Optimization of periprosthetic culture for diagnosis of Propionibacterium acnes prosthetic joint infection

Proceedings from the 2018 International Consensus Meeting on Orthopedic Infections: evaluation of periprosthetic shoulder infection

The Second International Consensus Meeting on Orthopedic Infections was held in Philadelphia, Pennsylvania, in July 2018. More than 800 experts from all 9 subspecialties of orthopedic surgery and allied fields of infectious disease, microbiology, and epidemiology were assembled to form the International Consensus Group. The shoulder workgroup reached consensus on 27 questions related to culture techniques, inflammatory markers, and diagnostic criteria used to evaluate patients for periprosthetic shoulder infection. This document contains the group's recommendations and rationale for each question related to evaluating periprosthetic shoulder infection.

The Journey of Cultures Taken During Revision Joint Arthroplasty: Preanalytical Phase

Background: Microbiological culture has been considered the standard for pathogen identification for decades. However, culture is a laborious, time consuming, imperfect and outdated process. This study aims to inform the orthopedic community of the steps and timing of routine culture processing. Methods: We prospectively tracked 103 cultures from 33 revision hip and knee arthroplasty patients between September 2017-February 2018. Times were recorded at intraoperative collection; time of pick up from OR, transportation time; arrival at the laboratory; culture processing and plating time; and time to final result reporting. Results: Of the 103 cultures, 45.6% were processed and incubated in less than two hours, and 54.4% greater than or equal to two hours. The mean time spent in the OR, during transport, and within the laboratory prior to incubation was 0:53, 0:06 and 1:12. The range of time that samples remained at each stage varied considerably in the OR (0:03-3:33), in transit(0:04-0:16), and in the lab prior to incubation(0:26-3:01). The proportion of the total time to incubation attributed to idle time samples spent in the OR after initial sampling was 40.0%. In contrast, transport to the laboratory represented 5.1% of the total time. Idle time in the laboratory represented the greatest share at 54.9%. Conclusion: There is significant variability in the time to transport, process and incubate culture samples. Almost half of the specimens were processed outside the 2-hour recommended window. Surgeons should be aware of idle time during processing and seek to optimize their institutional pathways to maximize culture yield.

The W.A.I.O.T. Definition of High-Grade and Low-Grade Peri-Prosthetic Joint Infection

The definition of peri-prosthetic joint infection (PJI) has a strong impact on the diagnostic pathway and on treatment decisions. In the last decade, at least five different definitions of peri-prosthetic joint infection (PJI) have been proposed, each one with intrinsic limitations. In order to move a step forward, the World Association against Infection in Orthopedics and Trauma (W.A.I.O.T.) has studied a possible alternative solution, based on three parameters: 1. the relative ability of each diagnostic test or procedure to Rule OUT and/or to Rule IN a PJI; 2. the clinical presentation; 3. the distinction between pre/intra-operative findings and post-operative confirmation. According to the WAIOT definition, any positive Rule IN test (a test with a specificity > 90%) scores +1, while a negative Rule OUT test (a test with a sensitivity > 90%) scores −1. When a minimum of two Rule IN and two Rule OUT tests are performed in a given patient, the balance between positive and negative tests, interpreted in the light of the clinical presentation and of the post-operative findings, allows to identify five different conditions: High-Grade PJI (score ≥ 1), Low-Grade PJI (≥0), Biofilm-related implant malfunction, Contamination and No infection (all scoring < 0). The proposed definition leaves the physician free to choose among different tests with similar sensitivity or specificity, on the basis of medical, logistical and economic considerations, while novel tests or diagnostic procedures can be implemented in the definition at any time, provided that they meet the required sensitivity and/or specificity thresholds. Key procedures to confirm or to exclude the diagnosis of PJI remain post-operative histological and microbiological analysis; in this regard, given the biofilm-related nature of PJI, microbiological investigations should be conducted with proper sampling, closed transport systems, antibiofilm processing of tissue samples and explanted biomaterials, and prolonged cultures. The proposed WAIOT definition is the result of an international, multidisciplinary effort. Next step will be a large scale, multicenter clinical validation trial.

Cutibacterium acnes in primary reverse shoulder arthroplasty: from skin to deep layers

BACKGROUND

The aim of this study was to determine the presence of Cutibacterium acnes (formerly Propionibacterium acnes) on the skin and in deep tissue in a real clinical scenario of primary reverse shoulder arthroplasty.

METHODS

This prospective study included 90 primary reverse shoulder arthroplasties, and 12 cultures were obtained from each patient. Each sample was homogenized and used to inoculate PolyVitex (bioMérieux, Marcy-l'Etoile, France) agar and Schaedler (bioMérieux) agar plates. The same procedure was also followed with a thioglycolate broth. Culture was considered positive for C acnes when 2 or more colonies were observed. Total DNA from C acnes isolates was extracted using the InstaGene Matrix (Bio-Rad Laboratories, Hercules, CA, USA) method. The phylotype was determined, and single-locus sequence typing was done on all isolates.

RESULTS

We obtained 1080 tissue cultures from the 90 patients included, and 62 of those tissue cultures (5.7%) were positive for C acnes. There were 22 C acnes-positive tissue cultures before prosthesis implantation and 40 after implantation. C acnes was isolated in 17 patients (18.8%). We sent 38 positive samples for blinded phylotyping, single-locus sequence typing, and multi-locus sequence typing type determination. Many of the clusters isolated belonged to phylotype IB and clonal complex (CC) 36 or phylotype II and CC53.

DISCUSSION

In the real scenario of patients undergoing primary reverse shoulder arthroplasty using antibiotic prophylaxis and standard preoperative skin preparation with chlorhexidine, C acnes was isolated in the deep layers of 18.8% of the patients. The C acnes K1 and K2 subtypes (belonging to phylotype II and CC53), reported to be commonly involved in prosthetic joint infection, were usually isolated.

Comparing Standard Versus Extended Culture Duration in Acute Hip and Knee Periprosthetic Joint Infection

INTRODUCTION

Periprosthetic joint infection (PJI) is a devastating complication of hip and knee arthroplasties. Surgical cultures are essential for the diagnosis and treatment of PJI. Yet, the ideal culture duration remains unclear. This study compares culture yield, organism profile, and treatment success between standard (5 days) and extended (14 days) cultures in acute hip and knee PJI.

METHODS

A retrospective review of medical records was completed between 2006 and 2015. All patients with an acute PJI meeting the modified International Consensus Meeting on PJI criteria of a primary hip or knee arthroplasty were included. All patients underwent irrigation and débridement with exchange of modular bearing surfaces for an acute postoperative or acute hematogenous infection. A standard growth cohort (before February 2012) was compared with an extended growth cohort (after February 2012) to determine if differences existed in culture yield and treatment success using the Delphi consensus criteria.

RESULTS

One hundred eighty-nine patients were analyzed, including 102 (54.0%) standard duration and 87 (46.0%) extended duration cohorts. Patient cohorts were closely matched, except more hip PJIs than knee PJIs were included in the standard cohort (69.6% versus 49.4%; P = 0.005). No differences between standard and extended cohorts were observed with regard to overall culture yield, monomicrobial growth, or polymicrobial growth. Propionibacterium acnes was identified more often in the extended cohort (5 versus 0 patients; P = 0.019). However, four of these patients had only one positive P acnes culture and grew additional organisms. Finally, no difference in treatment success between the standard and extended cohorts at the final follow-up was found (53% versus 52%; P = 0.282).

CONCLUSION

Extended culture duration in acute hip and knee PJIs did not change the rate of culture-negative PJI, identify more patients with polymicrobial PJI, or improve the success of surgical treatment. The only difference was a higher incidence of P acnes growth, but contaminants or indolent chronic PJI cannot be excluded. Although extended culture growth may be indicated in acute shoulder arthroplasty PJI, its utility in hip or knee arthroplasty may be limited. Higher-level studies will be needed to address this in the future.

