ANTIBIOTIC-RESISTANT PNEUMOCOCCI

In 1875, 7 years prior to the description of the Koch bacillus, Klebs visualized the first Streptococcus pneumoniae in pleural fluid. Since then, this organism has played a decisive role in biomedical science. From a biological point of view, it was extensively involved in the de velopment of passive and active immunization by serotherapy and vaccin ation respectively. Genetic transformation was also first observed in S. pneumoniae, leading to the discovery of DNA. From a clinical point of view, S. pneumoniae is today still a prime cause of otitis media in children and of pneumonia in all age groups, as well as a predominant cause of meningitis and bacteremia. In adults, bacteremia still has a mortality of over 25%. Although S. pneumoniae remained very sensitive to penicillin for many years, penicillin-resistant strains have emerg ed and increased dramatically over the last 15 years. During this peri od the frequency of penicillin-resistant isolates has increased from l ess than or equal to 1% to frequencies varying from 20 to 60% in geogr aphic areas as diverse as South Africa, Spain, France, Hungary, Icelan d, Alaska, and numerous regions of the United States and South America . In Switzerland, the current frequency of penicillin-resistant pneumo cocci ranges between 5 and greater than or equal to 10%. The increase in penicillin-resistant pneumococci correlates with the intensive use of beta-lactam antibiotics. The mechanism of resistance is not due to bacterial production of penicillinase but to an alteration of the bact erial target of penicillin, the so-called penicillin-binding proteins. Resistance is subdivided into (1) intermediate level resistance (mini mal inhibitory concentration [MTC] of penicillin of 0.1-1 mg/l) and (2 ) high level resistance (MCI greater than or equal to 2 mg/l). The cli nical significance of intermediate resistance remains poorly defined. On the other hand, highly resistant strains have been responsible for numerous therapeutic failures, especially in cases of meningitis. Anti biotics recommended against penicillin-resistant pneumococci include c efotaxime, ceftriaxone, imipenem and in some instances vancomycin. How ever, penicillin-resistant pneumococci tend to present cross-resistanc es to all the antibiotics of the beta-lactam family and could even bec ome resistant to the last resort drugs mentioned above. Thus, the expl osion of resistance to penicillin in pneumococci is a ubiquitous pheno menon which must be fought against by (1) avoiding excessive use of an tibiotics, (2) the practice of microbiological sampling of infected fo ci before treatment, (3) the systematic surveillance of resistance pro files of pneumococci against antibiotics and (4) adequate vaccination of populations at risk.