Clinical and epidemiological differences between implant-associated and implant-free orthopaedic infections

A Comparison of the Minimum Inhibitory Concentration of Antibiotics in Staphylococcus Species Isolated From Orthopedic and Respiratory Medicine Infections

INTRODUCTION

Antibiotic susceptibility is very important for the successful treatment of orthopedic infections, particularly for implant-related infections. While the minimum inhibitory concentrations (MICs) of Staphylococcus species were well investigated for the isolates from the respiratory tract, investigations for orthopedic pathogens are very limited. We investigated the antibiotic MIC values of Staphylococcus species isolated from orthopedic infections and compared them with those of respiratory medicine isolates used as a control.

METHODS

The MICs of vancomycin (VCM), arbekacin (ABK), teicoplanin (TEIC), linezolid (LZD), and rifampicin (RFP) of a total of consecutive 259 (89 orthopedic and 170 respiratory) Staphylococcus speciesisolated in our laboratory from January 2013 to July 2016 were retrospectively reviewed. Differences between the MICs of each antibiotic in orthopedic and respiratory samples were determined.

RESULTS

The number of methicillin-sensitive Staphylococcus aureus (MSSA) with a VCM MIC of <0.5 μg/mL among respiratory isolates was significantly higher than that among orthopedic isolates, while those with a MIC of 2 μg/mL were significantly lower (P = 0.0078). The proportion of methicillin-resistant coagulase-negative staphylococci (MRCNS) isolates with a VCM MIC of 2 μg/mL was significantly higher in orthopedic samples than that of methicillin-resistant Staphylococcus aureus (MRSA) (P < 0.001) in respiratory isolates. The proportion of MRCNS orthopedic isolates with an RFP MIC of >2 μg/mL was significantly higher (P = 0.0058) than that of other orthopedic staphylococci.

CONCLUSIONS

The VCM MICs of Staphylococcus species from orthopedic infections were higher than those of respiratory samples, particularly MRCNS from implant-related samples.

A Rare Pathogen of Bones and Joints: A Systematic Review of Osteoarticular Infections Caused by Gemella morbillorum

Osteoarticular infections (OAIs) caused by Gemella morbillorum (G. morbillorum) are a rare clinical entity. This study aimed to review all published cases of OAI due to G. morbillorum. A systematic review of PubMed, Scopus, and Cochrane Library was conducted to report the demographic and clinical characteristics, microbiological data, management, and outcome of OAIs caused by G. morbillorum in the adult population. A total of 16 studies reporting on 16 patients were included in this review. Eight patients had arthritis and eight patients had osteomyelitis/discitis. The most reported risk factors were immunosuppression, poor dental hygiene/dental infections, and recent gastrointestinal (GI) endoscopy. Five cases of arthritis occurred in a native joint while three patients had prostheses. The potential source of G. morbillorum infection was documented in more than half of the cases (56%) (most commonly odontogenic and GI sources (25% and 18%, respectively). The knee and hip joints were the most frequently affected joints in patients with arthritis, while the thoracic vertebrae were the most common sites for osteomyelitis/discitis. The blood cultures were positive in three patients with arthritis (37.5%) and five patients with osteomyelitis/discitis (62.5%). Associated endovascular infection was found in five patients with bacteremia. Contiguous spread (adjacent mediastinitis) was documented in two patients with sternal osteomyelitis and thoracic vertebral osteomyelitis. Surgical interventions were performed for 12 patients (75%). Most strains of G. morbillorum were susceptible to penicillin and cephalosporins. All patients with reported outcomes had achieved complete recovery. G. morbillorum is an emerging pathogen for OAIs in certain susceptible populations with specific risk factors. This review reported the demographic, clinical, and microbiological features of OAIs caused by G. morbillorum. A careful evaluation of an underlying infectious focus is warranted to control the source. When G. morbillorum bacteremia is present, it is also necessary to have a high index of suspicion to rule out an associated endovascular infection.

Study protocol: short against long antibiotic therapy for infected orthopedic sites - the randomized-controlled SALATIO trials

BACKGROUND

Few studies address the appropriate duration of post-surgical antibiotic therapy for orthopedic infections; with or without infected residual implants. We perform two similar randomized-clinical trials (RCT) to reduce the antibiotic use and associated adverse events.

METHODS

Two unblinded RCTs in adult patients (non-inferiority with a margin of 10%, a power of 80%) with the primary outcomes "remission" and "microbiologically-identical recurrences" after a combined surgical and antibiotic therapy. The main secondary outcome is antibiotic-related adverse events. The RCTs allocate the participants between 3 vs. 6 weeks of post-surgical systemic antibiotic therapy for implant-free infections and between 6 vs. 12 weeks for residual implant-related infections. We need a total of 280 episodes (randomization schemes 1:1) with a minimal follow-up of 12 months. We perform two interim analyses starting approximately after 1 and 2 years. The study approximatively lasts 3 years.

