Short communicationInvestigating the correlation of constitutive proteins with the growth limits of Salmonella enterica isolates from feeds in response to temperature, pH, formic and lactic acid

- Enhanced antimicrobial activity of lactic and formic acids at lower temperatures is reported.
- At 20 and 25 °C lactic acid seemed to be more effective than formic acid.
- A rather limited amount of uniquely expressed proteins has been identified.

The aim of this study was to assess growth/no growth interface of several Salmonella enterica strains isolated from contaminated feeding stuffs at various pH values and temperatures, in the presence of lactic or formic acid and to analyze the proteomic map of the most interesting ones. Addition of lactic acid resulted in an increase of the minimum pH value required for growth with decreasing temperature; addition of formic acid resulted in no detectable growth at 10 and 15 °C, the latter with the exception of strains 23 and 15100, while only minor differences were exhibited at 20 and 25 °C. The complexity of the mechanisms by which organic acids affect microbial growth has been highlighted, and factors such as type and concentration of the acid, pH, temperature as well as specific attributes of the microbial strains, should be taken into consideration. A large number of protein spots, with no significant variation, have been observed, representing the housekeeping proteome of the species and on the other hand, a rather limited amount of uniquely expressed proteins has been identified, representing differences that require further study for their assignment to serovar/strain variability or possess a role in pathogenesis.