Prosthetic Joint Infection Diagnosis Using Broad-Range PCR of Biofilms Dislodged from Knee and Hip Arthroplasty Surfaces Using Sonication

Periprosthetic tissue and/or synovial fluid PCR has been previously studied for prosthetic joint infection (PJI) diagnosis; however, few studies have assessed the utility of PCR on biofilms dislodged from the surface of explanted arthroplasties using vortexing and sonication (i.e., sonicate fluid PCR). We compared sonicate fluid 16S rRNA gene real-time PCR and sequencing to culture of synovial fluid, tissue, and sonicate fluid for the microbiologic diagnosis of PJI. PCR sequences generating mixed chromatograms were decatenated using RipSeq Mixed. We studied sonicate fluids from 135 and 231 subjects with PJI and aseptic failure, respectively. Synovial fluid, tissue, and sonicate fluid culture and sonicate fluid PCR had similar sensitivities (64.7, 70.4, 72.6, and 70.4%, respectively; P > 0.05) and specificities (96.9, 98.7, 98.3, and 97.8%, respectively; P > 0.05). Combining sonicate fluid culture and PCR, the sensitivity was higher (78.5%, P < 0.05) than those of individual tests, with similar specificity (97.0%). Thirteen subjects had positive sonicate fluid culture but negative PCR, and 11 had negative sonicate fluid culture but positive PCR (among which 7 had prior use of antimicrobials). Broad-range PCR and culture of sonicate fluid have equivalent performance for PJI diagnosis.     

Diagnosis of Prosthetic Joint Infection by Use of PCR-Electrospray Ionization Mass Spectrometry

We compared PCR-electrospray ionization mass spectrometry (PCR-ESI/MS) to culture using sonicate fluid from 431 subjects with explanted knee (n = 270) or hip (n = 161) prostheses. Of these, 152 and 279 subjects had prosthetic joint infection (PJI) and aseptic failure, respectively. The sensitivities for detecting PJI were 77.6% for PCR-ESI/MS and 69.7% for culture (P = 0.0105). The specificities were 93.5 and 99.3%, respectively (P = 0.0002).     

Evaluation of the use of sonication of retrieved implants for the diagnosis of prosthetic joint infection in a routine setting

In order to evaluate the usefulness of sonication of retrieved implants for the diagnosis of prosthetic joint infection (PJI) in a large group of patients in a routine setting, we designed a 3-year retrospective study. Patients were classified into two groups: those meeting the clinical criteria of PJI and those that did not (control group). Two hundred patients and 276 samples were included. The types of infection were early (n?=?44), delayed (n?=?53), positive intraoperative cultures (n?=?13) and late-acute (n?=?8). The culture sensitivities of sonicate fluid, periprosthetic tissue, synovial fluid and combination of periprosthetic tissue and/or synovial fluid were 69.5, 52.8, 54.8 and 60.2%, respectively. The specificities were 97.6, 90.3, 93.0 and 89.9%, respectively. Sonicate fluid culture of implants was more sensitive than peri-implant tissue, synovial fluid and combination of periprosthetic tissue and/or synovial fluid for all infection types, though it was especially useful in delayed infection: 91.3% vs. 60.0% (p?=?0.0015), 63.2% (p?=?0.0005) and 66.7% (p?=?0.0001), respectively. When sonicate fluid culture of implants was performed in addition to conventional cultures, the sensitivity increased significantly in total (from 60.2 to 77.1%) and delayed PJI (from 45.1 to 71.7%). On the other hand, for early PJI, sonicate fluid culture of prosthesis was not superior to conventional diagnostic methods.     

