Routine antibiotics appear ineffective for toxoplasma retinochoroiditis

This literature review found a lack of level I evidence to support routine antibiotic or corticosteroid treatment for immunocompetent patients with acute toxoplasma retinochoroiditis (TRC). However, level II evidence from a single study suggested that long-term prophylactic treatment with combined trimethoprim and sulfamethoxazole may reduce recurrences in patients with recurrent TRC.

These findings should be interpreted with caution. A lack of evidence for treatment means that a randomized placebo-controlled trial is needed. Until more information is available, physicians must rely on their clinical judgment. Patients with vision-threatening lesions may still benefit from treatment, and this study does not suggest that antibiotics should be withheld. A patient's degree of immunosuppression should be considered when determining whether or not to treat. As with all medications, patients should be carefully monitored for allergy or side effects. 

Eight of the 11 studies reviewed were randomized controlled studies, and none of them demonstrated that routine antibiotic or corticosteroid treatment of TRC favorably affects visual outcomes or reduces lesion size. Adverse effects of antibiotic treatment were reported in as many as 25 percent of patients, mostly as a result of bone-marrow suppression and allergic reactions. There was no evidence supporting the efficacy of other nonmedical treatments, such as laser photocoagulation.

The authors note that the study's investigators and subjects were unmasked and that other strains of T gondii may respond differently to treatment. Equally important, there is no convincing evidence to date that treatment decreases the severity of intraocular inflammation or duration of disease for all patients.

They also note that this lack of conclusive clinical evidence of the effectiveness of antibiotics is in contrast to data from animal studies that demonstrate that antimicrobial drugs are highly effective for treating active toxoplasmosis. Although a treatment effect has been difficult to find in immunocompetent hosts, one has been shown more convincingly in immunosuppressed patients with AIDS. Furthermore, studies have suggested that long-term treatment of newborns with congenital toxoplasmosis for up to one year using pyrimethamine and sulfadiazine reduced the risk of developing TRC when compared with historical untreated controls.