Biofilm formation by bacteria isolated from retrieved failed prosthetic hip implants in an in vitro model of hip arthroplasty antibiotic prophylaxis

A Case of Coccidioidal Meningitis With Biofilm Obstructing VP Shunt Due to Cutibacterium acnes

Herein described is a case of biofilm obstructing ventriculoperitoneal shunt due to Cutibacteirum acnes infection in a patient with coccidioidal meningitis. Cutibacterium acnes infects and obstructs cerebral shunts by the production of biofilm; however, diagnosis is usually missed by routine aerobic cultures. Obtaining anaerobic cultures routinely in patients with foreign body implants leading to central nervous system infections could prevent a missed diagnosis of this pathogen. Penicillin G is the first-line treatment.

Risk factors of reinfection after prosthesis removal and antibiotic bone cement spacer implantation for the treatment of periprosthetic joint infection

BACKGROUND

Prosthesis removal and antibiotic bone cement spacer implantation is a very important link in two-stage revision of periprosthetic joint infection (PJI) after artificial joint replacement, which is key to the smooth progress of second-stage revision surgery. There are few reports on the risk factors of reinfection after prosthesis removal and antibiotic bone cement spacer implantation for PJI. This study aimed to investigate the risk factors of reinfection after prosthesis removal and antibiotic bone cement spacer implantation for the treatment of PJI.

METHODS

Clinical data of 40 patients who underwent prosthesis removal and antibiotic bone cement spacer implantation for PJI after arthroplasty in our hospital from January 2013 to July 2019 were retrospectively analyzed. During the follow-up period of at least 2 years, 21 patients underwent complete two-stage revision after the removal of the antibiotic bone cement spacer, and 19 patients did not receive a new prosthesis due to other factors, such as reinfection or the patient's wishes, record the infection control of patients during the treatment. Reinfection after prosthesis removal and antibiotic bone cement spacer implantation was defined as failure of effective control of infection, symptoms of reinfection, requires increased antibiotic therapy or reoperation. Multivariate Cox proportional hazards model was used to analyze the risk factors associated with reinfection after prosthesis removal and antibiotic bone cement spacer implantation.

RESULTS

Of the 40 patients, nine (22.5%) developed reinfection after prosthesis removal and antibiotic bone cement spacer implantation with a mean follow-up duration of 31 months, and multivariate analysis revealed that history of prior revision surgery (hazard ratio [HR] = 6.317, confidence interval [CI]: 1.495-26.700; p = 0.012) and presence of sinus tract before treatment (HR = 5.117, 95% CI: 1.199-21.828; p = 0.027) were independent risk factors for reinfection after prosthesis removal and antibiotic bone cement spacer implantation.

CONCLUSION

History of prior revision surgery and presence of sinus tract are two independent risk factors for reinfection in patients with PJI treated with prosthesis removal and antibiotic bone cement spacer implantation.

Cutibacterium acnes in shoulder surgery: a scoping review of strategies for prevention, diagnosis, and treatment

BACKGROUND

Cutibacterium acnes is a commensal, gram-positive, facultatively anaerobic bacillus that resides in the dermis. Historically thought to be a contaminant when identified on cultured specimens, recent advances in diagnostic technology have now implicated it as the most common organism responsible for postoperative shoulder infections. Despite a recognition of the role of this organism and a significant research interest in recent years, there is clear lack of consensus guideline on strategies to prevent, diagnose, and treat postoperative shoulder infection.

METHOD

The electronic databases PubMed, MEDLINE, CINAHL, Scopus, and Web of Science were searched in March 2020. All experimental and nonexperimental studies that investigate C acnes in shoulder surgery were included. Inclusion was limited to articles published after 2000 and written in English; reviews, gray literature, or abstracts were excluded. A total of 70 studies were included in this review. This scoping review was performed in accordance with the Extended Preferred Reporting Items of Systematic Reviews and Meta-Analyses Statement for Scoping Reviews (PRISMA-ScR).

RESULTS

Standard surgical prophylactic regimens such as intravenous antibiotics and topical chlorhexidine are ineffective at removing C acnes from the deep layer of the dermis, and there is a shift toward using topical benzoyl peroxide with significantly improved efficacy. An improved understanding of the bacteria has demonstrated that a prolonged culture time of up to 14 days is needed, especially in cases of established infection. Advances in diagnostics such as sonication and molecular-based testing are promising. Although usually thought to be susceptible to a broad range of antibiotics, resistance is emerging to clindamycin. An improved understanding of its ability to form a biofilm highlights the difficulty in treating an established infection.

CONCLUSION

The role of C acnes causing postoperative infection following shoulder surgery is being increasingly recognized. Strategies for prevention, diagnosis, and treatment have been outlined from both an antimicrobial and surgical perspective. A number of these strategies are emerging and require further research to demonstrate efficacy before implementation into clinical guidelines.

Cutibacterium acnes as an Opportunistic Pathogen: An Update of Its Virulence-Associated Factors

Cutibacterium acnes is a member of the skin microbiota found predominantly in regions rich in sebaceous glands. It is involved in maintaining healthy skin and has long been considered a commensal bacterium. Its involvement in various infections has led to its emergence as an opportunist pathogen. Interactions between C. acnes and the human host, including the human skin microbiota, promote the selection of C. acnes strains capable of producing several virulence factors that increase inflammatory capability. This pathogenic property may be related to many infectious mechanisms, such as an ability to form biofilms and the expression of putative virulence factors capable of triggering host immune responses or enabling C. acnes to adapt to its environment. During the past decade, many studies have identified and characterized several putative virulence factors potentially involved in the pathogenicity of this bacterium. These virulence factors are involved in bacterial attachment to target cells, polysaccharide-based biofilm synthesis, molecular structures mediating inflammation, and the enzymatic degradation of host tissues. C. acnes, like other skin-associated bacteria, can colonize various ecological niches other than skin. It produces several proteins or glycoproteins that could be considered to be active virulence factors, enabling the bacterium to adapt to the lipophilic environment of the pilosebaceous unit of the skin, but also to the various organs it colonizes. In this review, we summarize current knowledge concerning characterized C. acnes virulence factors and their possible implication in the pathogenicity of C. acnes.

