Abstract

The present study was undertaken to investigate the deoxyribonucleic acid (DNA) polymorphism finger printing among DNA of local Brucella isolates which is a new method in molecular epidemiological studies. It was performed on 125 different human and animal samples obtained from many locations in Baghdad. A total of 11 local Brucella isolates were obtained through the study. Its biochemical characters revealed that 8 of them were belong to Brucella melitensis and 3 to Brucella abortus. All isolates were submitted to genomic organization detection which revealed the presence of two chromosomes, no plasmids were detected. The PFGE analysis after genomic digestion with restriction enzymes to the 11 local Brucella isolates and 2 reference strains were done by using two low-cleavage–frequency restriction enzymes (Not1 and X ba1) and one high – cleavage-frequency restriction enzyme which was Eco R1 followed by pulsed-field gel electrophoresis (PFGE), which revealed as general great similarity in bands patterns (DNA profiles), although the restriction pattern using X ba1 showed some missing bands in Brucella abortus isolates while it is present in Brucella melitensis which maybe a marker for species specific detection. Results of Brucella genomic digestion with Not 1 RE showed few and large fragments which where identical from strain to strain, while Eco R1 showed high number of fragments which were very close to each other and the bands pattern showed great similarity. From this study the following conclusion can be made. The restriction enzymes pattern applied to the whole genome maybe not the perfect way to investigate Brucella DNA polymorphism, and we recommend the use of restriction fragments length polymorphism to special genes and not to the whole genome.