Is an isolated positive sonication fluid culture in revision arthroplasties clinically relevant?

OBJECTIVES

The aim of this study was to investigate the clinical relevance of an isolated positive sonication fluid culture (SFC) in patients who underwent revision surgery of a prosthetic joint. We hypothesized that cases with a positive SFC have a higher rate of infection during follow-up compared with controls with a negative SFC.

METHODS

This retrospective multicentre observational study was performed within the European Study Group of Implant-Associated Infections. All patients who underwent revision surgery of a prosthetic joint between 2013 and 2019 and had a minimum follow-up of 1 year were included. Patients with positive tissue cultures or synovial fluid cultures were excluded from the study.

RESULTS

A total of 95 cases (positive SFC) and 201 controls (negative SFC) were included. Infection during follow-up occurred in 12 of 95 cases (12.6%) versus 14 of 201 controls (7.0%) (p = 0.125). In all, 79.8% of cases were with treated with antibiotics (76/95). Of the non-treated cases, 89% (17/19) had a positive SFC with a low virulent microorganism. When solely analysing patients who were not treated with antibiotics, 16% of the cases (3/19) had an infection during follow-up versus 5% of the controls (9/173) (p = 0.08).

DISCUSSION

Although not statistically significant, infections were almost twice as frequent in patients with an isolated positive SFC. These findings require further exploration in larger trials and to conclude about the potential benefit of antibiotic treatment in these cases.

An Observational Prospective Clinical Study for the Evaluation of a Collagen-Hydroxyapatite Composite Scaffold in Hip Revision Surgery

One of the greatest challenges of hip revision surgery is the need to restore extensive bone loss by creating a stable reconstruction with long-term durability. The present observational, investigator-initiated prospective study was carried out to evaluate the clinical and radiological results of the use of a commercial biomimetic collagen-hydroxyapatite composite biomaterial (RegenOss) applied in hip revision surgery. Thirty-three patients who underwent hip revision were included in this study, and 29 received up to 2 years of follow-up. The acetabulum was reconstructed using an uncemented hemispherical shell both with or without an iliac fixation stem. Functional recovery was assessed according to the Harris Hip Score (HHS) at the pre-hospitalisation check-up, and at 6-, 12-, and 24-month follow-ups. Radiological evaluation consisting of X-ray analyses (6, 12, and 24 month follow-ups) and CT scan exams (within 10 weeks post-surgery and at 12-month follow-up) were performed to evaluate the reduction in bone defect and new bone regeneration. All the patients reported a complete recovery and a considerable improvement in functional outcome assessed by the HHS, which was significantly higher at all the follow-ups than at pre-hospitalisation. Moreover, radiological assessments revealed good scaffold integration. Overall, collected data suggest that RegenOss is a valid and safe alternative to restoring acetabular bone loss in revision hip arthroplasty.

Demineralized bone matrix paste formulated with biomimetic PLGA microcarriers for the vancomycin hydrochloride controlled delivery: Release profile, citotoxicity and efficacy against S. aureus

Infection and resulting bone defects caused by Staphylococcus aureus is one of the major issues in orthopaedic surgeries. Vancomycin hydrochloride (VaH) is largely used to manage these events. Here, a human derived bone paste supplemented with biopolymer microcarriers for VaH sustained delivery to merge osteoinductive and antimicrobial actions is described. In detail, different emulsion formulations were tested to fabricate micro-carriers of poly-lactic-co-glycolic acid (PLGA) and hydroxyapatite (HA) by a proprietary technology (named Supercritical Emulsion Extraction). These carriers (mean size 827 ± 68 μm; loading 47 mg_VaH/g_PLGA) were assembled with human demineralized bone matrix (DBM) to obtain an antimicrobial bone paste system (250 mg/0.5 cm³ w/v, carrier/DBM). Release profiles in PBS indicated a daily drug average release of about 4 µg/mL over two weeks. This concentration was close to the minimum inhibitory concentration and able to effectively inhibit the S. aureus growth in our experimental sets. Carriers cytotoxicity tests showed absence of adverse effects on cell viability at the concentrations used for paste assembly. This approach points toward the potential of the DBM-carrier-antibiotic system in hampering the bacterial growth with accurately controlled antibiotic release and opens perspectives on functional bone paste with PLGA carriers for the controlled release of bioactive molecules.

