Rifampin combination therapy for nonmycobacterial infections

Drugs for treating infections caused by non-tubercular mycobacteria: a narrative review from the study group on mycobacteria of the Italian Society of Infectious Diseases and Tropical Medicine

BACKGROUND

Non-tuberculous mycobacteria (NTM) are generally free-living organism, widely distributed in the environment, with sporadic potential to infect. In recent years, there has been a significant increase in the global incidence of NTM-related disease, spanning across all continents and an increased mortality after the diagnosis has been reported. The decisions on whether to treat or not and which drugs to use are complex and require a multidisciplinary approach as well as patients' involvement in the decision process.

METHODS AND RESULTS

This review aims at describing the drugs used for treating NTM-associated diseases emphasizing the efficacy, tolerability, optimization strategies as well as possible drugs that might be used in case of intolerance or resistance. We also reviewed data on newer compounds highlighting the lack of randomised clinical trials for many drugs but also encouraging preliminary data for others. We also focused on non-pharmacological interventions that need to be adopted during care of individuals with NTM-associated diseases CONCLUSIONS: Despite insufficient efficacy and poor tolerability this review emphasizes the improvement in patients' care and the needs for future studies in the field of anti-NTM treatments.

Development and Validation of a New Reversed Phase HPLC Method for the Quantitation of Azithromycin and Rifampicin in a Capsule Formulation

This research aimed to develop a new method for simultaneously estimating the presence of azithromycin (AZT) and rifampicin (RIF) in a capsule formulation using reverse-phase high-performance liquid chromatography. The developed method utilized a Gemini column with a 60:40% v/v acetonitrile and potassium dihydrogen phosphate mobile phase, a flow rate of 1 mL/min, and an injection volume of 20 μL. The detection wavelengths of 210 and 254 nm for AZT and RIF, respectively, were used. Validation ensures specificity with a peak purity index > 0.99999 for AZT and >0.99995 for RIF, affirming unambiguous analyte detection. The system suitability test, within acceptable limits, validates method reliability. Linearity calibration curves (R2 = 0.998) cover a 25-150% target concentration range. Accuracy studies employing the standard addition method yield recovery values between 96.6 and 103.9% for both drugs, confirming method accuracy. Precision studies reveal % relative standard deviation values consistently below 2%, highlighting reproducibility. Robustness testing supports method reliability under varying conditions. Application to a pharmaceutical capsule formulation demonstrates the method's practicality, accurately quantifying AZT (98.30%) and RIF (99.37%). This study provides a validated analytical approach for simultaneous quantification in commercial pharmaceutical products containing both drugs, enhancing pharmaceutical quality control for critical antibiotics in complex formulations.

The use of combination therapy for the improvement of colistin activity against bacterial biofilm

Colistin is used as a last resort for the management of infections caused by multi-drug resistant (MDR) bacteria. However, the use of this antibiotic could lead to different side effects, such as nephrotoxicity, in most patients, and the high prevalence of colistin-resistant strains restricts the use of colistin in the clinical setting. Additionally, colistin could induce resistance through the increased formation of biofilm; biofilm-embedded cells are highly resistant to antibiotics, and as with other antibiotics, colistin is impaired by bacteria in the biofilm community. In this regard, the researchers used combination therapy for the enhancement of colistin activity against bacterial biofilm, especially MDR bacteria. Different antibacterial agents, such as antimicrobial peptides, bacteriophages, natural compounds, antibiotics from different families, N-acetylcysteine, and quorum-sensing inhibitors, showed promising results when combined with colistin. Additionally, the use of different drug platforms could also boost the efficacy of this antibiotic against biofilm. The mentioned colistin-based combination therapy not only could suppress the formation of biofilm but also could destroy the established biofilm. These kinds of treatments also avoided the emergence of colistin-resistant subpopulations, reduced the required dosage of colistin for inhibition of biofilm, and finally enhanced the dosage of this antibiotic at the site of infection. However, the exact interaction of colistin with other antibacterial agents has not been elucidated yet; therefore, further studies are required to identify the precise mechanism underlying the efficient removal of biofilms by colistin-based combination therapy.

Rifampicin does not reduce moxifloxacin concentrations at the site of infection and may not improve treatment outcome of a one-stage exchange surgery protocol of implant-associated osteomyelitis lesions in a porcine model

We aimed to evaluate moxifloxacin steady-state concentrations in infected bone and soft tissue and to explore the additive microbiological and pathological treatment effect of rifampicin to standard moxifloxacin treatment of implant-associated osteomyelitis (IAO). 16 pigs were included. On Day 0, IAO was induced in the proximal tibia using a susceptible Staphylococcus aureus strain. On Day 7, the pigs underwent one-stage exchange surgery of the IAO lesions and were randomized to receive seven days of intravenous antibiotic treatment of either rifampicin combined with moxifloxacin or moxifloxacin monotherapy. On Day 14, microdialysis was applied for continuous sampling (8 h) of moxifloxacin concentrations. Microbiological, macroscopical pathology, and histopathological analyses were performed postmortem. Steady-state moxifloxacin area under the concentration-time curve was lower in the combination therapy group in plasma (total) and subcutaneous tissue compartments (infected and noninfected) (p < 0.04), while no differences were found in bone compartments. No additional treatment effect of rifampicin to moxifloxacin treatment was found (p = 0.57). Conclusive, additive rifampicin treatment does not reduce moxifloxacin concentrations at the infection site. Rifampicin treatment may not be necessary in a one-stage exchange treatment of IAO. However, our sample size and treatment period may have been too small and short to reveal true clinical differences.

Evaluating generalizability of artificial intelligence models for molecular datasets

Deep learning has made rapid advances in modeling molecular sequencing data. Despite achieving high performance on benchmarks, it remains unclear to what extent deep learning models learn general principles and generalize to previously unseen sequences. Benchmarks traditionally interrogate model generalizability by generating metadata based (MB) or sequence-similarity based (SB) train and test splits of input data before assessing model performance. Here, we show that this approach mischaracterizes model generalizability by failing to consider the full spectrum of cross-split overlap, i.e., similarity between train and test splits. We introduce Spectra, a spectral framework for comprehensive model evaluation. For a given model and input data, Spectra plots model performance as a function of decreasing cross-split overlap and reports the area under this curve as a measure of generalizability. We apply Spectra to 18 sequencing datasets with associated phenotypes ranging from antibiotic resistance in tuberculosis to protein-ligand binding to evaluate the generalizability of 19 state-of-the-art deep learning models, including large language models, graph neural networks, diffusion models, and convolutional neural networks. We show that SB and MB splits provide an incomplete assessment of model generalizability. With Spectra, we find as cross-split overlap decreases, deep learning models consistently exhibit a reduction in performance in a task- and model-dependent manner. Although no model consistently achieved the highest performance across all tasks, we show that deep learning models can generalize to previously unseen sequences on specific tasks. Spectra paves the way toward a better understanding of how foundation models generalize in biology.

Neuroinvasive Francisella tularensis Infection: Report of 2 Cases and Review of the Literature

BACKGROUND

Neuroinvasive infection with Francisella tularensis, the causative agent of tularemia, is rare. Establishing clinical suspicion is challenging if risk factors or clinical features classically associated with tularemia are absent. Tularemia is treatable with antibiotics; however, there are limited data to inform management of potentially fatal neuroinvasive infection.

METHODS

We collected epidemiologic and clinical data on 2 recent US cases of neuroinvasive F. tularensis infection, and performed a literature review of cases of neuroinvasive F. tularensis infection published after 1950.

