A rather apprehensive Christopher enters you consulting room, clinging tightly to his mother’s hand and staring at you with mistrustful eyes. It’s not really surprising, the last time he was here he had diarrhoea and vomiting and he clearly still blames you for it! You flash him a smile and get
straight down to business finding out what is wrong…

Christopher is 3 years old and for the last 2 days he has had a sore throat and a fever and has not been his normal boisterous self. His mum has brought him to see you because he has developed a fine rash on his chest and
abdomen which has made his skin feel very rough and dry, like sandpaper. You manage to get a quick look in Christopher’s throat and see enlarged, slightly purulent tonsils and a bright red “strawberry tongue”. You smile reassuringly at his mother and start to tap away on your computer… you know exactly what this is… you’ve seen the same problem 3 times already this week…

So what is the diagnosis?
Christopher has the classic signs of scarlet fever; a common childhood infection caused by the Group A Beta-haemolytic Streptococcus (Streptococcus pyogenes). Approximately 4,000 cases of scarlet fever are diagnosed each year in the
UK, with 80% occurring in children under 10 years old.

Bacteria like to colonise warm moist sites with poor blood supply and hence a poor immune response. They especially like broken areas of skin such as ulcers and lacerations.

Broken areas of skin are not sterile. Wounds should be colonised with relatively harmless bacteria like the Coagulase-negative Staphylococci, Coryneform bacteria (Diptheroids) and Propionibacterium spp. This normal process prevents more dangerous bacteria from getting in and causing infections such as Staphylococcus aureus and the Beta-haemolytic Streptococci. It is therefore really important that we only treat breaks in the skin when infections have occurred, rather than trying to prevent them occurring.

You are a BMS reading the results of the positive blood cultures from
yesterday when you notice that something doesn’t quite add up. The growth on the blood agar looks like an Alpha-haemolytic Streptococcus but the Gram film from yesterday looked like a Staphylococcus (Gram-positive coccus in clumps). To make matters more confusing the bacteria have not grown on the ISO sensitivity agar either.