Monday, January 22, 2018

Propionibacterium - the most common bacteria on healthy skin and in infected shoulder joint replacements

In 1886 Robert Louis Stevenson wrote the gothic novel


about a character who could be either really good or really bad. We suggest you read it if you haven't recently.

In a real sense Propionibacterium is this character.

A recent article, The human skin microbiome, provides some excellent insight into this organism, the importance of which in orthopaedics has only recently been recognized. 

On one hand it is an essential ingredient of healthy skin, keeping it lubricated and resisting major pathogens, such as Staph Aurus. On the other hand, it is the most commonly recovered bacterium from failed shoulder joint replacements; it can be recovered as well from failed hip and knee arthroplasties, ruptured disc fragments, failed rotator cuff repairs, failed fracture fixation and failed spine surgeries. But, it can only be reliably recovered if special culture methods are used - if you don't look for it, you will not find it.

While it is recovered from the surface of normal skin, it lives in the dermal glands within the skin. 




It is able to thrive in the anoxic sebaceous gland by using proteases to liberate the amino acid arginine from skin proteins and lipases to degrade triglyceride lipids in sebum; this releases free fatty acids, which promote bacterial adherence. Sebum levels positively correlate with Propionibacterium abundance.

The relative abundance of skin microbial species, including Propionibacterium, is restructured during puberty, a time when increased levels of hormones stimulate the sebaceous glands to produce additional sebum. Thus, the skin of postpubescent individuals favors the expansion of lipophilic microorganisms, such as bacterial Propionibacterium and Corynebacterium. By contrast, pre-pubescent children have greater abundances of Firmicutes (Streptococcaceae spp.), Bacteroidetes and Proteobacteria (betaproteobacteria and gammaproteobacteria) .

Gene expression profiles of P. acnes are different for individuals with Propionibacterium associated diseases, for example between individuals with acne and individuals without acne. The observation that almost all adults are colonized with P. acnes but only a minority have acne highlights the importance of studying diseases in the broader context of host genetics, immune or barrier defects, the microbiome and the environment. For example, increased sebum secretion is associated with the pathophysiology of acne, as secretion rates correlate with the severity of clinical symptoms. In a study using fluorescent microscopy to visualize P. acnes in follicles of skin biopsy samples, acne development was substantially associated with the presence of P. acnes in follicles and its formation of biofilms. At the clade level, P. acnes belonging to the type 1A1 phylogroup have been consistently associated with acne across studies utilizing distinct sampling and analysis methods. Strains within the type 1A1 phylogroup have increased inflammatory potential based on the presence of putative virulence factors that affect bacterial adhesion and host immune responses. The propensity of certain strains of Propionibacterium to form biofilms is thought to be an important factor in Propionibacterium-associated total joint arthroplasty failure.

Protected inside the skin, Propionibacterium can not be eliminated by soap or surgical skin preparation or systemic antibiotics. Lying within the dermis, these organisms are released into the wound when surgical skin incisions are made. Propionibacterium seem more likely to create a problem if a large number are introduced into the wound and if a metal device (such as a joint replacement) is implanted. The importance of factors such as bacterial virulence, biofilm propensity, hemolysis, host resistance, and antimicrobial prophylaxis are still being investigated. 

We need to learn much more and we're working on it!


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