Does hydrogen peroxide application to the dermis following surgical incision affect Cutibacterium acnes cultures in total shoulder arthroplasty in male patients? A randomized controlled trial.

BACKGROUND: Periprosthetic joint infections occur in 1%-4% of primary total shoulder arthroplasties (TSAs). Cutibacterium acnes is the most commonly implicated organism and has been shown to persist in the dermis despite use of preoperative antibiotics and standard skin preparations. Studies have shown decreased rates of cultures positive for C acnes with use of preoperative benzoyl peroxide or hydrogen peroxide (H2O2), but even with this positive deep cultures remain common. We sought to determine whether an additional application of H2O2 directly to the dermis following skin incision would further decrease deep culture positivity rates. METHODS: We performed a randomized controlled trial comparing tissue culture results in primary TSA in patients who received a standard skin preparation with H2O2, ethanol, and ChloraPrep (CareFusion, Leawood, KS, USA) vs. an additional application of H2O2 to the dermis immediately after skin incision. Given the sexual dimorphism seen in the shoulder microbiome regarding C acnes colonization rates, only male patients were included. Bivariable and multivariable analyses were performed to compare rates of positive cultures based on demographic and surgical factors. RESULTS: Dermal cultures were found to be positive for C acnes at similar rates between the experimental and control cohorts for the initial (22% vs. 28%, P = .600) and final (61% vs. 50%, P > .999) dermal swabs. On bivariable analysis, the rate of positive deep cultures for C acnes was lower in the experimental group, but this difference was not statistically significant (28% vs. 44%, P = .130). However, patients who underwent anatomic TSA were found to have a significantly greater rate of deep cultures positive for C acnes (57% vs. 28%, P = .048); when controlling for this on multivariable analysis, the experimental cohort was found to be associated with significantly lower odds of having positive deep cultures (odds ratio, 0.37 [95% confidence interval, 0.16-0.90], P = .023). There were no wound complications in either cohort. CONCLUSIONS: An additional H2O2 application directly to the dermis following skin incision resulted in a small but statistically significant decrease in the odds of having deep cultures positive for C acnes without any obvious adverse effects on wound healing. Given its cost-effectiveness, use of a post-incisional dermal decontamination protocol may be considered as an adjuvant to preoperative use of benzoyl peroxide or H2O2 to decrease C acnes contamination.

The incidence of subclinical infection in patients undergoing revision shoulder stabilization surgery: a retrospective chart review.

BACKGROUND: Shoulder instability continues to be a common problem that is difficult to treat. Part of this difficulty can be attributed to the numerous postoperative complications that can impact the clinical course. Our study aims to primarily identify the incidence of subclinical infection in patients undergoing revision shoulder stabilization surgery and secondarily identify any risk factors for developing a subclinical infection. MATERIALS AND METHODS: From January 2012 to December 2022, 94 charts of patients who underwent revision surgery by the senior author after a previous arthroscopic or open stabilization surgery for shoulder instability were reviewed. All patients of any age who underwent either bony or soft tissue revision surgery, regardless of the number of previous surgeries or corticosteroid injections, were included. Patients were excluded if they had a previous infection in the shoulder, if there was no record of the procedures performed in the previous surgery, or if cultures were not available for review. For each patient, demographic information (age, sex, race, smoking status, previous corticosteroid injections, malnutrition, renal failure, liver failure, diabetes mellitus, immunocompromised status, and intravenous drug use), surgical information (procedures performed, type of surgery, and date of surgery), and culture results were recorded. RESULTS: Overall, 107 patients were included in our study. Twenty-nine patients (27.1%) had positive cultures (60 cultures in total). Twenty-six patients had positive Cutibacterium acnes (C. acnes) cultures. On average, C. acnes cultures took 10.65 days to turn positive, whereas 24 of 27 patients had cultures that were positive within 14 days of the culture being obtained. There was no difference in infection incidence rates between soft tissue and bony stabilization procedures (P = .86) or arthroscopic and open procedures (P = .59). Males were more than 5 times more likely than females to be culture positive in our cohort (93.1% vs. 73.1%, relative risk [RR] = 1.27, P = .03). Finally, 10 control cultures were taken from the operating room air environment (8 distinct surgeries had 1 control culture taken, whereas 1 surgery had 2), 2 of which were positive for C. acnes (both taken from the same patient operation). This patient had their shoulder cultures positive for C. acnes as well. CONCLUSION: More than a quarter of patients requiring revision surgery after shoulder stabilization procedures have a subclinical shoulder infection, with males being at a higher risk of developing an infection than females. Surgeons should always consider infection as a reason for the lack of clinical improvement and possibly needing revision surgery after shoulder stabilization. The prompt diagnosis and treatment of these infections could be vital in improving results after these surgeries.

