Aims: To study the survival processes of thermophilic Campylobacter spp. within a modelled aquatic system and particularly the involvement and survival potential of viable but nonculturable forms.Methods and Results: The survival and morphological characteristics of populations of thermophilic Campylobacter species exposed to simulated aquatic conditions were examined using a combination of cultural and microscopic techniques. Populations underwent progressive decay when exposed to simulated aquatic conditions. The rates of population decay were observed to be significantly greater at the higher temperature (20degreesC) with a rapid transition of the dominant sub-populations from non-stressed to dead cells occurred within 3 days. At 10degreesC the rate of culturability loss was much reduced with substantial development (approx. 80% of total population) of viable but non-culturable (VBNC) populations by all species within 3 days, declining to represent approximately 5-25% of the total population at day 60. Significant differences (P < 0.001) were identified between decay rates as a consequence of different species, sub-populations and temperature but not between sub-populations of different species. Morphological variants including spiral, elongated spirals and rods, short rods and coccoid forms were identified. The endpoints of morphological transition were temperature-independent and isolate-specific yet the rate of morphological transition was directly related to temperature and approximately equivalent between species.Conclusion: The VBNC state is a transitory stage in the degeneration of Campylobacter population within the aquatic environments simulated during this study.Significance and Impact of the Study: VBNC cells form the most persistent, viable, potentially pathogenic sub-population of Campylobacter populations exposed to aquatic stress conditions.

Summary The survival and growth of Listeria monocytogenes and L. innocua strains inoculated onto cooked sweet corn and fresh bean sprouts packed individually, and as components of a combination product, were examined at refrigeration and mild abuse temperatures. Growth rates were both temperature and vegetable dependent. Maximal growth rates (1.14 ± 0.1log CFU/day) were identified on cooked sweet corn at 12 °C. The inclusion of cooked sweet corn did not significantly increase ( P > 0.05) the growth rate or final Listeria population density of bean sprouts stored at 8 °C and 12 °C. The sensory quality of bean sprouts was relatively temperature independent for the initial 48 h of storage, but was maximized (4 days shelf life) at 3 °C. Acidification of sweet corn to pH 5, particularly with citric acid, slowed Listeria growth and could be an additional hurdle to supplement temperature in maintaining the safety of minimally processed vegetable combination products.

Summary Demand for fresh, convenient, minimally processed vegetables has led to an increase in the quantity and variety of products available to the consumer. Modified atmosphere packaging, in combination with refrigeration, is increasingly being employed as a mild preservation technique to ensure quality and storage‐life. The fresh nature of these products, together with the mild processing techniques and subsequent storage conditions, have presented indigenous and pathogenic microorganisms with new ecosystems and potential infection vehicles; a number of outbreaks of foodborne disease being attributed to their consumption. Psychrotrophic pathogens and pathogens which are capable of maintaining an infectious potential under mild preservation regimes are of particular concern; Listeria monocytogenes , Aeromonas hydrophila and Clostridium botulinum being amongst the most notable. This review describes the processing, packaging and storage procedures involved in the production of minimally processed vegetables, and details their impact upon the survival and growth of associated pathogens. Gaps in our current understanding of the consequences of this novel technology for microbiological safety are highlighted.

Members of the genus Campylobacter have established themselves as the most common human gastro-enteric pathogens throughout much of the developed world. The ubiquitous distribution of Campylobacter spp. in animal reservoirs and food products derived thereof make such vehicles primary risk factors in contracting campylobacteriosis. The contamination rates, identification of common pathogenic serotypes and extended survival of Campylobacter in surface waters illustrates the potential, but yet to be quantified, campylobacteriosis risk associated with untreated water. The existence and potential pathogenicity of viable but nonculturable forms of Campylobacter remains a contentious subject. Furthermore. the role of such forms in the epidemiology of Campylobacter related disease and their involvement in the large number of waterborne gastroenteritis outbreaks from which a disease agent cannot be isolated remains to be fully clarified. This article presents a survey of current perspectives with regard to the survival and epidemiology of Campylobacter spp. in natural water systems.

Campylobacter jejuni strains demonstrate a variety of growth phase-linked distinct morphological forms when grown in liquid culture. The typical spiral form of the organism, evident during logarithmic phase, undergoes elongation during stationary phase before becoming coccoid via the formation of membrane blebs and budded forms in decline phase. Cellular elongation and coccoid formation occurred despite the inhibition of protein synthesis and without a detectable change in the protein components of the inner and outer cell membranes.

A study of basal medal identified Campylobacter enrichment broth, with (CEB+) and without (CEB) antibiotic supplement, as a suitable medium for the detection and enumeration of Campylobacter jejuni, C. coli and C. lari within aqueous samples via conductance methodology. Despite apparent differences in conductivity profiles between species in the presence of antibiotics, no significant differences (P < 0.05) were detected between detection times for each species tested. CEB+ was successfully employed within a combined enrichment and conductance protocol to the detection of C. jejuni from river water at a concentration of 1 CFU ml-1 from 83% of samples in under 39 h and thus demonstrated an improvement over an applied conventional membrane filtration technique.

Batch microcosms containing various water types (de-ionized and river water with or without sediment), incubated at a range of temperatures (5-37 degrees C), were used to facilitate a comparative evaluation of the significance of such variables and their interactions upon the collective and individual survival of four species of thermophilic Campylobacter. All variables significantly influenced (P < = 0.031) population decay rates. Minimal decay for the group was identified at low temperatures (5 degrees C) in river water, i.e. nutrient-containing microcosms. Collective decay rates within river water microcosms were significantly decreased (P = 0.03) from those observed in de-ionized water, particularly at environmental temperatures (5 and 15 degrees C). However, the increased nutrient levels observed in sediment-containing microcosms did not significantly (P = 0.41) reduce population decay rates. Overall, Camp. jejuni populations demonstrated the most resilience to the environmental stressors evaluated, with the exception of 15 degrees C where Camp. lari was the most persistent. Campylobacter coli and Camp. upsaliensis demonstrated comparable survival characteristics but were less resilient than Camp. jejuni and Camp. lari. These observations identify the suitability of water systems as a reservoir and medium for Campylobacter infection, and potentially identifies Camp. jejuni and Camp. lari as the main protagonists of water-mediated campylobacteriosis.