An outbreak of infection with Mycobacterium chelonae subsp. abscessus after the injection of penicillin in 86 patients attending a factory hospital is reported. The bacterium was isolated both from lids and from the soil where the drug was stored. Molecular analysis by sodium dodecyl sulfate-polyacrylamide gel electrophoresis of whole-cell proteins and plasmids revealed a pattern identical to that of the strains isolated from the wounds. The source of the infections was soil contamination of the vial lids and was caused by improper use and sterilization of penicillin vials.Mycobacterium chelonae subsp. abscessus, a rapidly growing atypical mycobacterium, is part of the normal flora in the respiratory tract and the digestive tract of healthy human beings and animals and is widely distributed in soil, wastewater, and other materials. As a human pathogen, it seldom infects the lungs, but it often causes infections of skin and soft tissues, especially local infections and abscesses after surgery or intramuscular injection (1-3). Here we describe infection on a large scale caused by M. chelonae subsp. abscessus after the injection of penicillin, the investigation of the reason for the infection, and the development of prevention measures.From January 1997 to July 1998, a factory hospital in Chongqing, China, received 86 patients with local infections at injection sites, on the right or left buttock or both buttocks. Among them, 31 were male and 55 were female, the oldest was 80 years old and the youngest was merely 1 year 1 month old, 55 (64%) were more than 55 years old and 9 (10.5%) were less than 6 years old, and 22 (25.5%) were between 55 and 6 years old. Initially, the skin of the injection sites of the patients became red and swollen, and then scleroma appeared and an abscess formed. The pus was thin and did not give off any extraordinary odor. After the necrotic tissue was resected and the pus was drained, the inflammation still could not be controlled, and the wound would not heal. The infection spread along the interstitial spaces and caused inguinal lymphadenitis through lymphatic vessels. However, general symptoms, such as a sensation of chills or fever, and lung infection did not occur.Samples from the pus, curettage deep in the abscess, and swollen lymph nodes of all patients were examined. The bacteriologic examination was carried out by microscopy of paraffin sections of these materials stained by the Gram stain method. Many gram-positive bacilli were arranged in V or L shapes in the interstitial spaces, with deeply stained granules in the bodies of the bacilli (Fig. 1). After being cultured on blood agar plates for 3 days at 35°C, the organism developed into smooth, mucoid, round, thin, yellow colonies without hemolysis. At that time, according to the shape and staining characteristics, the organism would have been identified as Corynebacterium. Examination with the API Coryne autoanalytical system (Biomerieux, Marcy l'Etoile, France) indicated that the organism was most likely Corynebacterium equi. T...