Tags

Type your tag names separated by a space and hit enter

Modeling the effect of inoculum size and acid adaptation on growth/no growth interface of Escherichia coli O157:H7.
Int J Food Microbiol. 2007 Dec 15; 120(3):237-49.IJ

Abstract

The objective of this study was to model with logistic regression the growth/no growth interface of different initial inoculation levels (10(1), 10(3) and 10(5) CFU/ml; study 1), or nonadapted vs acid-adapted (study 2) Escherichia coli O157:H7 as influenced by pH, NaCl concentration and incubation temperature. Study 1 was conducted with a mixture of four E. coli O157:H7 strains grown (35 degrees C, 24 h) in tryptic soy broth (TSB). Study 2 was conducted with the same mixture of four E. coli O157:H7 strains grown (35 degrees C, 24 h) in glucose-free TSB with 1% added glucose (final pH 4.83), or in diluted lactic acid meat decontamination runoff fluids (washings; final pH 4.92), or nonadapted cultures prepared in glucose-free TSB (final pH 6.45), or in water washings (final pH 6.87). Parameters included incubation temperature (10-35 degrees C), pH (3.52-7.32), and NaCl concentration (0-10% w/v). Growth responses were evaluated for 60 days turbidimetrically (610 nm) every 5 days in 160 (study 1) and 360 (study 2) combinations in quadruplicate samples, with a microplate reader. The lower the initial inoculum the higher were the minimum pH and a(w) values permitting growth. Differences in the pH and a(w) growth limits among inoculum concentrations increased at 15 and 10 degrees C. Acid-adapted cultures were able to grow at lower pH than nonadapted cultures, while at temperatures below 25 degrees C, growth initiation of nonadapted cultures stopped at higher a(w) compared to acid-adapted cultures for the whole pH range of 3.52 to 7.32. A comparison with available data indicated that our model for acid-adapted E. coli O157:H7 in different environments may provide representative growth probabilities covering both nonadapted and stress-adapted contaminants.

Links

Publisher Full Text

Authors+Show Affiliations

Skandamis PN
Department of Animal Sciences, Colorado State University, Fort Collins, Colorado 80523-1171, USA.
Stopforth JD
No affiliation info available
Kendall PA
No affiliation info available
Belk KE
No affiliation info available
Scanga JA
No affiliation info available
Smith GC
No affiliation info available
Sofos JN
No affiliation info available

MeSH

Adaptation, PhysiologicalColony Count, MicrobialEscherichia coli O157Food ContaminationFood HandlingFood MicrobiologyHydrogen-Ion ConcentrationKineticsLogistic ModelsModels, BiologicalTemperatureTime FactorsWater

Pub Type(s)

Journal Article
Research Support, U.S. Gov't, Non-P.H.S.

Language

eng

PubMed ID

17961778

Citation

Skandamis, P N., et al. "Modeling the Effect of Inoculum Size and Acid Adaptation On Growth/no Growth Interface of Escherichia Coli O157:H7." International Journal of Food Microbiology, vol. 120, no. 3, 2007, pp. 237-49.
Skandamis PN, Stopforth JD, Kendall PA, et al. Modeling the effect of inoculum size and acid adaptation on growth/no growth interface of Escherichia coli O157:H7. Int J Food Microbiol. 2007;120(3):237-49.
Skandamis, P. N., Stopforth, J. D., Kendall, P. A., Belk, K. E., Scanga, J. A., Smith, G. C., & Sofos, J. N. (2007). Modeling the effect of inoculum size and acid adaptation on growth/no growth interface of Escherichia coli O157:H7. International Journal of Food Microbiology, 120(3), 237-49.
Skandamis PN, et al. Modeling the Effect of Inoculum Size and Acid Adaptation On Growth/no Growth Interface of Escherichia Coli O157:H7. Int J Food Microbiol. 2007 Dec 15;120(3):237-49. PubMed PMID: 17961778.
* Article titles in AMA citation format should be in sentence-case
TY - JOUR T1 - Modeling the effect of inoculum size and acid adaptation on growth/no growth interface of Escherichia coli O157:H7. AU - Skandamis,P N, AU - Stopforth,J D, AU - Kendall,P A, AU - Belk,K E, AU - Scanga,J A, AU - Smith,G C, AU - Sofos,J N, Y1 - 2007/09/01/ PY - 2007/07/06/received PY - 2007/08/28/accepted PY - 2007/10/27/pubmed PY - 2008/2/12/medline PY - 2007/10/27/entrez SP - 237 EP - 49 JF - International journal of food microbiology JO - Int J Food Microbiol VL - 120 IS - 3 N2 - The objective of this study was to model with logistic regression the growth/no growth interface of different initial inoculation levels (10(1), 10(3) and 10(5) CFU/ml; study 1), or nonadapted vs acid-adapted (study 2) Escherichia coli O157:H7 as influenced by pH, NaCl concentration and incubation temperature. Study 1 was conducted with a mixture of four E. coli O157:H7 strains grown (35 degrees C, 24 h) in tryptic soy broth (TSB). Study 2 was conducted with the same mixture of four E. coli O157:H7 strains grown (35 degrees C, 24 h) in glucose-free TSB with 1% added glucose (final pH 4.83), or in diluted lactic acid meat decontamination runoff fluids (washings; final pH 4.92), or nonadapted cultures prepared in glucose-free TSB (final pH 6.45), or in water washings (final pH 6.87). Parameters included incubation temperature (10-35 degrees C), pH (3.52-7.32), and NaCl concentration (0-10% w/v). Growth responses were evaluated for 60 days turbidimetrically (610 nm) every 5 days in 160 (study 1) and 360 (study 2) combinations in quadruplicate samples, with a microplate reader. The lower the initial inoculum the higher were the minimum pH and a(w) values permitting growth. Differences in the pH and a(w) growth limits among inoculum concentrations increased at 15 and 10 degrees C. Acid-adapted cultures were able to grow at lower pH than nonadapted cultures, while at temperatures below 25 degrees C, growth initiation of nonadapted cultures stopped at higher a(w) compared to acid-adapted cultures for the whole pH range of 3.52 to 7.32. A comparison with available data indicated that our model for acid-adapted E. coli O157:H7 in different environments may provide representative growth probabilities covering both nonadapted and stress-adapted contaminants. SN - 0168-1605 UR - https://www.unboundmedicine.com/medline/citation/17961778/Modeling_the_effect_of_inoculum_size_and_acid_adaptation_on_growth/no_growth_interface_of_Escherichia_coli_O157:H7_ L2 - https://linkinghub.elsevier.com/retrieve/pii/S0168-1605(07)00461-8 DB - PRIME DP - Unbound Medicine ER -