Antimicrobial susceptibility of Propionibacterium acnes isolates from shoulder surgery

Propionibacterium acnes and Staphylococcus epidermidis olecranon bursitis/osteomyelitis: a case involving surgical and antibiotic treatment

This report describes a 63-year-old generally healthy male with septic olecranon bursitis caused by Propionibacterium acnes The patient sustained a small laceration after striking the posterior aspect of his left elbow on a metal railing when he was at a public swimming pool. We concluded that P. acnes was not initially detected because cultures were only kept for 5 days. Consequently, initial antibiotic treatment failed. P. acnes and Staphylococcus epidermidis grew in a subsequent tissue culture. The infection did not respond to intravenous vancomycin although soft-tissue debridements were done. This likely reflected the presence of olecranon osteomyelitis (seen on MRI scans) in addition to inadequate treatment with this antibiotic in the setting of a polymicrobial infection. Eventually, the infection was eradicated with multiple soft-tissue debridements in addition to the continuation of vancomycin with daily intravenous piperacillin/tazobactam that was added for the final 4 weeks of antibiotic treatment.

Survey of shoulder arthroplasty surgeons' methods for infection avoidance of Propionibacterium

Introduction

Propionibacterium acnes infection after shoulder arthroplasty remains a source of morbidity. Determining practices amongst shoulder surgeons is the first step in developing infection-prevention best-practices.

Methods

A survey was sent to a shoulder fellowship alumni group to determine their arthroplasty infection prevention methods.

Results

74% completed the survey. Cefazolin (90%), vancomycin (50%) and clindamycin (18%) were the most commonly used antibiotics, 61% utilized more than one antibiotic. Most (76%) reported using an experience-based protocol learned during residency/fellowship.

Discussion and conclusion

There are no clear standards for prevention of Propionibacterium acnes infections in shoulder arthroplasty. There is a general non-scientific approach to the prevention of shoulder arthroplasty infection.

In vitro susceptibility of Propionibacterium acnes to simulated intrawound vancomycin concentrations

Background

There is convincing evidence supporting the prophylactic use of intrawound vancomycin powder in spinal fusion surgery and mounting evidence in the arthroplasty literature suggesting that it can reduce surgical site infections. As a result, a number of shoulder arthroplasty surgeons have adopted this practice, despite a paucity of evidence and the presence of a pathogen that is, for the most part, unique to this area of the body—Propionibacterium acnes. The purpose of this study was to evaluate the efficacy of vancomycin against planktonic P. acnes in vitro, using time-dependent concentrations one would expect in vivo after intra-articular application.

Methods

Intrawound vancomycin concentrations were interpolated and extrapolated from existing in vivo data. Planktonic P. acnes was then subjected to a time-kill analysis during 96 hours. At each time point, the inoculum was centrifuged into pellet form and then reconstituted for serial drop counts onto blood agar plates. After anaerobic incubation, colony-forming units were counted, and log₁₀ colony-forming units per milliliter were determined.

Results

Early time points grew to confluence, and thus colony-forming units per milliliter were not calculated. However, at 12 hours of vancomycin treatment, distinct colonies were appreciated. Notably, there was a 3 × log₁₀ reduction in colony-forming units per milliliter between 12 and 48 hours, denoting bactericidal activity. In addition, P. acnes was completely eradicated after 3 days of treatment.

Conclusion

When administered in a fashion meant to simulate time-dependent in vivo intrawound concentrations, vancomycin exhibited bactericidal activity against P. acnes. This may lend credence to the prophylactic use of vancomycin in shoulder surgery.

Low-grade infections in nonarthroplasty shoulder surgery

BACKGROUND

Recent studies have identified the diagnostic challenge of low-grade infections after shoulder arthroplasty surgery. Infections after nonarthroplasty procedures have not been reported. This study assessed patient-related risk factors, outcomes, and clinical presentation of low-grade infection after open and arthroscopic nonarthroplasty shoulder surgery.

