Cause Of Prosthetic Joint Infection Research Articles

Diagnostic Performance of a Molecular Assay in Synovial Fluid Targeting Dominant Prosthetic Joint Infection Pathogens.

Prosthetic joint infection (PJI) is one of the most serious complications of joint replacement surgery among orthopedic surgeries and occurs in 1 to 2% of primary surgeries. Additionally, the cause of PJIs is mostly bacteria from the Staphylococcus species, accounting for more than 98%, while fungi cause PJIs in only 1 to 2% of cases and can be difficult to manage. The current gold-standard microbiological method of culturing synovial fluid is time-consuming and produces false-negative and -positive results. This study aimed to identify a novel, accurate, and convenient molecular diagnostic method. The DreamDX primer-hydrolysis probe set was designed for the pan-bacterial and pan-fungal detection of DNA from pathogens that cause PJIs. The sensitivity and specificity of DreamDX primer-hydrolysis probes were 88.89% (95% CI, 56.50-99.43%) and 97.62% (95% CI, 87.68-99.88%), respectively, compared with the microbiological method of culturing synovial fluid, and receiver operating characteristic (ROC) area under the curve (AUC) was 0.9974 (*** p < 0.0001). It could be concluded that the DreamDX primer-hydrolysis probes have outstanding potential as a molecular diagnostic method for identifying the causative agents of PJIs, and that host inflammatory markers are useful as adjuvants in the diagnosis of PJIs.

Completed genome and emergence scenario of the multidrug-resistant nosocomial pathogen Staphylococcus epidermidis ST215

BackgroundA multidrug-resistant lineage of Staphylococcus epidermidis named ST215 is a common cause of prosthetic joint infections and other deep surgical site infections in Northern Europe, but is not present elsewhere. The increasing resistance among S. epidermidis strains is a global concern. We used whole-genome sequencing to characterize ST215 from healthcare settings.ResultsWe completed the genome of a ST215 isolate from a Swedish hospital using short and long reads, resulting in a circular 2,676,787 bp chromosome and a 2,326 bp plasmid. The new ST215 genome was placed in phylogenetic context using 1,361 finished public S. epidermidis reference genomes. We generated 10 additional short-read ST215 genomes and 11 short-read genomes of ST2, which is another common multidrug-resistant lineage at the same hospital. We studied recombination’s role in the evolution of ST2 and ST215, and found multiple recombination events averaging 30–50 kb. By comparing the results of antimicrobial susceptibility testing for 31 antimicrobial drugs with the genome content encoding antimicrobial resistance in the ST215 and ST2 isolates, we found highly similar resistance traits between the isolates, with 22 resistance genes being shared between all the ST215 and ST2 genomes. The ST215 genome contained 29 genes that were historically identified as virulence genes of S. epidermidis ST2. We established that in the nucleotide sequence stretches identified as recombination events, virulence genes were overrepresented in ST215, while antibiotic resistance genes were overrepresented in ST2.ConclusionsThis study features the extensive antibiotic resistance and virulence gene content in ST215 genomes. ST215 and ST2 lineages have similarly evolved, acquiring resistance and virulence through genomic recombination. The results highlight the threat of new multidrug-resistant S. epidermidis lineages emerging in healthcare settings.

Outcomes in orthopedic device infections due to Streptococcus agalactiae: a retrospective cohort study

BackgroundGroup B streptococci (Streptococcus agalactiae) (GBS) is a rare cause of prosthetic joint infection (PJI) occurring in patients with comorbidities and seems to be associated with a poor outcome. Depiction of GBS PJI is scarce in the literature.MethodsA retrospective survey in 2 referral centers for bone joint infections was done Patients with a history of PJI associated with GBS between 2014 and 2019 were included. A descriptive analysis of treatment failure was done. Risk factors of treatment failure were assessed.ResultsWe included 61 patients. Among them, 41 had monomicrobial (67%) infections. The median duration of follow-up was 2 years (interquartile range 2.35) Hypertension, obesity, and diabetes mellitus were the most reported comorbidities (49%, 50%, and 36% respectively). Death was observed in 6 individuals (10%) during the initial management. The rate of success was 63% (26/41). Removal of the material was not associated with remission (p = 0.5). We did not find a specific antibiotic regimen associated with a better outcome.ConclusionThe results show that S. agalactiae PJIs are associated with high rates of comorbidities and a high treatment failure rate with no optimal treatment so far.