Sonication of Explanted Prosthesis Combined with Incubation in BD Bactec Bottles for Pathogen-Based Diagnosis of Prosthetic Joint Infection

Prosthetic joint infection (PJI) is a rare but refractory complication of arthroplasty. Accurate identification of pathogens is a key step for successful treatment of PJI, which remains a challenge for clinicians and laboratory workers. We designed a combined culture method with sonication of implants and incubation in a BD Bactec system to improve the effectiveness of pathogen diagnosis in PJI. The aims of this study were to investigate the diagnostic accuracy of sonicate fluid cultures in the BD Bactec system and to compare the results with those of synovial fluid cultures in the BD Bactec system. The prosthetic components removed were sonicated in Ringer''s solution, and then sonicate fluid was incubated in Bactec bottles for 5 days. Synovial fluid was incubated in Bactec bottles for 5 days as a control. Synovial fluid cultures with Bactec bottles and sonicate fluid cultures with Bactec bottles showed sensitivities of 64% and 88%, respectively (P = 0.009), with specificities of 98% and 87% (P = 0.032), respectively. Sonicate fluid cultures with Bactec bottles were more sensitive than synovial fluid cultures with Bactec bottles regardless of whether antimicrobial agents were used within 14 days before surgery (81% versus 52%; P = 0.031) or not (93% versus 72%; P = 0.031). Sonication of explanted prostheses followed by incubation of the resulting sonicate fluid in Bactec bottles detected many more pathogens than did synovial fluid cultures with Bactec bottles. This method is also effective in cases with antibiotic treatment before surgery.     

Microbiologic Diagnosis of Prosthetic Shoulder Infection by Use of Implant Sonication

We recently described a sonication technique for the diagnosis of prosthetic knee and hip infections. We compared periprosthetic tissue culture to implant sonication followed by sonicate fluid culture for the diagnosis of prosthetic shoulder infection. One hundred thirty-six patients undergoing arthroplasty revision or resection were studied; 33 had definite prosthetic shoulder infections and 2 had probable prosthetic shoulder infections. Sonicate fluid culture was more sensitive than periprosthetic tissue culture for the detection of definite prosthetic shoulder infection (66.7 and 54.5%, respectively; P = 0.046). The specificities were similar (98.0% and 95.1%, respectively; P = 0.26). Propionibacterium acnes was the commonest species detected among culture-positive definite prosthetic shoulder infection cases by periprosthetic tissue culture (38.9%) and sonicate fluid culture (40.9%). All subjects from whom P. acnes was isolated from sonicate fluid were male. We conclude that sonicate fluid culture is useful for the diagnosis of prosthetic shoulder infection.The frequency of shoulder replacement surgery is increasing (1). The incidence of prosthetic shoulder infection varies from 0.4 to 15.4% (6, 7). When an infection is present, the infection requires unique medical and surgical management, rendering an accurate diagnosis critical. However, since patients with prosthetic shoulder infection often present with stiffness and/or pain alone (7), the achievement of an accurate diagnosis is challenging.Periprosthetic tissue has been the specimen cultured for the microbiologic diagnosis of prosthetic shoulder infection. Specificity is an issue, as microorganisms (e.g., Propionibacterium and Staphylococcus spp.) can be contaminants, and the number of microorganisms in tissue is small. As a result, it has been suggested that multiple samples be obtained; for prosthetic hips and knees, it is recommended that five or six periprosthetic tissue specimens be cultured (2). No such data are available for shoulder implants.We recently clinically validated a sonication technique that is used to sample biofilm bacteria on the surface of removed hip and knee implants placed in solid containers. We demonstrated that the culture of samples obtained by sonication of the implant was more sensitive than the culture of periprosthetic tissue for the diagnosis of prosthetic hip and knee infections (22). The poor sensitivity of the latter likely relates to the presence of bacteria in biofilms on the prosthesis surface, a site not well sampled when periprosthetic tissue samples for culture are obtained. No data on the accuracy of sonication for the diagnosis of prosthetic shoulder infection are available.The proportion of patients with shoulder infections due to Propionibacterium acnes is significantly greater than the proportion of patients with lower limb infections due to P. acnes (12). Sperling et al. reported that Propionibacterium spp. account for 16% of prosthetic shoulder infections (16). Franta et al. reported that among 31/282 patients (11%) with unsatisfactory shoulder arthroplasties, positive intraoperative cultures were found in 23 at the time of revision surgery, with the most common organisms isolated being coagulase-negative Staphylococcus spp., followed by P. acnes (11). Cheung et al. reported the results of reimplantation of glenoid components following removal and allogeneic bone grafting in seven patients; specimens from two patients demonstrated the growth of P. acnes (5). These two patients had continuing pain and radiographic evidence of glenoid component loosening and subsequently underwent repeat revision surgery, whereas the remaining patients did well and did not require repeat revision surgery (5), suggesting a role for P. acnes in pain and component loosening. Accordingly, the accurate detection of a Propionibacterium spp. is paramount in the diagnosis of prosthetic shoulder infection.The purpose of the present study was to compare implant sonication to periprosthetic tissue culture for the diagnosis of prosthetic shoulder infection. We also evaluated immunofluorescence microscopy and PCR analysis of sonicate fluid to detect prosthetic shoulder infection caused by the two most frequently associated microorganisms. Finally, we compared patient characteristics associated with Propionibacterium prosthetic shoulder infection versus those associated with non-Propionibacterium prosthetic shoulder infection.(This work was presented in part at the 16th Annual European Congress of Clinical Microbiology and Infectious Diseases, April 2006, Nice, France, and the 47th Interscience Conference on Antimicrobial Agents and Chemotherapy, September 2007, Chicago, IL.)     

