Brucellosis is a highly infectious zoonotic disease but rare in Sweden. Nonetheless, an outbreak of canine brucellosis caused by an infected dog imported to Sweden was verified in 2013. In total 25 dogs were tested at least duplicated by the following approaches: real-time PCR for the detection of Brucella canis, a Brucella genus-specific real-time PCR, selective cultivation, and microscopic examination. The whole genome of B. canis strain SVA13 was analysed regarding genetic markers for epidemiological examination. The genome of an intact prophage of Roseobacter was detected in B. canis strain SVA13 with whole genome sequence prophage analysis (WGS-PA). It was shown that the prophage gene content in the American, African and European isolates differs remarkably from the Asian strains. The prophage sequences in Brucella may therefore serve of use as genetic markers in epidemiological investigations. Phage DNA fragments were also detected in clustered, regularly interspaced short palindromic repeats (CRISPR) in the genome of strain SVA13. In addition to the recommendations for genetic markers in Brucella outbreak tracing, our paper reports a validated two-step stand-alone real-time PCR for the detection of B. canis and its first successful use in an outbreak investigation.
Campylobacter jejuni and Campylobacter coli are important bacterial enteropathogens. Poultry is the best-known reservoir for Campylobacter infection but natural bodies of water have also been shown to be important pathways for transmission. Campylobacter can survive in cold water but most of the studies have focused on C. jejuni only. In this paper, we take a closer look at the biology and water survival strategies of C. coli. Eight C. coli isolates cultivated from raw (incoming) surface water at water plants in Sweden were characterized using whole-genome sequencing and phenotypical assays. Phylogenetic analysis assigned the Swedish water isolates to clades 2 and 3, known to include C. coli of environmental origin. In addition, 53 earlier published sequences of C. coli clade 2 and 3 from environmental waters were included for in silico analyses. Generally, clade 2 isolates had larger genomes, which included a functional tricarballylate utilization locus, while clade 3 isolates contained different genes involved in oxidative stress as well as putative virulence factors. The Swedish water isolates of clade 2 formed large, blurry bacterial colonies on agar, whereas clade 3 colonies were smaller. All Swedish isolates were motile, but clade 3 isolates formed larger motility zones on soft agar, and none of these isolates produced biofilm. Although water survival varied between the analyzed isolates, there were hardly any clade-specific significant differences. Our results highlight the diversity of C. coli in general, and show differences in metabolic capabilities and ways to handle oxidative stress between clade 2 and 3 water isolates.
Campylobacter jejuni is the most common cause of bacterial gastroenteritis. Major reservoirs are warm-blooded animals, poultry in particular, but Campylobacter can also be transmitted via water. In this paper, we have taken a closer look at the biology and potential virulence of C. jejuni water isolates. Seven C. jejuni isolates from incoming surface water at water plants in Sweden were characterized with whole genome sequencing and phenotypical testing. Multi locus sequence typing analysis revealed that these isolates belonged to groups known to include both common (ST48CC) and uncommon (ST1275CC, ST683, ST793 and ST8853) human pathogens. Further genomic characterization revealed that these isolates had potential for arsenic resistance (due to presence of arsB gene in all isolates), an anaerobic dimethyl sulfoxide oxidoreductase (in three isolates) and lacked the MarR-type transcriptional regulator gene rrpB (in all but one isolate) earlier shown to be involved in better survival under oxidative and aerobic stress. As putative virulence factors were concerned, there were differences between the water isolates in the presence of genes coding for cytolethal distending toxin (cdtABC), Type VI secretion system and sialylated LOS, as well as in biofilm formation. However, all isolates were motile and could adhere to and invade the human HT-29 colon cancer cell line in vitro and induce IL-8 secretion suggesting potential to infect humans. This is, to the best of our knowledge, the first study where C. jejuni water isolates have been characterized using whole genome sequencing and phenotypical assays. We found differences and shared traits among the isolates but also potential to infect humans.
Cites: Am J Epidemiol. 2003 Aug 1;158(3):234-4212882945