Induced thermotolerance under nonisothermal treatments of a heat sensitive and a resistant strain of Staphylococcus aureus in media of different pH.
OBJECTIVE
The aim was to assess the induced thermotolerance under nonisothermal treatments of two strains of Staphylococcus aureus in media of different pH.


RESULTS
Staphylococcus aureus ATCC 25923 was more heat resistant than S. aureus ATCC 13565 at any pH investigated under isothermal conditions. At pH 7.4, the D58 value of the resistant strain was approx. 30 times greater. Both strains showed a higher heat resistance at pH 4.0 than at pH 7.4. In contrast, under nonisothermal treatments (0.5-2 degrees C min(-1)), both strains were more heat resistant when treated at pH 7.4 than at pH 4.0 due to heat adaptation at the higher pH. At the slowest heating up rate tested at pH 7.4, the initially heat-sensitive strain nearly reached the thermotolerance of the heat-resistant strain.


CONCLUSIONS
The induced thermotolerance under nonisothermal treatments depended on the treatment medium pH and the microbial strain tested. The induced thermotolerance in a sensitive strain can be greater than in a heat-resistant strain, showing similar resistance under nonisothermal conditions.


CONCLUSIONS
This work shows data of interest about mechanisms of microbial resistance and adaptation to heat. Moreover, it contributes to the development of more adequate combined processes for food preservation.
Hassani
M
M
Departamento de Producción Animal y Ciencia de los Alimentos, Facultad de Veterinaria, Universidad de Zaragoza, Zaragoza, Spain.
Cebrián
G
G
Mañas
P
P
Condón
S
S
Pagán
R
R
D000222:Adaptation, Physiological; D015169:Colony Count, Microbial; D003470:Culture Media; D005519:Food Preservation / Q000379:methods; D006358:Hot Temperature; D006863:Hydrogen-Ion Concentration; D013211:Staphylococcus aureus / Q000254:growth & development* / Q000502:physiology*
D003470:Culture Media