Effect of trimethoprim/sulphamethoxazole and hyperbaric oxygen on experimental Spiroplasma mirum encephalitis.

This study was undertaken to determine the susceptibility of experimentally induced Spiroplasma mirum infection in the rat to trimethoprim/sulfamethoxazole (TMP/SMX) in combination with hyperbaric oxygen (HBO). One-day-old Fisher 344 rats were intracerebrally inoculated with the GT-48 strain of S. mirum and were exposed to regimens employed combined antibiotic and HBO treatments. The exclusive use of TMP/SMX produced a significant reduction in mortality (P less than 0.0001) and an absence of clinical signs of infection. HBO in combination with TMP/SMX showed similar effect on mortality and no evident clinical disease. The addition of HBO did result in a significant decrease in spiroplasma brain titres but was no more effective in preventing the spiroplasma-induced fatal microcystic encephalopathy than when the antibiotics were used alone. The exclusive use of HBO produced a catastrophic mortality rate in the spiroplasma-infected rats, which is contrary to the effect of HBO on conventional bacterial infections.