Adjunctive use of rifampin for the treatment of Staphylococcus aureus infections: a systematic review of the literature

Local Delivery of Exosomes and Antibiotics in Hydroxyapatite-Based Nanocement for Osteomyelitis Management

The management of bone and joint infections is a formidable challenge in orthopedics and poses a global health concern. While clinical management emphasizes infection prevention and complete eradication, an effective strategy for stabilizing skeletal tissue with adequate soft tissue coverage remains limited. In this study, we have employed a novel approach of using the local delivery of exosomes and antibiotics (rifampicin) using a hydroxyapatite-based nanocement carrier to manage the residual space created during debridement effectively. Additionally, we synthesized a periosteum-guiding antioxidant herbal membrane to leverage the inherent periosteum regeneration capability of the bone, facilitating bone callus repair and natural healing. The synthesized scaffolds were biocompatible and demonstrated potent antibacterial activity in vitro. When evaluated in vivo in the Staphylococcus aureus-induced rat tibial osteomyelitis model, the released drugs successfully cleared the residual bacteria and the released exosome promoted bone healing, resulting in 3-fold increase in bone volume as analyzed via micro-CT analysis. Immunofluorescence staining of periosteum-specific markers also indicated the complete formation of periosteal layers, thus highlighting the complete bone repair.

Effect of N-acetyl cysteine, rifampicin, and ozone on biofilm formation in pan-resistant Klebsiella pneumoniae: an experimental study

BACKGROUND

To the best of our knowledge, this is the first study to evaluate the effectiveness of specific concentrations of antibiofilm agents, such as N-acetyl cysteine (NAC), rifampicin, and ozone, for the treatment of pan-resistant Klebsiella pneumoniae (PRKp).

OBJECTIVES

We evaluated the effectiveness of antibiofilm agents, such as NAC, rifampicin, and ozone, on biofilm formation in PRKp at 2, 6, 24, and 72 h.

DESIGN AND SETTING

This single-center experimental study was conducted on June 15, 2017, and July 15, 2018, at Istanbul Faculty of Medicine, Istanbul University, Turkey.

METHODS

Biofilm formation and the efficacy of these agents on the biofilm layer were demonstrated using colony counting and laser-screened confocal microscopy.

RESULTS

NAC at a final concentration of 2 μg/mL was administered to bacteria that formed biofilms (24 h), and no significant decrease was detected in the bacterial counts of all isolates (all P > 0.05). Rifampicin with a final concentration of 0.1 μg/mL was administered to bacteria that formed biofilm (24 h), and no significant decrease was detected in bacterial count (all P > 0.05). Notably, ozonated water of even 4.78 mg/L concentration for 72 h decreased the bacterial count by ≥ 2 log10.

CONCLUSION

Different approaches are needed for treating PRKp isolates. We demonstrate that PRKp isolates can be successfully treated with higher concentrations of ozone.

From the Oral Cavity to the Spine: Prevalence of Oral Cavity Infections in Patients with Pyogenic Spinal Infection

Background incidence of pyogenic spinal infections has increased in recent years. In addition to treating the spinal infection, optimal care also includes identifying the source of the pyogenic spinal infection and the presence of other infections. The aim of this study is to elucidate the prevalence of oral cavity infection (OCI) within this patient cohort. Methods As part of a prospective study conducted from 2016 to 2021, the number of patients with dental infections was investigated by means of an orthopantomogram (OPG) and subsequent dental examination. Results The presence of an oral infection was investigated in 55 (47%) of 118 patients by an OPG, 29 (53%) of whom had a corresponding abnormality of the oral cavity. In addition to the spinal infection, patients with an oral cavity infection revealed an increased incidence of endocarditis, sepsis and brain abscess. A spinal epidural abscess, a multilevel affection of the infection, and an elevated CRP value were also found in patients with a co-existing oral cavity infection. Back pain assessed at admission and 3 months after surgery was also more pronounced in patients with an oral cavity infection. Neurological deficits were often present in patients with spinal and oral cavity infection. Conclusions The presence of an oral cavity infection has proven to be one of the important factors in the detection of the source of the pyogenic spinal infection. In addition, a pronounced spinal affection and frequent co-infections were seen in patients with an oral cavity infection.

Rifampin Based Therapy for Patients With Staphylococcus aureus Native Vertebral Osteomyelitis: A Systematic Review and Meta-analysis

BACKGROUND

Native vertebral osteomyelitis (NVO) caused by Staphylococcus aureus is associated with high risk of treatment failure and increased morbidity. The role of rifampin-based therapy for the treatment of this condition is controversial. The goal of this systematic review and meta-analysis is to explore the efficacy and safety of rifampin-based therapy for the treatment of S. aureus NVO.

METHODS

We searched Cochrane, Embase, Medline, Scopus, and Web of Science databases for studies published up to May 2023, focusing on adults with NVO treated with or without rifampin-containing regimens. A random-effects model meta-analysis estimated relative risks and risk difference with 95% confidence intervals (CI).

RESULTS

Thirteen studies (2 randomized controlled trials and 11 comparative cohort studies), comprising 244 patients with S. aureus NVO who received rifampin and 435 who did not, were analyzed. Meta-analysis showed that rifampin-based regimens were associated with lower risk of clinical failure (risk difference, -14%; 95% CI, -19% to -8%; P < .001; I2 = 0%; relative risk, 0.58; 95% CI, .37-.92, P = .02, I2 = 21%). Only 1 study reported on adverse events. All studies had a high or uncertain risk of bias, and the certainty of evidence was rated as very low.

CONCLUSIONS

Adjunctive rifampin therapy might be associated with lower risk of S. aureus NVO treatment failure; however, the low certainty of evidence precludes drawing definitive conclusions that would alter clinical practice. A randomized trial is necessary to corroborate these findings.

Biofilm Producing Methicillin-Resistant Staphylococcus aureus (MRSA) Infections in Humans: Clinical Implications and Management

Since its initial description in the 1960s, methicillin-resistant Staphylococcus aureus (MRSA) has developed multiple mechanisms for antimicrobial resistance and evading the immune system, including biofilm production. MRSA is now a widespread pathogen, causing a spectrum of infections ranging from superficial skin issues to severe conditions like osteoarticular infections and endocarditis, leading to high morbidity and mortality. Biofilm production is a key aspect of MRSA's ability to invade, spread, and resist antimicrobial treatments. Environmental factors, such as suboptimal antibiotics, pH, temperature, and tissue oxygen levels, enhance biofilm formation. Biofilms are intricate bacterial structures with dense organisms embedded in polysaccharides, promoting their resilience. The process involves stages of attachment, expansion, maturation, and eventually disassembly or dispersion. MRSA's biofilm formation has a complex molecular foundation, involving genes like icaADBC, fnbA, fnbB, clfA, clfB, atl, agr, sarA, sarZ, sigB, sarX, psm, icaR, and srtA. Recognizing pivotal genes for biofilm formation has led to potential therapeutic strategies targeting elemental and enzymatic properties to combat MRSA biofilms. This review provides a practical approach for healthcare practitioners, addressing biofilm pathogenesis, disease spectrum, and management guidelines, including advances in treatment. Effective management involves appropriate antimicrobial therapy, surgical interventions, foreign body removal, and robust infection control practices to curtail spread within healthcare environments.

Efficacy of EDTA-NS irrigation in eradicating Staphylococcus aureus biofilm-associated infection

Aims

To investigate the efficacy of ethylenediaminetetraacetic acid-normal saline (EDTA-NS) in dispersing biofilms and reducing bacterial infections.

