Nutritionally variant streptococci from corneal ulcers in horses.

The study tests the characteristics and antimicrobial susceptibility of a group of bacteria (nutritionally variant streptococci or NVS) found in horse eye ulcers. A nutrient supplement was used to achieve optimal growth for these bacteria in laboratory conditions. The biochemical patterns of these bacteria were found to resemble two types of streptococci species, while certain patterns remained unfamiliar. The tested bacteria exhibited sensitivity to specific antimicrobial agents with only a few exceptions.

Growth Requirements and Environment

• The research investigated 24 samples of NVS collected from equine corneal ulcers, and of these, 22 were extensively tested and analyzed.
• The optimal growth of these bacteria was obtained by supplementing blood agar and a growth medium called Todd-Hewitt broth with a substance called pyridoxal hydrochloride.
• For culture and testing purposes, all the media used was likewise supplemented with 0.002% of this compound, indicating that these bacteria required such conditions to grow and be studied effectively.

Biochemical Reactions and Patterns

• The researchers found interesting results when studying the biochemical reactions and patterns of these bacteria.
• Half of the isolates (12 out of 22) showed biochemical patterns resembling those of two viridans streptococcal species i.e., Streptococcus intermedius and Streptococcus constellatus.
• However, the patterns of the remaining 10 isolates did not resemble those of any recognized viridans species, suggesting that they may be unique or divergent species.

Antimicrobial Susceptibility

• The study also evaluated the susceptibility of these NVS isolates to various antimicrobial agents.
• All of the tested bacteria were found to be inhibited by less than or equal to 0.25 micrograms of erythromycin per ml, less than or equal to 4 micrograms of chloramphenicol per ml, and less than or equal to 4 micrograms of gentamicin per ml.
• Interestingly, all but two of the isolates were also inhibited by less than or equal to 0.1 microgram of penicillin per ml, implying that the majority of these bacteria are sensitive to a low dose of penicillin, with only a couple of exceptions.