Ecologie des mycobactéries et mode de contamination humaine

Skin and joint infection by Mycobacterium chelonae: Rescue treatment with interferon gamma

INTRODUCTION

Atypical mycobacteria are environmental organisms that cause opportunistic infections in humans.

CASE REPORT

A 50-year-old electronics engineer sought advice about starting TNFalpha antagonist therapy for ankylosing spondylitis. Disease duration was 23 years and current treatment was methylprednisolone 4 mg/d. Atypical skin lesions and knee arthritis were noted. Fluid aspirated from the knee showed inflammatory properties and a few acid-fast bacteria, which a line probe assay identified as Mycobacterium chelonae. The same organism was found in a skin biopsy from a thigh lesion. Antimicrobial treatment was started immediately. Inadequate results 6 months later prompted synovectomy of the knee followed by interferon gamma, 50 microg/m(2) body surface area subcutaneously 3 times a week. After 16 months, there were no new skin or joint lesions, and the antimicrobials and interferon gamma were therefore discontinued.

CONCLUSION

This highly unusual case suggests that interferon gamma may be effective in patients with M. chelonae infection that fails to respond adequately to antimicrobials.

[Disseminated Mycobacterium avium complex infections in AIDS. Apropos of 100 cases. Groupe d'Epidémiologie clinique du SIDA en Aquitaine]

The improvement of survival of AIDS patients allowed the emergence of disseminated Mycobacterium avium Complex infections (D.MAC). Here we report the experience of the group of "Epidémiologie clinique du sida en Aquitaine (GECSA)" about 100 patients. There were no differences according to sex, age and route of acquisition of HIV. Clinical and biological characteristics of the infections were not specific. The mean TCD4+ lymphocytes count was 18/mm3. The diagnostic was generally established by systematic blood culture on Septi-Chek in patients with TCD4+ lymphocytes count below 75/mm3. The recommendations on therapy for D.MAC are to use regimen containing azithromycin or clarithromycin, ethambutol and one of the following drugs, rifabutin, clofazimine, amikacin, or ciprofloxacin. Rifabutin is recommended for prophylaxis in patients with lymphocytes TCD4+ count below 100/mm3.

Mycobactin analysis as an aid for the identification of Mycobacterium fortuitum and Mycobacterium chelonae subspecies

Mycobactin patterns from 65 Mycobacterium fortuitum and Mycobacterium chelonae strains have been determined by thin-layer chromatography. By use of a rich liquid medium containing an iron chelator (ethylenediamine-di-o-hydroxyphenylacetic acid [EDDA]) to ensure iron starvation, all strains were able to form mycobactins. The method developed here allows sensitive detection of mycobactin by thin-layer chromatography from as little as 5 ml of culture after a 2-week incubation. Within M. fortuitum two mycobactin patterns were identified, whereas within M. chelonae four were recognized. Comparisons with the subspecific identification performed by using biochemical tests showed that 73% of the M. fortuitum subsp. fortuitum strains shared the same mycobactin pattern (designated F), whereas 75% of the M. fortuitum subsp. peregrinum strains shared the other mycobactin pattern (designated P). Within the M. fortuitum strains that cannot be assigned to a subspecies on the basis of their biochemical features, only F and P patterns were determined. Similarly, 93% of the M. chelonae subsp. chelonae strains produced the so-called C1 and C2 patterns and 86% of the M. chelonae subsp. abscessus strains produced A1 and A2 patterns. C2 and A2 were the patterns most frequently encountered; they were represented by 65 and 50% of the M. chelonae subsp. chelonae and M. chelonae subsp. abscessus strains, respectively. Within the biochemically M. chelonae strains that did not fit any subspecies on the basis of biochemical test results, C1, C2, and A1 patterns were found. Whereas about 30% of both M. fortuitum and M. chelonae strains cannot be characterized to the subspecies level on the basis of biochemical tests, 100% of the strains of both species can be characterized on the basis of mycobactin patterns.