Culturing for Cutibacterium at revision surgery

The role of implant sonication in the diagnosis of periprosthetic shoulder infection

These authors spought to investigate the value of implant sonication fluid cultures in the diagnosis of shoulder periprosthetic joint infection (PJI) compared with tissue culture. They conducted a retrospective case-control study analyzing all patients who underwent a revision surgery for any kind of suspected septic or aseptic event due to failed shoulder arthroplasty.

Of the 72 patients, a total of 28 (38.9%) were classified as infected. Of the 28 infected patients, 20 (71.4%) had an identified organism by tissue cultures.


Of all infected patients, 71.4% (20/28 patients) had an identified organism by tissue cultures, and C acnes was the most commonly isolated pathogen, in 13/28 patients (46%), followed by coagulase-negative staphylococci (5/28, 17.9%), Staphylococcus aureus (2/28, 7%), Finegoldia magna (1/28, 3.6%), Streptococcus agalactiae (1/28, 3.6%), Enterococcus faecalis (1/28, 3.6%), and Peptoniphilus asaccharolyticus (1/28, 3.6%).

The sensitivities of sonicate fluid (50 CFU/mL) and periprosthetic tissuebculture for the diagnosis of periprosthetic shoulder infection were 36% and 61% (P . .016), and the specificities were 97.7% and 100%, respectively. If no cutoff value was used in sonication culture, the sensitivity increased to 75% whereas the specificity dropped to 82%. Although there was no significant difference in sensitivity between tissue culture and the no-cutoff sonication fluid culture (61% vs. 75%), the specificity of tissue culture was significantly higher (100% vs. 82%,).

The authors concluded that tissue culture showed a higher sensitivity and specificity than implant sonication in the diagnosis of shoulder PJI and should remain the gold standard for microbiological diagnosis of shoulder PJI.

Comment: It is not a question of either explant or tissue cultures. We have found that both tissue and explant cultures are of importance in the detection of a periprosthetic infection. In their study it is possible that the authors missed the opportunity to recover bacteria in over 25% of their cases because in some cases they only submitted two specimens to the laboratory.

Because Cutibacterium are not evenly dispersed throughout an infected shoulder it is critical that five deep specimens be submitted for culture, in that even if the shoulder is infected, some specimens may show no growth. Recall that titanium alloy provides a surface that is attractive for Cutibacterium biofilm formation; this in some cases the explant cultures are positive while the tissue cultures are negative.

Our routine is to culture synovium, collar membrane, humeral membrane, and all explanted prostheses. Explants are vortexed in 3 cc of saline to remove the biofilm, but sonication has not been shown to be of added value.

Here is a relevant poster from a recent American Shoulder and Elbow Surgeons meeting

Should Explants Be Cultured at Revision Shoulder Arthroplasty?

Background:Surgeons revising a failed arthroplasty need to know whether or not bacteria are present around the implanted components.  The specimen harvesting and culturing practices used to recover bacteria at revision surgery vary among surgeons, some including only tissue and others including both tissue and removed component explants. Culturing explants has the potential benefit of revealing organisms residing in biofilms on their surface that might otherwise be overlooked. The purpose of this study was to assess the added value of culturing explants in seeking evidence of Propionibacteriumat revision arthroplasty. We sought to answer three questions:

1. Does culturing of explants (in addition to tissue cultures) facilitate the recovery of Propionibacteriumfrom revised shoulder arthroplasties?

2. In Propionibacteriumculture-positive shoulders, how does the Propionibacteriumload from explant cultures compare with the load from tissue cultures?

3. In Propionibacteriumculture-positive shoulders, are some anatomic areas more likely to have positive cultures?

Methods:From December 2015 until March 2018, 122 revision arthroplasties were consented for inclusion in a revision shoulder arthroplasty database. Specimens were submitted for standardized Propionibacterium culturing of tissue from the collar membrane, humeral canal, and periglenoid area as well as explants of the humeral head, humeral stem, and glenoid components. In this analysis we included only those shoulders that had both tissue and explant culture results from three anatomically similar locations: 1) HEAD region: collar membrane tissue and humeral head explant (n=86), 2) STEM region: humeral canal tissue and humeral stem explant (n=58), or 3) GLENOID region: periglenoid tissue and glenoid explant (n=45). Tissue samples were placed in a stomacher with saline, and the saline was streaked onto three different anaerobic and aerobic media and observed for 21 days. Explanted components were vortexed with saline, and the saline was streaked in a similar fashion. Semiquantitative culture results were reported for each specimen as the Specimen Propi Value (SpPV). We analyzed the results for two threshold values: SpPV>0 and for SpPV≥1. 

Results:For both thresholds, inclusion of explant cultures increased the percentages of cultures that were positive. 