Analysis of subclinical infections and biofilm formation in cases of capsular contracture after silicone augmentation rhinoplasty: Prevalence and microbiological study

Background

Implant-related deformities in aesthetic rhinoplasty are a major problem for rhinoplasty surgeons. Capsular contracture is believed to be the pathological cause of delayed contour deformities, comparable to breast implant-related contracture. This study investigated the prevalence of bacterial biofilms and other epidemiological factors related to capsular contracture in cases of silicone augmentation rhinoplasty.

Methods

Thirty-three patients who underwent corrective rhinoplasty due to a delayed contour deformity or aesthetic revision after implant rhinoplasty were studied from December 2014 to December 2016. All recruited patients received surgical correction by the authors. The patients were categorized by clinical severity into four grades. Demographic data and related confounding factors were recorded. Samples of capsular tissue and silicone removed from each patient were analyzed for the presence of a biofilm by ultrasonication with bacterial culture and scanning electron microscopy.

Results

Thirty-three paired samples of capsular tissue and silicone implants from the study group were analyzed. Biofilms were detected in one of 10 subjects (10%) with grade 1 contracture, two of four (50%) with grade 2 contracture, 10 of 14 (71.40%) with grade 3 contracture, and four of five (80%) with grade 4 contracture (P<0.05). The organisms found were Staphylococcus epidermidis (47.10%), coagulase-negative staphylococci (35.30%), and Staphylococcus aureus (17.60%).

Conclusions

As with breast implant-related capsular contracture, silicone nasal augmentation deformities likely result from bacterial biofilms. We demonstrated the prevalence of biofilms in patients with various degrees of contracture. Implant type and operative technique seemed to have only vague correlations with biofilm presence.

Studies on the Curing Efficiency and Mechanical Properties of Bis-GMA and TEGDMA Nanocomposites Containing Silver Nanoparticles

Bioactive dimethacrylate composites filled with silver nanoparticles (AgNP) might be used in medical applications, such as dental restorations and bone cements. The composition of bisphenol A glycerolate dimethacrylate (Bis-GMA) and triethylene glycol dimethacrylate (TEGDMA) mixed in a 60/40 wt% ratio was filled from 25 to 5000 ppm of AgNP. An exponential increase in resin viscosity was observed with an increase in AgNP concentration. Curing was performed by way of photopolymerization, room temperature polymerization, and thermal polymerization. The results showed that the polymerization mode determines the degree of conversion (DC), which governs the ultimate mechanical properties of nanocomposites. Thermal polymerization resulted in a higher DC than photo- and room temperature polymerizations. The DC always decreased as AgNP content increased. Flexural strength, flexural modulus, hardness, and impact strength initially increased, as AgNP concentration increased, and then decreased at higher AgNP loadings. This turning point usually occurred when the DC dropped below 65% and moved toward higher AgNP concentrations, according to the following order of polymerization methods: photopolymerization < room temperature polymerization < thermal polymerization. Water sorption (WS) was also determined. Nanocomposites revealed an average decrease of 16% in WS with respect to the neat polymer. AgNP concentration did not significantly affect WS.

The Evidence Behind Peroxide in Orthopedic Surgery

Peroxide is a strong oxidizing agent and disinfectant frequently used in orthopedic surgery. The authors conducted a systematic literature review of peroxide in orthopedic surgery, evaluating use, complications, efficacy, and appropriate concentrations. One hundred seventy-five reports were identified, with 24 being eligible for analysis. Orthopedic surgeons used peroxide for irrigation and bacterial reduction in various procedures. Complications included cytotoxicity, allergic reactions, suture damage, and inflammation. Use of the standard concentration of 3% peroxide and standard time in situ are without evidence. Laboratory studies suggest that diluted concentrations retain the benefit of bacterial decolonization without increasing the risk for complications. [Orthopedics. 2018; 41(6):e756-e764.].

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.

Rhodomyrtone inhibits lipase production, biofilm formation, and disorganizes established biofilm in Propionibacterium acnes

Virulence enzymes and biofilm a play crucial role in the pathogenesis of Propionibacterium acnes, a major causative agent of acne vulgaris. In the present study, the effects of rhodomyrtone, a pure compound identified from Rhodomyrtus tomentosa (Aiton) Hassk. leaves extract against enzyme production and biofilm formation production by 5 clinical isolates and a reference strain were evaluated. The degree of hydrolysis by both lipase and protease enzymes significantly decreased upon treatment with the compound at 0.125-0.25 μg/mL (p < 0.05). Lipolytic zones significantly reduced in all isolates while decrease in proteolytic activities was found only in 50% of the isolates. Rhodomyrtone at 1/16MIC and 1/8MIC caused significant reduction in biofilm formation of the clinical isolates (p < 0.05). Percentage viability of P. acnes within mature biofilm upon treated with the compound at 4MIC and 8MIC ranged between 40% and 85%. Pronounced properties of rhodomyrtone suggest a path towards developing a novel anti-acne agent.

Understanding the role of Propionibacterium acnes in acne vulgaris: The critical importance of skin sampling methodologies

Acne vulgaris is a chronic inflammatory skin condition classified by the Global Burden of Disease Study as the eighth most prevalent disease worldwide. The pathophysiology of the condition has been extensively studied, with an increase in sebum production, abnormal keratinization of the pilosebaceous follicle, and an inflammatory immune response all implicated in its etiology. One of the most disputed points, however, is the role of the gram-positive anaerobic bacterium Propionibacterium acnes in the development of acne, particularly when this organism is also found in normal sebaceous follicles of healthy skin. Against this background, we now describe the different sampling strategies that have been adopted for qualitative and quantitative study of P acnes within intact hair follicles of the skin and discuss the strengths and weaknesses of such methodologies for investigating the role of P acnes in the development of acne.