Various biofilm matrices of the emerging pathogen Staphylococcus lugdunensis: exopolysaccharides, proteins, eDNA and their correlation with biofilm mass

Staphylococcus lugdunensis is an emerging high-virulent pathogen causative of hospital-acquired infections. Biofilm formation is a complex pathogenic process that leads to well-established bacterial communities. There is a paucity of data on the composition of the biofilm matrix among S. lugdunensis strains. Here, twenty-two S. lugdunensis clinical isolates, mainly from orthopaedic infections but also from other clinical sources, were sub-grouped by ribotyping and dendrogram analysis. Biofilms were analysed by fluorimetric methods based on FITC-Wheat Germ Agglutinin, SYPRO Ruby and TOTO-1 dyes to detect exopolysaccharides, proteins and extracellular DNA (eDNA), respectively. Biofilm morphology was investigated under confocal laser scanning microscopy (CLSM). Isolates displayed intriguing diversities in biofilm mass and matrix composition. The content of exopolysaccharides was found to be to be strongly associated with the biofilm mass (R² = 0.882), while the content of proteins turned out to be weakly (R² = 0.465) and that of eDNA very weakly associated (R² = 0.202) to the biofilm mass.

Sonication Improves the Diagnosis of Megaprosthetic Infections

Limited data are available for the diagnosis of patients with tumors with infected endoprosthetic reconstructions. The purpose of this study was to evaluate whether sonication is effective for the diagnosis of infection and to compare it with tissue cultures. The files of 58 patients who underwent revision surgery for suspected infected endoprosthetic reconstructions were reviewed. Cultures were performed on 5 tissue samples obtained from each patient and on fluid obtained by sonication of the megaprosthesis. The sensitivity, specificity, and negative and positive predictive values of tissue and sonication fluid cultures were evaluated. Overall, tissue and sonication fluid cultures confirmed an infection in 42 of the 58 patients. In 36 of the 42 infected endoprosthetic reconstructions, tissue and sonication fluid cultures identified the same bacterial isolate. In 5 cases, a bacterial isolate was identified only in sonication fluid cultures, and in 1 case, a bacterial isolate was identified only in tissue cultures. The sensitivity and negative predictive value of sonication fluid cultures were statistically significantly better than those of tissue cultures, while the specificity and positive predictive value were not different between the 2 culture types. Compared with tissue cultures for the diagnosis of infected megaprostheses in patients with tumors, sonication fluid cultures are associated with a better sensitivity and negative predictive value and a similar specificity and positive predictive value. Therefore, sonication should be considered a useful adjunct for the optimal diagnosis and management of these patients. [Orthopedics. 2019; 42(1):28-32.].

Characterization of 26 Staphylococcus warneri isolates from orthopedic infections

Staphylococcus warneri is a coagulase negative Staphylococcus (CNS) commonly present in the flora of human epithelia and mucosal membranes. Over the last two decades, similarly to other CNS species, S. warneri has been reported as a new emerging pathogen, capable of causing serious infections usually in association with the presence of implant materials, but, at times, even in the absence of a foreign body and in patients considered immunocompetent. At present, there is still a lack of scientific data on the pathogenesis and epidemiology of this species. The present study investigated a collection of 26 clinical isolates derived from orthopedic infections, some associated with implant materials and others not. Automated ribotyping showed the existence of 5 distinct ribogroups. Except for the least numerous ribogroup consisting of a single isolate, all other ribogroups included at least one strain obtained from an infection not associated with implant materials, suggesting that putative virulence factors necessary for infections even in the absence of a foreign body could be transversal to most ribogroup categories. Orthopedic infections were found to involve S. warneri strains with low antibiotic resistance potential, differing in this respect from the strains isolated at neonatal intensive care units, where this species has been described to figure among the principal causative agents and exhibit an alarming profile of antibiotic resistance.

