Two Actinobacillus species isolated from laboratory rodents

Area of Science:

• Microbiology
• Bacteriology
• Rodent Health

Background:

• Actinobacillus species are known pathogens in various animals.
• Accurate identification of bacterial isolates is crucial for disease management and research.
• Previous studies have not fully characterized Actinobacillus strains from laboratory rats and hamsters.

Purpose of the Study:

• To characterize the cultural and biochemical properties of Actinobacillus strains isolated from laboratory rats and hamsters.
• To determine if these isolates represent known species or novel taxa.
• To assess potential confusion with other bacterial genera like Pasteurella.

Main Methods:

• Isolation and culturing of 17 Actinobacillus strains from laboratory rats and hamsters.
• Evaluation of cultural characteristics, including colony color on blood agar.
• Assessment of biochemical properties, specifically the urease reaction.

Main Results:

• Two distinct types of Actinobacillus were identified among the 17 strains.
• Type 1 strains exhibited characteristics consistent with Actinobacillus equuli.
• Type 2 strains possessed unique characteristics, including urease production and colony color, not matching any described species, and showed similarities to Pasteurella pneumotropica. One isolate of Type 2 was recovered from tap water.

Conclusions:

• The study identified two distinct groups within the isolated Actinobacillus strains.
• One group was identified as Actinobacillus equuli, while the other represents a potentially novel species.
• These findings highlight the importance of careful characterization to differentiate these Actinobacillus types from Pasteurella pneumotropica, especially given their isolation from laboratory animal environments and tap water.