Reduced Time to Positive Cutibacterium acnes Culture Utilizing a Novel Incubation Technique: A Retrospective Cohort Study

Introduction

Cutibacterium acnes (C. acnes) is a common pathogen in postoperative shoulder infections. The purpose of this study was to evaluate the time to positive cultures for C. acnes and compare our experience before and after implementation of a regulated anaerobic chamber system. We hypothesized that this would reduce the time to identify positive cultures.

Methods

This was a retrospective review of 34 patients with cultures obtained from the shoulder that were positive for C. acnes. The time until positive result was evaluated before and after implementation of a regulated anaerobic incubation chamber.

Results

Following implementation of the regulated anaerobic incubation chamber, the time until C. acnes culture growth significantly decreased from 6.5 days (range 3–10 days) to 4.9 days (range 2.75–10 days) (mean difference: 1.6 days, 95% confidence interval: 1.06–2.66 days; P = .002). True infections had a significantly shorter time to positive culture compared to contaminants (5.5 vs 6.8 days, respectively, P = .003). Increased number of positive culture specimens correlated with a shorter time to positivity (Spearman rank = −0.58, P = .007).

Conclusion

Improved anaerobic culture protocols and techniques may lead to greater accuracy and earlier diagnosis and initiation of treatment of postoperative shoulder infections.

A comparative study of intraoperative frozen section and alpha defensin lateral flow test in the diagnosis of periprosthetic joint infection

Background and purpose - For decision-making (aseptic vs. septic), surgeons rely on intraoperatively available tests when a periprosthetic joint infection (PJI) cannot be confirmed or excluded preoperatively. We compared and evaluated the intraoperative performances of the frozen section and the alpha defensin lateral flow test in the diagnosis of PJI. Patients and methods - In this prospective study, consecutive patients with indicated revision surgery after arthroplasty were included. Patients were classified as having PJI using the MusculoSkeletal Infection criteria. The presence of alpha defensin was determined using the lateral flow test intraoperatively. During revision surgery, tissue samples were harvested for frozen and permanent section. Analysis of diagnostic accuracy was based on receiver-operating characteristics. Results - 101 patients (53 hips, 48 knees) were eligible for inclusion. Postoperatively, 29/101 patients were diagnosed with PJI, of which 8/29 cases were definitely classified as septic preoperatively. Of the remainder 21 septic cases, the intraoperative alpha defensin test and frozen section were positive in 13 and 17 patients, respectively. Sensitivities of the alpha defensin test and frozen section were 69% and 86%, respectively. The area under the curves of both tests showed a statistically significant difference (p = 0.006). Interpretation - The frozen section showed a significantly higher performance compared with the alpha defensin test and a near perfect concordance with the definitive histology, and therefore remains an appropriate intraoperative screening test in diagnosing PJI. Although the sensitivity of the alpha defensin test was lower compared with that of frozen section, this test is highly specific for confirming the diagnosis of PJI.

Application of dermal chlorhexidine antisepsis is ineffective at reducing Proprionibacterium acnes colonization in shoulder surgery

BACKGROUND

Chlorhexidine as a skin surface antiseptic has been shown to be ineffective with respect to reducing Proprionibacterium acnes colonization within the dermis. The purpose of the present study was to determine whether the application of aqueous chlorhexidine solution to the dermal layer decreased P. acnes colonization during open shoulder surgery.

METHODS

The present study enrolled 50 patients who were undergoing open shoulder surgery. Patients received standard antimicrobial preparation. Three dermal swabs were taken from each patient: swab 1 following skin incision; swab taken 2 minutes to 5 minutes post-application of aqueous chlorhexidine to the dermis; and swab 3 taken 60 minutes post-application.

RESULTS

Mean age was 57.5 years (22 males, 28 females). There were 21 patients (42%) with P. acnes present on any dermal swab. There were significantly more P. acnes positive cultures identified at swab 3 compared to swab 1 (p = 0.043). In nine patients with positive P. acnes at cultures swab 1, eight also isolated P. acnes after at swabs 2 or 3. Males were significantly more likely to have P. acnes on any swab (p < 0.001). Positive P. acnes cultures were significantly more common in patients ≤50 years (p < .001). None of the patients had any clinical signs of infection at a minimum of 1 year following surgery.

CONCLUSIONS

Dermal application of aqueous chlorhexidine during open shoulder surgery fails to eradicate or reduce P. acnes on deep cultures.

Propionibacterium acnes Infection in Disc Material and Different Antibiotic Susceptibility in Patients With Lumbar Disc Herniation

BACKGROUND

Low back pain is an important, worldwide clinical problem from which human populations are suffering. It has been suggested that Propionibacterium acnes is associated with low back pain. The objective of this clinical study is to evaluate the P. acnes infection in the disc material and antibiotic susceptibility in patients with disc herniation.

METHODS

A total of 120 patients with disc herniation surgery were enrolled in the study. The samples were excited during discectomy and then cultured in both anaerobic and aerobic incubations. Minimum inhibitory concentration (MIC) was performed for determination of antibiotic susceptibility.

RESULTS

Of 120 samples, 60 (50%) samples were positive for microorganisms. Disc herniation was at the level of L4-L5 in 63 cases and L5-S1 in 57 cases.

CONCLUSIONS

According to the results and presence of P. acnes in more than 35% of the cultured samples, the presence of P. acnes in lumbar disc herniation is a suspected element leading to this condition. After analysis of the antibiotics, the lowest MIC value was identified for amoxicillin, ciprofloxacin, erythromycin, rifampicin, tetracycline, vancomycin; the moderate MIC value was for fusidic acid; and the highest MIC value was for gentamicin and trimethoprim.

Prevalence and quantification of contamination of knitted cotton outer gloves during hip and knee arthroplasty surgery

INTRODUCTION

Knitted cotton outer gloves offer protection against surgical glove perforation and provide improved grip on instruments. These gloves absorb blood and other fluids during surgery, and may therefore also accumulate contaminating bacteria. To date, there is no published data on microbial contamination of such gloves during surgery.

METHODS

Knitted cotton outer gloves used in primary and revision hip and knee arthroplasty from two Swiss hospitals were analysed by quantitative bacteriology. Samples were subjected to sonication and vortexing, followed by membrane filtration of the sonicate. Membranes were incubated under aerobic and anaerobic culture conditions, respectively, for 21 days. Total microbial load for each pair of gloves was determined by colony-forming units (CFU) count. Strain identification was performed with MALDI-TOF.

RESULTS

A total of 43 pairs of gloves were collected from continuous series of surgeries. Under aerobic culture conditions, total CFU counts ranged 0-1103, 25 (58%) samples remaining sterile, and 4 (9%) yielding > 100 CFU. Under anaerobic culture conditions, total CFU counts ranged 0-3579, 22 (51%) samples remaining sterile, 6 (14%) yielding > 100 CFU. The only covariate significantly associated with the level of contamination was the provider hospital (p < 0.0001 for aerobic and p = 0.007 for anaerobic cultures). Strain identification revealed only skin commensals, mainly coagulase-negative staphylococci and Propionibacterium spp.

CONCLUSION

While contamination of surgical latex gloves is a well-known issue, no study has examined so far contamination of knitted cotton outer gloves. No or very low microbial contamination could be identified in the majority of the knitted cotton outer gloves assayed. However, a relevant proportion showed contamination far higher than estimated minimal thresholds for implant-associated infection. Clinical relevance of these findings remains to be established.

Hemolysis Is a Diagnostic Adjuvant for Propionibacterium acnes Orthopaedic Shoulder Infections

INTRODUCTION

The purpose of this study was to further evaluate the pathogenicity of hemolytic and nonhemolytic phenotypes of Propionibacterium acnes (P acnes) isolates from shoulders of orthopaedic patients.

METHODS

Thirty-one patient records were reviewed, which had a positive P acnes shoulder culture from joint aspiration fluid and/or intraoperative tissues for demographics, clinical course, culture, and laboratory data. Patients were categorized as definite infection, probable infection, or probable contaminant. Antibiotic resistance patterns and hemolysis characteristics were subsequently analyzed.

