Phenotypic and Transcriptomic Responses of Campylobacter jejuni Suspended in an Artificial Freshwater Medium

Abstract

Campylobacter jejuni is the leading cause of campylobacteriosis in the developed world. Although most cases are caused by consumption of contaminated meat, a significant proportion is linked to ingestion of contaminated water. The differences between C. jejuni strains originating from food products and those isolated from water are poorly understood. Working under the hypothesis that water-borne C. jejuni strains are better equipped at surviving the nutrient-poor aquatic environment than food-borne strains, the present study aims to characterize these differences using outbreak strains 81116 and 81-176. Strain 81116 caused a campylobacteriosis outbreak linked to consumption of water, while strain 81-176 was linked to consumption of raw milk. CFU counts and viability assays showed that 81116 survives better than 81-176 at 4°C in a defined freshwater medium (Fraquil). Moreover, 81116 was significantly more resistant to oxidative stress and bile salt than strain 81-176 in Fraquil. To better understand the genetic response of 81116 to water, a transcriptomic profiling study was undertaken using microarrays. Compared to rich broth, strain 81116 represses genes involved in amino acid uptake and metabolism, as well as genes involved in costly biosynthetic processes such as replication, translation, flagellum synthesis and virulence in response to Fraquil. In accordance with the observed increase in stress resistance in Fraquil, 81116 induces genes involved in resistance to oxidative stress and bile salt. Interestingly, genes responsible for cell wall synthesis were also induced upon Fraquil exposure. Finally, twelve unique genes were expressed in Fraquil; however, analysis of their distribution in animal and water isolates showed that they are not uniquely and ubiquitously present in water isolates, and thus, unlikely to play a major role in adaptation to water. Our results show that some C. jejuni strains are more resilient than others, thereby challenging current water management practices. The response of 81116 to Fraquil serves as a starting point to understand the adaptation of C. jejuni to water and its subsequent transmission.

Retail liver juices enhance the survivability of Campylobacter jejuni and Campylobacter coli at low temperatures

“…Among C. jejuni strains, used clinical strains survived better than poultry strains at low temperatures (4 °C and 10 °C) in a previous report 63 . Likewise, a waterborne C. jejuni strain showed better survival in defined fresh water media at 4 °C than a foodborne strain 51 . In contrast, a few reports have shown similar survival rates for both species 40,41 and higher survival rate of C. coli at low temperatures in different food models 64 .…”

“…A variety of genes were essential for survival at low temperatures in nutrient-rich or nutrient-poor media 55 . All transcriptomic and genome fit analyses of Campylobacter at low temperatures have been conducted with C. jejuni 9,36,43,51,55 . Genomic differences between C. jejuni and C. coli strains 52 might contribute to differences in survival.…”

“…In both conditions, higher survival rate of C. coli strains in the retail liver environment compared to other food matrices might have contributed to the higher prevalence; however, a precise explanation remains unclear. Most studies on Campylobacter survival and gene expression have been conducted with C. jejuni 36,37,43,51 however, it is important to note that genomic differences between Campylobacter spp 52 might be associated with differential survival rates and stress tolerance mechanisms. A few studies have shown higher survival rates of C. jejuni vs. C. coli strains at a lower temperatures, although contrasting results have been reported 41,48,53,54 .…”

Characterization of genes differentially regulated after bile acid exposure in Campylobacter jejuni

“…Symptoms of Campylobacteriosis are watery to bloody diarrhea, with fever, nausea, vomiting and abdominal pain. It can be fatal to vulnerable individuals (Trigui et al 2017). Of the 26 species of Campylobacter described, C. jejuni and C. coli cause more than 90% of all human Campylobacteriosis cases (Dasti et al 2010).…”