Importantly, explants were culture positive in shoulders in which the tissue specimens were negative in 6 of 30 (20%) HEAD specimens, 8 of 24 (33%) STEM specimens, and 9 of 19 (47%) GLENOID specimens. The PropionibacteriumSpPVs were similar between positive explant and tissue specimens in the HEAD region (tissue 1.0 ± 0.8 vs. explant 1.5 ± 1.1, p=0.144), STEM region (tissue 1.2 ± 1.0 vs. explant 1.3 ± 1.1, p=0.873), and GLENOID region (tissue 1.0 ± 0.6 vs. explant 0.8 ± 0.8). The percentage of positive tissue or explant specimens were similar between anatomic sites: the HEAD specimens were positive in 30 of 86 (35%) samples, STEM 24 of 58 (41%), and GLENOID 19 of 45 (42%). 

Conclusion:In this study, inclusion of explant cultures increased the percentages of cultures positive for Propionibacteriumat each of three anatomic sites. These findings suggest that the identification of Propionibacterium in revision arthroplasty is more likely if removed implants are submitted for culture. This increase may be due to the detection of bacteria in implant biofilms in cases where it was not detectable in tissue samples.  

And here are some related studies

Performance of implant sonication culture for the diagnosis of periprosthetic shoulder infection

Sonication versus Vortexing of Implants for Diagnosis of Prosthetic Joint Infection

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Does implant sonication help in the diagnosis of periprosthetic shoulder infection?

Performance of implant sonication culture for the diagnosis of periprosthetic shoulder infection

These authors performed routine perioperative testing in 53 patients who underwent revision shoulder arthroplasty. In addition to routine tissue and fluid culture, the retrieved shoulder implants underwent sonication with culture of the sonicate fluid.

25 (47%) were classified as infected. Propionibacterium was the identified pathogen in 19 of 25 cases. Other cultured organisms were CNSS (4/25 [16%]), methicillin resistant Staphylococcus aureus (2/25 [8%]), group B streptococcus (1/25 [4%]), and Enterobacter cloacae (1/25 [4%]). Two (8%) cases were polymicrobial, with both CNSS and P. acnes identified in each. 

Using the cutoff value of >20 colony forming units (CFU)/mL to exclude contaminants, implant sonication culture had a low sensitivity (56%) but high specificity (93%) .

Without using a cutoff value, implant sonication culture had a high sensitivity (96%) but low specificity (64%). 

Standard intraoperative cultures (tissue and fluid) had a better overall performance compared with the cutoff and non-cutoff sonication results.

The authors concluded that implant sonication fluid culture in revision shoulder arthroplasty showed no significant improvement in diagnostic utility over standard intraoperative cultures.

Comment: In our laboratory, explanted prosthesis are submitted to vortexing, which is an alternative approach to sonication for shaking loose bacteria that may be encased in a biofilm on the implant. Our experience indicates that implants studied in this way provide an important source of culture positive specimens harvested at the time of revision arthroplasty. In a recent study (see this link) only 32.6% of the fluid cultures were positive in comparison with 66.5% of the soft-tissue cultures and 55.6% of the cultures of the explant specimens.

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The reader may also be interested in these posts:

Healing through joint replacement

Supporting progress in shoulder surgery

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Information about shoulder exercises can be found at this link.

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'

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Periprosthetic shoulder infection - is sonication of implants helpful in the diagnosis

Performance of implant sonication culture for the diagnosis of periprosthetic shoulder infection

These authors sough to evaluate the utility of implant sonication in the diagnosis of periprosthetic joint infection in patients undergoing revision shoulder arthroplasty between August 2010 and April 2013.  There were 5 patients with 2 cultures, 12 patients with 3 cultures, 9 patients with 4 cultures, 9 patients with 5 cultures, 14 patients with 6 cultures, 3 patients with 7 cultures, and 1 patient with 8 cultures. Preoperative fluid was obtained in 36 of 53 cases, and intraoperative fluid was obtained in 36 of 53 cases. Of the 53 revision cases that underwent implant sonication fluid culture, 25 (47%) were classified as infected. Their results are shown below

They concluded that implant sonication fluid culture in revision shoulder arthroplasty showed no significant benefits over standard intraoperative cultures in diagnostic utility for periprosthetic joint infection.

Conclusion: Sonication has been proposed as a means for removing organisms in the biofilm of retrieved implants. It is an expensive process and at present is without substantial evidence supporting its use. Our practice is to culture retrieved implants by vortexing them in 3 cc of sterile saline and submitted the saline for standard culturing for Propionibacterium and other organisms.

In contrast to their cases from the era presented here, these authors now carefully standardize their culturing protocol for revision shoulder arthroplasty to include the harvest of 5 intraoperative specimens: a synovial fluid sample and four tissue samples with all specimens sent for 14 day anaerobic culture hold. This degree of standardization is essential for interpreting the culture results. 

