Value of multiplex PCR for detection of antimicrobial resistance in samples retrieved from patients with orthopaedic infections

Background: The performance of multiplex PCR (mPCR) for detection of antimicrobial resistance from clinical isolates is unknown. We assessed the ability of mPCR to analyse resistance genes directly from clinical samples. Patients with orthopedic infections were prospectively included. Phenotypical and genotypical resistance was evaluated in clinical samples (synovial and sonication fluid) where identical pathogens were identified by culture and mPCR. Result: A total of 94 samples were analysed, including 60 sonication fluid and 34 synovial fluid samples. For coagulase-negative staphylococcus strains, mPCR detected resistance to oxacillin in 10 of 23 isolates (44%) and to rifampin in none of 6 isolates. For S. aureus isolates, detection rate of oxacillin and rifampin-resistance was 100% (2/2 and 1/1, respectively). Fluoroquinolone-resistance was confirmed by mPCR in all 3 isolates of Enterobacteriaceae, in enterococci resistance to aminoglycoside-high level was detected in 1 of 3 isolates (33%) and in streptococci resistance to macrolides/lincosamides in none of 2 isolates. The overall sensitivity for different pathogens and antimicrobials was 46% and specificity 95%, the median concordance was 80% (range, 57–100%). Full agreement was observed for oxacillin in S. aureus, vancomycin in enterococci, carbapenems/cephalosporins in Enterobacteriaceae and rifampin in Cutibacterium species. Conclusion: The overall sensitivity for detection of antimicrobial resistance by mPCR directly from clinical samples was low. False-negative mPCR results occurred mainly in coagulase-negative staphylococci, especially for oxacillin and rifampin. However, the specificity of mPCR was high and a positive result reliably predicted antimicrobial resistance. Including universal primers in the PCR test assay may improve the detection rate but requires additional sequencing step. Trial registration: www.clinicaltrials.gov No. NCT02530229, registered at 21 August 2015 (retrospectively registered)

Heterogeneous contributions of change in population distribution of body mass index to change in obesity and underweight NCD Risk Factor Collaboration (NCD-RisC)

From 1985 to 2016, the prevalence of underweight decreased, and that of obesity and severe obesity increased, in most regions, with significant variation in the magnitude of these changes across regions. We investigated how much change in mean body mass index (BMI) explains changes in the prevalence of underweight, obesity, and severe obesity in different regions using data from 2896 population-based studies with 187 million participants. Changes in the prevalence of underweight and total obesity, and to a lesser extent severe obesity, are largely driven by shifts in the distribution of BMI, with smaller contributions from changes in the shape of the distribution. In East and Southeast Asia and sub-Saharan Africa, the underweight tail of the BMI distribution was left behind as the distribution shifted. There is a need for policies that address all forms of malnutrition by making healthy foods accessible and affordable, while restricting unhealthy foods through fiscal and regulatory restrictions

The value of novel diagnostic methods in the diagnosis of periprosthetic joint infection and the complication rate after two-stage revision for periprosthetic hip infections

