Prevalence of antimicrobial resistance in Streptococcus pneumoniae circulating in Italy: Results of the Italian Epidemiological Observatory survey (1997-1999)

The Italian Epidemiological Observatory (IEO), a surveillance program suppo rted by the SmithKline Foundation, analyzed the susceptibility of 2,664 com munity-acquired respiratory Streptococcus pneumoniae derived from over 50 c linical microbiology laboratories during 1997-1999, against 21 antibiotics adopting a quantitative methodology. Throughout these years, total penicill in resistance varied from 14.3% to 10.2%. High-level resistance has remaine d stable, ranging from 3.8% to 4.1%, while a decrease in low-level resistan ce (from 10.3% to 6.1%) has been recorded. Lack of susceptibility to macrol ides ranged from 29.1% in 1997 to 25.5% in 1999. Similar figures have also been observed with tetracycline and co-trimoxazole (rates of resistance aro und 30%). As expected, large geographical variations in resistance rates we re found for all drugs. Amoxicillin and amoxicillin-clavulanate were 100% a ctive on penicillin-intermediate isolates. Injectable third-generation ceph alosporins and carbapenems, were also capable of inhibiting a large proport ion of these microorganisms. Rifampin was the most potent non-beta -lactam compound tested. In contrast to the situation prevailing elsewhere, in Ital ian children (aged 0-5 years) presenting with respiratory conditions, the t otal rate of penicillin resistance (3%) was lower than that shown by the ad ult population (10.9%). However, lack of susceptibility to macrolides, tetr acycline, and cotrimoxazole (35%, 41%, 44%) was more incident in pediatric than in adult patients (25%, 26%, 28% respectively). Strains recovered from blood in 1999 (67) were much more susceptible to penicillin (98.5%) than r espiratory pneumococci (89.8%), whereas macrolides, tetracycline, and cotri moxazole were consistently, less active (75%, 67%, 64%).