grows well and generally exhibits typical morphology on Columbia blood agar, whereas requires a more complex medium to meet its growth requirements - usually chocolated blood agar – on which is less easily recognisable. Therefore, a single medium that produces typical morphology of and facilitates the growth of would have considerable potential advantages. It has been claimed that blood agar supplemented with nicotinamide adenine dinucleotide (NAD) is such a medium. However, despite its routine use in several large diagnostic laboratories its performance has never been properly evaluated. In the present study, 1724 sputum samples were examined in four laboratories. The isolation rates of and on NAD-supplemented blood agar (SBA) were compared with those on a two-plate combination of plain blood (BA) and chocolated blood agar (CBA). The two-plate combination performed significantly better for both organisms; isolation rates for were increased from 8.16% on SBA to 11.07% on BA plus CBA and for from 4.18% to 4.68%. Isolation rates were also compared after incubation for 24 and 48 h. With the two-plate combination, isolation rates for and were increased by 0.98% and 0.16%, respectively, and for SBA by 0.57% and 0.32% after 48 h. However, despite this increase, SBA still performed less well than the two-plate combination.


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