Abstract
Corynebacterium pseudotuberculosis is the etiological agent of caseous lymphadenitis in small ruminants, a chronic disease characterized by the development of granulomas in superficial and visceral lymph nodes as well as in several organs. An important characteristic of the infection with this bacterium is the formation of a biofilm and the absence of effective antibiotic therapy against the disease. From this scenario, the objective of this study was to evaluate the susceptibility of C. pseudotuberculosis to conventional antibiotics and to red, green, and brown propolis extracts obtained by the supercritical and ethanolic extraction methods as well as its activity in the bacterial biofilm. The results of the sensitivity test using antibiotics indicated a sensitivity of C. pseudotuberculosis strains to the antimicrobial agents. The ethanolic extract of green propolis and the supercritical red propolis extract showed the best antibacterial activities against planktonic C. pseudotuberculosis. A lower antimicrobial activity of the brown propolis extract was identified. Propolis extracts were effective in interfering with the formation of the C. pseudotuberculosis biofilm but had little activity on the consolidated biofilm. In conclusion, propolis extracts are more effective against C. pseudotuberculosis in the planktonic stage, being able to interfere with the formation of bacterial biofilm. However, the action of propolis extracts in a sessile and structured microbial biofilm is reduced.
Highlights
Corynebacterium pseudotuberculosis is a Gram-positive and intracellular bacterium that causes caseous lymphadenitis (CLA) in small ruminants, a chronic disease characterized by the development of granulomas in superficial and visceral lymph nodes as well as in several organs
C. pseudotuberculosis is an infectious agent of great importance in small ruminant breeding because it causes CLA, leading to significant economic losses related to the reduced productivity and reproductive efficiency in infected animals
We identified in this study that different types of Brazilian propolis extracts can act as antibacterial agents against C. pseudotuberculosis, being able to prevent the formation of biofilm by this bacterium
Summary
Corynebacterium pseudotuberculosis is a Gram-positive and intracellular bacterium that causes caseous lymphadenitis (CLA) in small ruminants, a chronic disease characterized by the development of granulomas in superficial and visceral lymph nodes as well as in several organs. Even though it is a bacterium sensitive to most antibiotics, the therapy becomes inefficient when the bacterial biofilm is formed [3] and in encapsulated abscesses [4] In this way, the current treatment of the disease is based on opening, draining, and cleaning the lesions, which leads to environmental contamination and recurrences [5]. Propolis can reduce biofilm formation and accelerate healing processes [8], especially in cases of chronic infections that are difficult to control due to biofilm formation in the wound environment [9] This situation was evident in clinical isolates of Proteus mirabilis from patients with chronic wounds, for which ethanolic extracts of propolis were effective in inhibiting the formation of biofilm [10]
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