METHODS

The cases of 35 patients presenting with suspected low-grade infection were reviewed. Biopsy specimens taken at revision surgery were cultured in the sterile environment of a class II laminar flow cabinet and incubated for a minimum of 14 days at a specialist orthopedic microbiology laboratory. Patient-related factors (age, occupation, injection), index surgery, and infection characteristics (onset of symptoms, duration to diagnosis, treatment) were analyzed.

RESULTS

Positive cultures were identified in 21 cases (60.0%), of which 15 were male patients (71%). Of all patients with low-grade infection, 47.6% were male patients between 16 and 35 years of age. Propionibacterium acnes and coagulase-negative staphylococcus were the most common organisms isolated (81.1% [n = 17] and 23.8% [n = 5], respectively). Of 14 negative culture cases, 9 were treated with early empirical antibiotics (64.3%); 7 patients reported symptomatic improvement (77.8%). Of 5 patients treated with late empirical antibiotics, 4 stated improvement. Patients presented with symptoms akin to resistant postoperative frozen shoulder (persistent pain and stiffness, unresponsive to usual treatments).

CONCLUSION

Young male patients are at greatest risk for low-grade infections after arthroscopic and open nonarthroplasty shoulder surgery. P. acnes was the most prevalent organism. Patients presented with classic postoperative frozen shoulder symptoms, resistant to usual treatments. Interestingly, 78.6% of patients with negative cultures responded positively to empirical treatment.

Host Inflammatory Response During Periprosthetic Infection Is Joint Specific

BACKGROUND

Propionibacterium acnes (P. acnes) has become increasingly recognized as a cause of periprosthetic joint infection (PJI).

QUESTIONS/PURPOSES

It is not currently known if the clinical presentation of P. acnes varies depending on the joint being infected.

METHODS

We retrospectively reviewed patients infected with P. acnes after total hip, knee, and shoulder arthroplasty from two institutions. Patients were classified as having a PJI based on the Musculoskeletal Infection Society criteria and were excluded if they had a polymicrobial culture. Patient demographics, preoperative laboratory values, and microbiology data were analyzed.

RESULTS

Eighteen knees, 12 hips, and 35 shoulders with a P. acnes PJI were identified. Median ESR was significantly higher in the knee (38.0 mm/h, IQR 18.0-58.0) and hip (33.5 mm/h, IQR 15.3-60.0) groups compared to the shoulder group (11.0 mm/h, IQR 4.5-30.5). C-reactive protein levels were higher in the knee (2.0 mg/dl, IQR 1.3-8.9) and hip (2.4 mg/dl, IQR 0.8-4.9) groups compared to the shoulder group (0.7 mg/dl, IQR 0.6-1.5). Median synovial fluid WBC was significantly higher in the knee group than shoulder group (19,950 cells/mm³, IQR 482-60,063 vs 750 cells/mm³, IQR 0-2825, respectively). Peripheral blood WBC levels were similar between groups, as was mean time of P. acnes growth in culture. Clindamycin resistance was present in all groups.

CONCLUSION

The manner in which a patient with P. acnes PJI presents is joint specific. Inflammatory markers were significantly higher in the knee and hip groups compared to the hip and shoulder groups, and long hold anaerobic cultures up to 14 days are necessary to accurately identify this organism.

High incidence of periprosthetic joint infection with propionibacterium acnes after the use of a stemless shoulder prosthesis with metaphyseal screw fixation - a retrospective cohort study of 241 patients

BACKGROUND

A stemless shoulder prosthesis with humeral metaphyseal screw fixation was introduced in order to save bone-stock and to facilitate reconstruction of biomechanics (Eclipse®). The aim of this study was to analyze whether the risk of infection is different with this implant compared to conventional shoulder prosthesis.

METHODS

Two hundred and forty-one patients (54.8% females) were operated with a shoulder arthroplasty and followed for median 2.0 (0.1-5.7) years. One hundred and two (42.3%) had received an Eclipse® prosthesis, the remaining patients were operated with other implants. There was an overrepresentation of males in the Eclipse® group (63.7% males) when compared with the control group (31.7% males).

