Have you ever played draughts? I think it’s called checkers in America. It’s a board game that requires you to move pieces known as men and kings to take an opponent’s pieces. The pieces are often made of wood or plastic and have indentations to make stacking easier.
It’s these indentations that link the game of draughts to bacteriology.
Let me introduce the pneumococcus. Formally known as Streptococcus pneumoniæ. This is a Gram-positive diplococcus that forms α-hæmolysis on blood agar. This means the colonies look green when you hold the plate up to the light.
As the bacterial cells divide and the colony grows in size, autolysis occurs in the centre of the colony forming a dimple or umbilication. Some clever bacteriologist a long time ago thought the colonies looked like draughts pieces and so in many bacteriology textbooks, you’ll read about how the colonies look like draughts (or checkers) pieces.
The pneumococcus can cause many infections including pneumonia, meningitis, bacteræmia, and septicæmia. It can also be involved in appendicitis and vulvitis in children.
One of my fondest memories from medical school is studying pathology in the third and fourth year. The School of Medicine at the University of Queensland had one of the best-curated pathology museums. I loved handling the pots as they were known which contained various organs in various states of disease. Coupled with the pots we would sit down and learn the histopathological features of each pathological state under a microscope. A good going pneumococcal pneumonia goes through phases of consolidation known as hepatisation. In lobar pneumonia, as the pneumococcus creates more and more pus, the lung goes through red hepatisation when erythrocytes, neutrophils and fibrin occupy the alveoli. This proceeds to grey hepatisation when the erythrocytes breakdown leaving a lovely fibrinosuppurative exudate. If you’re not familiar with the term hepatisation, it means it looks like liver. It always made me feel hungry. I love eating lambs fry or lamb liver that has been marinated in a little whisky with Worcestershire sauce and served with fried bacon, calf testes, a lamb cutlet and a few fried eggs.
Anyway, I’m pretty fond of the pneumococcus. One of the joys of clinical bacteriology is being able to look at a Gram’s stain from a clinical specimen and along with the relevant clinical information being able to provide advice to the referring medical practitioner about the likelihood of the cause of the illness and the best approach to treatment. Sadly, antimicrobial resistance is becoming more and more of a problem with pneumococcal infections.
If you disagree with anything in these podcasts or if you would like to voice a different view, please feel free to write a comment. If I have said something incorrect I welcome correction. Please also feel free to share your comments on social media.