Enhancing Drug Release From Antibiotic-loaded Bone Cement Using Porogens

OBJECTIVE

To evaluate whether the addition of porogens to polymethyl methacrylate (PMMA) enhances the antibiotic elution rate from antibiotic-loaded bone cement.

METHODS

Two porogens, gelatin sponge (Spongostan, Ferrosan Medical Devices) and ceramic granules (Bicera, Wiltrom), were added to liquid gentamicin-loaded PMMA at increasing concentrations. Porosity was analyzed using Fourier transform infrared (FTIR) spectroscopy and scanning electron microscopy. Young's modulus and drug elution were also measured. The gentamicin content of the eluents was evaluated by o-phthaldialdehyde (OPA) assay on days 1, 2, 5, 7, 10, and 14.

RESULTS

After day 5, the drug-releasing rate of Spongostan was significantly higher than that of Bicera in the order G3 > G2 > T3 > G1 > T2 > T1 > bone cement, where G represents the concentration of Spongostan and T represents the concentration of Bicera. The addition of Bicera and Spongostan increased the drug-releasing efficiency of PMMA by 3.75-fold and 5.65-fold, respectively. Spongostan also resulted in larger pores (ie, 70 to approximately 200 μm) compared with Bicera (5 to 10 μm) but reduced biomechanical strength.

CONCLUSION

Both gelatin sponge and ceramic granules improved the local antibiotic elution rate, although the drug-releasing rate of Spongostan was significantly higher than that of Bicera.

Propionibacterium acnes: from commensal to opportunistic biofilm-associated implant pathogen. Clin Microbiol Rev. 2014;27:419-440. [PMID: 24982315 DOI: 10.1128/cmr.00092-13]

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.

Antibiotic-loaded synthetic calcium sulfate beads for prevention of bacterial colonization and biofilm formation in periprosthetic infections

Periprosthetic infection (PI) causes significant morbidity and mortality after fixation and joint arthroplasty and has been extensively linked to the formation of bacterial biofilms. Poly(methyl methacrylate) (PMMA), as a cement or as beads, is commonly used for antibiotic release to the site of infection but displays variable elution kinetics and also represents a potential nidus for infection, therefore requiring surgical removal once antibiotics have eluted. Absorbable cements have shown improved elution of a wider range of antibiotics and, crucially, complete biodegradation, but limited data exist as to their antimicrobial and antibiofilm efficacy. Synthetic calcium sulfate beads loaded with tobramycin, vancomycin, or vancomycin-tobramycin dual treatment (in a 1:0.24 [wt/wt] ratio) were assessed for their abilities to eradicate planktonic methicillin-resistant Staphylococcus aureus (MRSA) and Staphylococcus epidermidis relative to that of PMMA beads. The ability of the calcium sulfate beads to prevent biofilm formation over multiple days and to eradicate preformed biofilms was studied using a combination of viable cell counts, confocal microscopy, and scanning electron microscopy of the bead surface. Biofilm bacteria displayed a greater tolerance to the antibiotics than their planktonic counterparts. Antibiotic-loaded beads were able to kill planktonic cultures of 10(6) CFU/ml, prevent bacterial colonization, and significantly reduce biofilm formation over multiple days. However, established biofilms were harder to eradicate. These data further demonstrate the difficulty in clearing established biofilms; therefore, early preventive measures are key to reducing the risk of PI. Synthetic calcium sulfate loaded with antibiotics has the potential to reduce or eliminate biofilm formation on adjacent periprosthetic tissue and prosthesis material and, thus, to reduce the rates of periprosthetic infection.

Propionibacterium persists in the skin despite standard surgical preparation

BACKGROUND

Propionibacterium acnes, which normally resides in the skin, is known to play a role in surgical site infection in orthopaedic surgery. Studies have suggested a persistence of propionibacteria on the skin surface, with rates of positive cultures ranging from 7% to 29% after surgical preparation. However, as Propionibacterium organisms normally reside in the dermal layer, these studies may underestimate the true prevalence of propionibacteria after surgical skin preparation. We hypothesized that, after surgical skin preparation, viable Propionibacterium remains in the dermis at a much higher rate than previously reported.

METHODS

Ten healthy male volunteers underwent skin preparation of the upper back with ChloraPrep (2% chlorhexidine gluconate and 70% isopropyl alcohol). Two 3-mm dermal punch biopsy specimens were obtained through the prepared skin and specifically cultured for P. acnes.

RESULTS

Seven volunteers had positive findings for Propionibacterium on dermal cultures after ChloraPrep skin preparation. The average time to positive cultures was 6.78 days.

CONCLUSIONS

This study found that Propionibacterium persists in the dermal tissue even after surface skin preparation with ChloraPrep. The 70% rate of persistence of propionibacteria after skin preparation is substantially higher than previously reported.

CLINICAL RELEVANCE

Propionibacteria are increasingly discussed as having an association with infection, implant failure, and degenerative disease. This study confirms the possibility that the dermal layer of skin may be the source of the bacteria.

In vitro and in vivo investigation of the influence of implant surface on the formation of bacterial biofilm in mammary implants

BACKGROUND

Capsular contracture remains the most common complication following breast augmentation surgery, and evidence suggests that bacterial biofilm on the implant surface is responsible. The authors investigated whether the interaction of bacterial biofilm with implants independently determines progression to capsule formation. They also studied the rate of bacterial growth and adhesion to implants.

METHODS

Sixteen adult female pigs had 121 breast implants inserted. Sixty-six implants-23 smooth and 43 textured-were inoculated with a human strain of Staphylococcus epidermidis and received no other treatment. After an average period of 19 weeks, Baker grading was performed and implants were retrieved. For the in vitro study, samples underwent both quantitative bacterial analysis and imaging using confocal laser scanning and scanning electron microscopy.

