Genetic Analysis of Mutacin B-Ny266, a Lantibiotic Active against Caries Pathogens.

Bacteriocins are ribosomally synthesized proteinaceous antibacterial peptides. They selectively interfere with the growth of other bacteria. The production and secretion of bacteriocins confer a distinct ecological advantage to the producer in competing against other bacteria that are present in the same ecological niche. Streptococcus mutans, a significant contributor to the development of dental caries, is one of the most prolific producers of bacteriocins, known as mutacins in S. mutans In this study, we characterized the locus encoding mutacin B-Ny266, a lantibiotic with a broad spectrum of activity. The chromosomal locus is composed of six predicted operon structures encoding proteins involved in regulation, antimicrobial activity, biosynthesis, modification, transport, and immunity. Mutacin B-Ny266 was purified from semisolid cultures, and two inhibitory peptides, LanA and LanA', were detected. Both peptides were highly modified. Such modifications include dehydration of serine and threonine and the formation of a C-terminal aminovinyl-cysteine (AviCys) ring. While LanA peptide alone is absolutely required for antimicrobial activity, the presence of LanA' enhanced the activity of LanA, suggesting that B-Ny266 may function as a two-peptide lantibiotic. The activation of lanAA' expression is most likely controlled by the conserved two-component system NsrRS, which is activated by LanA peptide but not by LanA'. The chromosomal locus encoding mutacin B-Ny266 was not universally conserved in all sequenced S. mutans genomes. Intriguingly, the genes encoding LanAA' peptides were restricted to the most invasive serotypes of S. mutansIMPORTANCE Although dental caries is largely preventable, it remains the most common and costly infectious disease worldwide. Caries is initiated by the presence of dental plaque biofilm that contains Streptococcus mutans, a species extensively characterized by its role in caries development and formation. S. mutans deploys an arsenal of strategies to establish itself within the oral cavity. One of them is the production of bacteriocins that confer a competitive advantage by targeting and killing closely related competitors. In this work, we found that mutacin B-Ny266 is a potent lantibiotic that is effective at killing a wide array of oral streptococci, including nearly all S. mutans strains tested. Lantibiotics produced by oral bacteria could represent a promising strategy to target caries pathogens embedded in dental plaque biofilm.

Rapid Isolation and Purification of Secreted Bacteriocins from Streptococcus mutans and Other Lactic Acid Bacteria.

Bacteriocins are small ribosomally synthesized antimicrobial peptides produced by some microorganisms including lactic acid bacteria (LAB), a group of Gram-positive bacteria (cocci, rods) expressing high tolerance for low pH. Bacteriocins kill bacteria rapidly and are biologically active at very low concentrations. Bacteriocins produced by LAB are primarily active against closely related bacterial species. Many bacteriocins have been investigated with respect to their potential use in promoting human, plant, and animal health, and as food biopreservatives. Bacteriocins produced by LAB are particularly interesting since several LAB have been granted GRAS (Generally Recognized as Safe) status. Because it is not always possible to extract active bacteriocins secreted from cells grown in liquid medium, we developed a simple and inexpensive peptide extraction procedure using a semi-solid nutrient-rich agar medium. We hereby present a detailed procedure that leads to the rapid extraction of secreted bioactive bacteriocin peptides from the oral species Streptococcus mutans, a prolific bacteriocin-producing species, and its potential application for bacteriocin extraction from other LAB (e.g., Streptococcus, Lactococcus, Enterococcus). We also present a simple method for the detection of bacteriocin activity from the purified extracellular peptide extract.

Irrigation versus suction alone during laparoscopic appendectomy; A randomized controlled equivalence trial.

INTRODUCTION: The objective of this study was to compare operative peritoneal irrigation versus suction alone during laparoscopic appendectomy in adult patients; our hypothesis was that the two methods are equivalent in terms of rate of post-operative intra-abdominal abscess. There has been only one prospective, randomized, superiority trial in children, that showed non-significant difference in the rate of intra-abdominal abscess comparing irrigation to suction alone during laparoscopic appendectomy for perforated appendicitis. Non-significant difference in a superiority trial does not imply equivalence. METHODS: This was a single-institution, prospective, randomized controlled equivalence study based on a null-hypothesis of non-equivalence between irrigation and suction alone. Adult patients with intra-operative findings of an acutely inflamed appendix, with suppuration or perforation localized to the right iliac fossa, paracolic gutter or pelvis were randomized to irrigation or suction alone. The primary endpoint was the rate of intra-abdominal abscess. An unconditional exact test of equivalence was used to test the null-hypothesis. RESULTS: Eighty-one patients were included for analysis. Two (5%) of 40 patients in the irrigation group and two (4.9%) of 41 in the suction-only group developed postoperative intra-abdominal abscess. The 95% confidence interval for the difference between the two groups was -0.1200 to 0.1244, captured within the pre-defined δ limits (-0.15, 0.15). With reference to the rate of intra-abdominal abscess, equivalence was demonstrated between irrigation and suction-only techniques. CONCLUSIONS: In patients with suppurative or perforated appendicitis, the rate of intra-abdominal abscess is equivalent between groups treated with peritoneal irrigation and suction alone.