Anaerobic bacterial pneumonia with septicemia in two racehorses.

This research study evaluated two Thoroughbred racehorses that had an anaerobic bacterial pneumonia with septicemia infection, which did not initially respond to antibiotic treatments. The study found that the horses responded differently to similar treatments, with one horse recovering after six months while the other horse died due to pulmonary hemorrhage.

Overview of the Study

• The study focused on two Thoroughbred racehorses that presented with a respiratory tract disease, specifically anaerobic bacterial pneumonia with septicemia.
• Initial treatment with conventional antibiotics such as penicillin and trimethoprim-sulfamethoxazole did not elicit a response in the horses.
• The bile of both horses was bathing in multiple anaerobic organisms like Bacteroides spp and Fusobacterium spp, isolated from the blood and transtracheal aspirates, and from cutaneous nodules in one.

Results of Intervention

• In an attempt to manage the diseases, the horses were administered metronidazole.
• Interestingly, one horse displayed improvement in health after six months of metronidazole treatment, with procaine penicillin G then provided as maintenance treatment.
• However, the second horse didn’t respond favorably to the same regimen, and unfortunately died following an acute pulmonary hemorrhage episode and maintaining a fever intermittently for seven weeks.

Insights from the Study

• Despite in vitro antimicrobial susceptibility tests indicating that the isolated anaerobic organisms could be susceptible to penicillin, it didn’t seem to alleviate the infection in these horses.
• The researchers speculated the reason could be due to inadequate penicillin concentration in the deep lung infection foci.
• The study also suggested that animals with anaerobic bacterial infections that are resistant to penicillin or fail to respond to it might gain from metronidazole treatment.