Charcoal Agar Base with Niacin, 5 kg

The genus Bordetella contains four species : Bordetella pertussis, Bordetella parapertussis, Bordetella bronchiseptica and Bordetella avium (1). Genetic studies have shown that these organisms are very closely related to each other. Humans are the only host of B.pertussis and B.parapertussis , while B.bronchoseptica is found in a wide variety of animals and occasionally found in humans (2). B. avium is found in birds. Bordetella species are obligately aerobic and metabolically not very active. They are non-motile except B.bronchoseptica . B.pertussis is the major cause of whooping cough or pertussis. B.parapertussis is associated with a milder form of the disease (3). Primary isolation of B.pertussis in particular, requires the addition of charcoal, 15-20% blood to neutralize the growth-inhibiting effects. Isolation of this organism requires enrichment medium. Charcoal Agar is prepared according to the method of Mishulow, Sharpe and Cohen (2). This medium can be used as a replacement for Bordet-Gengou Agar for isolation of B.pertussis and for the production of B.pertussis vaccines. Charcoal Agar supplemented with horse blood can also be used for the cultivation and isolation of Haemophilus influenzae (4). Medium ingredients like pancreatic digest of gelatin and beef extract provide essential nutrients to the organisms. Sodium chloride maintains osmotic balance. Starch soluble and charcoal neutralizes substances toxic to Bordetella species such as fatty acids. Charcoal has the tendency to settle at the bottom of the flask. Therefore, before dispensing, swirl the flasks gently to obtain a uniform charcoal suspension (7). The difficulty in the isolation of Bordetella pertussis from nasopharyngeal secretions is the repression of unwanted flora during the long incubation period on nutritious media. Penicillin can be added to the medium as an antimicrobial agent for restricting the other contaminants. However Penicillin resistant flora still causes the contamination that was observed by Lacey (4). Necessity of the Nicotinic acid as a growth factor was showed by Proom (8). Methicillin was found to be superior to Penicillin in suppressing unwanted nasopharyngeal flora as observed by Broome et al (5). Sutcliffe and Abbott found that Cephalexin was still better than Methicillin (6). Storage and Shelf-life: Store below 30°C in tightly closed container and the prepared medium at 2-8°C.Use before expiry date on the label. References: 1. Murray P. R., Baron J. H., Pfaller M. A., Jorgensen J. H. and YolkenR. H., (Ed.), 2003, Manual of Clinical Microbiology, 8th Ed., American Society for Microbiology, Washington, D.C. 2. Mishulow, Sharpe and Cohen, 1953, Am. J. Public Health, 43:1466 3. Linneman and Pery, 1977, Am. J. Dis. Child., 131:560. 4. Lacey B. W., 1954, J. Hyg., 59:273. 5. Broome C. V., Fraser D. W. and English J. W., 1979, Internat. Symp. on Pertussis DHEW J., Washington D.C., pp 19-29. 6. Sutcliffe E. M. and Abbott J. D., 1979, B.M.J. II: 732-733. 7. MacFaddin J. F., 1985, Media for Isolation-Cultivation-Identification -Maintenance of Medical Bacteria, Vol. I, Williams and Wilkins, Baltimore. 8. Proom H., 1955, J. Gen. Microbiol., 12 (1): 63-75.