Sonication Fluid Culture Research Articles

Clinical utility of sonication for diagnosing infection and colonization of cardiovascular implantable electronic devices.

Our study aimed to evaluate the sensitivity of the sonication tool for the microbiological diagnosis of cardiovascular implantable electronic device infections (CIEDIs). The extracted cardiac implants of 52 patients were assessed: 19 with CIEDI and 33 with elective generator replacement or revision without clinical infection. Sonication fluid culture of explanted CIEDs yielded higher numbers of microorganisms than pocket tissue or swab cultures. The sensitivity of sonication fluid culture was significantly higher than that of pocket swab and tissue culture for microbiological diagnosis of CIEDI. The microorganisms isolated most frequently via sonication of explanted CIEDs were Gram-positive cocci (70%), of which 50% was coagulase-negative Staphylococcus. Sonication fluid culture detected colonization in 36.4% of the non-infected patients. Sonication fluid culture represents a promising diagnostic strategy with increased sensitivity compared to conventional culture methods for microbiological diagnosis of cardiac devices associated with infection and colonization.

Sonication fluid culture of antibiotic-loaded bone cement spacer has high accuracy to confirm eradication of infection before reimplantation of new prostheses

BackgroundSonication fluid culture of antibiotic-loaded bone cement spacer has been used to predict reinfection of two-stage revision, but its value remains disputable. This study aims to evaluate the association between the culture result of the sonicated spacer and the status of patients with periprosthetic joint infection receiving two-stage revision.Materials and methodsA comprehensive electronic literature search was performed through four databases including PubMed, Embase/Ovid, and EBSCO, and the Cochrane Library to retrieve studies in which sonication fluid culture of the antibiotic spacer was conducted before reimplantation. The pooled sensitivity, specificity, positive likelihood ratio (PLR), negative likelihood ratio (NLR), and diagnostic odds ratio (DOR) were calculated to assess the association between the culture result of sonicated spacer and prognosis of the two-stage revision.ResultsEleven eligible studies comprising 603 artificial joints with PJI (134 suffering a clinical failure of two-stage revision) were included in the quantitative analysis. The pooled incidences of positive culture of sonicated spacer and intraoperative tissue were 0.14 (95% confidence interval [CI] 0.08–0.21) and 0.14 (95% CI 0.08–0.20), respectively. A positive culture of sonicated antibiotic-loaded bone cement spacer illustrated moderate sensitivity (0.31, 95% CI 0.13–0.58) but high specificity (0.94, 95% CI 0.86–0.98) for the diagnosis of therapeutic failure of two-stage revision; the pooled DOR was 7.67 (95% CI, 3.63–16.22). Meanwhile, the pooled sensitivity, specificity, and DOR of intraoperative tissue culture during the two-stage revision to predict therapeutic failure were 0.32 (95% CI, 0.20–0.47), 0.96 (95% CI, 0.92–0.98), and 10.62 (95% CI, 4.90–23.01), respectively.ConclusionsSonication fluid culture of antibiotic-loaded bone cement spacer revealed high accuracy for confirming eradication of infection before reimplantation of new prostheses and therefore could be used as a supplement for assessing therapeutic effect for PJI. However, both sonication fluid culture and intraoperative tissue culture from antibiotic-loaded bone cement spacer showed restricted yield for the prediction of a septic failure after the two-stage revision of PJI. Large-scale, prospective studies are still needed to testify current findings.

Targeted next generation sequencing for elbow periprosthetic joint infection diagnosis

16S ribosomal RNA (rRNA) gene PCR followed by next-generation sequencing (NGS) was compared to culture of sonicate fluid derived from total elbow arthroplasty for periprosthetic joint infection (PJI) diagnosis. Sonicate fluids collected from 2007 to 2019 from patients who underwent revision of a total elbow arthroplasty were retrospectively analyzed at a single institution. PCR amplification of the V1-V3 region of the 16S rRNA gene was performed, followed by NGS using an Illumina MiSeq. Results were compared to those of sonicate fluid culture using McNemar's test of paired proportions.Forty-seven periprosthetic joint infections and 58 non-infectious arthroplasty failures were studied. Sensitivity of targeted NGS was 85%, compared to 77% for culture (P = 0.045). Specificity and positive and negative predictive values of targeted NGS were 98, 98 and 89%, respectively, compared to 100, 100 and 84%, respectively, for culture. 16S rRNA gene-based targeted metagenomic analysis of sonicate fluid was more sensitive than culture.