DISCUSSION

Both parallel RCTs will enable to prescribe less antibiotics for future orthopedic infections in adult patients.

TRIAL REGISTRATION

ClinicalTrial.gov NCT05499481. Registered on 12 August 2022.

PROTOCOL VERSION

2 (19 May 2022).

Biofilm formation and inflammatory potential of Staphylococcus saccharolyticus: A possible cause of orthopedic implant-associated infections

Staphylococcus saccharolyticus, a coagulase-negative staphylococcal species, has some unusual characteristics for human-associated staphylococci, such as slow growth and its preference for anoxic culture conditions. This species is a relatively abundant member of the human skin microbiota, but its microbiological properties, as well as the pathogenic potential, have scarcely been investigated so far, despite being occasionally isolated from different types of infections including orthopedic implant-associated infections. Here, we investigated the growth and biofilm properties of clinical isolates of S. saccharolyticus and determined host cell responses. Growth assessments in anoxic and oxic conditions revealed strain-dependent outcomes, as some strains can also grow aerobically. All tested strains of S. saccharolyticus were able to form biofilm in a microtiter plate assay. Strain-dependent differences were determined by optical coherence tomography, revealing that medium supplementation with glucose and sodium chloride enhanced biofilm formation. Visualization of the biofilm by confocal laser scanning microscopy revealed the role of extracellular DNA in the biofilm structure. In addition to attached biofilms, S. saccharolyticus also formed bacterial aggregates at an early stage of growth. Transcriptome analysis of biofilm-grown versus planktonic cells revealed a set of upregulated genes in biofilm-embedded cells, including factors involved in adhesion, colonization, and competition such as epidermin, type I toxin-antitoxin system, and phenol-soluble modulins (beta and epsilon). To investigate consequences for the host after encountering S. saccharolyticus, cytokine profiling and host cell viability were assessed by infection experiments with differentiated THP-1 cells. The microorganism strongly triggered the secretion of the tested pro-inflammatory cyto- and chemokines IL-6, IL-8, and TNF-alpha, determined at 24 h post-infection. S. saccharolyticus was less cytotoxic than Staphylococcus aureus. Taken together, the results indicate that S. saccharolyticus has substantial pathogenic potential. Thus, it can be a potential cause of orthopedic implant-associated infections and other types of deep-seated infections.

The epidemiology of fracture-related infections in Germany

The epidemiology of fracture-related infection (FRI) is unknown, which makes it difficult to estimate future demands and evaluate progress in infection prevention. Therefore, we aimed to determine the nationwide burden’s development over the last decade as a function of age group and gender. FRI prevalence as a function of age group and gender was quantified based on annual ICD-10 diagnosis codes from German medical institutions between 2008 through 2018, provided by the Federal Statistical Office of Germany (Destatis). The prevalence of FRI increased by 0.28 from 8.4 cases per 100,000 inhabitants to 10.7 cases per 100,000 inhabitants between 2008 and 2018. The proportion of fractures resulting in FRI increased from 1.05 to 1.23%. Gender distribution was equal. Patients aged 60–69 years and 70–79 years comprised the largest internal proportion with 20.2% and 20.7%, respectively, whereby prevalence increased with age group. A trend towards more diagnoses in older patients was observed with a growth rate of 0.63 for patients older than 90 years. Increasing rates of fracture-related infection especially in older patients indicate an upcoming challenge for stakeholders in health care systems. Newly emerging treatment strategies, prevention methods and interdisciplinary approaches are strongly required.

Osteoarticular infections: a specific program for older patients?

BACKGROUND

With the increasing number of elderly patients, arthroplasties, fractures and diabetic foot infections, the worldwide number of osteoarticular infections (OAI) among the elderly is concomitantly expected to rise.

AIMS

We explore existing scientific knowledge about OAI in the frail elderly population.

METHODS

We performed a literature search linking OAIs to geriatric patients and comparing elderly patients (> 65 years) with average adults (range 18-65 years).

RESULTS

In this literature, financial aspects, comparison of diverse therapies on quality of life, reimbursement policies, or specific guidelines or nursing recommendations are missing. Age itself was not an independent factor related to particular pathogens, prevention of OAI, nursing care, and outcomes of OAI. However, geriatric patients were significantly more exposed to adverse events of therapy. They had more co-morbidities and more conservative surgery for OAI.

CONCLUSION

Available literature regarding OAI management among elderly patients is sparse. In recent evaluations, age itself does not seem an independent factor related to particular epidemiology, pathogens, prevention, nursing care, rehabilitation and therapeutic outcomes of OAI. Future clinical research will concern more conservative surgical indications, but certainly reduce inappropriate antibiotic use.

