Culture-independent techniques were used for the detection of pathogenic bacteria in drinking water at potentially critical control points along the production lines at a German dairy company and a Spanish dry cured ham company. Denaturing gradient gel electrophoresis (DGGE) was used to describe bacterial population shifts indicating biological instability in the drinking water samples. Autochthonous bacteria were identified by sequencing the excised DGGE DNA bands. More specifically, real-time PCR was applied to detect a number of pathogenic bacteria, i.e. Listeria monocytogenes, Mycobacterium avium subsp. paratuberculosis, Campylobacter jejuni, Enterococcus spp., Salmonella spp, Escherichia coli, and Pseudomonas aeruginosa. Due to the detection limits of the real-time PCR method, a specific protocol was established in order to meet the technical detection requirements and to avoid unwanted polymerase inhibitions. Autochthonous bacterial populations were found to be highly stable at most of the sampling points. Only one sampling point exhibited population shifts at the German dairy company. Enterococci and P. aeruginosa were detected in some water samples from these companies by molecular biology detection methods, but not by conventional culturing methods. Some opportunistic bacteria as Enterobacter sp., Acinetobacter, Sphingomonas sp. and non-pathogenic Bacillus, were also detected after DNA sequencing of DGGE bands.

Temperature is considered as the major factor determining virus inactivation in the environment. Food industries, therefore, widely apply temperature as virus inactivating parameter. This review encompasses an overview of viral inactivation and virus genome degradation data from published literature as well as a statistical analysis and the development of empirical formulae to predict virus inactivation. A total of 658 data (time to obtain a first log10 reduction) were collected from 76 published studies with 563 data on virus infectivity and 95 data on genome degradation. Linear model fitting was applied to analyse the effects of temperature, virus species, detection method (cell culture or molecular methods), matrix (simple or complex) and temperature category (<50 and ≥50°C). As expected, virus inactivation was found to be faster at temperatures ≥50°C than at temperatures <50°C, but there was also a significant temperature–matrix effect. Virus inactivation appeared to occur faster in complex than in simple matrices. In general, bacteriophages PRD1 and PhiX174 appeared to be highly persistent whatever the matrix or the temperature, which makes them useful indicators for virus inactivation studies. The virus genome was shown to be more resistant than infectious virus. Simple empirical formulas were developed that can be used to predict virus inactivation and genome degradation for untested temperatures, time points or even virus strains.

Aeromonas hydrophila, a ubiquitous inhabitant of aquatic environments, commonly expresses several cell-surface properties that may contribute to virulence. Since many aquatic microorganisms in hostile environments can withstand starvation conditions for long periods, we examined the effect of storage under nutrient poor conditions on the expression of cell-surface properties of this pathogen. Phenotypes studied were: (1) cell surface hydrophobicity and charge, and (2) the ability to bind connective-tissue proteins and lactoferrin. Our results suggest that the response of A. hydrophila to nutrient-poor conditions is regimen specific. Generally, A. hydrophila cells became more hydrophobic and significantly increased their ability to bind the iron-binding glycoprotein lactoferrin when the bacterium was stored under nutrient-poor conditions; however, under these conditions, the cells seemed to lose their ability to bind connective tissue proteins.