RESULTS

At explantation, there was no significant difference (p = 1.0) in the presence of capsular contracture (Baker grade III and IV) between smooth (83 percent) and textured implants (84 percent). Biofilm was confirmed on 60 of the 66 capsules. Capsules from smooth and textured implants had the same number of infecting bacteria (textured: 3.01 × 10 bacteria/g; smooth: 3.00 × 10 bacteria/g). In vitro, the surface of textured implants showed 11-, 43-, and 72-fold more bacteria at 2, 6, and 24 hours, respectively, compared with smooth implants (p < 0.001). These findings were confirmed by imaging analysis.

CONCLUSIONS

These results show that textured implants develop a significantly higher load of bacterial biofilm in comparison with smooth implants. Furthermore, in vivo, once a threshold of biofilm forms on either smooth or textured implant surfaces, there seems to be an equal propensity to progress to capsular contracture.

Propionibacterium acnes and Staphylococcus lugdunensis cause pyogenic osteomyelitis in an intramedullary nail model in rabbits

Propionibacterium acnes and coagulase-negative staphylococci (CoNS) are opportunistic pathogens implicated in prosthetic joint and fracture fixation device-related infections. The purpose of this study was to determine whether P. acnes and the CoNS species Staphylococcus lugdunensis, isolated from an "aseptically failed" prosthetic hip joint and a united intramedullary nail-fixed tibial fracture, respectively, could cause osteomyelitis in an established implant-related osteomyelitis model in rabbits in the absence of wear debris from the implant material. The histological features of P. acnes infection in the in vivo rabbit model were consistent with localized pyogenic osteomyelitis, and a biofilm was present on all explanted intramedullary (IM) nails. The animals displayed no outward signs of infection, such as swelling, lameness, weight loss, or elevated white blood cell count. In contrast, infection with S. lugdunensis resulted in histological features consistent with both pyogenic osteomyelitis and septic arthritis, and all S. lugdunensis-infected animals displayed weight loss and an elevated white blood cell count despite biofilm detection in only two out of six rabbits. The differences in the histological and bacteriological profiles of the two species in this rabbit model of infection are reflective of their different clinical presentations: low-grade infection in the case of P. acnes and acute infection for S. lugdunensis. These results are especially important in light of the growing recognition of chronic P. acnes biofilm infections in prosthetic joint failure and nonunion of fracture fixations, which may be currently reported as "aseptic" failure.

Origin of propionibacterium in surgical wounds and evidence-based approach for culturing propionibacterium from surgical sites

BACKGROUND

To explore the origin of Propionibacterium in surgical wounds and to suggest an optimized strategy for culturing this organism at the time of revision surgery, we studied the presence of this organism on the skin and in the surgical wounds of patients who underwent revision arthroplasty for reasons other than apparent infection.

METHODS

Specimens were cultured in broth and on aerobic and anaerobic media. The presence and degree of positivity of Propionibacterium cultures were correlated with sex. The results of dermal and deep cultures were correlated. Times to positivity and the yields of each media type and specimen source were investigated.

RESULTS

Propionibacterium grew in twenty-three of thirty cultures of specimens obtained preoperatively from the unprepared epidermis over the area where a skin incision was going to be made for a shoulder arthroplasty; males had a greater average degree of positivity than females (p &lt; 0.002). Twelve of twenty-one male subjects and zero of twenty female subjects who had cultures of dermal specimens obtained during revision shoulder arthroplasty had positive findings for Propionibacterium (p = 0.0001). Twelve of twenty male subjects and only one of twenty female subjects had positive deep cultures (p = 0.0004). The positivity of dermal cultures for Propionibacterium was significantly associated with the positivity of deep cultures for this organism (p = 0.0001). If Propionibacterium was present in deep tissues, it was likely that it would be recovered by culture if four different specimens were obtained and cultured for a minimum of seventeen days on three different media: aerobic, anaerobic, and broth.

CONCLUSIONS

Because the surgical incision of dermal sebaceous glands may be a source of Propionibacterium in deep wounds, strategies for minimizing the risk of Propionibacterium infections may need to be directed at minimizing the contamination of surgical wounds from these bacteria residing in rather than on the skin. Obtaining at least four specimens, observing them for seventeen days, and using three types of culture media optimize the recovery of Propionibacterium at the time of revision surgery.

Intercellular adhesion molecule-1 (ICAM-1, CD54) is increased in adhesive capsulitis

BACKGROUND

The purpose of this study was to investigate the presence of intercellular adhesion molecule-1 (ICAM-1) in shoulders with adhesive capsulitis ("frozen shoulder").

METHODS

Glenohumeral capsular tissue was obtained from twenty-six patients (seventeen with adhesive capsulitis and nine controls), and ICAM-1 was evaluated with use of oligonucleotide arrays, real-time reverse transcription-polymerase chain reaction (RT-PCR), and immunohistochemistry. ICAM-1 was also evaluated in synovial fluid with use of western blotting (six patients with adhesive capsulitis and two controls) and in peripheral blood with use of an enzyme-linked immunosorbent assay (ELISA) (thirty-two patients with adhesive capsulitis, twenty with diabetes mellitus, and fourteen controls). The effect of ICAM-1 treatment on gene expression of cytokines related to inflammation and fibrosis was evaluated in cultured normal human synovial cells.

RESULTS

The level of ICAM-1 was significantly greater in capsular tissue from the glenohumeral joint of patients with adhesive capsulitis compared with controls as measured by oligonucleotide array analysis (0.12 ± 0.01 compared with 0.09 ± 0.00 arbitrary units) (p = 0.001), real-time RT-PCR (1.70 ± 0.19 compared with 0.67 ± 0.24 arbitrary units) (p < 0.05), and immunohistochemical staining. ICAM-1 was also significantly increased in the synovial fluid of patients with adhesive capsulitis (1.70 ± 0.18 arbitrary units) compared with normal controls (0.48 ± 0.17) (p < 0.05) and in serum of patients with adhesive capsulitis (633.22 ± 59.14 ng/mL) and patients with diabetes mellitus (671.25 ± 27.08 ng/mL) compared with controls (359.86 ± 44.29 ng/mL) (p < 0.05). Gene expression of cytokines related to inflammation and fibrosis in synoviocytes cultured in vitro was greater after three days of treatment with ICAM-1 and with ICAM-1 with glucose compared with untreated cells.

