Culturability, injury and morphological dynamics of thermophilic Campylobacter spp. within a laboratory-based aquatic model system

Abstract

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 signi®cantly greater at the higher temperature (20°C) with a rapid transition of the dominant sub-populations from non-stressed to dead cells occurred within 3 days. At 10°C 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. Signi®cant differences (P < 0á001) were identi®ed 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 identi®ed. The endpoints of morphological transition were temperature-independent and isolate-speci®c 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. Signi®cance and Impact of the Study: VBNC cells form the most persistent, viable, potentially pathogenic sub-population of Campylobacter populations exposed to aquatic stress conditions.

Quo vadis? — MonitoringCampylobacterin Germany

“…Freezing is considered to be a physical decontamination process, leading to a 2 log reduction of Campylobacter concentration after 3 weeks of freezing [3]. Third, stressed and nonculturable cells of Campylobacter do not grow in vitro on selective medium and are not accessible for common detection methods [24]. Under meat storage conditions (4 °C), the number of culturable Campylobacter on chicken skin was reduced by 2 log within the first 2-5 days depending on the strain tested [25].…”

Human campylobacteriosis: a challenge for the veterinary profession

“…64 Similarly, biofilms are reported to facilitate the survival of C jejuni in broiler houses. 65 Some researchers postulate that campylobacters can survive in water in a viable but noncultivable form 66,67 ; however, the role of this dormant stage in the Campylobacter life cycle is controversial.…”

Survival mechanisms and culturability of Campylobacter jejuni under stress conditions

“…Aquatic environments are reservoirs for C. jejuni (Bolton et al 1982;Thomas et al 1999;Levin 2007) and contaminated drinking water has been implicated in several C. jejuni outbreaks (Thomas et al 2002). Wastewater treatment effluent, animal feces and agricultural activities contribute to C. jejuni contamination of surface waters.…”