Selective medium for isolation of Bacteroides nodosus

Area of Science:

• Veterinary Microbiology
• Antimicrobial Susceptibility Testing

Background:

• Sheep foot rot is a contagious disease caused by Bacteroides nodosus.
• Accurate isolation of B. nodosus is crucial for diagnosis and treatment strategies.

Purpose of the Study:

• To evaluate the antimicrobial susceptibility of B. nodosus.
• To develop a selective medium for isolating B. nodosus from mixed microbial populations in foot rot lesions.

Main Methods:

• Antimicrobial sensitivity testing of B. nodosus against 24 agents.
• Culturing sheep foot rot lesions on basal medium versus lincomycin-supplemented selective medium.
• Assessing the impact of agar concentration on selective medium efficacy.

Main Results:

• Bacteroides nodosus showed resistance to lincomycin, while common contaminants were sensitive.
• A selective medium with 1 µg/ml lincomycin optimally inhibited contaminants, allowing B. nodosus growth.
• B. nodosus was isolated from 16/31 lesions using the selective medium, compared to 3/31 on basal medium.
• Agar concentration influenced B. nodosus growth in the presence of lincomycin.
• Trimethoprim also showed potential selectivity for B. nodosus.

Conclusions:

• Lincomycin serves as an effective selective agent for isolating Bacteroides nodosus from sheep foot rot lesions.
• The developed selective medium significantly enhances the detection rate of B. nodosus.
• Further investigation into trimethoprim's selectivity is warranted.