The effects of inactivation of the genes encoding penicillin-binding protein 1a (PBP1a), PBP1b, and PBP2a in Streptococcus pneumoniae were examined. Insertional mutants did not exhibit detectable changes in growth rate or morphology, although a pbp1a pbp1b double-disruption mutant grew more slowly than its parent did. Attempts to generate a pbp1a pbp2a double-disruption mutant failed. The pbp2a...

We investigated the roles of the Vibrio cholerae high-molecular-weight bifunctional penicillin binding proteins, PBP1a and PBP1b, in the fitness of this enteric pathogen. Using a screen for synthetic lethality, we found that the V. cholerae PBP1a and PBP1b proteins, like their Escherichia coli homologues, are each essential in the absence of the other and in the absence of the other's putative ...

One group of penicillin target enzymes, the class A high-molecular-weight penicillin-binding proteins (PBPs), are bimodular enzymes. In addition to a central penicillin-binding-transpeptidase domain, they contain an N-terminal putative glycosyltransferase domain. Mutations in the genes for each of the three Streptococcus pneumoniae class A PBPs, PBP1a, PBP1b, and PBP2a, were isolated by inserti...

A seminested PCR assay, based on the amplification of the pneumococcal pbp1A gene, was developed for the detection of penicillin resistance in clinical isolates of Streptococcus pneumoniae. The assay was able to differentiate between intermediate (MICs = 0.25 to 0.5 microgram/ml) and higher-level (MICs = >/=1 microgram/ml) resistance. Two species-specific primers, 1A-1 and 1A-2, which amplified...

The bacterial cell wall, which is comprised of a mesh of polysaccharide strands crosslinked via peptide bridges (peptidoglycan, PG), is critical for maintenance of cell shape and survival. PG assembly is mediated by a variety of Penicillin Binding Proteins (PBP) whose fundamental activities have been characterized in great detail; however, there is limited knowledge of the factors that modulate...

Most Helicobacter pylori strains are susceptible to amoxicillin, an important component of combination therapies for H. pylori eradication. The isolation and initial characterization of the first reported stable amoxicillin-resistant clinical H. pylori isolate (the Hardenberg strain) have been published previously, but the underlying resistance mechanism was not described. Here we present evide...

OBJECTIVES To investigate the Helicobacter pylori amoxicillin resistance rate, the occurrence of heteroresistance, and their related molecular mechanisms. METHODS Eighty-seven H. pylori-positive patients were included: 45/87 with single biopsy and 42/87 with multiple biopsies. MICs were determined, and sequencing analysis of pbp1A gene and the variable regions of seven hop porins was performe...

Streptococcus mutans, a key etiological agent of human dental caries, lives almost exclusively on the tooth surface in plaque biofilms and is known for its ability to survive and respond to various environmental insults, including low pH, and antimicrobial agents from other microbes and oral care products. In this study, a penicillin-binding protein (PBP1a)-deficient mutant, strain JB467, was g...

The bacterial cell envelope contains the stress-bearing peptidoglycan layer, which is enlarged during cell growth and division by membrane-anchored synthases guided by cytoskeletal elements. In Escherichia coli, the major peptidoglycan synthase PBP1A requires stimulation by the outer-membrane-anchored lipoprotein LpoA. Whereas the C-terminal domain of LpoA interacts with PBP1A to stimulate its ...

Penicillin-binding protein 2x (PBP2x) of Streptococcus pneumoniae represents a primary resistance determinant for beta-lactams, and low-affinity PBP2x variants can easily be selected with cefotaxime. Penicillin-resistant clinical isolates of S. pneumoniae frequently contain in their mosaic PBP2x the mutation T338A adjacent to the active site S337, and T338P as well as T338G substitutions are al...