Effect of making skin incision with electrocautery on positive Cutibacterium acnes culture rates in shoulder arthroplasty: a prospective randomized clinical trial.

BACKGROUND: Cutibacterium acnes remains the most commonly detected organism in shoulder arthroplasty. C acnes infection is thought to occur during shoulder arthroplasty through contamination of the surgical field with C acnes from the incised dermis. The purpose of this study was to examine whether using electrocautery for making skin incisions would decrease C acnes culture rates at the incised dermis compared to using scalpels during shoulder arthroplasty. METHODS: Patients undergoing primary shoulder arthroplasty were randomized into 2 groups, electrocautery vs. scalpel incision group. All patients received a standard preoperative antiseptic preparation including chlorhexidine gluconate showers, intravenous antibiotic administration, and topical application of hydrogen peroxide, povidone iodine, isopropyl alcohol, and DuraPrep. Cultures were obtained from the incised dermal edge immediately after skin incision and later from surgeon's gloves and forceps immediately prior to humeral component implantation. The primary outcome was positive C acnes culture rates compared between the groups. RESULTS: A total of 64 patients (32 in each group) were enrolled. There were 24 males in each group. Regarding dermis cultures, 10 patients (31%) in the scalpel group were positive with 8 of them positive for C acnes, whereas no patients in the electrocautery group were positive (P < .001). Regarding glove cultures, the electrocautery group had 8 patients positive C acnes, while the scalpel group had 8 (P = .777). Regarding forceps cultures, the electrocautery group had 4 patients positive for C acnes, and the scalpel group had 6 (P = .491). All positive cultures were exclusively from male patients. There were no wound complications or infection in the electrocautery group while the scalpel group had 1 acute postoperative infection. CONCLUSIONS: Making skin incisions using electrocautery resulted in 0 C acnes culture at the incised dermis, suggesting its potential effect against C acnes. However, despite this initial antibacterial effect, C acnes still appeared on surgeon's gloves and forceps during surgery of male patients. All positive cultures were from male patients, suggesting that the source of C acnes was specifically related to the male body. While the study hypothesis was supported by the results, the present study also raises new questions and calls for further research.

Infection in Shoulder Arthroplasty: Prevention, Diagnosis, and Treatment.

Prosthetic joint infection is a devastating complication following shoulder arthroplasty that can lead to pain, poor function, and poor quality of life. With the increasing number of shoulder arthroplasties performed annually, recognition of prosthetic infection and treatment is necessary. The skin surrounding the shoulder has a unique microbiome, and Cutibacterium acnes is the most commonly encountered bacteria causing prosthetic joint infection. C acnes is a low-virulence organism that resides in the subcutaneous layer of the skin. As a result, the clinical presentation is typically less obvious than prosthetic infections seen in other joints such as the hip and knee. Therefore, diagnosis is not always straightforward, and optimal treatment strategy is unclear. Guidance on prevention, diagnosis, and treatment of shoulder prosthetic joint infection with special emphasis on the consensus definition established at the 2018 International Consensus Meeting is provided.

Functional outcomes and complications of patients contaminated with Cutibacterium acnes during primary reverse shoulder arthroplasty: study at two- and five-years of follow-up.

