Propionibacterium acnes causing delayed postoperative spine infection: Review

Delayed Infection After Cervical Disc Arthroplasty: A Case Report and Review of the Literature

STUDY DESIGN

Case report and literature review.

OBJECTIVE

To report the relatively rare complication of delayed infection after cervical disc arthroplasty (CDA).

BACKGROUND

Delayed infection of the M6 device has been a rarely reported complication, with all cases described outside of the United States. The reliability of positive intraoperative cultures remains an ongoing debate.

METHODS

Cases were reviewed, and findings were summarized. A literature review was performed and discussed, with special consideration to current reports of delayed M6 infection, etiology, and utility of intraoperative cultures.

RESULTS

We present a case of delayed infection 6 years after primary 1-level CDA with the M6 device. At revision surgery, gross purulence was encountered. Intraoperative cultures finalized with Staphylococcus epidermidis and Cutibacterium acnes. The patient was revised with removal of the M6 and conversion to anterior cervical discectomy and fusion. A prolonged course of intravenous antibiotics was followed by an oral course for suppression. At the final follow-up, the patient's preoperative symptoms had resolved.

CONCLUSION

Delayed infection after CDA is a rare complication, with ongoing debate regarding the reliability of positive cultures. We describe an infected M6 and demonstrate the utility of implant removal, conversion to anterior cervical discectomy and fusion, and long-term antibiotics as definitive treatment.

LEVEL OF EVIDENCE

Level V-case report and literature review.

Positive Cutibacterium acnes Intervertebral Discs Are Not Associated with Subsidence Following Anterior Cervical Discectomy and Fusion at 3 or 6 Months

Background/Objectives:Cutibacterium acnes (C. acnes), formerly known as Propionibacterium acnes (P. acnes), is an anaerobic, low-virulent bacterium that has been associated with postoperative infections of the shoulder, knee, and cervical spine. Recent studies have highlighted an association between C. acnes and the development of degenerative disc disease (DDD). The aim of this study is to ascertain whether C. acnes increases the risk of subsidence following anterior cervical discectomy and fusion (ACDF). Methods: After IRB approval, consecutive patients undergoing elective ACDF for DDD from 2017 to 2018 were enrolled in this prospective cohort study. Intervertebral disc samples were taken at each affected level and cultured. A total of 66 patients with radiographic follow-ups were included in the final analysis. The extent of subsidence and cervical lordosis was determined immediately postoperatively and at the 3- and 6-month follow-ups. Results: No significant difference in subsidence was observed at 3 months (p = 0.07) or 6 months (p = 0.11) between culture-positive and -negative cohorts. Additionally, there was no significant difference detected in the change in cervical lordosis observed at 3 months (p = 0.16) or 6 months (p = 0.27) between culture-positive and -negative cohorts. For the most inferiorly fused segment, there was a significant difference in subsidence observed at 3 months (1.5 mm, 95% CI: 0.2-2.7 mm, p = 0.02) but not at 6 months (p = 0.17). Conclusions: Intervertebral discs with a positive C. acnes culture were not associated with greater levels of subsidence at 3 or 6 months following ACDF for DDD. Further research is necessary to endorse these results and to gauge the clinical significance of C. acnes infection.

Tissue response following implantation with the posterior dynamic distraction device (PDDD) in adolescent idiopathic scoliosis (AIS)

PURPOSE

The PDDD is a ratchet-based, unidirectional expandable rod to treat adolescent idiopathic scoliosis (AIS), primarily by correcting scoliotic deformity without full spinal fusion. We hypothesized that the device will be fully tolerated by the host and, if aseptic screw loosening occurs, it will be unrelated to wear particle formation.

METHODS

This study comprised tissue samples from seven patients from a prospective study (NCT04296903) to assess the PDDD's safety and benefits, reoperated due to complications. Host response was assessed from histological slides (four levels/implant) in accordance with GLP and ISO10993-6:2016. The elementary chemical composition of wear particles present in tissue sections was quantified by energy dispersive X-ray spectroscopy (EDX).

RESULTS

Host reaction was minor, characterized by low levels of diverse inflammatory cells, mild fibrosis, occasional small necrotic foci, neovascularization, hemorrhage, and, rarely, small bone fragments. Twenty-four of 28 tissue sections displayed varying degrees of wear particles (black discoloration), and most sections (17) were scored as 1 (< 25% of the sample). The discoloration observed corresponded to black-appearing, fine granular pigment. EDX analysis confirmed particles were composed of titanium, aluminum, and vanadium. Twenty-six of 28 samples were scored zero for necrosis and 2/28 were scored 1. Eleven samples were scored zero for fibrosis, 12 as 1, and five as 2. No aseptic screw loosening occurred.

CONCLUSION

The PDDD induced minimal host reaction with little or no degeneration, inflammation or fibrosis. No changes present could be expected to promote device failure. The PDDD implant for treating AIS is well-tolerated and locally safe.

One-step Bio-guided Isolation of Secondary Metabolites from the Endophytic Fungus Penicillium crustosum Using High-resolution Semi-preparative HPLC

BACKGROUND

An endophytic fungal strain Penicillium crustosum was isolated from the seagrass Posidonia oceanica and investigated to identify its antimicrobial constituents and characterize its metabolome composition. The ethyl acetate extract of this fungus exhibited antimicrobial activity against methicillin-resistant Staphylococcus aureus (MRSA) as well as an anti-quorum sensing effect against Pseudomonas aeruginosa.

METHODS

The crude extract was profiled by UHPLC-HRMS/MS, and the dereplication was assisted by feature-based molecular networking. As a result, more than twenty compounds were annotated in this fungus. To rapidly identify the active compounds, the enriched extract was fractionated by semipreparative HPLC-UV applying a chromatographic gradient transfer and dry load sample introduction to maximise resolution. The collected fractions were profiled by 1H-NMR and UHPLC-HRMS.

RESULTS

The use of molecular networking-assisted UHPLC-HRMS/MS dereplication allowed preliminary identification of over 20 compounds present in the ethyl acetate extract of P. crustosum. The chromatographic approach significantly accelerated the isolation of the majority of compounds present in the active extract. The one-step fractionation allowed the isolation and identification of eight compounds (1-8).

CONCLUSION

This study led to the unambiguous identification of eight known secondary metabolites as well as the determination of their antibacterial properties.

A practical method for the retrieval of tulip-head polyaxial pedicle screw by reusing the rod in revision and implants removal surgery: introduction of technique and evaluation of clinical outcomes

BACKGROUND

The removal of spinal implants is needed in revision surgery or in some cases whose fracture had healed or fusion had occurred. The slip of polyaxial screw or mismatch of instruments would make this simple procedure intractable. Here we introduce a simple and practical method to address this clinical dilemma.

METHODS

This is a retrospective study. The patients underwent new technique for retrieving the implants from July 2019 to July 2022 were labeled as group A, while the patients underwent traditional implants retrieval technique from January 2017 to January 2020 were labeled as group B. Patients in each group were subdivided into revision surgery group (r group) and simple implants removal group (s group) according to the surgery fashion. For the new technique, the retrieved rod was cut off to a proper length which was matched with the size of tulip head, and was replaced into the tulip head. After tightened with nut, a monoaxial screw-rod "construct" was formed. Then the "construct" can be retrieved by a counter torque. The operation duration, intraoperative blood loss, post-operative bacteria culture, hospital stay and costs were analyzed.

RESULTS

A total of 116 polyaxial screws with difficult retrieval (43 screws in group A, 73 screws in group B) in 78 patients were recorded, in which 115 screws were successfully retrieved. Significant differences were found in the mean operation duration, intraoperative blood loss when comparing the r group in group A and B, as well as the s group in group A and B (P < 0.05). There were no significant differences in hospital stay and costs between group A and B. Three patients were found positive bacteria culture of drainage tube/tape in group A (3/30), while 7 patients in group B (7/48). The most prevalent bacteria was Propionibacterium acnes.

CONCLUSION

This technique is practical and safe in retrieving tulip head poly-axial screw. Reduced operation duration and intraoperative bloods loss may potentially alleviate the hospitalization burden of patients. Positive bacterial cultivation results are common after implants removal surgery, but they rarely represent an organized infection. A positive culture with P. acnes or S. epidermidis should be interpreted with caution.

Cutibacterium spp. Infections after Instrumented Spine Surgery Have a Good Prognosis Regardless of Rifampin Use: A Cross-Sectional Study

Infection after spinal instrumentation (IASI) by Cutibacterium spp. is being more frequently reported. The aim of this study was to analyse the incidence, risk factors, clinical characteristics, and outcome of a Cutibacterium spp. IASI (CG) compared with non-Cutibacterium IASI (NCG) infections, with an additional focus on the role of rifampin in the treatment. All patients from a multicentre, retrospective, observational study with a confirmed IASI between January 2010 and December 2016 were divided into two groups: (CG and NCG) IASI. Baseline, medical, surgical, infection treatment, and follow-up data were compared for both groups. In total, 411 patients were included: 27 CG and 384 NCG. The CG patients were significantly younger. They had a longer median time to diagnosis (23 vs. 13 days) (p = 0.025), although 55.6% debuted within the first month after surgery. Cutibacterium patients were more likely to have the implant removed (29.6% vs. 12.8%; p = 0.014) and received shorter antibiotic regimens (p = 0.014). In 33% of Cutibacterium cases, rifampin was added to the baseline therapy. None of the 27 infections resulted in treatment failure during follow-up regardless of rifampin use. Cutibacterium spp. is associated with a younger age and may cause both early and late IASIs. In our experience, the use of rifampin to improve the outcome in the treatment of a Cutibacterium spp. IASI is not relevant since, in our series, none of the cases had therapeutic failure regardless of the use of rifampin.