Methods

EDTA-NS solutions were irrigated at different durations (1, 5, 10, and 30 minutes) and concentrations (1, 2, 5, 10, and 50 mM) to disrupt Staphylococcus aureus biofilms on Matrigel-coated glass and two materials widely used in orthopaedic implants (Ti-6Al-4V and highly cross-linked polyethylene (HXLPE)). To assess the efficacy of biofilm dispersion, crystal violet staining biofilm assay and colony counting after sonification and culturing were performed. The results were further confirmed and visualized by confocal laser scanning microscopy (CLSM) and scanning electron microscopy (SEM). We then investigated the efficacies of EDTA-NS irrigation in vivo in rat and pig models of biofilm-associated infection.

Results

When 10 mM or higher EDTA-NS concentrations were used for ten minutes, over 99% of S. aureus biofilm formed on all three types of materials was eradicated in terms of absorbance measured at 595 nm and colony-forming units (CFUs) after culturing. Consistently, SEM and CSLM scanning demonstrated that less adherence of S. aureus could be observed on all three types of materials after 10 mM EDTA-NS irrigation for ten minutes. In the rat model, compared with NS irrigation combined with rifampin (Ti-6Al-4V wire-implanted rats: 60% bacteria survived; HXLPE particle-implanted rats: 63.3% bacteria survived), EDTA-NS irrigation combined with rifampin produced the highest removal rate (Ti-6Al-4V wire-implanted rats: 3.33% bacteria survived; HXLPE particle-implanted rats: 6.67% bacteria survived). In the pig model, compared with NS irrigation combined with rifampin (Ti-6Al-4V plates: 75% bacteria survived; HXLPE bearings: 87.5% bacteria survived), we observed a similar level of biofilm disruption on Ti-6Al-4V plates (25% bacteria survived) and HXLPE bearings (37.5% bacteria survived) after EDTA-NS irrigation combined with rifampin. The in vivo study revealed that the biomass of S. aureus biofilm was significantly reduced when treated with rifampin following irrigation and debridement, as indicated by both the biofilm bacterial burden and crystal violet staining. EDTA-NS irrigation (10 mM/10 min) combined with rifampin effectively removes S. aureus biofilm-associated infections both in vitro and in vivo.

Conclusion

EDTA-NS irrigation with or without antibiotics is effective in eradicating S. aureus biofilm-associated infection both ex and in vivo.

Efficacy of single antibiotic therapy versus antibiotic combination in implant-free staphylococcal post-surgical spinal infections: a retrospective observational study

BACKGROUND

Post-surgical spinal infections (pSSIs) are a serious complication of spinal surgeries, with Staphylococcus spp. being one of the most prominent bacteria identified. Optimal antimicrobial therapy for staphylococcal spinal infections without spinal implants is not well documented.

METHODS

This single center retrospective 7-year observational study described and compared the outcome (treatment failure or mortality rate one year after diagnosis) of 20 patients with staphylococcal-implant-free pSSI treated with single or combination antibiotics.

RESULTS

Median duration of treatment was 40 days (IQR 38-42), with 6 days (IQR 5-7) on intravenous antibiotics and 34 days (IQR 30-36) on oral therapy. Four patients (20%) underwent new surgical debridement, all due to surgical failure, and 1 patient died within the first year without significant differences between both treatment group.

CONCLUSION

This study raises the possibility of single antibiotic therapy for patients with implant-free post-surgical spinal infections due to Staphylococcus spp.

Clinical outcomes of rifampicin combination therapy in implant-associated infections due to staphylococci and streptococci: A systematic review and meta-analysis

OBJECTIVES

Adjunctive rifampicin for implant-associated infections is controversial. This study investigated the clinical outcomes of rifampicin combination therapy compared with monotherapy in treating prosthetic joint infection (PJI) or prosthetic valve endocarditis (PVE) due to staphylococci and streptococci.

METHODS

A systematic search was performed from inception to 13 June 2022 in Embase, MEDLINE, Cochrane and Web of Science to investigate the clinical outcomes of rifampicin combination therapy compared with monotherapy in treating staphylococcal and streptococcal PJI or PVE. Randomised controlled trials (RCTs) and observational studies were included in the systematic review and meta-analysis.

RESULTS

Fourteen studies were included. A moderate quality of evidence was found in favour of rifampicin in patients with staphylococcal PJI who underwent a debridement, antibiotics and implant retention (DAIR) procedure [odds ratio = 2.49, 95% confidence interval (CI) 1.93-3.23]. Including the two RCTs only, adding rifampicin to the antibiotic regimen after DAIR was also in favour of rifampicin, but this was not statistically significant (risk ratio = 1.27, 95% CI 0.79-2.04; n = 126). Pooling data for patients with staphylococcal PJI who underwent a two-stage procedure showed that adding rifampicin was not associated with therapeutic success. Limited evidence was found for the use of rifampicin for PVE caused by staphylococci.

CONCLUSIONS

Adding rifampicin in the treatment of staphylococcal PJI treated by DAIR clearly increased the likelihood for therapeutic success. The clinical benefit of adjunctive rifampicin in the treatment of other staphylococci and streptococci implant-associated infections is still unclear.

Liposome-loaded polymeric microneedles for enhanced skin deposition of rifampicin

Methicillin-resistant Staphylococcus aureus (MRSA) is a prevailing bacterial pathogen linked to superficial skin and soft tissue infections (SSTIs). Rifampicin (RIF), a potent antibiotic against systemic and localised staphylococcal infections, faces limitations due to its low solubility. This constraint hampers its therapeutic potential for MRSA-induced SSTIs. To address this, an advanced liposomal system was designed for efficient dermal RIF delivery. Rifampicin-loaded liposomes (LipoRIF) were embedded within polymeric dissolving microneedles (DMNs) to enable targeted intradermal drug delivery. A robust Design of Experiment (DoE) methodology guided the systematic preparation and optimisation of LipoRIF formulations. The optimal LipoRIF formulation integrated within polymeric DMNs. These LipoRIF-DMNs exhibited favourable mechanical properties and effective skin insertion characteristics. Notably, in vitro assays on skin deposition unveiled a transformative result - the DMN platform significantly enhanced LipoRIF deposition within the skin, surpassing LipoRIF dispersion alone. Moreover, LipoRIF-DMNs displayed minimal cytotoxicity toward cells. Encouragingly, rigorous in vitro antimicrobial evaluations demonstrated LipoRIF-DMNs' capacity to inhibit MRSA growth compared to the control group. LipoRIF-DMNs propose a potentially enhanced, minimally invasive approach to effectively manage SSTIs and superficial skin ailments stemming from MRSA infections.

Effectiveness of adjunctive rifampicin for treatment of Staphylococcus aureus bacteraemia: a systematic review and meta-analysis of randomized controlled trials

OBJECTIVES

To assess whether the addition of rifampicin to conventional treatment of Staphylococcus aureus bacteraemia (SAB) reduces bacteriological or clinical failure or death.

DATA SOURCES

PubMed, Embase and Cochrane CENTRAL databases were searched from inception to 31 December 2022. Reference lists and PubMed citations of eligible studies were checked.

REVIEW METHODS

Two study authors independently identified randomized controlled trials (RCTs) involving adult participants with SAB, in which an intervention group received adjunctive rifampicin and the control group received usual care with or without a placebo. Dichotomous data (bacteriological and clinical failure and deaths) were analysed and pooled across studies using risk ratio (RR) with 95% confidence intervals (CI) using a Mantel-Haenszel random-effect model. The key variable of interest being whether rifampicin was used.

RESULTS

Six RCTs including 894 participants-of which 758 (85%) were from one trial-met the inclusion criteria. The addition of rifampicin to conventional treatment of SAB significantly reduced bacteriological failure by 59% (RR 0.41, 95% CI 0.21-0.81, I2 = 0%, number need to treat 27). However, it did not reduce clinical failure (RR 0.70, 95% CI 0.47-1.03, I2 = 0%) or deaths (RR 0.96, 95% CI 0.70-1.32, I2 = 0%). Further, it did not reduce the duration of bacteraemia, or the length of hospital stay. Adjunctive rifampicin reduced SAB recurrences (1% versus 4%, P = 0.01). Emergence of rifampicin resistance during treatment was uncommon (<1%).