Cutibacterium avidum: A Potent and Underestimated Pathogen in Prosthetic Hip Joint Infections.

Cutibacterium avidum has recently been reported as a rare cause of prosthetic joint infections (PJIs), contrary to Cutibacterium acnes, which is well established as a cause of PJIs, especially in shoulder arthroplasties. Two specific risk factors for PJI due to C. avidum have been reported: obesity and the skin incision approach. Here, we report four cases of hip PJIs caused by C. avidum admitted over a 30-month period at a single center. Whole-genome sequencing revealed that the four C. avidum strains were all individual strains and did not originate from a common source, such as an outbreak. Antibiotic susceptibility tests showed that the isolates were fully susceptible, and none carried known antibiotic resistance genes. In conclusion, the occurrence of four cases of PJI caused by C. avidum over a limited time at a single center may indicate that this pathogen is underestimated and is either emerging or more common than previously recognized. The patients presented overt signs of infection during surgery, indicating that C. avidum is a virulent pathogen. None of the previously reported risk factors for C. avidum PJI applied to these patients as only one was obese and none were operated on using a direct anterior skin incision approach.

980. Enterobacter: An Early-Onset Pathogen of Prosthetic Hip and Knee Infections with Poor Prognoses

Abstract Background Enterobacter sp. is a gram-negative, often drug-resistant bacillus that is classically identified from mucosal surfaces, such as pulmonary or urinary tracts. Despite its virulence, Enterobacter represents a less common pathogen in prosthetic joint infections (PJI). This study aims to resolve the current paucity of described clinical characteristics and treatment success of Enterobacter PJI. Methods Thirty-three patients with Enterobacter aerogenes-, cloaecae/asburiae-, or hormachei-positive PJIs were identified at a single institution. Infection clearance was defined as absence of infection or repeat surgery at one year and off all adjunct antibiotic therapy. Patient demographics, PJI characteristics, treatments, and clinical outcomes were compared between patients with and without clearance. Results In this cohort, mean age was 66.8 years (SD: 11.6), mean BMI was 31.0 (SD: 7.1), and mean Elixhauser Comorbidity Score was 9.1 (SD: 4.5). 54.5% had a prior PJI in the same joint, and 87.9% had more than one prior surgery in that joint. Median time of PJI diagnosis after surgery was 22 days [IQR: 18-60]. Patients initially treated with debridement antibiotics and implant retention (n=11) had a 45.5% clearance rate, compared to 23.1% for 2-stage exchange (n=13) and 44.4% for those requiring resection arthroplasty or amputation (n=9). With a median follow-up of 2.9 years, final joint outcomes included resection arthroplasty in 9 (27.3%), above-knee amputation in 7 (21.2%), definitive treatment with an articulating spacer in 6 (18.2%), and arthrodesis in 2 (6.1%) patients. Conclusion Enterobacter PJI often presents acutely and is a difficult pathogen to treat. The outcomes of our cohort reflect the virulence of Enterobacter, with high rates of failure and ultimate joint- or limb-sacrificing procedure. Despite being a less common cause of PJI, prognosis is exceptionally poor with traditional treatment algorithms when compared to historical cohorts of more common pathogens. Disclosures William A. Jiranek, MD, Biomech Holdings LLC: Stocks/Bonds|DePuy, A Johnson &amp; Johnson Company: IP royalties Thorsten M. Seyler, MD, PhD, Heraeus: Paid consultant|Pattern Health: IP royalties|Restor3d: IP royalties|Smith &amp; Nephew: Paid consultant|Total Joint Orthopedics: Paid consultant|Zimmer: research.