Panton-Valentine Leukocidin Gene Detected in a Staphylococcus Aureus Strain Isolated from a Knee Arthroprosthesis Infection

This report focuses on the molecular characterization of a Staphylococcus aureus strain isolated from a knee arthroprosthesis infection and recognized retrospectively as a carrier of the Panton-Valentine leukocidin gene. The stored microbiological isolate, which belonged to the strain collection of the Research Unit on Implant Infections of the Rizzoli Orthopaedic Institute, was retrieved for molecular analysis. Genotyping was carried out, revealing an interesting profile. In addition to the positivity for the Panton-Valentine toxin gene, the results indicated that the isolate belonged to the agr III group and was endowed with bbp and cna genes, both encoding for staphylococcal adhesins that bind bone proteins. The strain had the mecA gene for methicillin resistance, even though it was unable to resist any of the β-lactam or other antibiotics. Its gene configuration matched that of other community-acquired methicillin-resistant and methicillin-susceptible Staphylococcus aureus (CA-MRSA and CA-MSSA) strains which have recently been reported worldwide. As far as we know, this is the first report on a PVL-positive S. aureus strain associated with an orthopedic implant (knee arthroprosthesis) infection.

Is Treatment With Dithiothreitol More Effective Than Sonication for the Diagnosis of Prosthetic Joint Infection?

BACKGROUND

Prosthetic joint infection (PJI) is among the most-severe complications of a total joint arthroplasty. Identification of the causal organism is of paramount importance for successful treatment, and sonication of implants may aid in this identification. Dithiothreitol (DTT) treatment has been proposed as an alternative to sonication to improve diagnosis, reduce costs, and improve reliability of the procedure, but its efficacy remains poorly characterized.

QUESTIONS/PURPOSES

(1) Are DTT and sonication more sensitive and/or more specific than standard cultures of tissue samples for the diagnosis of PJI? (2) Which test (DTT or sonication) is more sensitive when the clinician does not suspect infection before surgery? (3) Which test (DTT or sonication) is more sensitive when the clinician suspects infection before surgery?

METHODS

Two hundred thirty-two patients undergoing revision of a knee or hip arthroplasty were prospectively evaluated in this randomized study. Cultures were performed on five tissue samples from each patient and on fluid obtained by prosthesis treatment in patients randomly assigned to sonication (117 patients) or DTT (115 patients). The reference standard against which cultures (on tissue samples and on fluids from sonication or DTT) were compared was the Musculoskeletal Infection Society definition of PJI.

RESULTS

Cultures on sonication and DTT fluids provided higher sensitivity (89% and 91%, respectively) than those on standard cultures of tissue samples (79%; p < 0.001). Among patients in whom infection was not suspected before surgery, the sensitivity of DTT was greater than that for sonication and cultures on tissue samples (100% versus 70% and 50%; p < 0.001). Among patients in whom infection was suspected before surgery, the sensitivity of DTT and sonication were not greater than that for standard cultures (89% and 94% versus 86%).

CONCLUSIONS

In this randomized study, we found no difference in sensitivity between DTT and sonication for the detection of PJI, and both of those tests were more sensitive than standard tissue cultures. Thus, cultures of sonication or DTT fluid should be considered important additional tools to standard cultures for definition of PJI and should be considered together with other criteria, especially in settings where infection is not suspected before revision surgery.Level of Evidence Level I, diagnostic study.

Orthopedic implant infections: Incompetence of Staphylococcus epidermidis, Staphylococcus lugdunensis, and Enterococcus faecalis to invade osteoblasts

Septic failure is still the major complication of prosthetic implants. Entering host cells, bacteria hide from host immune defenses, shelter from extracellular antibiotics, and cause chronic infection. Staphylococcus aureus, the leading etiologic agent of orthopedic implant infections, is able to enter bone cells and induce osteoblast apoptosis, osteoclast recruitment, and highly destructive osteomyelitis. Staphylococcus epidermidis, Staphylococcus lugdunensis, and Enterococcus faecalis are opportunistic pathogens causative of implant-related infections. This study investigated the ability to internalize into osteoblastic MG63 cells of 22 S. epidermidis, 9 S. lugdunensis, and 21 E. faecalis clinical isolates from orthopedic implant infections. Isolates were categorized in clusters by ribotyping. Internalization assay was carried out by means of a microtiter plate-based method. S. epidermidis, S. lugdunensis, and E. faecalis strains turned out incompetent to enter osteoblasts, exhibiting negligible internalization into MG63 cells, nearly three orders of magnitude lower than that of S. aureus. Osteoblast invasion does not appear as a pathogenetic mechanism utilized by S. epidermidis, S. lugdunensis, or E. faecalis for infecting orthopedic implants. Moreover, it can be inferred that intracellularly active antimicrobials should not be necessary against implant infections caused by the three bacterial species. Finally, implications with the uptake of biomaterial microparticles by nonphagocytic cells are enlightened. © 2015 Wiley Periodicals, Inc. J Biomed Mater Res Part A: 104A: 788-801, 2016.