CONCLUSIONS

ICAM-1 was increased in patients with adhesive capsulitis, similar to the increase that has been reported in patients with diabetes mellitus.

Reducing Staphylococcus aureus biofilm formation on stainless steel 316L using functionalized self-assembled monolayers

Stainless steel 316L (SS316L) is a common material used in orthopedic implants. Bacterial colonization of the surface and subsequent biofilm development can lead to refractory infection of the implant. Since the greatest risk of infection occurs perioperatively, strategies that reduce bacterial adhesion during this time are important. As a strategy to limit bacterial adhesion and biofilm formation on SS316L, self-assembled monolayers (SAMs) were used to modify the SS316L surface. SAMs with long alkyl chains terminated with hydrophobic (-CH3) or hydrophilic (oligoethylene glycol) tail groups were used to form coatings and in an orthogonal approach, SAMs were used to immobilize gentamicin or vancomycin on SS316L for the first time to form an "active" antimicrobial coating to inhibit early biofilm development. Modified SS316L surfaces were characterized using surface infrared spectroscopy, contact angles, MALDI-TOF mass spectrometry and atomic force microscopy. The ability of SAM-modified SS316L to retard biofilm development by Staphylococcus aureus was functionally tested using confocal scanning laser microscopy with COMSTAT image analysis, scanning electron microscopy and colony forming unit analysis. Neither hydrophobic nor hydrophilic SAMs reduced biofilm development. However, gentamicin-linked and vancomycin-linked SAMs significantly reduced S. aureus biofilm formation for up to 24 and 48 h, respectively.

Daptomycin: local application in implant-associated infection and complicated osteomyelitis

BACKGROUND

The rise of highly resistant bacteria creates a persistent urge to develop new antimicrobial agents. This paper investigates the application of the lipopeptide antibiotic daptomycin in infections involving the human bone.

METHODS

Compressive and tensile strength testing of daptomycin-laden PMMA was performed referring to the ISO 5833. The microstructure of the antibiotic-laden PMMA was evaluated by scanning electron microscopy. Intracellular activity of daptomycin was determined by a human osteoblast infection model. Elution kinetics of the antibiotic-laden bone cement was measured by using a continuous flow chamber setup.

RESULTS

There was no significant negative effect of adding 1.225% and 7.5% per weight of daptomycin to the PMMA. There was no significant difference in intracellular activity comparing gentamicin to daptomycin. Elution of daptomycin from PMMA showed within the first-hour initial peak values of 15-20 μg/mL.

CONCLUSION

Daptomycin has a certain degree of activity in the intracellular environment of osteoblasts. Daptomycin admixed to PMMA remains bactericidal and does not significantly impair structural characteristics of the PMMA. The results of this paper suggest that daptomycin might be a potent alternative for treating osteomyelitis and implant-associated infection in trauma and orthopedic surgery caused by multiresistant strains.

Antibacterial efficacy of a new gentamicin-coating for cementless prostheses compared to gentamicin-loaded bone cement

Cementless prostheses are increasingly popular but require alternative prophylactic measures than the use of antibiotic-loaded bone cements. Here, we determine the 24-h growth inhibition of gentamicin-releasing coatings from grit-blasted and porous-coated titanium alloys, and compare their antibacterial efficacies and gentamicin release-profiles to those of a commercially available gentamicin-loaded bone cement. Antibacterial efficacy increased with increasing doses of gentamicin in the coating and loading with 1.0 and 0.1 mg gentamicin/cm(2) on both grit-blasted and porous-coated samples yielded comparable efficacy to gentamicin-loaded bone cement. The coating had a higher burst release than bone cement, and also inhibited growth of gentamicin-resistant strains. Antibacterial efficacy of the gentamicin coatings disappeared after 4 days, while gentamicin-loaded bone cement exhibited efficacy over at least 7 days. Shut-down after 4 days of gentamicin-release from coatings is advantageous over the low-dosage tail-release from bone cements, as it minimizing risk of inducing antibiotic-resistant strains. Both gentamicin-loaded cement discs and gentamicin-coated titanium coupons were able to kill gentamicin-sensitive and -resistant bacteria in a simulated prothesis-related interfacial gap. In conclusion, the gentamicin coating provided similar antibacterial properties to those seen by gentamicin-loaded bone cement, implying protection of a prosthesis from being colonized by peri-operatively introduced bacteria in cementless total joint arthroplasty.

Impact of nanoscale topography on genomics and proteomics of adherent bacteria

Bacterial adhesion onto inorganic/nanoengineered surfaces is a key issue in biotechnology and medicine, because it is one of the first necessary steps to determine a general pathogenic event. Understanding the molecular mechanisms of bacteria-surface interaction represents a milestone for planning a new generation of devices with unanimously certified antibacterial characteristics. Here, we show how highly controlled nanostructured substrates impact the bacterial behavior in terms of morphological, genomic, and proteomic response. We observed by atomic force microscopy (AFM) and scanning electron microscopy (SEM) that type-1 fimbriae typically disappear in Escherichia coli adherent onto nanostructured substrates, as opposed to bacteria onto reference glass or flat gold surfaces. A genetic variation of the fimbrial operon regulation was consistently identified by real time qPCR in bacteria interacting with the nanorough substrates. To gain a deeper insight into the molecular basis of the interaction mechanisms, we explored the entire proteomic profile of E. coli by 2D-DIGE, finding significant changes in the bacteria adherent onto the nanorough substrates, such as regulations of proteins involved in stress processes and defense mechanisms. We thus demonstrated that a pure physical stimulus, that is, a nanoscale variation of surface topography, may play per se a significant role in determining the morphological, genetic, and proteomic profile of bacteria. These data suggest that in depth investigations of the molecular processes of microorganisms adhering to surfaces are of great importance for the design of innovative biomaterials with active biological functionalities.