Risk Factors and Outcomes of Central Nervous System Infection After Spinal Surgery: A Retrospective Cohort Study

OBJECTIVE

To investigate the risk factor associated with central nervous system infection, a rare and dire complication after spinal surgery.

METHODS

Univariate and multivariate logistic regression analyses were performed to screen for the independent risk factors. According to the different administration methods of antibiotics, patients were divided into intravenous and intrathecal groups. The differences in time needed for body temperature, white blood cells (WBC), and C-reactive protein (CRP) to return to normal and the time of antibiotic application were compared between the 2 groups. In addition, the differences in WBC, neutrophil ratio, CRP, procalcitonin in blood, and WBC in cerebrospinal fluid were compared before intrathecal injection, after the first one, and the last one. The incidence of complications in the 2 groups was observed.

RESULTS

Dural tears, laminectomy, and operation time >3 hours were identified as independent risk factors. The time needed for body temperature, WBC, and CRP to return to normal and the antibiotic application time were significantly different between the 2 groups (all P < 0.05). Before and after the first intrathecal injection and after the last intrathecal injection, the differences in WBCs, neutrophil ratios, CRP, procalcitonin in blood, and cerebrospinal fluid-WBC were statistically significant in overall and pairwise comparisons (P < 0.05). Complications occurred in 2 and 14 cases, respectively.

CONCLUSIONS

The independent risk factors for central nervous system infection after spinal surgery were a dural tear, laminectomy, and operation time > 3 hours. Combined intravenous and intrathecal injections of antibiotics led to a better effect than intravenous injection alone; however, this approach was associated with more complications.

Anaerobic spondylodiscitis: a retrospective analysis

Background

This retrospective study analyzed the clinical characteristics and outcomes of patients with anaerobic spondylodiscitis.

Methods

From a total of 382 patients with infectious spondylodiscitis, nine patients (2.4%; two male and seven female with an average age of 67 years) with anaerobic spondylodiscitis between March 2003 and March 2017 were analyzed.

Results

Most of the patients (77.8%) initially presented with afebrile back pain. Hematogenous spread occurred in seven patients and postoperative infection in two patients. Bacteroid fragilis was the most common pathogen isolated from three patients. Atypical radiographic characteristics, including a vertebral fracture with the preservation of disk height or coexisting spondylolytic spondylolisthesis, occurred in four patients with hematogenous anaerobic spondylodiscitis. The eradication rate of anaerobic infection was significantly higher in the patients with hematogenous infection than in those with postoperative infection (100% vs. 0%, p = 0.0476). Anaerobic spondylodiscitis accounted for 2.4% of cases of infectious spondylodiscitis and predominantly affected the female patients.

Conclusions

Diagnostic delay may occur because of atypical spinal radiographs if the patient reports only back pain but no fever. Anaerobic infection following elective spinal instrumentation has a higher recurrence rate.

Incidence, Management and Outcome of Delayed Deep Surgical Site Infection Following Spinal Deformity Surgery: 20-Year Experience at a Single Institution

STUDY DESIGN

A retrospective study.

OBJECTIVES

To investigate the incidence, management and outcome of delayed deep surgical site infection (SSI) after the spinal deformity surgery.

METHODS

This study reviewed 5044 consecutive patients who underwent spinal deformity corrective surgery and had been followed over 2 years. Delayed deep SSI were defined as infection involving fascia and muscle and occurring >3 months after the initial procedure. An attempt to retain the implant were initially made for all patients. If the infection failed to be eradicated, the implant removal should be put off until solid fusion was confirmed, usually more than 2 years after the initial surgery. Radiographic data at latest follow-up were compared versus that before implant removal.

RESULTS

With an average follow-up of 5.3 years, 56 (1.1%) patients were diagnosed as delayed deep SSI. Seven (12.5%) patients successfully retained instrumentation and there were no signs of recurrence during follow-up (average 3.4 years). The remaining patients, because of persistent or recurrent infection, underwent implant removal 2 years or beyond after the primary surgery, and solid fusion was detected in any case. However, at a minimum 1-year follow-up (average 3.9 years), an average loss of 9° in the thoracic curve and 8° in the thoracolumbar/lumbar curves was still observed.

CONCLUSIONS

Delayed deep SSI was rare after spinal deformity surgery. To eradicate infection, complete removal of implant may be required in the majority of delayed SSI. Surgeons must be aware of high likelihood of deformity progression after implant removal, despite radiographic solid fusion.

Late spinal infections are more common after pediatric than after adult spinal deformity surgery

PURPOSE

To compare the incidence, timing, and microbiologic factors associated with late spinal infection (onset ≥ 6 months after index operation) in pediatric versus adult spinal deformity patients who underwent instrumented posterior spinal fusion (PSF).

METHODS

We retrospectively queried our institutional database for pediatric (aged ≤ 21 years) and adult patients who underwent instrumented PSF from 2000 to 2015. Inclusion criteria were > 12-month follow-up, spinal arthrodesis spanning 4 or more levels, and idiopathic or degenerative spinal deformity. We included 1260 patients (755 pediatric, 505 adult). Incidence, timing, and microbiologic and operative parameters of late spinal infections were compared using chi-squared and Fisher exact tests. Alpha = 0.05.

RESULTS

Late spinal infection occurred in 28 (3.7%) pediatric and 2 (0.39%) adult patients (p = 0.009). Mean onset of infection was 4.2 years (range 0.7-12) in pediatric patients and 4.0 years (range 0.7-7.3) in adults (p = 0.93). Pediatric patients underwent arthrodesis spanning more levels (mean ± standard deviation, 10 ± 2.0) compared with adults (8.4 ± 3.3) (p < 0.001). Adults experienced greater intraoperative blood loss (2085 ± 1491 mL) compared with pediatric patients (796 ± 452 mL) (p < 0.001). Culture samples yielded positive growth in 11 pediatric and 2 adult cases. Propionibacterium and coagulase-negative staphylococci were the most commonly detected microorganisms in both cohorts.

CONCLUSION

Late spinal infections were significantly more common in pediatric patients than in adults after instrumented PSF for spinal deformity. Skin and indolent microorganisms were the primary identifiable causative bacteria in both cohorts.

LEVEL OF EVIDENCE

III.

Indolent Infection After Lumbar Interbody Fusion: An Under-recognized Cause of Pseudarthrosis, Which Can Be Successfully Treated With Anterior Revision Fusion

Introduction:

Methods:

Results:

Discussion:

Cobalt-Chromium Alloy Has Superior Antibacterial Effect Than Titanium Alloy: In Vitro and In Vivo Studies

STUDY DESIGN

In vitro and in vivo laboratory studies.

OBJECTIVE

This study aimed to compare bacterial survival on titanium alloy (Ti) and cobalt-chromium alloy (CC) using in vitro and in vivo experiments.

SUMMARY OF BACKGROUND DATA

Spinal implants are frequently manufactured from Ti and CC. These foreign materials are thought to be susceptible to biofilm formation that contributes to the development of surgical site infections. Certain metals (i.e., silver, cobalt) are known to have antibacterial properties.

METHODS

In the in vitro study, discs made of Ti or CC were incubated with one of two common bacteria: Staphylococcus aureus (S. aureus) and Propionibacterium acnes (P. acnes). After incubation, discs were assessed to determine the number of viable bacterial cells. In the in vivo study, the discs that were made of CC or Ti were implanted into the subcutaneous layer of BALB/c mice. After skin closure, a suspension including either S. aureus or P. acnes was directly inoculated on the implanted discs. The discs were retrieved and analyzed to determine the number of viable bacteria at 0.5, 1, and 3 days after inoculation.

RESULTS

The number of viable S. aureus cultured from the CC discs was 0.9 ± 0.2 × 103 CFU/disc, which was significantly lower than the cultured Ti discs (114.8 ± 18.3 × 103 CFU/disc). Moreover, a significantly lower mean number of P. acnes were cultured with CC (1.9 ± 1.2 × 103 CFU/disc) compared with the Ti (180.0 ± 72.1 × 103 CFU/disc). The in vivo infection model testing against S. aureus or P. acnes showed a significantly lower number of viable S. aureus or P. acnes on CC discs than Ti discs. The result was seen at all measured time points.

CONCLUSION

CC suppressed S. aureus and P. acnes proliferation compared with Ti in vitro and in an in vivo infection model.Level of Evidence: N/A.

Mycoplasma hominis Lumbar Wound Infection After Posterior Decompression and Instrumented Fusion: A Case Report

CASE

A 63-year-old man underwent L2-S1 decompression and fusion for spinal stenosis. He developed urinary retention postoperatively requiring catheterization. He developed fever, purulence, and foot-drop 8 days postoperatively and underwent debridement with implant retention. Cultures yielded Mycoplasma hominis after 10 days. He received 4 weeks of doxycycline. Four years postoperatively, he had no recurrence of infection and was able to ambulate despite a persistent foot-drop.

