High prevalence and two dominant host-specific genotypes of Coxiella burnetii in U.S. milk

BMC Microbiology (Impact Factor: 2.73). 02/2014; 14(1):41. DOI: 10.1186/1471-2180-14-41
Source: PubMed


Coxiella burnetii causes Q fever in humans and Coxiellosis in animals; symptoms range from general malaise to fever, pneumonia, endocarditis and death. Livestock are a significant source of human infection as they shed C. burnetii cells in birth tissues, milk, urine and feces. Although prevalence of C. burnetii is high, few Q fever cases are reported in the U.S. and we have a limited understanding of their connectedness due to difficulties in genotyping. Here, we develop canonical SNP genotyping assays to evaluate spatial and temporal relationships among C. burnetii environmental samples and compare them across studies. Given the genotypic diversity of historical collections, we hypothesized that the current enzootic of Coxiellosis is caused by multiple circulating genotypes. We collected A) 23 milk samples from a single bovine herd, B) 134 commercial bovine and caprine milk samples from across the U.S., and C) 400 bovine and caprine samples from six milk processing plants over three years.
We detected C. burnetii DNA in 96% of samples with no variance over time. We genotyped 88.5% of positive samples; bovine milk contained only a single genotype (ST20) and caprine milk was dominated by a second type (mostly ST8).
The high prevalence and lack of genotypic diversity is consistent with a model of rapid spread and persistence. The segregation of genotypes between host species is indicative of species-specific adaptations or dissemination barriers and may offer insights into the relative lack of human cases and characterizing genotypes.

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Available from: Erin P Price, Mar 12, 2014
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    • "tick and human blood in Kazakhstan [17]. ST37 genotype is closely related to ST27-28, 31 and 8–10 genotypes that have been collected from humans in Austria, Kazakhstan, Uzbekistan, France and Portugal as well as sheep and goats from Spain, France, Canada and the USA (Figure 2) [17,20,28,29,39]. The comparison of the novel genotypes (AG and AF) with others described in Europe revealed similarities with genotypes AA and T, differing at 2 and 3 loci respectively and also associated with sheep, goats and human [28,29]. "
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    ABSTRACT: Background Information about the genotypic characteristic of Coxiella burnetii from Hungary is lacking. The aim of this study is to describe the genetic diversity of C. burnetii in Hungary and compare genotypes with those found elsewhere. A total of 12 samples: (cattle, n = 6, sheep, n = 5 and human, n = 1) collected from across Hungary were studied by a 10-loci multispacer sequence typing (MST) and 6-loci multiple-locus variable-number of tandem repeat analysis (MLVA). Phylogenetic relationships among MST genotypes show how these Hungarian samples are related to others collected around the world. Results Three MST genotypes were identified: sequence type (ST) 20 has also been identified in ruminants from other European countries and the USA, ST28 was previously identified in Kazakhstan, and the proposed ST37 is novel. All MST genotypes yielded different MLVA genotypes and three different MLVA genotypes were identified within ST20 samples alone. Two novel MLVA types 0-9-5-5-6-2 (AG) and 0-8-4-5-6-2 (AF) (Ms23-Ms24-Ms27-Ms28-Ms33-Ms34) were defined in the ovine materials correlated with ST28 and ST37. Samples from different parts of the phylogenetic tree were associated with different hosts, suggesting host-specific adaptations. Conclusions Even with the limited number of samples analysed, this study revealed high genetic diversity among C. burnetii in Hungary. Understanding the background genetic diversity will be essential in identifying and controlling outbreaks.
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