RESULTS

One patient presented with focal neurologic deficits and brain lesions; broad-range molecular testing on resected brain tissue detected F. tularensis. The other patient presented with meningeal signs; tularemia was suspected based on animal exposure, and F. tularensis grew in cerebrospinal fluid (CSF) culture. Both patients received combination antibiotic therapy and recovered from infection. Among 16 published cases, tularemia was clinically suspected in 4 cases. CSF often displayed lymphocytic pleocytosis. Among cases with available data, CSF culture was positive in 13 of 16 cases, and F. tularensis antibodies were detected in 11 of 11 cases. Treatment typically included an aminoglycoside combined with either a tetracycline or a fluoroquinolone. Outcomes were generally favorable.

CONCLUSIONS

Clinicians should consider neuroinvasive F. tularensis infection in patients with meningitis and signs suggestive of tularemia or compatible exposures, lymphocyte-predominant CSF, unrevealing standard microbiologic workup, or lack of response to empiric bacterial meningitis treatment. Molecular testing, culture, and serologic testing can reveal the diagnosis. Favorable outcomes can be achieved with directed antibiotic treatment.

The Controversial Effect of Antibiotics on Methicillin-Sensitive S. aureus: A Comparative In Vitro Study

Methicillin-sensitive Staphylococcus (S.) aureus (MSSA) bacteremia remains a global challenge, despite the availability of antibiotics. Primary treatments include β-lactam agents such as cefazolin and flucloxacillin. Ongoing discussions have focused on the potential synergistic effects of combining these agents with rifampicin or fosfomycin to combat infections associated with biofilm formation. Managing staphylococcal infections is challenging due to antibacterial resistance, biofilms, and S. aureus's ability to invade and replicate within host cells. Intracellular invasion shields the bacteria from antibacterial agents and the immune system, often leading to incomplete bacterial clearance and chronic infections. Additionally, S. aureus can assume a dormant phenotype, known as the small colony variant (SCV), further complicating eradication and promoting persistence. This study investigated the impact of antibiotic combinations on the persistence of S. aureus 6850 and its stable small colony variant (SCV strain JB1) focusing on intracellular survival and biofilm formation. The results from the wild-type strain 6850 demonstrate that β-lactams combined with RIF effectively eliminated biofilms and intracellular bacteria but tend to select for SCVs in planktonic culture and host cells. Higher antibiotic concentrations were associated with an increase in the zeta potential of S. aureus, suggesting reduced membrane permeability to antimicrobials. When using the stable SCV mutant strain JB1, antibiotic combinations with rifampicin successfully cleared planktonic bacteria and biofilms but failed to eradicate intracellular bacteria. Given these findings, it is reasonable to report that β-lactams combined with rifampicin represent the optimal treatment for MSSA bacteremia. However, caution is warranted when employing this treatment over an extended period, as it may elevate the risk of selecting for small colony variants (SCVs) and, consequently, promoting bacterial persistence.

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.

Early Staphylococcal Periprosthetic Joint Infection (PJI) Treated with Debridement, Antibiotics, and Implant Retention (DAIR): Inferior Outcomes in Patients with Staphylococci Resistant to Rifampicin

It is unknown how rifampicin resistance in staphylococci causing a periprosthetic joint infection (PJI) affects outcomes after debridement, antibiotics, and implant retention (DAIR). We thus aimed to compare the risk of relapse in DAIR-treated early PJI caused by staphylococci with or without rifampicin resistance. In total, 81 patients affected by early PJI were included, and all patients were treated surgically with DAIR. This was repeated if needed. The endpoint of relapse-free survival was estimated using the Kaplan-Meier method, and Cox regression models were fitted to assess the risk of infection relapse for patients infected with rifampicin-resistant bacteria, adjusted for age, sex, type of joint, and type of index surgery. In patients with rifampicin-resistant staphylococci, relapse was seen in 80% after one DAIR procedure and in 70% after two DAIR procedures. In patients with rifampicin-sensitive bacteria, 51% had an infection relapse after one DAIR procedure and 33% had an infection relapse after two DAIR procedures. Patients with rifampicin-resistant staphylococcal PJI thus had an increased adjusted risk of infection relapse of 1.9 (95% CI: 1.1-3.6, p = 0.04) after one DAIR procedure compared to patients with rifampicin-sensitive bacteria and a 4.1-fold (95% CI: 1.2-14.1, p = 0.03) increase in risk of infection relapse after two DAIR procedures. Staphylococcal resistance to rifampicin is associated with inferior outcomes after DAIR. These findings suggest that DAIR may not be a useful strategy in early PJI caused by rifampicin-resistant staphylococci.

Combinatorial efficacy of Manuka honey and antibiotics in the in vitro control of staphylococci and their small colony variants

Introduction

Staphylococci are among the list of problematic bacteria contributing to the global antibiotic resistance (ABR) crisis. Their ability to adopt the small colony variant (SCV) phenotype, induced by prolonged antibiotic chemotherapy, complicates staphylococcal infection control options. Novel and alternative approaches are needed to tackle staphylococcal infections and curb ABR. Manuka honey (MH), a non-antibiotic alternative is recognized for its unique antibacterial activity based on its methylglyoxal (MGO) component.

Methods

In this study, MH (MGO 830+) was tested in combination with gentamicin (GEN), rifampicin (RIF), or vancomycin (VA) against staphylococcal wildtype (WT) and SCVs. To our knowledge, there are no current studies in the literature documenting the effects of MH on staphylococcal SCVs. While Staphylococcus aureus is well-studied for its international ABR burden, limited data exists demonstrating the effects of MH on S. epidermidis and S. lugdunensis whose pathogenic relevance and contribution to ABR is also rising.

Results & discussion

The three staphylococci were most susceptible to RIF (0.06-0.24 μg/ml), then GEN (0.12-0.49 μg/ml), and lastly VA (0.49-0.96 μg/ml). The MICs of MH were 7%, 7-8%, and 6-7% (w/v), respectively. Fractional inhibitory concentration (FIC) evaluations showed that the combined MH + antibiotic effect was either additive (FICI 1-2), or partially synergistic (FICI >0.5-1). While all three antibiotics induced SCVs in vitro, stable SCVs were observed in GEN treatments only. The addition of MH to these GEN-SCV-induction analyses resulted in complete suppression of SCVs (p<0.001) in all three staphylococci, suggesting that MH's antibacterial properties interfered with GEN's SCV induction mechanisms. Moreover, the addition of MH to growth cultures of recovered stable SCVs resulted in the inhibition of SCV growth by at least 99%, indicating MH's ability to prevent subsequent SCV growth. These in vitro analyses demonstrated MH's broad-spectrum capabilities not only in improving WT staphylococci susceptibility to the three antibiotics, but also mitigated the development and subsequent growth of their SCV phenotypes. MH in combination with antibiotics has the potential to not only resensitize staphylococci to antibiotics and consequently require less antibiotic usage, but in instances where prolonged chemotherapy is employed, the development and growth of SCVs would be hampered, providing a better clinical outcome, all of which mitigate ABR.

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.

Successful Treatment of Infective Endocarditis With Oral Antibiotics: A Case Report

Infective endocarditis (IE) is a serious and potentially life-threatening infection of the heart valves. It is commonly treated with prolonged courses of intravenous antibiotics, and in some cases, surgical intervention may also be necessary. While the use of oral antibiotics in the treatment of IE is generally limited, there are select cases where they may be considered as an alternative treatment option. Here, we report a case of staphylococcal right-sided IE successfully treated with oral antibiotics (linezolid and rifampicin). Our case highlights the potential for oral antibiotics to be used as step-down therapy for select patients with IE.

