New Insights into Beta-Lactam Resistance of : Serine Protease HtrA Degrades Altered Penicillin-Binding Protein 2x.

Reduced amounts of the essential penicillin-binding protein 2x (PBP2x) were detected in two cefotaxime-resistant laboratory mutants C405 and C606. These mutants contain two or four mutations in the penicillin-binding domain of PBP2x, respectively. The transcription of the gene was not affected in both mutants; thus, the reduced PBP2x amounts were likely due to post-transcriptional regulation.

PBP2a in β-Lactam-Resistant Laboratory Mutants and Clinical Isolates: Disruption Versus Reduced Penicillin Affinity.

Alterations in PBP2a have been recognized in cefotaxime-resistant laboratory mutants and β-lactam-resistant clinical isolates of Streptococcus pneumoniae. DNA sequencing revealed fundamental differences between these two settings. Internal stop codons in pbp2a occurred in all three laboratory mutants analyzed, caused by a mutation in pbp2a of mutant C604, and tandem duplications within pbp2a resulting in premature stop codons in another two mutants C403 and C406.

Diversity of Mosaic Families in Penicillin-Resistant Streptococcus pneumoniae from Iran and Romania.

Penicillin-resistant strains are found at high rates in Romania and Iran. The mosaic structure of PBP2x was investigated in 9 strains from Iran and in 15 strains from Romania to understand their evolutionary history. Mutations potentially important for β-lactam resistance were identified by comparison of the PBP2x sequences with the sequence of the related PBP2x of reference penicillin-sensitive strains.

Long Persistence of a 23F Clone in a Cystic Fibrosis Patient.

isolates of serotype 23F with intermediate penicillin resistance were recovered on seven occasions over a period of 37 months from a cystic fibrosis patient in Berlin. All isolates expressed the same multilocus sequence type (ST), ST10523. The genome sequences of the first and last isolates, D122 and D141, revealed the absence of two phage-related gene clusters compared to the genome of another ST10523 strain, D219, isolated earlier at a different place in Germany.