Rifampin use in acute community-acquired meningitis in intensive care units: the French retrospective cohort ACAM-ICU study

Mathematical Model for Growth and Rifampicin-Dependent Killing Kinetics of Escherichia coli Cells

Antibiotic resistance is a global health threat. We urgently need better strategies to improve antibiotic use to combat antibiotic resistance. Currently, there are a limited number of antibiotics in the treatment repertoire of existing bacterial infections. Among them, rifampicin is a broad-spectrum antibiotic against various bacterial pathogens. However, during rifampicin exposure, the appearance of persisters or resisters decreases its efficacy. Hence, to benefit more from rifampicin, its current standard dosage might be reconsidered and explored using both computational tools and experimental or clinical studies. In this study, we present the mathematical relationship between the concentration of rifampicin and the growth and killing kinetics of Escherichia coli cells. We generated time-killing curves of E. coli cells in the presence of 4, 16, and 32 μg/mL rifampicin exposures. We specifically focused on the oscillations with decreasing amplitude over time in the growth and killing kinetics of rifampicin-exposed E. coli cells. We propose the solution form of a second-order linear differential equation for a damped oscillator to represent the mathematical relationship. We applied a nonlinear curve fitting solver to time-killing curve data to obtain the model parameters. The results show a high fitting accuracy.

Bioprospecting for the soil-derived actinobacteria and bioactive secondary metabolites on the Western Qinghai-Tibet Plateau

Introduction

The increase in incidence of multidrug-resistant bacteria and the inadequacy of new antimicrobial drugs have led to a widespread outbreak of bacterial antimicrobial resistance. To discover new antibiotics, biodiversity, and novelty of culturable actinobacteria dwelled in soil of the Western Qinghai-Tibet Plateau were investigated. By integrating antibacterial assay with omics tools, Amycolatopsis sp. A133, a rare actinobacterial strain and its secondary metabolites were further studied.

Method

Culture-dependent method was used to obtain actinobacterial strains from two soil samples collected from Ali region in Qinghai-Tibet Plateau. The cultural extractions of representative strains were assayed against "ESKAPE" pathogens by paper-disk diffusion method and the double fluorescent protein reporter "pDualrep2" system. An Amycolatopsis strain coded as A133 was prioritized and its secondary metabolites were further analyzed and annotated by omics tools including antiSMASH and GNPS (Global Natural Social Molecular Networking). The predicted rifamycin analogs produced by Amycolatopsis sp. A133 were isolated and identified by chromatographic separation, such as Sephadex LH-20 and HPLC, and spectral analysis, such as NMR and UPLC-HRESI-MS/MS, respectively.

Results

A total of 406 actinobacteria strains affiliated to 36 genera in 17 families of 9 orders were isolated. Out of 152 representative strains, 63 isolates exhibited antagonistic activity against at least one of the tested pathogens. Among them, 7 positive strains were identified by the "pDualrep2" system as either an inhibitor of protein translation or DNA biosynthesis. The cultural broth of Amycolatopsis sp. A133 exhibited a broader antimicrobial activity and can induce expression of TurboRFP. The secondary metabolites produced by strain A133 was annotated as rifamycins and zampanolides by antiSMASH and GNPS analysis. Five members of rifamycins, including rifamycin W, protorifamycin I, rifamycin W-M1, proansamycin B, and rifamycin S, were purified and identified. Rifamycin W-M1, was found as a new member of the naturally occurring rifamycin group of antibiotics.

Discussion

Assisted by omics tools, the successful and highly efficient discovery of rifamycins, a group of clinically used antibiotics from actinobacteria in Ali area encouraged us to devote more energy to explore new antibiotics from the soils on the Western Tibetan Plateau.

Longer than 2 hours to antibiotics is associated with doubling of mortality in a multinational community-acquired bacterial meningitis cohort

To optimally define the association between time to effective antibiotic therapy and clinical outcomes in adult community-acquired bacterial meningitis. A systematic review of the literature describing the association between time to antibiotics and death or neurological impairment due to adult community-acquired bacterial meningitis was performed. A retrospective cohort, multivariable and propensity-score based analyses were performed using individual patient clinical data from Australian, Danish and United Kingdom studies. Heterogeneity of published observational study designs precluded meta-analysis of aggregate data (I² = 90.1%, 95% CI 71.9–98.3%). Individual patient data on 659 subjects were made available for analysis. Multivariable analysis was performed on 180–362 propensity-score matched data. The risk of death (adjusted odds ratio, aOR) associated with treatment after two hours was 2.29 (95% CI 1.28–4.09) and increased substantially thereafter. Similarly, time to antibiotics of greater than three hours was associated with an increase in the occurrence of neurological impairment (aOR 1.79, 95% CI 1.03–3.14). Among patients with community-acquired bacterial meningitis, odds of mortality increase markedly when antibiotics are given later than two hours after presentation to the hospital.

