Conservative medical therapy of infections following osteosynthesis: a retrospective analysis of a six-year experience

Chronic Suppressive Antibiotic Treatment for Staphylococcal Bone and Joint Implant-Related Infections

Prosthetic joint infection (PJI) and fracture-related infection (FRI) are difficult-to-treat conditions in patients with severe comorbidity or significant surgical risk. In cases not eligible for standard strategy, debridement procedures with the retention of prosthesis or internal fixation device, combined with long-term antibiotic treatment and subsequent indefinite chronic oral antimicrobial suppression (COAS), can be the only reasonable choice. The aim of this study was to investigate the role of COAS and its follow-up in the management of these cases. We retrospectively analyzed a cohort of 16 patients with a follow-up of at least 6 months (mean age 75 yo, 9F, 7M, 11 PJI, 5 FRI). All microbiological isolates were tetracycline-susceptible staphylococci and for this reason a minocycline-based COAS was adopted after debridement and 3 months of antibiogram-guided antibiotic treatment. Patient monitoring was carried out on a clinical basis, with bimonthly execution of the inflammation indices and serial radiolabeled leukocyte scintigraphy (LS). The overall median time of COAS follow-up was 15 months (min 6-max 30). Moreover, 62.5% of patients were still taking COAS with no relapse after cure at the last evaluation available. Clinical failure with a relapse of the infection was observed in 37.5% of patients; interestingly, 50% of them had previously stopped COAS due to side effects of the antibiotic used. In the COAS follow-up, a combination of clinical, laboratory and LS evaluation seems to monitor the infection properly. COAS can be considered as an interesting approach in patients not suitable for standard treatments of PJI or FRI but it requires careful monitoring.

Biofilm-Related Infections in Gram-Positive Bacteria and the Potential Role of the Long-Acting Agent Dalbavancin

Infections caused by Gram-positive bacteria are a major public health problem due to their increasing resistance to antibiotics. Staphylococcus and Enterococcus species' resistance and pathogenicity are enhanced by their ability to form biofilm. The biofilm lifestyle represents a significant obstacle to treatment because bacterial cells become highly tolerant to a wide range of antimicrobial compounds normally effective against their planktonic forms. Thus, novel therapeutic strategies targeting biofilms are urgently needed. The lipoglycopeptide dalbavancin is a long-acting agent for treating acute bacterial skin and skin structure infections caused by a broad range of Gram-positive pathogens. Recent studies have shown promising activity of dalbavancin against Gram-positive biofilms, including methicillin-resistant S. aureus (MRSA), methicillin-resistant S. epidermidis (MRSE), and vancomycin-susceptible enterococci. This review outlines the mechanisms regulating biofilm development in Staphylococcus and Enterococcus species and the clinical impact of biofilm-related infections. In addition, it discusses the clinical implications and potential therapeutic perspectives of the long-acting drug dalbavancin against biofilm-forming Gram-positive pathogens.

Haematogenous prosthetic knee infections: Prospective cohort study of 58 patients

BACKGROUND

Prosthetic joint infection (PJI) is a rare (incidence, 0.15% to 0.9%) but serious complication of knee arthroplasty. Haematogenous PJI of the knee (KhPJI) which accounts for 10% of cases, has been less studied than PJI due to other mechanisms. The primary objective of this study in patients with KhPJI of the knee was to determine the 2-year infection eradication failure rate after either exchange arthroplasty or arthrotomy/synovectomy/irrigation (ASI), combined with prolonged peri-operative antibiotic therapy, at a referral centre for complex osteo-articular infections.

HYPOTHESIS

ASI within 2 weeks after symptom onset and one-stage exchange arthroplasty produce similar 2-year success rates in patients with KhPJI of the knee.

MATERIAL AND METHODS

A prospective observational cohort study was performed in patients managed for PJI of the knee between 2003 and 2015. The primary outcome measure was the occurrence of a septic event or of KhPJI -related death during a minimum follow-up of 2 years.

RESULTS

Of 265 patients with PJI after total knee arthroplasty, 58 (22.1%) had KhPJI with onset more than 3 months after the last arthroplasty procedure and were included in the study. Among them, one-third had immune deficiencies. The most common causative organisms were streptococci (n=25, 43%) and Staphylococcusaureus (n=20, 34%). The primary focus of infection was identified in only 64% of patients and was most often cutaneous (n=19, 33%) or dental (n=11, 19%). A septic event or KhPJI-related death occurred in 5/34 (15%) patients after one-stage exchange arthroplasty and 6/19 (32%) patients after ASI within 15 days after symptom onset (p=0.03). Patient characteristics, type of prosthesis, and causative organism were not significantly associated with failure to eradicate the infection.

CONCLUSION

ASI carried a high failure rate despite being performed within 15 days after symptom onset. One-stage exchange arthroplasty seems to be the best surgical option, particularly as the exact time of symptom onset may be difficult to determine. Identifying and eradicating the primary focus of infection is crucial.

LEVEL OF EVIDENCE

II, low-powered prospective cohort study.