PURPOSE: The objective of the study was to compare the functional outcomes and the complication rate of the patients with C. acnes contamination at the end of the primary reverse shoulder arthroplasty (RSA) surgery to those patients without C. acnes contamination. METHOD: A total of 162 patients were included. In all cases, skin and deep tissue cultures were obtained. A molecular typing characterization of the C. acnes strains was performed. Functional outcomes were assessed with the Constant score at the two and five year follow-up and all complications were also recorded. RESULTS: A total of 1380 cultures were obtained from the 162 primary RSA surgeries. Of those, 96 turned out to be positive for C. acnes. There were 25 patients with positive cultures for C. acnes. The overall postoperative Constant score was not significantly different between those patients having C. acnes-positive cultures and those with negative cultures at the two and five year follow-up (59.2 vs. 59.6 at two years, p 0.870, and 59.5 vs. 62.4 at five years, p 0.360). Patients with positive cultures presented a higher complication rate (p 0.001) with two infections, one revision surgery, and one dislocation. CONCLUSION: Patients ending up with C. acnes-positive cultures after primary shoulder arthroplasty surgery do not have worse clinical outcomes when compared to patients having negative cultures, but a greater number of complications were found in those patients with C. acnes-positive cultures.

The POSI study: gender differences in 94 cases of postoperative shoulder surgery infection: results of a 7-year retrospective multicenter study.

BACKGROUND: Contrary to lower limb infection, POstoperative Shoulder surgery Infection (POSI) often involves Cutibacterium acnes. Our aim was to describe patient characteristics and pathogens retrieved in POSI to guide initial empiric antibiotic selection with suspected infection during revision. We also compared microorganisms in infection following trauma, arthroplasty (AP), and arthroscopy (AS). METHODS: A multicenter retrospective study from 2010 to 2016 reviewed laboratory databases and medical records to identify patients with a previous shoulder surgery and a confirmed shoulder infection. The following procedures were included: AP, AS, fracture fixation (FF), and another open surgery (OS). A confirmed shoulder infection was defined as 2 positive cultures or more of the same microorganism, or clear clinical infection with 1 positive culture or more. RESULTS: Among the 5 hospitals and 28 surgeons involved, 94 POSI cases were identified. Mean age was 59 years at index surgery (range: 22-91) with a majority of men (n = 70, 74%). Among POSI cases, AP was the most common index surgery (n = 41), followed by FF (n = 27), AS (n = 16), and OS (n = 10). The median time between index surgery and the first positive sample was 5 months and the mean was 23 months (minimum 6 days to maximum 27 years), illustrating a positively skewed distribution. Cutibacterium spp were identified in 64 patients (68%), including 59 C acnes patients (63%), which was the most frequent germ in all 4 surgical groups. In 86% of cases, C acnes was identified at the first revision. The other 2 most common germs were Staphylococcus epidermidis and Staphylococcus aureus, with 29% and 17%, respectively. Polymicrobial infection was present in 30% of patients. Gender analysis revealed that C acnes was twice as frequent in men (male = 52 of 70, female = 7 of 24; P < .001). S epidermidis was more prevalent in women (n = 11; 46%) compared with men (n = 16; 21%) (P = .032). C acnes infection was most frequent in arthroscopic surgery (n = 14; 70%, P = .049). S epidermidis was 3 times more prevalent in chronic than in acute cases. CONCLUSION: Empiric antimicrobial therapy following POSI, while waiting for culture results, should cover C acnes, S epidermidis, and S aureus. There is a significant gender difference regarding POSI culture results. C acnes is more frequent in men, but should still be covered in women as it was found in 29% of cases.

Success of staged revision reverse total shoulder arthroplasty in eradication of periprosthetic joint infection.