Comparing the Synergistic and Antagonistic Interactions of Ciprofloxacin and Levofloxacin Combined with Rifampin against Drug-Resistant Staphylococcus aureus: A Time-Kill Assay

BACKGROUND

Treatment of device-related infections by drug-resistant Staphylococcus aureus can be challenging, and combination therapy has been proposed as a potential solution. We compared the effectiveness of levofloxacin-rifampin and ciprofloxacin-rifampin combinations in killing methicillin-resistant S. aureus (MRSA) using a time-kill assay.

METHODS

We randomly selected 15 vancomycin-susceptible S. aureus (VSSA) strains, 3 vancomycin-intermediate S. aureus (VISA) strains, and 12 heterogeneous VISA (hVISA) strains from the Asian Bacterial Bank. Time-kill experiments were performed in duplicate for each isolate. Viable bacterial counts were determined at 0 h, 4 h, 8 h, and 24 h for the ciprofloxacin- and levofloxacin-rifampin combinations at 1× MIC and 0.5× MIC. We compared synergistic and antagonistic interactions between the two combinations.

RESULTS

The viable bacterial count significantly decreased after 24 h of exposure to ciprofloxacin-rifampin and levofloxacin-rifampin combinations, with synergy observed more frequently in isolates exposed to ciprofloxacin-rifampin (43.3%) than levofloxacin-rifampin (20.0%) (p = 0.0082). The synergistic interactions of both combinations were more frequently observed in resistant strains with high MICs of ciprofloxacin (≥16 mg/L) and levofloxacin (≥8 mg/L). Levofloxacin tended to exhibit more frequent antagonistic interactions with rifampin than ciprofloxacin, although there was no statistical difference in antagonism between the two combinations.

CONCLUSIONS

Our study demonstrated that ciprofloxacin exhibits superior synergistic activity against MRSA strains, including VISA/hVISA, when combined with rifampin compared with levofloxacin. High MICs of fluoroquinolones were found to predict synergism. Our results suggest that ciprofloxacin may be a more effective choice than levofloxacin for combination therapy with rifampin in the treatment of MRSA infections.

Antimicrobial treatment of patients with a periprosthetic joint infection: basic principles

The antibiotic treatment of periprosthetic joint infections (PJI) is complicated by the presence of biofilm produced by bacteria on the abiotic surface of the implant. Bacteria within the deeper layers of the biofilm become metabolically less active, resulting in antibiotic tolerance due to several mechanisms. This review describes the basic principles of antibiotic treatment in PJI in relation to the behavior of bacteria within the biofilm. The concept of biofilm-active antibiotics will be explained from an in vitro as well as in vivo perspective. Evidence from clinical studies on biofilm-active antibiotics in PJI will be highlighted, mainly focusing on the role of rifampicin for Gram-positive microorganisms and fluoroquinolones for Gram-negative microorganisms. The optimal treatment duration will be discussed as the timing of switching to oral antibiotic therapy.

Staphylococcal Biofilm: Penetration and bioavailability of vancomycin with or without rifampin

We measured antibiotic penetration and bioavailability in staphylococcus biofilms using simulated humanized concentrations of fluorescent vancomycin plus or minus rifampin. Vancomycin percent recovery across biofilm layers was:upper = 46%, middle = 40%, and lower = 33%. Vancomycin plus rifampin was not significantly different (P = 0.65). Addition of rifampin did not improve vancomycin penetration across biofilm layers.

Investigation of Multi-Subunit Mycobacterium tuberculosis DNA-Directed RNA Polymerase and Its Rifampicin Resistant Mutants

Emerging Mycobacterium tuberculosis (Mtb) resistant strains have continued to limit the efficacies of existing antitubercular therapies. More specifically, mutations in the RNA replicative machinery of Mtb, RNA polymerase (RNAP), have been widely linked to rifampicin (RIF) resistance, which has led to therapeutic failures in many clinical cases. Moreover, elusive details on the underlying mechanisms of RIF-resistance caused by Mtb-RNAP mutations have hampered the development of new and efficient drugs that are able to overcome this challenge. Therefore, in this study we attempt to resolve the molecular and structural events associated with RIF-resistance in nine clinically reported missense Mtb RNAP mutations. Our study, for the first time, investigated the multi-subunit Mtb RNAP complex and findings revealed that the mutations commonly disrupted structural-dynamical attributes that may be essential for the protein's catalytic functions, particularly at the βfork loop 2, β'zinc-binding domain, the β' trigger loop and β'jaw, which in line with previous experimental reports, are essential for RNAP processivity. Complementarily, the mutations considerably perturbed the RIF-BP, which led to alterations in the active orientation of RIF needed to obstruct RNA extension. Consequentially, essential interactions with RIF were lost due to the mutation-induced repositioning with corresponding reductions in the binding affinity of the drug observed in majority of the mutants. We believe these findings will significantly aid future efforts in the discovery of new treatment options with the potential to overcome antitubercular resistance.

The Potential of Antibiotics and Nanomaterial Combinations as Therapeutic Strategies in the Management of Multidrug-Resistant Infections: A Review

Antibiotic resistance has become a major public health concern around the world. This is exacerbated by the non-discovery of novel drugs, the development of resistance mechanisms in most of the clinical isolates of bacteria, as well as recurring infections, hindering disease treatment efficacy. In vitro data has shown that antibiotic combinations can be effective when microorganisms are resistant to individual drugs. Recently, advances in the direction of combination therapy for the treatment of multidrug-resistant (MDR) bacterial infections have embraced antibiotic combinations and the use of nanoparticles conjugated with antibiotics. Nanoparticles (NPs) can penetrate the cellular membrane of disease-causing organisms and obstruct essential molecular pathways, showing unique antibacterial mechanisms. Combined with the optimal drugs, NPs have established synergy and may assist in regulating the general threat of emergent bacterial resistance. This review comprises a general overview of antibiotic combinations strategies for the treatment of microbial infections. The potential of antibiotic combinations with NPs as new entrants in the antimicrobial therapy domain is discussed.

Treatment of periprosthetic joint infections guided by minimum biofilm eradication concentration (MBEC) in addition to minimum inhibitory concentration (MIC): protocol for a prospective randomised clinical trial

INTRODUCTION

Prosthetic joint infections (PJIs) are disastrous complications for patients and costly for healthcare organisations. They may promote bacterial resistance due to the extensive antibiotic use necessary in the PJI treatment. The PJI incidence is estimated to be 1%-3%, but the absolute numbers worldwide are high and increasing as large joint arthroplasties are performed by the millions each year. Current treatment algorithms, based on implant preserving surgery or full revision followed by a semitailored antibiotic regimen for no less than 2-3 months, lead to infection resolution in approximately 60% and 90%, respectively. Antibiotic choice is currently guided by minimum inhibitory concentrations (MICs) of free-living bacteria and not of bacteria in biofilm growth mode. Biofilm assays with relatively rapid output for the determination of minimum biofilm eradication concentrations (MBECs) have previously been developed but their clinical usefulness have not been established.