RESULTS

Hemolysis demonstrated 100% specificity with a positive predictive value of 100% and 80% sensitivity with a negative predictive value of 73% for determining definite and probable infections. Hundred percent of the patients in the hemolytic group and only 27% of patients in the nonhemolytic group were classified as infected. Presenting inflammatory markers were markedly higher in the hemolytic group. Clindamycin resistance was found in 31% of the hemolytic strains, whereas no antibiotic resistance was observed in the nonhemolytic group.

CONCLUSION

Hemolytic strains of P acnes exhibit enhanced pathogenicity to their host by eliciting a more prominent systemic inflammatory response, increased antibiotic resistance, and a more challenging clinical course. Hemolysis may serve as a specific marker for assisting in diagnosing true infection with P acnes.

LEVEL OF EVIDENCE

Level III retrospective comparative study.

Cutibacterium (formerly Propionibacterium) acnes clavicular infection

Cutibacterium (formerly Propionibacterium) acnes^{13, 16} is a slow growing, gram-positive bacteria that is naturally found in higher concentrations as skin flora on the chest and back, as well as in other areas with greater numbers of hair follicles.^{25, 37} Most of the reported cases of C. acnes shoulder girdle infection follow arthroplasty surgery,^{18, 20, 26, 27, 32, 35} which then often requires debridement, administration of intravenous antibiotics, and surgical revision of the implanted device.^{12, 15, 21, 28-30} In a recent study, 56% of 193 shoulder revisions had a positive culture, 70% of which grew C. acnes.³⁰ Despite the relatively common presumed association of C. acnes humeral osteomyelitis with prosthetic infection, infection of the scapula or clavicle secondary to C. acnes is rare.^{4, 23, 36} Osteomyelitis of the clavicle involving any organism is also an uncommon event that can arise spontaneously via presumed hematogenous spread, or secondary to open fractures or internal fixation.^{6, 33} The most commonly found organism in clavicular osteomyelitis is Staphylococcus aureus.⁹ We here report two cases of clavicular infection secondary to C. acnes that were not associated with implants.

Outcomes of revision arthroplasty for shoulder periprosthetic joint infection: a three-stage revision protocol

BACKGROUND

This study evaluated outcomes after treatment of shoulder periprosthetic joint infection (PJI) with a 3-stage revision protocol consisting of (1) débridement, explantation, and cement spacer placement, followed by parenteral antibiotics; (2) open biopsy and débridement; and (3) reimplantation if cultures were negative. We hypothesized this protocol would eradicate persistent infection while producing excellent functional and subjective outcomes, and there would be no difference in these parameters for patients with shoulder PJI compared with patients with revision for aseptic indications.

METHODS

We retrospectively analyzed a prospectively collected revision shoulder arthroplasty cohort to identify shoulder PJI patients treated with a 3-stage protocol. Demographics, culture data, range of motion, and patient-reported outcomes were collected. Outcomes for patients with shoulder PJI and revision to RTSA were compared with patients revised to RTSA for noninfectious indications. Significance was defined as P < .05.

RESULTS

There were 28 cases of shoulder PJI in 27 patients (age, 66.4 ± 11.2 years,); of these, 21 shoulders were revised to RTSA, and 7 shoulders were revised to hemiarthroplasty. There was no recurrent infection at a mean 32-month follow-up. One year after surgery, mean forward flexion was 110° ± 41° and abduction was 106° ± 42°. Mean final American Shoulder and Elbow Surgeons subjective score was 66.5 ± 23.3. The 21 shoulders with PJI revised to RTSA had no differences for functional and subjective outcomes compared with revised patients without shoulder PJI.

CONCLUSIONS

A 3-stage revision protocol for shoulder PJI reliably eradicated infection. Patients with PJI revised to RTSA can have similar outcomes as patients with noninfectious revision to RTSA.

Routine Diagnostic Tests for Periprosthetic Joint Infection Demonstrate a High False-Negative Rate and Are Influenced by the Infecting Organism

BACKGROUND

Current guidelines recommend serum erythrocyte sedimentation rate (ESR) and C-reactive protein (CRP) as the first-line testing for evaluation of suspected periprosthetic joint infection, in addition to synovial white blood-cell (WBC) count and polymorphonuclear percentage. However, the sensitivity and other diagnostic measures of these tests using a standardized definition of periprosthetic joint infection and the influence of organisms on these inflammatory markers remain inadequately investigated.

METHODS

A retrospective review of an institutional database of 549 periprosthetic joint infection cases and 653 aseptic total joint arthroplasty revisions was performed. Periprosthetic joint infection was defined using major criteria from the International Consensus Meeting (ICM) on Periprosthetic Joint Infection. The mean inflammatory marker levels were compared among organisms with Student t tests and the proportions of elevated laboratory levels were compared among organisms with chi-square analyses. Receiver operating characteristic curve analyses were performed to calculate new cutoffs, sensitivities, and specificities for each organism and overall for serum CRP and ESR and synovial WBC and polymorphonuclear percentage.

RESULTS

The sensitivity of these markers for diagnosing chronic periprosthetic joint infection was 0.85 for ESR, 0.88 for CRP, 0.83 for WBC count, and 0.78 for polymorphonuclear percentage. For ESR, antibiotic-resistant organisms had higher mean values (84.3 mm/hr) than culture-negative cases (57.4 mm/hr), coagulase-negative Staphylococcus (68.3 mm/hr), and Streptococcus species (66.1 mm/hr); Staphylococcus aureus (81.0 mm/hr) was higher than culture-negative cases (57.4 mm/hr). For CRP, culture-negative cases had lower mean values (41.0 mg/L) than gram-negative organisms (87.4 mg/L), antibiotic-resistant organisms (86.0 mg/L), S. aureus (112.2 mg/L), and Streptococcus species (114.6 mg/L); S. aureus (112.2 mg/L) was higher than coagulase-negative Staphylococcus (66.0 mg/L). For WBC count, culture-negative cases had lower mean values (27,984.5 cells/mL) than S. aureus (116,250.0 cells/mL) and Streptococcus species (77,933.7 cells/mL). For polymorphonuclear percentage, there were no significant differences in mean values among all organisms.

CONCLUSIONS

It appears that serological markers, namely ESR and CRP, have a higher false-negative rate than previously reported. Synovial markers similarly exhibit high false-negative rates. Furthermore, the sensitivity of these tests appears to be related to organism type. Surgeons should be aware of the high rate of false-negatives associated with low-virulence organisms and culture-negative cases.

LEVEL OF EVIDENCE

Diagnostic Level I. See Instructions for Authors for a complete description of levels of evidence.

Polymicrobial anaerobic infection with a deep abscess in the supraspinous fossa following a subacromial corticosteroid injection

In September 2015, a male aged 61 years with poorly controlled diabetes (his only medical problem) had left shoulder surgery that included an arthroscopic acromioplasty with debridement of suture material from a rotator cuff repair done 10 years prior. A subacromial corticosteroid injection was given 7 months later for pain and reduced motion. Three weeks later a fulminate infection was evident. Cultures grew Propionibacterium acnes. Treatment included two arthroscopic debridement surgeries and 8 weeks of intravenous antibiotics (primarily daptomycin). Eight weeks after the cessation of the antibiotics, purulence recurred and tissue cultures then grew Staphylococcus epidermidis. Several additional surgeries were needed to control the infection. We failed to recognise that an abscess that extended from the subacromial space across the entire supraspinous fossa. We report this case to alert clinicians that a seemingly innocuous subacromial corticosteroid injection can lead to an atypical infection and also extend into the supraspinous fossa.

