Evolution of antibiotic resistance in bacteria involved in community-acquired pneumopathies

Micro-organisms such as Haemophilus influenzae and, above all, Streptococcu s pneumoniae are often responsible for antibiotic resistance in acute commu nity-acquired pneumopathies. Current resistance of H. influenzae to beta -l actams is estimated at 35% of the strains and is steadily increasing. Its m echanisms are due to the production of beta -lactamases, mainly TEM-1. Thus , the gold-standard treatment includes either a combination of amoxicillin with a beta -lactamase inhibitor or an oral cephalosporin resistant to thes e enzymes. An other mechanism of resistance to beta -lactams is due to the alteration of penicillin binding proteins (PBP) but its incidence is low (1 -3%). Acquired resistance to other antimicrobial agents is still low, excep t for cotrimoxazole. In France, since 1987 S. pneumoniae has shown a dramat ic increase of resistance to penicillin, resulting from two distinct mechan isms: clonal spreading of resistant strains and horizontal transfer of gene s coding for altered PBF! In France, the current prevalence of penicillin-r esistant S, pneumoniae (PRSP) is estimated at 48% of the strains, 58.5% of which exhibit MIC > 1 mg/L. For oral beta -lactamins, amoxicillin has the l owest MICs against these resistant strains. For parenteral cephalosporins, cefotaxime, ceftriaxone, and imipenem are the most potent, and resistance t o these antibiotics is rare in France. Most PRSP strains (75%) currently sh ow multiresistance to other antibiotics, particularly to macrolides and cyc lins. However, resistance to penicillin does not give therapeutic failures in clinical practice, since plasmatic concentrations largely exceed MICs of resistant germs. Therefore, penicillin G or amoxicillin are still promoted as first line therapies. (C) 2001 Editions scientifiques et medicales Else vier SAS