METHODS AND ANALYSIS

This single-blinded, two-arm randomised study of hip or knee staphylococcal PJI will evaluate 6-week standard of care (MIC guided), or an alternative antibiotic regimen according to an MBEC-guided-based decision algorithm. Sixty-four patients with a first-time PJI treated according to the debridement, antibiotics, and implant retention principle will be enrolled at a single tertiary orthopaedic centre (Sahlgrenska University Hospital). Patients will receive 14 days of standard parenteral antibiotics before entering the comparative study arms. The primary outcome measurement is the proportion of changes in antimicrobial regimen from first-line treatment dependent on randomisation arm. Secondary endpoints are unresolved infection, how microbial properties including biofilm abilities and emerging antimicrobial resistance correlate to infection outcomes, patient reported outcomes and costs with a 12-month follow-up.

ETHICS AND DISSEMINATION

Approval is received from the Swedish Ethical Review Authority, no 2020-01471 and the Swedish Medical Products Agency, EudraCT, no 2020-003444-80.

TRIAL REGISTRATION NUMBER

ClinicalTrials.gov ID: NCT04488458.

Rifampicin treatment of canine multidrug-resistant meticillin-resistant staphylococcal pyoderma: A retrospective study of 51 cases

BACKGROUND

Rifampicin (RFP) is a potential treatment for canine multidrug-resistant (MDR) meticillin-resistant staphylococci (MRS), yet the use of lower doses based on recent MIC data has not been evaluated in vivo.

HYPOTHESIS/OBJECTIVES

To provide information on the efficacy and safety of low-dose range RFP (≤6 mg/kg/day) for the treatment of canine MDR MRS pyoderma.

ANIMALS

Fifty-one client-owned dogs.

MATERIALS AND METHODS

Retrospective review of dogs medical records. Dogs were from 11 US dermatology referral practices and had oral RFP at ≤6 mg/kg/day. Data evaluated included response to treatment, adverse events, and serum changes in alanine aminotransferase (ALT) and alkaline phosphatase (ALP).

RESULTS

Complete resolution of pyoderma occurred in 39 of 51 dogs (76.5%). Topical antimicrobials were used concurrently in most cases (47 of 51; 92.2%). ALP elevation >1.5-fold of baseline or the high end of the reference range occurred in nine of 37 (24.3%) dogs, while ALT elevation above baseline and the high end of the reference range occurred in two of 36 (5.6%). Only six of 51 (11.8%) had clinical adverse events during treatment; five of six (83.3%) were mild reactions consisting of lethargy and gastrointestinal signs, while one dog had a possible cutaneous adverse drug reaction. Of those that experienced clinical adverse events, four of six (66.7%) did not have concurrent increased liver enzyme activity, while two of six (33.3%) had elevations in ALP alone.

CONCLUSIONS AND CLINICAL RELEVANCE

Low-dose RFP (≤6 mg/kg/day) appears to be a relatively safe and effective single-agent systemic antibiotic in combination with topical antimicrobials for canine MDR MRS pyoderma.

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.

A flux-based machine learning model to simulate the impact of pathogen metabolic heterogeneity on drug interactions

Drug combinations are a promising strategy to counter antibiotic resistance. However, current experimental and computational approaches do not account for the entire complexity involved in combination therapy design, such as the effect of pathogen metabolic heterogeneity, changes in the growth environment, drug treatment order, and time interval. To address these limitations, we present a comprehensive approach that uses genome-scale metabolic modeling and machine learning to guide combination therapy design. Our mechanistic approach (a) accommodates diverse data types, (b) accounts for time- and order-specific interactions, and (c) accurately predicts drug interactions in various growth conditions and their robustness to pathogen metabolic heterogeneity. Our approach achieved high accuracy (area under the receiver operating curve (AUROC) = 0.83 for synergy, AUROC = 0.98 for antagonism) in predicting drug interactions for Escherichia coli cultured in 57 metabolic conditions based on experimental validation. The entropy in bacterial metabolic response was predictive of combination therapy outcomes across time scales and growth conditions. Simulation of metabolic heterogeneity using population FBA identified two subpopulations of E. coli cells defined by the levels of three proteins (eno, fadB, and fabD) in glycolysis and lipid metabolism that influence cell tolerance to a broad range of antibiotic combinations. Analysis of the vast landscape of condition-specific drug interactions revealed a set of 24 robustly synergistic drug combinations with potential for clinical use.

Beyond the approved: target sites and inhibitors of bacterial RNA polymerase from bacteria and fungi

Covering: 2016 to 2022RNA polymerase (RNAP) is the central enzyme in bacterial gene expression representing an attractive and validated target for antibiotics. Two well-known and clinically approved classes of natural product RNAP inhibitors are the rifamycins and the fidaxomycins. Rifampicin (Rif), a semi-synthetic derivative of rifamycin, plays a crucial role as a first line antibiotic in the treatment of tuberculosis and a broad range of bacterial infections. However, more and more pathogens such as Mycobacterium tuberculosis develop resistance, not only against Rif and other RNAP inhibitors. To overcome this problem, novel RNAP inhibitors exhibiting different target sites are urgently needed. This review includes recent developments published between 2016 and today. Particular focus is placed on novel findings concerning already known bacterial RNAP inhibitors, the characterization and development of new compounds isolated from bacteria and fungi, and providing brief insights into promising new synthetic compounds.

In vitro Investigation of Antibiotic Combinations against Multi- and Extensively Drug-Resistant Klebsiella pneumoniae

Objectives: Community and hospital acquired K. pneumoniae infections have become a ubiquitous medical issue due to the limited treatment options and high mortality rate therefore the aims of this study are in vitro investigation of double antimicrobial combinations against multidrug resistant (MDR) and extensively drug resistant (XDR) isolates. Materials and Methods: Antimicrobial susceptibility of twelve isolates from eight Bulgarian hospitals was determined to study the interaction effect of selected double combinations in accordance to fractional inhibitory concentration (FIC) method. Furthermore, the isolates were subjected to genotyping by Multilocus sequence typing (MLST) and detection of carbapenemase genes by multiplex PCR. The results were assessed by groups of strains with either NDM or KPC carbapenemase. Results: Nine antimicrobial combinations: meropenem-colistin, meropenem-fosfomycin, meropenem-gentamicin, meropenem-rifampicin, meropenem-tigecycline, colistin-fosfomycin, colistin-gentamicin, colistin-rifampicin and colistin-tigecycline were tested for synergism on twelve K. pneumoniae, producing either KPC-2 (KPC-KP, 41.7%, 5/12) or NDM-1 (NDM-KP, 58.3%, 7/12). The isolates were distributed in three sequence types: ST11 (58.3%, 7/12), ST15 (25%, 3/12) and ST258 (16.7%, 2/12). All KPC-KP (ST258 and ST15) originated from three hospitals. The rest were NDM-1 carriers isolated from six hospitals and belonged to ST11. The highest synergistic effect was determined for MER-GEN (83.3%, 10/12) and COL-RIF (83.3%, 10/12). The MER-FOS combination was most efficient against NDM-KP, opposite to the KPC strains. Antagonism was not observed for any combinations. Conclusions: The evaluated joint synergistic effect of the MER-GEN and COL-RIF may facilitate the treatment options for patients infected with NDM- and KPC-KP, whereas MER-FOS is highly synergetic against NDM-KP.

Rifampicin for COVID-19

Vaccinations for coronavirus disease-2019 (COVID-19) have begun more than a year before, yet without specific treatments available. Rifampicin, critically important for human medicine (World Health Organization’s list of essential medicines), may prove pharmacologically effective for treatment and chemoprophylaxis of healthcare personnel and those at higher risk. It has been known since 1969 that rifampicin has a direct selective antiviral effect on viruses which have their own RNA polymerase (severe acute respiratory syndrome coronavirus 2), like the main mechanism of action of remdesivir. This involves inhibition of late viral protein synthesis, the virion assembly, and the viral polymerase itself. This antiviral effect is dependent on the administration route, with local application resulting in higher drug concentrations at the site of viral replication. This would suggest also trying lung administration of rifampicin by nebulization to increase the drug’s concentration at infection sites while minimizing systemic side effects. Recent in silico studies with a computer-aided approach, found rifampicin among the most promising existing drugs that could be repurposed for the treatment of COVID-19.