Culturing periprosthetic tissue in blood culture bottles results in isolation of additional microorganisms

Despite low sensitivity, culture of periprosthetic tissue (PPT) specimens on agars and in broths has traditionally been used for the detection of causative microorganisms in patients suspected for prosthetic joint infection (PJI). The aim of this study was to evaluate the added diagnostic value of culturing PPT in blood culture bottles (BCB) over the conventional combination of standard agar and broth alone. This prospective cohort study was conducted over a 12-month period and included consecutive patients undergoing revision arthroplasty. Overall, 113 episodes from 90 subjects were studied; 45 subjects (50.0%) met the Infectious Diseases Society of America (IDSA) criteria for PJI, of whom the majority (75.6%) had an acute infection. Sensitivity and specificity of culture were assessed using IDSA criteria for PJI as gold standard. Although the increase in sensitivity from 84.44 (CI 70.54; 93.51) to 93.33% (81.73; 98.60) was not significant, added diagnostic value of culturing PPT in BCBs was demonstrated by the significantly higher number of detected pathogens in culture sets with BCBs compared to culture without BCBs (61 pathogens in conventional set versus 89 when BCBs were included for 57 PJI episodes, P = <0.0001). In 17 (29.8%) episodes, microorganisms were cultured from BCBs only, and in 9 (52.9%) of these episodes, virulent pathogens were found. This study demonstrates that PPT culture in BCBs leads to isolation of additional microorganisms, both virulent and low-virulent, which were not cultured with use of agars and broths alone. Isolation of additional causative microorganisms has serious consequences for the treatment strategy in PJI.

Culturing Periprosthetic Joint Infection: Number of Samples, Growth Duration, and Organisms

BACKGROUND

Owing to the difficulty isolating microorganisms in periprosthetic joint infection (PJI), current guidelines recommend that 3-5 intraoperative samples be cultured and maintained for 3-14 days. We investigated (1) the optimal number of culture samples and growth duration to diagnose PJI and (2) the microbiology profile at our institution.

METHODS

A retrospective review of 711 patients (329 hips, 382 knees) with PJI that met Musculoskeletal Infection Society criteria from 2000 to 2014 was performed. Two thousand two hundred ninety aerobic and anaerobic cultures were analyzed. A manual chart review collected demographic, surgical, and microbiological data. Microbiology profiles were trended. Logistic regression analysis was performed to determine statistical significance.

RESULTS

Obtaining 5 samples provided the greatest yield positive cultures for diagnosing PJI. The percentage of positive cultures overall was 62.6% and stratified by organism type: antibiotic resistant (80.0%), Staphylococcus aureus (76.0%), gram negative (58.9%), Pseudomonas (52.0%), variant PJI organisms (28.2%), Propionibacterium acnes (20.0%), and Escherichia coli (8.0%). Although most organisms were cultured in 5 days or less, 10.8 days were needed for Propionibacterium acnes, 6.6 for variant PJI organisms, and 5.2 for coagulase-negative Staphylococcus. At 3 days, only 42.2% of cultures turned positive compared with 95.0% at 8 days. There was a significant decrease in time in gram-positive PJIs and an increase in culture-negative PJIs.

CONCLUSION

The optimal number of cultures and growth duration depended on the type of organism. This study provides evidence that 5 samples should be obtained and held for at least 8 days given that the type of organisms is likely to be unknown at the time of surgery.

Lactobacillus plantarum-derived Extracellular Vesicles Protect Atopic Dermatitis Induced by Staphylococcus aureus-derived Extracellular Vesicles

PURPOSE

The microbial environment is an important factor that contributes to the pathogenesis of atopic dermatitis (AD). Recently, it was revealed that not only bacteria itself but also extracellular vesicles (EVs) secreted from bacteria affect the allergic inflammation process. However, almost all research carried out so far was related to local microorganisms, not the systemic microbial distribution. We aimed to compare the bacterial EV composition between AD patients and healthy subjects and to experimentally find out the beneficial effect of some bacterial EV composition.

METHODS

Twenty-seven AD patients and 6 healthy control subjects were enrolled. After urine and serum were obtained, EVs were prepared from samples. Metagenomic analysis of 16s ribosomal DNA extracted from the EVs was performed, and bacteria showing the greatest difference between controls and patients were identified. In vitro and in vivo therapeutic effects of significant bacterial EV were evaluated with keratinocytes and with Staphylococcus aureus-induced mouse AD models, respectively.

RESULTS

The proportions of Lactococcus, Leuconostoc and Lactobacillus EVs were significantly higher and those of Alicyclobacillus and Propionibacterium were lower in the control group than in the AD patient group. Therefore, lactic acid bacteria were considered to be important ones that contribute to the difference between the patient and control groups. In vitro, interleukin (IL)-6 from keratinocytes and macrophages decreased and cell viability was restored with Lactobacillus plantarum-derived EV treatment prior to S. aureus EV treatment. In S. aureus-induced mouse AD models, L. plantarum-derived EV administration reduced epidermal thickening and the IL-4 level.

CONCLUSIONS

We suggested the protective role of lactic acid bacteria in AD based on metagenomic analysis. Experimental findings further suggest that L. plantarum-derived EV could help prevent skin inflammation.

Anterior cruciate ligament reconstruction complicated by Propionibacterium acnes infection: case series

Anterior cruciate ligament (ACL) reconstruction is one of the most commonly performed orthopaedic procedures. While generally successful, failure resulting in revision surgery is reported to be between 1.9 - 4.9%. However, when not related to traumatic re-injury, failure mechanism is poorly understood. One potential but understudied mechanism of ACL reconstruction failure is infection. We describe three patients with previous ACL reconstructions who later developed infection with Propionibacterium acnes. Two cases presented with knee pain and swelling, and one presented with instability. While only two of the three cases received antibiotic treatment, all three cases were free of knee and infectious symptomatology at most recent follow-up. P. acnes infection may represent one potential mechanism for biologic failure of ACL reconstruction and anaerobic operative cultures may be used to identify its presence.

Orthopedic implant-associated infections caused by Cutibacterium spp. - A remaining diagnostic challenge

Background

The definition criteria and clinical characteristics of implant-associated infection (IAI) caused by Cutibacterium (formerly Propionibacterium) spp. are poorly known. We analyzed microbiologically proven Cutibacterium orthopedic IAI in a prospective cohort.

Methods

Patients with periprosthetic joint infections (PJI) and fixation device–associated infections (FDAI) caused by Cutibacterium spp. were prospectively included. IAI was defined by significant growth of Cutibacterium spp. and presence of at least one non-microbiological criterion for infection. The McNemar’s chi-squared or binomial test was used to compare the performance of diagnostic tests.

Results

Of 121 patients with Cutibacterium IAI, 62 patients (51%) had PJI and 59 (49%) had FDAI. 109 infections (90%) were caused by C. acnes and 12 (10%) by C. avidum. The median time from implantation until diagnosis of infection was 15.7 months (interquartile range, 5–46.5 months). Clinical local signs were present in 30 patients (28%) and radiological implant loosening in 64 patients (63%). Culture sensitivity of sonication fluid was 84%, of peri-implant tissue 84% and of synovial or peri-implant fluid 56% after 14 days of incubation.

Conclusion

Cutibacterium IAI was diagnosed late in the disease course and presented with subtle signs. Prolonged culture incubation and implant sonication improved the poor performance of conventional microbiological tests. Due to lack of reliable diagnostic tests, Cutibacterium remains difficult to detect making the diagnosis challenging.

What Is the Role of Diagnostic and Therapeutic Sonication in Periprosthetic Joint Infections?

BACKGROUND

Periprosthetic joint infection (PJI) is one of the most dreaded complications in joint replacement surgery. Diagnosis and treatment can be difficult and biofilms are of major concern due to their low susceptibility toward antibiotics.

METHODS

This review focuses on the use of sonication as an evolving diagnostic and adjunct treatment modality in the context of PJI. Therapeutic application of sonication is discussed separately for its (i) direct action on bacteria, (ii) synergistic effects with antibiotics, and (iii) effects on release of antibiotics from bone cement.

RESULTS

Used as a diagnostic tool, sonication shows promising results with respect to sensitivity and specificity when compared to conventional methods, notably after previous administration of antibiotics. As an adjunct treatment modality, the chemical, physical, and mechanical effects of sonication are primarily driven by cavitation and recognized as the main cause for bactericidal effects but the exact underlying mechanisms have not been identified yet. Sonication alone does not have the ability to completely eradicate biofilms but synergistic effects when used in conjunction with antibiotics have been reported. There is also evidence for enhanced antibiotic release from bone cement.