PCR-Based Diagnosis of Prosthetic Joint Infection

We performed a meta-analysis to evaluate use of PCR assays for diagnosis of prosthetic joint infection (PJI). The pooled sensitivity and specificity were 0.86 (95% confidence interval [CI], 0.77 to 0.92) and 0.91 (CI, 0.81 to 0.96), respectively. Subgroup analyses showed that use of tissue samples may improve sensitivity, and quantitative PCR and sonication of prostheses fluid may improve specificity. The results showed that PCR is reliable and accurate for detection of PJI.     

Campylobacter Prosthetic Joint Infection

A 75-year-old man was diagnosed with probable Campylobacter jejuni prosthetic knee infection after a diarrheal illness. Joint aspirate and operative cultures were negative, but PCR of prosthesis sonicate fluid was positive, as was stool culture. Nineteen additional cases of Campylobacter prosthetic joint infection reported in the literature are reviewed.     

Evaluation of a Genus- and Group-Specific Rapid PCR Assay Panel on Synovial Fluid for Diagnosis of Prosthetic Knee Infection

We evaluated a genus- and group-specific PCR assay panel using 284 prosthetic knee synovial fluid samples collected from patients presenting to our institution with implant failure. Using the Musculoskeletal Infection Society diagnostic criteria, 88 and 196 samples were classified as showing prosthetic joint infection (PJI) and aseptic failure (AF), respectively. Sensitivities of the synovial fluid PCR panel and culture were 55.6% and 76.1% (P ≤ 0.001), respectively, and specificities were 91.8% and 97.4% (P = 0.016), respectively. Among the 70 subjects who had received antibiotics within the month preceding synovial fluid aspiration (48 of whom had PJI), PCR panel and synovial fluid culture sensitivities were 64.5% and 85.4%, respectively (P < 0.0001). In this group, the PCR panel detected Staphylococcus aureus in two culture-negative PJI cases. Overall, the evaluated molecular diagnostic tool had low sensitivity when applied to synovial fluid.     

