title: Survival and colonization of Escherichia coli O157:H7 on spinach leaves as affected by inoculum level and carrier, temperature and relative humidity.
abstract: OBJECTIVE
  To determine survival and colonization of Escherichia coli O157:H7 on spinach leaves as affected by inoculum level and carrier, temperature and relative humidity (r.h.).
  
  
  RESULTS
  Spinach leaves were inoculated with suspensions of E. coli O157:H7 in distilled water (DW) and 0.1% peptone water (PW) and incubated at 4, 12 and 25°C and 43, 85 and 100% r.h. The number of E. coli O157:H7 on leaves (5.6 or 1.9 log CFU per leaf) inoculated using DW as a carrier medium increased significantly at 25°C and 100% r.h. within 120 h but remained constant or decreased significantly under other test conditions. E. coli O157:H7 on leaves (5.4 log CFU per leaf) inoculated using PW as a carrier increased significantly within 72 and 24 h, respectively, at 12 or 25°C and 100% r.h.; counts using a low inoculum (2.2 log CFU per leaf) increased significantly within 24 h at 25°C.
  
  
  CONCLUSIONS
  Escherichia coli O157:H7 can colonize on spinach leaves at 12 or 25°C in a 100% r.h. environment. Organic matter in the inoculum carrier may provide protection and nutrients which enhance survival and colonization.
  
  
  CONCLUSIONS
  Colonization of E. coli O157:H7 on spinach leaves as affected by organic matter in the inoculum, temperature and r.h. was determined. These observations will be useful when developing strategies to prevent growth of E. coli O157:H7 on pre- and postharvest spinach.
authors: Graduate School of Life Sciences and Biotechnology, Korea University, Seoul, South Korea.
authors: S
authors: S
authors: Choi
authors: J
authors: J
authors: Bang
authors: H
authors: H
authors: Kim
authors: L R
authors: LR
authors: Beuchat
authors: J-H
authors: JH
authors: Ryu
mesh_terms: D015169:Colony Count, Microbial; D003257:Consumer Product Safety; D019453:Escherichia coli O157 / Q000254:growth & development*; D005506:Food Contamination / Q000032:analysis; D005516:Food Microbiology; D006813:Humidity; D018515:Plant Leaves / Q000382:microbiology; D018724:Spinacia oleracea / Q000382:microbiology*; D013696:Temperature