Burkholderia cepacia Agar Plate

Principle And Interpretation

Burkholderia cepacia is an important opportunistic pathogen and causes pulmonary infection among individuals with cystic fibrosis (CF). The organism may lead to Burkholderia cepacia syndrome, a neutralizing pneumonia associated with fever that culminates in to a rapid and fatal clinical deterioration (1). B cepacia is difficult to isolate on routinely used laboratory media like MacConkey Agar, since B.cepacia is a slow grower and therefore it is usually outgrown by the faster growing Escherichia coli, Staphylococcus aureus and Pseudomonas aeruginosa. Burkholderia Cepacia Agar is based on PC medium, which was originally devised by Gilligan (2). This medium was found to be superior to MacConkey Agar for growth of B.cepacia. The medium is made selective for B.cepacia by the incorporation of bile salts, crystal violet and antibiotics. The antibiotics included are Polymyxin B, Gentamicin, Ticarcillin in the form of freeze dried supplement (FD). Peptone and yeast extract in the medium provides the nitrogenous, vitamin B source and other essential nutrients. Crystal violet, bile salts and antimicrobial agents are used as selective agents. Crystal violet and bile salts inhibits gram-positive cocci including Enterococci and Staphylococci. The antibiotics (FD) namely ticarcillin, polymyxin B and gentamicin inhibit gram-negative bacteria. B. cepacia metabolizes pyruvate forming alkaline end products. These end products elevate the pH of the medium. The phenol red indicator changes colour from pink orange to pink red in alkaline pH. Inoculate the plate with the specimen so as to obtain isolated colonies. The plates should be incubated for a period of 4 days to allow B. cepacia to grow and form colonies and subsequent colour change (2,3). The medium is not selective only for B. cepacia. Other organisms forming similar colonies may also grow on this medium. Therefore results obtained on this media should not be the sole criteria for identification of B. cepacia (4).