CONCLUSION

Although adjunctive rifampicin reduced the risk of bacteriological failure and recurrences, we found no mortality benefit to support its use in SAB.

Systemic Antimicrobial Treatment of Chronic Osteomyelitis in Adults: A Narrative Review

Chronic osteomyelitis in adults is a complex condition that requires prolonged and intensive antimicrobial therapy, but evidence on optimal selection and duration of antibiotics is limited. A review of PubMed and Ovid Embase databases was conducted to identify systematic reviews, meta-analyses, retrospective and randomised controlled trials (RCTs) on antibiotic treatment outcomes in adults with chronic osteomyelitis. Three main areas of interest were investigated: short-term versus long-term antibiotic therapy, oral versus parenteral antibiotic therapy, and combination antibiotic therapy with rifampicin versus without rifampicin. A total of 36 articles were identified and findings were synthesised using a narrative review approach. The available literature suffers from limitations, including a lack of high-quality studies, inconsistent definitions, and varying inclusion/exclusion criteria among studies. Most studies are open-labelled and lack blinding. Limited high-quality evidence exists that oral therapy is non-inferior to parenteral therapy and that shorter antibiotic duration might be appropriate in low-risk patients. Studies on the impact of rifampicin are inconclusive. Further well-designed studies are needed to provide more robust evidence in these areas.

Heartbreaking Decisions: The Dogma and Uncertainties of Antimicrobial Therapy in Infective Endocarditis

Infective endocarditis (IE) is a rare but increasingly prevalent disease with high morbidity and mortality, requiring antimicrobials and at times surgical intervention. Through the decades of healthcare professionals' experience with managing IE, certain dogmas and uncertainties have arisen around its pharmacotherapy. The introduction of new antimicrobials and novel combinations are exciting developments but also further complicate IE treatment choices. In this review, we provide and evaluate the relevant evidence focused around contemporary debates in IE treatment pharmacotherapy, including beta-lactam choice in MSSA IE, combination therapies (aminoglycosides, ceftaroline), the use of oral antimicrobials, the role of rifamycins, and long-acting lipoglycopeptides.

Pathogenic Role and Antibiotic Resistance of Methicillin-Resistant Staphylococcus aureus (MRSA) Strains Causing Severe Community-Acquired Pneumonia in Vietnamese Children

In recent years, the pathogenic role and antibiotic resistance of methicillin-resistant Staphylococcus aureus (MRSA) strains causing severe community-acquired pneumonia (CAP) have received increasing attention in clinical practice. The aim of this study was to determine the rate of isolates of MRSA strains causing severe CAP in children and to assess their level of antibiotic resistance. The study design was cross-sectional. Children with severe CAP were sampled by nasopharyngeal aspiration for the culture, isolation, and identification of MRSA. Antimicrobial susceptibility testing was performed using the gradient diffusion method to determine the minimum inhibitory concentration (MIC) of antibiotics. Results: MRSA was identified as the second leading cause of severe CAP in Vietnamese children. The rate of isolates of S. aureus was 41/239 (17.5%), of which most were MRSA, at 32/41 (78.0%). MRSA strains were completely non-susceptible to penicillin (100%), more resistant to clindamycin and erythromycin, less sensitive to ciprofloxacin and levofloxacin, and fully susceptible to vancomycin and linezolid, with a 32-fold decreased MIC90 for vancomycin (0.5 mg/L) and a 2-fold decreased MIC90 for linezolid (4 mg/L). Therefore, vancomycin and linezolid may be appropriate options for severe CAP identified by MRSA.

The Use of Rifampin in Total Joint Arthroplasty: A Systematic Review and Meta-Analysis of Comparative Studies

BACKGROUND

Periprosthetic joint infection (PJI) is a devastating complication of total joint arthroplasty (TJA). Rifampin is an antibiotic with the ability to penetrate bacterial biofilms, and thus has been considered as a potentially important adjunct in the prevention and treatment of PJI. The aim of this systematic review is to evaluate and summarize the use of rifampin in TJA, particularly in the context of PJI.

METHODS

A literature search of all relevant electronic databases was performed. All comparative studies assessing the use of rifampin in the context of TJA were included. Descriptive data are reported, and a meta-analysis was performed using all studies which compared the addition of rifampin to standard care in treating PJI.

RESULTS

A total of 33 studies met inclusion criteria. A meta-analysis of 22 studies comparing the addition of rifampin to standard care for treating PJI found a significant reduction in failure rates (26.0% vs 35.9%; odds ratio 0.61, 95% confidence interval 0.43-0.86). The protective effect of rifampin was maintained in studies which included exchange arthroplasty as a treatment strategy, but not in studies only using an implant retention strategy. Among studies reporting adverse events of rifampin, there was a 20.5% adverse event rate.

CONCLUSION

Overall, rifampin appears to confer a protective effect against treatment failure following PJI. This treatment effect is particularly pronounced in the context of exchange arthroplasty. Further high-level evidence is needed to clarify the exact indications and doses of rifampin which can most effectively act as an adjunct in the treatment of PJI.

LEVEL OF EVIDENCE

Level III, Systematic Review and Meta-Analysis of Level I-III Studies.

Oral versus standard antimicrobial treatment for pyogenic native vertebral osteomyelitis: a single center, retrospective, propensity score balanced analysis

Background

Interest toward shorter antimicrobial regimens and oral treatment for osteoarticular infections is growing. The aim of this study is to assess whether there is an association between the administration of an entirely oral antibiotic therapy (OT) and the clinical outcome of native vertebral osteomyelitis (NVOs).

Methods

Single center, retrospective, observational study on consecutive patients with pyogenic NVOs over a 10-year period (2008-2018). Multivariate logistic regression analysis was carried out to identify risk factors for clinical failure, both in the whole population and in subgroups. The impact of OT versus standard treatment (intravenous induction followed by oral treatment whenever possible) was assessed in patients with a non-multidrug resistant microorganism (MDRO) etiology and the impact of a rifampin-containing regimen was assessed in patients affected by NVOs caused by staphylococci or of unknown etiology.

Results

Study population included 249 patients, 33 (13.3%) experienced clinical failure; OT group consisted of 54 patients (21.7%). Multivariate regression analysis of the whole population selected Charlson Comorbidity Index (aOR 1.291, 95% CI 1.114-1.497, p = 0.001) and MDRO etiology (aOR 3.301, 95% CI 1.368-7.964, p = 0.008) as independent factors for clinical failure. Among patients affected by a non-MDRO NVO, OT was not associated with an increased risk of clinical failure (aOR 0.487, 95% CI 0.133-1.782, p value = 0.271), even after adjustment for the propensity score of receiving OT. In the subgroup of patients with staphylococcal or unknown etiology NVO rifampin was independently associated with favorable outcome (aOR 0.315, 95% CI 0.105-0.949, p value = 0.040)

Conclusions

An entirely oral, highly bioavailable treatment, including rifampin, may be as effective as parenteral treatment in selected patients with NVOs.

Current clinical practice in antibiotic treatment of Staphylococcus aureus bacteraemia: results from a survey in five European countries

OBJECTIVES

To determine clinical practice variation and identify knowledge gaps in antibiotic treatment of Staphylococcus aureus bacteraemia (SAB).

METHODS

A web-based survey with questions addressing antibiotic treatment of SAB was distributed through the ESGAP network among infectious disease specialists, clinical microbiologists and internists in Croatia, France, Greece, the Netherlands and the UK between July 2021 and November 2021.