INTRODUCTION: Management of periprosthetic joint infection (PJI) in shoulder arthroplasty remains a challenge, with no established gold standard treatment. This study presents the unique experience of a high-volume single-surgeon, single-institution approach on staged revision reverse total shoulder arthroplasty (RTSA) for infection. The authors theorize that staged revision RTSA is an effective treatment for PJI. MATERIALS AND METHODS: Between 2013 and 2018, 38 patients underwent a staged RTSA for treatment of PJI. Patient histories were collected and classified using Cierny-Mader classification. Infection workup for all patients included radiographs, laboratory indices, and computed tomographic aspiration arthrogram. PJI was identified based on high clinical and radiographic suspicion, elevated serologic markers, and/or aspirate culture results per 2018 International Consensus Meeting Shoulder guidelines on Orthopedic Infections. All patients underwent first stage with implant removal, irrigation and débridement, and antibiotic spacer placement. Next, intravenous antibiotics were administered by infectious disease consultants for a minimum of 6 weeks. Infection workup was then repeated and, if normalized, final-stage revision commenced with antibiotic spacer removal and revision to RTSA. If indices were persistently abnormal, an additional stage of débridement and spacer placement procedure was performed. Treatment failure was defined as recurrent periprosthetic infection after final prosthesis implantation or persistently elevated indices despite adequate débridement and spacer placement. RESULTS: Mean age of the cohort was 68 (standard deviation [SD] 8.9) years and mean follow-up was 33 (SD 14) months with 34 Cierny-Mader C hosts and 4 B hosts. Patients underwent a mean of 2 (SD 1.1) previous surgeries. The staged revision protocol was successful in 34 (89.5%) patients for management of PJI. Four patients (10.5%) were considered failures with recurrent infections at a mean of 13 months (range 2-26 months) after the final RTSA implantation and underwent repeat staged revisions. Of the 34 patients who had successful infection eradication, 31 had 2-stage treatment and 3 had to undergo 3 stages. There were no treatment-associated mortalities and 10 major complications (26%), including permanent neuropathy, instability, and periprosthetic fractures. The most common cultured microorganism was Cutibacterium acnes (18%), with no polymicrobial infections detected. DISCUSSION: Although there are multiple treatment options for PJI management, staged revision remains an effective means of treatment. Although there were several patients who required an additional stage of treatment, and a significant complication rate, staged revision RTSA proved successful in the ultimate eradication of the PJI.

Minimal number of cultures needed to detect Cutibacterium acnes in primary reverse shoulder arthroplasty: a prospective study.

BACKGROUND: The objective of this study was to determine the minimum number of cultures needed to detect Cutibacterium acnes in primary reverse shoulder arthroplasties (RSAs). METHODS: It is a prospective study including 160 primary RSAs. Exclusion criteria included an active infection, an invasive shoulder treatment in the last 6 months before surgery, an Arthro-SCAN or Arthro-MRI in the last 6 months before surgery, previous shoulder surgeries and revision cases. In 90 cases, 11 cultures were obtained. Another 10 cultures were obtained in the other 70 cases (culture 10 was a sterile sponge to detect false positives). To determine the minimum number of cultures needed to detect C acnes, the prevalence of C acnes contamination of the 160 patients included was determined. RESULTS: There were 128 females and 32 males, with a mean age of 74 years. There were 1690 cultures obtained from the 160 primary RSA surgeries, and 132 of them turned out to be positive for C acnes. There were 42 patients with positive cultures. Twenty of them were males and 22 females. When considering the skin and the deep tissue cultures altogether, the prevalence of positive cultures for C acnes was of 26.25%. If only deep tissues cultures were considered, the prevalence of positive cultures for C acnes was of 23.13%. When considering the skin and the deep tissue cultures together, the sensitivity to detect the C acnes is 19% if only 1 culture is obtained, 31% if 2 cultures are obtained, 50% if 3 cultures are obtained, 59.5% if 4 cultures are obtained, 66.7% if 5 cultures are obtained, 73.8% if 6 cultures are obtained, 85.7% if 7 cultures are obtained, and 92.9% if 8 cultures are obtained. When considering only the deep tissue cultures, if only 1 culture is obtained, the sensitivity to detect the C acnes is 24.3%, 40.5% if 2 cultures are obtained, 54.1% if 3 cultures are obtained, 73% if 4 cultures are obtained, 89.2% if 5 cultures are obtained, and 97.3% if 6 or 7 cultures are obtained. DISCUSSION: A minimum number of 8 cultures are needed to detect C acnes in skin. Moreover, a minimum of 6 cultures are needed to detect it in deep tissues when performing an RSA.