Functional analysis of intergenic regulatory regions of genes encoding surface adhesins in Staphylococcus aureus isolates from periprosthetic joint infections

Staphylococcus aureus is a leading cause of prosthetic joint infections (PJI). Surface adhesins play an important role in the primary attachment to plasma proteins that coat the surface of prosthetic devices after implantation. Previous efforts to identify a genetic component of the bacterium that confers an enhanced capacity to cause PJI have focused on gene content, kmers, or single-nucleotide polymorphisms (SNPs) in coding sequences. Here, using a collection of S. aureus strains isolated from PJI and wounds, we investigated whether genetic variations in the regulatory region of genes encoding surface adhesins lead to differences in their expression levels and modulate the capacity of S. aureus to colonize implanted prosthetic devices. The data revealed that S. aureus isolates from the same clonal complex (CC) contain a specific pattern of SNPs in the regulatory region of genes encoding surface adhesins. As a consequence, each clonal lineage shows a specific profile of surface proteins expression. Co-infection experiments with representative isolates of the most prevalent CCs demonstrated that some lineages have a higher capacity to colonize implanted catheters in a murine infection model, which correlated with a greater ability to form a biofilm on coated surfaces with plasma proteins. Together, results indicate that differences in the expression level of surface adhesins may modulate the propensity of S. aureus strains to cause PJI. Given the high conservation of surface proteins among staphylococci, our work lays the framework for investigating how diversification at intergenic regulatory regions affects the capacity of S. aureus to colonize the surface of medical implants.

Prosthetic Joint Infection due to Histoplasma capsulatum in a Patient from Trinidad: Workup, Pathology, and Treatment

Histoplasma capsulatum is a rarely reported cause of prosthetic joint infections. This current case report is of a patient from Trinidad, with a history of a right total knee replacement (TKR), who underwent a successful two-stage revision due to a Histoplasmosis capsulatum periprosthetic joint infection (PJI). This case report offers a unique treatment plan to successfully treat Histoplasmosis capsulatum periprosthetic joint infections and emphasizes the importance of obtaining an accurate travel history.

Comparative In Vitro Study of Biofilm Formation and Antimicrobial Susceptibility in Gram-Negative Bacilli Isolated from Prosthetic Joint Infections.

ABSTRACTProsthetic joint infections (PJIs) are typically caused by microorganisms that grow in biofilms. Traditional antimicrobial susceptibility tests are based on the study of planktonic bacteria that might lead to missing the biofilm behavior and to a treatment failure. This study was designed to analyze the antimicrobial susceptibility of clinical Gram-negative bacilli (GNB) isolates from PJIs in planktonic and sessile states and the possible relationship between antimicrobial resistance and biofilm formation. A total of 46 clinical isolates from patients with PJIs (mainly hip and knee prostheses) plus three GNB ATCC isolates were studied. The Minimal Inhibitory Concentration (MIC), minimal bactericidal concentration (MBC), minimal biofilm inhibitory concentration (MBIC), and minimal biofilm eradication concentration (MBEC) were assessed using a previously published methodology. Almost all of the GNB clinical isolates tested were biofilm forming. Pseudomonas aeruginosa was the largest biofilm-forming species. A comparison of MBIC90 versus MIC90 shows an increase higher than 1- to -2-fold dilutions in most antimicrobials studied, and MBEC90 was significantly higher than MIC90, becoming resistant to all the antimicrobial drugs tested. Higher biofilm production values were obtained in antibiotic-susceptible Escherichia coli in comparison to their resistant counterparts. However, regarding the relationships between antimicrobial resistance and biofilm formation, our analysis showed that each strain differed. A high antimicrobial resistance rate was found among the GNB studied. Moreover, almost all bacterial isolates were in vitro biofilm formers. Although there was no significant association between biofilm and antibiotic resistance, multidrug-resistant isolates were found to be greater biofilm formers than non-multidrug-resistant isolates.IMPORTANCE This study is the first one to analyze a high number of isolates of Gram-negative bacilli that are the cause of prosthetic joint infection. The analysis includes biofilm development and antimicrobial susceptibility testing of both planktonic and sessile bacteria. The obtained results support the clinical knowledge about the treatment of these bacteria when biofilms are involved.

