Saturday, November 5, 2016

Propionibacterium antibiotic resistance - more bad news

Propionibacterium acnes and bacterial resistance

In this review article, the authors point out that Propionibacterium acnes is one of the main microorganisms found on the skin. It is predominantly found in hair follicles, prefers anaerobic conditions, preferably colonizes the areas with high sebum production, and is the main bacterium involved in the pathogenesis of acne. They suggest that the indiscriminate use of antibiotics for the treatment of acne vulgaris can result in the development of bacterial resistance.

Several observations in this article are of interest to us shoulder surgeons:

There are over one million Propionibacterium per square centimeter of skin.

Propionibacterium inhibits the invasion of the skin by common pathogens such as Staphylococcus aureus and Streptococcus pyogenes.  Its hydrolyzation of triglycerides with the release of free fatty acids (including propionic acid) contributes to the acid pH of the skin’s surface, which is another factor for skin protection. Note: this suggests that elimination of Propionibacterium from the skin of the surgical site may open the door for worse bugs.

There are many different types of Propionibacterium; on average, each individual has 3 different Propi ribotypes on the skin each with different pathogen potential and different resistance patterns. 

Persons can transmit the different clones to other individuals, and thus resistant bacteria can be spread throughout the population by 'rubbing elbows'.

There has been an increasing number of cases of antibiotic- resistance by P. acnes over the years: in the UK, the resistance rate increased from 34.5% in 1991 to 55.5% in 2000;156 94% of  the isolates in Spain and 51% from the isolates in Hungary were  resistant to at least one antibiotic. The highest resistance rates are related to erythromycin, with cross-resistance to clindamycin. The lowest resistance rates are to tetracyclines.

Resistance comes from gene mutation:

In cases of severe infections caused by P. acnes, surgical procedures should be combined with crystalline penicillin, vancomycin, daptomycin, and rifampicin due to their effect on the biofilm.

Comment: The reasons for the emergence of Propionibacterium as a problem in shoulder surgery is becoming clearer - the use of antibiotics for acne and for other reasons is changing the genetics of the bacterium to favor antibiotic resistance and the resistant strains are being exchanged within the human population.