CONCLUSION

Sonication is as an evolving modality in the context of PJIs. As a diagnostic tool, it has not been introduced in routine clinical practice and sonication as a treatment modality in PJIs is still in an experimental stage. Factors such as frequency, pressure, chemical activity, intensity, and exposure time need to be evaluated for optimal application of sonication and may also improve study comparison.

Low-Virulence Organisms and Periprosthetic Joint Infection-Biofilm Considerations of These Organisms

PURPOSE OF REVIEW

The purpose of this manuscript is to provide a critical review of peer-reviewed literature over the last 5 years related to low virulent organisms associated with periprosthetic joint infection (PJI). We evaluated the most common organisms, the diagnostic challenges, and the novel tools available in the perioperative workup of PJI as well as the current understanding of how biofilm potentiates the indolent clinical presentation and explore a possible shift in the surgical management of these patients.

RECENT FINDINGS

Biofilm actively prevents macrophage phagocytosis by suppressing proinflammatory activity through the recruitment of myeloid-derived suppressor cells. Given the appropriate host and organism conditions, increased utilization of one-stage exchange arthroplasty in the surgical treatment of these low virulent infections may be on the rise. Biomarkers and molecular techniques offer encouraging results to diagnose low virulent organisms and future research focused on the disruption of biofilm may ultimately give rise to improved treatment strategies.

Preoperative Doxycycline Does Not Reduce Propionibacterium acnes in Shoulder Arthroplasty

BACKGROUND

Propionibacterium acnes (P. acnes) is the most common bacteria associated with infection after shoulder arthroplasty. These bacteria can be grown on culture of skin after standard preoperative skin preparation and antibiotics. The purpose of this study was to determine whether adding preoperative intravenous doxycycline reduces the prevalence of positive P. acnes cultures of skin and deep tissues at the time of prosthetic joint implantation during shoulder arthroplasty.

METHODS

This was a randomized controlled trial. An a priori power analysis determined that a sample size of 56 patients was necessary. Patients scheduled to undergo shoulder arthroplasty were randomized to receive either standard perioperative cefazolin or a combination of doxycycline and cefazolin. Tissue specimens for culture were then taken from the skin edge, and swabs of the superficial dermal tissue and glenohumeral joint were obtained. All cultures were maintained for 14 days to allow for P. acnes detection. Groups were compared to determine if the addition of doxycycline reduced the rate of culture positivity.

RESULTS

Fifty-six patients were enrolled and randomized. Twenty-one (38%) had ≥1 positive cultures for P. acnes, with no significant difference between the group treated with cefazolin alone (10 [37%] of 27 patients) and the combined doxycycline and cefazolin group (11 [38%] of 29 patients) (p = 0.99). The greatest numbers of culture-positive samples were obtained from the skin (30%), followed by dermal tissue (20%) and the glenohumeral joint (5%). Patients who had ≥1 positive cultures were younger than those who did not (mean age [and standard deviation], 64.9 ± 7.7 versus 69.4 ± 7.7 years; p = 0.041), had a greater tendency to be male (16 [76%] of 21 versus 17 [49%] of 35; p = 0.053), and had a lower Charlson Comorbidity Index (3.35 ± 1.3 versus 4.09 ± 1.4; p = 0.051). There were no significant differences between the culture-positive and culture-negative groups in terms of body mass index (BMI) (p = 0.446) or arthroplasty type, with positive cultures found for 8 of the 29 anatomic shoulder arthroplasty procedures compared with 13 of the 27 reverse shoulder arthroplasty procedures (p = 0.280). There were no doxycycline-related adverse events.

CONCLUSIONS

In this randomized controlled trial, doxycycline did not significantly decrease P. acnes culture positivity of the skin, dermis, or glenohumeral joint of patients undergoing shoulder arthroplasty. The addition of prophylactic intravenous antibiotics to cover P. acnes may not be an effective method to reduce postoperative and periprosthetic shoulder joint infections.

LEVEL OF EVIDENCE

Therapeutic Level I. See Instructions for Authors for a complete description of levels of evidence.

Propionibacterium Acnes Persists Despite Various Skin Preparation Techniques

PURPOSE

To investigate the efficacy of various skin preparations at eradicating Propionibacterium acnes in the dermal layer of the skin.

METHODS

Twelve healthy volunteers consented to participate in this study. Each subject's upper back was prepped using 4 different techniques: an isopropyl alcohol control, chlorhexidine gluconate paint, chlorhexidine gluconate plus a mechanical scrub, and a high-concentration chlorhexidine gluconate plus a mechanical scrub. A 3-mm dermal punch biopsy specimen was obtained at each preparation site. The 4 punch biopsy specimens were cultured for 14 days to assess for P. acnes growth. A Fisher's exact test was used to compare the proportion of positive cultures in each group and across biopsy sites. A Skillings-Mack test was used to compare the degree of culture positivity between the treatment arms.

RESULTS

There were no reported complications in any of our subjects. P. acnes grew in 7 of the 12 control sites, 5 of the 12 chlorhexidine gluconate sites, 6 of the 12 chlorhexidine plus mechanical scrub sites, and 6 of the 12 high-concentration chlorhexidine gluconate plus mechanical scrub sites. There were no statistically significant differences between any of the treatment arms (P = .820).

CONCLUSIONS

P. acnes persisted despite a variety of clinically relevant skin antisepsis preparations and techniques.

LEVEL OF EVIDENCE

Level II, prospective comparative study.

Hamstring autografts are associated with a high rate of contamination in anterior cruciate ligament reconstruction

PURPOSE

To quantitatively evaluate the rate, type, and level of contamination of anterior cruciate ligament (ACL) hamstring autografts after harvesting and preparation or dropping onto the operating room (OR) floor.

METHODS

Two hamstring autograft specimens were prospectively retrieved from each graft in a consecutive series of 50 patients undergoing primary isolated ACL reconstruction (100 specimens total). One specimen was retrieved immediately after harvesting and dropped onto the OR floor (dropped group). The other was retrieved just after graft implantation and before fixation (control group). Each specimen was incubated for aerobic and anaerobic growth, and the number of colony-forming units (CFU)/g was measured. Patients' clinical course was monitored for signs of surgical site infection (SSI).

RESULTS

The control and dropped groups had positive culture rates of 11/50 (22%) and 16/50 (32%), respectively, with no significant difference between groups (n.s.). The most common organism in the control group was Staphylococcus epidermidis (45.5%) followed by S. aureus (36.4%). In the dropped group, the most common organism was S. epidermidis (31.3%) followed by Bacillus species (25%). The median (range) CFU/g among positive specimens in the dropped and control groups was 65 (8-150) and 10 (2-60), respectively (P = 0.0003). No patient developed postoperative SSI.

CONCLUSION

Intraoperative hamstring autograft contamination rates were high. Hence, routine prophylactic decontamination of all hamstring autografts after harvesting and preparation and before implantation is recommended.

LEVEL OF EVIDENCE

Controlled laboratory study.

Preoperative skin cultures are predictive of Propionibacterium load in deep cultures obtained at revision shoulder arthroplasty

BACKGROUND

Propionibacterium-specific cultures are commonly positive in revised shoulders without obvious signs of infection. To help identify patients at risk for these "stealth" presentations of positive Propionibacterium cultures, we assessed the value of a preoperative skin culture in predicting the results of deep cultures obtained at the time of revision shoulder arthroplasty in patients without clinical evidence of infection.

METHODS

The study enrolled 60 patients undergoing revision for a prior shoulder arthroplasty without clinical evidence of infection. A preoperative culture of the skin surface was taken before skin preparation. At surgery, multiple (mean 5.9 ± standard deviation 1.6) deep tissue and explant cultures were harvested from the shoulder. Each culture was semiquantitatively reported as the specimen Propionibacterium value (SpPV). All SpPVs from the deep specimens from each patient were summed as the total shoulder Propionibacterium score (ShPS). The averaged ShPS was the total ShPS divided by the number of deep specimens harvested.

RESULTS

A multivariate analysis demonstrated that the preoperative skin SpPV was predictive of the Propionibacterium load in the revised shoulders as indicated by the total ShPS (P = .004) and averaged ShPS (P = .003).

