Cutibacterium - why is it so difficult to get them out of bones and joints?

Cutibacterium (propionibacterium) was long dismissed as just a normal inhabitant of the skin, a cause of acne, a slow‐growing facultative anaerobe, a non-virulent organism, and a contaminant when found in intraoperative cultures.

Now, however, clinical scientists point out that Cutibacterium is the organism most commonly associated with periprosthetic infections of the shoulder. And, furthermore, Cutibacterium has the ability to persist in prosthetic wounds, in spite of prophylaxis, surgical treatment and antibiotic management.

This persistence is likely to multifactorial, related in part to the large amounts of this organism on the skin, the host's inability to recognize Cutibacterium as "a foreign invader", and the ability of this organism to form biofilms that protect it from antibiotics and immune response.

Recently, the authors of Cutibacterium acnes invades submicron osteocyte lacuno‐canalicular networks following implant‐associated osteomyelitis uncovered more information bearing on the challenge of eliminating this organism from arthroplasty wounds. They developed an implant-associated osteomyelitis model in which mice were subjected to transtibial implantation of titanium or stainless-steel pins contaminated with Cutibacterium. Using in vitro scanning electron microscopy (EM) they confirmed that Cutibacterium can form biofilms on stainless-steel and titanium implants - two of the common metals used in prosthetic implants. In their model, Cutibacterium persisted for 28 days not only in the tibia but that it also disseminated to internal organs. 

Transmission EM revealed the presence of Cutibacterium within bone canaliculi. These data revealed that the osteocyte lacuno-canalicular networks can serve as a sheltered reservoir in which Cutibacterium can persist long after inoculation. 

This adds yet another possible mechanism explaining why Cutibacterium chronic implant-associated bone infections can be delayed in their presentation and difficult to treat.

One of the striking features of this work is that it demonstrates biofilm formation with bacterial adherence to the pin surface as early as 3 hours after implantation. Progressive biofilm formation was seen with increasing pin incubation time as shown below

The recovery of Cutibacterium from bone, soft tissue, liver, kidneys, heart and spleen at 28 days after implantation demonstrates the systemic spread of the organism and inability of the host to resolve the infection. 

Comment: Cutibacterium can now be recognized as a virulent bacteria because of its high ability to cause disease - in part because it evades the host' immune system and in part because of its defense mechanisms, including biofilm formation and, as suggested in this article reporting on results from a murine model, its ability to colonize bone canaliculi.

The dermal pilosebaceous units of the skin overlying the shoulder - especially those in young men - are loaded with Cutibacterium. Investigations have shown that skin preparations are not effective in eliminating Cutibacterium from the dermis. Thus the incisions used for shoulder arthroplasty routinely allow Cutibacterium to enter the wound and potentially participate in the formation of a biofilm on the surface of the implant. 

Further research is needed to define ways to reduce the bacterial load that is introduced at the time of arthroplasty as well as the risk of subsequent biofilm formation.

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Here are some videos that are of shoulder interest
Shoulder arthritis - what you need to know (see this link).
How to x-ray the shoulder (see this link).
The ream and run procedure (see this link).
The total shoulder arthroplasty (see this link).
The cuff tear arthropathy arthroplasty (see this link).
The reverse total shoulder arthroplasty (see this link).
The smooth and move procedure for irreparable rotator cuff tears (see this link).
Shoulder rehabilitation exercises (see this link). 

Are Cutibacterium recovered from revision arthroplasty different from those found on normal skin?

Cutibacterium Recovered from Deep Specimens at the Time of Revision Shoulder Arthroplasty Samples Have Increased Biofilm Forming Capacity and Hemolytic Activity Compared to Cutibacterium Skin Isolates from Normal Subjects

It is apparent that Cutibacterium have two faces: benign commensal and pathogenic in shoulder periprosthetic infections (see this link).  

To explore this duality, these authors sought to compare the prevalence of Cutibacterium subtypes, biofilm formation and hemolytic activity between Cutibacterium recovered from 42 deep specimens obtained at the time of surgical revision for failed shoulder arthroplasty and Cutibacterium recovered from 43 samples of the skin from normal subjects.

