PubMed · 2022781
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1991. Preventing bacterial endocarditis. Correction.. https://pubmed.ncbi.nlm.nih.gov/2022781/
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Genetic, biochemical, and structural data support an essential role for the ribosomal RNA in all steps of the translation process. Although in vivo genetic selection techniques have been used to identify mutations in the rRNAs that result in various miscoding phenotypes and resistance to known ribosome-targeted antibiotics, these are limited because the resulting mutant ribosomes must be only marginally disabled if they are able to support growth of the cell. Furthermore, in vivo, it is not possible to control the environment in precise ways that might allow for the isolation of certain types of rRNA variants. To overcome these limitations, we have developed an in vitro selection system for the isolation of functionally competent ribosomal particles from populations containing variant rRNAs. Here, we describe this system and present an example of its application to the selection of antibiotic resistance mutations. From a pool of 4,096 23S rRNA variants, a double mutant (A2058U/A2062G) was isolated after iteration of the selection process. This mutant was highly resistant to clindamycin in in vitro translation reactions and yet was not viable in Escherichia coli. These data establish that this system has the potential to identify mutations in the rRNA not readily accessed by comparable in vivo systems, thus allowing for more exhaustive ribosomal genetic screens.
OBJECTIVE: Streptococcus species are common pathogens in head and neck infections and are leading causes of morbidity and mortality. Emerging penicillin-resistant streptococcal pathogens have shifted empirical antibiotic therapy in favor of valuable alternatives, including erythromycin and clindamycin. This study was undertaken to determine the magnitude of antimicrobial resistance to these antibiotics. STUDY DESIGN: Retrospective review. METHODS: A retrospective study of two streptococcal species isolates, Streptococcus pyogenes (163 specimens) and Streptococcus pneumoniae (164 specimens), collected between January 1, 2001 and January 1, 2002 at two academic institutions. The antibiotic susceptibility patterns were analyzed for penicillin, erythromycin, and clindamycin according to the National Committee for Clinical Laboratory Standards. RESULTS: Fourteen percent to 34% of S. pyogenes isolates were erythromycin-resistant, and 0% to 28% were clindamycin-resistant. None of the S. pyogenes isolates were resistant to penicillin. Of the S. pneumoniae isolates, 33% to 50% were resistant to erythromycin, and 18% to 33% were resistant to clindamycin. The penicillin resistance levels for S. pneumoniae were 0% to 45%. CONCLUSIONS: Our antimicrobial resistance levels for S. pyogenes and S. pneumoniae significantly exceeded national and worldwide levels of erythromycin and clindamycin resistance. With a diverse population of over 8 million residents and high physician supply, our model is a microcosm for the study of antimicrobial use and susceptibility patterns and of clinical failure.
A prospective study of erythromycin and clindamycin resistance was performed with 304 consecutive group B streptococci (GBS) isolates. According to two automated susceptibility testing systems, Vitek-1 and Vitek-2, and double-disk agar diffusion, 79.9% were susceptible to both erythromycin and clindamycin. However, for macrolide-lincosamide-streptogramin B-inducible isolates, the accuracies of the Vitek-1 and Vitek-2 systems were 5.6 and 94.4%. In light of these results, we recommend that GBS be routinely tested using the double-disk diffusion method.