CONCLUSIONS

In this series of patients, a preoperative culture of the unprepared skin was strongly predictive of the Propionibacterium load in revised shoulder arthroplasties without clinical evidence of infection. This result suggests that the results of skin cultures taken before revision surgery may help inform operative management with respect to the need for prosthesis exchange and extended postoperative antibiotic treatment.

Prevalence of Propionibacterium acnes in the glenohumeral compared with the subacromial space in primary shoulder arthroscopies

HYPOTHESIS

We hypothesized that the prevalence of Propionibacterium acnes in patients undergoing primary shoulder arthroscopy is equal in the glenohumeral space compared with the subacromial space.

METHODS

Patients aged 18 years or older with shoulder arthroscopies were included. The exclusion criteria were prior shoulder operations, complete rotator cuff tears, systemic inflammatory diseases, tumors, shoulder injections within 6 months of surgery, and antibiotic therapy within 14 days preoperatively. After standardized skin disinfection with Kodan Tinktur Forte Gefärbt, a skin swab was taken at the posterior portal. Arthroscopy was performed without cannulas, prospectively randomized to start either in the glenohumeral space or in the subacromial space, with direct harvesting of a soft-tissue biopsy specimen. Sample cultivation was conducted according to standardized criteria for bone and joint aspirate samples and incubated for 14 days. Matrix-assisted laser desorption-ionization time-of-flight spectrometry was used for specimen identification in positive culture results.

RESULTS

The study prospectively included 115 consecutive patients with normal C-reactive protein levels prior to surgery (54.8% men; mean age, 47.2 ± 14.6 years). P acnes was detected on the skin after disinfection in 36.5% of patients, in the glenohumeral space in 18.9%, and in the subacromial space in 3.5% (P = .016).

CONCLUSION

The prevalence of P acnes is significantly higher in the glenohumeral space compared with the subacromial space in primary shoulder arthroscopies. The results do not confirm the contamination theory but also cannot clarify whether P acnes is a commensal or enters the joint hematologically or even lymphatically or via an unknown pathway. Despite standardized surgical skin disinfection, P acnes can be detected in skin swab samples in more than one-third of patients.

Differential Contributions of Specimen Types, Culturing, and 16S rRNA Sequencing in Diagnosis of Prosthetic Joint Infections

Prosthetic joint failure is mainly caused by infection, aseptic failure (AF), and mechanical problems. Infection detection has been improved with modified culture methods and molecular diagnostics. However, comparisons between modified and conventional microbiology methods are difficult due to variations in specimen sampling. In this prospective, multidisciplinary study of hip or knee prosthetic failures, we assessed the contributions of different specimen types, extended culture incubations, and 16S rRNA sequencing for diagnosing prosthetic joint infections (PJI). Project specimens included joint fluid (JF), bone biopsy specimens (BB), soft-tissue biopsy specimens (STB), and swabs (SW) from the prosthesis, collected in situ, and sonication fluid collected from prosthetic components (PC). Specimens were cultured for 6 (conventional) or 14 days, and 16S rRNA sequencing was performed at study completion. Of the 156 patients enrolled, 111 underwent 114 surgical revisions (cases) due to indications of either PJI (n = 43) or AF (n = 71). Conventional tissue biopsy cultures confirmed PJI in 28/43 (65%) cases and refuted AF in 3/71 (4%) cases; one case was not evaluable. Based on these results, minor diagnostic adjustments were made. Fourteen-day cultures of JF, STB, and PC specimens confirmed PJI in 39/42 (93%) cases, and 16S rRNA sequencing confirmed PJI in 33/42 (83%) cases. One PJI case was confirmed with 16S rRNA sequencing alone and five with cultures of project specimens alone. These findings indicated that JF, STB, and PC specimen cultures qualified as an optimal diagnostic set. The contribution of sequencing to diagnosis of PJI may depend on patient selection; this hypothesis requires further investigation.

Cutibacterium acnes prosthetic joint infection: Diagnosis and treatment

Cutibacterium acnes is a commensal skin bacterium, regularly implicated in prosthetic joint infection, particularly of the shoulder. Diagnosis has been improved by progress in bacteriological techniques: longer culture time, liquid medium culture, MALDI-TOF mass spectrography, and universal 16S rRNA PCR, associated by some authors to sonication of ablated implants. C. acnes pathogenicity involves many virulence factors, notably including biofilm formation. C. acnes may lead to infection that is clinically evident or, frequently, relatively asymptomatic. C. acnes is an anaerobic Gram-positive bacterium, susceptible to many antibiotics that are regularly used in bone and joint infection: beta-lactams, quinolone, rifampicin and clindamycin. It shows increasing resistance to clindamycin and natural resistance to metronidazole. Treatment is medical and surgical, associating synovectomy or complete 1- or 2-step revision depending on time to treatment, and antibiotic therapy. Antibiotic therapy is typically for three months with an initial 2-6 weeks' intravenous phase. Prognosis is generally favorable with well-conducted treatment. Late discovery of positive samples after apparently aseptic implant change is an at-risk situation, usually managed by antibiotic therapy, but with late initiation and hence increased risk of failure. Adverse secondary progression requires repeat revision under good conditions.

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

BACKGROUND

Diagnosing infection after shoulder arthroplasty can be a challenge because of the high prevalence of low-virulence organisms, such as Propionibacterium acnes. The purpose of this study was to evaluate the utility of implant sonication fluid cultures in the diagnosis of periprosthetic joint infection compared with standard culture techniques in patients undergoing revision shoulder arthroplasty.

METHODS

Routine perioperative testing was performed 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. Diagnostic performance of implant sonication culture was determined on the basis of previously defined infection criteria and compared with standard intraoperative cultures.

RESULTS

Of the 53 revision cases that underwent implant sonication fluid culture, 25 (47%) were classified as infected. Intraoperative culture (tissue and fluid) sensitivity, specificity, positive predictive value (PPV), negative predictive value (NPV), and accuracy were 96%, 75%, 77%, 95%, and 85%, respectively. Using a cutoff of >20 colony-forming units per milliliter to exclude contaminants, the sensitivity, specificity, PPV, NPV, and accuracy of implant sonicate culture were 56% (P < .001, compared with standard intraoperative cultures), 93% (P = .07), 88% (P = .4), 70% (P = .02), and 75% (P = .22), respectively. Without use of a sonication fluid culture cutoff value, the sensitivity, specificity, PPV, NPV, and accuracy of implant sonicate culture were 96% (P = 1.0, compared with standard intraoperative cultures), 64% (P = .38), 71% (P = .53), 95% (P = .9), and 79% (P = .45).

CONCLUSIONS

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

Periprosthetic joint infection caused by anaerobes. Retrospective analysis reveals no need for prolonged cultivation time if sensitive supplemented growth media are used

BACKGROUND

In microbiological diagnosis of periprosthetic joint infection (PJI) culture media and incubation time are controversially discussed, especially if anaerobic bacteria are the causative agent. This study was conducted to demonstrate the influence of sensitive supplemented growth media on the duration of culturing anaerobes.

METHODS

Twenty-five consecutive cases were included in this retrospective study. For definition of PJI, the criteria of the Musculoskeletal Infection Society (MSIS) were considered. Histopathological analysis was interpreted according to the classification by Krenn et al. The quantity and time to positivity of detected anaerobes were monitored. Furthermore, antimicrobial activity within the tissue and sonicate fluid was phenotypically tested.

RESULTS

In all cases, even if the patients had received antibiotics before recovery, culture of anaerobes (Propionibacterium species, Finegoldia magna, Parvimonas micra and Robinsoniella peoriensis), both from tissue samples and prosthetic components, first became detectable in supplemented liver thioglycollate broth within six days (median: four days).

CONCLUSION

Recommendations for prolonged cultivation for up to 14 days mostly aim at detection of anaerobes. Here we present a laboratory procedure that can shorten cultivation time considerably.