Biofilm forming capacity and hemolytic activity were significantly higher in the tissue and explant samples compared to the control skin samples.  

Samples with hemolytic activity had significantly higher biofilm forming capacity compared to samples without hemolytic activity (0.27 ± 0.29 vs. 0.12 ± 0.15, p=0.015).

While there were significant differences in genetic subtypes between samples from revised shoulders and normal skin

the difference in biofilm forming capacity and hemolytic activity between genetic subtypes of Cutibacterium was not statistically significant in this study

Comment: These data add support for the view that Cutibacterium harvested from deep tissues are significantly different from those recovered from normal skin with respect to both genetic subtypes and phenotype (hemolysis and biofilm formation).

The lack of statistically significant correlation between Cutibacterium phenotypes and genetic subtype suggests that the observed differences in hemolytic activity and biofilm formation may relate at least in part to gene expression rather than to genetics. 

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How you can support research in shoulder surgery Click on this link.

Here are some videos that are of shoulder interest

Shoulder arthritis - what you need to know (see this link)

The smooth and move for irreparable cuff tears (see this link)

The total shoulder arthroplasty (see this link).

The ream and run technique is shown in this link.

The cuff tear arthropathy arthroplasty (see this link).

The reverse total shoulder arthroplasty (see this link).

Shoulder rehabilitation exercises (see this link).

Shoulder joint infections and biofilms

Cutibacterium is recognized as the most common organism recovered from failed shoulder joint replacements. Shoulder arthroplasty wounds are often inoculated by Cutibacterium released from the dermal pilocebaceous units when the skin is incised. When these planktonic (free floating) bacteria come in contact with prosthetic joint surfaces, they can form a biofilm that protects them from antibiotics and host defenses. Efforts to minimize the risk of periprosthetic infections focus on minimizing the size of the inoculum and on killing the introduced organisms before they have an opportunity to form a durable biofilm. 

Here are a few relevant articles

Biofilm formation by Propionibacterium acnes is a characteristic of invasive isolates

Propionibacterium acnes (Cutibacterium) has been shown to form biofilm both in vitro and

in vivo. These authors analyzed biofilm formation by 93 P. acnes isolates, either from invasive infections (n = 45) or from the skin of healthy people (n = 48). The majority of isolates from deep infections produced biofilm in a microtitre model of biofilm formation, whereas the skin isolates were poor biofilm producers (p <0.001 for a difference). They concluded that there was a role for biofilm formation in P. acnes virulence. The type distribution, as determined by sequencing of recA, was similar among isolates isolated from skin and from deep infections, demonstrating that P. acnes isolates with different genetic backgrounds have pathogenic potential. The biofilm formed on plastic and on bone cement was analysed by scanning electron microscopy (EM) and by transmission EM. The biofilm was seen as a 10-lm-thick layer covering the bacteria and was composed of filamentous as well as more amorphous structures. Interestingly, the presence of human plasma in solution or at the plastic surface inhibits biofilm formation, which could explain why P. acnes primarily infect plasma-poor environments

of, for example, joint prostheses and cerebrospinal shunts. This work underlines the importance of biofilm formation in P. acnes pathogenesis, and shows that biofilm formation should be considered in the diagnosis and treatment of invasive P. acnes infections.

Delayed Propionibacterium acnes surgical site infections occur only in the presence of an implant

These authors used a mouse model to compare the effects of P. acnes inoculation with an implant into the mouse femur to a control group with the bacteria but no implant. They observed the animals over a 6-month period using optical imaging system. During the first 2 weeks, bacterial signals were detected in the femur in the both groups. The bacterial signal completely disappeared in the control group within 28 days. Interestingly, in the implant group, bacterial signals were still present 6 months after inoculation. Histological and scanning electron-microscope analyses confirmed that P. acnes was absent from the control group 6 months after inoculation, but in the implant group, the bacteria had survived in a biofilm around the implant. PCR analysis also identified P. acnes in the purulent effusion from the infected femurs in the implant group. 