RESULTS

A total number of 1687 respondents opened the survey link, of whom 677 (40%) answered at least one question. For MSSA and MRSA bacteraemia, 98% and 94% preferred initial monotherapy, respectively. In patients with SAB and non-removable infected prosthetic material, between 80% and 90% would use rifampicin as part of the treatment. For bone and joint infections, 65%-77% of respondents would consider oral step-down therapy, but for endovascular infections only 12%-32% would. Respondents recommended widely varying treatment durations for SAB with different foci of infection. Overall, 48% stated they used 18F-fluorodeoxyglucose positron emission tomography/CT (18F-FDG-PET/CT) to guide antibiotic treatment duration. Persistent bacteraemia was the only risk factor for complicated SAB that would prompt a majority to extend treatment from 2 to 4-6 weeks.

CONCLUSIONS

This survey in five European countries shows considerable clinical practice variation between and within countries in the antibiotic management of SAB, in particular regarding oral step-down therapy, choice of oral antibiotic agents, treatment duration and use of 18F-FDG-PET/CT. Physicians use varying criteria for treatment decisions, as evidence from clinical trials is often lacking. These areas of practice variation could be used to prioritize future studies for further improvement of SAB care.

Adjunctive rifampin therapy for native valve Staphylococcus aureus endocarditis in a neonate: A case report and literature review

Infective endocarditis in neonates can be fatal. Adjunctive rifampin therapy might be effective as salvage therapy in critically ill patients with Staphylococcus aureus native valve endocarditis (NVE). We present a case of a full-term neonate with NVE who had a favorable clinical outcome after adding rifampin to standard therapy.

Streptomyces sp.-A Treasure Trove of Weapons to Combat Methicillin-Resistant Staphylococcus aureus Biofilm Associated with Biomedical Devices

Biofilms formed by methicillin-resistant S. aureus (MRSA) are among the most frequent causes of biomedical device-related infection, which are difficult to treat and are often persistent and recurrent. Thus, new and effective antibiofilm agents are urgently needed. In this article, we review the most relevant literature of the recent years reporting on promising anti-MRSA biofilm agents derived from the genus Streptomyces bacteria, and discuss the potential contribution of these newly reported antibiofilm compounds to the current strategies in preventing biofilm formation and eradicating pre-existing biofilms of the clinically important pathogen MRSA. Many efforts are evidenced to address biofilm-related infections, and some novel strategies have been developed and demonstrated encouraging results in preclinical studies. Nevertheless, more in vivo studies with appropriate biofilm models and well-designed multicenter clinical trials are needed to assess the prospects of these strategies.

A Strong Synergy Between the Thiopeptide Bacteriocin Micrococcin P1 and Rifampicin Against MRSA in a Murine Skin Infection Model

Antibiotic-resistant bacterial pathogens have become a serious threat worldwide. One of these pathogens is methicillin-resistant Staphylococcus aureus (MRSA), a major cause of skin and soft tissue infections. In this study we identified a strain of Staphylococcus equorum producing a substance with high antimicrobial activity against many Gram-positive bacteria, including MRSA. By mass spectrometry and whole genome sequencing the antimicrobial substance was identified as the thiopeptide bacteriocin micrococcin P1 (MP1). Based on its properties we developed a one-step purification protocol resulting in high yield (15 mg/L) and high purity (98%) of MP1. For shorter incubation times (5-7 h) MP1 was very potent against MRSA but the inhibitory effect was overshadowed by resistance development during longer incubation time (24h or more). To overcome this problem a synergy study was performed with a number of commercially available antibiotics. Among the antibiotics tested, the combination of MP1 and rifampicin gave the best synergistic effect, with MIC values 25 and 60 times lower than for the individual drugs, respectively. To assess the therapeutic potential of the MP1-rifampicin combination, we used a murine skin infection model based on the use of the multidrug-resistant luciferase-tagged MRSA strain Xen31. As expected, neither of the single antimicrobials (MP1 or rifampicin) could eradicate Xen31 from the wounds. By contrary, the MP1-rifampicin combination was efficient not only to eradicate but also to prevent the recurrence of Xen31 infection. Furthermore, compared to fucidin cream, which is commonly used in skin infection treatments, MP1-rifampicin combination was superior in terms of preventing resistance development. Our results show that combining MP1, and probably other thiopeptides, with antibiotics can be a promising strategy to treat SSTIs caused by MRSA and likely many other Gram-positive bacteria.

Dual therapeutic targeting of intra-articular inflammation and intracellular bacteria enhances chondroprotection in septic arthritis

Bacterial infections involving joints and vital organs represent a challenging clinical problem because of the two concurrent therapeutic goals of bacterial eradication and tissue preservation. In the case of septic arthritis, permanent destruction of articular cartilage by intense host inflammation is commonly seen even after successful treatment of bacterial infection. Here, we provide scientific evidence of a novel treatment modality that can protect articular cartilage and enhanced eradication of causative bacteria in septic arthritis. Locally delivered cell-penetrating antibiotics such as rifampicin effectively eradicate intracellular reservoirs of methicillin-resistant Staphylococcus aureus within joint cells. Furthermore, mitigation of intra-articular inflammation by targeting the NLRP3 (nucleotide-binding oligomerization domain-, leucine-rich repeat- and pyrin domain-containing 3) inflammasome protects articular cartilage from damage in a murine model of knee septic arthritis. Together, concurrent mitigation of intra-articular inflammation and local adjuvant targeting of intracellular bacteria represents a promising new therapeutic strategy for septic arthritis.

Controversy about the Role of Rifampin in Biofilm Infections: Is It Justified?

Rifampin is a potent antibiotic against staphylococcal implant-associated infections. In the absence of implants, current data suggest against the use of rifampin combinations. In the past decades, abundant preclinical and clinical evidence has accumulated supporting its role in biofilm-related infections.In the present article, experimental data from animal models of foreign-body infections and clinical trials are reviewed. The risk for emergence of rifampin resistance and multiple drug interactions are emphasized. A recent randomized controlled trial (RCT) showing no beneficial effect of rifampin in patients with acute staphylococcal periprosthetic joint infection treated with prosthesis retention is critically reviewed and data interpreted. Given the existing strong evidence demonstrating the benefit of rifampin, the conduction of an adequately powered RCT with appropriate definitions and interventions would probably not comply with ethical standards.

Therapeutic Strategies To Counteract Antibiotic Resistance in MRSA Biofilm-Associated Infections

Methicillin-resistant Staphylococcus aureus (MRSA) has emerged as one of the leading causes of persistent human infections. This pathogen is widespread and is able to colonize asymptomatically about a third of the population, causing moderate to severe infections. It is currently considered the most common cause of nosocomial infections and one of the main causes of death in hospitalized patients. Due to its high morbidity and mortality rate and its ability to resist most antibiotics on the market, it has been termed a "superbug". Its ability to form biofilms on biotic and abiotic surfaces seems to be the primarily means of MRSA antibiotic resistance and pervasiveness. Importantly, more than 80 % of bacterial infections are biofilm-mediated. Biofilm formation on indwelling catheters, prosthetic devices and implants is recognized as the cause of serious chronic infections in hospital environments. In this review we discuss the most relevant literature of the last five years concerning the development of synthetic small molecules able to inhibit biofilm formation or to eradicate or disperse pre-formed biofilms in the fight against MRSA diseases. The aim is to provide guidelines for the development of new anti-virulence strategies based on the knowledge so far acquired, and, to identify the main flaws of this research field, which have hindered the generation of new market-approved anti-MRSA drugs that are able to act against biofilm-associated infections.

Antibiofilm efficacy of focused high-energy extracorporeal shockwaves and antibiotics in vitro

Aims

Biofilm formation is one of the primary reasons for the difficulty in treating implant-related infections (IRIs). Focused high-energy extracorporeal shockwave therapy (fhESWT), which is a treatment modality for fracture nonunions, has been shown to have a direct antibacterial effect on planktonic bacteria. The goal of the present study was to investigate the effect of fhESWT on Staphylococcus aureus biofilms in vitro in the presence and absence of antibiotic agents.

