|Year : 2019 | Volume
| Issue : 1 | Page : 99-101
Sonication of antibiotic loaded cement spacers: A valuable technique for detection of infection persistence in two-stage revision for infected joint arthroplasty
Sujeesh Sebastian1, Rajesh Malhotra2, Benu Dhawan1, Vishnubhatla Sreenivas3, Arti Kapil1, Rama Chaudhry1
1 Department of Microbiology, All Institute of Medical Sciences, New Delhi, India
2 Department of Orthopaedics, All Institute of Medical Sciences, New Delhi, India
3 Department of Biostatistics, All Institute of Medical Sciences, New Delhi, India
|Date of Web Publication||16-Aug-2019|
Prof. Rajesh Malhotra
Department of Orthopaedics, All India Institute of Medical Sciences, New Delhi - 110 029
Source of Support: None, Conflict of Interest: None
We evaluated the diagnostic utility of sonication of antibiotic loaded cement spacers comparing with periprosthetic tissue cultures for the detection of persisting infection in 14 patients undergoing staged procedures. Sonication improved microbial detection of intraoperative cultures from 14.2% to 28.5% (P = 0.481). Routine sonication of spacers is recommended.
Keywords: Explanted cement spacers, periprosthetic tissue, prosthetic joint infection, sonication, sonicate fluid culture
|How to cite this article:|
Sebastian S, Malhotra R, Dhawan B, Sreenivas V, Kapil A, Chaudhry R. Sonication of antibiotic loaded cement spacers: A valuable technique for detection of infection persistence in two-stage revision for infected joint arthroplasty. Indian J Med Microbiol 2019;37:99-101
|How to cite this URL:|
Sebastian S, Malhotra R, Dhawan B, Sreenivas V, Kapil A, Chaudhry R. Sonication of antibiotic loaded cement spacers: A valuable technique for detection of infection persistence in two-stage revision for infected joint arthroplasty. Indian J Med Microbiol [serial online] 2019 [cited 2019 Oct 21];37:99-101. Available from: http://www.ijmm.org/text.asp?2019/37/1/99/264478
| ~ Introduction|| |
A two-stage exchange arthroplasty is a valuable option for the treatment of chronic or delayed prosthetic joint infection (PJI). Although two-stage arthroplasty is known for its successful outcome, notable rates of reinfection have also been documented in the literature. Failure of routine pre- and intra-operative diagnostic tests to detect the incomplete eradication of PJI before second-stage surgery is a matter of concern for orthopaedic surgeons.
Several studies have evaluated the utility of sonication of the explanted antibiotic cement spacers for the detection of persisting infection in patients undergoing staged exchange procedures for PJI.,,,, However, none of these studies has used the Musculoskeletal Infection Society (MSIS) consensus criteria as the gold standard for PJI.
We evaluated the diagnostic efficacy of sonication of explanted antibiotic loaded cement spacers with the conventional periprosthetic tissue culture (PTC) method to detect the persisting infection in patients diagnosed with PJI as per MSIS consensus criteria, undergoing staged exchange procedures for PJI.
| ~ Materials And Methods|| |
Patients who underwent staged exchange procedures for PJI between July 2016 and June 2017 were enrolled. Institutional ethical approval was obtained (Ref. No. IESC/T-419/01.11.2013). PJI was confirmed for patients according to MSIS guidelines.
Intraoperatively, three to five periprosthetic tissue specimens were obtained for aerobic and anaerobic culture and processed in accordance with standard protocols. Briefly, specimens were aseptically homogenised in sterile mortar and pestle with saline solution for 1 min. Aliquots of the homogenate were inoculated onto a set of aerobic (sheep blood agar [SBA] and MacConkey agar [MA]) and anaerobic culture media (brain heart infusion agar [BHIA] and Robertson's cooked meat broth [RCM]). Both SBA and MA plates were incubated aerobically at 37°C for 2–4 days. BHIA plates were incubated anaerobically at 37°C for 7–14 days. RCM broth was subcultured if cloudy or systematically on the 7th and 14th day. Organisms were identified using matrix-assisted laser desorption ionization-time-of-flight mass spectrometry system (Vitek MS™; BioMe'rieux, France). A true positive PTC result was defined as the isolation of the identical microorganism in more than two tissue specimens.
