東京大学大学院農学生命科学研究科

Bacteriocins to Reduce Pathogens

講演内容の紹介

Campylobacter 感染症は世界的にみて最も患者数の多い食品媒介感染症である。日本においてもCampylobacter食中毒は事件数で最も多く、患者数も常にトップ５に入る重要な感染症である。Campylobacterは鶏肉を介しての食中毒が多いが、鳥類、牛、豚など自然界に広く分布しており、”From farm to table”の農場での汚染の抑制が感染予防の面で極めて重要な意味を持つ。しかし、動物の腸内では常在菌化しており、その抑制はSalmonella以上に困難と考えられている。今回講演をお願いするStern博士は、長年この分野での研究をされてきた第一人者で、特に最近はBacteriocinを用いたCampylobacterの汚染抑制で大きな成果を上げてこられた。単にBacteriocinを飼料中に混入させるのではなく、カプセルに封じ込めて飼料に添加することでその効果を発揮させている。

今回新潟で開催されますCHRO2009（15th International Workshop on Campylobacter, Helocobacter, and Related Organisms）での御講演のために来日するのを機会に東京大学で御講演をお願いしたものです。奮ってご参加ください。

Abstract

Bacteriocins to Reduce Pathogens-Edward Svetoch1 and Norman Stern2

1. State Research Center for Applied and Environmental Microbiology and Biotechnology-Obolensk, Russian Federation
2. Presentation by-Dr. Norman Stern, Poultry Microbiological Safety Research Unit, USDA-Agricultural Research Service, Athens, Georgia, USA

The paper will review studies which have used a variety of bacteriocins (BCN) to treat Campylobacter jejuni and Salmonella enteritidis colonized broiler chickens. Antagonistic bacteria were chosen by selecting those isolates which produced zones of inhibition among confluent C. jejuni growth. From these antagonists, BCN activities were demonstrated by overlaying C. jejuni inoculated agar onto SDS-PAGE and IEF gel preparations containing the crude antimicrobial preparations; BCN were characterized by Edman degradation and MALDI-TOF analyses and; quantities of the proteins were produced by fermentations which were then extracted by chromatographic procedures. A number of broiler chicken colonization studies were conducted, comparing levels of C. jejuni and Sal. enteritidis among both (therapeutically) treated and positive control groups. Results indicated that our BCN were characterized as polypeptides with 37 to 62 amino acid residues having molecular weights of 3,340 Da to 5,362 Da. The isoelectric points varied from 7.2 to 9.5. Paenibacillus polymyxa NRRL B-30509 BCN reduced C. jejuni colonization from 107.2 cfu g-1 to non-detectable levels in the cecae; Lactobacillus salivarius NRRL B-30514 BCN consistently reduced C. jejuni by at least one-million fold in the broiler cecae; Enterococcus faecium NRRL B-30745 BCN reduced C. jejuni in market age broilers from 106.2 cfu g-1 to non-detectable levels in the cecae; Ent. faecium NRRL B-30746 BCN reduced both C. jejuni in market age broilers from 108.0 cfu g-1 to 102.9 cfu g-1 cecae and Sal. enteritidis from 107.5 cfu g-1 to non-detectable levels in the cecae and, from 108.8 cfu g-1 to 104.6 cfu g-1 in the livers. A variety of BCN have been discovered which have been used to significantly reduce C. jejuni and Sal. enteritidis in both the intestinal tract and liver of infected broiler chickens. BCN MICs for E50-52 and B602 against clinical isolates Acinetobacter spp. (n=11), Citrobacter freundii (n=8), Escherichia coli (n=9), Klebsiella pneumoniae (n=10), Proteus spp. (n=6), Pseudomonasa aeruginosa (n=10), and Staphylococcus aureus (n=10) ranged from < 0.025 to 1.56 g/ml for bacteriocin B602 and 0.05 to 6.25 g/ml for bacteriocin E50-52. Limited studies have been conducted on Campylobacter resistance to BCN. Inactivation of efflux pumps suggests that only the CmeABC efflux pump contributed Campylobacter resistance to the BCNs. These novel therapeutic treatments with BCN may assist in the control of infections by pathogens.