Methods

S. aureus biofilms were grown on titanium discs (13 mm × 4 mm) in a bioreactor for 48 hours. Shockwaves were applied with either 250, 500, or 1,000 impulses onto the discs surrounded by either phosphate-buffered saline or antibiotic (rifampin alone or in combination with nafcillin). The number of viable bacteria was determined by quantitative culture after sonication. Representative samples were taken for scanning electron microscopy.

Results

The application of fhESWT led to a ten-fold reduction in bacterial counts on the metal discs for all impulse numbers compared to the control (p < 0.001). Increasing the number of impulses did not further reduce bacterial counts in the absence of antibiotics (all p > 0.289). Antibiotics alone reduced the number of bacteria on the discs; however, the combined application of the fhESWT and antibiotic administration further reduced the bacterial count compared to the antibiotic treatment only (p = 0.032).

Conclusion

The use of fhESWT significantly reduced the colony-forming unit (CFU) count of a S. aureus biofilm in our model independently, and in combination with antibiotics. Therefore, the supplementary application of fhESWT could be a helpful tool in the treatment of IFIs in certain cases, including infected nonunions.

Cite this article: Bone Joint Res 2021;10(1):77–84.

Staphylococcal Skin and Soft Tissue Infections

Staphylococcus aureus is the most common bacteria causing purulent skin and soft tissue infections. Many disease-causing S aureus strains are methicillin resistant; thus, empiric therapy should be given to cover methicillin-resistant S aureus. Bacterial wound cultures are important for characterizing local susceptibility patterns. Definitive antibiotic therapy is warranted, although there are no compelling data demonstrating superiority of any one antibiotic over another. Antibiotic choice is predicated by the infection severity, local susceptibility patterns, and drug-related safety, tolerability, and cost. Response to therapy is expected within the first days; 5 to 7 days of therapy is typically adequate to achieve cure.

Rifampin combination therapy in staphylococcal prosthetic joint infections: a randomized controlled trial

Background

The evidence supporting rifampin combination therapy in prosthetic joint infections (PJI) is limited due to the lack of controlled studies. The aim of this study is to evaluate the effect of adding rifampin to conventional antimicrobial therapy in early staphylococcal PJIs treated with debridement and retention of the implant (DAIR).

Methods

In this multicenter randomized controlled trial, 99 patients with PJI after hip and knee arthroplasties were enrolled. They were randomly assigned to receive rifampin or not in addition to standard antimicrobial treatment with cloxacillin or vancomycin in case of methicillin resistance. The primary endpoint was no signs of infection after 2 years of follow-up.

Results

Forty-eight patients were included in the final analyses. There were no differences in patient characteristics or comorbidities between the two groups. There was no significant difference in remission rate between the rifampin combination group (17 of 23 (74%)) and the monotherapy group (18 of 25 (72%), relative risk 1.03, 95% confidence interval 0.73 to 1.45, p = 0.88).

Conclusion

This trial has not proven a statistically significant advantage by adding rifampin to standard antibiotic treatment in acute staphylococcal PJIs.

Trial registration

The Regional Ethics Committee and the Norwegian Medicines Agency approved the study (EudraCT 2005-005494-29), and the study was registered at ClinicalTrials.gov at Jan 18, 2007 (NCT00423982).

Rifabutin Use in Staphylococcus Biofilm Infections: A Case Series

This is a case series of 10 patients who had staphylococcal biofilm infections that were treated with adjuvant rifabutin therapy instead of rifampin therapy. In these cases, rifampin was contraindicated secondary to drug–drug interactions with the patients’ chronic medications. Rifabutin therapy was well tolerated with no side effects. As well, no patients had recurrence of their staphylococcal infections. This case series shows that rifabutin can be a beneficial adjuvant therapy in Staphylococcus biofilm infections when drug–drug interactions limit the use of rifampin.

The First Report on Pharmacokinetic/Pharmacodynamic Study of Trimethoprim/Sulfamethoxazole against Staphylococcus aureus with a Neutropenic Murine Thigh Infection Model

INTRODUCTION

With an increase in the incidence of Staphylococcus aureus infections in the healthcare settings and in the community, trimethoprim/sulfamethoxazole (TMP/SMX) has been suggested as a convenient treatment option. However, the appropriate dosage regimen of TMP/SMX is unclear.

OBJECTIVE

This study aimed to examine the pharmacokinetics/pharmacodynamics (PK/PD) of TMP/SMX against S. aureus using a neutropenic murine thigh infection model.

METHODS

Five S. aureus isolates with TMP/SMX (1:5 fixed ratio) minimum inhibitory concentrations (MICs) of 0.032-64 μg/mL were tested. The antimicrobial efficacy of TMP/SMX (1-689 mg/kg/day: dose shown as SMX dosage) was calculated as the change in bacterial density after 24 h of treatment. The plasma concentrations of TMP/SMX were detected using high-performance liquid chromatography.

RESULTS

After TMP/SMX single dose (130 mg/kg), the half-life, area under the blood concentration curve (AUC0-∞), and the protein binding ratio of SMX were 1.5 h, 718.2 μg h/mL, and 73.0 ± 8.3%, respectively. The free AUC/MIC and free %time (%T) above the MIC of SMX were better correlated with the in vivo antimicrobial activity than Cmax/MIC (free AUC/MIC, R2 = 0.69; free %T > MIC, R2 = 0.71; free Cmax/MIC, R2 = 0.53). The distributed doses (2-3 times per day) of TMP/SMX (130, 260, and 390 mg/kg/day) showed higher antimicrobial activity than the single dosage. However, TMP/SMX did not show its antimicrobial activity at <100% free %T > MIC.

CONCLUSIONS

The TMP/SMX treatment demonstrated that the free AUC/MIC of SMX was the better predictor of the PK/PD index of TMP/SMX.

In Full Flow: Left Ventricular Assist Device Infections in the Modern Era

With the rising prevalence of heart disease in the United States, there is increasing reliance on durable mechanical circulatory support (MCS) to treat patients with end-stage heart failure. Left ventricular assist devices (LVADs), the most common form of durable MCS, are implanted mechanical pumps that connect to an external power source through a transcutaneous driveline. First-generation LVADs were bulky, pulsatile pumps that were frequently complicated by infection. Second-generation LVADs have an improved design, though infection remains a common and serious complication due to the inherent nature of implanted MCS. Infections can affect any component of the LVAD, with driveline infections being the most common. LVAD infections carry significant morbidity and mortality for LVAD patients. Therefore, it is paramount for the multidisciplinary team of clinicians caring for these patients to be familiar with this complication. We review the epidemiology, prevention, diagnosis, treatment, and outcomes of LVAD infections.

Antibiotic treatment regimens for bone infection after debridement: a study of 902 cases

BACKGROUND

Our aim was to investigate the clinical efficacy and complications of antibiotic treatment regimens for patients with bone infection.

METHODS

We retrospectively analysed patients with bone infection admitted to our hospital between March 2013 and October 2018. After surgical debridement was performed, the patients were divided into three groups: IV group (intravenous antibiotics for 2 weeks); oral group (intravenous antibiotics for 2 weeks followed by oral antibiotics for 4 weeks); and rifampicin group (intravenous antibiotics for 2 weeks followed by oral antibiotics plus rifampicin for 4 weeks). The infection control rate and complications were compared among the three groups.

RESULTS

A total of 902 patients were enrolled. The infection sites included 509 tibias, 228 femurs, 32 humeri, 23 radii and ulnae, 40 calcanei, and 47 miscellaneous sites, as well as 23 multiple-site infections. After at least 6 months of follow-up, 148 (16.4%) patients had an infection recurrence. The recurrence rate of the IV group was 17.9%, which was not significantly higher than the recurrence rates of the oral group (10.1%) and rifampicin group (10.5%), P = 0.051. The incidence of abnormal alanine aminotransferase (ALT) levels in the IV group was 15.1%, which was lower than that in the oral group (18.0%) and rifampicin group (27.4%), P = 0.026. The rates of proteinuria in the three groups were 3.2, 4.5, and 9.3%, respectively, P = 0.020.