RESULTS

In the Eclipse® group 10 (9.8%) patients developed a periprosthetic joint infection, as opposed to 1 (0.7%) in the control group. The most common bacteria was Propionibacterium acnes. Unadjusted infection-free survival after 4 years was 88.8% (CI 82.5-95.7) for Eclipse® patients and 95.7% (CI 87.7-100.0) for controls (p = 0.002). After adjustment for age, gender, diagnosis, and type of shoulder prosthesis (total or hemi), the risk ratio for revision due to infection was 4.3 (CI 0.5-39.1) for patients with the Eclipse® prosthesis.

CONCLUSIONS

Deep infections seem to be more common after the use of the metaphyseally fixed Eclipse® prosthesis than after conventional shoulder implants, but a predominance of male gender and younger age in the Eclipse group may have biased our findings. Future studies on larger cohorts and in vitro investigations on bacterial adherence and biofilm formation are needed.

TRIAL REGISTRATION

The study was conducted in accordance with the Helsinki Declaration. The local ethics board (Regionala Etikprövningsnämnden Stockholm) approved the study (Approval number 2015/1590-31, date of issue 2015-10-14). Retrospectively registered.

Clinical impact of positive Propionibacterium acnes cultures in orthopedic surgery

BACKGROUND

The clinical significance of a positive culture to Propionibacterium acnes in orthopedic specimens remains unclear, whether about its role as a contaminant or a pathogen, or its impact as a coinfectant. Therefore, we performed a retrospective study to provide a more accurate description of the clinical impact of P. acnes in an orthopedic population aiming to determine: 1) if there is a clinical difference between P. acnes infection and contamination? 2) If there is a clinical difference between P. acnes monoinfection, and coinfection.

HYPOTHESIS

There is a clinical difference between P. acnes infection and contamination.

MATERIALS AND METHODS

Patients were selected over a five-year period, and those with a minimum of one positive culture for P. acnes, from any intraoperative orthopedic tissue sample, were included in the study. P. acnes infection was defined as the isolation of P. acnes from≥2 specimens, or in only one specimen, in the presence of typical perioperative findings and/or local signs of infection.

RESULTS

A total of 68 patients had a positive P. acnes culture, 35 of which were considered to be infected. The infections affected mostly males (29/35-83%), occurred mostly in shoulders (22/35-63%), and at a site already containing an orthopedic implant (32/35-91%). Local inflammatory signs were present in half of the cases when an infection was diagnosed. Coinfection with other pathogens was present in 31% of patients (11/35). When comparing patients coinfected with P. acnes, and those who were monoinfected, the latter presented less often with local inflammatory signs. Recurrence rate was 24% (8/35) and the only risk factor for recurrence was the presence of a monoinfection.

DISCUSSION

This study confirms the pathogenicity of P. acnes in an orthopedic population, as it is present in multiple samples in the same patient, and because it is present in cultures from cases with clinical recurrence. Our study showed that monoinfections differ from coinfections mainly by their higher risk of recurrence.

LEVEL OF EVIDENCE

Level IV retrospective case series.

Infections following arthroscopic rotator cuff repair: incidence, risk factors, and prophylaxis

PURPOSE

The primary aim of the present study was to determine the incidence of infections following arthroscopic rotator cuff repair in a single department over a 10-year period. Secondary goals included the evaluation of potential risk factors for infections and to investigate the efficacy of perioperative antibiotic prophylaxis in the reduction of infectious complications.

METHODS

A retrospective evaluation of 3294 all-arthroscopic rotator cuff repairs performed between 2004 and 2014 at a single institution was conducted to determine the rate of infection in all-arthroscopic rotator cuff repairs. Detailed data including demographics, co-morbidities, initial surgical procedure, time from index surgery to infection, clinical presentation, isolated pathogens, and subsequent treatment were recorded of patients with infections. Univariate logistic regression was performed, and a multivariate model was developed to identify variables that were predictive of infections following arthroscopic rotator cuff repair.

