Search

Background: Pneumococcal adherence to the nasopharyngeal epithelium is a critical step in colonisation and disease. The probiotic bacterium, Streptococcus salivarius, can inhibit pneumococcal adherence to epithelial cells in vitro. We investigated the mechanism(s) of inhibition using a human pharyngeal epithelial cell line (Detroit 562) following pre-administration of two different strains of S. salivarius. Results: Whilst the bacteriocin-encoding megaplasmids of S. salivarius strains K12 and M18 were essential to prevent pneumococcal growth on solid media, they were not required to inhibit pneumococcal adherence. Experiments testing S. salivarius K12 and two pneumococcal isolates (serotypes 19F and 6A) showed that inhibition of 19F may involve S. salivarius-mediated blocking of pneumococcal binding sites: a negative correlation was observed between adherence of K12 and 19F, and no inhibition occurred when K12 was prevented from contacting epithelial cells. K12-mediated inhibition of adherence by 6A may involve additional mechanisms, since no correlation was observed between adherence of K12 and 6A, and K12 could inhibit 6A adherence in the absence of cell contact. Conclusions: These results suggest that S. salivarius employs several mechanisms, including blocking pneumococcal binding sites, to reduce pneumococcal adherence to pharyngeal epithelial cells. These findings extend our understanding of how probiotics may inhibit pneumococcal adherence and could assist with the development of novel strategies to prevent pneumococcal colonisation in the future. [ABSTRACT FROM AUTHOR]

The colonization efficacies of salivaricin A (SalA)-producing Streptococcus salivarius strains 20P3 and 5 were compared when given in milk to 219 children, using either 2-day or 9-day dosing regimens. Colonization levels overall were superior for strain 5, and the 9-day dosing schedule resulted in higher levels of both initial colonization and strain persistence. The indigenous streptococcal tongue populations of 20 (10.9%) of the 189 children in the 2-day trial showed markedly increased SalA-like inhibitory activity following use of the S. salivarius-supplemented milk. All 20 of these children were found to have had relatively small (<5% of total S. salivarius) indigenous tongue populations of SalA-producing S. salivarius, and the relative proportions and/or inhibitory activity of these SalA producers on the childrens' tongues increased following ingestion of the S. salivarius-supplemented milk. Because SalA is known to be strongly inhibitory to Streptococcus pyogenes, an important implication of this study is that the consumption of SalA-producing probiotic S. salivarius could potentially help to effect a sustained increase in SalA-mediated protection against S. pyogenes infection. [ABSTRACT FROM AUTHOR]

Abstract: Streptococcus rattus strain BHT is a species representative and strong bacteriocin producer. Here we report that S. rattus BHT produces two quite different types of bacteriocin activity, named BHT-A and BHT-B. The two bacteriocins were purified and analysed for activity and by MALDI-TOF mass spectrophotometry. BHT-A was found to be a variant of the two-component lantibiotic, Smb. BHT-B is a non-modified 5195Da peptide with some similarity to the tryptophan-rich Staphylococcus aureus bacteriocin, aureocin A53. Six S. rattus and two S. mutans strains were found to contain both the BHT-A and BHT-B genetic loci. [Copyright &y& Elsevier]

The antibacterial peptide SA-FF22, produced by the pathogen Streptococcus pyogenes strain FF22 was purified and features of its primary and secondary structure were characterised. Mass spectrometry demonstrated the pure peptide had a mass of 2794Da while, amino acid analysis revealed the presence of the unusual, thioether amino acids lanthionine and 3-methyllanthionine; thus SA-FF22 is a member of the group of antibacterial polypeptides termed lantibiotics. Furthermore, amino acid sequencing showed a unique sequence which was blocked at position 23 by a residue of the unsaturated amino acid 2,3-didehydrobutyrine. Carboxypeptidase-Y digestion could be used to demonstrate that serine occupies the C-terminal position only after complete oxidation of the thioether amino acid bridges, suggesting that the three-dimensional structure of the native peptide may prevent access of the enzyme to the C-terminus. Fragmentation of the native peptide with a variety of proteolytic enzymes failed to yield a peptide containing less than all three of the cross-linked lanthionine and methyllanthionine residues and demonstrated that all three thioether bridges overlapped. Analysis of the circular dichroism of SA-FF22 in various concentrations of 2,2,2-trifluoroethanol in water, SDS micelles and in the presence of artificial phospholipid vesicles suggested that there is significant change in its secondary structure from aqueous to lipophilic environments. [ABSTRACT FROM AUTHOR]

