Improved diagnosis of infection associated with osteosynthesis by use of sonication of fracture fixation implants

Microbial investigation of biofilms recovered from endotracheal tubes using sonication in intensive care unit pediatric patients

OBJECTIVES

To compare cultured microorganisms identified on endotracheal tubes biofilms through sonication technique with traditional tracheal aspirate collected at extubation of pediatric intensive care unit patients.

METHODS

Demographic and epidemiological data were analyzed to identify factors possibly related with the microbiological profile of the two collection methods. Associations between categorical and continuous variables were analyzed using the chi-square or Fisher's exact test, or Student's t test. p-Value <0.05 were considered significant.

RESULTS

Thirty endotracheal tubes and tracheal aspirates samples from 27 subjects were analyzed. Only one patient presented the clinical diagnosis of ventilator-associated pneumonia. Overall, 50% of bacteria were Gram-negative bacilli, followed by Gram-positive bacteria in 37%, and fungi in 10%. No statistically significant difference on the distribution of Gram-positive or Gram-negative bacteria (p=0.996), and fungi (p=0.985) were observed between the collection methods. Pseudomonas spp. was the most frequent microorganism identified (23.8%), followed by Streptococcus spp. (18.5%), Acinetobacter spp. (15.9%), coagulase-negative staphylococci (11.2%), and Klebsiella spp. (8.6%). Concordant results between methods amounted to 83.3%. Pseudomonas aeruginosa and Acinetobacter baumannii showed carbapenem resistance in 50% and 43.7% of the isolates, respectively. In general, cultures after endotracheal tubes sonication (non-centrifuged sonication fluid and centrifuged sonication fluid) yielded bacteria with higher rates of antimicrobial resistance compared to tracheal aspirates cultures. Additionally, in 12 subjects (40%), we observed discrepancies regarding microbiologic profiles of cultures performed using the collection methods.

CONCLUSIONS

Our study demonstrated that sonication technique can be applied to ET biofilms to identify microorganisms attached to their surface with a great variety of species identified. However, we did not find significant differences in comparison with the traditional tracheal aspirate culture approach.

The role of biofilm on orthopaedic implants: the "Holy Grail" of post-traumatic infection management?

The development of post-traumatic infection is potentially a limb threatening condition. The orthopaedic trauma literature lags behind the research performed by our arthroplasty colleagues on the topic of implant-related infections. Surgical site infections in the setting of a recent ORIF are notoriously hard to eradicate due to biofilm formation around the implant. This bacteria-friendly, dynamic, living pluri-organism structure has the ability to morph and adapt to virtually any environment with the aim to maintain the causative organism alive. The challenges are twofold: establishing an accurate diagnosis with speciation/sensitivity and eradicating the infection. Multiple strategies have been researched to improve diagnostic accuracy, to prevent biofilm formation on orthopaedic implants, to mobilize/detach or weaken the biofilm or to target specifically bacteria embedded in the biofilm. The purpose of our paper is to review the patho-physiology of this mysterious pluri-cellular structure and to summarize some of the most pertinent research performed to improve diagnostic and treatment strategies in biofilm-related infections.

Role of Sonication for Detection of Infection in Explanted Orthopaedic Trauma Implants

OBJECTIVES

Sonication is a new technology that uses high-frequency sound waves to mechanically dislodge bacteria adherent in biofilms. Unlike arthroplasty, its role in orthopaedic trauma has not been described. The goal of this study was to explore the utility of sonication in orthopaedic trauma.

DESIGN

Retrospective review.

SETTING

Level I trauma center.

PATIENTS

One hundred forty-six sonicated metallic orthopaedic devices from September 2010 to May 2013 were included. Patients were divided into 3 groups: clinically infected, elective implant removals, and nonunion.

INTERVENTION

Sonication culture results were retrospectively reviewed for all patients undergoing implant removal.

OUTCOMES

Sonication results were the primary study outcome and were considered positive for culture growth if equal to or greater than 20 colony-forming units per plate.

RESULTS

In 32 patients with clinical infection, tissue cultures were positive in 30 (94%) and negative in 2 (6%). In contrast, sonication cultures were positive in 19 patients (59%) and did not identify additional organisms. Of the 72 patients who underwent elective implant removal, 52 had pain. Sonication cultures were positive in 5 of these 52 patients (10%) and in 0 of 20 patients with no pain. Sonication culture results were negative in all 42 patients who underwent nonunion surgery.

