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United States Department of Agriculture

Agricultural Research Service


item Jensen, Allen
item Halling, Shirley

Submitted to: American Society for Microbiology
Publication Type: Abstract Only
Publication Acceptance Date: 3/7/2005
Publication Date: 6/9/2005
Citation: Jensen, A.E., Halling, S.M. 2005. Vast differences in sensitivity among brucella species to polymyxin b and colistin [abstract]. American Society for Microbiology. 2005 CDROM.

Interpretive Summary:

Technical Abstract: Brucella is much more resistant to polycations than enteric bacteria; however, the relative sensitivity of Brucella species to polymyxin B (PB) and colistin (CO) has not been thoroughly studied. Comparative sensitivities of the classical Brucella reference strains and biovars to these two cationic peptides were determined by the Etest and vast differences were found. Both B. melitensis and B. suis and their biovars were much less sensitive to these two antibiotics and the polycations bactenecin, cecropin P1, lactoferricin, magainin 1, and mellitin than the other Brucella spp. One of the brucellae, B. suis biovar 4 was considerably more resistant than the other brucellae. The relative sensitivity to PB and CO of a high passage isolate of RB51, isolated from Kuzdas and Morse (KM) medium containing PB was less sensitive than the parental strain and other rough strains of Brucella. Though growth of RB51 is independent of CO2, it grew on KM in the presence of CO2 but not in ambient air. Studies showed that most Brucella strains tested were more resistant to PB and CO when grown in the presence of CO2. With few exceptions, as the pH became more acid the strains became less sensitive to PB and CO. The relative sensitivities of several field strains and isolates from marine mammals to the reference strains were also determined. We found that the Etest was a rapid assay to determine sensitivity of brucellae to PB and CO and that there are vast differences in the relative sensitivity of Brucella species to PB and CO. Results from this study are applicable to diagnostic isolation of brucellae, the gold standard for the detection of Brucella infection.

Last Modified: 09/21/2017
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