Vol. 12, Issue 4 (2023)

Author(s):
Anbazhagan S, Karthikeyan R, Himani KM, Ambika Nayak, Prasad Thomas and Pallab Chaudhuri

Abstract:
Brucellosis is a contagious and under-reported zoonotic disease of livestock, wild animals, and humans. As a result, the livestock economy was severely affected worldwide, including in India. To date, Brucella abortus S19 strain-based vaccine is available in India to control the disease. However, the S19 vaccine strain also has disadvantages of the virulent nature. B. abortus S19 ∆per is a mutant vaccine candidate created to overcome S19 strain disadvantages. While developing S19∆per candidate, many other strains of Brucella cultures were used for vaccine efficacy testing in an animal model. All laboratory-maintained pathogenic cultures were known to cause infection in humans. This overall concept prompted us to characterize the morphological, biochemical, and antimicrobial susceptibility of newly developed mutant strain along with pathogenic cultures of B. abortus and B. melitensis. In the initial study, we characterized the morphology, biochemical, and growth rate of B. abortus S19 and B. abortus S19∆per strains. Further, we tested the antimicrobial susceptibility of B. abortus S19 and B. abortus S19∆per, along with other standard pathogenic cultures. Commonly recommended antibiotics for treatments were used to assess the in vitro antimicrobial susceptibility testing (AST). The morphological and biochemical characterization results showed no significant difference between the S19 and S19∆per. Brucella strains showed in vitro susceptibility to tetracycline, levofloxacin, streptomycin, kanamycin, ampicillin, imipenem, amikacin, ceftriaxone, trimethoprim/sulfamethoxazole, and azithromycin. Vaccine strains were susceptible to penicillin and ampicillin. Further, MIC strips of cell wall antibiotics were used, and varying degree of resistance pattern was noticed among polymyxin, colistin, penicillin, and vancomycin to B. abortus S19 and B. abortus S19∆per. In conclusion, the sensitivity of commonly used drugs for treating Laboratory associated brucellosis should be regularly monitored. To minimize future drug resistance, we propose rationalizing the use of antibiotics in selective culture media.