title: The influence of the microbial quality of wastewater, lettuce cultivars and enumeration technique when estimating the microbial contamination of wastewater-irrigated lettuce.
abstract: This study investigated the volume of wastewater retained on the surface of three different varieties of lettuce, Iceberg, Cos, and Oak leaf, following submersion in wastewater of different microbial qualities (10, 102, 103, and 104E. coli MPN/100 mL) as a surrogate method for estimation of contamination of spray-irrigated lettuce. Uniquely, Escherichia coli was enumerated, after submersion, on both the outer and inner leaves and in a composite sample of lettuce. E. coli were enumerated using two techniques. Firstly, from samples of leaves - the direct method. Secondly, using an indirect method, where the E. coli concentrations were estimated from the volume of wastewater retained by the lettuce and the E. coli concentration of the wastewater. The results showed that different varieties of lettuce retained significantly different volumes of wastewater (p < 0.01). No statistical differences (p > 0.01) were detected between E. coli counts obtained from different parts of lettuce, nor between the direct and indirect enumeration methods. Statistically significant linear relationships were derived relating the E. coli concentration of the wastewater in which the lettuces were submerged to the subsequent E. coli count on each variety the lettuce.
authors.affiliation: Health and Environment Group, School of the Environment, Flinders University, GPO Box 2100, Adelaide 5001, South Australia, Australia E-mail: patrick.makkaew@flinders.edu.au.
authors.forename: P
authors.initials: P
authors.lastname: Makkaew
authors.affiliation: Department of Health and Ageing, OzFoodNet, Communicable Disease Control Branch, P.O. Box 6, Rundle Mall, Adelaide 5000, South Australia, Australia.
authors.forename: M
authors.initials: M
authors.lastname: Miller
authors.affiliation: Health and Environment Group, School of the Environment, Flinders University, GPO Box 2100, Adelaide 5001, South Australia, Australia E-mail: patrick.makkaew@flinders.edu.au.
authors.forename: N J
authors.initials: NJ
authors.lastname: Cromar
authors.affiliation: Health and Environment Group, School of the Environment, Flinders University, GPO Box 2100, Adelaide 5001, South Australia, Australia E-mail: patrick.makkaew@flinders.edu.au.
authors.forename: H J
authors.initials: HJ
authors.lastname: Fallowfield
mesh_terms: D015169:Colony Count, Microbial; D004926:Escherichia coli / Q000302:isolation & purification*; D005516:Food Microbiology / Q000379:methods*; D018545:Lactuca / Q000235:genetics / Q000254:growth & development / Q000382:microbiology*; D018515:Plant Leaves / Q000382:microbiology; D062065:Wastewater / Q000382:microbiology*
chemical_list: D062065:Wastewater