Streptococcus uberis, a causal agent of bovine mastitis, produces ubericin A, a 5.3-kDa class IIa (pediocin-like) bacteriocin, which was purified and characterized. The uba locus comprises two overlapping genes: ubaA (ubericin A precursor peptide) and ubal (putative immunity protein). Ubericin A is the first streptococcal class ha bacteriocin to be characterized. [ABSTRACT FROM AUTHOR]

The article presents a study of new members to the antimicrobial proteins (bacteriocins) with modular structure from Gram-positive bacteria. It focuses on the heterologous expresssion of recombinant proteins accessed at the 17 kDa antibiotic protein SA-M57 from Streptococcus pyogenes with two unknown proteins from Enterococcus faecalis and YpkK from Corynebacterium jeikeium. These three antibiotic protein in different spectra of antimicrobial activity are shown in this study to have the ability of killing sensitive bacteria in nanomolar concentrations. Another activity of the proteins identified here is killing sensitive bacteria without lysis which sets them apart from known murolytic proteins.

The article focuses on the isolation and partial characterization of the Streptococcus mutans type AII lantibiotic mutacin K8. It was found that mutacin K8-encoding muk locus consists of 13 ORF, three of which have close homology to scnA, the structural gene encoding the Streptococcus pyogenes lantibiotic SA-FF22.

The article focuses on uberolysin, a novel cyclic bacteriocin produced by Streptococus uberis. It was called uberolysin because it induces the lysis of metabolically active, susceptible target bacteria. The isolation of the native active antimicrobial agent revealed that uberolysin is a 7048 Da peptide that is refractory to sequence analysis by Edman degradation.

The commercial probiotic Streptococcus salivarius strain K12 is the prototype of those S. salivarius strains that are the most strongly inhibitory in a standardized test of streptococcal bacteriocin production and has been shown to produce the 2,368-Da salivaricin A2 (SaIA2) and the 2,740-Da salivaricin B (SboB) lantibiotics. The previously uncharacterized SboB belongs to the type All class of lantibiotic bacteriocins and is encoded by an eight-gene cluster. The genetic loci encoding SalA2 and SboB in strain K12 have been fully characterized and are localized to nearly adjacent sites on pSsal-K12, a 190-kb megaplasmid. Of 61 strongly inhibitory strains of S. salivarius, 19 (31%) were positive for the sboB structural gene. All but one (strain NR) of these 19 strains were also positive for salA2, and in each of these cases of double positivity, the two loci were separated by fewer than 10 kb. This is the first report of a single streptococcus strain producing two distinct lantibiotics. [ABSTRACT FROM AUTHOR]

The article focuses on dysglalacticin, a novel bacteriocin produced by Streptococcus dysgalactiae subspecies equisimilis strain W2580 that has a narrow spectrum of antimicrobial activity directed primarily against the principal human streptococcal pathogen Streptococcus pyogenes. Dysgalacticin is a heat stable 21.5 kDa anionic protein that kills its target without inducing lysis.

Streptococcus mutans UA159, the genome sequence reference strain, exhibits nonlantibiotic mutacin activity. In this study, bioinformatic and mutational analyses were employed to demonstrate that the antimicrobial repertoire of strain UA159 includes mutacin IV (specified by the nim locus) and a newly identified bacteriocin, mutacin V (encoded by SMU.1914c). [ABSTRACT FROM AUTHOR]