Isolation of Streptococcus pneumoniae from the respiratory tract of horses.

The research article discusses the isolation of the Streptococcus pneumoniae bacteria from the respiratory tract of Thoroughbred horses. The findings suggest an association between the bacteria and lower respiratory tract inflammatory disease in these horses, though the bacteria do not appear to cross-infect from horses to their handlers.

Sample Collection and Bacterial Isolation

• The researchers collected nasopharyngeal swabs and tracheal washings from horses in training at four different stables to study the presence and spread of respiratory disease.
• Streptococcus pneumoniae was successfully isolated from these samples in three of the four stables. In one stable, the researchers found that five out of 15 horses carried the bacteria for at least four months.
• The researchers found that the bacteria’s growth in culture was enriched by a carbon dioxide environment.

Association with Respiratory Disease

• The study found an association between the presence of Streptococcus pneumoniae in heavy growths (10(6) to 10(8) colony-forming units/ml) and lower respiratory tract inflammatory disease in horses.
• This bacterial growth was primarily of Streptococcus pneumoniae alone, or occurring with large numbers of Streptococcus zooepidemicus, another common bacterial strain.

Type of Bacterial Strains

• All twelve strains of Strep pneumoniae isolated from the three stables were of capsule Type 3. This could point towards a common source of infection among these stables.
• However, a Type 9 strain was isolated from nose and throat swabs of 32 staff working in one of these stables. This is noteworthy as it suggests there was no cross-infection between horses and their handlers, at least in this instance.