title: Comparison of sample preparation methods for the recovery of foodborne pathogens from fresh produce.
abstract: Sample preparation methods (pummeling, pulsifying, sonication, and shaking by hand) were compared for achieving maximum recovery of foodborne pathogens from iceberg lettuce, perilla leaves, cucumber, green pepper, and cherry tomato. Antimicrobial and dehydration effects also were examined  to investigate causes of poor recovery of pathogens. Each produce type was inoculated with Escherichia coli O157:H7, Salmonella Typhimurium, Listeria monocytogenes, Staphylococcus aureus, and Bacillus cereus at 6.0 log CFU/cm(2), and samples were prepared  using the four methods. Bacterial populations recovered from the five types of produce were significantly different (P < 0.05) according to sample preparation methods and produce type. The bacterial populations recovered from pummeled and pulsified samples were higher (P <  0.05) than those recovered from sonicated and hand-shaken samples, except for cherry tomato. The number of bacteria recovered from produce was reduced (P < 0.05) from that of the inoculum by 0.16 to 2.69 log CFU/cm(2). Although extracts of iceberg lettuce, perilla leaves,  cucumber, and green pepper had no antimicrobial activity, the populations of E. coli O157:H7, Salmonella Typhimurium, B. cereus, and L. monocytogenes in cherry tomato extract were slightly reduced after these treatments (P < 0.05). The pathogen populations  on perilla leaves and cherry tomatoes decreased by >2 log CFU/cm(2) after exposure to 40% relative humidity for 1 h. No reduction was observed when the five pathogens were exposed to 90% relative humidity. These data suggest that pummeling and pulsifying are optimal sample preparation  methods for detection of microorganisms. Acidic produce such as cherry tomato should be treated with a method that does not cause sample breakdown so that acid stress on the bacteria can be minimized. Dehydration stress also affects recovery of pathogens from produce.
authors.affiliation: Microbial Safety Division, Department of Agri-Food Safety, National Academy of Agricultural Science, Rural Development Administration, Suwon 441-707, South Korea.
authors.forename: Se-Ri
authors.initials: SR
authors.lastname: Kim
authors.forename: Yohan
authors.initials: Y
authors.lastname: Yoon
authors.forename: Won-Il
authors.initials: WI
authors.lastname: Kim
authors.forename: Kyeong-Hun
authors.initials: KH
authors.lastname: Park
authors.forename: Hye-Jeong
authors.initials: HJ
authors.lastname: Yun
authors.forename: Duck Hwa
authors.initials: DH
authors.lastname: Chung
authors.forename: Jong Chul
authors.initials: JC
authors.lastname: Yun
authors.forename: Kyoung Yul
authors.initials: KY
authors.lastname: Ryu
mesh_terms: D001409:Bacillus cereus / Q000302:isolation & purification; D002212:Capsicum / Q000382:microbiology; D015169:Colony Count, Microbial; D018553:Cucumis sativus / Q000382:microbiology; D019453:Escherichia coli O157 / Q000302:isolation & purification; D005506:Food Contamination / Q000032:analysis* / Q000517:prevention & control; D005511:Food Handling / Q000379:methods*; D005516:Food Microbiology; D006801:Humans; D018545:Lactuca / Q000382:microbiology; D008089:Listeria monocytogenes / Q000302:isolation & purification; D018551:Solanum lycopersicum / Q000382:microbiology; D012486:Salmonella typhimurium / Q000302:isolation & purification; D013211:Staphylococcus aureus / Q000302:isolation & purification; D014675:Vegetables / Q000382:microbiology*