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Modelling the interactions between Pseudomonas putida and Escherichia coli O157:H7 in fish‐burgers: use of the lag‐exponential model and of a combined interaction index
Author(s) -
Speranza B.,
Bevilacqua A.,
Mastromatteo M.,
Sinigaglia M.,
Corbo M.R.
Publication year - 2010
Publication title -
journal of applied microbiology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.889
H-Index - 156
eISSN - 1365-2672
pISSN - 1364-5072
DOI - 10.1111/j.1365-2672.2010.04692.x
Subject(s) - pseudomonas putida , escherichia coli , exponential growth , lag , pseudomonas aeruginosa , biology , exponential function , microbiology and biotechnology , food science , bacteria , mathematics , biochemistry , mathematical analysis , computer network , genetics , computer science , gene
Aims: The objective of the current study was to examine the interactions between Pseudomonas putida and Escherichia coli O157:H7 in coculture studies on fish‐burgers packed in air and under different modified atmospheres (30 : 40 : 30 O 2 : CO 2 : N 2 , 5 : 95 O 2 : CO 2 and 50 : 50 O 2 : CO 2 ), throughout the storage at 8°C. Methods and Results: The lag‐exponential model was applied to describe the microbial growth. To give a quantitative measure of the occurring microbial interactions, two simple parameters were developed: the combined interaction index (CII) and the partial interaction index (PII). Under air, the interaction was significant ( P < 0·05) only within the exponential growth phase (CII, 1·72), whereas under the modified atmospheres, the interactions were highly significant ( P < 0·001) and occurred both in the exponential and in the stationary phase (CII ranged from 0·33 to 1·18). PII values for E. coli O157:H7 were lower than those calculated for Ps. putida . Conclusions: The interactions occurring into the system affected both E. coli O157:H7 and pseudomonads subpopulations. The packaging atmosphere resulted in a key element. Significance and Impact of the Study: The article provides some useful information on the interactions occurring between E. coli O157:H7 and Ps. putida on fish‐burgers. The proposed index describes successfully the competitive growth of both micro‐organisms, giving also a quantitative measure of a qualitative phenomenon.