CONCLUSION

Mycoplasma hominis is a urogenital commensal rarely implicated in musculoskeletal infections. A high index of suspicion is required in spinal surgery patients who develop fever and purulence and have initial negative cultures and poor response to empirical antibiotics.

Late spinal infections following posterior spinal fusion in pediatric deformities: treatment using single-stage titanium implant exchange

PURPOSE

Late infection following posterior spinal fusion (PSF) for deformity is a leading cause of revision. The purpose of this study is to evaluate clinical and radiographic outcomes following a single-stage debridement and exchange of spinal implants with titanium in adolescent patients with late-onset infections following PSF METHODS: A retrospective review of prospectively collected data of adolescent patients with spinal deformity, who were surgically treated with PSF was collected. Patients were included for the study if they developed late arising infection (> 1 year after index posterior fusion for the deformity) from 2006-2019. Treatment consisted of irrigation, debridement, implant exchange with titanium screws and rods, and antibiotics. Parameters evaluated include radiographic Cobb angles, operative data, and clinical data, all at minimum 2-year follow-up.

RESULTS

31 patients (29 with AIS and 2 with Scheuermann's kyphosis) developed late spinal infections. Mean age was 11.4 ± 2.3 years, 84% female, mean time from index surgery was 52.5 months. 25 had all stainless steel implants and 6 had cobalt chrome during the index procedure. Positive cultures were obtained in 5 patients (2 Staphylococcus Aureus, 1 Staphylococcus epidermidis, 1 Peptostreptococcus, 1 Pseudomonas aeruginosa) with cultures followed till 7 days post-operatively. At 2-years following the exchange, there was no change in coronal and sagittal alignment. Three (9%) patients developed subsequent infection necessitating implant removal.

CONCLUSION

A single-stage procedure consisting of implant removal, irrigation, and debridement, and replacement with all titanium implants is an effective treatment strategy in patients developing late wound infection following PSF with regards to maintenance of curve correction and minimizing recurrent infections.

Antibiotic treatment of postoperative spinal implant infections

Postoperative spinal implant infection (PSII) is a serious complication after spinal surgery. It is associated with increased morbidity and mortality for affected patients as well as significant costs for the healthcare system. Due to the formation of biofilm on foreign material, both diagnosis and treatment of PSII can pose a considerable challenge. Modern treatment protocols allow efficient eradication and good clinical outcomes in the majority of patients. In this article, we review the current antibiotic treatment concepts for PSII including the correct choice of antibiotics and their combination. In cases of late-onset PSII where the implants can be removed, two weeks of intravenous (IV) antibiotics followed by 4 weeks of oral antibiotics seem appropriate. If the implant needs to be retained, a 2-week IV antibiotic treatment should be followed by 10 weeks of oral antibiotic therapy with biofilm activity or, in case of problematic pathogens, a long-term suppression therapy. Initial empiric antibiotic therapy should cover staphylococci, streptococci, enterococci and Gram-negative bacilli as the most common pathogens. Antibiotic adjustments according to the type of pathogen and its antimicrobial susceptibility are essential for successful eradication of infection.

Sustained Postoperative Fever Without Evident Cause After Spine Instrumentation as an Indicator of Surgical Site Infection

BACKGROUND

Surgical site infection after spinal instrumentation increases morbidity and mortality as well as medical costs and is a burden to both patients and surgeons. Late-onset or sustained fever increases the suspicion for comorbid conditions. This retrospective, exploratory cohort study was conducted to identify the rate of and risk factors for sustained or late-onset postoperative fever after spinal instrumentation operations and to determine its relationship with surgical site infection.

METHODS

Five hundred and ninety-eight patients who underwent lumbar or thoracic spinal instrumentation were retrospectively reviewed. The patients were divided according to (1) whether or not they had had a sustained fever (SF[+] or SF[-]) and (2) whether or not they had had a surgical site infection (SSI[+] or SSI[-]). Clinical characteristics, surgical factors, prophylactic antibiotic usage, fever pattern, and laboratory/imaging findings were recorded for all patients by electronic medical chart review.

RESULTS

In total, 68 patients (11.4%) had a sustained fever. The rate of surgical site infection was significantly higher when the patient had sustained fever (13.2% [9 of 68] compared with 0.9% [5 of 530]; p < 0.001). Comparison of the patients who had a sustained fever but no surgical site infection (SF[+], SSI[-]) and those with both a sustained fever and surgical site infection (SF[+], SSI[+]) showed that continuous fever, an increasing or stationary pattern of inflammatory markers, and a C-reactive protein (CRP) level of >4 mg/dL on postoperative days 7 to 10 were diagnostic clues for surgical site infection. The sensitivity and specificity of postoperative magnetic resonance imaging (MRI) for the detection of surgical site infection were 40.0% and 90.9%, respectively, when MRI was performed within 1 month after surgery.

CONCLUSIONS

Although most patients with sustained fever did not have surgical site infection, fever was significantly related to surgical site infection. Continuous fever, increasing patterns of inflammatory markers, and high CRP on postoperative days 7 to 10 were diagnostic clues for surgical site infection. This study demonstrated provisional results for factors that can discriminate febrile patients with surgical site infection from febrile patients without infection. Further investigation with a larger sample size is warranted for clarification.

LEVEL OF EVIDENCE

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

Early adherence and biofilm formation of Cutibacterium acnes (formerly Propionibacterium acnes) on spinal implant materials

BACKGROUND

Cutibacterium acnes (C. acnes) is associated with infection following shoulder and spine surgery due to follicular pore concentrations in these anatomic regions. It has been established that it can form biofilms on surgical implant materials, which may contribute to its role in perioperative infection, but its behavior of early colonization on those materials is not yet well understood.

PURPOSE

The purpose of this study was to evaluate the time to adherence and subsequent biofilm formation of C. acnes in the first 24 hours on implant materials commonly used in spinal surgery.

STUDY DESIGN

We compared the colonization and behavior of C. acnes over time when applied to five commonly used spine implant materials - polyether ether ketone (PEEK), cobalt chromium (CC), stainless steel (SS), titanium, and titanium alloy.

METHODS

C. acnes was applied onto the samples of PEEK, CC, SS, titanium, and titanium alloy, and allowed to adhere for periods of 4, 8, 12, 16, and 20 hours. Nonadherent bacteria were then washed from the samples. These samples were then allowed to continue incubating for a total 24 hours. Scanning electron microscopy and confocal laser scanning microscopy were used to visualize all samples for the presence and quantification of C. acnes adherence at each time period. Subsequent transition to biofilm formation on these samples was assessed via scanning electron microscopy at each time period.

RESULTS

The PEEK specimens exhibited the highest amount of surface biological burden in the first 24 hours compared with the other materials, which displayed little or no adherence. Rapid biofilm formation first observed at 8 hours of allowed adhesion on PEEK, whereas no significant biofilm formation was seen on the other materials during the observed time period.

CONCLUSIONS

Although C. acnes is known to have a slow proliferation rate, the results of this investigation demonstrate that it can rapidly adhere to and form a biofilm on PEEK. These data suggest that the use of PEEK implants placed during spinal surgery may facilitate early intraoperative colonization, and subsequent infection, compared with metallic implants.

CLINICAL SIGNIFICANCE

The findings of this study suggest that PEEK may prove to be problematic as a choice of implant material in cases were C. acnes infection is a possibility.

Delayed periprosthetic collection after cervical disc arthroplasty

Cervical disc arthroplasty is a treatment option for symptomatic cervical disc disease. There is a paucity of literature on long-term safety outcomes, durability, and device-related failure rates. The M6-C artificial cervical disc is a device with titanium alloy endplates and a complex polymeric centerpiece. To date, trials have exhibited acceptable safety profiles.This case series describes the presentation, management, and pathological findings of a delayed prevertebral periprosthetic mass anterior to the M6-C disc. Four patients at 3 different institutions underwent cervical disc replacement with the M6-C disc. Two to seven years postoperatively, they presented with dysphagia secondary to a compressive mass anterior to the disc. Case notes were reviewed to collect data on symptoms, management, and outcomes. The patients were systemically well and presented with progressive dysphagia. They had imaging findings of a mass anterior to the disc. They underwent a decompressive procedure, with 2 patients undergoing device removal and fusion. In 2 cases, a soft-tissue mass was seen intraoperatively, with frank pus. In 3 cases, Propionibacterium acnes was identified and antibiotic treatment given. Histopathology demonstrated mixed inflammatory infiltrates with foreign body-type granulomas. Postoperatively, the dysphagia resolved.The development of delayed dysphagia in a patient with an M6-C disc should prompt investigation to identify a mass lesion. To the authors' knowledge, this is the first report of delayed infection, or suspected delayed-type hypersensitivity reaction, following M6-C disc implantation. It is important for this to be added to the device safety concerns. Further prospective studies are needed to establish the incidence and the long-term safety and failure rates of the M6-C disc.

Deep Infections After Pediatric Spinal Arthrodesis: Differences Exist with Idiopathic, Neuromuscular, or Genetic and Syndromic Cause of Deformity

BACKGROUND

Little is known about the rates, timing, and causative microorganisms of deep surgical site infections after spinal arthrodesis in patients with genetic and syndromic scoliosis compared with patients with adolescent idiopathic scoliosis and kyphosis or patients with neuromuscular scoliosis.

