Bile Salt Irgasan Brilliant Green Agar (BSIBG)

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INTRODUCTION

Bile Salt Irgasan Brilliant Green Agar (BSIBG) is a highly selective agar medium that uses bile salts, brilliant green, and Irgasan for the isolation of Aeromonas spp. from a variety of environmental, clinical, and food samples. Aeromonas spp. has been regarded as controversial pathogen and a possible source of food-borne infection with some strains noted as being enteropathogenic. This species of bacteria has also been found to grow and produce virulence factors not only at optimal growth temperature, but at refrigeration temperatures as well. 

SELECTIVITY

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This medium was originally designed for isolation of Aeromonas spp. from fecal samples. Absense of an antibiotic in the medium allows for the isolation of ampicillin-sensitive strains to grow and has been found more successful in isolation than formulations containing ampicillin. (1)

The addition of bile salts and brilliant green dye inhibit the growth of a majority of gram-negative and gram positive species, while Irgasan, also known as Triclosan (5-chloro-2-(2,4-dichlorophenoxy)phenol, C12H7Cl3O2) is a broad spectrum antimicrobial agent and an inhibitor of the enoyl-ACP (acrylic carrier protein) reductive component of type II fatty acid synthase in bacteria. When introduced into media, this chemical inhibits gram-negative organisms that posses type-A nitrate. Triclosan acts predominately against gram-positive bacteria but has the ability to affect gram-negative bacteria, fungi, and viruses. 

Microorganisms that survive the selective process of the agents added to the medium can be later be differentiated on their ability to attack the sugar xylose. Aeromonas spp. does not ferment xylose, so oxidase tests should be performed on the colonies that do not produce acid in order to differentiate between species. 

Reconstitution

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PREPARATION OF Bile salt irgasan brilliant green AGAR

  1. Add both dry and wet components to distilled water and boil to dissolve completely.

  2. Sterilize media by autoclaving at 121ºC for 15 minutes.

  3. Cool sterilized media to 45-50ºC.

  4. Aseptically dispense into sterile petri dishes and/or other appropriate containers.

Final pH: 7.0 ± 0.2 at 25°C

STORAGE AND SHELF LIFE 

Media is both light and temperature sensitive. Store plates away from direct light at 2-8ºC, or if properly sealed and stored upright, 15-25ºC. Plates may be used for one week when stored in a clean sterile area. Media should not be used if any signs of deterioration, color change, contamination, and/or expiration date has passed.

STERILIZE ALL BIOHAZARD WASTE BEFORE DISPOSAL.  

Quality Control

Samples requiring enrichment should first be inoculated with alkaline peptone water and incubated for 18-24 hours at 37°C and subcultured via surface spreading for individual colonies identification.

Plates not needed enrichment should be incubated for 18-27 hours at 37°C or depending the specific strain and optimal growth factors. 

Suitable microorganisms for Quality Control:

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References:

  1. “Aeromonas Agar -Bile Salt Irgasan Brilliant Green Agar.” http://www.labm.com/data/Product_Downloads/LAB167%20Aeromonas%20Agar%20specification_02.pdf

  2. “Bile Salts Irgasan Brilliant Green (BSIBG Agar).” September 2 2007. Handbook of Culture Media for Food Microbiology, J.E.L. Corry Et. Al. 2003. Elsevier Science B.V. https://doi.org/10.1016/S0079-6352(03)80033-4

  3. “Irgasan .” H2NC6H4CO2C2H5, Drugs, www.sigmaaldrich.com/catalog/product/sigma/72779?lang=en%C2%AEion.

  4. Yazdankhah, Siamak & Scheie, Anne & Arne Høiby, E & Lunestad, Bjørn & Heir, Even & Øystein Fotland, Tor & Naterstad, Kristine & Kruse, Hilde. (2006). Triclosan and Antimicrobial Resistance in Bacteria: An Overview. Microbial drug resistance (Larchmont, N.Y.). 12. 83-90. https://doi.org/10.1089/mdr.2006.12.83