RESUMO
Abstract Listeria monocytogenes is responsible for causing listeriosis, a type of food poisoning with high mortality. This bacterium is mainly transmitted to humans through the consumption of contaminated foods. Detection of L. monocytogenes through molecular methods is crucial for food safety and clinical diagnosis. Present techniques are characterized by low discrimination power and high cost, as well as being time-consuming and taking several days to give the final result. In our study, MLVA-HRM (Multiple-Locus Variable-number tandem repeats Analysis ‒ High-Resolution Melting) was investigated as an alternative method for a fast and precise method for the genotyping of L. monocytogenes isolates. Forty-eight isolates of L. monocytogenes obtained from the microbial bank of Department of Microbiology, Iran University of Medical Sciences, were typed by MLVA-HRM analysis using five Variable Numbers of Tandem Repeat (VNTR) loci. A total of 43 different types were obtained. This research demonstrated the usefulness of the MLVA-HRMA method and its ability to discriminate L. monocytogenes isolates. Since this method is easier and more efficient than existing methods, it can be widely used in food processing plants and diagnostic laboratories as a fast and accurate method.
RESUMO
ABSTRACT Background: Epidemiological studies are important tools to assess the diversity of Brucella isolates and to estimate their epidemiological relationship among isolates from different geographical origins. In this study the MLVA16 (multiple-locus variable number tandem repeat analysis based on 16 loci) was employed to investigate the diversity of Brucella spp. Isolated from humans and animals for epidemiological purposes and to determine the most common Brucella genotypes in Iran. Methods: We designed a molecular-based study to evaluate the potential reservoirs of human brucellosis. After isolation and identification of 54 Brucella spp human and animal specimens from three regions of Iran, bacterial genomic DNA was extracted MLVA with three panel was used for the genotyping of isolates. The size of PCR products were analyzed and converted to repeat unit numbers using a published allele numbering system and data set was imported into Bionumerics. Results: Three isolates (5.55%) were identified as Brucella abortus and 51 (94.44%) as Brucella melitensis. Two isolates of Brucella abortus were from humans and one from an animal. Thirty-four Brucella melitensis isolates were from humans and 17 from animals. Using MLVA16-genotyping, 54 isolates with genetic similarity coefficient of 80% were divided into 46 genotypes and 22 genotypes were represented by a single isolate, while 4, 2, 1 and 2 genotypes were represented by 2, 3, 4 and 7 isolates, respectively. The most prevalent genotype was represented by 14 isolates. There were two other frequent genotypes each represented by seven isolates, among which only one was restricted to a geographic region. Discriminatory power for each locus was determined in this study and panel 2B shows the high discretionary power [Bruce04 (0.837), Bruce30 (0.806), Bruce 09 (0.787), Bruce 07 (0.772), Bruce16 (0.766)]. Conclusion: MLVA16 analysis of 54 Brucella isolates showed high level polymorphism in their genotypes. Only two genotypes, each observed in seven isolates, were related to one another and only one of these genotypes were found in to two separate regions.