METHODS

We reviewed data from 1,353 patients who were <21 years of age and had undergone spinal arthrodesis for deformity correction by 1 surgeon from 2000 to 2015. Deformity causes were genetic, idiopathic, or neuromuscular. We identified patients who had undergone an unplanned surgical procedure for a deep surgical site infection that was early (≤90 days after the procedure) or late (>90 days after the procedure). We compared deep surgical site infection rates, timing, and causative microorganisms by deformity cause.

RESULTS

Deep surgical site infections occurred in 65 patients (4.8%): 4.2% for patients with genetic and syndromic scoliosis, 2.7% for patients with adolescent idiopathic scoliosis and kyphosis, and 10.0% for patients with neuromuscular scoliosis. Of the deep surgical site infections, 26 (40%) occurred early and 39 (60%) occurred late. The median times to deep surgical site infection onset were 51 days (range, 7 days to 7 years) in patients with genetic and syndromic scoliosis, 827 days (range, 10 days to 12 years) in patients with adolescent idiopathic scoliosis and kyphosis, and 45 days (range, 13 days to 6 years) in patients with neuromuscular scoliosis. Seventy-six microorganisms (41 gram-positive and 35 gram-negative) were isolated from 47 children with positive cultures; the most common was coagulase-negative Staphylococcus (n = 13). The ratio of gram-positive to gram-negative microorganisms was highest in patients with adolescent idiopathic scoliosis and kyphosis (4:1) and lowest in patients with genetic and syndromic scoliosis (0.5:1). In genetic and syndromic scoliosis, both early and late deep surgical site infections were more frequently caused by gram-negative bacteria. In neuromuscular scoliosis, early deep surgical site infections were more frequently caused by gram-negative bacteria, and late deep surgical site infections were more frequently caused by gram-positive bacteria. In adolescent idiopathic scoliosis and kyphosis, both early and late deep surgical site infections were more commonly caused by gram-positive bacteria. Methicillin-resistant Staphylococcus aureus was identified in 2 late deep surgical site infections in patients with neuromuscular scoliosis.

CONCLUSIONS

Deep surgical site infections were more common in genetic and syndromic scoliosis than in adolescent idiopathic scoliosis and kyphosis, but less common than in neuromuscular scoliosis. Adolescent idiopathic scoliosis and kyphosis had the highest ratio of late to early deep surgical site infections. Patients with genetic and syndromic scoliosis had predominantly gram-negative microorganisms, particularly in early deep surgical site infections. Methicillin-resistant S. aureus infection was rare, occurring in only 2 patients with neuromuscular scoliosis. Gram-negative and gram-positive prophylactic antibiotics may be indicated for patients with genetic and syndromic scoliosis after spinal arthrodesis.

LEVEL OF EVIDENCE

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

Cerebral empyema and abscesses due to Cutibacterium acnes

INTRODUCTION

Cutibacterium acnes is a commensal bacterium of the skin, frequently reported in prosthetic shoulder or spinal implant infections, but rarely in cranial and intracranial infections.

METHODS

We retrospectively reviewed patients with intracranial samples positive to Cutibacterium acnes managed in the neurosurgical units of our hospital of Lyon, France, between 2008-2016.

RESULTS

We included 29 patients, of whom 23 had empyema (with or without abscess), 17 had cranial osteomyelitis, and six only had abscess. Prior neurosurgery was reported in 28 patients, and the remaining patient had four spontaneous abscesses. Twelve patients had polymicrobial infections, including methicillin-susceptible Staphylococcus in 11 cases. The clinical diagnosis was difficult because of indolent and delayed symptoms: a CT scan or MRI was required. Thirteen patients (52%) had material at the infection site. All patients with bone flap implant or bones from biological banks had a bone flap-associated infection. Drainage was surgically performed in 25 cases or by CT scan-guided aspiration in four cases. All patients received an adapted antibiotic therapy (from three weeks to six months). The outcome was favorable in 28 patients. Three patients relapsed during the antibiotic therapy, requiring further surgery.

CONCLUSION

Cutibacterium acnes can be responsible for postoperative empyema and cerebral abscesses, with particular indolent forms, which make their diagnosis difficult. They are often polymicrobial and associated with bone flap osteomyelitis. Their outcome is favorable after drainage and adapted antibiotic therapy.

Is pseudarthrosis after spinal instrumentation caused by a chronic infection?

HYPOTHESIS

To assess whether a chronic bacterial infection is present in a subset of patients with pseudarthrosis after instrumented spinal fusion.

METHODS

This was a prospective diagnostic study including adult patients with previous instrumented spinal fusion. Patients underwent revision surgery for either pseudarthrosis or other causes (e.g. implant removal, curve progression or junctional kyphosis) (control group). Five separate biopsies were randomly collected, intraoperatively, from the pseudarthrosis site and cultivated under both aerobic (5 days) and anaerobic (14 days) conditions. If cultivation was positive in at least 2/5 tissue samples, the biopsy was sectioned and stained using peptide nucleic acid fluorescence in situ hybridization (PNA-FISH). Confocal laser scanning microscopy was used to examine the sections and visualize bacterial aggregates.

RESULTS

The study included 32 pseudarthrosis and 32 control patients. Cultivation yielded bacteria in at least 1/5 biopsies in 52% of patients with no difference between the groups (p = 1.0). Bacteria of the same species was found in at least 2/5 samples in seven pseudarthrosis patients and four controls (p = 0.509). Propionibacterium acnes was found in 8 of these 11 samples. Microscopy demonstrated tissue-embedded bacterial aggregates in two of these patients but with no inflammatory cells indicating an active infection. The presence of bacteria was not associated with the number of previous spinal procedures or the pre-revision fusion length (p ≥ 0.503).

CONCLUSIONS

Pseudarthrosis after instrumented spinal surgery was not significantly associated with the presence of bacteria at the pseudarthrosis site. Positive cultivation results are common after spinal instrumentation, but our results indicate that they rarely represent an organized infection. These slides can be retrieved under Electronic Supplementary Material.

Propionibacterium acnes Infection in Disc Material and Different Antibiotic Susceptibility in Patients With Lumbar Disc Herniation

BACKGROUND

Low back pain is an important, worldwide clinical problem from which human populations are suffering. It has been suggested that Propionibacterium acnes is associated with low back pain. The objective of this clinical study is to evaluate the P. acnes infection in the disc material and antibiotic susceptibility in patients with disc herniation.

METHODS

A total of 120 patients with disc herniation surgery were enrolled in the study. The samples were excited during discectomy and then cultured in both anaerobic and aerobic incubations. Minimum inhibitory concentration (MIC) was performed for determination of antibiotic susceptibility.

RESULTS

Of 120 samples, 60 (50%) samples were positive for microorganisms. Disc herniation was at the level of L4-L5 in 63 cases and L5-S1 in 57 cases.

CONCLUSIONS

According to the results and presence of P. acnes in more than 35% of the cultured samples, the presence of P. acnes in lumbar disc herniation is a suspected element leading to this condition. After analysis of the antibiotics, the lowest MIC value was identified for amoxicillin, ciprofloxacin, erythromycin, rifampicin, tetracycline, vancomycin; the moderate MIC value was for fusidic acid; and the highest MIC value was for gentamicin and trimethoprim.

Deep brain stimulation hardware-related infections: 10-year experience at a single institution

OBJECTIVE

Deep brain stimulation is an effective surgical treatment for managing some neurological and psychiatric disorders. Infection related to the deep brain stimulator (DBS) hardware causes significant morbidity: hardware explantation may be required; initial disease symptoms such as tremor, rigidity, and bradykinesia may recur; and the medication requirements for adequate disease management may increase. These morbidities are of particular concern given that published DBS-related infection rates have been as high as 23%. To date, however, the key risk factors for and the potential preventive measures against these infections remain largely uncharacterized. In this study, the authors endeavored to identify possible risk factors for DBS-related infection and analyze the efficacy of prophylactic intrawound vancomycin powder (VP).

METHODS

The authors performed a retrospective cohort study of patients who had undergone primary DBS implantation at a single institution in the period from December 2005 through September 2015 to identify possible risk factors for surgical site infection (SSI) and to assess the impact of perioperative (before, during, and after surgery) prophylactic antibiotics on the SSI rate. They also evaluated the effect of a change in the National Healthcare Safety Network's definition of SSI on the number of infections detected. Statistical analyses were performed using the 2-sample t-test, the Wilcoxon rank-sum test, the chi-square test, Fisher's exact test, or logistic regression, as appropriate for the variables examined.

RESULTS

Four hundred sixty-four electrodes were placed in 242 adults during 245 primary procedures over approximately 10.5 years; most patients underwent bilateral electrode implantation. Among the 245 procedures, 9 SSIs (3.7%) occurred within 90 days and 16 (6.5%) occurred within 1 year of DBS placement. Gram-positive bacteria were the most common etiological agents. Most patient- and procedure-related characteristics did not differ between those who had acquired an SSI and those who had not. The rate of SSIs among patients who had received intrawound VP was only 3.3% compared with 9.7% among those who had not received topical VP (OR 0.32, 95% CI 0.10-1.02, p = 0.04). After controlling for patient sex, the association between VP and decreased SSI risk did not reach the predetermined level of significance (adjusted OR 0.32, 95% CI 0.10-1.03, p = 0.06). The SSI rates were similar after staged and unstaged implantations.

