| Summary: | Increases in the prevalence of penicillin-nonsusceptible ' Streptococcus pneumoniae' can be attributed to the acquisition of altered penicillin-binding protein (PBP) genes and to the geographic spread of genetically related isolates with elevated B-lactam minimum inhibitory concentrations (MICs). The objective of this thesis was to characterize ' pbp1a, pbp2b' and 'pbp2x' mutations in Canadian isolates of penicillin-nonsusceptible 'S. pneumoniae' and to evaluate the relationship between genetic diversity and penicillin susceptibility as it pertains to the dissemination of resistance. Both pulsed-field gel electrophoresis (PFGE) and arbitrarily-primed PCR (AP-PCR) revealed homogeneity amongst penicillin-resistant isolates and exclusive heterogeneity amongst penicillin-intermediate and penicillin-susceptible isolates. Four penicillin-resistant isolates with homogenous typing profiles serotyped 19F, 23F and 14, indicating several instances of probable capsular serotype switching. Sequence analysis of the penicillin-binding domains of ' pbp1a, pbp2b' and 'pbp2x' revealed identical nucleotide and amino acid substitution patterns in all isolates with penicillin MICs >=1 [mu]g/ml. (Abstract shortened by UMI.)
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