Investigational agents for the treatment of methicillin-resistant Staphylococcus aureus (MRSA) bacteremia: progress in clinical trials

INTRODUCTION

Bacteremia caused by Staphylococcus aureus is common. Cases caused by methicillin-resistant S. aureus (MRSA) are particularly formidable and often lethal. The mortality associated with MRSA bacteremia has not significantly decreased over the past couple of decades and concerns regarding efficacy and toxicity of standard therapy highlight the need for novel agents and new therapeutic approaches.

AREAS COVERED

This paper explores clinical trials investigating novel therapeutic approaches to S. aureus bacteremia. There is a special focus on MRSA bacteremia. Monotherapy and combination therapies and novel antimicrobials and adjunctive therapies that are only recently being established for therapeutic use are discussed.

EXPERT OPINION

The unfavorable safety profile of combination antimicrobial therapy in clinical trials has outweighed its benefits. Therefore, future investigation should focus on optimizing duration and de-escalation protocols. Antibody and bacteriophage lysin-based candidates have mostly been limited to safety trials, but progress with these agents is demonstrated through a lysin-based agent receiving a phase III trial. Antibiotics indicated for use in treating MRSA skin infections see continued investigation as treatments for MRSA bacteremia despite the difficulty of completing trials in this patient population. Promising agents include dalbavancin, ceftobiprole, ceftaroline, and exebacase.

Real time monitoring of Staphylococcus aureus biofilm sensitivity towards antibiotics with isothermal microcalorimetry

Biofilm-associated infections with Staphylococcus aureus are difficult to treat even after administration of antibiotics that according to the standard susceptibility assays are effective. Currently, the assays used in the clinical laboratories to determine the sensitivity of S. aureus towards antibiotics are not representing the behaviour of biofilm-associated S. aureus, since these assays are performed on planktonic bacteria. In research settings, microcalorimetry has been used for antibiotic susceptibility studies. Therefore, in this study we investigated if we can use isothermal microcalorimetry to monitor the response of biofilm towards antibiotic treatment in real-time. We developed a reproducible method to generate biofilm in an isothermal microcalorimeter setup. Using this system, the sensitivity of 5 methicillin-sensitive S. aureus (MSSA) and 5 methicillin-resistant S. aureus (MRSA) strains from different genetic lineages were determined towards: flucloxacillin, cefuroxime, cefotaxime, gentamicin, rifampicin, vancomycin, levofloxacin, clindamycin, erythromycin, linezolid, fusidic acid, co-trimoxazole, and doxycycline. In contrast to conventional assays, our calorimetry-based biofilm susceptibility assay showed that S. aureus biofilms, regardless MSSA or MRSA, can survive the exposure to the maximum serum concentration of all tested antibiotics. The only treatment with a single antibiotic showing a significant reduction in biofilm survival was rifampicin, yet in 20% of the strains, emerging antibiotic resistance was observed. Furthermore, the combination of rifampicin with flucloxacillin, vancomycin or levofloxacin was able to prevent S. aureus biofilm from becoming resistant to rifampicin. Isothermal microcalorimetry allows real-time monitoring of the sensitivity of S. aureus biofilms towards antibiotics in a fast and reliable way.

Penicillin- and third-generation cephalosporin-resistant strains of Streptococcus pneumoniae meningitis: Case report and literature review

BACKGROUND

Treatment of patients with penicillin-resistant S. pneumoniae (PRSP) is complicated because of the relatively poor blood-brain barrier penetration of effective antimicrobials. Our case: A previously healthy 70-year-old woman, a traveler from China to Japan, was admitted to our hospital with fever and loss of consciousness. She has no history of pneumococcal vaccination. She was diagnosed with bacterial meningitis due to penicillin-and third-generation cephalosporin-resistant strains of S. pneumoniae. The patient was successfully treated with a combination therapy of vancomycin (VCM) and levofloxacin (LVFX) and recovered without any neurological sequelae. As the treatment of penicillin-and third-generation cephalosporin-resistant strains of S. pneumoniae meningitis remains unclear, we conducted a review of the reported cases of meningitis caused by penicillin- and cephalosporin-resistant S. pneumoniae.

METHOD

We performed a search using the keywords "penicillin-resistant Streptococcus pneumoniae," "meningitis," and "pneumococcal meningitis". We searched the electronic databases PubMed, Embase, and Ichushi from their inception to March 2020. Subsequently, two authors independently reviewed the resulting database records, retrieved full texts for eligibility assessment, and extracted data from these cases.

RESULT

We identified 18 papers describing thirty-five cases of penicillin- and cephalosporin-resistant S. pneumoniae meningitis including our case. The patient's characteristics were; median age: 50 years, men:50%, 85% of cases received combination regimens of antibiotics: Ceftroriaxone (CTRX) plus VCM (20 cases), CTRX plus VCM plus rifampicin (RFP) (two cases), CTRX plus linezolid (one case), fluoroquinolones (two cases), carbapenems (six cases), Thirty-five percent received steroids. Twenty-four percent of patients died. Twenty-six percent of patients complicated neurological sequalae.

CONCLUSION

Combination therapy including VCM plus LVFX could be a treatment option.

Rifamycin resistance, rpoB gene mutation, and clinical outcomes of Staphylococcus species isolated from prosthetic joint infections in Korea

PURPOSE

We conducted an in vitro investigation of rifamycin activity against planktonic and biofilm states of Staphylococcus aureus and S. epidermidis isolated from patients with prosthetic join infection (PJIs), characterized their rpoB mutations, and analyzed the clinical outcomes of rifampin-resistant isolates.

METHODS

A total of 110 staphylococcal isolates were collected from patients with PJIs. Antimicrobials tested using the broth microdilution method included rifampin, rifabutin, rifapentine, and rifaximin. We evaluated rpoB gene mutations to identify rifampin resistance mechanisms. Clinical outcomes were assessed in rifampin-resistant isolates.

RESULTS

Among the 110 staphylococcal isolates, we detected 85 S. aureus (methicillin-resistant, 55%) and 25 S. epidermidis (methicillin-resistant, 100%) isolates. Seven S. aureus isolates and two S. epidermidis isolates were rifampin resistant (minimum inhibitory concentration [MIC], ≥ 2 μg/mL); these exhibited rpoB gene mutations. Among 78 rifampin-susceptible S. aureus isolates and 23 S. epidermidis isolates, 76 S. aureus isolates and all S. epidermidis isolates were highly susceptible (MIC ≤ 0.06 μg/mL) to other rifamycins. The rifampin, rifabutin, rifapentine, and rifaximin minimum biofilm bactericidal concentrations for ≥ 50% of isolates were 4, 1, 2, and 4 μg/mL for S. aureus and 1, 0.125, 0.25, and 0.5 μg/mL for S. epidermidis, respectively, among rifampin-susceptible isolates. Among nine patients bearing rifampin-resistant isolates, only three (33%) had successful outcomes.

CONCLUSIONS

Rifamycins other than rifampin show promising staphylococcal activity, including antibiofilm activity. Rifamycin-resistant staphylococci exhibit rpoB gene mutations.

