Effect of the pre-treatments for milk samples filtration on direct viable cell counts.
Escherichia coli O25:H-42 was selected to study the effect of pre-treatments on the enumeration of direct viable cells from milk samples. Before and after inducing cell elongation by cellular division inhibitors, three pre-treatments for milk-filtration were used. One involved a pre-treatment with trypsin (1.5 min at 50 degrees C), addition of hot Triton X-100 after heating and filter rinses with phosphate saline buffer. The other two involved pre-treatment with trypsin and Triton X-100 (10 min at 50 degrees C), filter rinses with hot Triton X-100 and organic solvents. Pre-treatments applied after inducing cell elongation had an effect on cell recovery from milk samples depending on the pre-treatment used. The most suitable, on the basis of the number and percentage of enlarged cells obtained was the first described. The others selectively affected recovery of elongated cells. Pre-treatments applied before inducing the cell elongation, negatively affected viability with enumeration in milk samples being significantly (P < 0.001) lower than those found in controls. However, the negative effects of first pre-treatment on viability was lower than that produced by the pre-treatments involving organic solvents.
Fernández-Astorga
A
A
Departamento Inmunología Microbiología y Parasitología, Universidad del País Vasco, Facultad de Farmacia, Vitoria, Spain.
Hijarrubia
M J
MJ
Lázaro
B
B
Barcina
I
I
D000818:Animals; D015169:Colony Count, Microbial; D004926:Escherichia coli / Q000187:drug effects / Q000254:growth & development; D005374:Filtration; D006358:Hot Temperature; D008892:Milk / Q000382:microbiology*; D017830:Octoxynol; D014357:Trypsin
D017830:Octoxynol; D014357:Trypsin