Blood Free Campylobacter Selectivity Agar Base w/ Yeast Extract

Principle And Interpretation

Campylobacters are microaerophilic, very small, curved, thin, Gram-negative rods (1.5-5 µm), with corkscrew motility. It is considered to be one of the leading causes of enteric illness in the United States and other developed countries (1). The organism is reported to cause mild to severe diarrhea, with loose, watery stools often followed by bloody diarrhea. The infection together is called as campylobacteriosis. Campylobacters are carried in the intestinal tract of a wide variety of wild and domestic animals, especially birds and are frequent contaminants foods of animal origin (2).

Blood Free Campylobacter Selectivity Agar Base, w/ yeast extract is used for selective isolation and differentiation of Campylobacter species in accordance with FDA BAM, 1998(3). Initially blood was used in the isolation of Campylobacter . But, later it was reported by Bolton et al (4) that charcoal can be effectively used in place of blood. Campylobacter species are highly resistant to cefoperazone, an antibiotic which effectively suppresses growth of Pseudomonas and Enterobacteriaceae (5-7). Addition of cefoperazone increases the selectivity of the medium. Due to this addition, the medium is also known as Campylobacter Charcoal Differential Agar (CCDA). Charcoal, sodium pyruvate and ferrous sulphate reduces the aero tolerance of medium by quenching photochemically generated toxic oxygen derivatives (7). Peptone, casein hydrolysate and meat extract B serve as sources of essential nutrients and amino acids. Casein is added to help grow certain strains of nalidixic acid resistant thermophilic Campylobacter that are environmental organisms. Additional Amphotericin B in Blood Free Campylobacter Broth Base suppresses the growth of yeast and mold contaminants. Colonies tend to swarm when initially isolated from clinical specimens.

According to the BAM protocol, samples are pre enriched if required with suitable media under micro aerobic conditions for appropriate time at 37°C. These enriched cultures are further proceeded for isolation, identification and confirmation. For isolation, appropriately diluted samples are inoculated into either Heart Infusion Yeast Extract Agar Base (M169F + FD 294 and/ or FD009) or Bloodfree Campylobacter Selectivity Agar Base, w/ yeast extract (M 887F + FD135F). Plates are incubated at 37-42°C under anaerobic conditions away from light. Campylobacter colonies on agar appear as round to irregular with smooth edges. They can show thick translucent white growth to spreading, film-like transparent growth. These are further confirmed using microscopy and biochemical tests.