Short-term Clinical Outcomes of Unexpected Culture-positive Cutibacterium acnes (Formerly Propionibacterium acnes) in Open Orthopaedic Surgery.

INTRODUCTION: The clinical significance and treatment recommendations for an unexpected positive Cutibacterium acnes (C acnes) culture remain unclear. The purpose of our study was to evaluate the clinical effect of a C acnes positive culture in patients undergoing open orthopaedic surgery. METHODS: Patients with a minimum of one positive C acnes intraoperative culture were retrospectively reviewed over a 7-year period. True C acnes infection was defined as culture isolation from ≥1 specimens in the presence of clinical or laboratory indicators of infection. RESULTS: Forty-eight patients had a positive intraoperative C acnes culture. 4.2% had a C acnes monoinfection, and 12.5% of the patients had a coinfection. The remainder was classified as indeterminate. Significant differences were identified between the indeterminate and true C acnes infection groups, specifically in patients with surgery history at the surgical site (P = 0.04), additional antibiotic therapy before surgery (P < 0 .001), and postoperative clinical signs of infection (P < 0 .001). DISCUSSION: Suspicion for true C acnes infection should be raised in patients with surgery site history, antibiotic therapy before surgery, and clinical infectious signs. The indeterminate unexpected positive culture patients had a low risk of developing a true clinical infection that required antibiotic therapy.

Diagnostic Performance of Advanced Metal Artifact Reduction MRI for Periprosthetic Shoulder Infection.

BACKGROUND: The diagnosis of periprosthetic shoulder infection (PSI) in patients with a painful arthroplasty is challenging. Magnetic resonance imaging (MRI) may be helpful, but shoulder implant-induced metal artifacts degrade conventional MRI. Advanced metal artifact reduction (MARS) improves the visibility of periprosthetic bone and soft tissues. The purpose of our study was to determine the reliability, repeatability, and diagnostic performance of advanced MARS-MRI findings for diagnosing PSI. METHODS: Between January 2015 and December 2019, we enrolled consecutive patients suspected of having PSI at our academic hospital. All 89 participants had at least 1-year clinical follow-up and underwent standardized clinical, radiographic, and laboratory evaluations and advanced MARS-MRI. Two fellowship-trained musculoskeletal radiologists retrospectively evaluated the advanced MARS-MRI studies for findings associated with PSI in a blinded and independent fashion. Both readers repeated their evaluations after a 2-month interval. Interreader reliability and intrareader repeatability were assessed with κ coefficients. The diagnostic performance of advanced MARS-MRI for PSI was quantified using sensitivity, specificity, and the area under the receiver operating characteristic curve (AUC). When applying the International Consensus Meeting (ICM) 2018 criteria, of the 89 participants, 22 (25%) were deemed as being infected and 67 (75%) were classified as being not infected (unlikely to have PSA and not requiring a surgical procedure during 1-year follow-up). RESULTS: The interreader reliability and intrareader repeatability of advanced MARS-MRI findings, including lymphadenopathy, joint effusion, synovitis, extra-articular fluid collection, a sinus tract, rotator cuff muscle edema, and periprosthetic bone resorption, were good (κ = 0.61 to 0.80) to excellent (κ > 0.80). Lymphadenopathy, complex joint effusion, and edematous synovitis had sensitivities of >85%, specificities of >90%, odds ratios of >3.6, and AUC values of >0.90 for diagnosing PSI. The presence of all 3 findings together yielded a PSI probability of >99%, per logistic regression analysis. CONCLUSIONS: Our study shows the clinical utility of advanced MARS-MRI for diagnosing PSI when using the ICM 2018 criteria as the reference standard. Although the reliability and diagnostic accuracy were high, these conclusions are based on our specific advanced MARS-MRI protocol interpreted by experienced musculoskeletal radiologists. Investigations with larger sample sizes are needed to confirm these results. LEVEL OF EVIDENCE: Diagnostic Level III . See Instructions for Authors for a complete description of levels of evidence.