A Comparison of Bacterial Adhesion and Biofilm Formation on Commonly Used Orthopaedic Metal Implant Materials: An In vitro Study

These authors conducted an in vitro study is to evaluate the ability of Staphylococcus aureus, Staphylococcus epidermidis, Escherichia coli, Klebsiella pneumoniae, and Pseudomonas aeruginosa to adhere to and to form biofilms on the surface of five orthopaedic biomaterials: cobalt and chromium, highly cross-linked polyethylene, stainless steel, trabecular metal, and titanium alloy. While Cutibacterium was not included, they did include the second most common infecting organism for shoulder periprosthetic infections, S. epidermidis. They found that the highest level of adherence was observed on highly cross-linked polyethylene, followed by titanium, stainless steel, and trabecular metal, with the lowest occurring on the cobalt-chromium alloy. Among the bacterial strains tested, the ability for high adherence was observed with S. epidermidis and K. pneumoniaefollowed by P. aeruginosa and E. coli, whereas S. aureus showed the least adherence.

Cutibacterium acnes Biofilm Study during Bone Cells Interaction

These authors point out that Cutibacterium acnes can exist internally with osteoblast-like cells. For commensal strains, less than 1% of the bacteria were internalized.  C. acnes infection seems to have no cytotoxic effect on the bone cells. Commensal C. acnes showed a significant increase in biofilm formation after osteoblast-like internalization for 50% of the strains (2.8-fold increase). This phenomenon is exacerbated on a titanium, the material commonly used for shoulder implants. 

For the  strains associated with bone and prosthesis infections, they observed a similar internalization rate, but  did not notice any increase in biofilm formation. Fluorescent staining revealed more live bacteria within the biofilm after osteoblast-like cell interaction for all strains. They did not find any link between clinical origin and phylotype. 

Comparative analyses of biofilm formation among different Cutibacterium acnes isolates

These authors point out that Cutibacterium isolates exhibit marked heterogeneity and can be divided into at least 6 phylotypes by multilocus sequence typing and that biofilm formation may well be a relevant factor for Cutibacterium virulence. They performed a first comparative analysis of 58 diverse skin- or implant-isolates covering all six C. acnes phylotypes to investigate biofilm formation dynamics, biofilm morphology and attachment properties to abiotic surfaces. 

Their results suggest that biofilm formation correlates with the phylotype, rather than the anatomical isolation site. IA1 isolates, particularly SLST sub-types A1 and A2, showed highest biofilm amounts in the microtiter plate assays, followed by isolates of the IC, IA2 and II phylotypes.

Microscopic evaluation revealed well-structured three-dimensional biofilms and relatively high adhesive properties to abiotic surfaces for phylotypes IA1, IA2 and IC. 

Representatives of phylotype III formed biofilms with comparable biomass, but with less defined structures, whereas IB as well as II isolates showed the least complex three-dimensional morphology. 

Proteinase K- and DNase I-treatment reduced attachment rates of all phylotypes, therefore, indicating that extracellular DNA and proteins are critical for adhesion to abiotic surfaces. Moreover, proteins seem to be pivotal structural biofilm components as mature biofilms of all phylotypes were proteinase

K-sensitive, whereas the sensitivity to DNase I-treatment varied depending on the phylotype.

How you can support research in shoulder surgery Click on this link.

Here are some videos that are of shoulder interest

Shoulder arthritis - what you need to know (see this link).

How to x-ray the shoulder (see this link).

The total shoulder arthroplasty (see this link).

The ream and run technique is shown in this link.

The cuff tear arthropathy arthroplasty (see this link).

The reverse total shoulder arthroplasty (see this link).

The smooth and move procedure for irreparable rotator cuff tears (see this link).

Shoulder rehabilitation exercises (see this link).

Follow on twitter: Frederick Matsen (@shoulderarth)

Periprosthetic infections - the critical role of slime (biofilms) on the implants

 Methylene Blue Is an Effective Disclosing Agent for Identifying Bacterial Biofilms on Orthopaedic Implants

While this article concerns the use of methylene blue to indicate the presence of bacterial biofilms on implant surfaces, it also provides a useful review of the role of biofilms in periprosthetic infections (PJI). With respect to the shoulder it is recognized that the organism most commonly causing PJI, Cutibacterium, avidly forms biofilms on the most commonly used implant material, titanium alloy. See this link and this link.

