Klebsiella

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The broad scope of Klebsiella

The genus, Klebsiella, has a broad scope and extensive list at the species and sub-species levels. To remain clear, we will limit our descriptions to the most clinically significant species and sub-species. Namely, K. pneumoniae and K. oxytoca. The justification for limiting to these two, specifically, is that 90% of the waterborne pathogen infections caused by Klebsiella are these two species.

While the microbiologists out there are going to express scorn for our unwillingness to spend the full article discussing the catalogue of attributes across the genus, we’re keeping to a 30,000-foot discussion when we speak about cellular level and notable characteristics.

Environments of Klebsiella

Klebsiella’s most immediate visual cue is its rod-shape and capsule. Its capsule is meant, in part, to protect it from hostile environments. Klebsiella thrives in the gastrointestinal tracts of a wide range of animals, including our own. And consequently, it’s also found in wastewater, soil, and then of course, fruits and vegetables as well. Since it predominates these areas, it easily integrates into the water cycle, particularly municipal water networks. The capsules promote biofilm development, which allows it to better protect itself and easily persist in water distribution systems despite heavy chlorination. Like the other pathogens we’ve discussed, this too is a gram-negative bacterium, and it’s non-motile tendency depends on the biofilm for protection and nutrients.

Patient risk associated with Klebsiella

Klebsiella is among the most resistant to antibacterial agents, and most recently to a class of antibiotics known as carbapenems. Therefore, we see so much healthcare associated infections (HAIs) resulting from this bug. Klebsiella does exist in the human GI tract, but this does not cause disease. Klebsiella only becomes problematic when it’s transmitted in the blood or inhaled. So, serious blood infections and acute pneumonia are the biggest concerns, particularly with patients in need of long-term, recurring infusions or patients on ventilators. Additionally, individuals hospitalized with liver disease are known to get liver abscess because of Klebsiella.

If you’re paying attention to the headlines, you’ve heard of Klebsiella outbreaks in the United States, but are these cases correlated in any way to our overuse of antibiotics in healthcare settings? Klebsiella is ubiquitous in the environment. It finds its way into many places where humans will run into it, and of course, one of those places is within hospitals and healthcare centers. One of the interesting features of gram-negative bacteria, like Klebsiella, is that they can share genes and plasmids. They can carry antibiotic resistance genes within these plasmids that can be shared with another bacterium and passed on from one group to another. Therefore, when they grow, the resistance to antibiotics can grow exponentially. Bacteria can carry, and “collect” multiple antibiotic resistance factors in their DNA, which makes them hugely dangerous, particularly in a healthcare setting housing immunosuppressed patient populations. The topic of antibiotic stewardship has reached a level of importance to warrant discussion and policy adoption at the World Health Organization (WHO). Even some at Center for Disease Control (CDC) and Health and Human Services consider this an issue that deserves a broader national discourse in the United States. We have a limited number of antibiotics with which to fight infections, and we are losing many of those options because of the way the bacteria are adapting. Consequently, it is harder for pharmaceutical companies to develop novel antibiotics.