Diagnosis of Prosthetic Joint Infection: Cultures, Biomarker and Criteria

Prosthetic joint infections (PJIs) are devastating complications after joint arthroplasty that continue to pose a diagnostic challenge. Currently, a single, stand-alone test with the adequate accuracy and reliability for diagnosis of PJI is not available; therefore, physicians who care for patients with PJI must rely on a combination of diagnostic tests for the diagnosis of PJI. This article reviews conventional laboratory test modalities, diagnostic accuracy and limitations of current tests, and novel emerging tests for the diagnosis of PJI.

Diagnostic Methods for Prosthetic Joint Infection in Korea

Prosthetic joint infection (PJI) poses a burden on patients and health care resources. PJI diagnosis can be challenging, owing to imperfect definition, alongside inadequate diagnostic techniques. In this review, we describe consensus definitions of PJI, approaches to diagnosis using methods available in Korea, and novel diagnostic methods.

Performance of the BacT/Alert Virtuo Microbial Detection System for the culture of sterile body fluids: prospective multicentre study

OBJECTIVES

Continuous monitoring blood culture systems are commonly used for sterile body fluid cultures. In this multicentre study, we evaluated the performance of the new-generation BacT/Alert Virtuo system compared to the BacT/Alert 3D and conventional culture for the recovery of microorganisms from sterile body fluids.

METHODS

Peritoneal, cerebrospinal, pericardial, pleural and synovial fluids from adult patients submitted for culture were collected from three different centres. Specimens were inoculated into two bottles of the same bottle type (SA, SN, FA Plus or FN Plus) in equal volumes for simultaneous incubation in the Virtuo and 3D instruments. Each specimen was also Gram stained and seeded to solid media.

RESULTS

A total of 811 specimens were inoculated to 1257 bottle pairs. The Virtuo and 3D showed equivalent recovery of clinically significant microorganisms (127/155, 81.9%, vs. 126/155, 81.3%, respectively). Solid media cultures recovered fewer pathogens than either continuous monitoring system (95/155, 61.3%, p <0.001), including significantly fewer Enterobacteriaceae and enterococci. The Virtuo was significantly faster than the 3D in median time to detection of isolates from the same specimen (12.5 (range, 2.8-101.5) hours vs. 15.5 (range, 4.3-78.5) hours, p <0.001). Direct specimen Gram stain detected the eventual pathogen in 30 (26.1%) of 115 significant positive specimens.

CONCLUSIONS

The BacT/Alert Virtuo system was equivalent to the 3D system in organism recovery from sterile body fluid culture but showed faster detection of growth as a result of design enhancements.

Cutibacterium (formerly Propionibacterium) acnes infections associated with implantable devices

INTRODUCTION

Cutibacterium acnes (C. acnes), a Gram-positive biofilm-forming rod implicated in acne vulgaris, is increasingly recognized for its role in implant-associated infections. The diagnosis of C. acnes implant-associated infections remains challenging. The optimal treatment is a combination of both surgical intervention and antibiotic therapy. Areas covered: In this review, we discuss the different types of implant-associated infections caused by C. acnes. We also highlight the clinical manifestations pertaining to the various sites of infection, and identify several risk factors previously reported in the literature. We then cover the diagnostic laboratory markers, such as IL-6 and AD-1, optimizing C. acnes recovery in culture, and the specific molecular techniques. Finally, we examine the various effective antibiotic regimens and identify some preventive methods against C. acnes infections. Expert commentary: Biomarkers such as IL-6 and AD-1 should be further investigated for the diagnosis of C. acnes implant-associated infections. The use of 16S rRNA gene sequencing and other molecular techniques should be further explored in this setting. Longer incubation periods should be requested whenever C. acnes infection is suspected. If the clinical suspicion is high, sonication of the excised implant should be encouraged. Research should focus on developing effective anti-biofilm agents. Finally, preventive methods such as hair removal prior to surgery should be further explored.

Routine cultures for seemingly aseptic revision shoulder arthroplasty: are they necessary?

Propionibacterium acnes has recently gained attention as the leading cause of periprosthetic joint infections (PJIs) after shoulder arthroplasty. Unlike PJIs in the lower extremity, PJIs after shoulder arthroplasty usually have an indolent course and are notoriously difficult to diagnose. Most of the time, the diagnosis is made after positive intraoperative cultures are taken at the time of revision surgery. Adding even more complexity to the diagnosis is the high rate of P acnes-positive cultures taken at the time of primary shoulder surgery. In many cases the preoperative workup yields no suspicion for infection; however, intraoperative cultures are taken to completely eliminate the potential of an ongoing indolent infection. Concerns over how to interpret positive P acnes culture results and the high rate of culture positivity in primary shoulder arthroplasty, as well as the potentially high rate of contamination, have led surgeons to wonder about the utility of obtaining intraoperative cultures at the time of revision shoulder arthroplasty. We present evidence for and against the practice of obtaining routine intraoperative cultures at the time of seemingly aseptic revision shoulder arthroplasty.

The unsuspected prosthetic joint infection

Aims

Positive cultures are not uncommon in cases of revision total knee and hip arthroplasty (TKA and THA) for presumed aseptic causes. The purpose of this study was to assess the incidence of positive intra-operative cultures in presumed aseptic revision of TKA and THA, and to determine whether the presence of intra-operative positive cultures results in inferior survival in such cases.

Patients and Methods

A retrospective cohort study was assembled with 679 patients undergoing revision knee (340 cases) or hip arthroplasty (339 cases) for presumed aseptic causes. For all patients three or more separate intra-operative cultures were obtained. Patients were diagnosed with a previously unsuspected prosthetic joint infection (PJI) if two or more cultures were positive with the same organism. Records were reviewed for demographic details, pre-operative laboratory results and culture results. The primary outcome measure was infection-free implant survival at two years.

Results

The incidence of unsuspected PJI was 27 out of 340 (7.9%) in TKA and 41 out of 339 (12.1%) in THA. Following revision TKA, the rate of infection-free implant survival in patients with an unsuspected PJI was 88% (95% confidence intervals (CI) 60 to 97) at two years compared with 98% (95% CI 94 to 99) in patients without PJI (p = 0.001). After THA, the rate of survival was similar in those with unsuspected PJI (92% (95% CI 73 to 98) at two years) and those without (94% (95% CI 89 to 97), p = 0.31).

Conclusion

Following revision of TKA and THA for aseptic diagnoses, around 10% of cases were found to have positive cultures. In the knee, such cases had inferior infection-free survival at two years compared with those with negative cultures; there was no difference between the groups following THA. Cite this article: Bone Joint J 2017;99-B:1482–9.

Impact of Sequential Culture Results on Diagnosis and De-Escalation of the Antibiotic Regimen in Joint and Bone Infections

BACKGROUND

According to existing guidelines, orthopedic specimens collected in joint and bone infections (JBI) in our institution are cultured on several media sets and incubated for two, seven, and 14 days. The optimal timing for de-escalation of the first-line antibiotic combination according to the culture results needs to be defined.

METHODS

Single-center, retrospective analysis of all adult patients with a first documented episode of JBI between May 2012 and April 2013.

RESULTS

Ninety patients were included, 51 males (57%), median age 58 y (range 18-87 y), with prosthesis infection in 62 cases (69%). Rapidly growing pathogens (Staphylococcus aureus [n = 36] and Enterobacteriaceae [n = 12]) usually were diagnosed within two days, whereas coagulase-negative staphylococci (n = 25) and Propionibacterium acnes (n = 13) generally were identified after seven days (p < 10^-5). Positive culture results at day 2 fit with definitive microbiological diagnosis in 95% of cases, and prolonged incubation led to the identification of additional micro-organisms in only four of 76 patients (5%) with day-2-positive cultures. Conversely, for those with negative two-day culture (n = 14), the seven-day culture allowed identification of less virulent pathogens in eight cases (57%).

CONCLUSIONS

Our results suggest that, in JBI, de-escalation of the empirical antibiotic regimen can be based on micro-organisms identified on the two-day culture set. The impact of such a strategy on clinical outcomes, antibiotic consumption, and costs needs to be assessed in larger studies.

The colonisation of the glenohumeral joint by Propionibacterium acnes is not associated with frozen shoulder but is more likely to occur after an injection into the joint

AIMS

Our aim was to investigate the prevalence of Propionibacterium (P.) acnes in the subcutaneous fat and capsule of patients undergoing shoulder surgery for frozen shoulder or instability.