Glycolysis is critical for granulocytic myeloid-derived suppressor cell (G-MDSC) activity during Staphylococcus aureus biofilm infection

Abstract Staphylococcus aureus (S. aureus) is a leading cause of prosthetic joint infection (PJI). These infections are often intractable due to biofilm formation, which are complex bacterial communities that adhere to biotic and abiotic surfaces. Within a biofilm, there is considerable heterogeneity in bacterial metabolism and gene expression that serves to create an anti-inflammatory milieu at the site of infection. This is due, in part, to the preferential recruitment of granulocytic myeloid-derived suppressor cells (G-MDSCs), a population of pathologically activated immature leukocytes with immunosuppressive features. Our prior work revealed that G-MDSCs are integral for promoting biofilm persistence via the production of interleukin-10 (IL-10) in response to biofilm-derived lactate. However, the mechanism responsible for G-MDSC anti-inflammatory activity in the context of biofilm infection is unknown. Using a mouse model of S. aureus PJI, time-course single-cell RNA sequencing (scRNA-seq) revealed a significant enrichment in glycolytic and hypoxic transcriptional signatures in infiltrating G-MDSCs. G-MDSCs significantly increased their glycolytic activity when co-cultured with S. aureus biofilm in vitro and inhibiting glycolysis during PJI in vivo with 2-DG nanoparticles significantly attenuated G-MDSC suppressive activity concomitant with a significant reduction in bacterial burden. This study demonstrates that glycolysis is required for G-MDSC-mediated immunosuppression and biofilm persistence during S. aureus PJI. Furthermore, our results demonstrate that G-MDSC metabolism can be targeted to improve infection outcomes. Supported by funding from NIH (2P01 AI083211) &amp; UNMC (UNMC Graduate Fellowship)

Experimental Polymorphism Survey in Intergenic Regions of the icaADBCR Locus in Staphylococcus aureus Isolates from Periprosthetic Joint Infections.

Staphylococcus aureus is a leading cause of prosthetic joint infections (PJI) characterized by bacterial biofilm formation and recalcitrance to immune-mediated clearance and antibiotics. The molecular events behind PJI infection are yet to be unraveled. In this sense, identification of polymorphisms in bacterial genomes may help to establish associations between sequence variants and the ability of S. aureus to cause PJI. Here, we report an experimental nucleotide-level survey specifically aimed at the intergenic regions (IGRs) of the icaADBCR locus, which is responsible for the synthesis of the biofilm exopolysaccharide PIA/PNAG, in a collection of strains sampled from PJI and wounds. IGRs of the icaADBCR locus were highly conserved and no PJI-specific SNPs were found. Moreover, polymorphisms in these IGRs did not significantly affect transcription of the icaADBC operon under in vitro laboratory conditions. In contrast, an SNP within the icaR coding region, resulting in a V176E change in the transcriptional repressor IcaR, led to a significant increase in icaADBC operon transcription and PIA/PNAG production and a reduction in S. aureus virulence in a Galleria mellonella infection model. In conclusion, SNPs in icaADBCR IGRs of S. aureus isolates from PJI are not associated with icaADBC expression, PIA/PNAG production and adaptation to PJI.

An Insight Into Lyme Prosthetic Joint Infection in Knee Arthroplasty: A Literature Review.

Lyme prosthetic joint infection (PJI) is a rare event, but it is imperative to include Lyme disease as a possible cause of PJI in a Lyme-endemic region. The purpose of this article was to review the reported cases of Lyme PJIs in knee arthroplasty and to initiate the development of a treatment strategy. We found five cases of Lyme PJI in the literature. All patients lived in the northeastern region of the United States. Four patients were successfully treated with surgical intervention and postoperative antibiotics. One patient was successfully treated with intravenous and oral antibiotics for 6 weeks, without surgical intervention. Synovial fluid Lyme polymerase chain reaction and serological tests were positive in all patients. On follow-up visits, after completion of their treatment, all patients were asymptomatic with a painless functional knee. We recommend considering Lyme disease as a cause of culture-negative PJIs in endemic regions. Additional research is needed to clearly define a treatment algorithm. Based on our literature review, we cannot recommend a single best treatment modality for the treatment of Lyme PJI. However, early irrigation and débridement with administration of postoperative antibiotics may improve early clinical outcomes.