CONCLUSIONS

While most patient-related and procedure-related factors assessed in this study were not associated with the risk for an SSI, the data did suggest that intrawound VP may help to reduce the SSI risk after DBS implantation. Furthermore, given the implications of SSI after DBS surgery and the frequency of infections occurring more than 90 days after implantation, continued follow-up for at least 1 year after such a procedure is prudent to establish the true burden of these infections and to properly treat them when they do occur.

Management of late-onset deep surgical site infection after instrumented spinal surgery

Background

There are no universally accepted protocols for the treatment of late-onset deep surgical site infection. This study retrospectively evaluates the methods of aggressive debridement with instrumentation retention, high vacuum closed-suction drain without irrigation, primary wound closure, and antibiotic therapy for the treatment of late-onset deep surgical site infection after instrumented spinal surgery.

Methods

A total of 4057 patients who underwent instrumented spinal surgeries were surveyed from January 2010 to June 2014. Surgical debridement was performed immediately after late-onset deep surgical site infection was identified. In addition to extended resection of the devitalized and necrotic tissue, the biofilms adhered to the surface of implants were removed meticulously and thoroughly. Primary wound closure was performed on each patient, and closed suction drains were maintained for about 7–10 days without irrigation. Antibiotic therapy was administered for 3 months according to the results of the pathogenic culture.

Results

Forty-two patients were identified as having late-onset deep surgical site infection. Staphylococcus aureus was the most common pathogen in this group. Seven patients with late-onset deep surgical site infection had negative bacterial culture results. Infections resolved in all patients. Forty-one patients retained their instrumentation, whereas 1 patient had the implants removed because of Staphylococcus aureus infection, which was found the implants loosening during debridement. Primary wound healing was found in all patients with no recurrence of infection during the follow-up periods.

Conclusions

A timely diagnosis, aggressive and meticulous debridement, high vacuum closed-suction drain, routine and adequate use of antibacterial agents are the keys to successfully resolving infection and keeping implants retention in the treatment of late-onset deep surgical site infection after instrumented spinal surgery.

The Composition and Structure of Biofilms Developed by Propionibacterium acnes Isolated from Cardiac Pacemaker Devices

The present study aimed to understand the biofilm formation mechanism of Propionibacterium acnes by analyzing the components and structure of the biofilms. P. acnes strains were isolated from the surface of explanted cardiac pacemaker devices that exhibited no clinical signs of infection. Culture tests using a simple stamp culture method (pressing pacemakers against the surface of agar plates) revealed frequent P. acnes colonization on the surface of cardiac pacemaker devices. P. acnes was isolated from 7/31 devices, and the isolates were categorized by multilocus sequence typing into five different sequence types (STs): ST4 (JK18.2), ST53 (JK17.1), ST69 (JK12.2 and JK13.1), ST124 (JK5.3), ST125 (JK6.2), and unknown ST (JK19.3). An in vitro biofilm formation assay using microtiter plates demonstrated that 5/7 isolates formed biofilms. Inhibitory effects of DNase I and proteinase K on biofilm formation varied among isolates. In contrast, dispersin B showed no inhibitory activity against all isolates. Three-dimensional live/dead imaging of P. acnes biofilms with different biochemical properties using confocal laser microscopy demonstrated different distributions and proportions of living and dead cells. Additionally, it was suggested that extracellular DNA (eDNA) plays a role in the formation of biofilms containing living cells. Ultrastructural analysis of P. acnes biofilms using a transmission electron microscope and atmospheric scanning electron microscope revealed leakage of cytoplasmic components along with cell lysis and fibrous structures of eDNA connecting cells. In conclusion, the biochemical properties and structures of the biofilms differed among P. acnes isolates. These findings may provide clues for establishing countermeasures against biofilm-associated infection by P. acnes.

The distribution of infection with Propionibacterium acnes is equal in patients with cervical and lumbar disc herniation

BACKGROUND

Cervical and back pains are important clinical problems affecting human populations globally. It is suggested that Propionibacterium acnes (P. acnes) is associated with disc herniation. The aim of this study is to evaluate the distribution of P. acnes infection in the cervical and lumbar disc material obtained from patients with disc herniation.

METHODS AND MATERIAL

A total of 145 patients with mean age of 45.21 ± 11.24 years who underwent micro-discectomy in cervical and lumbar regions were enrolled into the study. The samples were excited during the operation and then cultured in the anaerobic incubations. The cultured P. acnes were detected by 16S rRNA-based polymerase chain reaction.

RESULTS

In this study, 145 patients including 25 cases with cervical and 120 cases with lumbar disc herniation were enrolled to the study. There was no significant difference in the age of male and female patients (p = 0.123). P. acnes infection was detected in nine patients (36%) with cervical disc herniation and 46 patients (38.3%) with lumbar disc herniation and no significant differences were reported in P. acnes presence according to the disc regions (p = 0.508.). Moreover, there was a significant difference in the presence of P. acnes infection according to the level of lumbar disc herniation (p = 0.028).

CONCLUSION

According to the results, the presence of P. acnes is equal in patients with cervical and lumbar disc herniation. There was a significant difference in the distribution of P. acnes infection according to level of lumbar disc herniation.

LEVEL OF EVIDENCE

II.

Modic changes in the adjacent vertebrae due to disc material infection with Propionibacterium acnes in patients with lumbar disc herniation

INTRODUCTION

Modic changes (MCs) in vertebral bones are induced by two mechanisms of mechanical factors and infection. As Propionibacterium acnes (P. acnes) have been reported to be associated with LBP. The aim of this study is to evaluate the MCs in patients with disc herniation and positive for P. acnes.

METHODS AND MATERIAL

A total of 120 patients with disc herniation surgery were enrolled into the study. The samples were excised during discectomy and then cultured in both anaerobic and aerobic incubations. Gram staining was employed for investigation of all colonies. The cultured P. acnes were detected by 16S rRNA-based polymerase chain reaction (PCR). MCs of baseline MRI were evaluated.

RESULTS

In this study, 120 subjects (69 male and 51 female) with mean age of 43.15 ± 12.62 years were investigated. Sixty disc samples and eight muscle samples were positive for microorganisms. Moreover, 16S rDNA gene was identified in 46 (38.3%) disc samples. Moreover, 36/46 patients with P. acnes in their sample had MCs.

CONCLUSION

According to the results and presence of 36/46 MCs in patients with lumbar disc herniation, positive for P. acnes suggests that P. acnes can lead to edema on the vertebrae endplates near to infected area.

Bacterial Communities Associated with Atherosclerotic Plaques from Russian Individuals with Atherosclerosis

Atherosclerosis is considered a chronic disease of the arterial wall and is the major cause of severe disease and death among individuals all over the world. Some recent studies have established the presence of bacteria in atherosclerotic plaque samples and suggested their possible contribution to the development of cardiovascular disease. The main objective of this preliminary pilot study was to better understand the bacterial diversity and abundance in human atherosclerotic plaques derived from common carotid arteries of individuals with atherosclerosis (Russian nationwide group) and contribute towards the further identification of a main group of atherosclerotic plaque bacteria by 454 pyrosequencing their 16S ribosomal RNA (16S rRNA) genes. The applied approach enabled the detection of bacterial DNA in all atherosclerotic plaques. We found that distinct members of the order Burkholderiales were present at high levels in all atherosclerotic plaques obtained from patients with atherosclerosis with the genus Curvibacter being predominant in all plaque samples. Moreover, unclassified Burkholderiales as well as members of the genera Propionibacterium and Ralstonia were typically the most significant taxa for all atherosclerotic plaques. Other genera such as Burkholderia, Corynebacterium and Sediminibacterium as well as unclassified Comamonadaceae, Oxalobacteraceae, Rhodospirillaceae, Bradyrhizobiaceae and Burkholderiaceae were always found but at low relative abundances of the total 16S rRNA gene population derived from all samples. Also, we found that some bacteria found in plaque samples correlated with some clinical parameters, including total cholesterol, alanine aminotransferase and fibrinogen levels. Finally, our study indicates that some bacterial agents at least partially may be involved in affecting the development of cardiovascular disease through different mechanisms.

Etiology of bone and joint infections: a case series of 363 consecutive patients from an orthopaedic infection unit

BACKGROUND

Bone and joint infections remain a clinical challenge with potentially serious consequences. Nevertheless there is a lack of studies with strict criteria for diagnosis and etiology. The primary aim of this study was to determine the causative agents in orthopaedic infections using strict diagnostic criteria for infection and etiology. The secondary aim was to assess the timing of post-operative infections in relation to pathogens and to compare causative bacteria in different parts of the body.

METHODS

A retrospective registry study of 363 consecutive cases of bone and joint infections was performed. Microbiological data on sampling and culture results were registered.

RESULTS

Staphylococcus aureus dominated in both operated (45%) and non-operated (44%) patients, followed in frequency by coagulase-negative staphylococci (CoNS) in operated patients (11%) and beta-haemolytic streptococci in non-operated patients (16%) (p < 0.001). There were no polymicrobial infections in non-surgical cases (p < 0.001). For operated patients, Gram-negative bacilli were observed in 6%, almost exclusively isolated from the lower extremity. Propionibacterium spp. was the most common finding after spinal surgery. In 90/363 (25%), the agent responsible for the infection could not be defined according to the strict criteria used.