Molecular Characterization of Rifampicin-Resistant Staphylococcus aureus Isolates from Retail Foods in China

This study investigated the molecular characteristics of rifampin-resistant (RIF-R) Staphylococcus aureus isolates recovered from 4300 retail food samples covering most provincial capitals in China, from 2011 to 2016. Of the 1463 S. aureus enrolled, 149 isolates (142 MSSA and 7 MRSA) were identified as rifampicin-resistant, including 20 high-level (MICs ≥ 8 μg/mL) and 129 low-level (MICs between 2 and 4 μg/mL) rifampicin-resistant strains. Most of the RIF-R S. aureus isolates were resistant to more than three antibiotics. The mutations in the rifampicin resistance-determining region of the rpoB gene were studied in all RIF-R strains. All of the strains presented the mutational change 481 His/Asn and five isolates presented an additional mutation, including 477 Asp/Tyr, 527 Ile/Met, and 466 Leu/Ser, respectively. Thirteen STs and twenty-one spa types were represented, in which five MRSA showed non-type SCCmec and the remaining MRSA belonged to SCCmec type IV-where, ST1-t127 was the predominant type from all of the isolates, while ST398-t034 was the predominant type for the MRSA isolates. In this study, we found that the food-related RIF-R S. aureus may have a unique genetic background selection. However, the scenario regarding the presence of RIF-R S. aureus, especially MRSA, in retail food in China is not favorable and warrants public attention.

Pleiotropic Effects of Statins: New Therapeutic Approaches to Chronic, Recurrent Infection by Staphylococcus aureus

An emergent approach to bacterial infection is the use of host rather than bacterial-directed strategies. This approach has the potential to improve efficacy in especially challenging infection settings, including chronic, recurrent infection due to intracellular pathogens. For nearly two decades, the pleiotropic effects of statin drugs have been examined for therapeutic usefulness beyond the treatment of hypercholesterolemia. Interest originated after retrospective studies reported decreases in the risk of death due to bacteremia or sepsis for those on a statin regimen. Although subsequent clinical trials have yielded mixed results and earlier findings have been questioned for biased study design, in vitro and in vivo studies have provided clear evidence of protective mechanisms that include immunomodulatory effects and the inhibition of host cell invasion. Ultimately, the benefits of statins in an infection setting appear to require attention to the underlying host response and to the timing of the dosage. From this examination of statin efficacy, additional novel host-directed strategies may produce adjunctive therapeutic approaches for the treatment of infection where traditional antimicrobial therapy continues to yield poor outcomes. This review focuses on the opportunistic pathogen, Staphylococcus aureus, as a proof of principle in examining the promise and limitations of statins in recalcitrant infection.

Rifamycin antibiotics and the mechanisms of their failure

Rifamycins are a class of antibiotics that were first discovered in 1957 and are known for their use in treating tuberculosis (TB). Rifamycins exhibit bactericidal activity against many Gram-positive and Gram-negative bacteria by inhibiting RNA polymerase (RNAP); however, resistance is prevalent and the mechanisms range from primary target modification and antibiotic inactivation to cytoplasmic exclusion. Further, phenotypic resistance, in which only a subpopulation of bacteria grow in concentrations exceeding their minimum inhibitory concentration, and tolerance, which is characterized by reduced rates of bacterial cell death, have been identified as additional causes of rifamycin failure. Here we summarize current understanding and recent developments regarding this critical antibiotic class.

Identification and Characterization of Pleiotropic High-Persistence Mutations in the Beta Subunit of the Bacterial RNA Polymerase

Mutations conferring resistance to bactericidal antibiotics reduce the average susceptibility of mutant populations. It is unknown, however, how those mutations affect the survival of individual bacteria. Since surviving bacteria can be a reservoir for recurring infections, it is important to know how survival rates may be affected by resistance mutations and by the choice of antibiotics. Here, we present evidence that (i) Escherichia coli mutants with 100 to 1,000 times increased frequency of survival in ciprofloxacin, an archetypal fluoroquinolone antibiotic, can be readily obtained in a stepwise selection; (ii) the high survival frequency is conferred by mutations in the switch region of the beta subunit of the RNA polymerase; (iii) the switch-region mutations are (p)ppGpp mimics, partially analogous to rpoB stringent mutations; (iv) the stringent and switch region rpoB mutations frequently occur in clinical isolates of E. coli, Acinetobacter baumannii, Mycobacterium tuberculosis, and Staphylococcus aureus, and at least one of them, RpoB S488L, which is a common rifampicin resistance mutations, dramatically increases the survival of a clinical methicillin-resistant S. aureus (MRSA) strain in ampicillin; and (v) the RpoB-associated high-survival phenotype can be reversed by subinhibitory concentrations of chloramphenicol.

Genomic and in vitro pharmacodynamic analysis of rifampicin resistance in multidrug-resistant canine Staphylococcus pseudintermedius isolates

BACKGROUND

Antimicrobial resistance is a growing concern in canine Staphylococcus pseudintermedius dermatitis. Treatment with rifampicin (RFP) is considered only in meticillin-resistant and multidrug-resistant S. pseudintermedius (MDR-MRSP).

HYPOTHESIS/OBJECTIVES

To determine an optimal RFP dosing for MDR-MRSP treatment without induction of RFP resistance and identify causal mutations for antimicrobial resistance.

METHODS AND MATERIALS

Time-kill assays were performed in a control isolate and three MDR-MRSP isolates at six clinically relevant concentrations [32 to 1,024 × MIC (the minimum inhibitory concentration)]. Whole-genome resequencing and bioinformatic analysis were performed in the resistant strains developed in this assay.

RESULTS

The genomic analysis identified nine antimicrobial resistance genes (ARGs) in MDR-MRSP isolates, which are responsible for resistance to seven classes of antibiotics. RFP activity against all four isolates was consistent with a time-dependent and bacteriostatic response. RFP resistance was observed in six of the 28 time-kill assays, including concentrations 64 × MIC in MDR-MRSP1 isolates at 24 h, 32 × MIC in MDR-MRSP2 at 48 h, 32 × MIC in MDR-MRSP3 at 48 h and 256 × MIC in MDR-MRSP3 at 24 h. Genome-wide mutation analyses in these RFP-resistant strains discovered the causal mutations in the coding region of the rpoB gene.

CONCLUSIONS AND CLINICAL RELEVANCE

A study has shown that 6 mg/kg per os results in plasma concentrations of 600-1,000 × MIC of S. pseudintermedius. Based on our data, this dose should achieve the minimum MIC (×512) to prevent RFP resistance development; therefore, we recommend a minimum daily dose of 6 mg/kg for MDR-MRSP pyoderma treatment when limited antibiotic options are available.

Microbiome-immune interactions in tuberculosis

Tuberculosis (TB) remains an infectious disease of global significance and a leading cause of death in low- and middle-income countries. Significant effort has been directed towards understanding Mycobacterium tuberculosis genomics, virulence, and pathophysiology within the framework of Koch postulates. More recently, the advent of “-omics” approaches has broadened our appreciation of how “commensal” microbes have coevolved with their host and have a central role in shaping health and susceptibility to disease. It is now clear that there is a diverse repertoire of interactions between the microbiota and host immune responses that can either sustain or disrupt homeostasis. In the context of the global efforts to combatting TB, such findings and knowledge have raised important questions: Does microbiome composition indicate or determine susceptibility or resistance to M. tuberculosis infection? Is the development of active disease or latent infection upon M. tuberculosis exposure influenced by the microbiome? Does microbiome composition influence TB therapy outcome and risk of reinfection with M. tuberculosis? Can the microbiome be actively managed to reduce risk of M. tuberculosis infection or recurrence of TB? Here, we explore these questions with a particular focus on microbiome-immune interactions that may affect TB susceptibility, manifestation and progression, the long-term implications of anti-TB therapy, as well as the potential of the host microbiome as target for clinical manipulation.