Sonication in the diagnosis of fracture-related infections (FRI)\u2014a retrospective study on 230 retrieved implants

BackgroundIn fracture-related infections (FRI), both the diagnosis of the infection and the identification of the causative pathogen are crucial to optimize treatment outcomes. Sonication has been successfully used for periprosthetic joint infections (PJI); however, its role in FRI remains unknown. Our aim was to determine the diagnostic accuracy (sensitivity, specificity) of sonicate fluid culture (SFC). The primary objective was to compare SFC with peri-implant tissue culture (PTC) overall and among subgroups using the consensus definition by Metsemakers et al. The secondary objective was to determine the yield of SFC in possible fracture-related infections (PFRI).MethodsFrom March 2017 to May 2019, 230 cases of retrieved implants were retrospectively reviewed. To perform sonication, explants were placed in sterile polypropylene jars intraoperatively. After treatment in an ultrasonic bath (Bandelin, Berlin, Germany), sonicate fluid was incubated into blood culture bottles, and conventional culturing was eventually performed. Sensitivity and specificity were determined using two-by-two contingency tables. McNemar’s test was used to compare proportions among paired samples while Fisher’s exact test was used for comparison between categorical variables.ResultsOf the 230 cases, 107 were identified as FRI, whereas 123 were aseptic revision cases (ARC). Of the latter, 105 were labeled as PFRI. Sensitivity of SFC was higher in comparison with PTC, although this did not reach statistical significance (90.7% vs. 84.1%; p = .065). The specificity of SFC was significantly lower than that of PTC (73.2% vs. 88.6%; p = .003). In PFRI, SFC yielded significantly more positive results than PTC (33/105 vs. 14/105; p = .003). Overall, 142 pathogens were identified by SFC, whereas 131 pathogens were found by PTC.ConclusionsWe found that sonication of fracture fixation devices may be a useful adjunct in FRI, especially in “low-grade” infections lacking confirmatory clinical criteria. Standardized diagnostic protocols are warranted in order to further optimize the diagnostic accuracy.

The value of conventional radiographs for diagnosing internal fixation-associated infection

BackgroundThe aim of the study is to assess the diagnostic value of preoperative conventional radiographs for diagnosing infection associated with internal fixation devices.MethodsWe prospectively collected data of patients undergoing removal of internal fixation devices for any reason. Infection was diagnosed in case of purulence, sinus tract, positive histopathology and/or positive peri-implant tissue or sonication fluid culture. In radiographs radiolucent lines, implant breakage or displacement, or periosteal reaction were assessed. White blood cell count (WBC) and serum C-reactive protein (CRP) were determined at admission.ResultsWe included 421 surgeries in 380 patients (median age 53.6 years, range 11–98 years), mainly indicated for infection (24.9%), nonunion (20.0%) and symptomatic implants (13.5%). Radiologic signs of infection included radiolucent lines (11.4%); implant breakage (12.4%) or displacement (10.7%); and periosteal reaction (7.1%). Infection was confirmed in 116 cases (27.6%). Only radiolucent lines (OR = 1.86 [95%CI: 1.00–3.38]) and periosteal reaction (OR = 2.48 [95%CI: 1.17–5.26]) were associated with infection, with a low sensitivity (16.4 and 12.1%, respectively), and high specificity (90.5 and 94.8%, respectively). Preoperative WBC and CRP had a sensitivity of 23.0 and 35.3%, and specificity of 91.7 and 89.5%, respectively.ConclusionsRadiological signs suggestive of infection were uncommon. Radiolucency and periosteal reaction were associated with infection, though with low sensitivity.

