Identification, Genotyping and Antimicrobial Susceptibility Testing of Brucella spp. Isolated from Livestock in Egypt

Abstract

Brucellosis is a highly contagious zoonosis worldwide with economic and public health impacts. The aim of the present study was to identify <i>Brucella</i> (<i>B</i>.) spp. isolated from animal populations located in different districts of Egypt and to determine their antimicrobial resistance. In total, 34-suspected <i>Brucella</i> isolates were recovered from lymph nodes, milk, and fetal abomasal contents of infected cattle, buffaloes, sheep, and goats from nine districts in Egypt. The isolates were identified by microbiological methods and matrix-assisted laser desorption ionization time-of-flight mass spectrometry (MALDI-TOF MS). Differentiation and genotyping were confirmed using multiplex PCR for <i>B. abortus</i>, <i>Brucella melitensis</i>, <i>Brucella ovis</i>, and <i>Brucella suis</i> (AMOS) and Bruce-ladder PCR. Antimicrobial susceptibility testing against clinically used antimicrobial agents (chloramphenicol, ciprofloxacin, erythromycin, gentamicin, imipenem, rifampicin, streptomycin, and tetracycline) was performed using E-Test. The antimicrobial resistance-associated genes and mutations in <i>Brucella</i> isolates were confirmed using molecular tools. In total, 29 <i>Brucella</i> isolates (eight <i>B. abortus</i> biovar 1 and 21 <i>B. melitensis</i> biovar 3) were identified and typed. The resistance of <i>B. melitensis</i> to ciprofloxacin, erythromycin, imipenem, rifampicin, and streptomycin were 76.2%, 19.0%, 76.2%, 66.7%, and 4.8%, respectively. Whereas, 25.0%, 87.5%, 25.0%, and 37.5% of <i>B. abortus</i> were resistant to ciprofloxacin, erythromycin, imipenem, and rifampicin, respectively. Mutations in the <i>rpo</i>B gene associated with rifampicin resistance were identified in all phenotypically resistant isolates. Mutations in <i>gyr</i>A and <i>gyr</i>B genes associated with ciprofloxacin resistance were identified in four phenotypically resistant isolates of <i>B. melitensis</i>. This is the first study highlighting the antimicrobial resistance in <i>Brucella</i> isolated from different animal species in Egypt. Mutations detected in genes associated with antimicrobial resistance unravel the molecular mechanisms of resistance in <i>Brucella</i> isolates from Egypt. The mutations in the <i>rpo</i>B gene in phenotypically resistant <i>B. abortus</i> isolates in this study were reported for the first time in Egypt.