Differential effects of cotreatment of the antibiotic rifampin with host-directed therapeutics in reducing intracellular Staphylococcus aureus infection

Background

Chronic infection by Staphylococcus aureus drives pathogenesis in important clinical settings, such as recurrent pulmonary infection in cystic fibrosis and relapsing infection in osteomyelitis. Treatment options for intracellular S. aureus infection are limited. Rifampin, a lipophilic antibiotic, readily penetrates host cell membranes, yet monotherapy is associated with rapid antibiotic resistance and development of severe adverse events. Antibiotic cotreatment can reduce this progression, yet efficacy diminishes as antibiotic resistance develops. ML141 and simvastatin inhibit S. aureus invasion through host-directed rather than bactericidal mechanisms.

Objective

To determine whether cotreatment of ML141 or of simvastatin with rifampin would enhance rifampin efficacy.

Methods

Assays to assess host cell invasion, host cell viability, host cell membrane permeability, and bactericidal activity were performed using the human embryonic kidney (HEK) 293-A cell line infected with S. aureus (29213) and treated with vehicle control, simvastatin, ML141, rifampin, or cotreatment of simvastatin or ML141 with rifampin.

Results

We found cotreatment of ML141 with rifampin reduced intracellular infection nearly 85% when compared to the no treatment control. This decrease more than doubled the average 40% reduction in response to rifampin monotherapy. In contrast, cotreatment of simvastatin with rifampin failed to improve rifampin efficacy. Also, in contrast to ML141, simvastatin increased propidium iodide (PI) positive cells, from an average of 10% in control HEK 293-A cells to nearly 20% in simvastatin-treated cells, indicating an increase in host cell membrane permeability. The simvastatin-induced increase was reversed to control levels by cotreatment of simvastatin with rifampin.

Conclusion

Taken together, rifampin efficacy is increased through host-directed inhibition of S. aureus invasion by ML141, while efficacy is not increased by simvastatin. Considerations regarding novel therapeutic approaches may be dependent on underlying differences in pharmacology.

An ultra-sensitive "turn-off" fluorescent sensor for the trace detection of rifampicin based on glutathione-stabilized copper nanoclusters

Rifampicin is a common antibiotic used in human and veterinary medicine to treat tuberculosis and other diseases caused by numerous pathogenic bacteria. However, the excessive or improper use of rifampicin usually leads to a series of problems, including bacterial resistance, excessive drug-resistance and water pollution. Thus, it is of great importance to develop selective and sensitive assays for monitoring rifampicin in biological systems. In this study, we designed a fluorescence "turn-off" strategy for the trace detection of rifampicin based on a glutathione-stabilized copper nanoclusters (GSH-Cu NC) sensor. In an aqueous solution, the fluorescence of the GSH-Cu NCs at 632 nm can be quenched effectively and selectively by rifampicin due to the inner-filter effect (IFE) of fluorescence mechanism. Distinctively, this GSH-Cu NC sensor exhibited excellent fluorescence sensing capability for the trace detection of rifampicin with a very low limit of detection (LOD) of 16 pM in a wide linear range from 50 to 10 000 pM. It is not only more sensitive than the other methods previously reported for the detection of rifampicin, but also has an outstanding selectivity and strong anti-interference in complex samples. Furthermore, the as-developed GSH-Cu NCs were also successfully applied to determine rifampicin in different real samples with quantitative spike recoveries ranging from 97% to 105%.

Pseudomonas aeruginosa Implant-Associated Bone and Joint Infections: Experience in a Regional Reference Center in France

Background:P. aeruginosa implant-associated bone and joint infections (BJI) is considered to be one of the most difficult to treat BJI. The data focusing specifically on this pathogen are sparse, and it seems difficult to extrapolate the results obtained with Enterobacteriaceae.

Methods: We performed a retrospective observation study of all P. aeruginosa implant-associated BJI diagnosed at our institution from 2011 to 2018. We defined failure as any type of relapse, including persistence of the same P. aeruginosa, superinfection by another organism(s) or any other cause of relapse such as the need for a subsequent surgery. Nonparametric statistical methods were used to compare the study groups and Kaplan-Meier curves and multivariate Cox analysis and were used to detect determinants associated with treatment failure.

Results: A total of 90 patients (62% men, median age 60 years IQR 47–72) including 30 (33%) prosthetic-joint infections and 60 (66%) other implant-associated BJIs were studied. Most of them were acute (62%). During the prolonged follow-up, (median 20 months; IQR 9–37), 23 patients (26%) experienced treatment failure. Optimal surgical treatment (DAIR for acute forms, explantation, 1-stage or 2-stage exchange for others) was significantly associated with a higher success rate in the univariate analysis (p = 0.003). Sixty-four (71%) patients received effective initial treatment against P. aeruginosa administered and 81 of them (90%) did for at least 3 weeks: both these parameters correlated with a higher success rate. In the multivariate Cox-analysis optimal surgical treatment, IV effective treatment of at least 3 weeks and treatment with ciprofloxacin for at least 3 months proved to be independently associated to a better outcome in patients with P. aeruginosa implant-associated BJI.

Conclusion:P. aeruginosa implant-associated BJI is one of the most difficult-to-treat BJI, with a strong impact on the prognosis of the surgical strategy. An effective initial IV antibiotic treatment for at least 3 weeks seems to be required, followed by oral ciprofloxacin for a total duration of 3 months.

Prediction of rifampicin resistance beyond the RRDR using structure-based machine learning approaches

Rifampicin resistance is a major therapeutic challenge, particularly in tuberculosis, leprosy, P. aeruginosa and S. aureus infections, where it develops via missense mutations in gene rpoB. Previously we have highlighted that these mutations reduce protein affinities within the RNA polymerase complex, subsequently reducing nucleic acid affinity. Here, we have used these insights to develop a computational rifampicin resistance predictor capable of identifying resistant mutations even outside the well-defined rifampicin resistance determining region (RRDR), using clinical M. tuberculosis sequencing information. Our tool successfully identified up to 90.9% of M. tuberculosis rpoB variants correctly, with sensitivity of 92.2%, specificity of 83.6% and MCC of 0.69, outperforming the current gold-standard GeneXpert-MTB/RIF. We show our model can be translated to other clinically relevant organisms: M. leprae, P. aeruginosa and S. aureus, despite weak sequence identity. Our method was implemented as an interactive tool, SUSPECT-RIF (StrUctural Susceptibility PrEdiCTion for RIFampicin), freely available at https://biosig.unimelb.edu.au/suspect_rif/ .

