Submitted to: Meeting Abstract
Publication Type: Abstract Only
Publication Acceptance Date: 2/21/2006
Publication Date: 8/13/2006
Citation: Orozco, L.R., Tamplin, M.L., Fratamico, P.M., Call, J.E., Luchansky, J.B., Escartin, E. 2006. Potential sources of salmonella contamination on tomatoes grown in hydroponic greenhouses. [Abstract] International Association for Food Protection's Annual Meeting P4-11. pg. 158. Interpretive Summary:
Technical Abstract: A study was conducted to determine the microbiological quality of tomatoes grown in hydroponic greenhouses in Mexico over the period of 2002 to 2004. The farm consisted of 13 harvest greenhouses, one nursery greenhouse, and a packaging shed. Contamination of tomatoes with enteric bacteria occurred during normal working conditions, and also during two natural and unexpected events: 1) a flood in 2003 that introduced runoff into four greenhouses, and 2) the entry of wild animals into five greenhouses in 2004. Salmonella and Escherichia coli were found on tomatoes, working and personal shoes, vehicle wheels, sponges, greenhouse soil, and feces from livestock, wild, and domestic animals. The most frequently isolated Salmonella serotypes were Montevideo (51.6%), Newport (6.8%), Connecticut (5.2%), and strains of serogroup F (13.2%). At least one strain from each positive sample was selected (n = 250) for analysis by pulsed-field gel electrophoresis (PFGE) to elucidate potential sources of contamination. PFGE was performed employing a CDC protocol for Salmonella using XbaI and AvrII restriction enzymes. Gel images were analyzed and dendrograms were constructed using BioNumerics software. AvrII detected differences in strains belonging to S. Montevideo and F serogroups that were not distinguished by XbaI. XbaI and AvrII distinguished 8 and 10 pulsotypes for Montevideo, and 5 and 7 for serogroup F, respectively. Pulsotypes C (XbaI) and b (AvrII) from S. Montevideo were more frequently isolated from tomatoes, possum feces, puddles, and soil. Pulsotypes I (XbaI) and iii (AvrII) from serogroup F were isolated from tomatoes, cow feces and personnel shoes. All S. Newport and S. Connecticut pulsotypes were associated with greenhouse floods and goat feces. Detection of sources of contamination provides baseline information for implementing effective control measures to prevent the presence of enteropathogens in produce grown in greenhouses.