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.

Commensal Streptococcus mitis produces two different lipoteichoic acids of type I and type IV.

The opportunistic pathogen Streptococcus mitis possesses, like other members of the Mitis group of viridans streptococci, phosphorylcholine (P-Cho)-containing teichoic acids (TAs) in its cell wall. Bioinformatic analyses predicted the presence of TAs that are almost identical with those identified in the pathogen Streptococcus pneumoniae, but a detailed analysis of S. mitis lipoteichoic acid (LTA) was not performed to date.

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.

Draft Genome Sequences of Two Serotype 19A Sequence Type 226 Clinical Isolates from Hungary, Hu17 with High-Level Beta-Lactam Resistance and Hu15 of a Penicillin-Sensitive Phenotype.

The draft genome sequences of two multiple-antibiotic-resistant isolates from Hungary, Hu15 and Hu17, are reported here. Strain Hu15 is penicillin susceptible, whereas Hu17 is a high-level-penicillin-resistant strain. Both isolates belong to the serotype 19A sequence type 226, a single-locus variant (in the locus) of the Hungary-6 clone.

New Aspects of the Interplay between Penicillin Binding Proteins, , and the Two-Component System CiaRH of Penicillin-Resistant Streptococcus pneumoniae Serotype 19A Isolates from Hungary.

The clone Hungary-6 expresses unusually high levels of β-lactam resistance, which is in part due to mutations in the MurM gene, encoding a transferase involved in the synthesis of branched peptidoglycan. Moreover, it contains the allele , encoding the histidine kinase CiaH (M. Müller, P.

Roles of the Essential Protein FtsA in Cell Growth and Division in Streptococcus pneumoniae.

is an ovoid-shaped Gram-positive bacterium that grows by carrying out peripheral and septal peptidoglycan (PG) synthesis, analogous to model bacilli, such as and In the model bacilli, FtsZ and FtsA proteins assemble into a ring at midcell and are dedicated to septal PG synthesis but not peripheral PG synthesis; hence, inactivation of FtsZ or FtsA results in long filamentous cells unable to divide. Here, we demonstrate that FtsA and FtsZ colocalize at midcell in and that partial depletion of FtsA perturbs septum synthesis, resulting in elongated cells with multiple FtsZ rings that fail to complete septation. Unexpectedly, complete depletion of FtsA resulted in the delocalization of FtsZ rings and ultimately cell ballooning and lysis.

Promoter Identification and Transcription Analysis of Penicillin-Binding Protein Genes in Streptococcus pneumoniae R6.

Penicillin-binding proteins (PBPs) are membrane-associated enzymes, which are involved in the last two steps of peptidoglycan biosynthesis, and some of them are key players in cell division. Furthermore, they are targets of β-lactams, the most widely used antibiotics. Nevertheless, very little is known about the expression and regulation of PBP genes.

Highly Variable Streptococcus oralis Strains Are Common among Viridans Streptococci Isolated from Primates.

Viridans streptococci were obtained from primates (great apes, rhesus monkeys, and ring-tailed lemurs) held in captivity, as well as from free-living animals (chimpanzees and lemurs) for whom contact with humans is highly restricted. Isolates represented a variety of viridans streptococci, including unknown species. Streptococcus oralis was frequently isolated from samples from great apes.

Lipoteichoic acid of Streptococcus oralis Uo5: a novel biochemical structure comprising an unusual phosphorylcholine substitution pattern compared to Streptococcus pneumoniae.

Members of the Mitis group of streptococci possess teichoic acids (TAs) as integral components of their cell wall that are unique among Gram-positive bacteria. Both, lipoteichoic (LTA) and wall teichoic acid, are formed by the same biosynthetic pathway, are of high complexity and contain phosphorylcholine (P-Cho) residues. These residues serve as anchors for choline-binding proteins (CBPs), some of which have been identified as virulence factors of the human pathogen Streptococcus pneumoniae.

Mechanism of β-lactam action in Streptococcus pneumoniae: the piperacillin paradox.

The human pathogen Streptococcus pneumoniae has been treated for decades with β-lactam antibiotics. Its resistance is now widespread, mediated by the expression of mosaic variants of the target enzymes, the penicillin-binding proteins (PBPs). Understanding the mode of action of β-lactams, not only in molecular detail but also in their physiological consequences, will be crucial to improving these drugs and any counterresistances.

Penicillin-binding protein 2x of Streptococcus pneumoniae: the mutation Ala707Asp within the C-terminal PASTA2 domain leads to destabilization.

Streptococcus pneumoniae penicillin-binding protein 2x (PBP2x) is an enzyme involved in the last stages of peptidoglycan assembly and essential for bacterial growth and survival. PBP2x localizes to the division site, a process that depends on its Penicillin-Binding Protein And Serine-Threonine-kinase Associated (PASTA) domains, which was previously demonstrated via GFP-PBP2x in living cells. During this study a mutant strain was isolated in which the GFP-PBP2x fusion protein did not localize at division sites and it contained reduced amounts of the full-length GFP-PBP2x.

