Antimicrobial susceptibility testing of Brucella melitensis isolated from patients with acute brucellosis in a centre of Iran

Abstract

Structured to Purpose: Human brucellosis is one of the most common zoonotic infections worldwide, which remains one of the major problems for public health. Despite the World Health Organization's recommendation for human brucellosis treatment, sporadic cases of relapse have been reported. The aim of this study was to assess the susceptibility of Brucella isolates to common antibiotics that are prescribed by the physician for the treatment of brucellosis and also to determine the minimum inhibitory concentration 50% (MIC 50 ) and MIC 90 for these antibiotics.

Materials and methods: Forty-eight Brucella strains were collected from patients with acute brucellosis. Species identification was made based on the conventional methods. MIC of rifampin, doxycycline, ciprofloxacin, trimethoprim- sulfamethoxazole, streptomycin, azithromycin and ceftriaxone was determined by E-test.

Results: All the 48 Brucella isolates (47 blood samples and one synovial fluid) were identified as Brucella melitensis. No antimicrobial-resistant strains were recognised. Trimethoprim-sulfamethoxazole had the lowest MIC 50 (0.016 μg/ml) and MIC 90 (0.064 μg/ml), whereas MIC 50 and MIC 90 of streptomycin and azithromycin had the highest level at 0.625, 1.5 µg/ml and 0.25, 1 µg/ml, respectively. All the isolates were susceptible to rifampin, and only one of the isolates had a reduced sensitivity to rifampin (1 μg/ml).

Conclusions: Although all the Brucella isolates were susceptible, antimicrobial susceptibility test should be recommended in patients with recurrent brucellosis or life-threatening organ involvement.