Background In recent years, attention has focused on novel diagnostic methods as alpha defensin and multiplex PCR (mPCR) for diagnosing periprosthetic joint infection. In addition, two stage revision is the most widely used surgical approach to manage periprosthetic hip infection (PHI). The aim of the first study was to evaluate the diagnostic value of qualitative (lateral flow) and quantitative (ELISA) alpha defensin test in patients with prosthetic failure and to compare both test methods among each other. In the second study, the performance of mPCR for genotypical resistance detection in microorganisms isolated from patients with implant-related infections was analysed. In the third study, the intra- and postoperative complications of a two-stage revision using resection arthroplasty during stages were investigated according to the length of the prosthesis free interval. Methods Study 1: In 71 patients with prosthetic failure, alpha defensin was determined in the aspirated synovial fluid using two different methods (qualitative and quantitative). The area under the curve (AUC) of each test was calculated and both AUCs were compared among each other using the z-test. Study 2: In 94 samples (60 sonication fluid, 34 synovial fluid) a comparison of phenotypical (culture) and genotypical resistance analysis (mPCR) was performed calculating the concordance. Study 3: According to the length of prosthesis-free interval, the 93 included patients were assigned to two groups (group 1 ≤ 10 weeks and group 2 > 10 weeks) and complication rates were compared using chi-squared test. The infection-free survival rate was calculated using Kaplan-Meier analysis. Results Study 1: The lateral flow test showed a sensitivity, specificity, and AUC of 46%, 98%, and 0.72, respectively; and the ELISA tests of 50%, 98%, and 0.74, respectively. There was no significant difference between both AUCs (p=0.566). Study 2: The sensitivity, specificity and concordance of the mPCR regarding genotypical susceptibility testing was 46%, 95%, and 80%, respectively. The concordance between phenotypical and genotypical susceptibility for biofilm-active agents was 84% for rifampin in Staphylococcus spp., and 89% for fluoroquinolone in Enterobacteriaceae. Study 3: Patients with a short interval showed less complications after reimplantation. At 24 months, the infection-free survival rate was 94% in group 1 and 86% in group 2 (p=0.058). Conclusion Due to the insufficient sensitivities of alpha defensin and mPCR, these tests cannot replace the established diagnostic test methods but may be useful as specific adjuncts. No difference between the qualitative and quantitative alpha defensin test was found. The complication rate (76%) of a two-stage revision with a prosthesis-free interval (resection arthroplasty) for PHI was high. Long intervals showed more complications. Therefore, short intervals (≤ 10 weeks) can be recommended between stages.Einleitung Neue Testmethoden wie alpha Defensin und das multiplex PCR (mPCR) System werden in den letzten Jahren zunehmend zur Diagnostik von periprothetische Gelenkinfektionen (PPI) herangezogen. Zudem zählt der zwei-zeitige Prothesenwechsel zu den am häufigsten eingesetzten operativen Therapieverfahren bei periprothetischen Hüftgelenkinfektionen (PHI). Das Ziel der ersten Studie war es, den diagnostischen Wert des qualitativen alpha Defensin Tests (Lateral flow Test) und des quantitativen alpha Defensin Tests (ELISA) in der Synovialflüssigkeit von Patienten mit Prothesenversagen zu untersuchen und miteinander zu vergleichen. In der zweiten Studie wurde die Genauigkeit der mPCR zur genotypischen Antibiotika-Resistenzbestimmung in Mikroorganismen von Patienten mit Implantat-assoziierten Infektionen evaluiert. In der dritten Arbeit wurden die intra – und postoperativen Komplikationen bei zwei-zeitigem Prothesenwechsel mit prothesen-freiem Intervall (Resektionsarthroplastie) zur Behandlung von PHI eruiert. Methodik Studie 1: Bei insgesamt 71 Patienten mit Prothesenversagen wurde die Synovialflüssigkeit qualitativ und quantitativ auf alpha Defensin untersucht. Für den Vergleich zwischen beiden Testmethoden wurden die Flächen unter den Kurven (AUCs) beider Methoden mittels z-Test verglichen. Studie 2: In 94 Proben (60 Sonikationsflüssigkeiten, 34 Synovialflüssigkeiten) wurde prospektiv ein Vergleich zwischen phänotypischer (Kultur) und genotypischer (mPCR) Resistenzbestimmung mit Hilfe von Konkordanz-Analysen durchgeführt. Studie 3: Abhängig von der Dauer des prothesen-freien Intervalls wurden die 93 eingeschlossenen Patienten in zwei Gruppen (Gruppe 1 ≤ 10 Wochen und Gruppe 2 > 10 Wochen) unterteilt und die Häufigkeit der Komplikationen mittels Chi-Quadrat Test verglichen. Zusätzlich wurde das infektionsfreie Überleben mit Hilfe von Kaplan-Meier Kurven analysiert. Ergebnisse Studie 1: Die Sensitivität, Spezifität und AUC des alpha Defensin lateral-flow Tests war 46%, 98% und 0.72; und des ELISA Tests 50%, 98% und 0.74. Es konnte kein signifikanter Unterschied zwischen beiden Testmodalitäten gefunden werden. Studie 2: Die Sensitivität, Spezifität und Konkordanz aller mittels mPCR durchgeführten genotypischen Resistenzbestimmungen war 46%, 95% und 80%. Die Übereinstimmung von genotypischer und phänotypischer Empfindlichkeit für Biofilm-aktive Substanzen war für Rifampicin bei Staphylokokken 84% und für Chinolone bei Enterobacteriaceae 89%. Studie 3: Patienten mit kurzem Intervall zeigten eine niedrigere Komplikationsrate nach Reimplantation. Das Infektions-freie Überleben nach 24 Monaten war in Gruppe 1 94% und in Gruppe 2 86% (p=0.058). Schlussfolgerung Aufgrund der geringen Sensitivitäten des alpha Defensins und der mPCR können diese Tests die etablierten diagnostischen Methoden nicht ersetzen und bei hoher Spezifität lediglich als zusätzliche Untersuchungen fungieren. Der Vergleich von qualitativem mit quantitativem alpha Defensin zeigte keinen Unterschied. Die Komplikationsrate nach zwei-zeitigem Prothesenwechsel mit prothesen-freiem Intervall (Girdlestone-Situation) zur Behandlung von PHI ist mit 76% hoch. Eine höhere Komplikationsrate wurde bei längerem Intervall beobachtet, weshalb ein kurzes Intervall (≤ 10 Wochen) zwischen Explantation und Reimplantation einer neuen Prothese empfohlen werden kann

Efficacy of different revision procedures for infected megaprostheses in musculoskeletal tumour surgery of the lower limb.