Microbiological diagnosis of polymicrobial periprosthetic joint infection revealed superiority of investigated tissue samples compared to sonicate fluid generated from the implant surface

ObjectivesIn the microbiological diagnosis of periprosthetic joint infection (PJI), there is much discussion about the methodology of obtaining proper specimens, the processing technique, and suitable culture media. This retrospective study was conducted to analyse the accuracy of our culture techniques. MethodsTissue samples and components from 258 patients after revision arthroplasty of the hip, knee, and shoulder were investigated, and the results of tissue cultures (TC) were compared to those of sonicate fluid cultures (SFC). Furthermore, an evaluation was performed of the influence of different culture media on the detection rate. ResultsPJI was confirmed in 186 patients. The overall sensitivity of TC was no different to that of SFC (91.3% vs 90.8%, P = 1). In 153 cases (82.3%), TC and SFC showed concordant positive results. Results were discordant in 33 cases (17.7%). When differentiated according to the type of infection, TC showed significantly better results than SFC in detecting polymicrobial infections (97.0% vs 67.0%, P = 0.004). There were also significant differences between the culture media regarding the yield of microorganisms. ConclusionsTC was more effective in detecting co-infections. The best results were obtained using both TC and SFC. The choice of culture media has a significant influence on the quality of results.

Does preoperative antibiotic prophylaxis affect sonication-based diagnosis in implant-associated infection?

As culture-negative implant-associated infection denote a diagnostic challenge, sonicate fluid cultures of the explanted endoprosthesis and osteosynthesis components are frequently used. However, the effect of antibiotic treatment on pathogen detection by sonication fluid cultures in implant-associated infection has not been investigated. Thus, the aim of this study was to evaluate the influence of preoperative antibiotic prophylaxis (PAP) and antibiotic therapy (AT) on sonicate fluid cultures in patients with implant-associated infection. In this retrospective study three groups were compared: (i) standard PAP, (ii) AT for at least one day, and (iii) no antibiotics before surgery. For the inclusion criteria, an established diagnostic protocol for implant-associated infection was used. Sonicate fluid cultures were validated by corresponding microbiological and histopathological samples. In 90 patients with single and multiple infections, 114 pathogens were detected. The detection rate by sonicate fluid cultures in patients receiving PAP (n = 27, 29 pathogens), AT before surgery (n = 33, 48 pathogens) and no antibiotics before surgery (n = 30, 37 pathogens) were 86.2%, 81.3%, and 86.5% (p = .778), respectively. Eleven of 114 infectious agents were detected exclusively by sonicate fluid cultures, while conventional tissue culture failed in these cases. PAP and AT do not affect intraoperative cultures in implant-associated infection. It is therefore not recommended to omit antibiotic prophylaxis in patients with implant-associated infection. Algorithms including both sonicate fluid cultures and tissue samples should be used for appropriate microbiological diagnosis of implant-associated infections.

Development of a large animal rabbit model for chronic periprosthetic joint infection.

AimsPeriprosthetic joint infections (PJIs) and osteomyelitis are clinical challenges that are difficult to eradicate. Well-characterized large animal models necessary for testing and validating new treatment strategies for these conditions are lacking. The purpose of this study was to develop a rabbit model of chronic PJI in the distal femur.MethodsFresh suspensions of Staphylococcus aureus (ATCC 25923) were prepared in phosphate-buffered saline (PBS) (1 × 109 colony-forming units (CFUs)/ml). Periprosthetic osteomyelitis in female New Zealand white rabbits was induced by intraosseous injection of planktonic bacterial suspension into a predrilled bone tunnel prior to implant screw placement, examined at five and 28 days (n = 5/group) after surgery, and compared to a control aseptic screw group. Radiographs were obtained weekly, and blood was collected to measure ESR, CRP, and white blood cell (WBC) counts. Bone samples and implanted screws were harvested on day 28, and processed for histological analysis and viability assay of bacteria, respectively.ResultsIntraosseous periprosthetic introduction of planktonic bacteria induced an acute rise in ESR and CRP that subsided by day 14, and resulted in radiologically evident periprosthetic osteolysis by day 28 accompanied by elevated WBC counts and histological evidence of bacteria in the bone tunnels after screw removal. The aseptic screw group induced no increase in ESR, and no lysis developed around the implants. Bacterial viability was confirmed by implant sonication fluid culture.ConclusionIntraosseous periprosthetic introduction of planktonic bacteria reliably induces survivable chronic PJI in rabbits.Cite this article: Bone Joint Res 2021;10(3):156–165.

