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Investigation of the Physiological Mechanisms for the Adaptation of Campylobacters to Stress Injury. - FS1526

In response to adverse environmental conditions Campylobacters produce non-culturable forms which appear to remain viable and, therefore, potentially pathogenic to man. This phemomena complicates estimation of the bacterial load in contaminated foods and identification of critical control points in food processing is difficult. Recent results indicate that non-culturability and infectivity are unrelated to either existing biochemical indicators of viability or morphological changes but the potential pathogenicity of sublethally injured campylobacters cannot be excluded. Therefore the development of alternative indicators, of infectious but non-culturable organisms, is necessary. The responses of campylobacters to adverse condi tions can be envisaged as a progressive sequenec of events leading from the characteristic spiral, pathogenic bacterium via a variety of intermediate forms to bacterial death. Such a progression would be accompanied bgy a gradual loss of those metabolic processes associated with maintenance of bacterial viability , and in consequence loss of culturability. Presumably early in this sequence these events would be reversible. However, afer some, as yet to be identified , point non-recoverability becomes irreversible. All stages in the sequence should be definable by markers expressed by the organism reflecting its physiological state. The main objective of this proposal is to identify novel markers of the physiological, biochemical and morphological changes which occur during this presumed sequence of events. These markers will then be used to develop appropriate techniques for the detection of non-culturable but infectious campylobacters in foods.
1) To develop the methodologies to expose campylobacters to defined adverse environmental conditions and to cause sub-lethal injury in order to establish the endpoint at which campylobacters are recoverable using optimal in vitro and in vivo culture techniques. 2) To establish the sequence of events definable on the basis of changes in bacterial physiology, biochemistry and morphology, in the progression from "infectious and culturable" organisms to "infectious but non-culturable" organisms. 3) To investigate the genetic basis of the response of C.jejuni to sub-lethal injury using deletion mutants of environmental response regulator genes and other genes potentially involved in survival. 4) To identify and characterise novel proteins expressed during the progression of events described in objective 3 as markers of infectious but non-culturable forms of camplylobacters. 5) Development and evaluation of immunological reagents directed against protein markers of sub-lethal injury identified in objective 4.
Time-Scale and Cost
From: 1995

To: 1998

Cost: £146,202
Contractor / Funded Organisations
Veterinary Laboratories Agency