Increasing Resistance of Brucellae to Co-Trimoxazole

Brucellosis is still a common disease in many developing countries, particularly among farm workers, abattoir workers, and veterinarians, as well as those who rear sheep and camels. Similarly, the disease is prevalent among those who are in the habit of drinking fresh unpasteurized camel or goat milk (4). In Saudi Arabia it contributes substantially to ill health and outpatient visits (3). In order to reduce the incidence of complications of brucellosis and the development of drug resistance by the pathogen, it is necessary that proper treatment be instituted, following antibiotic susceptibility testing.

In most publications it is usually recommended that trimethoprim-sulfamethoxazole be given in combination with tetracycline or streptomycin (1, 2, 5). We retrospectively reviewed the susceptibility pattern of the Brucella melitensis isolates in our microbiology laboratory from 1 October 1995 to June 1998. Susceptibility testing was carried out by the Kirby Bauer disk diffusion technique on 37 isolates from blood cultures and joint aspirates. All except one isolate were sensitive to rifampin, tetracycline, gentamicin, and ciprofloxacin. However, only 14 of 37 (38%) were sensitive to co-trimoxazole. In view of this finding we advocate that blood cultures and/or appropriate cultures should be attempted when a suspected case of brucellosis is encountered, so that the organism could be isolated and the susceptibility of the particular strain could be determined. While susceptibility tests are evaluated, we suggest that tetracycline in combination with ciprofloxacin should be started. With the development of resistance by virtually most organisms, such as staphylococci, enterococci, and enterobacteria, and Pseudomonas spp., the sensitivity of brucellae to the traditional drugs cannot be assumed. Every locality will need to make every attempt to determine the sensitivity pattern of the local isolates of B. melitensis, and less reliance should be placed on serological diagnosis of brucellosis.