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Salmonella contamination during production of domestic and imported canaloupe
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In this study, 8 cantaloupe farms and packing sheds from the United States (U.S.) and Mexico were sampled to evaluate cantaloupe contamination with Salmonella and Escherichia coli during production and processing. Samples collected from external surfaces of cantaloupes, water and environments of packing sheds of cantaloupe farms were examined for the presence of Salmonella and E. coli. Thirty-one samples (n = 1735) tested positive for Salmonella. Fifteen Salmonella serotypes were isolated from samples collected in the U.S., and 9 from samples collected in Mexico. Two serotypes (S. Poona and S. Oranienburg) that have been associated with 3 large Salmonella outbreaks in the U.S. and Canada linked to the consumption of contaminated cantaloupe were found in water samples collected at 4 farms (3 from the U.S.). Susceptibility of Salmonella isolates to 10 antimicrobials was evaluated by disk diffusion. The majority of the isolates from the U.S. and Mexico were susceptible to all antimicrobials tested. Eight isolates from the U.S. demonstrated an intermediate susceptibility to streptomycin and only 2 isolates were resistant to the same antimicrobial. From Mexico 4 isolates showed an intermediate susceptibility to streptomycin and 1 isolate was resistant to nalidixic acid and streptomycin. Repetitive sequence-based polymerase chain reaction (REP-PCR) analysis of Salmonella isolates helped to trace potential sources of Salmonella contamination in source water and in subsequent water samples obtained after the filtration systems from U.S. and Mexican cantaloupe farms. In this study, the efficacy of decontamination treatments in reducing rifampicin resistant S. Typhimurium and E. coli O157:H7 on inoculated cantaloupe pieces were also investigated. Melon pieces were treated with 200-ppm chlorine or 2% lactic acid solutions or a combination of both at 25 and 35⁰ C, and survival populations were determined. All treatments significantly reduced levels of both marker organisms on inoculated melon surfaces compared to the initial inoculation levels (3.1 and 2.9 Log₁₀ CFU/cm² respectively); however, additional testing is required to determine the actual benefit of one treatment over the other.
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Includes bibliographical references (leaves 73-93).
Issued also on microfiche from Lange Micrographics.
Uribe, Imelda Mercado (2002). Salmonella contamination during production of domestic and imported canaloupe. Master's thesis, Texas A&M University. Available electronically from
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