Sonication improves microbiologic diagnosis of periprosthetic elbow infection.

Periprosthetic joint infection (PJI) is a relatively frequent and oftentimes devastating complication after total elbow arthroplasty (TEA). Its microbiologic diagnosis is usually based on periprosthetic tissue culture (hereafter referred to as tissue culture), but the sensitivity of tissue culture is variable. Although implant sonication culture has been shown to be superior to tissue culture for the diagnosis of hip and knee PJI, only a single small study (of fewer than 10 infected implants) has assessed sonication for PJI diagnosis after elbow arthroplasty. We retrospectively analyzed 112 sonicate fluid cultures from patients who underwent revision of a TEA at a single institution between 2007 and 2019, comparing results to those of tissue cultures. We excluded patients who had fewer than 2 tissues submitted for culture. Using the Infectious Diseases Society of America guidelines to define PJI, there were 49 infected and 63 non-infected cases. Median ages in the PJI and non-infected groups were 66 and 61 years, respectively. In the non-infected group, 65% were female vs. 63% in the PJI group. We reviewed clinical characteristics and calculated the sensitivity and specificity of tissue compared with sonicate fluid culture. In addition, we compared the sensitivity of tissue culture to the combination of tissue and sonicate fluid culture. The most common pathogens were coagulase-negative Staphylococcus sp (49%), followed by Staphylococcus aureus (12%). Sensitivity of tissue culture was 63%, and sensitivity of sonicate fluid culture was 76% (P = .109). Specificity of tissue culture was 94% and specificity of sonicate fluid culture was 100%. Sensitivity of sonicate fluid culture in combination with tissue culture was 84% (P = .002 compared to tissue culture alone). In this study, we found that the combination of sonicate fluid and tissue culture had a greater sensitivity than tissue culture alone for microbiologic diagnosis of PJI after TEA.

The yield of sonication fluid culture for presumed aseptic loosening of orthopedic devices: a meta-analysis

Sonication fluid culture is routinely conducted in patients with suspected orthopedic devicerelated infection (ORI). However, its value in the assessment of orthopedic devices that have explanted because of presumed aseptic loosening is still debatable. A meta-analysis was conducted to estimate the yield of sonication fluid culture in detecting the presence of microorganisms in orthopedic devices with presumed aseptic loosening, and to summarize the clinical characteristics and outcomes of these patients. A meta-analysis was performed of peer-reviewed publications detailing the characteristics of patients whose orthopedic devices were explanted for presumed aseptic loosening and who underwent subsequent sonication fluid culture. Diagnostic data were extracted and pooled to estimate the yield of sonication fluid culture for detecting the presence of microorganisms with 95% confidence intervals (CI). Eight studies involving 421 patients were included in the meta-analysis analysis. The pooled results showed that sonication fluid culture had a yield of approximately 30% (95% CI: 20-41%) for identifying the presence of microorganisms in presumed aseptic loosening of orthopedic devices; this yield was higher than that of intraoperative tissue culture (22%, 95% CI: 8-41%) and aspirated fluid culture (13%, 95% CI: 7-21%). Sonication and vortexing for ≤5 min had a detection rate of 49% (95% CI: 43-55%), which exceeded that of >5 min. Coagulase-negative Streptococcus accounted for 74% (95% CI: 51-92%) of the isolated microorganisms. However, patients with positive microbiological results of sonication fluid culture and those with negative results showed similar outcomes after revision surgery. Colonization of low-virulent microorganisms may exist in a considerable number of patients with clinically presumed aseptic loosening of orthopedic devices. When this occurs, sonication (1-5 min at 40 kHz) of fluid culture could act as a sensitive diagnostic tool. However, the question of whether sonication fluid culture should be integrated into the routine treatment of loosened orthopedic devices requires further investigation.

Implant sonication versus intraoperative tissue sample cultures for Periprosthetic Joint Infection (PJI) of Shoulder Arthroplasty.