An evidence-based approach to managing unexpected positive cultures in shoulder arthroplasty.

BACKGROUND: Unexpected positive cultures (UPCs) are very commonly found during shoulder arthroplasty when surgeons send intraoperative cultures to rule out periprosthetic joint infection (PJI) without clinical or radiographic signs of infection. Cutibacterium acnes is thought to be the most common bacteria cultured in this setting; however, the implications of an unexpected positive result are neither well defined nor agreed upon within the literature. The current review evaluates the incidence of UPCs and C acnes in reverse total arthroplasty; the clinical significance, if any, of these cultures; and various prognostic factors that may affect UPC incidence or recovery following PJI. METHODS: A systematic review was performed with PRISMA guidelines using PubMed, CINAHL, and Scopus databases. Inclusion criteria included studies published from January 1, 2000, to May 20, 2021, that specifically reported on UPCs, native or revision shoulder surgery, and any study that directly addressed one of our 6 proposed clinical questions. Two independent investigators initially screened 267 articles for further evaluation. Data on study design, UPC rate/speciation, UPC risk factors, and UPC outcomes were analyzed and described. RESULTS: A total of 22 studies met the inclusion criteria for this study. There was a pooled rate of 27.5% (653/2373) deep UPC specimen positivity, and C acnes represented 76.4% (499/653) of these positive specimens. Inanimate specimen positivity was reported at a pooled rate of 20.1% (29/144) across 3 studies. Male patients were more likely to have a UPC; however, the significance of prior surgery, surgical approach, and type of surgery conflicted across multiple articles. Patient-reported outcomes and reoperation rates did not differ between positive-UPC and negative-UPC patients. The utilization of antibiotics and treatment regimen varied across studies; however, the reinfection rates following surgery did not statistically differ based on the inclusion of antibiotics. CONCLUSION: UPCs are a frequent finding during shoulder surgery and C acnes represents the highest percentage of cultured bacteria. Various preoperative risk factors, surgical techniques, and postoperative treatment regimens did not significantly affect the incidence of UPCs as well as the clinical outcomes for UPC vs. non-UPC patients. A standardized protocol for treatment and follow-up would decrease physician uncertainty when faced with a UPC from shoulder surgery. Given the results of this review, shoulder surgeons can consider not drastically altering the postoperative clinical course in the setting of UPC with no other evidence of PJI.

Culturing explants for Cutibacterium at revision shoulder arthroplasty: an analysis of explant and tissue samples at corresponding anatomic sites.

BACKGROUND: Culturing of deep tissues obtained at revision arthroplasty for Cutibacterium is a key component of diagnosing a periprosthetic infection. The value of culturing explanted components has not been well described. This study sought to answer the following questions: (1) How does the culture positivity of explant cultures compare with that of deep tissue cultures? (2) How often are explant cultures positive when tissue cultures are not, and vice versa? (3) How does the bacterial density in explant cultures compare with that in tissue cultures? METHODS: A total of 106 anatomic arthroplasties revised over a 7-year period were included. Explant (humeral head, humeral stem, and glenoid) and tissue (collar membrane, humeral canal tissue, and periglenoid tissue) specimens were sent for semiquantitative Cutibacterium culture. We compared culture positivity and bacterial density when cultures of an explant and tissue adjacent to the implant were both available. RESULTS: Explants had positive cultures at a higher rate than adjacent tissue specimens for most anatomic sites. Of the shoulders that had Cutibacterium growth, a higher proportion of explants were culture positive when tissue samples were negative (23%-43%) than vice versa (0%-21%). The Cutibacterium density was higher in explants than in tissues. Considering only the results of tissue samples, 16% of the shoulders met our threshold for infection treatment (≥2 positive cultures); however, with the inclusion of the results for explant cultures, additional 14% of cases-a total of 30%-met the criteria for infection treatment. CONCLUSIONS: In this group of patients, culturing explants in addition to tissue cultures increased the sensitivity for detecting Cutibacterium in revision shoulder arthroplasty.

