The histopathology is described of 190 skin biopsies from 71 patients who presented during an epidemic of nodules and abscesses in the periumbilical region and buttocks, secondary to the application of xylocaine injections. Positive cultures for Mycobacterium abscessus were obtained from the specimens and from the xylocaine solution. The severe inflammatory lesions involved the dermis and the hypodermis and had three main histopathological patterns: (i) granulomatous nodular or diffuse inflammation with mixed granulomas in 57 (80%) of the cases; (ii) prevailing abscesses with mild granulomatous reaction in 28 (15%) of the biopsies; and (iii) deep dermal and subcutaneous granulomatous inflammation with no neutrophil component in three (4%) of cases. Bacilli were detected in 51 (27%) of the specimens, frequently forming small clumps at the centre of clear spaces or vacuoles and which were lipid-like structures in 156 (82%) of the abscesses or granulomas. This series represents one of the largest reported outbreaks caused by atypical mycobacteria and in which the source of infection was confirmed. The results emphasize the essential role of skin biopsies in determining the histopathological substrate, in helping to detect the atypical mycobacterial origin and in encouraging the practice of cultures for the identification of micro-organisms.

SUMMARYWe describe an outbreak of skin lesions due to Mycobacterium chelonae subsp. abscessus associated with injections of lidocaine (lignocaine) given by a 'bioenergetic' (a practitioner of alternative medicine) in Colombia. The lidocaine carpules and the lesions of the patients yielded mycobacteria with identical biochemical characteristics.Using the methodology of Sartwell and a case control design we examined the incubation period and assessed risk factors. Of 667 potentially exposed individuals, a total of 298 patients were interviewed, of whom 232 had skin lesions. The median incubation period was 305 days (range 15-59 days). Male sex (OR 2-85, 95 % CI 126-6-5 1), increasing age (OR 1-25, 95 % CI 103-1-53), subcutaneous injection route (OR 3-72, 95 % CI 1-09-12-7) and number of injections (OR 101, 95% CI 1001-03) were risk factors for disease.To our knowledge, this is the largest reported outbreak of M. chelonae infection, the first in which the organism has been isolated from the putative vehicle of infection, and the first in which the incubation period could be determined.

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