Introduction:Periprosthetic joint infection (PJI) is the most problematic complications after shoulder arthroplasty. Many diagnostic tools have been identified to find infection, such as hystopatologic examination of tissue sections or cultures of intraoperative tissue. Implant sonication fluid culture showed good results in order to enhance diagnostic accuracy, but literature results are still controversial. Aim of our study is to compare the results of sonication with intraoperative tissue sample cultures.Patients and Methods:From February 2016 to January 2018 we performed 102 revisions of Total Shoulder Arthroplasty (TSA) for suspected PJI. Sixty - five patients respected the criteria for admission to the study and were enrolled. In each case periprostethic specimens were collected and explanted prosthesis were put inside sterile fluid, sonicated and then placed under culture.Results:Among the sixty-five patients, 36 were considered as possible, probable or certain infection. Tissue cultures were positive for infection in thirty - four cases (52,3%) and in nineteen cases was found the positivity for Cutibacterium acnes. Sonication fluid cultures were positive in forty cases (61,5%), with a positivity for Cutibacterium acnes in twenty - seven cases. The sensitivities of sonication and tissue cultures for the diagnosis of shoulder PJI were 83.3% and 88,9% (P = 0,08); the specificities were 65.5% and 93,1% (P < 0.01) respectively.Conclusion:Our results suggest that sonication technique had not shown a clear advantage in postoperative shoulder PJI diagnosis, but it’s a real aid to detect Cutibacterium acnes. In any case, sensitivity and mostly specificity were higher with tissue cultures. (www.actabiomedica.it)

324. Implant Sonication Improves Microbiologic Diagnosis of Elbow Prosthetic Joint Infection

BackgroundWith a reported incidence of up to 12%, periprosthetic joint infection (PJI) is a frequent complication of total elbow arthroplasty (TEA). Its microbiologic diagnosis is usually based on periprosthetic tissue culture (hereafter referred to as tissue culture), despite the poor sensitivity of this technique. Although implant sonication cultures have been shown to be superior to tissue cultures for hip and knee PJI diagnosis, only a single small study (including fewer than 10 infected implants) has assessed sonication of elbow arthroplasties.MethodsWe retrospectively analysed 116 sonicate fluid cultures from patients who underwent revision of a TEA at our Institution between 2007 and 2019, comparing results to tissue cultures. Nine elbows who had fewer than 2 tissue samples obtained during surgery were excluded. Using the IDSA guidelines to define PJI, there were 46 infected cases and 61 aseptic failures. We reviewed clinical characteristics and calculated the sensitivity and specificity of periprosthetic tissue culture compared to culture of samples obtained by implant sonication. In addition, we compared the sensitivity of tissue culture to the combination of tissue and sonicate fluid culture.ResultsA total of 107 elbows were included. Median ages in the aseptic failure and PJI groups were 60 and 67 years, respectively. Gender distribution was similar for both groups (PJI group 62% females; aseptic group 65% females). The most common pathogens were coagulase negative Staphylococcus species (66%), followed by Staphylococcus aureus (18%). The sensitivity of tissue culture was 63% and the sensitivity of sonicate fluid culture was 76% (p=0.14). The specificity of tissue culture was 86% and the specificity of sonicate fluid culture was 100%. Sensitivity of sonicate fluid culture in combination with tissue culture was 91% (p=0.045).Table. Comparison of tests for microbiologic diagnosis of PJI ConclusionThe combination of sonicate fluid culture and tissue culture had a greater sensitivity than tissue culture alone for microbiologic diagnosis of elbow TEA infection.Disclosures Joachin Sanchez-Sotelo, M.D, PhD, Elsevier (Other Financial or Material Support, Publishing Royalties)Exactech (Consultant)Oxford Univerity Press (Other Financial or Material Support, Publishing Royalties)Stryker (Grant/Research Support)Wright (Consultant) Robin Patel, MD, Accelerate Diagnostics (Grant/Research Support)CD Diagnostics (Grant/Research Support)Contrafect (Grant/Research Support)Curetis (Consultant)GenMark Diagnostics (Consultant)Heraeus Medical (Consultant)Hutchison Biofilm Medical Solutions (Grant/Research Support)Merck (Grant/Research Support)Next Gen Diagnostics (Consultant)PathoQuest (Consultant)Qvella (Consultant)Samsung (Other Financial or Material Support, Dr. Patel has a patent on Bordetella pertussis/parapertussis PCR issued, a patent on a device/method for sonication with royalties paid by Samsung to Mayo Clinic, and a patent on an anti-biofilm substance issued.)Selux Dx (Consultant)Shionogi (Grant/Research Support)Specific Technologies (Consultant)