Elution kinetics, antimicrobial efficacy, and degradation and microvasculature of a new gentamicin-loaded collagen fleece

Management of bone and soft tissue infections generally includes surgical procedures as well as attendant treatment and prevention with gentamicin-loaded fleeces. Conventional gentamicin-containing collagen fleeces currently in use are strongly acidic and exhibit limited biocompatibility thereby adversely affecting wound healing. To improve the antibiotic delivery system, a new phosphate-buffered, gentamicin-loaded fleece with pH-neutral properties has been developed (Jason G). This study aimed at comparing the elution kinetics of gentamicin release and the antimicrobial efficacy of conventional fleeces with the newly developed fleece in vitro. In addition, degradation and microvasculature of implanted fleeces were examined in a rat model and assessed using histology, as well as detection of ED-1 and PECAM-expression using immunohistochemistry. We show that the phosphate-buffered fleeces have reduced release (p < 0.05) of the integrated gentamicin. However, all of the fleeces tested had a significant antimicrobial effect on the growth of Staphylococcus aureus, Escherichia coli, and Pseudomonas aeruginosa strains (p < 0.01). Among the fleeces tested, the new Jason G fleece had the weakest but nevertheless sufficient antimicrobial effectiveness. Evaluation of the antibiotic effect in the prevention of an infection showed no differences between the applied fleeces. Following surgical implantation of fleece in the backs of Wistar rats we observed, on day 5 after implantation, an increase in cell infiltration and microvascularization with the phosphate-buffered fleece as compared with conventional fleeces, which show necrotic cells on their surface. Unlike the acidic fleeces, on day 15 after implantation the pH-neutral fleece was resorbed widely. Here, we show that the new, pH-neutral, gentamicin-containing fleece Jason G exhibits good overall antimicrobial effectiveness against both gram-positive and gram-negative bacteria in vitro with improved degradation properties and microvasculature formation in vivo.

Influência da ciprofloxacina na consolidação óssea de fraturas de fêmur em ratos

OBJETIVO: Apresentar um estudo experimental sobre o efeito da ciprofloxacina na resistência do calo ósseo de fraturas padronizadas de fêmures de ratos. MÉTODOS: Os ratos foram separados em dois grupos de oito animais: o grupo estudo (cipro) e o grupo controle. Os animais foram submetidos à fixação dos fêmures esquerdos com fio metálico intramedular e à confecção de fraturas padronizadas no mesmo osso. O grupo estudo recebeu ciprofloxacina e o grupo controle soro fisiológico durante seis semanas. Após este período, realizou-se estudo radiográfico controle e ensaio biomecânico de três pontos para obtenção da força de flexão mensurada em Newtons. RESULTADOS: As radiografias e a análise macroscópica demonstraram consolidação óssea em todas as fraturas. Foram comparados os resultados encontrados no estudo biomecânico entre os dois grupos, sendo que o grupo cipro apresentou resistência à força de flexão média 71,11 e o grupo controle, força de flexão média 74,78, não apresentando significância estatística (p = 0,601, test t). CONCLUSÃO: Não houve diferença estatística significante na resistência do calo ósseo de fraturas padronizadas de fêmur de ratos após o uso de ciprofloxacina em relação ao grupo controle.

Principles of systemic antimicrobial therapy in foreign material associated infection in bone tissue, with special focus on periprosthetic infection

Foreign material associated infection in bone tissue is mostly characterized by the features of sessile pathogens acting from the foreign material surface. These bacteria protected by biofilm attached to the surface are highly resistant for antimicrobial agents and host's own defense as well. Therapy is based on surgical revision, with removal of the foreign material and supplementary antimicrobial therapy. Empirical antimicrobial therapy cannot be recommended unless life threatening septicemia occurs. Infected bone tissue is lower compartment with respect to antimicrobial chemotherapy. Therefore, antibiotics must be administered in high dosage for an extended period of time. It is almost impossible to eradicate these pathogens by antibiotics alone even though the clinical symptoms may be influenced. The options of antimicrobial therapy are: 1. Antibiotics alone: Only suppression of clinical symptoms. 2. Amputation or resection arthroplasty in combination with antibiotics: The results are fair but poor in function. 3. Surgical revision with retention of the foreign material and long-term antibiotic therapy including rifampicin: This procedure is possible in early, not yet established foreign material infections. 4. Treatment of the periprosthetic infection: Surgical revision with exchange of the prosthesis combined with systemic (and optional local) therapy, regardless whether the revision is performed in 1 - or multiple-stages. Treatment of these infections should be carried out in specialized centers in cooperation with an experienced infectious disease specialist. Since most available data are empirical, further prospective studies are needed for evaluation of these therapeutic concepts.

Conservative medical therapy of prosthetic joint infections: retrospective analysis of an 8-year experience

Successful treatment of prosthetic joint infections often requires multiple surgical interventions and prolonged antimicrobial therapy. However, in certain situations, a surgical approach may not be in the best interest of the patient. A conservative approach was used to treat 34 patients with prosthetic joint infection between 1995 and 2003. Diagnosis of infection was based on clinical-microbiological evidence, confirmed by (99)Tc-labelled leukocyte scintigraphy, and involved 12 Staphylococcus aureus infections, nine Staphylococcus epidermidis infections, two Enterococcus faecalis infections, two mixed infections (S. aureus plus Pseudomonas aeruginosa; S. epidermidis plus E. faecalis), with the infecting pathogen being unidentified for nine patients. Most infections were treated initially with intravenous or intramuscular teicoplanin +/- ciprofloxacin or rifampicin, followed by oral ciprofloxacin or minocycline plus rifampicin. The mean duration of antimicrobial therapy was 41.2 weeks. Overall, only three patients did not respond to therapy, and infection was controlled in the remaining 31 patients. Among these, no relapse was observed in 17 patients during follow-up for 9-57 months; improvement with early (within 6 months of antibiotic discontinuation) or late relapse was observed in seven and three patients, respectively; two patients improved clinically, but continued to receive antibiotic therapy; and two patients whose condition improved initially were lost after a 6-month follow-up following discontinuation of antibiotics. No patient complained of side effects requiring discontinuation of antibiotic therapy. The study confirmed that suppression of infection, with salvage of the infected device in an acceptably functional state, can be achieved in selected cases.