Current perspectives on Streptococcus pneumoniae antibiotic resistance, with particular reference to isolates from Spain

Abstract

Pneumococcal antibiotic resistance has become general throughout the world, although in Spain resistance rates are particularly high. In 1979, reference was made to the fact that in this country 6% of pneumococcal strains were not susceptible to penicillin. Rates of penicillin resistance increased continuously in the following years, reaching values up to 44.3% among invasive strains in 1989. In data referring to the period 1997–2001, using pneumococcal isolate strains from 113 Spanish hospitals and the NCCLS-2000 breakpoints, 47.5% of the strains showed diminished susceptibility to penicillin, 7.8% to amoxicillin, 21.3% to cefotaxime, 38.3% to tetracycline, 22.1% to chloramphenicol, and 34.8% to erythromycin. The minimum inhibitory concentration90 for amoxicillin was 2 μg/mL, 1 μg/mL for cefotaxime, and equal to or more than 128 μg/mL for erythromycin.

One of the main factors that has been related to this steady increase in resistance has been antibiotic consumption outside of the hospital. Although antibiotic use in an outpatient basis is high in Spain, particularly that of quinolones, a constant decrease has been noted since 1997.

Concerning the repercussions that this resistance may have on the outcome of patients, some authors have described treatment failures when using macrolides to treat a pneumococcal infection caused by a macrolide-resistant strain (minimum inhibitory concentrations ≥4 μg/mL). Given their pharmacokinetic characteristics, it is generally accepted that high doses of β-lactams or fluoroquinolones (active against gram-positive pathogens) are still safe drugs to use when treating pneumococcal pneumonia.