Antibacterial Activity of Selected Essential Oil Compounds Alone and in Combination with β-Lactam Antibiotics Against MRSA Strains

This study aimed to determine the effect of selected essential oil compounds (EOCs) on the antibacterial activity of β-lactam antibiotics (βLAs) against methicillin-resistant Staphylococcus aureus (MRSA) strains. The following parameters were studied: antibiotic susceptibility testing, detection of mecA gene and evaluation of genotypic relativity of isolates using molecular techniques, analysis of chemical composition applying Fourier-transform infrared (FTIR) spectroscopy, and determination of antibacterial activity of EOCs alone and in combination with βLAs against MRSA strains using microdilution and checkerboard methods. It was found that all isolates expressed MRSA and resistance phenotypes for macrolides, lincosamides, and streptogramins B. All isolates harbored the mecA gene and belonged to three distinct genotypes. Eight of the 10 EOCs showed efficient antimicrobial activity against the MRSA reference strain. The analysis of interaction between EOCs and βLAs against the MRSA reference strain revealed a synergistic and additive effect of the following combinations: methicillin (Met)-linalyl acetate (LinAc), penicillin G (Pen)-1,8-cineole (Cin), and Pen-LinAc. Analysis of EOC-βLA interactions showed a synergistic and additive effect in the following combinations: Met-LinAc (against low- and high-level βLAs resistance strains), Pen-Cin, and Pen-LinAc (against low-level βLAs resistance strains). It was also confirmed that changes in phosphodiester, -OH, -CH₂ and -CH₃ groups may change the interactions with βLAs. Moreover, the presence of two CH₃O- moieties in the Met molecule could also play a key role in the synergistic and additive mechanism of LinAc action with Met against MRSA strains. Direct therapy using a Met-LinAc combination may become an alternative treatment method for staphylococcal infections caused by MRSA. However, this unconventional therapy must be preceded by numerous cytotoxicity tests.

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).

Antimicrobial Resistance of Staphylococcus aureus Isolated from Hospital Wastewater in Kermanshah, Iran

Introduction

Hospital wastewater contains highly resistant and virulent bacteria that can spread into the environment. This study was conducted to investigate the antimicrobial resistance of methicillin-resistant Staphylococcus aureus (MRSA) and methicillin-sensitive S. aureus (MSSA) in raw and treated hospital wastewater.

Methods

During a three-month period, 40 sewage samples were collected from the hospital sewage (Kermanshah, Iran), and S. aureus were identified using culture and biochemical tests. MRSA was detected by resistance to cefoxitin. Antibiotic resistance (AR) was determined using disk diffusion according to the Clinical and Laboratory Standards Institute (CLSI) in 20 MSSA (10 raw and 10 treated sewage) and 40 MRSA isolates (20 raw and 20 treated sewage). The antimicrobial resistance genes (ARGs) were determined by PCR.

Results

Eleven and eight percent of the isolates were MRSA in raw and treated sewage samples, respectively. Out of 60 isolates, 59 (98%) were multidrug resistant (MDR). The most common ARGs were mecA (raw=100%, treated=100%), aacA-D (raw=100%, treated=85%) and tetK (raw =95%, treated =45%) in MRSA, while the tetM gene was the most abundant gene (raw=50%, treated=80%) in MSSA. None of isolates (n=60) was positive for the vanB gene. MSSR (n=20) had the highest level of resistance against penicillin (100%), clindamycin (raw=90%, treated=90%), azithromycin (raw=80%, treated=90%). All MRSA isolates (n=40,100%) in both raw and treated sewage samples were non-susceptible to penicillin, oxacillin and azithromycin. There was no significant difference in the frequency AR and ARGs between raw and treated sewage samples (p>0.05).

Conclusion

The results indicated a high frequency of MDR and ARGs in both raw and treated sewage isolates which could be released into the environment through sewage system and pose a serious threat to public health. Hospital wastewater treatment processes should be improved in order to prevent the dissemination of the most resistant strains of S. aureus.

Oral switch versus standard intravenous antibiotic therapy in left-sided endocarditis due to susceptible staphylococci, streptococci or enterococci (RODEO): a protocol for two open-label randomised controlled trials

INTRODUCTION

Left-sided infective endocarditis (IE) is a serious infection with a heavy burden for patients and healthcare system. Oral switch after initial intravenous antibiotic therapy may reduce costs and improve patients' discomfort without increasing unfavourable outcomes. We describe the methodology of two simultaneously conducted open-label randomised trials aiming to assess non-inferiority of oral switch as compared with entirely intravenous antibiotic therapy for the treatment of left-sided IE.

METHODS AND ANALYSIS

Two simultaneous multicentre open-label prospective randomised trials assessing non-inferiority of oral switch during antibiotic treatment as compared with entirely intravenous therapy in patients with left-sided IE are ongoing. One trial is dedicated to left-sided IE caused by multisusceptible staphylococci (Relais Oral Dans le traitement des Endocardites à staphylocoques ou streptOcoques (RODEO)-1) and the other is dedicated to left-sided IE caused by susceptible streptococci or enterococci (RODEO-2). It is planned to randomise 324 patients in each trial after an initial course of at least 10 days of intravenous antibiotic therapy either to continue intravenous antibiotic therapy or to switch to oral antibiotic therapy. The primary outcome is treatment failure within 3 months after the end of antibiotic treatment, a composite outcome defined by all-cause death and/or symptomatic embolic events and/or unplanned valvular surgery and/or microbiological relapse (with the primary pathogen). Secondary outcomes include patient quality of life, echocardiographic outcome, costs and efficiency associated with IE care. Statistical analysis will be performed with a non-inferiority margin of 10% and a one-sided 2.5% type I error.

ETHICS AND DISSEMINATION

Written informed consent will be obtained from all participants. This study was approved by Tours Research ethics committee (CPP TOURS-Region Centre-Ouest 1, 2015-R26, 23 February 2016). Study findings will be published in peer-reviewed journals and disseminated through presentation at relevant national and international conferences.

TRIAL REGISTRATION NUMBER

EudraCT Number: 2015-002371-16 and NCT02701608; NCT02701595.

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.

How to manage KPC infections

Carbapenemase-producing Enterobacteriaceae represent an increasing global threat worldwide and Klebsiella pneumoniae carbapenemase (KPC)-producing K. pneumoniae (KPC-KP) has become one of the most important contemporary pathogens, especially in endemic areas. Risk stratification and rapid diagnostics laboratory workflows are of paramount importance and indication for therapy of KPC-KP infection must be individualized according to the baseline characteristics of the patient and severity of infection. The optimal treatment of infection because of KPC-KP organisms is uncertain and antibiotic options are limited. The knowledge of the patient's pathophysiology, infection site, and application of the pharmacokinetic/pharmacodynamic principles on the basis of minimum inhibitory concentration (MIC) has progressively gained major relevance. Combination therapies including high-dose meropenem, colistin, fosfomycin, tigecycline, and aminoglycosides are widely used, with suboptimal results. In the past few years, new antimicrobials targeting KPC-KP have been developed and are now at various stages of clinical research. However, their optimal use should be guaranteed in the long term for delaying, as much as possible, the emergence of resistance. Strict infection control measures remain necessary. The aim of this review is to discuss the challenges in the management and treatment of patients with infections because KPC-KP and provide an expert opinion.

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.

Calcium sulphate mixed with antibiotics does not decrease efficacy against Cutibacterium acnes (formerly Propionibacterium acnes), in vitro study

Background

This study explored the in vitro efficacy of antibiotics mixed with calcium sulfate (ACS) against Cutibacterium acnes (C. acnes).

Methods

C. acnes isolates from orthopaedic infection sites were tested for antimicrobial susceptibility with ACS. Minimal inhibitory concentrations (MIC) were determined with a gradient diffusion method (Etest® strips).

Results

When tested with Etest®, all 22 isolates were susceptible to penicillin, ceftriaxone, vancomycin, and two were resistant to clindamycin (MICs of 4 and 8 mg/L). Penicillin and rifampin had the largest inhibition zone diameters.

Conclusions

Antibiotics retained activity against C. acnes when mixed with calcium sulfate.