CONCLUSIONS

After debridement of bone infection, short-term antibiotic treatment regimens might offer similar rates of infection eradication while avoiding the risk of renal and hepatic damage associated with prolonged antibiotic use.

THE LEVEL OF CLINICAL RELEVANCE

Stage III.

Spinal Infections: An Update

Spinal infection poses a demanding diagnostic and treatment problem for which a multidisciplinary approach with spine surgeons, radiologists, and infectious disease specialists is required. Infections are usually caused by bacterial microorganisms, although fungal infections can also occur. The most common route for spinal infection is through hematogenous spread of the microorganism from a distant infected area. Most patients with spinal infections diagnosed in early stages can be successfully managed conservatively with antibiotics, bed rest, and spinal braces. In cases of gross or pending instability, progressive neurological deficits, failure of conservative treatment, spinal abscess formation, severe symptoms indicating sepsis, and failure of previous conservative treatment, surgical treatment is required. In either case, close monitoring of the patients with spinal infection with serial neurological examinations and imaging studies is necessary.

Adjunctive rifampin for the treatment of Staphylococcus aureus bacteremia with deep infections: A meta-analysis

Background

Staphylococcus aureus (S. aureus) bacteremia (SAB) has high morbidity and mortality, with the development of methicillin-resistant S. aureus (MRSA) and the recognized shortcomings of vancomycin, its management is becoming more complicated. Considering the capability to penetrate cells, tissues and biofilms, rifampin has been used as adjunctive agent to against staphylococcal activity.

Objectives

We performed this meta-analysis, aimed to explore the efficacy of adjunctive rifampin for the treatment of SAB.

Methods

Medical literatures were searched in the Pubmed, Medline, Embase and Cochrane databases up to October 2018. Patients with SAB received treatment with or without rifampin were included. The risk ratio (RR) and 95% confidence intervals (CI) of mortality, rate of bacteriological failure and relapse were estimated.

Results

Seven articles (five randomized controlled trials and two retrospective cohort studies) enrolling 979 and 636 patients of SAB treated with and without rifampin, respectively, were included. There was no difference of mortality between the adjunctive rifampin therapy and standard therapy on SAB (RR: 0.771, 95% CI: 0.442 to 1.347, I² = 70.4%). In the subgroup analyses, the decreased mortality was observed in the adjunctive rifampin treatment for patients without MRSA infection (RR: 0.509, 95% CI: 0.372 to 0.697, I² = 8.8%). In addition, there was no difference of the rate of bacteriologic failure (RR: 0.602, 95% CI: 0.198 to 1.825, I² = 0.0%) or relapse (RR: 0.574, 95% CI: 0.106 to 3.112, I² = 77.9%) between the adjunctive rifampin therapy and standard therapy on SAB.

Conclusions

In general, insufficient evidence supported the efficacy of adjunctive use of rifampin for treatment of SAB, adding rifampin to standard therapy didn’t decrease the incidence of death, rate of bacteriologic failure and relapse.

Effects of a rifampicin pre-treatment on linezolid pharmacokinetics

Linezolid is an oxazolidinone antibiotic that effectively treats methicillin-resistant Staphylococcus aureus (MRSA) and vancomycin-resistant Enterococci (VRE). Since rifampicin induces other antibiotic effects, it is combined with linezolid in therapeutic regimes. However, linezolid blood concentrations are reduced by this combination, which increases the risk of the emergence of antibiotic-resistant bacteria. We herein demonstrated that the combination of linezolid with rifampicin inhibited its absorption and promoted its elimination, but not through microsomal enzymes. Our results indicate that the combination of linezolid with rifampicin reduces linezolid blood concentrations via metabolic enzymes.

Treatments and limitations for methicillin-resistant Staphylococcus aureus: A review of current literature

Methicillin-resistant Staphylococcus aureus (MRSA) has remained a major threat to healthcare; in both hospital and community settings over the past five decades. With the current use of antibiotics for a variety of infections, including MRSA, emerging resistance is a major concern. Currently available treatments have restrictions limiting their use. These issues include, but are not limited to, side effects, cross-resistance, lack of understanding of pharmacokinetics and clinical pharmacodynamics, gradual increment in minimal inhibitory concentration over the period (MIC creep) and ineffectiveness in dealing with bacterial biofilms. Despite availability of various therapeutic options for MRSA, the clinical cure rates remain low with high morbidity and mortality. Given these challenges with existing treatments, there is a need for development of novel agents for MRSA. Along with prompt infection control strategies and strict implementation of antibiotic stewardship, cautious use of newer anti-MRSA agents will be of utmost importance. This article reviews the treatments and limitations of MRSA management and highlights the future path.

A study on combination of daptomycin with selected antimicrobial agents: in vitro synergistic effect of MIC value of 1 mg/L against MRSA strains

Background

Daptomycin is an important drug used in the treatment of methicillin-resistant Staphylococcus aureus (MRSA) infection. A high dose of daptomycin is indicated for an MRSA infection with a minimum inhibitory concentration (MIC) of 1 mg/L for daptomycin. Combination therapies with daptomycin and other antimicrobial agents, including fosfomycin, display in vitro synergism potentially. This study was conducted to investigate the in vitro synergistic effect of daptomycin-based combination therapy against MRSA strains with high daptomycin MIC.

Method

The synergistic effects of daptomycin in combination with fosfomycin, gentamicin, linezolid, oxacillin, or rifampicin against MRSA with an MIC of 1 mg/L for daptomycin were measured using the microbroth checkerboard assay in vitro.

Result

A total of 100 MRSA isolates was tested. The synergistic interactions of the drugs were evaluated using the fractional inhibitory concentration index. The MIC values revealed that all isolates (100%) were found to be susceptible to linezolid, 85% to fosfomycin, 8% to gentamicin, 69% to rifampicin, and no isolate was susceptible to oxacillin. The in vitro synergism rates of daptomycin in combination with fosfomycin, oxacillin, gentamicin, linezolid, and rifampicin were 37, 11, 5, 3, and 1%, respectively.

Conclusion

The combination of daptomycin plus fosfomycin may be an effective therapeutic option for MRSA infection.

Electronic supplementary material

The online version of this article (10.1186/s40360-019-0305-y) contains supplementary material, which is available to authorized users.

Rifampicin-Loaded Mesoporous Silica Nanoparticles for the Treatment of Intracellular Infections

Infectious diseases remain a major burden in today’s world, causing high mortality rates and significant economic losses, with >9 million deaths per year predicted by 2030. Invasion of host cells by intracellular bacteria poses treatment challenges due to the poor permeation of antimicrobials into the infected cells. To overcome these limitations, mesoporous silica nanoparticles (MSNP) loaded with the antibiotic rifampicin were investigated as a nanocarrier system for the treatment of intracellular bacterial infection with specific interest in the influence of particle size on treatment efficiency. An intracellular infection model was established using small colony variants (SCV) of S. aureus in macrophages to systemically evaluate the efficacy of rifampicin-loaded MSNP against the pathogen as compared to a rifampicin solution. As hypothesized, the superior uptake of MSNP by macrophages resulted in an enhanced treatment efficacy of the encapsulated rifampicin as compared to free antibiotic. This study provides a potential platform to improve the performance of currently available antibiotics against intracellular infections.

Adjunctive rifampicin to reduce early mortality from Staphylococcus aureus bacteraemia: the ARREST RCT

BACKGROUND

Staphylococcus aureus bacteraemia is a common and frequently fatal infection. Adjunctive rifampicin may enhance early S. aureus killing, sterilise infected foci and blood faster, and thereby reduce the risk of dissemination, metastatic infection and death.