Interleukin-1β and tumor necrosis factor are essential in controlling an experimental orthopedic implant-associated infection

Orthopedic implant-associated infection (OIAI) is a major complication that leads to implant failure. In preclinical models of Staphylococcus aureus OIAI, osteomyelitis and septic arthritis, interleukin-1α (IL-1α), IL-1β, and tumor necrosis factor (TNF) are induced, but whether they have interactive or distinctive roles in host defense are unclear. Herein, a S. aureus OIAI model was performed in mice deficient in IL-1α, IL-1β, or TNF. Mice deficient in IL-1β or TNF (to a lesser extent) but not IL-1α had increased bacterial burden at the site of the OIAI throughout the 28-day experiment. IL-1β and TNF had a combined and critical role in host defense as mice deficient in both IL-1R and TNF (IL-1R/TNF-deficient mice) had a 40% mortality rate, which was associated with markedly increased bacterial burden at the site of the OIAI infection. Finally, IL-1α- and IL-1β-deficient mice had impaired neutrophil recruitment whereas IL-1β-, TNF-, and IL-1R/TNF-deficient mice all had impaired recruitment of both neutrophils and monocytes. Therefore, IL-1β and TNF contributed to host defense against S. aureus OIAI and neutrophil recruitment was primarily mediated by IL-1β and monocyte recruitment was mediated by both IL-1β and TNF.

Should antibiotic prophylaxis before orthopedic implant surgery depend on the duration of pre-surgical hospital stay?

Background

Prolonged hospital stay before surgery is a risk for colonization with antibiotic-resistant microorganisms and possible antibiotic-resistant surgical site infections (SSI), which lacks acknowledgement in international guidelines for perioperative antibiotic prophylaxis.

Method

Retrospective cohort study focusing on prophylaxis-resistant SSI in adult orthopedic implant patients; with emphasis on length of hospital stay prior to the index surgery.

Results

We enrolled 611 cases of SSI (median age, 65 years; 241 females and 161 immune-suppressed) in four large implant groups: arthroplasties (n = 309), plates (n = 127), spondylodeses (n = 31), and nails (n = 46). The causative pathogen was resistant to the perioperative antibiotic prophylaxis regimen in 307 cases (307/611; 50%), but the length of pre-surgical hospitalization did not influence the incidences of prophylaxis-resistant SSIs. These incidences were (107/211;51%) for the admission day, (170/345;49%) within 10 days of delay, (19/35;54%) between 10 and 20 days, and (11/20; 55%) beyond 20 days of hospital stay before surgery. The corresponding incidences of methicillin-resistant staphylococci were 13%, 14%, 17%, and 5%, respectively. In adjusted group comparisons, the length of prior hospital stay was equally unrelated to future prophylaxis-resistant SSI (odds ratio 1.0, 95% confidence interval 0.99-1.01).

Conclusions

In our retrospective cohort of orthopedic implant SSI, the length of pre-surgical hospital stay was unrelated to the incidence of prophylaxis-resistant pathogens.

Bacteriological relevance of linezolid vs. vancomycin in postoperative empirical treatment of osteoarticular infections: a retrospective single-center study

BACKGROUND

In 2015, our center replaced vancomycin with linezolid for the postoperative empirical treatment of osteoarticular infections (OAI).

OBJECTIVES

To assess the bacteriological relevance of linezolid for orthopedic postoperative probabilistic antibiotic therapy.

METHODS

Analysis of an observational cohort of patients empirically treated with a combination of linezolid and piperacillin/tazobactam during the immediate postoperative stage for an OAI between July 1^st 2015 and July 1^st 2016, in a French reference center.

RESULTS

Seventy-seven of 126 patients who received a probabilistic postoperative combination of linezolid with piperacillin/tazobactam had microbiological proof of infection. Sixty-six of 77 OAI involved material, including an osteosynthesis in 45 cases (68%) and prosthesis in 21 cases (32%). Infection was due to Gram-positive bacteria in 62 cases (80.5%), mostly S. aureus (n=32, 41.6%), and S. epidermidis (n=14, 18.2%) accounting for 74.2% of Gram-positive bacteria. Among 14 OAI due to S. epidermidis, 11 (78.6%) were due to methicillin-resistant strains. All the S. aureus and S. epidermidis strains were susceptible to linezolid (MICs ≤ 4 mg/L), except in one patient previously treated with linezolid who was infected with a linezolid-resistant S. epidermidis strain (MIC > 256 mg/L).

CONCLUSION

Linezolid can be used empirically in postoperative antibiotic therapy of OAI before obtaining definitive microbial results. Although linezolid resistance is rare in this population, previous oxazolidinone treatment should be documented before initiation of probabilistic postoperative treatment to highlight potential linezolid resistance.