The Unusual Cause of Prosthetic Joint Infection: Outcomes of Nontuberculous Mycobacteria Treatment Following Primary Total Knee Arthroplasty.

Nontuberculous mycobacterium (NTM) is a rare cause of prosthetic joint infection (PJI) following primary total knee arthroplasty (TKA). NTM causes a variety of infections, mainly divided into pulmonary and extrapulmonary infections. In Pakistan, there was a 7.7-fold increase in NTM infections from 21 cases in 2012 to 163 cases in 2018. An earlier study evaluating the distribution of NTM species across Pakistan suggested geographical variation across different regions, every area having its own distribution spectrum. There are no data available especially in developing countries such as Pakistan regarding PJI due to NTM following primary TKA. The purpose of our study was to determine treatment outcomes of two-stage revision surgery following NTM infection. This is a retrospective study. Patients who underwent TKA between June 2008 and December 2018 were included in the study. NTM was defined as the presence of traditional criteria for diagnosing PJI plus growth of NTM cultured from a joint aspirate or deep periprosthetic tissue specimen using Löwenstein-Jensen medium and Mycobacteria Growth Indicator Tube medium. All patients were female with a mean age of 62.8 ± 7.9 years. The mean body mass index was 25.6 ± 2.8 kg/m2. Treatment outcomes were categorized into favorable and unfavorable. We found rapid-growing mycobacterium in 6 patients whereas slow-growing mycobacterium was found in 2 patients only. Generally, clarithromycin was the standard antibiotic used in all cases of NTM infections. All patients underwent revision surgery. Meticulous surgical debridement and prolonged antibiotic treatment course were the only hope of cure to combat the unusual cause of PJI following primary TKA.

Genomic analysis of a rare recurrent Listeria monocytogenes prosthetic joint infection indicates a protected niche within biofilm on prosthetic materials

Listeria monocytogenes is a rare cause of prosthetic joint infections (PJI). In this study, we describe a case of recurrent L. monocytogenes infections, 39 months apart, following debridement and retention of a prosthetic hip. Despite numerous studies reporting persistent L. monocytogenes in human infections, the genomic and phenotypic changes that clinically relevant strains undergo in the host are poorly understood. Improved knowledge of how PJI occurs is needed to improve the management of prosthetic infections. We used a combination of long- and short-read sequencing to identify any potential genomic differences between two L. monocytogenes isolates that occurred over 39-month incubation in the host. The isolates, QI0054 and QI0055, showed three single nucleotide polymorphisms and three insertions or deletions, suggesting that the recurrent infection was caused by the same strain. To identify potential differences in the capacity for persistence of these isolates, their biofilm-forming ability and potential to colonize prosthesis-relevant materials was investigated both in microtitre plates and on prosthetic material titanium, stainless steel 316 and ultra-high molecular weight polyethylene. Whilst the L. monocytogenes isolate from the most recent infection (QI0055) was able to form higher biofilm in microtitre plates, this did not lead to an increase in biomass on prosthetic joint materials compared to the initial isolate (QI0054). Both clinical isolates were able to form significantly more biofilm on the two metal prosthetic materials than on the ultra-high molecular weight polyethylene, in contrast to reference strain Scott A. Transcriptomics revealed 41 genes overexpressed in biofilm state and 643 in planktonic state. Moreover, genes with mutations were actively expressed in both isolates. We conclude the isolates are derived from the same strain and hypothesize that L. monocytogenes formed biofilm on the prosthetic joint materials, with minimal exposure to stresses, which permitted their survival and growth.

Genomic Analysis of Cutibacterium acnes Strains Isolated from Prosthetic Joint Infections.

