Abstract
Abstract: :
Purpose: To determine the in vitro antibiotic resistant trends for common antibiotics used for the treatment of conjunctivitis. Methods: In a prospective study using stock isolates, disk diffusion susceptibility (NCCLS breakpoint interpretation) was determined for 3 groups of bacterial conjunctivitis isolates (Staphylococcus aureus, Streptococcus pneumoniae, and Haemophilus influenzae) to moxifloxacin (Mx), bacitracin (B), erythromycin (E), gentamicin (Gm), tobramycin (Tb), neomycin (Ne), ciprofloxacin (Cp), ofloxacin (Of), levofloxacin (Lv), trimethoprim (Tri), polymyxin B (PB), sulfa (S), and oxacillin (Ox–SA only). Antibiotic susceptibility was determined for two consecutive periods (1999 to 2004) and (1996 to 1999). Consecutive isolates were chosen from the most recent available for each period. The number of isolates for each bacterial group in the first period was 50 and 30 were used in the second period. Cumulative susceptibility for each period was compared and designated as increase, decrease, or no change in resistance. Results: Streptococcus pneumoniae – Resistance increased for 6 antibiotics (50%) (B, E, Gm, Tri, Pb, S), decreased for 4 (33%) (Cp, Of, Tb, and Lv), and there was no change for 2 (17%) (Mx, Ne). Staphylococcus aureus – Resistance increased for 4 (31%) (E, Pb, B, Ne), decreased for 7 (54%) (Mx, Tb, Gm, Tri, Of, Ox, Lv), and there was no change for 2 (15%) (S, Cp). Haemophilus influenzae – Resistance increased for 8 antibiotics (66%) (E, Of, Tri, Pb, Tb, S, Lv, Ne), decreased for 2 (17%) (B, Gm), and there was no change for 2 (17%) (Mx, Cp). Conclusions: Although there were trends of increased antibiotic resistance, some antibiotics noted a decrease in resistance and other antibiotics demonstrated no change in resistance. Recently–introduced topical moxifloxacin, lacking significant selection factors, demonstrated high susceptibility (100%) for St. pneumoniae and H. influenzae, and the highest susceptibility (82%) amongst the tested fluoroquinolones for S. aureus.