Detection of Prosthetic Hip Infection at Revision Arthroplasty by Immunofluorescence Microscopy and PCR Amplification of the Bacterial 16S rRNA Gene

In this study the detection rates of bacterial infection of hip prostheses by culture and nonculture methods were compared for 120 patients with total hip revision surgery. By use of strict anaerobic bacteriological practice during the processing of samples and without enrichment, the incidence of infection by culture of material dislodged from retrieved prostheses after ultrasonication (sonicate) was 22%. Bacteria were observed by immunofluorescence microscopy in 63% of sonicate samples with a monoclonal antibody specific for Propionibacterium acnes and polyclonal antiserum specific for Staphylococcus spp. The bacteria were present either as single cells or in aggregates of up to 300 bacterial cells. These aggregates were not observed without sonication to dislodge the biofilm. Bacteria were observed in all of the culture-positive samples, and in some cases in which only one type of bacterium was identified by culture, both coccoid and coryneform bacteria were observed by immunofluorescence microscopy. Bacteria from skin-flake contamination were readily distinguishable from infecting bacteria by immunofluorescence microscopy. Examination of skin scrapings did not reveal large aggregates of bacteria but did reveal skin cells. These were not observed in the sonicates. Bacterial DNA was detected in 72% of sonicate samples by PCR amplification of a region of the bacterial 16S rRNA gene with universal primers. All of the culture-positive samples were also positive for bacterial DNA. Evidence of high-level infiltration either of neutrophils or of lymphocytes or macrophages into associated tissue was observed in 73% of patients. Our results indicate that the incidence of prosthetic joint infection is grossly underestimated by current culture detection methods. It is therefore imperative that current clinical practice with regard to the detection and subsequent treatment of prosthetic joint infection be reassessed in the light of these results.     

Meta-Analysis of Sonication Fluid Samples from Prosthetic Components for Diagnosis of Infection after Total Joint Arthroplasty

This meta-analysis included 12 studies that evaluated sonication fluid cultures (SFC) for the diagnosis of prosthetic joint infection (PJI). The pooled sensitivity and specificity were 0.80 (95% confidence interval [CI], 0.74 to 0.84) and 0.95 (CI, 0.90 to 0.98), respectively. Subgroup analyses showed that a 14-day anaerobic culture may improve sensitivity, the use of centrifugation or vortexing may improve specificity, and the use of 400 to 500 ml of Ringer''s solution for containers may improve sensitivity and specificity. The best SFC cutoff was ≥5 CFU. In conclusion, SFC has high sensitivity and very high specificity for diagnosing PJI.     

The utility of dithiothreitol treatment of periprosthetic tissues and explanted implants in the diagnosis of prosthetic joint infection

PurposeThe methods used for the processing of periprosthetic tissues and explanted implants to improve culture outcome especially in biofilm mediated prosthetic joint infections (PJIs) are still debated upon. Studies have reported that Dithiothreitol (DTT) pretreatment of infected devices gives similar results as sonication. However, none of them evaluated the DTT treatment of periprosthetic tissues and explanted implants in the same cohort. We evaluated the diagnostic utility of DTT treatment of periprosthetic tissue and explanted implants, as compared to the normal saline treatment of periprosthetic tissues and sonication of explanted implants for the diagnosis of PJI.MethodsSeventy-three revision arthroplasty cases were prospectively included in this study. Three to five tissue specimens and the explanted implants were collected from each patient. Periprosthetic tissue samples were processed by both normal saline and DTT treatments. Explanted implants were subjected to both DTT treatment and sonication. Musculoskeletal Infection Society (MSIS) PJI criteria was used as the reference standard for the diagnosis of PJI.ResultsOf the 73 cases enrolled, 34 had PJI and 39 were aseptic failures. The sensitivity of DTT treated periprosthetic tissue culture (PTC) and saline treated PTC was similar (66.6% vs 58.8%, P = 0.25). The specificity of both was 100%. Sonication and DTT treatment of explanted implants showed comparable sensitivity (85.3% vs 82.4%) and specificity (100% vs 97.4%), P > 0.99. Compared to DTT treated PTC, culture of DTT treated explanted implants significantly improved the diagnosis of PJI (P = 0.03).ConclusionsWe could verify that DTT can be used to improve culture outcome in laboratories where biofilm detaching sonication techniques are not available for infected implants. In addition, we showed that it is possible to use DTT for treating tissue biopsies, but larger studies are required to confirm our findings.     

