Journal of Clinical Microbiology, October 1998, p. 2861-2864, Vol. 36, No. 10
0095-1137/98/$04.00+0
Copyright © 1998, American Society for Microbiology. All rights reserved.

Infectious Disease Epidemiology and Surveillance Division1 and Bureau of Laboratories,3 Texas Department of Health, Austin, Texas 78756, and Epidemiology Program Office, Centers for Disease Control and Prevention, Atlanta, Georgia 303332
Received 16 March 1998/Returned for modification 13 May 1998/Accepted 1 July 1998
The number of Salmonella agona isolates reported annually in Texas from 1992 through 1994 ranged from 14 to 21. An increase in incidence of S. agona infections was noted in the fall of 1995. Pulsed-field gel electrophoresis (PFGE) analysis identified prospectively two possible cryptic outbreaks caused by an indistinguishable strain which was isolated from 18 of 59 patients who were culture positive from March through December 1995. These 18 patients had onset of illness from 20 May through 3 October 1995. Eight individuals resided in the Austin area, eight resided in San Antonio, and two resided in Houston; none had attended a common social gathering or owned common pets. Six patients in San Antonio and one patient from Houston recalled eating food items from the same Mexican food restaurant in San Antonio. S. agona organisms with the same PFGE profile were isolated from machacado, an air-dried, raw beef product prepared at the restaurant. The machacado had been shredded in a kitchen blender which was the probable source for cross-contamination of other food items. Five patients in Austin reported eating at a popular Mexican food restaurant in Austin. Improperly prepared machacado also may have been served at the Austin restaurant; however, sufficient quantities of machacado were not available for analysis. PFGE was essential in determining whether the cases constituted outbreaks and was invaluable in guiding the epidemiological investigation.
Present address: Division of Infectious Diseases, Department of
Medicine, Emory University School of Medicine, Atlanta, GA 30303.
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