New Approaches to the Diagnosis and Management of Periprosthetic Joint Infection of the Shoulder.

Periprosthetic joint infection (PJI) of the shoulder is a potentially devastating complication following shoulder arthroplasty. It is important to review the workup of PJI in the shoulder, including recently developed diagnostic criteria for shoulder PJI, along with detailed examination of the most common causative organism, Cutibacterium acnes. Treatment strategies for PJI of the shoulder include antibiotic therapy, surgical options, and what to do with unexpected positive cultures in revision arthroplasty. Surgeons should be familiar with bony and soft-tissue reconstructive options following explantation of an infected shoulder prosthesis.

What do positive and negative Cutibacterium culture results in periprosthetic shoulder infection mean? A multi-institutional control study.

BACKGROUND: Deep tissue culture specimens obtained at the time of revision shoulder arthroplasty are commonly positive for Cutibacterium. Clinical interpretation of positive cultures can be difficult. This was a multi-institutional study evaluating the accuracy of cultures for Cutibacterium using positive control (PC) and negative control (NC) samples. The relationship between time to culture positivity and strength of culture positivity was also studied. METHODS: Eleven different institutions were each sent 12 blinded samples (10 PC and 2 NC samples). The 10 PC samples included 2 sets of 5 different dilutions of a Cutibacterium isolate from a failed total shoulder arthroplasty with a probable periprosthetic infection. At each institution, the samples were handled as if they were received from the operating room. Specimen growth, time to culture positivity, and strength of culture positivity (based on semiquantitative assessment) were reported. RESULTS: A total of 110 PC samples and 22 NC samples were tested. One hundred percent of specimens at the 4 highest dilutions were positive for Cutibacterium. At the lowest dilution, 91% of samples showed positive findings. Cutibacterium grew in 14% of NC samples. Cutibacterium grew in PC samples at an average of 4.0 ± 1.3 days, and all of these samples showed growth within 7 days. The time to positivity was significantly shorter (P < .001) and the strength of positivity was significantly higher (P < .001) in true-positive cultures compared with false-positive cultures. CONCLUSIONS: This multi-institutional study suggests that different institutions may report highly consistent rates of culture positivity for revision shoulder arthroplasty samples with higher bacterial loads. In contrast, with lower bacterial loads, the results are somewhat less consistent. Clinicians should consider using a shorter time to positivity and a higher strength of positivity as adjuncts in determining whether a tissue culture sample is a true positive.

Incidence of Cutibacterium acnes in open shoulder surgery.

In recent years, Cutibacterium acnes (C. acnes) has been reported to affect postoperative outcomes. The purpose of this study was to examine the detection rate and clinical features of C. acnes infection after open shoulder surgery. Fifty-nine patients (33 males and 26 females; mean age, 69.1 years) were included. Samples were collected from a skin swab at the incision site prior to skin preparation. Further samples were collected from synovial swabs at the glenohumeral joint immediately after incision and before incision closure. Samples with C. acnes-positive skin swab cultures were defined as Group A, and those with negative cultures were defined as Group N. Age, sex, presence of diabetes mellitus, operation time, presence of deep infection after surgery, and rate of positive synovial swab cultures were compared between groups. There were 27 patients in Group A (mean age 69.1±13.3 [SD], 21 males and 6 females) and 32 patients in Group N (mean age 69.1±11.0 [SD], 12 males and 20 females). No significant difference in the presence of diabetes mellitus and operation time were found between groups. From the glenohumeral joint immediately after incision, C. acnes was detected in 22.2% and 0% of patients in Group A and Group N, respectively. For the glenohumeral joint before incision closure, C. acnes was detected in 22.2% and 0% of patients in Group A and Group N, respectively, demonstrating a significantly higher rate in Group A. Our findings suggest that the route of infection following open shoulder surgery is via contamination.

Management of an outbreak of invasive Kingella kingae skeletal infections in a day care center.

