Actinobacillus suis-like organisms in horses

Area of Science:

• Veterinary Microbiology
• Equine Infectious Diseases

Background:

• Actinobacillus suis-like organisms have been identified in equine samples since 1975.
• Transtracheal washings are the most common source, accounting for 65% of isolations.

Purpose of the Study:

• To characterize Actinobacillus suis-like organisms from equine sources.
• To determine their biochemical properties and antibiotic susceptibility.

Main Methods:

• Gram staining and biochemical tests (oxidase, urease, ONPG, esculin).
• Hemolysis on blood agar and carbohydrate fermentation patterns.
• Antibiotic susceptibility testing against various antimicrobials.

Main Results:

• The organism is gram-negative, hemolytic, and positive for oxidase, urease, ONPG, and esculin.
• Four main patterns of carbohydrate reactions were observed.
• 90% sensitivity was noted for amikacin, cephalothin, chloramphenicol, gentamicin, kanamycin, tetracycline, and trimethoprim-sulfamethoxazole.
• Frequent co-recovery of other aerobic and anaerobic bacteria.

Conclusions:

• Actinobacillus suis-like organisms possess distinct biochemical characteristics.
• These organisms exhibit significant sensitivity to a range of clinically relevant antibiotics.
• Understanding these properties aids in equine respiratory disease diagnosis and treatment.