CONCLUSION

S. aureus dominated as etiological agent in all bone and joint infections, including operated patient given peri-operative prophylaxis. Improved timing of antibiotic prophylaxis seen after the introduction of the Swedish national project PRISS may have changed this. The number of infections with uncertain etiology was high, stressing the importance of more studies on diagnostics, as well as strict diagnostic algorithms.

Analysis of Postoperative Thoracolumbar Spine Infections in a Prospective Randomized Controlled Trial Using the Centers for Disease Control Surgical Site Infection Criteria

INTRODUCTION

Wound infections following spinal surgery place a high toll on both the patient and the healthcare system. Although several large series studies have examined the incidence and distribution of spinal wound infection, the applicability of these studies varies greatly since nearly every study is either retrospective and/or lacks standard inclusion criteria for defining surgical site infection. To address this void, we present results from prospectively gathered thoracolumbar spine surgery data for which the Centers for Disease Control (CDC) criteria were stringently applied to define a surgical site infection (SSI).

METHODS

A prospective randomized trial of 314 patients who underwent multilevel thoracolumbar spinal surgery with instrumentation followed by postoperative drain placement was completed (Takemoto et al., 2015). The trial consisted of two antibiotic arms: one for 24-hours, and the other for the duration of the drain; no differences were found between the arms. All infections meeting CDC criteria for SSI were included.

RESULTS

A total of 40 infections met CDC criteria for SSI, for an overall incidence of 12.7%. Of these, 20 (50%) were culture-positive. The most common organism was Staphylococcus aureus (4 total: methicillin-sensitive=2; methicillin-resistant=2), followed by coagulase-negative Staphylococcus (3 cases), Propionibacterium acnes and Escherichia coli (2 cases each). Six infections grew multiple organisms, most commonly involving coagulase-negative staphylococcus and enterococcus.

CONCLUSIONS

Our findings indicate that thoracolumbar SSI occurs at the higher end of the range cited in the literature (2-13%), which is largely based on retrospective data not subjected to the inclusivity of SSI as defined by the CDC. The three most common organisms in our analysis (S. aureus, P. acnes, E. coli) are consistent with previous reports. Staphylococcus aureus continues to be the most common causative organism and continued vigilance and searching for preventive measures need to be a high priority. This study provides Level I evidence.

Propionibacterium in Shoulder Arthroplasty: What We Think We Know Today

➤ Propionibacterium is a slow-growing gram-positive rod that is part of the normal skin microbiome but can be found on culture of specimens from a large number of patients having revision shoulder arthroplasty performed for pain, stiffness, and component loosening. ➤ Propionibacterium infections do not present with obvious signs of infection, such as swelling, erythema, drainage, or tenderness, but rather are of the so-called stealth type, presenting with unexplained pain, stiffness, or component loosening months to years after the index arthroplasty. ➤ Not all propionibacteria are the same: certain subtypes of Propionibacterium are enriched with virulence factors that may enhance deep infection. ➤ Because propionibacteria typically reside in the pilosebaceous glands of the oily skin of the chest and back, standard surgical skin preparation solutions and even perioperative intravenous antibiotics are often inadequate at sterilizing the incision site; therefore, other prophylactic measures such as meticulous implant handling to avoid contact with dermal structures need to be considered. ➤ Recovery of Propionibacterium from the surgical wounds requires that multiple specimens for culture be taken from different areas of the shoulder to reduce sampling error, and cultures should be held for two weeks on multiple culture media. ➤ Future research efforts can be focused on reducing the risk of implant infection and point-of-care methods for identifying Propionibacterium infections.

Treatment of Surgical Site Infection in Posterior Lumbar Interbody Fusion

STUDY DESIGN

A retrospective observational and case control study.

PURPOSE

To identify appropriate treatment options according to the types of surgical site infections (SSI) in instrumented posterior lumbar interbody fusion (PLIF).

OVERVIEW OF LITERATURE

There has been no agreement or consensus with regard to this matter.

METHODS

Thirty-two consecutive SSIs were included and followed for more than one year. The elapsed time to diagnosis (ETD) according to the type of SSI was analyzed. The treatment options for each type and consequent clinical results were reviewed. The risk factors of removing the implants were analyzed.

RESULTS

There were 6/32 (19%) superficial incisional, 6/32 (19%) deep incisional, and 20/32 (62%) organ/space infection cases (SII, DII, and O/SI, respectively) (p=0.002). ETD was 8.5±2.3 days in SII, 8.7±2.3 days in DII, and 164.5±131.1 days in O/SI (p=0.013). All cases of SII and DII retained implants and were treated by repeated irrigation and secondary closure. Among O/SIs, 10/20 were treated conservatively. Nine out of ten underwent posterior one stage simultaneous revision (POSSR) and in one case, the cage was removed anteriorly. Those who had ETDs longer than 3 months showed a significant risk of implant removal (p=0.008, odds ratio [OR]=40.3). The Oswestry disability index (ODI) improved from 47.3% to 33.8% in SII, from 55.0% to 32.3% in DII, and from 53.4% to 42.1% in O/SI (p=0.002). There was no difference among the three groups (p=0.106); however, there was a partial correlation between ETD and final ODI (r=0.382, p=0.034).

CONCLUSIONS

Latent O/SI was the most common type of SSI in PLIF. In cases of SII and DII, early aggressive wound management and secondary closure was effective and implant removal was not necessary. In some cases of O/SI, implant removal was unavoidable. However, implant removal could be averted by an earlier diagnosis. POSSR was feasible and safe. Functional outcomes were improved; however, disability increased as ETD increased.

Management of late (>1 y) deep infection after spinal fusion: a retrospective cohort study

BACKGROUND

The incidence of late infection published in the literature varies from 1% to 12% with varying definition of late infection (range, 3 mo to 1 y). Current evidence suggests implant removal and antibiotic therapy is necessary to clear these infections. A high incidence of late (>1 y) deep infection after instrumented spinal fusion was identified at our institution. We sought to evaluate the efficacy of our management of these patients.

METHODS

A total of 1390 patients underwent instrumented spinal fusion from 2000 to 2009. Forty-two patients developed deep infection >1 year after index procedure (3%) and had surgical debridement. Clinical records and microbiology reports were reviewed for details of operative and postoperative management.

RESULTS

Advanced imaging was only obtained in 6 patients (5 computed tomography, 1 magnetic resonance imaging). Offending organisms were identified in 39/42 patients, 27 of these grew Propionibacterium acnes. P. acnes grew in culture at a median of 6 days (range, 3 to 10 d), significantly longer than all other organisms, which grew in a median of 1 day (range, 0 to 8 d) (P<0.001). Implants were removed at the index hospitalization in 41 patients. Implant retention was attempted in 1 patient and failed. Primary closure was carried out in 37 patients; the remainder had undergone multiple debridements (4 planned, 1 unplanned). VAC closure was utilized in 2 patients. All patients were treated with organism-specific intravenous antibiotics and transitioned to oral antibiotics on average in 34 days (range, 2 to 186 d). Total length of antibiotic therapy was an average of 141 days (range, 34 to 413 d).

CONCLUSIONS

P. acnes was the most common organism identified and took nearly 1 week to grow in culture. Treatment is generally successful with thorough debridement, removal of implants, and antibiotic treatment.

LEVEL III

retrospective comparative study.

Propionibacterium acnes: from commensal to opportunistic biofilm-associated implant pathogen

Propionibacterium acnes is known primarily as a skin commensal. However, it can present as an opportunistic pathogen via bacterial seeding to cause invasive infections such as implant-associated infections. These infections have gained more attention due to improved diagnostic procedures, such as sonication of explanted foreign materials and prolonged cultivation time of up to 14 days for periprosthetic biopsy specimens, and improved molecular methods, such as broad-range 16S rRNA gene PCR. Implant-associated infections caused by P. acnes are most often described for shoulder prosthetic joint infections as well as cerebrovascular shunt infections, fibrosis of breast implants, and infections of cardiovascular devices. P. acnes causes disease through a number of virulence factors, such as biofilm formation. P. acnes is highly susceptible to a wide range of antibiotics, including beta-lactams, quinolones, clindamycin, and rifampin, although resistance to clindamycin is increasing. Treatment requires a combination of surgery and a prolonged antibiotic treatment regimen to successfully eliminate the remaining bacteria. Most authors suggest a course of 3 to 6 months of antibiotic treatment, including 2 to 6 weeks of intravenous treatment with a beta-lactam. While recently reported data showed a good efficacy of rifampin against P. acnes biofilms, prospective, randomized, controlled studies are needed to confirm evidence for combination treatment with rifampin, as has been performed for staphylococcal implant-associated infections.

Role of Sonication in the Microbiological Diagnosis of Implant-Associated Infections: Beyond the Orthopedic Prosthesis

Implant-associated infections are difficult-to-treat conditions associated with high morbidity, mortality and length of hospitalization. They are characterized by biofilm formation on implant surface, which makes the microbiological diagnosis difficult and requires a complete device removal for the correct management. The sonication method, which is based on the application of long-wave ultrasounds radiating in a liquid medium, has been recently validated for the diagnosis of prosthetic joint infections. Additionally, this technique has been considered a potential tool in order to improve the microbiological diagnosis of infections associated with other foreign bodies, such as breast, urinary, endovascular and cerebral implants. In the present study, the application of sonication in the setting of implant-associated infections other than orthopedics will be reviewed.