PATIENTS AND METHODS

A total of 46 patients undergoing either an arthroscopic capsular release or stabilisation had biopsies taken from the subcutaneous fat and capsule of the shoulder at the time of surgery. These samples were sent for culture in enrichment, and also for Nucleic Acid Amplification testing. The prevalence of P. acnes and other microbes was recorded. Fisher's exact test of binary variables was used to calculate the association with significance set at p < 0.05. Assessment of influence of independent variables including a pre-operative glenohumeral injection, fat colonisation and gender, was undertaken using binary linear regression.

RESULTS

A total of 25 patients (53%) had P. acnes in one or more tissue samples and 35 (74%) had other bacterial species. The same microbe was found in the subcutaneous fat and the capsule in 13 patients (28%). There was no statistically significant association between the surgical pathology and capsular colonisation with P. acnes (p = 0.18) or mixed identified bacterial species (p = 0.77). Male gender was significantly associated with an increased capsular colonisation of P. acnes (odds ratio (OR) 12.38, 95% confidence interval (CI) 1.43 to 106.77, p = 0.02). A pre-operative glenohumeral injection was significantly associated with capsular P. acnes colonisation (OR 5.63, 95% CI 1.07 to 29.61, p = 0.04. Positive fat colonisation with P. acnes was significantly associated with capsular P. acnes (OR 363, 95% CI 20.90 to 6304.19, p < 0.01). Regression models pseudo R² found fat colonisation with P. acnes to explain 70% of the variance of the model. Patients who had a pre-operative glenohumeral injection who were found intra-operatively to have fat colonisation with P. acnes had a statistically significant association with colonisation of their capsule with P. acnes (OR 165, 95% CI 13.51 to 2015.24, p < 0.01).

CONCLUSION

These results show a statistically significant association between subcutaneous skin P. acnes culture and P. acnes capsular culture, especially when the patient has undergone a previous injection. The results refute the hypothesis that P. acnes causes frozen shoulder. Cite this article: Bone Joint J 2017;99-B:1067-72.

Preoperative doxycycline does not decolonize Propionibacterium acnes from the skin of the shoulder: a randomized controlled trial

BACKGROUND

Propionibacterium acnes is frequently cultured in patients undergoing both primary and revision shoulder surgery. The purpose of this study was to evaluate the efficacy and safety of preoperative oral administration of doxycycline in decreasing the colonization of skin around the shoulder by P. acnes.

METHODS

This was a single-institution, prospective, randomized controlled trial of male patients undergoing shoulder arthroscopy. Patients were randomized to receive oral doxycycline (100 mg twice a day) for 7 days or to the standard of care (no drug). Before skin incision, 2 separate 3-mm punch biopsy specimens were obtained from the sites of the anterior and posterior arthroscopic portals and were sent for culture in anaerobic and aerobic medium held for 13 days.

RESULTS

There were 22 of 37 (59.5%) patients in the no-drug group and 16 of 37 (43.2%) patients in the doxycycline group who had at least 1 dermal culture positive for P. acnes (P = .245). In the no-drug group, 10 patients (45.5%) had 1 positive culture and 12 (54.5%) had 2 positive cultures (34 total positive cultures [45.9%]). In the doxycycline group, 6 (37.5%) patients had 1 positive culture and 10 (62.5%) had 2 positive cultures (26 total positive cultures [35.1%]; P = .774).

DISCUSSION

Administration of oral doxycycline for 7 days before surgery did not reduce colonization of P. acnes significantly. Given the potential risk for emergence of bacterial resistance and the adverse effects associated with administration of antibiotics, we do not recommend routine use of oral doxycycline for preoperative decolonization of the shoulder.

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.

Utility of strain typing of Propionibacterium acnes in central nervous system and prosthetic joint infections to differentiate contamination from infection: a retrospective cohort

The study aimed to retrospectively assess if strain typing of Propionibacterium acnes could help to distinguish between infection and contamination in isolates recovered from the central nervous system (CNS) and prosthetic joints (PJs). This was a retrospective cohort of all Propionibacterium species isolates from the Barnes-Jewish Hospital (St Louis, MO, USA) clinical microbiology laboratory from 2011 to 2014. Available frozen isolates were recovered, and strain type (IA-1, IA-2, IB, II, III, or nontypeable class A or B) was determined via polymerase chain reaction (PCR)-based methods. For CNS isolates, P. acnes was considered pathogenic if treating physicians administered ≥7 days of directed antibiotic therapy against P. acnes. During the study period, Propionibacterium species was isolated from clinical cultures 411 times. 152 isolates were available for analysis. Of the 152 isolates, 140 were confirmed to be P. acnes, 61 of which were from the CNS (45 contaminants, 16 infections). Strain type IA-1 was more common (50.0%, 8 out of 16) among CNS infections than among contaminants (22.2%, 10 out of 45). For PJ isolates 61.3% (19 out of 31) met the criteria for infection. The predominant strain type for CNS infection was IA-1 and for PJ isolates, IB. Strain type IA-1 was isolated more often in patients with CNS infections, which may indicate a predilection of this strain type to cause CNS infection. Future research should prospectively evaluate strain typing as a means of assisting in the diagnosis of CNS infections and confirm our findings.

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.

A comparison of culture and PCR methods for identifying Propionibacterium acnes in lesions isolated from patients with acne

BACKGROUND/AIM

One of the factors that affect the occurrence of acne is the presence of Propionibacterium acnes. The present study was conducted to compare the culture and polymerase chain reaction (PCR) methods for identifying P. acnes in lesions isolated from patients with acne.

MATERIALS AND METHODS

To examine the presence of P. acnes, 70 samples of acne lesions were collected. Microbial culture and the PCR molecular technique were used to identify P. acnes.

RESULTS

Of the total of 70 samples, 14 cases (20%) were identified as P. acnes positive using microbial culture and 58 cases (82.85%) using PCR. The results obtained showed the lack of a relationship between the frequency of P. acnes and factors such as sex, family history of acne, and history of treatment with either of the techniques examined (i.e. the microbial culture and PCR). In contrast, a significant relationship was observed between the frequency of P. acnes and age with the culture method.

CONCLUSION

Given the limitations in the identification of P. acnes using microbial culture, PCR is proposed as a better method with a higher efficiency.

Future surgery after revision shoulder arthroplasty: the impact of unexpected positive cultures

BACKGROUND

The clinical implications and treatment of unexpected positive cultures (UPCs) in revision shoulder arthroplasty are not well defined. The purpose of this study was to describe results of patients with and without UPCs after revision shoulder arthroplasty.

METHODS

A single institutional database was used to retrospectively identify all revision shoulder arthroplasties performed between January 1, 2011, and December 31, 2013. Patients with preoperative suspicion of infection were excluded. Multivariable regression analysis was used to identify risk factors for future surgery after revision shoulder arthroplasty.

RESULTS

There were 117 revision shoulder arthroplasties without preoperative suspicion of infection. There were 28 of 117 (23.9%) with UPCs, of which 15 (57.1%) were Propionibacterium acnes; 18 of 28 (64.3%) patients received antibiotics for 6 weeks postoperatively without complications compared with 10 of 28 (35.7%) who received a routine 2-week empirical antibiotic regimen; 2 of 28 (7.1%) patients with UPCs required future surgery, and only 1 (3.6%) had a recurrent infection. Comparatively, 18 of 89 (20.2%) patients without UPCs (P = .109) required 25 additional surgeries. Average time to UPC was 4.3 years after index revision. Multivariable regression analysis of patient demographics, comorbidities, surgical procedure, and presence of UPCs found no independent predictors of reoperation.

DISCUSSION

Nearly one-quarter of our institution's revision shoulder arthroplasties had UPCs. The patients without UPCs had a nonsignificantly higher risk of reoperation compared with those with UPCs. We did not identify clinical or demographic variables that independently correlated with reoperation. Further study will be necessary to determine the true clinical benefit of routine culture acquisition in cases with low suspicion for prosthetic joint infection.