Back story or back to basics?
Our tale of a bad back, recently posted online by no less than the New England Journal, has a bit of background for students of microbial trivia. The Klebsiella that caused that specific infection had a collection of nasty attributes. This is the back story.
For some years now we have recognised a particular collection of destructive outcomes from Klebsiella pneumonia infection. These include liver abscess, meningitis, pleural empyaema or endophthalmitis, all of which are more common when the Klebsiella strain makes a sticky mess on the agar plate. Hence the name for the condition: hypermucoviscous (HV) Klebsiella syndrome. These strains can be detected in the clinical laboratory using the string test, which uses a bacteriological loop to tease out a long string of mucoid Klebsiella capsule material.
That’s all very well, but doesn’t completely explain why gas forms in tissues or in the case we reported, a vertebral body. And here’s where a knowledge of bacteriology comes in handy. Klebsiellas produce a compound called acetoin during fermentation reactions (demonstrated by a positive Vosges-Prokauer reaction). And the acetoin pathway produces twice as much CO2 during glucose fermentation than the alternative pathway used by E.coli and many other enteric bacteria. From there on it is easy to put the story together. Klebsiella will use glucose in anaerobic conditions to form acetone and gas.
Now, some people suggest that the hypermucoviscous Klebsiellas are very different from the strains with multiple antibiotic resistance. But recent data from the Indian subcontinent tells a different story. There, highly virulent Klebsiellas can also be very antibiotic resistant. Though we have yet to see a convergence of these on a large scale closer to home, it is clear that HV Klebsiella is gaining prominence on a global scale.