RESULTS

The rate of infection was 8.5/1000 in whom rotator cuff repairs were performed (95 % CI 0.58-1.23 %) during the study period. The most commonly identified pathogen was Staphylococcus epidermidis (n = 11, 39.3 %), followed by Propionibacterium acnes (n = 8, 28.6 %) and Staphylococcus aureus (n = 2, 7.1 %). Patients presented at our institution with signs of infection an average of 28.9 ± 14.7 days after the index surgery. The leading symptom that was present in all patients was diffuse or localized shoulder pain, followed by local signs of infection in 19 (67.9 %), secretion in 14 (50 %), and fever in 9 (32.1 %) patients, respectively. Univariate and multivariate analyses identified the male gender, age over 60, and duration of surgery over 90 min as predictive factors for infection. Administration of perioperative antibiotic prophylaxis was an independent mitigating factor for postoperative infection and reduced the infection rate from 1.54 % (95 % CI 0.98-2.30 %) to 0.28 % (95 % CI 0.10-0.67 %).

CONCLUSIONS

The overall incidence of infection was 8.5/1000 arthroscopic rotator cuff repairs over a 10-year period. Gender, age, and length of surgery were identified as predictive factors for infection. The administration of perioperative antibiotic prophylaxis significantly reduced the overall risk of infection and is therefore recommended in all-arthroscopic rotator cuff repairs. However, current prophylactic treatment strategies were not equally efficient for all types of pathogens.

LEVEL OF EVIDENCE

Retrospective comparative study, Level III.

Propionibacterium acnes Susceptibility and Correlation with Hemolytic Phenotype

BACKGROUND

Many studies have noted an increase in the number of recognized cases of invasive infections due to Propionibacterium acnes, especially after shoulder replacement surgery. The increase in the number of recognized cases of P. acnes, a nonspore-forming, anaerobic, Gram-positive organism, appears due to both an increase in the number of shoulder operations being performed and more specimens being sent for anaerobic cultures. Nevertheless, the optimal surgical and antibiotic management of P. acnes remains controversial.

METHODS

We tested the susceptibility of 106 P. acnes strains from sterile body sites collected at the Erie County Medical Center between 2012 and 2015, using Etest gradient antibiotic strips.

RESULTS

P. acnes is very susceptible to the penicillins and the first-generation cephalosporins. We noted an association between hemolytic phenotype on Brucella Blood Agar and clindamycin resistance.

CONCLUSIONS

Antimicrobial susceptibility testing of P. acnes should no longer just be confined to the research laboratory but expanded and incorporated into routine microbiological evaluation of P. acnes. This would improve patient care as well as help clarify the relationship between hemolysis and clindamycin resistance.

Clinical Analysis of Propionibacterium acnes Infection After Total Knee Arthroplasty

BACKGROUND

Propionibacterium acnes is a common cause of upper extremity arthroplasty infection and usually presents in an indolent subacute fashion. It is not well described how total knee arthroplasty (TKA) patients infected with P acnes present.

METHODS

We retrospectively compared patients undergoing revision TKA for infection from P acnes and methicillin-sensitive Staphylococcal aureus (MSSA) in our institutional infection database. Patients were classified as having a periprosthetic joint infection based on the Musculoskeletal Infection Society criteria and were excluded if they had a polymicrobial culture. Patient demographics, preoperative laboratory values, microbiology data, and synovial fluid white blood cell (WBC) counts were analyzed.

RESULTS

Sixteen patients with a P acnes and 30 with an MSSA TKA periprosthetic joint infection were identified. Median erythrocyte sedimentation rate was significantly higher in the MSSA group compared to the P acnes group (56.0 mm/h; interquartile range [IQR], 44.3-72.9 vs 23.0 mm/h; IQR, 18.5-52.0; respectively, P = .03) as were C-reactive protein levels (5.9 mg/dL; IQR, 3.7-26.9 vs 2.0 mg/dL; IQR, 0.5-14.0; respectively, P = .04). WBC count, synovial fluid WBC, and percentage of synovial polymorphonuclear cells were similar between groups. Mean time to culture was 8.3 ± 2.0 days in the P acnes group and 1.8 ± 0.8 days in the MSSA group.

