Wednesday, November 2, 2016

Propionibacterium - look out!: they are becoming resistant to antibiotics

Propionibacterium acnes and antimicrobial resistance in acne

These authors provide insight into the antibiotic resistance of Propionibacterium, a bacterium that resides in the pilosebaceous duct of the skin. "The prevalence of antibiotic-resistant Propionibacterium is worldwide and increasing, with rates varying in different parts of the world. The reason for the difference in the antibiotic resistance patterns of P. acnes among different countries is not clear, although it may be attributed to different antibiotic prescribing habits, concomitant topical agents (retinoids, benzoyl peroxide, or other antibiotics), varying methods of bacterial sampling, or even different Propionibacterium populations. While the relative abundances of Propionibacterium may be similar among acne patients and individuals without acne, the Propionibacterium populations and the presence of Propionibacterium biofilms differ with different potential virulence properties and antimicrobial resistance patterns. Concern is expressed regarding the decreased efficacy of antibiotics  and the possible emergence of other resistant bacterial species via selective pressure by antibiotic use."

Here are their data on antibiotic resistance:

Comment: While this is an article about acne, these authors point out information relevant to orthopaedic surgeons "the presence of a bacterial biofilm may play a key role in antimicrobial resistance. A biofilm is defined by three essential components: the microbial cells, a surface where these cells adhere, and an extracellular polymeric matrix in which cells are embedded and form larger communities.This complex protective glycocalyx is produced by bacteria and protects them from host defences and topical or systemic antimicrobial therapy by limiting the effective antimicrobial concentrations within the biofilm microenvironment. Propionibacterium in biofilms may exist in a sessile state (called persister cells). They are able to communicate through ‘quorum sensing,’ and they are relatively metabolically inert and protected. Factors implicated in increased resistance in biofilms include restricted penetration of antimicrobials, decreased growth rate, expression of resistance genes, and the presence of resistant ‘persister’ cells. When conditions permit, they undergo a phenotypic change. They become planktonic and free of the biofilm, inducing the expression of new proteins. Bacteria in planktonic state may lead to infection, and only in this state may they be recognized through culture."

These observations help understand the delayed manifestations of Propionibacterium in failed shoulder arthroplasty.