Reporting of the throat swab cultures:
If a B-haemolytic streptococcus sensitive to bacitracin is isolated, report the culture as “S. pyogenes presumptive group A isolated, Lancefield group to be confirmed. If a B-haemolytic streptococcus that is not sensitive to bacitracin is isolated (confirm that the colonies are
”Beta-haemolytic to follow”.
Modified Tinsdale medium (MTM) and tellurite blood agar (TBA) Cultures.
On MTM, c. diphtheriae produces grey-black raised colonies surrounded by a dark brown area.
If there is no growth, reincubate to the plate for further 24 hours.
Examine the TBA plate for grey or grey-black colonies measuring 0.5-2 mm in diameter.
Sabouraud agar culture Look for candid albicans