[beta-lactam-antibiotics in the treatment of community-acquired respiratory tract infections with penicillin-resistant pneumococci].

Streptococcus pneumoniae is still the most important pathogen of community-acquired respiratory tract infections. During the last decades in many countries an increase in the spread of antibiotic resistant strains (e. g. against beta-lactams, macrolides, tetracyclin) was observed. Resistance against penicillin is often associated with resistance against macrolides and other antibiotic classes. In Germany surveillance studies including isolates from patients with community-acquired respiratory tract infections have shown that about 14 % of strains show a reduced susceptibility against penicillin (MIC-values 0.12 - 1 mg/L) and up to 4 % are highly resistant against penicillin (MIC >/= 2 mg/L). Resistance against tetracycline or macrolides was detected in up to 12 and 15 % of strains, respectively. According to the treatment guidelines of the Paul-Ehrlich-Gesellschaft für Chemotherapie and the Deutschen Atemwegsliga penicillins and cephalosporins are recommended as first line antibiotics for the treatment of community-acquired respiratory tract infections. As pneumococcal strains with reduced susceptibility against penicillin show often also a reduced susceptibility against cephalosporins the questions arises which beta-lactam antibiotics should still be used in empirical treatment of such strains. beta-Lactam-antibiotics highly differ in their in-vitro-activity against S. pneumoniae and their pharmacokinetic properties. In different models is has been demonstrated for beta-lactams that an adequate clinical and bacteriological efficacy is achievable when the serum levels of the free, i. e. not protein bound fraction of drug exceeds the MIC of the pathogen for at least 40 to 50 % of the dosing interval (T > MIC). In a clinical situation where pneumococci with reduced susceptibility against penicillin cannot be ruled out, only beta-lactam antibiotics with favourable pharmacological properties (good in-vitro activity, high and long lasting serum levels) should be used for treatment.