Risk factors for revision due to infection after primary total hip arthroplasty. A population-based study of 80,756 primary procedures in the Danish Hip Arthroplasty Registry

BACKGROUND AND PURPOSE

There has been a limited amount of research on risk factors for revision due to infection following total hip arthroplasty (THA), probably due to low absolute numbers of revisions. We therefore studied patient- and surgery-related risk factors for revision due to infection after primary THA in a population-based setting.

MATERIALS AND METHODS

Using the Danish Hip Arthroplasty Registry, we identified 80,756 primary THAs performed in Denmark between Jan 1, 1995 and Dec 31, 2008. We used Cox regression analysis to compute crude and adjusted relative risk (RR) of revision due to infection. Revision was defined as extraction or exchange of any component due to infection. The median follow-up time was 5 (0–14) years.

RESULTS

597 primary THAs (0.7%) were revised due to infection. Males, patients with any co-morbidity, patients operated due to non-traumatic avascular femoral head necrosis, and patients with long duration of surgery had an increased RR of revision due to infection within the total follow-up time. A tendency of increased RR of revision was found for patients who had received cemented THA without antibiotic and hybrid THA relative to patients with cementless implants. Hip diagnosis and fixation technique were not associated with risk of revision due to infection within 1 year of surgery (short-term risk).

INTERPRETATION

We identified several categories of THA patients who had a higher risk of revision due to infection. Further research is required to explain the mechanism underlying this increased risk. More attention should be paid by clinicians to infection prevention strategies in patients with THA, particularly those with increased risk.

A biofilm approach to detect bacteria on removed spinal implants

STUDY DESIGN

This is a prospective study comparing the diagnosis of spinal implant infection by conventional peri-implant tissue culture with a technique which uses a combination of vortexing and bath sonication to dislodge bacteria growing as a biofilm on the surface of retrieved spinal implants.

OBJECTIVE

We hypothesized that the biofilm-sampling technique would be more sensitive than peri-implant tissue culture.

SUMMARY OF BACKGROUND DATA

Culture of peri-implant tissue is inaccurate for the diagnosis of orthopedic device-related infection; cultures taken from the implant may be more sensitive. We have developed a technique which uses vortexing-bath sonication to sample bacterial biofilms on the surface of retrieved hip and knee implants, and shown that it is more sensitive than peri-prosthetic tissue culture for the microbiologic diagnosis of prosthetic knee, hip, and shoulder infection.

METHODS

We compared peri-implant tissue culture to the vortexing-bath sonication technique which samples bacterial biofilm on the surface of retrieved spinal implants, for the diagnosis of spinal implant infection. In addition, we compared detection of Staphylococcus and Propionibacterium acnes by rapid cycle real-time polymerase chain reaction with culture of sonicate fluid.

RESULTS

A total of 112 subjects were studied; 22 had spinal implant infection. The sensitivities of peri-implant tissue and sonicate fluid culture were 73% and 91% (P = 0.046), and the specificities were 93% and 97%, respectively. P. acnes and coagulase-negative staphylococci were the most frequent microorganisms detected among subjects with spinal implant infection, with P. acnes detected in 56 and 45%, and coagulase-negative staphylococci detected in 31 and 40% of peri-implant tissue and sonicate fluid cultures, respectively. Compared with the culture of sonicate fluid, polymerase chain reaction was 100 and 67% sensitive for the detection of culture-positive Staphylococcus and P. acnes spinal implant infection, respectively.

CONCLUSION

Implant sonication followed by culture is more sensitive than peri-implant tissue culture for the microbiologic diagnosis of spinal implant infection.

Propionibacterium acnes as an etiological agent of arthroplastic and osteosynthetic infections--two cases with specific clinical presentation including formation of draining fistulae

This report describes two patients with orthopaedic implant infections, with specific clinical presentations including formation of draining fistulae. Propionibacterium acnes was isolated in multiple cultures in both cases. Phenotypic and genetic characterisation of the isolates clearly emphasizes the significance of P. acnes as an etiological agent of implant infections. These infections are insidious with delayed presentation of symptoms and may have been overlooked because of the consideration of P. acnes as a contaminating commensal as well as the frequent use of suboptimal culture procedures.

Rationale for one stage exchange of infected hip replacement using uncemented implants and antibiotic impregnated bone graft