The term 'biofilm' refers to bacteria embedded in an extracellular slime layer consisting of polysaccharides, extracellular DNA, proteins and lipids. Biofilms can develop channels allowing for diffusion of nutrients to the embedded bacteria. Because of the limited ability of oxygen to enter, the biofilm provides a range of environments from aerobic on the surface to anaerobic at the depth. Spatial separation of metabolic environments allows for niches for different types of bacteria. Bacteria in biofilms behave differently from those in the free-floating (planktonic) form.

Biofilms can form on all orthopaedic implants, including metal, plastic, and cement. They can be found in fibrous membranes surrounding implants. Because they are viscoelastic liquids, they can resist detachment and can flow across surfaces.

Biofilms protect bacteria from host defenses (1) forming conglomerates too large for phagocytosis by inflammatory cells and  (2) blocking antibodies from diffusing in to reach the bacteria. They also protect the bacteria from antibiotics such that the levels a 1000 times greater concentration is required to kill bacteria in biofilms in comparison to planktonic bacteria.

Biofilms make bacteria difficult to recover. Even though a prosthesis has a bacteria-ladened biofilm, joint fluid aspiration may well be negative because the bacteria are not present in the fluid. Bacteria in biofilms are not easily recovered because conventional culturing methods may not dislodge the biofilm. Even if the biofilm is recovered, host factors such as endonucleases may prevent the bacteria from growing. Bacteria in biofilms may enter a dormant or slow growing phenotype that grows slowly or not at all in cultures.

Essentially all periprosthetic infections involve biofilms. These can progress very slowly and may be non-symptomatic for years. Biofilm infections may exert their pathological effects by triggering insidious tissue damage (such as bone resorption) rather than by creating the usual signs of inflammation. Thus it may be very difficult to differentiate prosthetic loosening from the chronic effects of a biofilm from 'aseptic' mechanical loosening. These infections do not resolve spontaneously and usually require surgical debridement and antibiotics.

Biofilms may serve as sources of more obvious planktonic infection if the biofilm is stimulated or if the host is weakened.

These observations regarding biofilms have informed our current approach to failed shoulder arthroplasty.

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How dirty is your duck?

Ugly ducklings—the dark side of plastic materials in contact with potable water

Bath todays are in common use (see this link).

They pose an interesting insight into biofilm formation and flexible plastic materials, water, external microbial and nutrient contamination,

These authors characterized biofilm communities inside 19 bath toys used under real conditions. All examined bath toys revealed slimy biofilms on their inner surface.

Total bacterial numbers averaged 5.5 million cells/cm2 (clean water controls), 9.5 million cells/cm2 (real bath toys), and 74  million cells/cm2 (dirty water controls). Bacterial community compositions were diverse, showing many rare taxa in real bath toys and rather distinct communities in control bath toys, with a noticeable difference between clean and dirty water control biofilms.

The authors argue that bath toy biofilms are influenced by (1) the organic carbon leaching from the plastic material, (2) the chemical and biological water quality, (3) additional nutrients from care products and human body fluids in the bath water, as well as, (4) additional bacteria from dirt and/or the end-users’ microbiome.

They conclude that toys from real households are colonized by dense biofilms with complex bacterial and fungal communities.

Comment: The purpose of this post is to remind us that biofilms form on plastic as well as metal. Of interest is that the biofilm did not come off the plastic easily - it had to be removed using an electric toothbrush (Oral-B®, Advanced Power).

These findings may have relevance in the revision of the plastic components of a total shoulder when infection is suspected.

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What does an infected biofilm on a titanium implant look like?

Quantification of Peri-Implant Bacterial Load and in Vivo Biofilm Formation in an Innovative, Clinically Representative Mouse Model of Periprosthetic Joint Infection

These authors developed a murine PJI model involving a Ti-6Al-4V implant capable of bearing weight and permitting quantitative analysis of periprosthetic bacterial load and evaluation of biofilm.