PURPOSE:The incidence of recurrent infections in patients following one or two stage revision for infected megaprostheses after resection of bone tumours was investigated. The difference between retaining at least one well fixed stem and a complete removal of the megaprosthesis during a two stage revision was also analysed. METHODS:627 patients who experienced a replacement of a musculoskeletal tumour by megaprostheses were recorded. An infection occurred in 83 of 621 patients available for follow-up. 61 patients underwent one stage revision, and 16 patients two stage revision for the first revision surgery. In the entire study period, two stage revision was performed 32 times (first, second, and third revision). RESULTS:The cumulative incidence analysis showed a reinfection probability after one stage revision of 18% at one year, 30% at two years, 39% at five years, 46% at ten years, and 56% at 15 years. After two stage revision, a reinfection probability of 28% at two years, and 48% at five years was calculated. Cumulative incidence curves did not differ significantly (Gray's test; p = 0.51) between one and two stage revision (with and without complete removal of the stems). In two stage revision (n = 32), a statistically significant difference in infection rates between patients treated with complete removal of the megaprosthesis (n = 18) including anchorage stems and patients with at least one retained stem (n = 14) was shown (Fisher's exact test, p = 0.029). CONCLUSION:Two stage revisions with complete removal of the megaprosthesis showed the best results among limb salvage procedures for the treatment of infected megaprosthesis

International Orthopaedics / Multiplex PCR Unyvero i60 ITI application improves detection of low-virulent microorganisms in periprosthetic joint infections

Purpose The aim of this study was to evaluate the pre-operative performance of an automated multiplex PCR (mPCR) system in patients with suspected periprosthetic joint infection (PJI). Methods Under sterile conditions, synovial fluid samples from patients with a suspected PJI were collected pre-operatively. One hundred eighty microliter of the aspirate was used for analysis in the mPCR. The remaining joint fluid was sent for microbiological analysis. PJI was diagnosed by using the Musculoskeletal Infection Society (MSIS) criteria. Total percentage agreement and Cohens kappa coefficient were calculated to measure overall agreement. Results Overall, 90 patients with a suspected PJI were included. Using MSIS criteria, 38 (42%) patients were classified as septic. Total percent agreement between mPCR and synovial fluid culture was 86% with a Cohens kappa of 0.68. The mPCR and synovial fluid culture showed sensitivities of 71% and 84%, respectively. Combined evaluation provided an even higher sensitivity of 92%. While Cutibacterium spp. were detected five times by mPCR, it could only be cultured once. A higher detection rate of CoNS by mPCR (n=7) compared to conventional culture (n=5) was also demonstrated. In comparison to synovial fluid culture, the mPCR missed Staphylococcus aureus five times. Conclusion With a moderate agreement between synovial fluid mPCR and culture, the mPCR system could be a useful adjunct in diagnosing a PJI pre-operatively. Due to faster availability of results and a higher detection rate of low-virulent microorganisms, it can complement conventional culture.(VLID)363848

The reinfection rate (RR) depending on the localisations of the megaprostheses and OP procedures.

<p>The reinfection rate (RR) depending on the localisations of the megaprostheses and OP procedures.</p

Comparison of the literature of the reinfection rates (RR) after 2-stage procedures.

<p>The follow-up period started after the first revision (m = months). In the series of Flint et al. and Grimer et al. (*patient survival 109m), it is not clear at which point in time follow up began.</p

Comparison of the literature of the reinfection rates (RR) after 1-stage procedures.

<p>The follow-up period started after the first revision (m = months).</p

The cumulative incidence of reinfection (continuous line) and death (dashed line) after one-stage revision.

<p>The cumulative incidence of reinfection (continuous line) and death (dashed line) after one-stage revision.</p

Flow chart of all patients with infection following a primary replacement of a musculoskeletal tumour of the lower limb and reconstruction by a megaprosthesis.

<p>Flow chart of all patients with infection following a primary replacement of a musculoskeletal tumour of the lower limb and reconstruction by a megaprosthesis.</p