Extracted cement spacers were aseptically placed in plasma-sterilised polypropylene container and following the previously described sonication protocol. Sonication was performed in Bactosonic 14.2 (Bandelin GmbH, Berlin, Germany) ultrasonic bath. Briefly, the extracted spacer was sonicated in normal saline for 7 min at 40 kHz. Sonication fluid was then centrifuged at 3200 × g for 20 min in sterile 50-ml conical centrifuge tubes. The supernatant was aspirated, and 0.1 ml of sediment was processed in the same manner as periprosthetic tissue. A positive sonicate fluid culture (SFC) was defined as that with at least 20 colony-forming units (CFUs) per plate.
Statistical analyses were performed with Stata software version 14.2 (Stata Corp LLC; Texas, USA).
| ~ Results|| |
A total of 14 patients suitable for second-stage reimplantation for PJI with cement spacer in situ after the first stage as evidenced by normal laboratory parameters and negative culture of preoperatively aspirated joint fluid were included in the study (eight knee and six hip replacements). The demographic data of the patients are shown in [Table 1]. The interval between the two stages (indicating the period for which cement spacer remained in situ) ranged from 12 to 76 weeks (average 30 weeks).
Multiple periprosthetic tissue samples were collected from each patient at the time of second-stage surgery. Fourteen antibiotic loaded cement spacers were received for sonication. All the spacers contained vancomycin; but, in three cases, gentamicin had been added, and in another two, tobramycin had been added. SFC of the explanted spacer was positive in four cases (28.5%), with detection of one isolate each of Staphylococcus hominis, Staphylococcus epidermidis, Escherichia coli and Enterobacter cloacae, respectively. The traditional PTC was positive in only two of these. Sonication of explanted cement spacer improved microbial detection compared to PTC from 14.2% to 28.55% (P = 0.481). In all cases with positive SFC of the explanted spacer, the same pathogen that had caused the initial infection grew in the sonication fluid of the cement spacer.
| ~ Discussion|| |
The results of our study demonstrate that sonication culture of antibiotic loaded cement spacers is superior to PTC for the detection of persisting infection at the time of staged exchange procedures. Limited studies are available on the diagnostic utility of removed spacer sonication as compared to PTC for detecting the infection persistence in the second-stage surgery.,,,, The SFC of the removed spacer in our study was positive in four cases. In two of these positive cases, PTC failed to identify the pathogen. Of note, there was no discordance between SFC of the spacer with the culture of the prosthesis ( first-stage surgery) or the PTC (second-stage surgery).
Sonication culture also showed its ability to detect coagulase-negative staphylococci on the antibiotic loaded cement spacers. As reported by Sebastian et al., the increased susceptibility of Gram-negative bacteria than Gram-positives to the effect of ultrasound could be the reason for their decreased recovery. Similar results have been reported by Monsen et al. and Shen et al.,
Spacer sonication was performed as described by Monsen et al. Results' interpretation and reporting were based on the criteria developed by Piper et al.; a positive sonication value was considered ≥20 CFU and negative sonication value <20 CFU. However, Nelson et al. have suggested that 5 CFU should be considered as the cutoff value for cement spacers since a cutoff value of 20 CFU may lead to false negatives if applied to cement spacers. However, for optimal sensitivity and specificity, Piper et al. recommended a cutoff value of ≥5 and ≥20 CFU as the ideal for unconcentrated and concentrated sonicate fluid, respectively. Since our sonication protocol included a concentration step, we used a cutoff value of ≥20 CFU. Categorical CFU data for sonication of spacers have not been published. Further studies are required to determine the ideal cutoff values for cement spacer sonication.
It has been suggested that antimicrobial loaded spacers could negatively impact sonicate culture results. However, Park et al. reported that antimicrobial loaded spacers did not influence the microbiologic culture yield of SFC. This suggests that combining sonication of antibiotic loaded cement spacers with the bacterial culture at second-stage surgery can improve the diagnosis of persisting infection as was observed by us where the diagnosis of four (28.7%) cases of persisting infection was possible.
Detection of persisting infection is important as it is associated with poor outcome and may explain the failures reported with the two-stage protocol for PJI. All the four patients with lingering infection were given pathogen-specific antibiotic therapy. One patient died because of underlying diseases not related to the infection. All other patients did not develop reinfection at a minimum of 7-month follow-up.
Limitations of our study include the relatively small number of patients, which implies limited statistical power. Nonetheless, our results emphasise the importance of routine sonication of spacers to detect subclinical infections to help ensure a good clinical outcome following two-stage arthroplasty.
Financial support and sponsorship
Conflicts of interest
There are no conflicts of interest.
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