The application of sonication in diagnosis of periprosthetic joint infection

Periprosthetic joint infection (PJI) is a catastrophic complication after total joint arthroplasty. It has always been difficult to diagnose PJI, which is characterised by existence of biofilm around the implants. The application of sonication has proven advantageous for pathogen detection. This meta-analysis of clinical trials was performed to evaluate the diagnostic value of sonication and to compare it with traditional bacterial culture. We assessed 16 studies that evaluated sonication fluid cultures (SFC) for the diagnosis of PJI. It was shown that sonication may be of great value in PJI diagnosis, with a pooled sensitivity of 0.79 (95 % confidence interval [CI]?=?0.76–0.81), specificity of 0.95 (CI?=?0.94–0.96), DOR of 71.20 (CI?=?31.08–163.10), PLR of 15.25 (CI?=?6.44–36.15), and NLR of 0.23 (CI?=?0.18–0.30). The AUC value of the SROC was 0.90. The results of this meta-analysis showed that culture of fluid after sonication was of great value for PJI diagnosis. Sonication was more sensitive than traditional tissue culture with lower specificity, especially for patients previously taking antibiotics.     

Sonication of explanted prosthetic components in bags for diagnosis of prosthetic joint infection is associated with risk of contamination

Explanted orthopedic implants from 54 patients with aseptic failure and 24 patients with prosthetic knee or hip infection were sonicated in polyethylene bags. The sensitivities of periprosthetic tissue and sonicate fluid cultures for the diagnosis of prosthetic joint infection were 54% and 75%, whereas the specificities were 98% and 87%, respectively. Sonication in bags improved bacterial recovery from the surface of orthopedic implants; however, it lacked specificity, due to bag leakage.     

Miliary tuberculosis with delayed-onset total knee arthroplasty Mycobacteria tuberculosis infection successfully treated with medical therapy alone: A case report and literature review

Tuberculosis (TB) affecting a prosthetic knee is an unusual and diagnostically challenging presentation of this disease. This study reported a case of an 80-year-old man with a left total knee arthroplasty (TKA) performed eight years before his presentation. He presented with left knee swelling and pain for one month. Knee X-rays showed a normal joint space with no loosening of his prosthesis. His chest X-ray showed miliary disease, and microbiological studies of his sputum and synovial fluid aspirate grew Mycobacteria tuberculosis complex. He was successfully medically treated with anti-tuberculous therapy alone for one year. His knee hardware was retained, and he did not require debridement, resection, or revision. It is believed that this is the first reported case of miliary TB with delayed-onset TKA prosthetic joint infection (PJI) in which the prosthesis was successfully retained. Thirty-eight published TB TKA PJI cases in medical literature were also reviewed.     

Ureaplasma parvum Prosthetic Joint Infection Detected by PCR

We describe the first reported case of Ureaplasma parvum prosthetic joint infection (PJI) detected by PCR. Ureaplasma species do not possess a cell wall and are usually associated with colonization and infection of mucosal surfaces (not prosthetic material). U. parvum is a relatively new species name for certain serovars of Ureaplasma urealyticum, and PCR is useful for species determination. Our patient presented with late infection of his right total knee arthroplasty. Intraoperative fluid and tissue cultures and pre- and postoperative synovial fluid cultures were all negative. To discern the pathogen, we employed PCR coupled with electrospray ionization mass spectrometry (PCR/ESI-MS). Our patient''s failure to respond to empirical antimicrobial treatment and our previous experience with PCR/ESI-MS in culture-negative cases of infection prompted us to use this approach over other diagnostic modalities. PCR/ESI-MS detected U. parvum in all samples. U. parvum-specific PCR testing was performed on all synovial fluid samples to confirm the U. parvum detection.     