Infection of a total hip replacement (THR) is considered a devastating complication, necessitating its complete removal and thorough debridement of the site. It is undoubted that one stage exchange, if successful, would provide the best benefit both for the patient and the society. Still the fear of re-infection dominates the surgeons decisions and in the majority of cases directs them to multiple stage protocols. However, there is no scientifically based argument for that practice. Successful eradication of infection with two stage procedures is reported to average 80% to 98%. On the other hand a literature review of Jackson and Schmalzried (CORR 2000) summarizing the results of 1,299 infected hip replacements treated with direct exchange (almost exclusively using antibiotic loaded cement), reports of 1,077 (83%) having been successful. The comparable results suggest, that the major factor for a successful outcome with traditional approaches may be found in the quality of surgical debridement and dead space management. Failures in all protocols seem to be caused by small fragments of bacterial colonies remaining after debridement, whereas neither systemic antibiotics nor antibiotic loaded bone cement (PMMA) have been able to improve the situation significantly. Reasons for failure may be found in the limited sensitivity of traditional bacterial culturing and reduced antibiotic susceptibility of involved pathogens, especially considering biofilm formation. Whenever a new prosthesis is implanted into a previously infected site the surgeon must be aware of increased risk of failure, both in single or two stage revisions. Eventual removal therefore should be easy with low risk of additional damage to the bony substance. On the other hand it should also have potential of a good long term result in case of success. Cemented revisions generally show inferior long term results compared to uncemented techniques; the addition of antibiotics to cement reduces its biomechanical properties. Efficient cementing techniques will result in tight bonding with the underlying bone, making eventual removal time consuming and possibly associated with further damage to the osseous structures. All these issues are likely to make uncemented revisions more desirable. Allograft bone may be impregnated with high loads of antibiotics using special incubation techniques. The storage capacities and pharmacological kinetics of the resulting antibiotic bone compound (ABC) are more advantageous than the ones of antibiotic loaded cement. ABC provides local concentrations exceeding those of cement by more than a 100fold and efficient release is prolonged for several weeks. The same time they are likely to restore bone stock, which usually is compromised after removal of an infected endoprosthesis. ABC may be combined with uncemented implants for improved long term results and easy removal in case of a failure. Specifications of appropriate designs are outlined. Based on these considerations new protocols for one stage exchange of infected TJR have been established. Bone voids surrounding the implants may be filled with antibiotic impregnated bone graft; uncemented implants may be fixed in original bone. Recent studies indicate an overall success rate of more than 90% without any adverse side effects. Incorporation of allografts appears as after grafting with unimpregnated bone grafts. Antibiotic loaded bone graft seems to provide sufficient local antibiosis for protection against colonisation of uncemented implants, the eluted amounts of antibiotics are likely to eliminate biofilm remnants, dead space management is more complete and defects may be reconstructed efficiently. Uncemented implants provide improved long term results in case of success and facilitated re-revision in case of failure. One stage revision using ABC together with uncemented implants such should be at least comparably save as multiple stage procedures, taking advantage of the obvious benefits for patients and economy.

Biofilm formation by Propionibacterium acnes is a characteristic of invasive isolates

Propionibacterium acnes is a common and probably underestimated cause of delayed joint prosthesis infection. Bacterial biofilm formation is central in the pathogenesis of infections related to foreign material, and P. acnes has been shown to form biofilm both in vitro and in vivo. Here, biofilm formation by 93 P. acnes isolates, either from invasive infections (n = 45) or from the skin of healthy people (n = 48), was analysed. The majority of isolates from deep infections produced biofilm in a microtitre model of biofilm formation, whereas the skin isolates were poor biofilm producers (p <0.001 for a difference). This indicates a role for biofilm formation in P. acnes virulence. The type distribution, as determined by sequencing of recA, was similar among isolates isolated from skin and from deep infections, demonstrating that P. acnes isolates with different genetic backgrounds have pathogenic potential. The biofilm formed on plastic and on bone cement was analysed by scanning electron microscopy (EM) and by transmission EM. The biofilm was seen as a 10-mum-thick layer covering the bacteria and was composed of filamentous as well as more amorphous structures. Interestingly, the presence of human plasma in solution or at the plastic surface inhibits biofilm formation, which could explain why P. acnes primarily infect plasma-poor environments of, for example, joint prostheses and cerebrospinal shunts. This work underlines the importance of biofilm formation in P. acnes pathogenesis, and shows that biofilm formation should be considered in the diagnosis and treatment of invasive P. acnes infections.

Prevalence of genes for aminoglycoside-modifying enzymes in Staphylococcus epidermidis isolates from orthopedic postsurgical and implant-related infections

Staphylococcus epidermidis, a main etiologic agent of implant-related infections, is showing increasing resistance to several antibiotic substances, among them the aminoglycosides, a class of drugs playing a relevant role in current medical protocols to prevent and treat clinical infections. Here we investigated the prevalence of aac(6')-Ie-aph(2''), aph(3')-IIIa, and ant(4') genes, encoding for the three forms of aminoglycoside-modifying enzymes (AME), responsible for resistance to aminoglycoside antibiotics, in 70 clinical isolates of S. epidermidis from orthopedic postsurgical and implant-related infections. In addition, ermA and ermC, the two most common staphylococcal genes conferring antibiotic resistance to macrolides, lincosamides, and streptogramin B (MLS(B)) were included in this investigation. All isolates were characterized by automated ribotyping, so that the presence of antibiotic resistance determinants was investigated in strains exhibiting different ribopatterns. Interestingly, combinations of coexisting AME genes appeared to be typical of specific ribopatterns. The aac(6')-Ie-aph(2'') gene was the most prevalent AME gene, being observed in 44% of the isolates. As far as the determinants for MLS(B) antibiotics are concerned, the ermC gene was observed in 33% of the isolates, while ermA was detected in a single isolate. These results provide a detailed characterization in terms of antibiotic resistance determinants of clones of S. epidermidis frequently isolated from implant orthopedic infections, providing useful indications for more effectual future strategies of infection prevention/eradication based on the incorporation of antibiotic drugs in biomaterials.

In vitro testing of chitosan in gentamicin-loaded bone cement: no antimicrobial effect and reduced mechanical performance

BACKGROUND AND PURPOSE

Efforts to prevent infection of arthroplasties, including the use of antibiotic-loaded bone cement, are not always successful. We investigated whether the incorporation of chitosan in gentamicin-loaded bone cement increases antibiotic release, and prevents bacterial adherence and biofilm formation by clinical isolates of Staphylococcus spp. In addition, we performed mechanical and degradation tests.

METHODS

Different amounts of chitosan were added to the powder of the gentamicin-loaded bone cement. Gentamicin release was determined using high-per-formance liquid chromatography mass spectrometry. Bacterial adherence and bacterial biofilm formation were determined using clinical isolates cultured from implants retrieved at revision hip surgery. The mechanical properties were determined as a function of degradation in accordance with ISO and ASTM standards for PMMA bone cement.

RESULTS

The addition of chitosan to bone cement loaded with gentamicin reduced gentamicin release and did not increase the efficacy of the bone cement in preventing bacterial colonization and biofilm formation. Moreover, the mechanical performance of cement containing chitosan was reduced after 28 days of degradation. The compressive and bending strengths were not in compliance with the minimum ISO and ASTM requirements.

