Thermo Scientific™ Charcoal Agar Base (Dehydrated)

Description

• Cultivate and isolate Bordetella pertussis and Haemophilus influenzae with Thermo Scientific™ Oxoid™ Charcoal Agar Base (Dehydrated)
• The medium is designed to provide a non-blood containing medium for the cultivation of Bordetella pertussis and Haemophilus influenzae
• Nicotinic acid in the medium acts as essential growth factor for Bordetella 1
• Haemophilus and Bordetella are small, gram-negative rods that tend to assume a coccobacillary shape
• Members of both genera contain species exclusively found in humans and cause respiratory tract infections
• The major species are Haemophilus influenzae , the cause of acute purulent meningitis, and Bordetella pertussis , the cause of whooping cough
• Charcoal Agar was developed by Oxoid to provide a non-blood-containing medium for the cultivation of Bordetella pertussis and Haemophilus influenzae
• Proom 1 showed that nicotinic acid was an essential growth factor for the bordetellae
• Ensminger et al
• 2 used a charcoal medium for the growth of Bordetella pertussis in vaccine production and found that the medium could replace Bordet-Genou
• Mishulow et al
• 3 used charcoal agar for Bordetella pertussis cultivation
• Haemophilus influenzae is cultivated on the medium containing 10% chocolated blood but no antibiotics
• The inoculated plate is incubated for 2 to 3 days at 37°C
• The colonies are usually small, transparent, and droplet-like, but some transformation to the ‘rough’ type colony may occur
• Species differentiation is performed by examination of the need for X and V growth factors, on Blood Agar Base CM0055
• The greatest problem in the isolation of Bordetella species from naso-pharyngeal secretions is the suppression of unwanted flora during the long incubation period on very nutritious media
• Fleming’s first in vitro demonstration of penicillin was to show that it could help isolate Bordetella pertussis on media 4
• Lacey 5 confirmed this but found that the penicillin-resistant flora still caused problems
• He supplemented penicillin with 2μg/ml 4,4’ diamidino-diphenylamine dihydrochloride (M & B 938) thereby increasing the selectivity of this medium
• Broome et al
• 6 found methicillin to be superior to penicillin in suppressing unwanted naso-pharyngeal flora but the earlier publication of Sutcliffe and Abbott 7 where cephalexin (40μg/ml) was shown to be superior to penicillin, has proved to be the most significant advance
• The benefits of cephalexin as a selective agent for Bordetella pertussis have been confirmed 8,9,10,11
• The ability to recover stressed cells and the much longer shelf life (6-8 weeks) are added benefits to its superiority at suppressing unwanted naso- pharyngeal growth.