Use of sodium hypochlorite for skin antisepsis before inserting a peripheral venous catheter: a pilot study

Although it can be prevented, catheter-related bacteremia is common and dangerous. The antiseptics most widely used during insertion of peripheral venous catheters (PVCs) include povidone iodine, alcohol, and chlorhexidine. Another widely used antiseptic is a solution of 0.057 g sodium hypochlorite. This pilot study explored the contamination rate of the PVC tip inserted after skin decontamination with sodium hypochlorite. Culture analysis of the tips of the PVCs inserted into the 42 participants showed 7 (16.7%) colonized catheters. The results of this pilot study suggest taking into serious consideration the assessment of this antiseptic in randomized experimental studies.

A novel DNA profiling application for the monitoring of cross-contamination in autologous chondrocyte implantation

BACKGROUND

Autologous chondrocyte implantation (ACI) is a cell-based treatment that can be used to regenerate chondral defects. European legislation specifically classifies such produced chondrocytes as "medicinal for advanced cell therapy" that have to be manufactured in pharmaceutical factories according to specific rules, named Good Manufacturing Practices (GMPs). One main requirement of cell manipulation in advanced therapy is to prevent the risk of any contamination.

AIM

The aim of this study was to verify if chondrocyte cultures suitable for ACI were free of cross-contamination by means of DNA profiling techniques.

MATERIALS AND METHODS

Cell cultures were carried on in a Hospital Cell Factory in compliance with European current Good Manufacturing Practices. DNA profiling, by means of Short Tandem Repeats and miniShort Tandem Repeats analyses, was performed on expanded chondrocytes and their related control blood samples. Mitochondrial DNA was analysed to further confirm the results and to evaluate possible mutations occurred in the samples.

RESULTS

Our findings demonstrated the absence of cross-contamination between chondrocyte cultures and, thus, their identity maintenance until the end of the manipulation.

CONCLUSIONS

DNA profiling technique can be a suitable test for quality control not only for chondrocyte manipulation, but for cell therapy in general.

[In vitro evaluation of bactericidal activity of an over-heated saturated dry atomized steam electro-medical device on inert contaminated surfaces]

Surface disinfection together with cleaning practises and aseptic procedures are established measures for effective prevention of infectious diseases reducing infection risks. In this study, we evaluated the bactericidal effectiveness in vitro of the electro-medical device Sani System, an over-heated saturated dry-steam disinfection system, against predetermined bacterial load dried on inert surfaces. In particular we have tested different materials, representative of operating rooms furnishing and walls commonly used in healthcare setting, with Staphylococcus aureus, Pseudomonas aeruginosa, Klebsiella pneumoniae, Acinetobacter baumannii. As a result of treatment, the mean bacterial load on all the test surfaces was reduced by a factor of 102 in the contact plate experimental study and by a factor of 10 in the total bioburden experimental study. The Sani System Polti proved to be efficacious in killing 100% of the bacteria in all experimental conditions, therefore it could help to reduce the risk of spreading nosocomial infections in healthcare facilities.

Bacterial contamination of musculoskeletal allografts

Based on the indications in the literature of the transmission of highly pathogenic bacteria in musculoskeletal allograft implants, the cultural results for allografts removed and implanted in conditions of asepsis between 1997 and 2000 in BTM were analyzed: 4014 allografts (3117 from a living donor, 897 from a cadaver) and 3479 implants (2191 with allografts from living donors and 1288 with allografts from cadavers). Explanted tissues: these were positive to culture in 292 out of 3117 (9.4%) allografts from living donors; the bacteria isolated showed low pathogenicity. Out of 897 allografts 117 cadaver donors bacteria with low pathogenicity were isolated in 68 (7.6%) and high pathogenicity in 12 (1.3%). Implants: cultures were positive in 116/2191 (5.3%) implants with allografts from living donors and in 55/1288 (4.3%) implants with allografts from cadavers. The bacteria isolated are the same as those shown in the explants. In living donors contamination is similar as regards incidence and type of microorganism to that observed in surgical theatres during routine surgery. Contamination seems to be greater in allografts removed from cadavers who died as a result of trauma, in the presence of positive hemocultures, prolonged catheterization and intubation, explantation of the pelvis and removal of several organs and tissues prior to musculoskeletal allograft.