Propionibacterium persists in the skin despite standard surgical preparation

BACKGROUND

Propionibacterium acnes, which normally resides in the skin, is known to play a role in surgical site infection in orthopaedic surgery. Studies have suggested a persistence of propionibacteria on the skin surface, with rates of positive cultures ranging from 7% to 29% after surgical preparation. However, as Propionibacterium organisms normally reside in the dermal layer, these studies may underestimate the true prevalence of propionibacteria after surgical skin preparation. We hypothesized that, after surgical skin preparation, viable Propionibacterium remains in the dermis at a much higher rate than previously reported.

METHODS

Ten healthy male volunteers underwent skin preparation of the upper back with ChloraPrep (2% chlorhexidine gluconate and 70% isopropyl alcohol). Two 3-mm dermal punch biopsy specimens were obtained through the prepared skin and specifically cultured for P. acnes.

RESULTS

Seven volunteers had positive findings for Propionibacterium on dermal cultures after ChloraPrep skin preparation. The average time to positive cultures was 6.78 days.

CONCLUSIONS

This study found that Propionibacterium persists in the dermal tissue even after surface skin preparation with ChloraPrep. The 70% rate of persistence of propionibacteria after skin preparation is substantially higher than previously reported.

CLINICAL RELEVANCE

Propionibacteria are increasingly discussed as having an association with infection, implant failure, and degenerative disease. This study confirms the possibility that the dermal layer of skin may be the source of the bacteria.

Bacteria and bacterial DNA in atherosclerotic plaque and aneurysmal wall biopsies from patients with and without periodontitis

Background

Several studies have reported an association between chronic periodontitis (CP) and cardiovascular diseases. Detection of periodontopathogens, including red complex bacteria (RCB), in vascular lesions has suggested these bacteria to be involved in the pathogenesis of atherosclerosis and abdominal aortic aneurysms.

Objective

In this study, we investigate bacteria and their DNA in vascular biopsies from patients with vascular diseases (VD; i.e. abdominal aortic aneurysms, atherosclerotic carotid, and common femoral arteries), with and without CP.

Methods

DNA was extracted from vascular biopsies selected from 40 VD patients: 30 with CP and 10 without CP. The V3-V5 region of the 16S rDNA (V3-V5) was polymerase chain reaction (PCR)-amplified, and the amplicons were cloned into Escherichia coli, sequenced, and classified (GenBank and the Human Oral Microbiome database). Species-specific primers were used for the detection of Porphyromonas gingivalis. In addition, 10 randomly selected vascular biopsies from the CP group were subjected to scanning electron microscopy (SEM) for visualization of bacteria. Checkerboard DNA–DNA hybridization was performed to assess the presence of RCB in 10 randomly selected subgingival plaque samples from CP patients.

Results

A higher load and mean diversity of bacteria were detected in vascular biopsies from VD patients with CP compared to those without CP. Enterobacteriaceae were frequently detected in vascular biopsies together with cultivable, commensal oral, and not-yet-cultured bacterial species. While 70% of the subgingival plaque samples from CP patients showed presence of RCB, only P. gingivalis was detected in one vascular biopsy. Bacterial cells were seen in all 10 vascular biopsies examined by SEM.

Conclusions

A higher bacterial load and more diverse colonization were detected in VD lesions of CP patients as compared to patients without CP. This indicated that a multitude of bacterial species both from the gut and the oral cavity, rather than exclusively periodontopathogens, may be involved as additional risk factors in the pathogenesis of VD.

Bacteriology and Risk Factors for Development of Late (Greater Than One Year) Deep Infection Following Spinal Fusion With Instrumentation

STUDY DESIGN

Retrospective cohort review.

OBJECTIVES

To evaluate patients who underwent instrumented spinal fusion procedures and compare late (more than 1 year) and early infection (less than 1 year).

SUMMARY OF BACKGROUND DATA

Centers for Disease Control and Prevention criteria for surgical site infections with implants include infections occurring at less than 1 year postoperatively. The authors observed a high rate of deep infection at more 1 year after instrumented spinal fusion. Retrospective review was conducted to determine whether differences in bacteriology, patient demographics, or surgical factors exist between late and early infection.

METHODS

A total of 1,390 patients underwent spinal fusion with instrumentation from 2000 to 2009. Deep infection requiring operative debridement occurred in 112 patients (70 at less than 1 year and 42 at more than 1 year after the index surgery). Clinical, operative, and microbiology reports were reviewed and logistic regression was performed to evaluate the relationship between these factors and time of infection.

RESULTS

The most common organisms in the greater than 1 year group were Propionibacterium acnes, compared with Staphylococcus aureus in the less than 1 year group. The odds of late infection in the P acnes group were 15.5 (95% confidence interval [CI], 4.36-54.72) times the odds among all other organisms (p < .0001). Patient demographics and surgical factors were not different between groups. Among all patients, the infection rate was significantly higher in patients who received stainless-steel implants (11.56%) compared with those who received titanium implants (3.53%) (p < .0001). In univariate analysis, the odds of late infection in the stainless-steel group were 6.09 (95% CI, 1.62-39.88) times the odds in the titanium group (p = .0042). However, in multivariate analysis, controlling for organism type reduced the odds ratio to 4.62 (95% CI, .53-40.14), with only a trend to significance (p = .1656).

CONCLUSIONS

Propionibacterium acnes was more commonly identified in late infection. Patients with stainless-steel implants had a higher incidence of late infection than those with titanium implants, but this was not significant after controlling for organism type.

Outcome and treatment of postoperative spine surgical site infections: predictors of treatment success and failure

BACKGROUND

Surgical site infection (SSI) is an important complication after spine surgery. The management of SSI is characterized by significant variability, and there is little guidance regarding an evidence-based approach. The objective of this study was to identify risk factors associated with treatment failure of SSI after spine surgery.

PATIENTS AND METHODS

A total of 225 consecutive patients with SSI after spine surgery between July 2005 and July 2010 were studied retrospectively. Patients were treated with aggressive surgical debridement and prolonged antibiotic therapy. Outcome and risk factors were analyzed in 197 patients having 1 year of follow-up. Treatment success was defined as resolution within 90 days.

RESULTS

A total of 126 (76 %) cases were treated with retention of implants. Forty-three (22 %) cases had treatment failure with five (2.5 %) cases resulting in death. Lower rates of treatment success were observed with late infection (38 %), fusion with fixation to the ilium (67 %), Propionibacterium acnes (43 %), poly microbial infection (68 %), >6 operated spinal levels (67 %), and instrumented cases (73 %). Higher rates of early resolution were observed with superficial infection (93 %), methicillin-sensitive Staphylococcus aureus (95 %), and <3 operated spinal levels (88 %). Multivariate logistic regression revealed late infection was the most significant independent risk factor associated with treatment failure. Superficial infection and methicillin-sensitive Staphylococcus aureus were predictors of early resolution.

CONCLUSION

Postoperative spine infections were treated with aggressive surgical debridement and antibiotic therapy. High rates of treatment failure occurred in cases with late infection, long instrumented fusions, polymicrobial infections, and Propionibacterium acnes. Removal of implants and direct or staged re-implantation may be a useful strategy in cases with high risk of treatment failure.

Origin of propionibacterium in surgical wounds and evidence-based approach for culturing propionibacterium from surgical sites

BACKGROUND

To explore the origin of Propionibacterium in surgical wounds and to suggest an optimized strategy for culturing this organism at the time of revision surgery, we studied the presence of this organism on the skin and in the surgical wounds of patients who underwent revision arthroplasty for reasons other than apparent infection.

METHODS

Specimens were cultured in broth and on aerobic and anaerobic media. The presence and degree of positivity of Propionibacterium cultures were correlated with sex. The results of dermal and deep cultures were correlated. Times to positivity and the yields of each media type and specimen source were investigated.

RESULTS

Propionibacterium grew in twenty-three of thirty cultures of specimens obtained preoperatively from the unprepared epidermis over the area where a skin incision was going to be made for a shoulder arthroplasty; males had a greater average degree of positivity than females (p &lt; 0.002). Twelve of twenty-one male subjects and zero of twenty female subjects who had cultures of dermal specimens obtained during revision shoulder arthroplasty had positive findings for Propionibacterium (p = 0.0001). Twelve of twenty male subjects and only one of twenty female subjects had positive deep cultures (p = 0.0004). The positivity of dermal cultures for Propionibacterium was significantly associated with the positivity of deep cultures for this organism (p = 0.0001). If Propionibacterium was present in deep tissues, it was likely that it would be recovered by culture if four different specimens were obtained and cultured for a minimum of seventeen days on three different media: aerobic, anaerobic, and broth.

CONCLUSIONS

Because the surgical incision of dermal sebaceous glands may be a source of Propionibacterium in deep wounds, strategies for minimizing the risk of Propionibacterium infections may need to be directed at minimizing the contamination of surgical wounds from these bacteria residing in rather than on the skin. Obtaining at least four specimens, observing them for seventeen days, and using three types of culture media optimize the recovery of Propionibacterium at the time of revision surgery.

