July 7, 2019  |  

Complete genome sequences of three multidrug-resistant clinical isolates of Streptococcus pneumoniae serotype 19A with different susceptibilities to the myxobacterial metabolite carolacton.

The full-genome sequences of three drug- and multidrug-resistant Streptococcus pneumoniae clinical isolates of serotype 19A were determined by PacBio single-molecule real-time sequencing, in combination with Illumina MiSeq sequencing. A comparison to the genomes of other pneumococci indicates a high nucleotide sequence identity to strains Hungary19A-6 and TCH8431/19A. Copyright © 2017 Donner et al.

July 7, 2019  |  

Genome evolution to penicillin resistance in serotype 3 Streptococcus pneumoniae by capsular switching.

Streptococcus pneumoniae isolates of serotype 3 were collected from cases of invasive pneumococcal disease (n= 124) throughout Japan between April 2010 and March 2013. A penicillin-resistantS. pneumoniae(PRSP) isolate from an adult patient, strain KK0981 of serotype 3, was identified among these strains. Whole-genome analysis characterized this PRSP as a recombinant strain derived from PRSP of serotype 23F with thecpslocus (20.3 kb) replaced by that of a penicillin-susceptible strain of serotype 3. Copyright © 2017 American Society for Microbiology.

July 7, 2019  |  

Gene acquisition by a distinct phyletic group within Streptococcus pneumoniae promotes adhesion to the ocular epithelium.

Streptococcus pneumoniae (pneumococcus) displays broad tissue tropism and infects multiple body sites in the human host. However, infections of the conjunctiva are limited to strains within a distinct phyletic group with multilocus sequence types ST448, ST344, ST1186, ST1270, and ST2315. In this study, we sequenced the genomes of six pneumococcal strains isolated from eye infections. The conjunctivitis isolates are grouped in a distinct phyletic group together with a subset of nasopharyngeal isolates. The keratitis (infection of the cornea) and endophthalmitis (infection of the vitreous body) isolates are grouped with the remainder of pneumococcal strains. Phenotypic characterization is consistent with morphological differences associated with the distinct phyletic group. Specifically, isolates from the distinct phyletic group form aggregates in planktonic cultures and chain-like structures in biofilms grown on abiotic surfaces. To begin to investigate the association between genotype and epidemiology, we focused on a predicted surface-exposed adhesin (SspB) encoded exclusively by this distinct phyletic group. Phylogenetic analysis of the gene encoding SspB in the context of a streptococcal species tree suggests that sspB was acquired by lateral gene transfer from Streptococcus suis. Furthermore, an sspB deletion mutant displays decreased adherence to cultured cells from the ocular epithelium compared to the isogenic wild-type and complemented strains. Together these findings suggest that acquisition of genes from outside the species has contributed to pneumococcal tissue tropism by enhancing the ability of a subset of strains to infect the ocular epithelium causing conjunctivitis. IMPORTANCE Changes in the gene content of pathogens can modify their ability to colonize and/or survive in different body sites in the human host. In this study, we investigate a gene acquisition event and its role in the pathogenesis of Streptococccus pneumoniae (pneumococcus). Our findings suggest that the gene encoding the predicted surface protein SspB has been transferred from Streptococcus suis (a distantly related streptococcal species) into a distinct set of pneumococcal strains. This group of strains distinguishes itself from the remainder of pneumococcal strains by extensive differences in genomic composition and by the ability to cause conjunctivitis. We find that the presence of sspB increases adherence of pneumococcus to the ocular epithelium. Thus, our data support the hypothesis that a subset of pneumococcal strains has gained genes from neighboring species that enhance their ability to colonize the epithelium of the eye, thus expanding into a new niche.

July 7, 2019  |  

Lysosomal Cathepsin A plays a significant role in the processing of endogenous bioactive peptides.

Lysosomal serine carboxypeptidase Cathepsin A (CTSA) is a multifunctional enzyme with distinct protective and catalytic function. CTSA present in the lysosomal multienzyme complex to facilitate the correct lysosomal routing, stability and activation of with beta-galactosidase and alpha-neuraminidase. Beside CTSA has role in inactivation of bioactive peptides including bradykinin, substances P, oxytocin, angiotensin I and endothelin-I by cleavage of 1 or 2 amino acid(s) from C-terminal ends. In this study, we aimed to elucidate the regulatory role of CTSA on bioactive peptides in knock-in mice model of CTSA(S190A) . We investigated the level of bradykinin, substances P, oxytocin, angiotensin I and endothelin-I in the kidney, liver, lung, brain and serum from CTSA(S190A) mouse model at 3- and 6-months of age. Our results suggest CTSA selectively contributes to processing of bioactive peptides in different tissues from CTSA(S190A) mice compared to age matched WT mice.

July 7, 2019  |  

Neuraminidase A-exposed galactose promotes Streptococcus pneumoniae biofilm formation during colonization.

Streptococcus pneumoniae is an opportunistic pathogen that colonizes the nasopharynx. Herein we show that carbon availability is distinct between the nasopharynx and bloodstream of adult humans: glucose is absent from the nasopharynx, whereas galactose is abundant. We demonstrate that pneumococcal neuraminidase A (NanA), which cleaves terminal sialic acid residues from host glycoproteins, exposed galactose on the surface of septal epithelial cells, thereby increasing its availability during colonization. We observed that S. pneumoniae mutants deficient in NanA and ß-galactosidase A (BgaA) failed to form biofilms in vivo despite normal biofilm-forming abilities in vitro Subsequently, we observed that glucose, sucrose, and fructose were inhibitory for biofilm formation, whereas galactose, lactose, and low concentrations of sialic acid were permissive. Together these findings suggested that the genes involved in biofilm formation were under some form of carbon catabolite repression (CCR), a regulatory network in which genes involved in the uptake and metabolism of less-preferred sugars are silenced during growth with preferred sugars. Supporting this notion, we observed that a mutant deficient in pyruvate oxidase, which converts pyruvate to acetyl-phosphate under non-CCR-inducing growth conditions, was unable to form biofilms. Subsequent comparative transcriptome sequencing (RNA-seq) analyses of planktonic and biofilm-grown pneumococci showed that metabolic pathways involving the conversion of pyruvate to acetyl-phosphate and subsequently leading to fatty acid biosynthesis were consistently upregulated during diverse biofilm growth conditions. We conclude that carbon availability in the nasopharynx impacts pneumococcal biofilm formation in vivo Additionally, biofilm formation involves metabolic pathways not previously appreciated to play an important role. Copyright © 2016, American Society for Microbiology. All Rights Reserved.

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