Twenty-five mice received a unilateral proximal tibial implant and intra-articular injection of either Staphylococcus aureus containing saline or saline solution alone.

In contrast to the control mice, infected mice had difficulty walking over time, exhibited radiographic findings of septic implant loosening, and had significantly elevated inflammatory markers. Periprosthetic tissues and implant surfaces contained viable S. aureus.

Images of a pristine implant, showing the smooth tibial baseplate that resides in the articular space and the stem that resides in the intramedullary space, roughened with sintered titanium beads (arrows).

Below left - an implant retrieved from an infected animal 2 weeks following surgery, with bacteria visible adjacent to a titanium bead (star). Below right - magnified view of the boxed region of interest, showing clusters of S. aureus bacteria covered in biofilm consisting of several fibrin-like shapes, including straight fibers connecting bacteria (arrows).

Below left - an implant retrieved from an infected animal 6 weeks following surgery, showing adherent material consisting of cellular and fibrinous content. Below right - magnified view of the implant, showing a cluster of S. aureus bacteria covered in biofilm in the middle of the image, as well as a wall of fibrinous tissue filled with multiple layers of bacteria (arrows).

Below left - image from an infected implant 6 weeks following surgery, showing multiple host cells (arrowheads) covering titanium beads (stars) and the fibrin coating. Below right - magnified view of the same implant showing 3 S. aureus bacteria (arrows) surrounded by host leukocytes (yellow asterisks). A red blood cell is also noted in the field (red asterisk).

Comment: While these images are from an animal model infected with S. aureus, they are helpful reminders of how adherent bacteria can be to a Titanium implant surface. It is no wonder that such colonization cannot be resolved with systemic or local antibiotics. Implant exchange is the key.

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Prevention and treatment of propionibacterium biofilms

Prevention of Propionibacterium acnes biofilm formation in prosthetic infections in vitro

These authors studied biofilm formation on synthetic calcium sulfate (CaSO4) bone void filler beads using scanning electron microscopy (SEM) over a period of 14 days.

Here are some SEM photographs of Propionibacterium biofilm formation on the surface of an unloaded pharmaceutical-grade calcium sulfate alpha-hemihydrate bead over a period of 14 days. Surface colonization was observed at day 3 with evidence of extracellular polymeric substance (EPS) strands  (indicated by arrows), with small microcolonies noted at day 7 with more extensive EPS deposition. At day 14, biofilm was observed across  the bead surface over a matted layer of EPS. Scale bars equal 10 μm.

Beads loaded with vancomycin/tobramycin were able to kill planktonic cultures of 106 colony-forming units/mL, prevent bacterial colonization, and significantly reduce biofilm formation over periods of weeks. 

Here is a graph showing Propionibacterium biofilm formation over a period of 14 days in the presence of antibiotic-loaded pharmaceutical-grade calcium sulfate alpha-hemihydrate (PG-CSH) beads as determined by confocal laser scanning microscopy images and colony-forming unit (CFU) counts (CFUs per square centimeter). Data represent the mean of 3 experimental repeats (15 data points, n = 5 per experimental repeat) with standard deviation bars. Arrows indicate a fresh bacterial challenge of 106 CFU/mL every 72 hours. Scale bars equal 25 μm.

Comment: This is an interesting study showing the effectiveness of local antibiotic elution from calcium sulfate beads in preventing and treating Propionibacterium biofilms in vitro. Future in vivo models and clinical experience will help define the role of this approach for prophylaxis in high risk patients and in treatment for patients suspected of having Propionibacterium infections. 

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Consultation for those who live a distance away from Seattle.

Click here to see the new Shoulder Arthritis Book

Click here to see the new Rotator Cuff Book

Use the "Search" box to the right to find other topics of interest to you.

You may be interested in some of our most visited web pages including:shoulder arthritis, total shoulder, ream and run, reverse total shoulder, CTA arthroplasty, and rotator cuff surgery as well as the 'ream and run essentials'

See from which cities our patients come.

See the countries from which our readers come on this post.