Cutibacterium acnes is a common cause of prosthetic joint infections (PJIs). The C. acnes population can be divided into six main phylotypes (IA1, IA2, IB, IC, II and III) that are associated with different clinical conditions and normal skin. A single-locus sequence typing (SLST) scheme can distinguish ten main SLST types: A-E (all IA1), F (IA2), G (IC), H (IB), K (II), L (III). We genome-sequenced and compared 16 strains of C. acnes isolated from healthy skin (n = 4) and PJIs (n = 12), including six PJI cases with a good outcome (four shoulder PJIs, one hip PJI, one knee PJI) and six with infection relapse (three shoulder PJIs, three hip PJIs). The sequenced strains belonged to four different phylotypes (IA1, IA2, IB and II) and seven different SLST types. All five type IB strains (all SLST type H1) were PJI isolates (three hip PJIs, two shoulder PJIs), and four of these caused infection relapse (three hip PJIs, one shoulder PJI). Isolates from PJI cases with a good outcome belonged to three different phylotypes (IA, IB, II). Interestingly, four strains (three strains from PJI cases with good outcome and one strain from healthy skin) contained a linear plasmid; these strains belonged to different SLST types (A1, C1, F4, H1) and were isolated in three different hospitals. This study suggests that type IB strains have the potential to cause infection relapse, in particular regarding hip PJIs. Moreover, our study revealed that strains belonging to the same SLST type can differ in their accessory genome in different geographic locations, indicative of microevolution.

Staphylococcus epidermidis small colony variants, clinically significant quiescent threats for patients with prosthetic joint infection

ObjectivesStaphylococcus epidermidis is a leading cause of prosthetic joint infection. Its relevance is based on its high ability to develop biofilm and small colony variants. However, the clinical associations between this bacterial subpopulation and prosthetic joint infections remain highly uncertain. We aimed to define the clinical characteristics and outcome of patients affected by S. epidermidis small colony variants, as well as their antimicrobial susceptibility. MethodsWe conducted a retrospective cohort study of patients with monomicrobial prosthetic joint infection. Clinical data and time to remission after prosthesis removal was compared between groups. Antimicrobial susceptibility of small colony variants and wild type strains were analyzed. ResultsS. epidermidis small colony variants were identified in 16 (37.20%) cultures from eligible subjects. These patients were less likely to achieve remission throughout the follow-up period (Hazard ratio, 0.45 [95% CI, 0.22-0.89], p=0.02), compared to those with wild type strains. In vitro experiments showed higher resistant rates to trimethoprim/sulfamethoxazole (62.5%), and lower resistant rates to levofloxacin (37.5%), among small colony variants. ConclusionsThe isolation of small colony variants was negatively associated with remission achievement throughout management. The search for this bacterial subpopulation and its antimicrobial susceptibility may be appropriate to adjust treatment and clinical expectations.

Lactate production by Staphylococcus aureus biofilm inhibits HDAC11 to reprogram the host immune response during persistent infection

Abstract Staphylococcus aureus (S. aureus) is a leading cause of prosthetic joint infection (PJI) typified by biofilm formation. Our laboratory has identified preferential myeloid-derived suppressor cell (MDSC) recruitment as a critical mechanism for biofilm persistence, as MDSCs are a main source of IL-10. We screened the Nebraska Transposon Mutant Library to identify S. aureus mutants impaired in their ability to trigger MDSC IL-10 production. Significant hits in lactate biosynthesis were identified. A S. aureus Δddh/ldh1/ldh2 mutant, defective in both D- and L-lactate production, decreased leukocyte IL-10 expression and biofilm-associated monocytes were reprogrammed to a pro-inflammatory state, resulting in reduced biofilm burden. Histone acetylation plays a central role in regulating gene expression and histone deacetylase (HDAC) activity was significantly increased in leukocytes recovered from mice infected with Δddh/ldh1/ldh2 compared to WT, resulting in decreased global histone 3 (H3) acetylation at the IL-10 promoter in MDSCs from Δddh/ldh1/ldh2-infected mice. Lactate inhibited HDAC11, resulting in unchecked activity of HDAC6, a positive regulator of Il-10 transcription, and increased IL-10 production. MDSCs and macrophages produced significantly less IL-10 when treated with HDAC6 inhibitor tubastatin A during co-culture with WT but not Δddh/ldh1/ldh2 biofilm. D-lactate was elevated in synovial fluid of patients with PJI compared to aseptic controls and lactate promoted IL-10 production by human monocyte-derived macrophages. Collectively, S. aureus lactate-mediated inhibition of HDAC11 plays a critical role during biofilm infection, leading to epigenetic changes that reprogram the host immune response.