CONCLUSION

P acnes TKA infections are associated with more acute inflammatory symptoms than typically appreciated, and long hold anaerobic cultures up to 14 days are necessary to accurately identify this organism as the causative agent of TKA periprosthetic infection.

Acute infection with Propionibacterium acnes after a Latarjet coracoid transfer procedure: a case report

Coracoid transfer procedures are highly effective at improving glenohumeral stability in patients with recurrent shoulder instability; complication rates from this procedure are generally low. We present the first case in the literature of a Propionibacterium acnes (P. acnes) infection following a coracoid transfer. The case stresses the importance of proper antibiotic prophylaxis for patients undergoing Latarjet procedures, as well as the workup for a painful postoperative shoulder, and the need to maintain cultures from the shoulder for up to 21 days to isolate P. acnes.

Cardiovascular Implantable Electronic Device Infections due to Propionibacterium Species

INTRODUCTION

Propionibacterium species are part of the normal skin flora and often considered contaminants when identified in cultures. However, they can cause life-threatening infections, including prosthetic cardiovascular device infections. Clinical presentation and management of cardiovascular implantable electronic device (CIED) infection due to Propionibacterium species has not been well described.

METHODS

Retrospective review of all cases of CIED infection due to Propionibacterium species admitted to Mayo Clinic between January 1, 1990 and December 31, 2014. Patient charts were reviewed for clinical, microbiological, and imaging data. Descriptive analysis was performed.

RESULTS

We identified 14 patients with CIED infection due to Propionibacterium species, accounting for 2.3% of all CIED infections. Patients were predominantly male (n = 12, 86%). The median age at admission was 58.5 years (range 22-83). Twelve patients had implantable cardioverter defibrillators (ICDs) and two had permanent pacemaker systems. Twelve patients had generator pocket infection (86%). Two patients met clinical criteria for CIED-related infective endocarditis. Median time between last device manipulation and infection was 9 months (range 1-98). All patients were treated with complete device removal and antibiotic therapy. Six-month follow-up data were available for 10 patients (71%), with no relapses documented.

CONCLUSION

CIED infections due to Propionibacterium species accounted for 2.3% of all device infections over a 25-year period. The most common infectious syndrome was generator pocket infection with delayed onset. There was an unanticipated predominance of ICDs in this cohort. Cure was achieved in all cases with complete device removal and antibiotic therapy.

Characteristics and Treatment Outcomes of Propionibacterium acnes Prosthetic Shoulder Infections in Adults

P. acnes shoulder prosthetic joint infections were predominantly characterized by pain and functional loss. Inflammatory marker elevation occurred in just under 50% of cases. Isolates were broadly susceptible to guideline concordant antimicrobials. Antibiotic-only and combined antibiotic-surgical intervention outcomes were similar.

Background. Prosthetic joint infections (PJIs) significantly complicate joint arthroplasties. Propionibacterium acnes is an increasingly recognized PJI pathogen, yet limited clinical and therapeutic data exist. We sought to examine characteristics of P. acnes shoulder PJIs and compare surgical and nonsurgical management outcomes.

Methods. A retrospective analysis of P. acnes shoulder PJIs was conducted at an academic center in Baltimore, Maryland from 2000 to 2013.

Results. Of 24 cases of P. acnes shoulder PJIs, 92% were diagnosed after extended culture implementation; 42% in the delayed and 46% in the late postsurgical period. Joint pain and diminished function were the predominant presenting clinical signs. Erythrocyte sedimentation rate and C-reactive protein elevations occurred in 47% and 44%, respectively. All tested isolates were susceptible to β-lactams, moxifloxacin, vancomycin, and rifampin. Clindamycin resistance was identified in 6%. Of the antibiotic-only treated cases, 67% had a favorable clinical outcome compared with 71% (P = 1.0) of cases with a combined antibiotic-surgical approach. Favorable outcome with and without rifampin therapy was 73% and 60% (P = .61), respectively.