Highly variable effect of sonication to dislodge biofilm-embedded Staphylococcus epidermidis directly quantified by epifluorescence microscopy: an in vitro model study

BackgroundIn cases of prosthetic joint infections, culture of sonication fluid can supplement culture of harvested tissue samples for correct microbial diagnosis. However, discrepant results regarding the increased sensitivity of sonication have been reported in several studies. To what degree bacteria embedded in biofilm are dislodged during the sonication process has to our knowledge not been fully elucidated. In the present in vitro study, we have evaluated the effect of sonication as a method to dislodge biofilm by quantitative microscopy.MethodsWe used a standard biofilm method to cover small steel plates with biofilm forming Staphylococcus epidermidis ATCC 35984 and carried out the sonication procedure according to clinical practice. By comparing area covered with biofilm before and after sonication with epifluorescence microscopy, the effect of sonication on biofilm removal was quantified. Two series of experiments were made, one with 24-h biofilm formation and another with 72-h biofilm formation.Confocal laser scanning microscopy (CLSM) and scanning electron microscopy (SEM) were used to confirm whether bacteria were present after sonication. In addition, quantitative bacteriology of sonication fluid was performed.ResultsEpifluorescence microscopy enabled visualization of biofilm before and after sonication. CLSM and SEM confirmed coccoid cells on the surface after sonication. Biofilm was dislodged in a highly variable manner.ConclusionThere is an unexpected high variation seen in the ability of sonication to dislodge biofilm-embedded S. epidermidis in this in vitro model.

Microbiological diagnosis of intramedullary nailing infection: comparison of bacterial growth between tissue sampling and sonication fluid cultures.

Intramedullary nailing (IMN) has been frequently indicated to treat long bone open and closed fractures, but IMN infection (IMNI) may have devastating consequences. Sonication has been regarded as an important add-on for microbial identification on a variety of orthopaedic implant-associated infections, but its role in the IMNI is poorly studied. We aim at evaluating the accuracy obtained by conventional peri-implant tissue culture (TC) samples with sonication fluid cultures (SCs) of IMNI. Longitudinal prospective cohort study ongoing since June 2014, which included patients with indication for IMN removal due to any reason. Clinical diagnosis of INMI was defined according to publication addressing fracture-related infections. Minimal of two samples from TC were cultured. SCs followed the protocol previously published. Statistical analysis was performed using McNemar's test for related proportions. We included 54 patients submitted to IMN retrieval, of whom 47 presenting clinical signs of IMNI. Sensitivity for detecting microorganisms using TC and SC was 89.4% (42/47) and 97.6% (40/41), and specificity was 71.4% (5/7) for both TC and SC (p = 1.00). Positive and negative predictive values for TC and SC were 95.5% (42/44), 95.2% (40/42), 50% (5/10), and 83.3% (5/6), respectively. The most frequent organisms isolated in both TC and SC were Staphylococcus aureus, S. epidermidis, and Enterococcus sp. Polymicrobial infection was diagnosed in 14.8% (8/54) and 25% (12/48) by TC and SC, respectively (p = 0.19). Sonication fluid and tissue samples presented similar accuracy on the diagnosis of IMNI, but SC was advantageous of detecting polymicrobial infection.

A comparative study of heterogeneous antibiotic resistance of microbial populations in conventional periprosthetic tissue cultures and sonication fluid cultures of orthopaedics explanted prostheses.

