Cell Envelope Virulence Genes among Field Strains of Brucella melitensis Isolated in West Bank Part of Palestine

Despite the conjunctival vaccination program against Brucellosis in Palestine for more than 15 years, brucellosis continues to be a big problem concern, with increased incidence widely noted. Brucella melitensis is a facultative intracellular bacterium that replicates within macrophages. Recent reports showed that certain cell envelope associated genes of the B. melitensis is associated with its environmental stress adaptation and intracellular survival. Identification and characterization of these genes are essential to implementing efficient disease control and prevention systems. The aim of this study is to identify the cell envelope virulence associated genes of B. melitensis strains in Palestine. A total of 80 non-repetitive B. melitensis isolates were obtained from milk samples collected from infected small ruminants in the northern districts of the West Bank, Palestine during 2013 and 2015. The milk were cultured on Brucella agar (Oxoid) then incubated at 37 °C for 3 to7 days. Positive cultures were identified by standard biochemical methods and confirmed by IS711 and Rev 1 rpsL gene PCR. All samples were negative for vaccine strain Rev 1 rpsL gene-PCR. The 80 B. melitensis under investigation were tested by multiplex PCR for 19 cell envelope virulence associated genes. Interestingly, our results revealed that all the 80 isolates were positive for the following genes: lpsB, lpsA rfbD, wbpL, pgm omp19, omp25, omp10, mgtA, uppS, amiC and dacF, while the other genes: wbdA, wbpZ, pmm, wbkA, perA, manB and wpbW were detected in more than 95% of the isolates.