Strains of bacillus for inhibiting foodborne pathogens

Abstract

A process for inhibiting foodborne pathogens and reducing foodborne disease involves contacting a living animal, a dressed carcass, or a cut of meat with an effective amount of a bacillus strain exhibiting antibacterial activity. Strains of antibacterial bacillus that are particularly effective for inhibiting Vibrio were discovered. These include Bacillus licheniformis OBT 712 and Bacillus amyloliquefaciens OBT 618.

Claims

1. A process for inhibiting foodborne pathogenic bacteria, comprising contacting a living animal, dressed carcass, or cut of meat with an effective amount of Bacillus licheniformis strain OBT 618 as deposited with the American Type Culture Collection under accession number PTA-122188 that exhibits antibacterial activity.

2. The process of claim 1, in which a foodborne pathogenic bacteria is known to be present in or on the living animal, dressed carcass, or cut of meat.

3. The process of claim 2, in which the foodborne pathogenic bacteria is Vibrio.

4. The process of claim 1, in which contacting the living animal, dressed carcass, or cut of meat with the Bacillus strain is done by applying an aqueous based composition containing the Bacillus strain to the live animal, dressed carcass, or cut of meat.

5. The process of claim 4, in which the applying is done by spraying, brushing or dipping.

6. The process of claim 1, in which the process is performed on a living animal, and the contacting is done by feeding the antibacterial Bacillus to the living animal.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) FIG. 1 (SEQ ID NO: 1) is the relevant sequence for Bacillus licheniformis OBT 618.

(2) FIG. 2 (SEQ ID NO: 2) is the relevant sequence listing for Bacillus amyloliquefaciens OBT 712.

(3) FIG. 3 is a schematic illustration of the preparation of an antibacterial bacillus strain isolate.

(4) FIG. 4 is a schematic illustration of a process for screening isolates that are antagonistic toward an isolate of Vibrio sp. selected from a marine environment using an agar overlay method.

(5) FIG. 5 is a photograph showing a comparison of a positive (+) result for Bacillus amyloliquefaciens OBT 712 to a negative () control.

DESCRIPTION OF THE DISCLOSED EMBODIMENTS

(6) It has been discovered that foodborne pathogens can be inhibited when contacted with an effective amount of a bacillus strain exhibiting antibacterial activity.

(7) The term inhibit means to reduce or arrest growth and/or reproduction of bacterial pathogens that can cause foodborne diseases, and encompasses killing such bacterial pathogens.

(8) The term effective amount means an amount that will achieve a desired level of foodborne pathogen inhibition to effect a beneficial result such as reducing bacterial pathogen populations in or on food, or in or on animals that are processed into foods.

(9) Foodborne pathogens that can be inhibited include Salmonella enteric, Escherichia coli, Clostridium difficile and Vibrio.

(10) Bacillus strains exhibiting antibacterial activity include Bacillus licheniformis strains (e.g., OBT 618), and Bacillus amyloliquefaciens strains (e.g., OBT 712). The relevant sequence listings for Bacillus licheniformis OBT 618 and Bacillus amyloliquefaciens OBT 712 are shown in FIGS. 1 and 2, respectively.

(11) The step of contacting the foodborne pathogens with a bacillus strain exhibiting antibacterial activity can involve application of an aqueous based composition containing the antibacterial bacillus strain to a live animal, a dressed carcass or cuts of meat, such as by spraying, brushing or dipping. In the case of aquatic animals, the antibacterial bacillus strain can be added to a container, tank or enclosure (e.g., a fish hatchery) in which the aquatic animals are raised and/or from which they are harvested. As another alternative, contact between the bacterial pathogens and the antibacterial bacillus can be achieved by feeding the antibacterial bacillus to the animal, either directly or to animals that serve as the food source for the animal that is ultimately processed for consumption such as by a human or companion animal.

(12) FIG. 3 shows a method of preparing an antibacterial bacillus strain isolate. Samples from marine environments were selected for spore-forming bacillus and Vibrio species. The bacillus samples were enriched, and subsequently pasteurized at about 70 C. Bacillus isolates were then placed on sporulation agar. The Vibrio was placed on thiosulfate-citrate-bile salts-sucrose (TCBS) agar.

(13) FIG. 4 shows an assay to determine growth inhibition for the bacillus strains. A candidate bacillus spore-former is placed on a trypticase soy agar (TSA) plate, and thereafter, Vibrio isolate embedded in top agar is disposed over the TSA plate. After a sufficient period (e.g., two days), the zones in which the candidate bacillus strains are overlaid with the Vibrio isolates are inspected for clearance of the Vibrio. Positive results are illustrated on the right side of the agar dish at Step 3 of FIG. 4.

(14) FIG. 5 is a photograph showing an actual positive result labeled HB8(+) and a negative result labeled Control().

(15) Isolates were screened for antagonism toward an isolate of Vibrio sp. selected from a marine environment using an agar overlay method. This method consisted of covering one day old bacillus cultures with the Vibrio isolate embedded in agar. Zones of clearance were evaluated at 2 days. Thirty-six isolates from various environments were screened. Of the thirty-six isolates tested, two isolates, a B. licheniformis (OBT 618) and a B. amyloliquefaciens (OBT 712), had particularly high levels of antagonism toward Vibrio. All strains are easily propagated on trypticase soy agar (TSA) and sporulate in liquid media.

(16) These strains are antagonistic to Vibrio. They produce a clearance zone on agar plates when the Bacillus colonies are covered with a thin agar layer that includes Vibrio sp. One isolate has a delayed response killing the Vibrio after it has grown. The other inhibits Vibrio growth.

(17) In a preliminary trial, feeding rotifers the Bacillus strains increased survivability of larval snook fed the rotifers. The mechanism by which the Bacillus isolates fed to rotifers increases survivability of larval snook fed the rotifers has not been determined. It is conceivable that they are inhibiting growth of Vibrio within the digestive tract of rotifers or snook. It is also possible that they inhibit growth of Vibrio within larval brooding tanks overall.

(18) Anticipated use is at a concentration of 10.sup.5-10.sup.7 spores/ml in live food tanks or in a larval rearing tank. They are stored as freeze dried spores. Spores can be supplied on a nutritive carrier.

(19) The invention could possibly be used to suppress Vibrio sp. on multiple fish species as well as shell fish that are grown in culture. Vibrio is a gammaproteobacteria, a class of bacteria that includes Pseudomonas and Enterobacter such as E. coli and Salmonella sp. It could potentially be antagonistic to these other species.

(20) Possible ancillary benefits of Bacillus addition in aquaculture include improved nutrient availability and waste reduction.

(21) The Bacillus licheniformis strain OBT 618 was deposited under the Budapest Treaty and will be irrevocably and without restriction or condition released to the public upon issuance of a patent. The Bacillus licheniformis strain OBT 618 was deposited May 29, 2015 at the American Type Culture Collection (ATCC), P.O. Box 1549, Manassas, VA 20108 and given accession number PTA-122188.

(22) The described embodiments are preferred and/or illustrated, but are not limiting. Various modifications are considered within the purview and scope of the appended claims.