Contamination of clinical specimens by Mycobacterium gordonae is a signific
ant endemic problem in many laboratories. To investigate this problem, 84 c
ases at 1 hospital were retrospectively identified during 20 months. The ov
erall rate of specimen contamination was 2.4%, and 72 of the contaminated s
pecimens were respiratory. A case-control comparison showed that the risk o
f respiratory specimen contamination was significantly increased If the spe
cimen was expectorated (odds ratio [OR], 3.62; 95% confidence interval [CI]
, 1.36-9.50) or if the patient consumed fluids within 2 days before specime
n collection (OR, 8.92; 95% CI, 1.40-71.20). Cultures of tap water, ice, an
d iced drinking water all yielded M. gordonae at 10(-2)-10(0) cfu/ml. A cul
ture survey of consenting patients showed contamination of 8 (24%) of 34 sp
utum specimens collected immediately after a tap water mouth rinse. These f
indings demonstrate that endemic specimen contamination arises from mycobac
teria in hospital tap water and provide a foundation for control efforts.