"Heterogeneity" describes a phenomenon where subpopulations of seemingly isogenic bacteria exhibit a range of susceptibilities to a particular antibiotic. We aim to investigate the frequency of heterogeneity among microbes isolated from infected prostheses, and its possible correlation with microbial resistance. Between May 2014 and June 2019, we investigated 234 patients, at our institution, undergoing revision arthroplasty because of loosening of the prostheses or because of periprosthetic joint infection. All patients had periprosthetic tissue culture, sonication of prosthesis and direct inoculation of Sonication fluid into blood culture bottles. We assessed the presence of heterogeneity among all pathogens isolated from infected prostheses. Using standard non-microbiological criteria to determine periprosthetic joint infection, it was found that 143 patient (61.1%) had aseptic loosening while 91 patients (38.9%) had periprosthetic joint infection. Comparing the two methods, the results of our study showed that the method of sonication was significantly more sensitive than tissue culture [91% (83-96) vs. 43% (33-54); p < 0.005]. In this study, heterogeneity was reported in 15 cases, 16.5% of all infections and 6.4% in the total population. In our study, Staphylococcus epidermidis was the most commonly isolated strain followed by Staphylococcus aureus, at a rate of 35.2% and 19.8%, respectively. Antibiotics in which the microorganisms exhibited heterogeneous bacterial behavior most frequently were Gendamicin (5.3%), Vancomycin (4.9%). There is increasing evidence that heterogeneity can lead to therapeutic failure and that the detection of this phenotype is a prerequisite for a proper antibiotic choice to have a successful therapeutic effect.

The Performance of a Dithiothreitol-Based Diagnostic System in Diagnosing Periprosthetic Joint Infection Compared to Sonication Fluid Cultures and Tissue Biopsies.

The aim of this study was to evaluate the performance of a commercially available dithiothreitol (DTT) kit for routine use in diagnosing periprosthetic joint infections (PJIs) in comparison to conventional microbiological tissue specimens and sonication procedures in a maximal care hospital. We applied the DTT system in 40 consecutive cases of revision arthroplasty (23 PJIs and 17 aseptic revisions), with an exchange or a removal of components. The hardware components were split between the DTT system and the conventional sonication procedure. At least three tissue biopsies and a joint fluid specimen were sent for microbiological and histopathological analysis. Data was analysed retrospectively to compare between the different methods. Cultures of the DTT fluid showed a sensitivity of 65% and specificity of 100%, as referenced to conventional microbiological cultures. Sonication had better sensitivity (75%) but lower specificity (85%). The categorical agreement of DTT cultures compared to sonication fluid cultures was 78% (31/40). Neither pathogen type, infection duration nor antibiotic pretreatment influenced the accuracy of the DTT, but a low pH in the DTT seemed to be associated with false-negative results. DTT was inferior in sensitivity when diagnosing PJIs compared to sonication fluid cultures and tissue biopsies. A low pH in the DTT fluid correlated with false-negative results. Nevertheless, the closed system of the DTT kit avoids contamination and false-positive results, and DTT can be an alternative where sonication is not available.

Sonication Leads to Clinically Relevant Changes in Treatment of Periprosthetic Hip or Knee Joint Infection.

Background: Diagnosis of periprosthetic joint infection (PJI) can be troublesome. Sonication can be a helpful tool in culturing bacteria that are difficult to detect with standard tissue cultures. Aim of this study is to evaluate the clinical importance of our standardized sonication protocol in detecting periprosthetic joint infection.Materials and methods: All patients with revision surgery of a hip or knee prosthesis between 2011 and 2016 were retrospectively reviewed and divided in two groups: clinically suspected of infection or not suspected of infection. For both tissue culture and implant sonication, calculations of sensitivity and specificity were performed. Clinical relevance of sonication was evaluated by calculating in which percentage of patients' sonication influenced clinical treatment.Results: 226 patients with revision of a total hip prosthesis (122 patients) or a total knee prosthesis (104 patients) were included. Sensitivity of perioperatively taken tissue cultures was 94.3% and specificity was 99.3%. For sonication sensitivity was 80.5% and specificity was 97.8%.In the infection group eight patients (9%) with only one positive tissue culture and a positive sonication fluid culture with the same pathogen were found.Interpretation: Although sensitivity and specificity of sonication was lower compared to tissue cultures, periprosthetic joint infection could only be established in 8 patients (9%) suspected of infection because of a positive result of the sonication fluid culture.Sonication leads to clinically relevant changes in treatment and seems therefore to be a helpful diagnostic tool in clinical practice.