INTERPRETATION

Clinically, incorporation of chitosan into gentamicin-loaded bone cement for use in joint replacement surgery has no antimicrobial benefit and the detrimental effect on mechanical properties may have an adverse effect on the longevity of the prosthetic joint.

Copal bone cement is more effective in preventing biofilm formation than Palacos R-G

Bone cements loaded with combinations of antibiotics are assumed more effective in preventing infection than bone cements with gentamicin as a single drug. Moreover, loading with an additional antibiotic may increase interconnectivity between antibiotic particles to enhance release. We hypothesize addition of clindamycin to a gentamicin-loaded cement yields higher antibiotic release and causes larger inhibition zones against clinical isolates grown on agar and stronger biofilm inhibition. Antibiotic release after 672 hours from Copal bone cement was more extensive (65% of the clindamycin and 41% of the gentamicin incorporated) than from Palacos R-G (4% of the gentamicin incorporated). The higher antibiotic release from Copal resulted in a stronger and more prolonged inhibition of bacterial growth on agar. Bacterial colony counting and confocal laser scanning microscopy of biofilms grown on the bone cements suggest antibiotic release reduced bacterial viability, most notably close to the cement surface. The gentamicin-sensitive Staphylococcus aureus formed gentamicin-resistant small colony variants on Palacos R-G and therefore Copal more effectively decreased biofilm formation than Palacos R-G.

Influence of surface sub-micropattern on the adhesion of pioneer bacteria on metals

Most of the implantable medical devices are prone to infection caused by microorganisms that form biofilms. Pseudomonads are frequently used as model species for studying bacterial adhesion. The initial stages of biofilm formation are influenced by different factors including, among others, the chemistry of the surface, the roughness, and topography. The aim of this work was to assess the early stages of Pseudomonas fluorescens biofilm formation on sub-microstructured surfaces (SMS) that are in tune with bacterial size. Copper and gold were used as the substrata. It was concluded that SMS influenced bacterial length, alignment, and distribution, whereas the chemistry of the surfaces affected bacterial length and distribution. However, the effect of the SMS was the most significant. The shape of the bacterial colonies and the polymeric substances production were also influenced by SMS and the chemistry of the surface and both factors may be considered to reduce the susceptibility of a surface to biofilm formation.

Incorporation of large amounts of gentamicin sulphate into acrylic bone cement: Effect on handling and mechanical properties, antibiotic release, and biofilm formation

Bacterial infection remains a significant complication following total joint replacement. If infection is suspected when revision surgery is being performed, a large dose of antibiotic, usually gentamicin sulphate, is often blended with the acrylic bone cement powder in an attempt to reduce the risk of recurrent infection. In this in-vitro study the effect of small and large doses of gentamicin sulphate on the handling and mechanical properties of the cement, gentamicin release from the cement, and in-vitro biofilm formation by clinical Staphylococcus spp. isolates on the cement was determined. An increase in gentamicin loading of 1, 2, 3, or 4 g, in a cement powder mass of 40 g, resulted in a significant decrease in the compressive and four-point bending strength, but a significant increase in the amount of gentamicin released over a 72 h period. When overt infection was modelled, using Staphylococcus spp. clinical isolates at an inoculum of 1×107 colony-forming units/ml, an increase in the amount of gentamicin (1, 2, 3, or 4 g) added to 40 g of poly(methyl methacrylate) cement resulted in an initial decrease in bacterial colonization but this beneficial effect was no longer apparent by 72 h, with the bacterial strains forming biofilms on the cements despite the release of high levels of gentamicin. The findings suggest that orthopaedic surgeons should carefully consider the clinical consequences of blending large doses (1 g or more per 40 g of poly(methyl methacrylate)) of gentamicin into Palacos® R bone cement for use in revision surgery as the increased gentamicin loading does not prevent bacterial biofilm formation and the effect on the mechanical properties could be important to the longevity of the prosthetic joint.

Incorporation of chitosan in acrylic bone cement: effect on antibiotic release, bacterial biofilm formation and mechanical properties

Bacterial infection remains a significant problem following total joint replacement. Efforts to prevent recurrent implant infection, including the use of antibiotic-loaded bone cement for implant fixation at the time of revision surgery, are not always successful. In this in vitro study, we investigated whether the addition of chitosan to gentamicin-loaded Palacos R bone cement increased antibiotic release and prevented bacterial adherence and biofilm formation by Staphylococcus spp. clinical isolates. Furthermore, mechanical tests were performed as a function of time post-polymerisation in pseudo-physiological conditions. The addition of chitosan to gentamicin-loaded Palacos R bone cement significantly decreased gentamicin release and did not increase the efficacy of the bone cement at preventing bacterial colonisation and biofilm formation. Moreover, the mechanical performance of cement containing chitosan was significantly reduced after 28 days of saline degradation with the compressive and bending strengths not in compliance with the minimum requirements as stipulated by the ISO standard for PMMA bone cement. Therefore, incorporating chitosan into gentamicin-loaded Palacos R bone cement for use in revision surgery has no clinical antimicrobial benefit and the detrimental effect on mechanical properties could adversely affect the longevity of the prosthetic joint.

Nano/microscale order affects the early stages of biofilm formation on metal surfaces

The adhesion of Pseudomonas fluorescens was studied on nano/microengineered surfaces. Results show that these bacteria formed well-defined aggregates on randomly oriented nanosized granular gold substrates. These aggregates consist of aligned ensembles of bacteria, with some of them strongly elongated. This kind of biological structure was not found on ordered engineered surfaces because bacterial alignment and cell-to-cell sticking were hindered. Importantly, differences in cell morphology, length, orientation, and flagellation were observed between bacteria attached on the ordered nano/microstructures and the randomly ordered surfaces. The implications of the results are related to the design of engineered surfaces to enhance (nanostructured filters) or inhibit (medical implants and industrial biofouling) bacterial colonization on the surfaces and to the biocontrol of soil ecosystems.