CONCLUSIONS

Sonication of orthopaedic trauma implants in patients with clinically apparent infection or "aseptic" nonunion offered negligible additional information. Sonication demonstrated a positive microbiologic yield in a subset of patients with painful implants; further research is required to better establish the frequency of subclinical infection and to determine the diagnostic role of traditional cultures and sonication.

LEVEL OF EVIDENCE

Diagnostic Level III. See Instructions for Authors for a complete description of levels of evidence.

Concentration of Sonication Fluid through Centrifugation Is Superior to Membrane Filtration for Microbial Diagnosis of Orthopedic Implant-Associated Infection

Microbial identification of orthopedic implant-associated infections using sonication fluid (SF) submitted to a concentration step by membrane filtration (SMF) was compared with the standard centrifugation (SC) method. Among 33 retrieved infected implants, sonication identified microorganisms in 26 (78.8%). The sensitivity of SC was higher than that of SMF (78.8% versus 30.3%; P < 0.001).

Are atrophic long-bone nonunions associated with low-grade infections?

Impaired fracture healing, especially when associated with bacterial infection, is a severe complication following long-bone fractures and requires special treatment. Because standard diagnostic techniques might provide falsely negative results, we evaluated the sonication method for detection of bacteria on implants of patients with fracture nonunions. A total of 49 patients with a nonunion (group NU) and, for comparison, 45 patients who had undergone routine removal of osteosynthetic material (group OM), were included in the study. Five different diagnostic methods (culture of tissue samples, culture of intraoperative swabs, histopathology of tissue samples, culture of sonication fluid, and 16S ribosomal DNA polymerase chain reaction of sonication fluid) were compared and related to clinical data. Among the diagnostic tests, culture of sonication fluid demonstrated by far the highest detection rate of bacteria (57%) in group NU, and rather unexpectedly 40% in group OM. Culture of sonication samples also revealed a broad spectrum of bacteria, in particular Propionibacterium spp. In conclusion, our results indicate that more bacteria can be detected on implants of patients with atrophic nonunions of long-bone fractures by means of the sonication procedure, which provides a valuable additional diagnostic tool to decide on a surgical procedure (eg, two-step procedure) and to further specify antimicrobial therapy.

Surgical management of infected non-unions: An update

Infected non-union is a devastating complication post fracture fixation. While its incidence is small, its management is lengthy, challenging and costly. Complex reconstruction surgery is often required with unpredictable outcomes despite the significant advances that have been made in diagnostics, surgical techniques and antibiotic protocols. In this article we present recent approaches to the surgical treatment of this condition.

Microbial diagnosis of infection and colonization of cardiac implantable electronic devices by use of sonication

OBJECTIVES

The clinical utility of sonication as an adjunctive diagnostic tool for the microbial diagnosis of cardiac implantable device-associated infections (CIDAIs) was investigated.

METHODS

The implants of 83 subjects were investigated, 15 with a CIDAI and 68 without a clinical infection. Clinical data were analyzed prospectively and sonication fluid cultures (83 patients, 100%) and traditional cultures (31 patients, 37.4%) were performed

RESULTS

Generator pocket infection and device-related endocarditis were found in 13 (86.7%) and four (26.7%) subjects, respectively. The mean numbers of previous technical complications and infections were higher in the infected patients compared to the non-infected patients (8 vs. 1, p<0.001; 2 vs. 0, p<0.031, respectively). The sensitivity and specificity for detecting CIDAI was 73.3% (11/15) and 48.5% (33/68) for sonication fluid culture, and 26.7% (4/15) and 100% (16/16) for traditional culture (p<0.001), respectively. A higher number of organisms were identified by sonication fluid than by tissue culture (58 vs. 4 specimens; p<0.001). The most frequent organisms cultured were Gram-positive cocci (66.1%), mainly coagulase-negative staphylococci (35.5%). Thirty-five (51.5%) non-infected subjects were considered colonized due to the positive identification of organisms exclusively through sonication fluid culture.

CONCLUSIONS

Sonication fluid culture from the removed cardiac implants has the potential to improve the microbiological diagnosis of CIDAIs.