The topic of sonication is also discussed here:

The authors of Sonication versus Vortexing of Implants for Diagnosis of Prosthetic Joint Infection
compared sanitation (shaking) versus vortexing (stirring) with respect to the biofilm removal efficacy of vortexing alone in 135 removed prostheses, 35 were diagnosed with infection and 100 with aseptic failure. They used two different cutoffs for a positive result: 1 colony forming unit (CFU) or 50 CFU.

Using a cutoff of >50 CFU/ml, sonication showed higher sensitivity than vortexing (60% versus 40%) (p = 0.151), while the specificities remained equal (99%). Using the lower cutoff value (>CFU/ml), the sensitivities of vortexing and sonication fluid were similar (69% to 71%); however, the specificities decreased to 92% to 93%. In the table below PJI were cases they defined as infection and AF were thought to be aseptic failure.

It is of note that only two of these cases involved the shoulder and only 5 of the recovered organisms were Propionibacterium.

Comment: These authors provide a nice commentary on their work : "Interestingly, vortexing alone demonstrated acceptable sensitivity and specificity, especially in acute PJI, and may be used for the diagnosis of PJI in laboratories where sonication is not available. In addition, vortexing fluid represents a single clinical sample, with such analyses reaching sensitivity comparable to that of analyses using multiple periprosthetic tissue cultures (∼70%). Furthermore, sonication may kill bacteria, especially Gram-negative bacilli and anaerobes, whereas vortexing has not been shown to be harmful to bacteria. In addition, vortexing is an easy and simple procedure which can be performed in most laboratories without additional costs. Despite vortexing having originally been introduced as a preparatory step before sonication to generate microbubbles, which increase the cavitation effect, it seems to be a powerful removal method. High shear forces generated on the interface between the prosthesis and the vortexing fluid may explain the biofilm removal effect. These shear forces could be increased by a pulsatile change of the fluid movement direction (as used in Stomacher analysis). The removal efficiency may be also increased by addition of detergents (e.g., polysorbate 80) or anticoagulants (e.g., EDTA) to the vortexing fluid. Another possibility is the addition of beads to vortexing fluid, as is used for processing tissue samples in a bead mill. However, the contamination risk, increased workload, and costs need to be considered"

Our laboratory has determined that the potential incremental benefit of sonication does not offset the incremental cost and time.

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The reader may also be interested in these posts:

Healing through joint replacement

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

Information about shoulder exercises can be found at this link.

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.

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Culturing explant biofilms - shaken or stirred

Many of our readers are familiar with James Bond's martini preference: shaken but not stirred.

The authors of Sonication versus Vortexing of Implants for Diagnosis of Prosthetic Joint Infection
compared sanitation (shaking) versus vortexing (stirring) with respect to the biofilm removal efficacy of vortexing alone in 135 removed prostheses, 35 were diagnosed with infection and 100 with aseptic failure. They used two different cutoffs for a positive result: 1 colony forming unit (CFU) or 50 CFU.

Using a cutoff of >50 CFU/ml, sonication showed higher sensitivity than vortexing (60% versus 40%) (p = 0.151), while the specificities remained equal (99%). Using the lower cutoff value (>CFU/ml), the sensitivities of vortexing and sonication fluid were similar (69% to 71%); however, the specificities decreased to 92% to 93%. In the table below PJI were cases they defined as infection and AF were thought to be aseptic failure.

It is of note that only two of these cases involved the shoulder and only 5 of the recovered organisms were Propionibacterium.

Comment: These authors provide a nice commentary on their work : "Interestingly, vortexing alone demonstrated acceptable sensitivity and specificity, especially in acute PJI, and may be used for the diagnosis of PJI in laboratories where sonication is not available. In addition, vortexing fluid represents a single clinical sample, with such analyses reaching sensitivity comparable to that of analyses using multiple periprosthetic tissue cultures (∼70%). Furthermore, sonication may kill bacteria, especially Gram-negative bacilli and anaerobes, whereas vortexing has not been shown to be harmful to bacteria. In addition, vortexing is an easy and simple procedure which can be performed in most laboratories without additional costs. Despite vortexing having originally been introduced as a preparatory step before sonication to generate microbubbles, which increase the cavitation effect, it seems to be a powerful removal method. High shear forces generated on the interface between the prosthesis and the vortexing fluid may explain the biofilm removal effect. These shear forces could be increased by a pulsatile change of the fluid movement direction (as used in Stomacher analysis). The removal efficiency may be also increased by addition of detergents (e.g., polysorbate 80) or anticoagulants (e.g., EDTA) to the vortexing fluid. Another possibility is the addition of beads to vortexing fluid, as is used for processing tissue samples in a bead mill. However, the contamination risk, increased workload, and costs need to be considered"

Our laboratory has determined that the potential incremental benefit of sonication does not offset the incremental cost and time.
However, we recognize the importance of dislodging bacteria ensconced in a biofilm if we are to be able to detect their presence in failed shoulder arthroplasty. We await further evidence on the value of sonication in recovering Propionibacterium from shoulder implants.

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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.