Brucellosis is a zoonotic disease caused by the bacteria of genus Brucella and transmitted through direct or indirect contact to animal [1]. Brucellae based on differences in pathogenicity, phenotypic characteristics and host reference were classified within eleven species [2, 3]. Four of species including Brucella abortus, Brucella melitensis, Brucella canis and Brucella suis are known to infect human. Enormous economic losses and public health problems occur due to abortion, infertility in livestock, weak offspring, decreased milk production and morbidity in human. Although Brucellosis has been eradicated in the USA, Canada, North Europe, Australia, this disease is highly prevalent in central Asia, the Middle East, the Mediterranean region, Africa and Latin America [4]. Iran is an endemic area for Brucellosis and there is a main risk of Brucella transmission from eastern and western neighbors such as Iraq, Pakistan and Afghanistan due to don’t have high quality veterinary services for controlling animal disease [5, 6]. Despite, 500000 Brucellosis human cases reported around the world in every year, there are the numbers of undetected and neglected cases [7]. The key control for Brucellosis in human is control of this disease in animal and using of epidemiological studies to assess the diversity among strains for epidemiological purpose in human brucellosis and to estimate the epidemiological relationship of isolates from different geographical origin [8, 9].
The classical phenotyping methods such as serotyping, phage typing, metabolic profiles and sensitivity to dyes have been employed to subtype Brucellosis, but these techniques are available in reference laboratories only, have a limited discriminatory power, time consuming, require manipulating the living agent and in a lake of standardization interpretation of this method cause difficulties [10].
For these limited in phenotyping methods, bacterial typing shift towards molecular identification which investigate epidemiological relationships among isolates and source of infection. Several molecular typing methods have been introduced such as random amplified polymorphic DNA (RAPD)-PCR, amplified fragment-length polymorphism (AFLP), Pulse field gel electrophoresis (PFGE), Polymerase chain reaction restriction fragment length polymorphism, Multilocus sequence typing (MLST) and Multiple Loci VNTR (Variable number tandem repeats) analysis (MLVA). MLVA method introduced as an effective and rapid tool which monitors the variability in the copy numbers of tandem repeat units (TRS) with higher discriminatory power [11]. This method not only uses in outbreak and epidemiological trace-back investigations but also use in confirmatory laboratory or food borne acquired infections. TR sequences are multiple allels can be presented at a single locus, and based on their size differences can be easily resolved through agarose electrophoresis or capillary electrophoresis equipment [12]. MLVA has been proven to be a good technique for the assessment of pathogenic bacteria such as Brucella that display very little genomic diversity. MLVA schemes with 21, 15 and 16 loci (MLVA21, 15 and 16) have been published. MLVA 16 has been proposed by Al-Dahank et al with eight minisatellite markers (panel1: Bruce06, Bruce 08, Bruce11, Bruce 12, Bruce 42, Bruce 43, Bruce 45 and Bruce 55) for species identification and eight microsatellite markers (panel2A: Bruce18, Bruce 19, Bruce 21 and 2B: Bruce 04, Bruce 07, Bruce 09, Bruce 16 and Bruce 30) for determine the most common genotypes and the further subspecies differentiation [13]. The genetic diversity of Brucella strains isolated from human and animal infection has not yet been investigated in Iran. The main objectives of this study was applied the MLVA16 assay to investigate and to determine the diversity among Brucella strains for epidemiological purposes in human and animal and determine the most common genotypes among Brucella strains in Iran.