PATHOGENESIS MICROBIAL Microbial Pathogenesis 43 (2007) 120–125 Short communication Environmental stress factors affecting survival and virulence of Campylobacter jejuni Roberta Rubesa Mihaljevic a , Maja Sikic b , Anja Klancnik b , Gordana Brumini c , Sonja Smole Mozina b , Maja Abram a,Ã a Department of Microbiology, Medical Faculty, University of Rijeka, Brace Branchetta 20, HR-51000 Rijeka, Croatia b Department of Food Science and Technology, Biotechnical Faculty, University of Ljubljana, Jamnikarjeva 101, SI-1111 Ljubljana, Slovenia c Department of Medical Informatics, Medical Faculty, University of Rijeka, Brace Branchetta 20, HR-51000 Rijeka, Croatia Received 1 August 2006; received in revised form 12 December 2006; accepted 6 March 2007 Available online 19 April 2007 Abstract Enteric pathogens are constantly exposed to stressful conditions in their natural habitat in the host and even more in the extra-host environment, including food processing. The aim of this study was to evaluate the effect of selected environmental stress factors: temperature shift, starvation and atmospheric oxygen concentration on culturability/viability of two Campylobacter jejuni isolates. Additionally, after stress exposure, in an in vitro cell culture model using Caco-2 cells, the adhesion, invasion and intracellular survival of C. jejuni were studied. Nutrient insufficiency was the most powerful stress factor which significantly affected C. jejuni culturability and viability, as well as, adhesion and invasion properties. Temperature elevation induced a transient growth arrest, and temporary loss of pathogenic potential as indicated by impaired adhesion and invasion efficiency of C. jejuni. However, bacteria recovered within 24–48 h inside the Caco-2 cells. Oxidative stress neither affected C. jejuni growth nor reduced the binding and invasion into Caco-2 cells. Only 5 h oxygen exposure increased the invasion capability and intraepithelial survival of the clinical isolate. Modulation of C. jejuni virulence in response to environmental stress factors may have further implications in the pathogenesis of campylobacteriosis. r 2007 Elsevier Ltd. All rights reserved. Keywords: Campylobacter jejuni; Stress; Culturability; Viability; Virulence 1. Introduction Campylobacter is recognized as the most frequent agent of food-borne bacterial diarrhea in humans. Human cases are mostly caused by Campylobacter jejuni, a Gram- negative, spiral, microaerophilic bacterium that exists as a commensal organism in the intestinal tract of many wild and domestic birds and mammals. Infections in humans are usually acquired through the consumption of under- cooked poultry or contaminated drinking water [1,2]. While most food-borne pathogens are considered to be relatively robust organisms, as a consequence of the necessity to survive under diverse conditions both inside and outside the host, Campylobacter species have uniquely fastidious growth requirements and an unusual sensitivity to environmental stress. Campylobacters are considered microaerobic bacteria, therefore unable to grow in the presence of air, and sensitive to toxic products of oxygen metabolism. The organisms grow within a narrow tem- perature range from approximately 32 to 47 1C. Despite its thermophilic nature, human body temperature is found optimal for growth and chemotaxis of Campylobacter [3], while cell death occurs at 56–57 1C [4]. When compared to other food-borne pathogens, like Salmonella enteritidis and Staphylococcus aureus, C. jejuni shows an increased susceptibility to slow-air-drying on surfaces [5]. Also, C. jejuni poorly survives UVB exposure [6], hydrostatic pressure [7], as well as, low pH of the microenvironment [8]. However, the increasing incidence of human enteric ARTICLE IN PRESS www.elsevier.com/locate/micpath 0882-4010/$ - see front matter r 2007 Elsevier Ltd. All rights reserved. doi:10.1016/j.micpath.2007.03.004 Ã Corresponding author. Tel.:+385 51 651 172; fax.:+385 51 651 177. E-mail address: amaja@medri.hr (M. Abram).