Historical Distribution and Molecular Diversity of Bacillus anthracis, Kazakhstan

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Volume 16, Number 5–May 2010
Research
Historical Distribution and Molecular Diversity of Bacillus anthracis, Kazakhstan
Alim M. Aikembayev,1 Larissa Lukhnova, Gulnara Temiraliyeva, Tatyana Meka-Mechenko, Yerlan Pazylov, Sarkis Zakaryan, Georgiy Denissov, W. Ryan Easterday, Matthew N. Van Ert,2 Paul Keim, Stephen C. Francesconi, Jason K. Blackburn,3 Martin Hugh-Jones, and Ted Hadfield
Author affiliations: Kazakhstan Scientific Center for Quarantine and Zoonotic Diseases, Almaty, Kazakhstan (A.M. Aikembayev, L. Lukhnova, G. Temiraliyeva, T. Meka-Mechenko, Y. Pazylov, S. Zakaryan, G. Denissov); Northern Arizona University, Flagstaff, Arizona, USA (W.R. Easterday, P. Keim); Midwest Research Institute, Palm Bay, Florida, USA (M.N. Van Ert, T. Hadfield); The Translational Genomics Research Institute, Phoenix, Arizona, USA (P. Keim); Naval Medical Research Center, Silver Spring, Maryland, USA (S.C. Francesconi); California State University, Fullerton, California, USA (J.K. Blackburn); and Louisiana State University, Baton Rouge, Louisiana, USA (M. Hugh-Jones)

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Abstract
To map the distribution of anthrax outbreaks and strain subtypes in Kazakhstan during 1937–2005, we combined geographic information system technology and genetic analysis by using archived cultures and data. Biochemical and genetic tests confirmed the identity of 93 archived cultures in the Kazakhstan National Culture Collection as Bacillus anthracis. Multilocus variable number tandem repeat analysis genotyping identified 12 genotypes. Cluster analysis comparing these genotypes with previously published genotypes indicated that most (n = 78) isolates belonged to the previously described A1.a genetic cluster, 6 isolates belonged to the A3.b cluster, and 2 belonged to the A4 cluster. Two genotypes in the collection appeared to represent novel genetic sublineages; 1 of these isolates was from Krygystan. Our data provide a description of the historical, geographic, and genetic diversity of B. anthracis in this Central Asian region.

Anthrax is a globally widespread disease of livestock and wildlife that occasionally infects humans. According to official estimates, the number of human anthrax cases worldwide ranges from 2,000 to 20,000 annually (1). Bacillus anthracis, the etiologic agent of anthrax, persists in the environment as a dormant, highly stable spore. The prolonged periods of dormancy during the spore phase slows evolution of this species, resulting in high levels of interstrain genetic homogeneity, which complicates efforts to subtype the pathogen. The availability of whole-genome nucleotide sequences of B. anthracis for single-nucleotide polymorphism (SNP) elucidation and the discovery of polymorphic markers such as variable number tandem repeat (VNTR) sequences (2,3) have enabled identification of unique subtypes within this species. Keim et al. (4) used 8 VNTRs to describe 89 unique genotypes in a global collection of over 400 B. anthracis isolates. Later studies used VNTRs to examine B. anthracis diversity in different global regions, including France (5), Italy (6), Poland (7), Chad (8), and South Africa (9). More recently, SNPs that define major clonal lineages in B. anthracis have been identified and applied to describe global and regional patterns of B. anthracis diversity (10).

In the central Asian republic of Kazakhstan, anthrax is enzootic and still represents a human public health concern. A recent publication examined risk factors associated with 73 human anthrax cases in Kazakhstan over a 2-year period (11) and concluded that most cases were cutaneous and had resulted from the handling of infected livestock and contaminated animal products. Gastrointestinal anthrax in Kazakhstan has also been reported but is less common. Despite the widespread nature of the disease in this region, the historical incidence, distribution, and genetic diversity of B. anthracis in central Asia, and Kazakhstan in particular, has remained cryptic.

We mapped the historical distribution of anthrax in Kazakhstan over a 68-year period. Archived cultures from a subset of these outbreaks collected from 10 oblasts (provinces) over a 53-year period were analyzed by using genetic and biochemical tests. Multilocus variable number tandem repeat analysis (MLVA) and canonical single nucleotide polymorphism genotyping (10) of this collection enabled us to examine strain dynamics among and within these outbreaks and to understand the diversity of B. anthracis isolates from Kazakhstan on a local, regional, and global scale.

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Suggested Citation for this Article
Aikembayev AM, Lukhnova L, Temiraliyeva G, Meka-Mechenko T, Pazylov Y, Zakaryan S, et al. Historical distribution and molecular diversity of Bacillus anthracis, Kazakhstan. Emerg Infect Dis [serial on the Internet]. 2010 May [date cited]. http://www.cdc.gov/EID/content/16/5/789.htm

DOI: 10.3201/eid1605.091427