Prosthetic hip joint infection by Bacillus Calmette-Guerin therapy following intravesical instillation for bladder cancer identified using whole-genome sequencing: a case report

BackgroundJoint replacement is an effective intervention and prosthetic joint infection (PJI) is one of the most serious complications of such surgery. Diagnosis of PJI is often complex and requires multiple modalities of investigation. We describe a rare cause of PJI which highlights these challenges and the role of whole-genome sequencing to achieve a rapid microbiological diagnosis to facilitate prompt and appropriate management.Case presentationA 79-year-old man developed chronic hip pain associated with a soft-tissue mass, fluid collection and sinus adjacent to his eight-year-old hip prosthesis. His symptoms started after intravesical Bacillus Calmette-Guerin (BCG) therapy for bladder cancer. Synovasure™ and 16S polymerase chain reaction (PCR) tests were negative, but culture of the periarticular mass and genome sequencing diagnosed BCG infection. He underwent a two-stage joint revision and a prolonged duration of antibiotic therapy which was curative.ConclusionsBCG PJI after therapeutic exposure can have serious consequences, and awareness of this potential complication, identified from patient history, is essential. In addition, requesting appropriate testing is required, together with recognition that traditional diagnostics may be negative in non-pyogenic PJI. Advanced molecular techniques have a role to enhance the timely management of these infections.

Staphylococcus aureus ATP Synthase Promotes Biofilm Persistence by Influencing Innate Immunity.

Staphylococcus aureus is a major cause of prosthetic joint infection (PJI), which is characterized by biofilm formation. S. aureus biofilm skews the host immune response toward an anti-inflammatory profile by the increased recruitment of myeloid-derived suppressor cells (MDSCs) that attenuate macrophage proinflammatory activity, leading to chronic infection. A screen of the Nebraska Transposon Mutant Library identified several hits in the ATP synthase operon that elicited a heightened inflammatory response in macrophages and MDSCs, including atpA, which encodes the alpha subunit of ATP synthase. An atpA transposon mutant (ΔatpA) had altered growth kinetics under both planktonic and biofilm conditions, along with a diffuse biofilm architecture that was permissive for leukocyte infiltration, as observed by confocal laser scanning microscopy. Coculture of MDSCs and macrophages with ΔatpA biofilm elicited significant increases in the proinflammatory cytokines interleukin 12p70 (IL-12p70), tumor necrosis factor alpha (TNF-α), and IL-6. This was attributed to increased leukocyte survival resulting from less toxin and protease production by ΔatpA biofilm as determined by liquid chromatography with tandem mass spectrometry (LC-MS/MS). The enhanced inflammatory response elicited by ΔatpA biofilm was cell lysis-dependent since it was negated by polyanethole sodium sulfanate treatment or deletion of the major autolysin, Atl. In a mouse model of PJI, ΔatpA-infected mice had decreased MDSCs concomitant with increased monocyte/macrophage infiltrates and proinflammatory cytokine production, which resulted in biofilm clearance. These studies identify S. aureus ATP synthase as an important factor in influencing the immune response during biofilm-associated infection and bacterial persistence.IMPORTANCE Medical device-associated biofilm infections are a therapeutic challenge based on their antibiotic tolerance and ability to evade immune-mediated clearance. The virulence determinants responsible for bacterial biofilm to induce a maladaptive immune response remain largely unknown. This study identified a critical role for S. aureus ATP synthase in influencing the host immune response to biofilm infection. An S. aureus ATP synthase alpha subunit mutant (ΔatpA) elicited heightened proinflammatory cytokine production by leukocytes in vitro and in vivo, which coincided with improved biofilm clearance in a mouse model of prosthetic joint infection. The ability of S. aureus ΔatpA to augment host proinflammatory responses was cell lysis-dependent, as inhibition of bacterial lysis by polyanethole sodium sulfanate or a ΔatpAΔatl biofilm did not elicit heightened cytokine production. These studies reveal a critical role for AtpA in shaping the host immune response to S. aureus biofilm.

