Effect of chronic systemic use of Trimethoprim –Sulfamethoxazole in the Conjunctival Bacterial Flora of HIV– Infected patients

Abstract

Abstract: : Purpose : To investigate the effect of orally administered Trimethoprim–Sulfamethoxazole (TMP–SMZ) on the prevalence, species distribution and resistance of the aerobic ocular conjunctival bacterial flora in HIV–infected adults under highly active antiretroviral therapies (HAART). Methods : Cross–sectional study, with descriptive and analytic components. Samples from the inferior conjunctival fornix of consecutive patients were collected and submitted to cultures in order to evaluate aerobic ocular conjunctival flora. Microorganisms were identified and antibiotic susceptibility was tested to each bacteria. Results : Samples of sixty eyes from thirty HIV infected patients, divided in two groups related or not to the use of TMP–SMZ, were collected from March to August 2003. Negative cultures were found in 17 (56,7%) eyes of the study group, and in 10 (33%) of the control group (p= 0.036). All the coagulase–negative Staphylococcus isolates in the TMP–SMZ group were resistant to this drug, whereas 50% of the control group presented such characteristic (p=0.025). On the study group all bacterias (100%) were resistant to TMP–SMZ, and only 47% of the microorganisms in the control group. Overall, antimicrobial resistance was uncommon for others antibiotics tested in both groups. Conclusions : Oral administered TMP–SMZ in HIV infected patients seems to reach an adequate concentration on the conjunctiva, exerting a selection pressure in the microorganisms, both decreasing the bacterial growth and increasing local resistance to this antibiotic.

Keywords: antibiotics/antifungals/antiparasitics • clinical laboratory testing • AIDS/HIV