Genetic diversity of Brucella melitensis isolates from sheep and goat milk in Iran

The genetic diversity of Brucella strains has not been fully understood. To investigate this, the genetic characteristics of ۶۴ isolates of Brucella melitensis from sheep and goats’ milk were studied using random fragment length polymorphism (RFLP) and multiple locus variable-number tandem repeat analysis (MLVA-۱۶) methods developed in Orsay, France (MLVA-۱۶Orsay). The RFLP analysis revealed that all ۶۴ isolates were of biovar one. The MLVA-typing showed that one sample was simultaneously infected with two strains of B. melitensis and the genotype of ۶۵ isolate was analyzed. Four genotypes (۴۷, ۴۲, ۴۳, and ۶۳) were identified using MLVA-۸ (panel ۱), whereas six genotypes (۱۳۸, ۱۲۵, ۱۱۶, ۱۰۸, and two unknown genotypes) were identified using MLVA۱۱ (panels ۱ and ۲A). From the review of MLVA-۱۶ (panels ۱, ۲A, and ۲B), panel ۲B showed a very high discriminatory power. Two loci of Bruc۰۴ and Bruc۳۰ from this panel had diversity index values higher than ۰.۷۱ and the average diversity index was ۰.۶۱۹. So MLVA-۱۶Orsay ۳۴ showed the genotype indicating a low genetic homogeneity among the isolates. The findings of MLVA genotyping of the isolates suggest that strains of B. melitensis isolated from the milk of small ruminants in Iran are most closely related to the isolates from neighboring countries of the Eastern Mediterranean group. To the best of our knowledge, this is the first study to indicate the potential use of MLVA genotyping for simultaneous detection of specimen contamination using two different B. melitensis biovars.

Keywords:

Brucella melitensis , Goat , Milk , MLVA , Sheep