Evaluation of 16S rRNA Gene PCR Sensitivity and Specificity for Diagnosis of Prosthetic Joint Infection: a Prospective Multicenter Cross-Sectional Study

There is no standard method for the diagnosis of prosthetic joint infection (PJI). The contribution of 16S rRNA gene PCR sequencing on a routine basis remains to be defined. We performed a prospective multicenter study to assess the contributions of 16S rRNA gene assays in PJI diagnosis. Over a 2-year period, all patients suspected to have PJIs and a few uninfected patients undergoing primary arthroplasty (control group) were included. Five perioperative samples per patient were collected for culture and 16S rRNA gene PCR sequencing and one for histological examination. Three multicenter quality control assays were performed with both DNA extracts and crushed samples. The diagnosis of PJI was based on clinical, bacteriological, and histological criteria, according to Infectious Diseases Society of America guidelines. A molecular diagnosis was modeled on the bacteriological criterion (≥1 positive sample for strict pathogens and ≥2 for commensal skin flora). Molecular data were analyzed according to the diagnosis of PJI. Between December 2010 and March 2012, 264 suspected cases of PJI and 35 control cases were included. PJI was confirmed in 215/264 suspected cases, 192 (89%) with a bacteriological criterion. The PJIs were monomicrobial (163 cases [85%]; staphylococci, n = 108; streptococci, n = 22; Gram-negative bacilli, n = 16; anaerobes, n = 13; others, n = 4) or polymicrobial (29 cases [15%]). The molecular diagnosis was positive in 151/215 confirmed cases of PJI (143 cases with bacteriological PJI documentation and 8 treated cases without bacteriological documentation) and in 2/49 cases without confirmed PJI (sensitivity, 73.3%; specificity, 95.5%). The 16S rRNA gene PCR assay showed a lack of sensitivity in the diagnosis of PJI on a multicenter routine basis.     

Laboratory Diagnosis of Prosthetic Joint Infection, Part II

Prosthetic joint infection (PJI), although a rare complication of primary or revision arthroplasty, is reported more frequently as the number patients undergoing arthroplasty increases. Accurate diagnosis of PJI is essential for adequate management and outcome. Although multiple tests have been applied, in some cases, differentiation of PJI from aseptic loosening of the prosthesis remains a challenge. Here, we review the current diagnostic laboratory modalities used for the diagnosis PJI. In Part I of this two-part article, components of the preoperative evaluation of the patient and the histology of the intraoperative evaluation were discussed. Part II of the article discusses the remaining components of the intraoperative evaluation, including periprosthetic tissue and sonicate fluid cultures. In addition, recent investigational approaches for the diagnosis of PJI, antimicrobial susceptibility testing, and management of PJIs are reviewed.     

Improved Diagnosis of Infection Associated with Osteosynthesis by Use of Sonication of Fracture Fixation Implants

Previous studies have shown that sonication fluid cultures from removed orthopedic devices improved the microbiological diagnosis of orthopedic implant-associated infections; however, few of these investigations have applied sonication to the removed fracture fixation devices to evaluate its utility for the diagnosis of osteosynthesis-associated infection (OAI). We compared sonication fluid to conventional tissue cultures from 180 subjects with different sizes of plates and screws (n = 156), spinal implants (n = 26), and intramedullary nails (n = 3), of whom 125 and 55 subjects had OAI and noninfected osteosynthesis (NIO), respectively. The sensitivity for detecting OAI was 90.4% for sonication fluid culture and 56.8% for periprosthetic tissue cultures (P < 0.05), and the specificities were 90.9% and 96.4%, respectively. Sonication fluid culture detected more pathogens than peri-implant tissue culture (113 versus 71; P < 0.001), while polymicrobial infections were diagnosed by sonication fluid cultures and tissue cultures in 20.8% and 8% (P < 0.001), respectively. Microbiological diagnosis was achieved exclusively by sonication fluid cultures for 47 (90.4%) subjects, and among them, 18 (38.3%) had previously received antibiotics, whereas in five (9.6%) infected subjects, tissue culture was positive and the sonication fluid culture was negative. Among 39 (31.2%) OAI cases receiving antibiotics, the identification of the organisms occurred in 38.5% and 82.1% of the tissue and sonication fluid cultures, respectively (P < 0.049). We demonstrated that sonication fluid culture from removed osteosyntheses has the potential for improving the microbiological diagnosis of OAI.     