Conclusions. Propionibacterium acnes PJI diagnoses increased with extended culture. Inflammatory markers were elevated in a minority of cases. Isolates maintained broad antimicrobial susceptibility. Compared to combined antibiotic-surgical approaches, antibiotic-only approaches were similarly successful in selected cases.

Propionibacterium acnes infection after shoulder surgery

Propionibacterium acnes has been implicated as a cause of infection following shoulder surgery, may occur up to 2 years after the index operation and has been shown to be responsible for up to 56% of shoulder infections after orthopedic implant. Male patients within the population undergoing shoulder surgery are particularly at risk, especially if their shoulder surgery involved prosthesis or was posttraumatic. P. acnes infection can be difficult to diagnose clinically and laboratory techniques require prolonged and specialized cultures. Usual inflammatory markers are not raised in infection with this low virulence organism. Delayed diagnosis with P. acnes infection can result in significant morbidity prior to prosthesis failure. Early diagnosis of P. acnes infection and appropriate treatment can improve clinical outcomes. It is important to be aware of P. acnes infection in shoulder surgery, to evaluate risk factors, to recognize the signs of P. acnes infection, and to promptly initiate treatment. The signs and symptoms of P. acnes infection are described and discussed. Data were collected from PubMed™, Web of Science, and the NICE Evidence Healthcare Databases - AMED (Ovid), BNI (Ovid), CINAHL (EBSCO), Embase (Ovid), HMIC: DH-Data and Kings Fund (Ovid), Medline (Ovid), and PsycINFO (Ovid). The search terms used were "P. acnes," "infection," "shoulder," and "surgery." In this review, we summarize the current understanding of the prevention and management of P. acnes infection following shoulder surgery.

Principles of Antibiotic Prophylaxis in Total Joint Arthroplasty: Current Concepts

Infection is a rare, serious complication following total joint arthroplasty and constitutes a considerable emotional and financial burden for patients, surgeons, and healthcare systems. Prevention of surgical site and periprosthetic joint infections is crucial. This requires knowledge of the microorganisms that commonly cause these infections, including Staphylococcus species. Selection of the appropriate antibiotic regimen to treat infection remains controversial, but cefazolin and cefuroxime are the most commonly recommended antibiotics for prophylaxis. Appropriate timing of administration before surgery, with redosing performed as needed, can help to ensure optimal antibiotic concentration during surgery. Given the increasing evidence that S aureus colonization is a risk factor for periprosthetic joint infection, an exploration of the potential benefits of preoperative S aureus carrier screening and decolonization protocols is warranted. The use of antibiotic-loaded bone cement in primary total joint arthroplasty and antibiotic powder at wound closure are other controversial topics that require additional research.

Propionibacterium can be isolated from deep cultures obtained at primary arthroplasty despite intravenous antimicrobial prophylaxis

BACKGROUND

Propionibacterium organisms are commonly recovered from deep cultures obtained at the time of revision arthroplasty. This study sought to determine whether deep cultures obtained at the time of primary arthroplasty can be substantially positive for Propionibacterium despite thorough skin preparation and preoperative intravenous antibiotic prophylaxis.

METHODS

After timely administration of preoperative antibiotics chosen specifically for their activity against Propionibacterium and after double skin preparation, specimens from the dermis, fascia, capsule, synovium, and glenoid tissue were sterilely harvested from 10 male patients undergoing primary shoulder arthroplasty and were submitted for culture for Propionibacterium.

RESULTS

Of the 50 specimens, 7 were positive for Propionibacterium: 3 in each of 2 patients and 1 in 1 patient. The specimen sources having positive anaerobic cultures were the dermis (1 of 10), fascia (2 of 10), synovium (1 of 10), and glenoid tissue (3 of 10). None of these patients had evidence of infection at the time of the arthroplasty.

DISCUSSION AND CONCLUSION

Preoperative antibiotics and skin preparation do not always eliminate Propionibacterium from the surgical field of primary shoulder arthroplasty. The presence of these bacteria in the arthroplasty wound may pose a risk of delayed shoulder arthroplasty failure from the subtle type of periprosthetic infection typically associated with Propionibacterium.

