degree of immune deficiency and the staphylococcal colonization, explaining the poor prognosis of both AIDS and psoriasis in these patients. With reference to the studies which indicate significant involvement of substance P (SP) in the pathogenesis of psoriasis and on the other hand increased release of this agent by HIV-infected immune cells it is proposed that SP plays an important role in creating the paradox. Since in HIV-positive psoriatics the source of SP is largely immune cells not neurons, capsaicin, which exerts its action selectively on a subpopulation of neurons, could not be of significant therapeutic value. As SP significantly enhances HIV-1 replication in latently infected immune cells, psoriatic lesions, being heavily infiltrated with immune cells and having high concentrations of SP, could serve as high HIV-replication foci, with the resultant rapid progression of the infection towards AIDS. Additionally, given that lipopolysaccharide is supposed to exacerbate psoriasis, increase of gram-negative infections or cutaneous colonization with these organisms in AIDS may partly explain the paradox. Understanding the HIV-induced immunodysregulation that is associated with psoriasis in some HIV-seropositive patients may assist in the delineation of the immunopathogenesis of the disease in HIV-seronegative psoriatics.

Susceptibility to local and systemic bacterial infections in intercellular adhesion molecule 1-deficient transgenic mice

The contribution of intercellular adhesion molecule 1 (ICAM-1) during systemic and local bacterial infections was studied in transgenic ICAM-1-deficient and control mice that were injected intraperitoneally (ip) or intradermally (id) with Escherichia coli, Pseudomonas aeruginosa, or Staphylococcus aureus. Mortality rates, blood cultures, white blood cell (WBC) counts and absolute neutrophil counts (ANCs) were obtained daily until cultures were sterile. Six and 24 h after injections, autopsies were done on randomly selected ip-inoculated mice and biopsies were done on randomly selected id-inoculated mice. Survival rates were similar. In ICAM-1-deficient mice, ip P. aeruginosa resulted in higher incidences of bacteremia at 24 h (P = .003) and 48 h (P = .002); id S. aureus resulted in larger skin lesions (P = .026). Leukocytosis persisted in ICAM-1-deficient mice 6 h after ip injection of E. coli; however, WBC counts and ANCs in peritoneal fluid did not differ. Although the inflammatory responses were similar histologically in ICAM-1-deficient and normal mice, differences in site- and stimulus-specific susceptibilities were noted.

Pulmonary sarcoidosis and chronic cutaneous atypical mycobacter ulcer

This interesting case of pulmonary sarcoidosis and Mycobacterium ulcerans ulcers raises many issues: 1. Our paucity of knowledge of deficient immune status in individuals; the multifarious presentation as recognisable ill health, its early detection, treatment and its prevention. In this present case the management of the immune status of the patient has not yet been fully addressed. The relationship between his pulmonary sarcoidosis as being an 'immune' response to the Mycobacterium ulcerans remains speculative; for example, did this patient have the Mycobacterium infection before he was diagnosed as having sarcoidosis? There is no evidence of this. With the history of repeated cellulitis associated with his business trips to Asia and the Middle East, the likelihood seems speculative--as would infection with Mycobacterium ulcerans contracted from swimming in pools and rivers. 2. As sarcoidosis is thought to have an association with Mycobacterium tuberculosis it is tempting to suggest that as, in this case, the Mycobacterium ulcerans is the caus-ative agent for his sarcoidosis. Additionally, should we be looking for sarcoidosis in every other case of Mycobacterium ulcerans infection? Other cases of Mycobacterium ulcerans could be assessed. 3. It is suggested that corticosteroids do pave the way for opportunistic infection as in this case. How often does this occur in 'usual practice' where patients are exposed to corticosteroids? Further comments are invited. 4. The question of sterility techniques in the home (daily dressings), the surgery, and at work as a food handler, is noted as a matter of concern. 5. The implications of the problem having any work-related association is also noted in passing.