Role of universal 16S rRNA gene PCR and sequencing in diagnosis of prosthetic joint infection

The etiological diagnosis of prosthetic joint infection (PJI) requires the isolation of microorganisms from periprosthetic samples. Microbiological cultures often yield false-positive and false-negative results. 16S rRNA gene PCR combined with sequencing (16SPCR) has proven useful for diagnosing various infections. We performed a prospective study to compare the utility of this approach with that of culture to diagnose PJI using intraoperative periprosthetic samples. We analyzed 176 samples from 40 patients with PJI and 321 samples from 82 noninfected patients using conventional culture and 16SPCR. Three statistical studies were undertaken following a previously validated mathematical model: sample-to-sample analysis, calculation of the number of samples to be studied, and calculation of the number of positive samples necessary to diagnose PJI. When only the number of positive samples is taken into consideration, a 16SPCR-positive result in one sample has good specificity and positive predictive value for PJI (specificity, 96.3%; positive predictive value, 91.7%; and likelihood ratio [LR], 22), while 3 positive cultures with the same microorganism are necessary to achieve similar specificity. The best combination of results for 16SPCR was observed when 5 samples were studied and the same microorganism was detected in 2 of them (sensitivity, 94%; specificity, 100%; and LR, 69.62). The results for 5 samples with 2 positive cultures were 96% and 82%, respectively, and the likelihood ratio was 1.06. 16SPCR is more specific and has a better positive predictive value than culture for diagnosis of PJI. A positive 16SPCR result is largely suggestive of PJI, even when few samples are analyzed; however, culture is generally more sensitive.     

Origin and characteristics of haematogenous periprosthetic joint infection

ObjectivesRecognition of infectious origin of haematogenous periprosthetic joint infections (PJI) is crucial. We investigated the primary focus and characteristics of haematogenous PJI.MethodsConsecutive patients who presented with haematogenous PJI between 01/2010 and 01/2018 were retrospectively analysed. Haematogenous PJI was defined by diagnosis of infection ≥1 month after surgery, acute manifestation after a pain-free period and positive blood or prosthetic-site culture and/or evidence of distant infectious focus consistent with the pathogen. Fisher's exact, Student's t and Mann–Whitney U tests were used, as appropriate.ResultsA total of 106 episodes of PJI were included, involving 59 knee, 45 hip, one shoulder and one elbow prostheses. The median time from last surgery until haematogenous PJI was 47 months (range, 1–417 months). The pathogen was identified in 105 episodes (99%), including Staphylococcus aureus (n = 43), streptococci (n = 32), enterococci (n = 13), Gram-negative bacteria (n = 9) and coagulase-negative staphylococci (n = 8). Gram-negative bacteria were significantly more often found in hip joints than in knee joints. Blood cultures grew the pathogen in 43 of 70 episodes (61%). The primary infectious focus was identified in 72 episodes (68%) and included infections of intravascular devices or heart valves (22 episodes), skin and soft tissue (16 episodes), the oral cavity (12 episodes), urogenital (12 episodes) or gastrointestinal tract (seven episodes) and other sites (three episodes).ConclusionsIn acute PJI manifesting after a pain-free period, the haematogenous infection route should be considered and the primary infectious focus should be actively searched for. The cardiovascular system, skin and soft tissue, oral cavity, urogenital and gastrointestinal tracts were common origins of haematogenous PJI.