Genotypic and Phenotypic Characteristics of Staphylococcus aureus Prosthetic Joint Infections: Insight on the Pathogenesis and Prognosis of a Multicenter Prospective Cohort.

Background Staphylococcus aureus is the leading cause of prosthetic joint infection (PJI). Beyond the antibiogram, little attention has been paid to the influence of deep microbiological characteristics on patient prognosis. Our aim was to investigate whether microbiological genotypic and phenotypic features have a significant influence on infection pathogenesis and patient outcome.MethodsA prospective multicenter study was performed, including all S. aureus PJIs (2016–2017). Clinical data and phenotypic (agr functionality, β-hemolysis, biofilm formation) and genotypic characteristics of the strains were collected. Biofilm susceptibility to antimicrobials was investigated (minimal biofilm eradication concentration [MBEC] assay).ResultsEighty-eight patients (39.8% men, age 74.7 ± 14.1 years) were included. Forty-five had early postoperative infections (EPIs), 21 had chronic infections (CPIs), and 19 had hematogenous infections (HIs). Twenty (22.7%) were caused by methicillin-resistant S. aureus. High genotypic diversity was observed, including 16 clonal complexes (CCs), with CC5 being the most frequent (30.7%). agr activity was greater in EPI than CPI (55.6% vs 28.6%; P = .041). Strains causing EPI were phenotypically and genotypically similar, regardless of symptom duration. Treatment failure (36.5%) occurred less frequently among cases treated with implant removal. In cases treated with debridement and implant retention, there were fewer failures among those who received combination therapy with rifampin. No genotypic or phenotypic characteristics predicted failure, except vancomycin minimal inhibitory concentration ≥1.5 mg/L (23.1% failure vs 3.4%; P = .044). MBEC50 was >128 mg/L for all antibiotics tested and showed no association with prognosis.Conclusions S. aureus with different genotypic backgrounds is capable of causing PJI, showing slight differences in clinical presentation and pathogenesis. No major microbiological characteristics were observed to influence the outcome, including MBEC.

Proteomic Analysis Reveals a Biofilm-Like Behavior of Planktonic Aggregates of Staphylococcus epidermidis Grown Under Environmental Pressure/Stress.

Prosthetic joint replacement failure has a huge impact on quality of life and hospitalization costs. A leading cause of prosthetic joint infection is bacteria-forming biofilm on the surface of orthopedic devices. Staphylococcus epidermidis is an emergent, low-virulence pathogen implicated in chronic infections, barely indistinguishable from aseptic loosening when embedded in a mature matrix. The literature on the behavior of quiescent S. epidermidis in mature biofilms is scarce. To fill this gap, we performed comparative analysis of the whole proteomic profiles of two methicillin-resistant S. epidermidis strains growing in planktonic and in sessile form to investigate the molecular mechanisms underlying biofilm stability. After 72-h culture of biofilm-forming S. epidermidis, overexpression of proteins involved in the synthesis of nucleoside triphosphate and polysaccharides was observed, whereas planktonic bacteria expressed proteins linked to stress and anaerobic growth. Cytological analysis was performed to determine why planktonic bacteria unexpectedly expressed proteins typical of sessile culture. Images evidenced that prolonged culture under vigorous agitation can create a stressful growing environment that triggers microorganism aggregation in a biofilm-like matrix as a mechanism to survive harsh conditions. The choice of a unique late time point provided an important clue for future investigations into the biofilm-like behavior of planktonic cells. Our preliminary results may inform comparative proteomic strategies in the study of mature bacterial biofilm. Finally, there is an increasing number of studies on the aggregation of free-floating bacteria embedded in an extracellular matrix, prompting the need to gain further insight into this mode of bacterial growth.