Presence of Propionibacterium acnes in primary shoulder arthroscopy: results of aspiration and tissue cultures

BACKGROUND

Infection after shoulder surgery has a serious impact on patient outcome and costs associated with care. Propionibacterium acnes infection may be insidious and manifest years after index surgery with resultant joint arthropathy or prosthesis infection. Our goal was to evaluate the presence of P. acnes in a group of patients undergoing primary arthroscopic shoulder surgery to better understand this organism.

METHODS

Samples were collected from 57 patients undergoing first-time shoulder arthroscopy. Demographic data and medical comorbidities were collected. A control, 2 skin swabs, synovial fluid, and 3 tissue samples were obtained. All samples were placed on aerobic plates, on anaerobic plates, and in thioglycolate broth and held for 28 days.

RESULTS

Fifty-seven patients underwent arthroscopic shoulder surgery. The mean age was 51 years. Eighty-one samples (21.8%) were positive for P. acnes when cultures were held 14 days; 32 subjects (56%) had at least 1 culture that grew P. acnes. Positive skin cultures for P. acnes increased from 15.8% before incision to 40.4% at closure. This was even more pronounced in men as positive skin cultures increased from 31.3% before incision to 63.0% at closure. Thirteen patients (22.8%) had more than 3 cultures positive. None of the patients in this study have had signs or symptoms to suggest clinical P. acnes infection.

CONCLUSIONS

Of all subjects studied, 56% had at least 1 positive culture; 21% (of all 371 culture specimens obtained) grew P. acnes. We suspect that it is a consequence of true positive cultures from imperfect skin preparation and dermal contamination.

Potential biological applications of bio-based anacardic acids and their derivatives

Cashew nut shells (CNS), which are agro wastes from cashew nut processing factories, have proven to be among the most versatile bio-based renewable materials in the search for functional materials and chemicals from renewable resources. CNS are produced in the cashew nut processing process as waste, but they contain cashew nut shell liquid (CNSL) up to about 30-35 wt. % of the nut shell weight depending on the method of extraction. CNSL is a mixture of anacardic acid, cardanol, cardol, and methyl cardol, and the structures of these phenols offer opportunities for the development of diverse products. For anacardic acid, the combination of phenolic, carboxylic, and a 15-carbon alkyl side chain functional group makes it attractive in biological applications or as a synthon for the synthesis of a multitude of bioactive compounds. Anacardic acid, which is about 65% of a CNSL mixture, can be extracted from the agro waste. This shows that CNS waste can be used to extract useful chemicals and thus provide alternative green sources of chemicals, apart from relying only on the otherwise declining petroleum based sources. This paper reviews the potential of anacardic acids and their semi-synthetic derivatives for antibacterial, antitumor, and antioxidant activities. The review focuses on natural anacardic acids from CNS and other plants and their semi-synthetic derivatives as possible lead compounds in medicine. In addition, the use of anacardic acid as a starting material for the synthesis of various biologically active compounds and complexes is reported.

Conventional diagnostic challenges in periprosthetic joint infection

Periprosthetic joint infection remains a clinical challenge with no benchmark for diagnosis. The diagnosis is based on many different clinical variables that may be difficult to interpret, especially in the setting of chronic systemic disease. Synovial fluid aspiration, diagnostic imaging, traditional culture, peripheral serum inflammatory markers, and intraoperative frozen sections each have their limitations but continue to be the mainstay for diagnosis of periprosthetic joint infection. As molecular- and biomarker-based technologies improve, the way we interpret and diagnose periprosthetic joint infection will ultimately change and may even improve diagnostic accuracy and turnaround time. Future research on this topic should be focused on improving diagnostic criteria for low-virulence organisms, improving interpretation of intraoperative frozen sections, and establishing improved synovial fluid and peripheral serum biomarker profiles for periprosthetic joint infection.

