RESUMEN
Antimicrobial resistance among clinical isolates of Streptococcus pneumoniae (n = 49), Haemophilus influenzae (n = 66) and Moraxella catarrhalis (n = 25) from adults with community-acquired lower respiratory tract infections (CALRTI) was assessed in a national surveillance study in Southern Estonia during 2000-2003. In S. pneumoniae, no penicillin resistance and only 2.0% resistance to clarithromycin was present, although intermediate resistance to trimethoprim-sulphamethoxazole (TMP-SMX) reached 24.5%. Beta-lactamase production rate was 96.0% in M. catarrhalis, but only 3.0% in H. influenzae. Both Gram-negative strains lacked resistance to ciprofloxacin. Clarithromycin resistance was 12% in M. catarrhalis but lacking among H. influenzae (except for 18.2% intermediate resistance). Resistance to TMP-SMX was 12.0% and 24.2% in M. catarrhalis and H. influenzae, respectively. In summary, a favorable resistance pattern of the main CALRTI pathogens is preserved in Estonia to core antibacterials. Nevertheless, use of TMP-SMX in CALRTI is discouraged and clinical response should be carefully monitored, when clarithromycin is chosen against M. catarrhalis or H. influenzae.