OBJECTIVES

To determine whether or not adjunctive rifampicin reduces bacteriological (microbiologically confirmed) failure/recurrence or death through 12 weeks from randomisation. Secondary objectives included evaluating the impact of rifampicin on all-cause mortality, clinically defined failure/recurrence or death, toxicity, resistance emergence, and duration of bacteraemia; and assessing the cost-effectiveness of rifampicin.

DESIGN

Parallel-group, randomised (1 : 1), blinded, placebo-controlled multicentre trial.

SETTING

UK NHS trust hospitals.

PARTICIPANTS

Adult inpatients (≥ 18 years) with meticillin-resistant or susceptible S. aureus grown from one or more blood cultures, who had received < 96 hours of antibiotic therapy for the current infection, and without contraindications to rifampicin.

INTERVENTIONS

Adjunctive rifampicin (600-900 mg/day, oral or intravenous) or placebo for 14 days in addition to standard antibiotic therapy. Investigators and patients were blinded to trial treatment. Follow-up was for 12 weeks (assessments at 3, 7, 10 and 14 days, weekly until discharge and final assessment at 12 weeks post randomisation).

MAIN OUTCOME MEASURES

The primary outcome was all-cause bacteriological (microbiologically confirmed) failure/recurrence or death through 12 weeks from randomisation.

RESULTS

Between December 2012 and October 2016, 758 eligible participants from 29 UK hospitals were randomised: 370 to rifampicin and 388 to placebo. The median age was 65 years [interquartile range (IQR) 50-76 years]. A total of 485 (64.0%) infections were community acquired and 132 (17.4%) were nosocomial; 47 (6.2%) were caused by meticillin-resistant S. aureus. A total of 301 (39.7%) participants had an initial deep infection focus. Standard antibiotics were given for a median of 29 days (IQR 18-45 days) and 619 (81.7%) participants received flucloxacillin. By 12 weeks, 62 out of 370 (16.8%) patients taking rifampicin versus 71 out of 388 (18.3%) participants taking the placebo experienced bacteriological (microbiologically confirmed) failure/recurrence or died [absolute risk difference -1.4%, 95% confidence interval (CI) -7.0% to 4.3%; hazard ratio 0.96, 95% CI 0.68 to 1.35; p = 0.81]. There were 4 (1.1%) and 5 (1.3%) bacteriological failures (p = 0.82) in the rifampicin and placebo groups, respectively. There were 3 (0.8%) versus 16 (4.1%) bacteriological recurrences (p = 0.01), and 55 (14.9%) versus 50 (12.9%) deaths without bacteriological failure/recurrence (p = 0.30) in the rifampicin and placebo groups, respectively. Over 12 weeks, there was no evidence of differences in clinically defined failure/recurrence/death (p = 0.84), all-cause mortality (p = 0.60), serious (p = 0.17) or grade 3/4 (p = 0.36) adverse events (AEs). However, 63 (17.0%) participants in the rifampicin group versus 39 (10.1%) participants in the placebo group experienced antibiotic or trial drug-modifying AEs (p = 0.004), and 24 (6.5%) participants in the rifampicin group versus 6 (1.5%) participants in the placebo group experienced drug-interactions (p = 0.0005). Evaluation of the costs and health-related quality-of-life impacts revealed that an episode of S. aureus bacteraemia costs an average of £12,197 over 12 weeks. Rifampicin was estimated to save 10% of episode costs (p = 0.14). After adjustment, the effect of rifampicin on total quality-adjusted life-years (QALYs) was positive (0.004 QALYs), but not statistically significant (standard error 0.004 QALYs).

CONCLUSIONS

Adjunctive rifampicin provided no overall benefit over standard antibiotic therapy in adults with S. aureus bacteraemia.

FUTURE WORK

Given the substantial mortality, other antibiotic combinations or improved source management should be investigated.

TRIAL REGISTRATIONS

Current Controlled Trials ISRCTN37666216, EudraCT 2012-000344-10 and Clinical Trials Authorisation 00316/0243/001.

FUNDING

This project was funded by the National Institute for Health Research (NIHR) Health Technology Assessment programme and will be published in full in Health Technology Assessment; Vol. 22, No. 59. See the NIHR Journals Library website for further project information.

Ciprofloxacin and Rifampin Dual Antibiotic-Loaded Biopolymer Chitosan Sponge for Bacterial Inhibition

Complex extremity wounds in Wounded Warriors can become contaminated with microbes, which may cause clinical outcomes resulting in amputation, morbidity, or even fatality. Local delivery of multiple or broad-spectrum antibiotics allows practicing clinicians treatment solutions that may inhibit biofilm formation. Propagation of vancomycin-resistant Staphylococcus aureus is also a growing concern. The development of vancomycin-resistant S. aureus has become a critical challenge in nosocomial infection prevention in the USA, but to date has seen little occurrence in osteomyelitis. As an alternative, locally delivered ciprofloxacin and rifampin were investigated in a preclinical model for the prevention of biofilm in complex extremity wounds with implanted fixation device. In vitro assays demonstrated ciprofloxacin and rifampin possess an additive effect against Gram-negative Pseudomonas aeruginosa and were actively eluted from a chitosan sponge based local delivery system. In an in vivo orthopedic hardware-associated polymicrobial model (S. aureus and Escherichia coli) the combination was able to achieve complete clearance of both bacterial strains. E. coli was detected in bone of untreated animals, but did not form biofilm on wires. Results reveal the clinical potential of antibiotic-loaded chitosan sponges to inhibit infection through tailored antibiotic selection at desired concentrations with efficacy towards biofilm inhibition.

Psoitis and multiple venous thromboses caused by Panton Valentine Leukocidin-positive methicillin-sensitive Staphylococcus aureus in a 12-year-old girl: A case report

Panton Valentine Leukocidin (PVL) is one of the many toxins produced by Staphylococcus aureus. In Japan, PVL-positive S. aureus strains are mainly methicillin-resistant S. aureus (MRSA). Data regarding PVL-positive methicillin-sensitive S. aureus (MSSA) are scarce. In this report, we describe a case of severe infection by PVL-positive MSSA. A 12-year-old healthy girl was admitted with high fever and pain in the lower back. Computed tomography revealed a diagnosis of psoitis and multiple venous thromboses. Blood cultures obtained after admission revealed infection with MSSA. Her fever continued despite adequate antibiotic therapy. On the fifth hospitalization day, she developed bladder dysfunction, and an abscess was noted near the third lumbar vertebra. She underwent an emergency operation and recovered. Bacterial analyses revealed that the causative MSSA was a PVL-producing single variant of ST8 (related to USA300clone), of sequence type 2149. PVL is known to cause platelet activation. This case demonstrates the need for detailed analyses of the causative strain of bacteria in cases of S. aureus infection with deep vein thrombosis, even in cases of known MSSA infection.

Evaluation of Telavancin Alone and Combined with Ceftaroline or Rifampin against Methicillin-Resistant Staphylococcus aureus in an In Vitro Biofilm Model

Infections caused by biofilm-producing methicillin-resistant Staphylococcus aureus (MRSA) bacteria are challenging due to increasing antibiotic resistance. Synergistic activities of lipopeptides and lipoglycopeptides with β-lactams have been demonstrated for MRSA, but little is known about biofilm-embedded organisms. Our objective was to evaluate two telavancin (TLV) dosage regimens (7.5 mg/kg of body weight and 10 mg/kg every 24 h [q24h]) alone and in combination with ceftaroline (CPT) (600 mg every 8 h [q8h]) or rifampin (RIF) (450 mg every 12 h [q12h]) against two biofilm-producing MRSA strains (494 and N315). Pharmacokinetic/pharmacodynamic CDC biofilm reactor models with polyurethane coupons were used to evaluate the efficacies of the antibiotic combinations over 72 h. Overall, there were no significant differences observed between the two TLV dosing regimens either alone or in combination with RIF or CPT against these strains. Both TLV dosing regimens and CPT alone demonstrated killing but did not reach bactericidal reduction at 72 h. However, both TLV regimens in combination with RIF demonstrated enhanced activity against both strains, with a rapid decrease in CFU/ml at 4 h that was bactericidal and maintained over the 72-h experiment (-Δ3.75 log10 CFU/ml from baseline; P < 0.0001). Of interest, no enhanced activity was observed for TLV combined with CPT. No development of resistance was observed in any of the combination models. However, resistance to RIF developed as early as 24 h, with MIC values exceeding 32 mg/liter. Our results show that TLV plus RIF displayed therapeutic improvement against biofilm-producing MRSA. These results suggest that TLV at 7.5 and 10 mg/kg q24h are equally effective in eradicating biofilm-associated MRSA strains in vitro.

