Active substances: Norfloxacin
Molecular assays for several resistance markers are reliable, such as mecA in staphylococci and vanA in enterococci 39. For other resistance markers, there is currently a lack of field testing.
Du Plessis et al. Penicillin resistance was demonstrated in laboratory mutants soon after the introduction of penicillin G into clinical use but was not reported in clinical strains until 20 years later when investigators in Boston reported penicillin resistance in 2 of 200 strains 45.
Initially, the observation was not considered relevant, until Hansman and Bullen 46 gave a report describing a penicillin-resistant strain MIC 0.
Subsequently, resistant strains were identified in New Guinea and Australia and in 1974 the first clinical infection due to a penicillin nonsusceptible strain was reported in the Unites States 47.
In 1977 pneumococci resistant to penicillin began to appear in South Africa and in 1978, the first multidrug-resistant pneumococci were documented in Johannesburg, South Africa 20. In between and after these initial reports, detection of penicillin-resistant pneumococci among clinical isolates began to be reported with increasing frequency in the clinical and microbiological setting.
Today, penicillin-resistant strains are encountered in all countries in which adequate surveys are conducted and an increasing number of countries are reporting a high prevalence of penicillin-resistant pneumococci.
Six PBPs have been identified in S. In general, the resistance profile of particular isolates results from interactions between various combinations of altered PBPs, in conjunction with a functional murMN operon which encodes enzymes involved in the synthesis of branched structured muropeptides.
In certain countries, such as the United States 78, active efflux is the major mechanism for macrolide resistance. This efflux in S.
Important differences however exist between these two variants and recent data shows that the two genes have disseminated differently and are being recognized in an ever-growing number of microbial species 82.
Worldwide erm B and mef A or E mechanisms account for the majority of macrolide resistance among pneumococci and the prevalence of these genes varies considerably among countries.
Some macrolide-resistant S.