Management of Propionibacterium acnes infection after shoulder surgery

Propionibacterium acnes (P. acnes) is a gram-positive anaerobic bacillus commonly isolated from the flora of the face, chest, and axilla region. It has emerged as a major pathogen responsible for postoperative shoulder infections after both arthroscopy and arthroplasty procedures. Patients with P. acnes shoulder infection typically present with normal laboratory values (white blood cells (WBC), erythrocyte sedimentation rate (ESR), and C-reactive protein (CRP)) making diagnosis difficult. Several intraoperative tissue cultures should be obtained and cultured in both agar plate and broth in aerobic and anaerobic conditions for a minimum of 13 days to optimize the sensitivity and specificity to detect P. acnes. The utilization of intraoperative frozen sections to detect P. acnes infection is not reliable. Risk factors include male, cloudy synovial fluid, lucencies around the implant, and periprosthetic membrane formation. Managements include irrigation and debridement, single or two-staged revision, and intravenous antibiotics. Open biopsy prior to the final implantation (two-staged revision) may help detect persistent P. acnes infection. Penicillin and cephalosporins are effective against clinical P. acnes infection and biofilm in vitro. Combination antibiotic therapy with rifampin and daptomycin may further increase the clinical efficacy of treatment.

Propionibacterium acnes: from commensal to opportunistic biofilm-associated implant pathogen

Propionibacterium acnes is known primarily as a skin commensal. However, it can present as an opportunistic pathogen via bacterial seeding to cause invasive infections such as implant-associated infections. These infections have gained more attention due to improved diagnostic procedures, such as sonication of explanted foreign materials and prolonged cultivation time of up to 14 days for periprosthetic biopsy specimens, and improved molecular methods, such as broad-range 16S rRNA gene PCR. Implant-associated infections caused by P. acnes are most often described for shoulder prosthetic joint infections as well as cerebrovascular shunt infections, fibrosis of breast implants, and infections of cardiovascular devices. P. acnes causes disease through a number of virulence factors, such as biofilm formation. P. acnes is highly susceptible to a wide range of antibiotics, including beta-lactams, quinolones, clindamycin, and rifampin, although resistance to clindamycin is increasing. Treatment requires a combination of surgery and a prolonged antibiotic treatment regimen to successfully eliminate the remaining bacteria. Most authors suggest a course of 3 to 6 months of antibiotic treatment, including 2 to 6 weeks of intravenous treatment with a beta-lactam. While recently reported data showed a good efficacy of rifampin against P. acnes biofilms, prospective, randomized, controlled studies are needed to confirm evidence for combination treatment with rifampin, as has been performed for staphylococcal implant-associated infections.

Substantial cultures of Propionibacterium can be found in apparently aseptic shoulders revised three years or more after the index arthroplasty

BACKGROUND

Revisions of apparently "aseptic" shoulder arthroplasties are not infrequently culture positive for Propionibacterium, organisms that may be introduced at the time of the index surgery when the dermal sebaceous glands are transected. This report seeks to answer the question, Do surgeons performing revision shoulder arthroplasty years after the index procedure need to be concerned about the persistence of Propionibacterium?

METHODS

We reviewed the medical records of 148 revision arthroplasties performed between July 2008 and June 2013 to find those revisions performed at least 3 years after the index procedure and at which intraoperative cultures were strongly positive for Propionibacterium.

RESULTS

We identified 14 cases of revision surgery performed 8 ± 4 years after the original arthroplasty for which deep cultures were strongly positive for Propionibacterium. A total of 109 specimens were obtained, 84 of which were positive. All 14 patients were male.

CONCLUSION

Shoulder arthroplasties revised for the mechanical problems of loosening or stiffness can be substantially culture positive for Propionibacterium, even if the revision is performed many years after the index procedure. Therefore, even in shoulder arthroplasties revised for mechanical problems years after the index procedures, surgeons should consider submitting multiple deep specimens for specific Propionibacterium culture. In the presence of persistent Propionibacterium, surgeons should consider the need for directed surgical and medical treatment in their management of a failed arthroplasty.