BACKGROUND: Kingella kingae (Kk) is frequently responsible for invasive skeletal infections in children aged 3-36months. However, few outbreaks of invasive Kk infections in day care centers have been reported. The objective of the present study was to describe (a) the clinical and laboratory data recorded during an outbreak of invasive Kk skeletal infections, and (b) the management of the outbreak. METHOD: Four children from the same day care center were included in the study May and June 2019. We retrospectively analyzed the children's clinical presentation and their radiological and laboratory data. We also identified all the disease control measures taken in the day care center. RESULTS: We observed cases of septic arthritis of the wrist (case #1), shoulder arthritis (case #2), knee arthritis (case #3) ans cervical spondylodiscitis (case #4). All cases presented with an oropharyngeal infection and concomitant fever prior to diagnosis of the skeletal infection. All cases were misdiagnosed at the initial presentation. The mean (range) age at diagnosis was 10.75months (9-12). The three patients with arthritis received surgical treatment. All patients received intravenous and then oral antibiotics. In cases 1 and 2, Kk was detected using real-time PCR and a ST25-rtxA1 clone was identified. The outcome was good in all four cases. Four other children in the day care center presented with scabies during this period and were treated with systemic ivermectin. The Regional Health Agency was informed, and all the parents of children attending the day care center received an information letter. The day care center was cleaned extensively. CONCLUSION: Our results highlight the variety of features of invasive skeletal Kk infections in children and (given the high risk of transmission in day care centers) the importance of diagnosing cases as soon as possible.

Late prosthetic shoulder joint infection due to Actinomyces neuii in an adult man.

A 72-year-old man with a history of right reverse shoulder arthroplasty presented with a 1-month history of erythema, pain and drainage from the right shoulder. Arthrocentesis was performed and synovial fluid gram stain revealed gram-positive rods. Clinical diagnosis of prosthetic shoulder joint infection was made. Orthopaedic surgeons performed irrigation and debridement with resection of the right shoulder prothesis and implantation of an antimicrobial spacer. Operative cultures grew Actinomyces neuii The patient was treated with 6 weeks of ceftriaxone with improvement in both clinical symptoms and laboratory values. Actinomyces species remain a rare cause of late prosthetic joint infection (PJI) due to their slow growing and indolent course. While generalised actinomycosis is often treated with 6-12 months of antibiotics, the treatment course of Actinomyces PJI is not well characterised, with some sources suggesting a minimum of 6 weeks of antimicrobial therapy.

Pathogenic genetic variations of C. acnes are associated with clinically relevant orthopedic shoulder infections.

Many surgeons continue to face the clinical dilemma of interpreting a positive aspiration or unexpected positive Cutibacterium acnes (C. acnes) culture. There are factors that complicate the interpretation of positive cultures including variations in both frequency of false positive cultures and virulence properties. As indices of virulence, hemolytic strains, from previously confirmed clinically infected shoulders, were compared with non-hemolytic isolates determined to be contaminants, by RNA-sequencing (RNA-Seq). Six C. acnes isolates from patients who underwent revision total shoulder arthroplasty (TSA) were identified based on previously described infection criteria. Three C. acnes isolates from each group underwent RNA-Seq. Differential gene expression analysis, principal component analysis (PCA), and heatmap analysis were used to determine the gene variation and patterning between the definite infection and probable contaminant isolates. Differential gene expression analysis identified genes that were differentially expressed between the isolates classified as definite infection and isolates classified as probable contaminants. PCA using a 500 gene subset of identified genes was able to find combinations of these genes that separated out the definite infection and probable contaminants isolates. The heatmap demonstrated similar gene expression in the three Definite Infections isolates, and significantly different expression when compared with the probable contaminant isolates. Clinical significance: C. acnes revision TSA isolates classified as definite infection and probable contaminant demonstrated a similar gene expression pattern to each respective group and different gene expression pattern when compared between groups. These findings indicate distinct differences in C. acnes strains associated with clinically relevant orthopedic TSA infections.