Minimum inhibitory concentration and killing properties of rifampicin against canine Staphylococcus pseudintermedius isolates from dogs in the southeast USA

BACKGROUND

Meticillin-resistant (MR) staphylococcal pyoderma in dogs has led to increased use of alternate antibiotics such as rifampicin (RFP). However, little information exists regarding its pharmacodynamics in MR Staphylococcus pseudintermedius.

HYPOTHESIS/OBJECTIVES

To determine the minimum inhibitory concentration (MIC) and killing properties of RFP for canine Staphylococcus pseudintermedius isolates.

METHODS

The MIC of RFP was determined using the ETEST® for 50 meticillin-susceptible (MS) and 50 MR S. pseudintermedius isolates collected from dogs. From these isolates, two MS isolates (RFP MIC of 0.003 and 0.008 μg/mL, respectively) and two MR isolates (RFP MIC of 0.003 and 0.012 μg/mL, respectively) were subjected to time-kill studies. Mueller-Hinton broth was supplemented with RFP at 0, 0.5, 1, 2, 4, 8, 16 and 32 times the MIC for 0, 2, 4, 10, 16 and 24 h. The number of viable colony forming units in each sample was determined using a commercial luciferase assay kit.

RESULTS

The MIC50 and MIC90 were the same for MS and MR isolates, at 0.004 μg/mL and 0.008 μg/mL, respectively. Rifampicin kill curves were not indicative of concentration-dependency, suggesting time-dependent activity. Two isolates (MS 0.003 and 0.008 μg/mL) exhibited bacteriostatic activity, whereas two others (MR 0.003 and 0.012 μg/mL) exhibited bactericidal activity.

CONCLUSIONS AND CLINICAL IMPORTANCE

This study demonstrated that MS and MR S. pseudintermedius isolates were equally susceptible to rifampicin and that dosing intervals should be designed for time-dependent efficacy. These data can support pharmacokinetic studies of RFP in dogs with susceptible infections caused by S. pseudintermedius.

Targeting intracellular Staphylococcus aureus to lower recurrence of orthopaedic infection

Staphylococcus aureus is often found in orthopaedic infections and may be protected from commonly prescribed antibiotics by forming biofilms or growing intracellularly within osteoblasts. To investigate the effect of non-antibiotic compounds in conjunction with antibiotics to clear intracellular and biofilm forming S. aureus causing osteomyelitis. SAOS-2 osteoblast-like cell lines were infected with S. aureus BB1279. Antibiotics (vancomycin, VAN; and dicloxacillin, DICLOX), bacterial efflux pump inhibitors (piperine, PIP; carbonyl cyanide m-chlorophenyl hydrazone, CCCP), and bone morphogenetic protein (BMP-2) were evaluated individually and in combination to kill intracellular bacteria. We present direct evidence that after gentamicin killed extracellular planktonic bacteria and antibiotics had been stopped, seeding from the infected osteoblasts grew as biofilms. VAN was ineffective in treating the intracellular bacteria even at 10× MIC; however in presence of PIP or CCCP the intracellular S. aureus was significantly reduced. Bacterial efflux pump inhibitors (PIP and CCCP) were effective in enhancing permeability of antibiotics within the osteoblasts and facilitated killing of intracellular S. aureus. Confocal laser scanning microscopy (CLSM) showed increased uptake of propidium iodide within osteoblasts in presence of PIP and CCCP. BMP-2 had no effect on growth of S. aureus either alone or in combination with antibiotics. Combined application of antibiotics and natural agents could help in the treatment of osteoblast infected intracellular bacteria and biofilms associated with osteomyelitis. © 2017 Orthopaedic Research Society. Published by Wiley Periodicals, Inc. J Orthop Res 36:1086-1092, 2018.

Searching for Bacterial Biofilm in Recurrent Cholangitis in Primary Sclerosing Cholangitis: A Case Presentation and Introduction of an Unexplored Disease Mechanism

Inflammation and fibrosis of the bile ducts are the defining pathological characteristics of primary sclerosing cholangitis (PSC). A previously unexplored mechanism for recurrent cholangitis, one of PSC's most common presentations, is bacterial colonization of the biliary epithelium in the form of biofilm, which may confer resistance to antibiotics and host phagocytic machinery. The aim of the current study was to assess whether bacteria could be seen on the liver explant and whether they organized in the form of biofilm. An explanted PSC liver from a 60-year-old male who suffered from recurrent cholangitis was formalin-fixed, paraffin-embedded and Gram stained. The specimens were observed under light microscopy. Neither bacteria nor biofilm were detected. We did not detect bacteria or biofilm in the liver explant of a single PSC patient with recurrent cholangitis using standard light microscopy. We suspect this may be in part due to techniques related to tissue preservation and microscopy.

Micellar chemotherapeutic platform based on a bifunctional salicaldehyde amphiphile delivers a "combo-effect" for heightened killing of MRSA

The devastating infections caused by methicillin-resistant Staphylococcus aureus (MRSA) coupled with its high resistance towards antibiotics underscores the need for an effective anti-MRSA therapeutic. The present study illustrates the use of a salicylaldehyde based bactericidal amphiphile (C1) in generating a micellar carrier that renders delivery of therapeutic antibiotics. The inherent membrane-targeting activity of C1 present in the micelle could be leveraged to counter the resistance of MRSA and enhance cellular uptake of the released antibiotics, resulting in effective elimination of the pathogen. The inherent bactericidal and antibiofilm activity of C1 was captured in FESEM analysis, solution-based assays and fluorescence microscopy. ANS-based fluorescence spectroscopy indicated that the critical micelle concentration (CMC) for C1 was 18.5 μM in water. DLS studies and FESEM analysis indicated that the average particle size for micelles based on C1 (C1_M) and rifampicin-loaded C1_M (C1_M- R) was smaller than vancomycin-loaded C1_M (C1_M- V). C1_M- R and C1_M- V rendered sustained release of the antibiotics in physiologically relevant fluids. Notably, following interaction with MRSA for 3 h, the relative anti-MRSA activity of C1_M- R and C1_M- V was nearly 12-fold and 8-fold higher, respectively, as compared to the free antibiotics at equivalent concentration, highlighting the merit of leveraging the activity of C1 and the antibiotic concurrently in the micellar system. The relative cell-free antibiotic was also manifold lower in the case of C1_M- R and C1_M- V treated MRSA as against treatment with free antibiotics, suggesting that the amphiphilic warhead breached the membrane barrier and enhanced cellular uptake of the released antibiotics. Interestingly, C1_M- R and C1_M- V exhibited a high therapeutic index, being non-toxic to HEK 293 cells at concentrations higher than their minimum inhibitory concentration (MIC) against MRSA and they could be employed as an antibacterial coating to prevent MRSA biofilm formation on surgical silk sutures. The antibiotic-replete biocompatible micelles based on a self-assembling membrane-targeting amphiphile described herein represent a promising framework to integrate multiple warheads and generate a potent anti-MRSA therapeutic material.