Propionibacterium acnes: an underestimated pathogen in implant-associated infections

The role of Propionibacterium acnes in acne and in a wide range of inflammatory diseases is well established. However, P. acnes is also responsible for infections involving implants. Prolonged aerobic and anaerobic agar cultures for 14 days and broth cultures increase the detection rate. In this paper, we review the pathogenic role of P. acnes in implant-associated infections such as prosthetic joints, cardiac devices, breast implants, intraocular lenses, neurosurgical devices, and spine implants. The management of severe infections caused by P. acnes involves a combination of antimicrobial and surgical treatment (often removal of the device). Intravenous penicillin G and ceftriaxone are the first choice for serious infections, with vancomycin and daptomycin as alternatives, and amoxicillin, rifampicin, clindamycin, tetracycline, and levofloxacin for oral treatment. Sonication of explanted prosthetic material improves the diagnosis of implant-associated infections. Molecular methods may further increase the sensitivity of P. acnes detection. Coating of implants with antimicrobial substances could avoid or limit colonization of the surface and thereby reduce the risk of biofilm formation during severe infections. Our understanding of the role of P. acnes in human diseases will likely continue to increase as new associations and pathogenic mechanisms are discovered.

Infection with spinal instrumentation: Review of pathogenesis, diagnosis, prevention, and management

Background:

Instrumentation has become an integral component in the management of various spinal pathologies. The rate of infection varies from 2% to 20% of all instrumented spinal procedures. Every occurrence produces patient morbidity, which may adversely affect long-term outcome and increases health care costs.

Methods:

A comprehensive review of the literature from 1990 to 2012 was performed utilizing PubMed and several key words: Infection, spine, instrumentation, implant, management, and biofilms. Articles that provided a current review of the pathogenesis, diagnosis, prevention, and management of instrumented spinal infections over the years were reviewed.

Results:

There are multiple risk factors for postoperative spinal infections. Infections in the setting of instrumentation are more difficult to diagnose and treat due to biofilm. Infections may be early or delayed. C Reactive Protein (CRP) and Magnetic Resonance Imaging (MRI) are important diagnostic tools. Optimal results are obtained with surgical debridement followed by parenteral antibiotics. Removal or replacement of hardware should be considered in delayed infections.

Conclusions:

An improved understanding of the role of biofilm and the development of newer spinal implants has provided insight in the pathogenesis and management of infected spinal implants. This literature review highlights the mechanism, pathogenesis, prevention, and management of infection after spinal instrumentation. It is important to accurately identify and treat postoperative spinal infections. The treatment is often multimodal and prolonged.

Should we start treating chronic low back pain with antibiotics rather than with pain medications?

For those of us who have read the 2 recently published articles by a Danish - British research group, it might appear that we are observing an impending paradigm shift on the origins of chronic low back pain. The results of this research indicate, that chronic low back pain associated with bone marrow edema in vertebral endplates that are adjacent to herniated intervertebral discs may be caused by infections with anaerobic bacteria of low virulence. According to these articles, treatment with certain antibiotics is significantly more effective than placebo against this low back pain. If these findings are to hold true in repeat studies by other researchers, they stand to fundamentally change our concepts of low back pain, degenerative disc disease and in consequence the suitable therapies for these entities. It may in fact require pain specialists to become familiarized with the details of antibiotic treatments and their specific risks in order to be able to properly counsel their patients. While this seems hard to believe at first glance, bacteria have been implicated in the pathogenesis of other conditions that do not primarily impose as infectious diseases such as gastric ulcers. While the authors refer to a few previous studies pointing into the same direction, the relevant research is really only from one group of collaborating scientists. Therefore, before we start prescribing antibiotics for chronic low back pain, it is imperative that other researchers in different institutions confirm these results.

Intercellular adhesion molecule-1 (ICAM-1, CD54) is increased in adhesive capsulitis

BACKGROUND

The purpose of this study was to investigate the presence of intercellular adhesion molecule-1 (ICAM-1) in shoulders with adhesive capsulitis ("frozen shoulder").

METHODS

Glenohumeral capsular tissue was obtained from twenty-six patients (seventeen with adhesive capsulitis and nine controls), and ICAM-1 was evaluated with use of oligonucleotide arrays, real-time reverse transcription-polymerase chain reaction (RT-PCR), and immunohistochemistry. ICAM-1 was also evaluated in synovial fluid with use of western blotting (six patients with adhesive capsulitis and two controls) and in peripheral blood with use of an enzyme-linked immunosorbent assay (ELISA) (thirty-two patients with adhesive capsulitis, twenty with diabetes mellitus, and fourteen controls). The effect of ICAM-1 treatment on gene expression of cytokines related to inflammation and fibrosis was evaluated in cultured normal human synovial cells.

RESULTS

The level of ICAM-1 was significantly greater in capsular tissue from the glenohumeral joint of patients with adhesive capsulitis compared with controls as measured by oligonucleotide array analysis (0.12 ± 0.01 compared with 0.09 ± 0.00 arbitrary units) (p = 0.001), real-time RT-PCR (1.70 ± 0.19 compared with 0.67 ± 0.24 arbitrary units) (p < 0.05), and immunohistochemical staining. ICAM-1 was also significantly increased in the synovial fluid of patients with adhesive capsulitis (1.70 ± 0.18 arbitrary units) compared with normal controls (0.48 ± 0.17) (p < 0.05) and in serum of patients with adhesive capsulitis (633.22 ± 59.14 ng/mL) and patients with diabetes mellitus (671.25 ± 27.08 ng/mL) compared with controls (359.86 ± 44.29 ng/mL) (p < 0.05). Gene expression of cytokines related to inflammation and fibrosis in synoviocytes cultured in vitro was greater after three days of treatment with ICAM-1 and with ICAM-1 with glucose compared with untreated cells.

CONCLUSIONS

ICAM-1 was increased in patients with adhesive capsulitis, similar to the increase that has been reported in patients with diabetes mellitus.

Propionibacterium acnes: infection beyond the skin

Propionibacterium acnes is a Gram-positive bacterium that forms part of the normal flora of the skin, oral cavity, large intestine, the conjunctiva and the external ear canal. Although primarily recognized for its role in acne, P. acnes is an opportunistic pathogen, causing a range of postoperative and device-related infections. These include infections of the bones and joints, mouth, eye and brain. Device-related infections include those of joint prostheses, shunts and prosthetic heart valves. P. acnes may play a role in other conditions, including inflammation of the prostate leading to cancer, SAPHO (synovitis, acne, pustulosis, hyperostosis, osteitis) syndrome, sarcoidosis and sciatica. If an active role in these conditions is established there are major implications for diagnosis, treatment and protection. Genome sequencing of the organism has provided an insight into the pathogenic potential and virulence of P. acnes.

Propionibacterium acnes delayed infection following spinal surgery with instrumentation

Propionibacterium acnes detection in culture media was previously considered a contamination but recently its infectious role was discovered in post-spinal surgery infections. P. acnes might be introduced during surgery. Its diagnosis is based on non-specific clinical signs, image indications of infection, and the conclusive microbiological sign. Furthermore, its diagnosis is difficult because of slow growth rate and low virulence, delaying its presentation. Usually, the infection is manifested after a couple of months or years. Here, a 65-year-old man presented with drainage at the site of instrumented spinal surgery performed 13 years ago. P. acnes infection was confirmed by culture with extended incubation. Our review of the literature revealed only two other reported cases of delayed P. acnes infection presenting a decade following a spinal surgery with instrumentation. This article sheds light on such delayed infections and discusses their presentation and management.

Role of rifampin against Propionibacterium acnes biofilm in vitro and in an experimental foreign-body infection model

Propionibacterium acnes is an important cause of orthopedic-implant-associated infections, for which the optimal treatment has not yet been determined. We investigated the activity of rifampin, alone and in combination, against planktonic and biofilm P. acnes in vitro and in a foreign-body infection model. The MIC and the minimal bactericidal concentration (MBC) were 0.007 and 4 μg/ml for rifampin, 1 and 4 μg/ml for daptomycin, 1 and 8 μg/ml for vancomycin, 1 and 2 μg/ml for levofloxacin, 0.03 and 16 μg/ml for penicillin G, 0.125 and 512 μg/ml for clindamycin, and 0.25 and 32 μg/ml for ceftriaxone. The P. acnes minimal biofilm eradication concentration (MBEC) was 16 μg/ml for rifampin; 32 μg/ml for penicillin G; 64 μg/ml for daptomycin and ceftriaxone; and ≥128 μg/ml for levofloxacin, vancomycin, and clindamycin. In the animal model, implants were infected by injection of 10⁹ CFU P. acnes in cages. Antimicrobial activity on P. acnes was investigated in the cage fluid (planktonic form) and on explanted cages (biofilm form). The cure rates were 4% for daptomycin, 17% for vancomycin, 0% for levofloxacin, and 36% for rifampin. Rifampin cured 63% of the infected cages in combination with daptomycin, 46% with vancomycin, and 25% with levofloxacin. While all tested antimicrobials showed good activity against planktonic P. acnes, for eradication of biofilms, rifampin was needed. In combination with rifampin, daptomycin showed higher cure rates than with vancomycin in this foreign-body infection model.