A low-affinity penicillin-binding protein 2x variant is required for heteroresistance in Streptococcus pneumoniae.

Heteroresistance to penicillin in Streptococcus pneumoniae is the ability of subpopulations to grow at a higher antibiotic concentration than expected from the MIC. This may render conventional resistance testing unreliable and lead to therapeutic failure. We investigated the role of the primary β-lactam resistance determinants, penicillin-binding protein 2b (PBP2b) and PBP2x, and the secondary resistance determinant PBP1a in heteroresistance to penicillin.

Streptococcus pneumoniae PBP2x mid-cell localization requires the C-terminal PASTA domains and is essential for cell shape maintenance.

The transpeptidase activity of the essential penicillin-binding protein 2x (PBP2x) of Streptococcus pneumoniae is believed to be important for murein biosynthesis required for cell division. To study the molecular mechanism driving localization of PBP2x in live cells, we constructed a set of N-terminal GFP-PBP2x fusions under the control of a zinc-inducible promoter. The ectopic fusion protein localized at mid-cell.

Biosynthesis of teichoic acids in Streptococcus pneumoniae and closely related species: lessons from genomes.

The cell wall of Streptococcus pneumoniae contains an unusually complex wall teichoic acid (WTA), which has identical repeating units as the membrane-anchored lipoteichoic acid (LTA). Both polymers share a common cytoplasmic pathway of precursor synthesis, but several TA enzymes have remained elusive. Bioinformatic analysis of the genome of various pneumococcal strains, including choline-independent mutant strains, has allowed us to identify the missing TA genes.

Molecular mechanisms of β-lactam resistance in Streptococcus pneumoniae.

Alterations in the target enzymes for β-lactam antibiotics, the penicillin-binding proteins (PBPs), have been recognized as a major resistance mechanism in Streptococcus pneumoniae. Mutations in PBPs that confer a reduced affinity to β-lactams have been identified in laboratory mutants and clinical isolates, and document an astounding variability of sites involved in this phenotype. Whereas point mutations are selected in the laboratory, clinical isolates display a mosaic structure of the affected PBP genes, the result of interspecies gene transfer and recombination events.

A new variant of the capsule 3 cluster occurs in Streptococcus pneumoniae from deceased wild chimpanzees.

The presence of new Streptococcus pneumoniae clones in dead wild chimpanzees from the Taï National Park, Côte d'Ivoire, with previous respiratory problems has been demonstrated recently by DNA sequence analysis from samples obtained from the deceased apes. In order to broadenour understanding on the relatedness of these pneumococcal clones to those from humans, the gene locus responsible for biosynthesis of the capsule polysaccharide (CPS) has now been characterized. DNA sequence analysis of PCR fragments identified a cluster named cps3(Taï) containing the four genes typical for serotype 3 CPS, but lacking a 5'-region of ≥2 kb which is degenerated in other cps3 loci and not required for type 3 biosynthesis.

Genome of Streptococcus oralis strain Uo5.

Streptococcus oralis, a commensal species of the human oral cavity, belongs to the Mitis group of streptococci, which includes one of the major human pathogens as well, S. pneumoniae. We report here the first complete genome sequence of this species.

The genome of Streptococcus mitis B6--what is a commensal?

Streptococcus mitis is the closest relative of the major human pathogen S. pneumoniae. The 2,15 Mb sequence of the Streptococcus mitis B6 chromosome, an unusually high-level beta-lactam resistant and multiple antibiotic resistant strain, has now been determined to encode 2100 genes.

Versatility of choline metabolism and choline-binding proteins in Streptococcus pneumoniae and commensal streptococci.

The pneumococcal choline-containing teichoic acids are targeted by cholinebinding proteins (CBPs), major surface components implicated in the interaction with host cells and bacterial cell physiology. CBPs also occur in closely related commensal species, Streptococcus oralis and Streptococcus mitis, and many strains of these species contain choline in their cell wall. Physiologically relevant CBPs including cell wall lytic enzymes are highly conserved between Streptococcus pneumoniae and S.

An important site in PBP2x of penicillin-resistant clinical isolates of Streptococcus pneumoniae: mutational analysis of Thr338.

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 also known.

Different pathways of choline metabolism in two choline-independent strains of Streptococcus pneumoniae and their impact on virulence.

The two recently characterized Streptococcus pneumoniae strains--R6Chi and R6Cho(-)--that have lost the unique auxotrophic requirement of this bacterial species for choline differ in their mechanisms of choline independence. In strain R6Chi the mechanism is caused by a point mutation in tacF, a gene that is part of the pneumococcal lic2 operon, which is essential for growth and survival of the bacteria. Cultures of lic2 mutants of the encapsulated strain D39Chi growing in choline-containing medium formed long chains, did not autolyze, had no choline in their cell wall, and were completely avirulent in the mouse intraperitoneal model.