title: Molecular sequence typing reveals genotypic diversity among Escherichia coli isolates recovered from a cantaloupe packinghouse in Northwestern Mexico.
abstract: The increase in the consumption of fresh produce has correlated with a rise in the number of reported foodborne illnesses. To identify potential risk factors associated with postharvest practices, the present study employed multilocus sequence typing (MLST) for the genotypic classification of Escherichia coli isolates recovered from three sources sampled at seven operational stages in a cantaloupe packinghouse in Northwestern Mexico. The MLST analysis results indicated that the E. coli isolates were classified into 18 different sequence types (ST), and 11 of these STs were found to be novel. ST-171 was the predominant type and was found in 19% (7/36) of the recovered isolates. Interestingly, the novel ST-827 was found to be significantly associated with isolates recovered from workers' hands, sampled during final postwash stages. Further phylogenetic analyses to examine the relatedness of the STs revealed genetic heterogeneity. Fourteen of the identified STs were assigned to known clonal groups, while the remaining four novel STs were distinct and did not cluster with any clonal group. The present study has provided the first evidence indicating that several sources from distinct operational stages in a cantaloupe packinghouse may contribute to a genotypic and phylogenetic diverse set of E. coli isolates.
  
  
  CONCLUSIONS
  Packinghouses can be considered as a potential source of microbial contamination. Using multilocus sequence typing, this study identified a genotypic and phylogenetic diverse set of Escherichia coli isolates recovered from the surfaces of cantaloupes, workers' hands and processing equipment at a cantaloupe packinghouse. A total of 61% of the sequence types identified were novel, and a distinct sequence type, ST-827, was significantly associated with worker's hands, sampled during the final postwash operational stages in the packinghouse. These findings serve as a baseline to identify potential sources of microbial contamination at distinct operational stages in a cantaloupe packinghouse.
authors.affiliation: Produce Safety and Microbiology Research Unit, Western Regional Research Center, U.S. Department of Agriculture/ARS, Albany, CA, USA.
authors.forename: B
authors.initials: B
authors.lastname: Quiñones
authors.affiliation: Department of Chemical and Biochemical Engineering, Technological Institute of Culiacan (ITC), Culiacan, Sinaloa, Mexico.
authors.forename: J P
authors.initials: JP
authors.lastname: Campos Sauceda
authors.affiliation: Produce Safety and Microbiology Research Unit, Western Regional Research Center, U.S. Department of Agriculture/ARS, Albany, CA, USA.
authors.forename: B G
authors.initials: BG
authors.lastname: Lee
authors.affiliation: Produce Safety and Microbiology Research Unit, Western Regional Research Center, U.S. Department of Agriculture/ARS, Albany, CA, USA.
authors.forename: J C
authors.initials: JC
authors.lastname: Yambao
authors.affiliation: Food Safety National Research Laboratory (LANIIA), Research Center in Food & Development (CIAD), Culiacan, Sinaloa, Mexico.
authors.forename: C
authors.initials: C
authors.lastname: Cháidez Quiroz
mesh_terms: D015373:Bacterial Typing Techniques; D028463:Cucumis melo / Q000382:microbiology*; D004926:Escherichia coli / Q000235:genetics* / Q000302:isolation & purification; D005506:Food Contamination; D018857:Food Packaging; D014644:Genetic Variation; D005838:Genotype; D006801:Humans; D008800:Mexico; D058885:Multilocus Sequence Typing; D010802:Phylogeny
keywords: 
  Escherichia coli
  ; cantaloupe; diversity; food safety; genotyping; postharvest