After 15 patients had positive cultures for Mycobacterium abscessus without evidence of infection (i.e., pseudoinfection) following endoscopy, retrospective cohort studies of patients undergoing endoscopy and microbiologic sampling of the environment were done to examine potential nosocomial transmission and to identify the source and risk factors for M. abscessus pseudoinfection. In the epidemic period, M. abscessus-positive cultures were significantly more likely to be obtained during bronchoscopy than gastroendoscopy (16/149 vs. 1/860, P < .001) and during procedures using bronchoscopes disinfected in an automated washer rather than by other methods (16/54 vs. 0/95, P < .001). M. abscessus was recovered from the automated washer, the inlet water feeding the washer, and a flexible bronchoscope. Environmental and case-patient isolates had identical large restriction fragment (LRF) patterns of genomic DNA separated by pulsed-field gel electrophoresis. Molecular typing using LRF analysis supported the epidemiologic results and demonstrate the utility of combined epidemiologic and laboratory investigations in nosocomial outbreaks of nontuberculous mycobacteria.

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A retrospective study was done of 602 patients with primary squamous cell carcinoma of the upper aerodigestive tract and a clinically negative neck (No) seen at the University of Illinois Hospital between 1960-1975. There was no uniform policy as to the treatment of No neck during this period; therefore in many of the patients, cervical lymph nodes were treated with elective neck dissection and others were followed until they became positive clinically. It was this difference which formed the basis for this study. All the patients were treated surgically; the patients were placed into two groups depending on whether they had radical neck dissection at the same time as resection of the primary. Group 1 consisted of 149 patients and had surgery for the primary only. The 253 patients of group 2 had surgery for the primary and also had a neck dissection. Both groups were analyzed for recurrences in the cervical region. In group 1, 12.9% of the patients developed either ipsilateral or contralateral metastases. Of the group 2 patients, 22% developed palpable nodal disease. The evolution of palpable nodal disease was analyzed by primary site, T-stage, and according to whether the tumor at the primary was controlled. Only 3% of the patients developed lymph nodes when the primary was controlled. The pathology reports of the neck specimens were studied to determine the relationship between a) positive node histology and b) number of nodes positive to the recurrence rate in the neck. Our results showed a 23% failure rate for the histologically positive group and a 21% failure rate for the negative group. The number of positive nodes did not seem to affect the recurrence rate.