[Antibiotic therapy for community acquired Streptococcus pneumoniae pneumonia: clinical relevance of antibiotic resistance]

Abstract

The emergence of Streptococcus pneumoniae strains with reduced susceptibility to beta-lactams and with multiple drug resistance has not led to major changes in recommendations for antibiotic therapy in patients with acute community-acquired pneumococcal pneumonia. Numerous factors explain the limited clinical impact of this major microbiological change. The frequency of intermediate strains is high but the frequency of resistant strains to beta-lactams is very low. There is a complex relation between the acquisition of resistance to beta-lactams and the decreased virulence of S. pneumoniae strains. The only finding in studies of humanized experimental animal models of lethal bacteremic pneumonia caused by resistance and tolerant strains was a slowing in the kinetics of beta-lactams bactericidal activity, especially for amoxicillin. Taken together, this preclinical data shows that microbiological resistance of pneumococci to beta-lactams has very little influence on a possible failure of recommanded treatment regimens for pneumococcal pneumonia. The high rate of multiple drug resistance, particularly among beta-lactam resistant strains, rules out the probabilistic use of macrolides. Conversely, fluoroquinolone (FQ) resistance remains low, inferior to 3%, and the same is true for ketolides (<1%). Only a global strategy of patient management in the use of these new drugs could ensure their long-term activity. The high mortality rate of hospitalized S. pneumoniae pneumonia will only be improved with a better understanding of the complex host-bacteria interactions.