Mechanisms behind tailing in the pressure inactivation curve of a clinical isolate of Escherichia coli O157:H7.
The tailing in pressure inactivation curve of clinically isolated Escherichia coli O157:H7 was investigated. A typical tailing was observed after the treatment period for 30min when 10(7) CFU/ml of the cell suspension was subjected to pressure treatment at 300MPa and 25 degrees Celsius. There was no effect on the tailing profiles by the addition of pressure-killed cells and released cellular components. When cells survived at a tail portion were re-propagated (tail-culture) and subjected to second pressure treatment, the cells of the tail-culture exhibited eminently higher barotolerance compared to those of the original-culture, suggesting that the presence of genetically pressure-resistant subpopulation was responsible for the tailing. The cytoplasmic membrane of the tail-culture cells had higher stability to a pressure treatment at 100MPa for 10min than that of the original-culture, which was evidenced by lower permeability to ethidium bromide. The addition of non-ionic surfactants including 0.5microl/ml polyoxyethylene p-t-octylphenyl ester (Triton X-100) and 0.53mg/ml lauric sugar ester dramatically reduced the level of tailing and made the inactivation curve linear.
Noma
Seiji
S
Kyushu University Venture Business Laboratory, 6-10-1, Hakozaki, Higashi-ku, Fukuoka City, 812-8581, Japan.
Kajiyama
Daiki
D
Igura
Noriyuki
N
Shimoda
Mitsuya
M
Hayakawa
Isao
I
D015169:Colony Count, Microbial; D045703:Emulsifying Agents / Q000494:pharmacology*; D019453:Escherichia coli O157 / Q000187:drug effects / Q000254:growth & development*; D006874:Hydrostatic Pressure; D007700:Kinetics; D007850:Lauric Acids / Q000494:pharmacology; D008954:Models, Biological; D017830:Octoxynol / Q000494:pharmacology; D013501:Surface-Active Agents / Q000494:pharmacology*; D013696:Temperature; D013997:Time Factors
D045703:Emulsifying Agents; D007850:Lauric Acids; D013501:Surface-Active Agents; D017830:Octoxynol