Establishment of an in vivo rat model for chronic musculoskeletal implant infection

BackgroundThe aim of the study was to establish an experimental chronic musculoskeletal infection model in vivo characterized by (a) a small bacterial inoculum, (b) no general or local signs of infection, (c) several parallels (implants) in each animal and finally (d) a model that is technically easy to perform.MethodsBone xenografts with steel plates were implanted intramuscularly in rats. To the xenografts, different inocula of Staphylococcus aureus and two strains of Staphylococcus epidermidis were added. The animals were observed for different time periods before the removal of the xenografts. The xenografts and steel plates were subjected to quantitative bacterial culture after sonication. Additional steel plates were subjected to scanning electron microscopy (SEM) for visualization of biofilm formation.ResultsInoculation of bone grafts with S. aureus did produce a pyogenic infection in all animals. A chronic infection was established in rats where the bone grafts were inoculated with S. epidermidis. A bacterial inoculum of 100 colony-forming units (CFU) of S. epidermidis was adequate as a minimum infective dose. During a period of up until 42 days, the animals infected with S. epidermidis had no general or local signs of infection. According to the results of the quantitative bacterial culture of sonicate fluid and SEM, a biofilm was developed on all implants.ConclusionIn the present in vivo model, a very small bacterial inoculum succeeded in establishing a chronic musculoskeletal implant infection where a biofilm was formed on the implants. The experimental model is easy to perform and allows several implants in each animal. The model could be useful for the study of biofilm formation in vivo on different implants and different surfaces.

Patient-Related Factors Affecting the Sensitivity of Sonication of Removed Hip and Knee Implants Against Conventional Tissue Cultures for Diagnosis of Prosthetic Joint Infections

Despite its decreasing incidence, prosthesis-related infections remain a research, diagnostic, therapeutic and cost-related problem. Our study aim was to compare the diagnostic accuracy of conventional periprosthetic tissue culture and culture of sonication fluid of the explanted hardware and to investigate the role of patientrelated factors affecting the sensitivity of the sonication method. We investigated 70 patients undergoing revision hip or knee arthroplasty, at our institution. Patients’ medical history and demographic characteristics were recorded. We compared the culture of samples obtained by sonication of explanted hip and knee prostheses with conventional culture of periprosthetic tissue for the microbiological diagnosis of prosthetic-joint infection. Thirty-two patients had septic loosening and 38 aseptic loosening (48 hip prostheses and 22 knee prostheses). The sensitivities of sonication fluid culture and conventional tissue cultures were 81.25% and 56.25%, respectively (p-value = 0.043). The sensitivity of the sonication method was statistically higher in obese, diabetic patients, with age above 60, in uncemented arthroplasties and in arthroplasties because of primary osteoarthritis (p-values &lt; 0.05). The sonication method has a greater sensitivity than the conventional periprosthetic tissue cultures for the periprosthetic infections, especially in obese, diabetic patients, with age above 60, in uncemented arthroplasties and in arthroplasties because of primary osteoarthritis.

The role of implant sonication in the diagnosis of periprosthetic shoulder infection

The aim of this study was to investigate the validity of implant sonication fluid cultures in the diagnosis of shoulder periprosthetic joint infection (PJI) compared with tissue culture. This was a retrospective case-control study analyzing all patientswho underwent a revision surgery for any kind of suspected septic or aseptic event due to failed shoulder arthroplasty at our institution between July 2014 and December 2018. The diagnostic validity of implant sonication was analyzed on the basis of the last proposed definition criteria of the International Consensus Meeting and compared with standard tissue cultures. Of the 72 patients, a total of 28 (38.9%) were classified as infected. Of the 28 infected patients, 20 (71.4%) had an identified organism by tissue cultures, and Cutibacterium acnes was the most commonly isolated pathogen. The sensitivities of sonicate fluid (≥50 CFU/mL) and periprosthetic tissue culture for the diagnosis of periprosthetic shoulder infection were 36% and 61% (P = .016), and the specificities were 97.7% and 100% (P > .99), respectively. If no cutoff value was used in sonication culture, the sensitivity increased to 75% whereas the specificity dropped to 82%. Although there was no significant difference in sensitivity between tissue culture and the no-cutoff sonication fluid culture (61% vs. 75%, P = .125), the specificity of tissue culture was significantly higher (100% vs. 82%, P= .01). Tissue culture showed a higher sensitivity and specificity than implant sonication in the diagnosis of shoulder PJI and should remain the gold standard for microbiological diagnosis of shoulder PJI.