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.

Potential Roles of Myeloid Differentiation Factor 2 on Neuroinflammation and Its Possible Interventions

Neuroinflammation is the primary response by immune cells in the nervous system to protect against infection. Chronic and uncontrolled neuroinflammation triggers neuronal injury and neuronal death resulting in a variety of neurodegenerative disorders. Therefore, fine tuning of the immune response in the nervous system is now extensively considered as a potential therapeutic intervention for those diseases. The immune cells of the nervous system express Toll-like receptor 4 (TLR4) together with myeloid differentiation factor 2 (MD-2) to protect against the pathogens. Over the last 10 years, antagonists targeting the functional domains of MD-2 have become attractive pharmacological intervention strategies in pre-clinical studies into neuroinflammation and its associated brain pathologies. This review aims to summarize and discuss the roles of TLR4-MD-2 signaling pathway activation in various models of neuroinflammation. This review article also highlights the studies reporting the effect of MD-2 antagonists on neuroinflammation in in vitro and in vivo studies.

Community-acquired acute bacterial meningitis in adults: a clinical update

BACKGROUND

Acute bacterial meningitis (ABM) in adults is associated with a mortality that may exceed 30%. Immunization programs have reduced the global burden; in the UK, declining incidence but persistently high mortality and morbidity mean that clinicians must remain vigilant.

SOURCES OF DATA

A systematic electronic literature search of PubMed was performed to identify all ABM literature published within the past 5 years.

AREAS OF AGREEMENT AND CONTROVERSY

Clinical features cannot reliably distinguish between ABM and other important infectious and non-infectious aetiologies. Prompt investigation and empirical treatment are imperative. Lumbar puncture (LP) and cerebrospinal fluid microscopy, biochemistry and culture remain the mainstay of diagnosis, but molecular techniques are increasingly useful. The 2016 UK joint specialist societies' guideline provides expert recommendations for the management of ABM, yet published data suggest clinical care delivered in the UK is frequently not adherent. Anxiety regarding risk of cerebral herniation following LP, unnecessary neuroimaging, underutilization of molecular diagnostics and suboptimal uptake of adjunctive corticosteroids compromise management.

GROWING POINTS

There is increasing recognition that current antibiotic regimens and adjunctive therapies alone are insufficient to reduce the mortality and morbidity associated with ABM.

AREAS TIMELY FOR DEVELOPING RESEARCH

Research should be focused on optimization of vaccines (e.g. pneumococcal conjugate vaccines with extended serotype coverage), targeting groups at risk for disease and reservoirs for transmission; improving adherence to management guidelines; development of new faster, more accurate diagnostic platforms (e.g. novel point-of-care molecular diagnostics); and development of new adjunctive therapies (aimed at the host-inflammatory response and bacterial virulence factors).

Rifampicin ameliorates lithium-pilocarpine-induced seizures, consequent hippocampal damage and memory deficit in rats: Impact on oxidative, inflammatory and apoptotic machineries

Epilepsy is one of the serious neurological sequelae of bacterial meningitis. Rifampicin, the well-known broad spectrum antibiotic, is clinically used for chemoprophylaxis of meningitis. Besides its antibiotic effects, rifampicin has been proven to be an effective neuroprotective candidate in various experimental models of neurological diseases. In addition, rifampicin was found to have promising antioxidant, anti-inflammatory and anti-apoptotic effects. Herein, we investigated the anticonvulsant effect of rifampicin at experimental meningitis dose (20 mg/kg, i.p.) using lithium-pilocarpine model of status epilepticus (SE) in rats. Additionally, we studied the effect of rifampicin on seizure induced histopathological, neurochemical and behavioral abnormalities. Our study showed that rifampicin pretreatment attenuated seizure activity and the resulting hippocampal insults marked by hematoxylin and eosin. Markers of oxidative stress, neuroinflammation and apoptosis were evaluated, in the hippocampus, 24 h after SE induction. We found that rifampicin pretreatment suppressed oxidative stress as indicated by normalized malondialdehyde and glutathione levels. Rifampicin pretreatment attenuated SE-induced neuroinflammation and decreased the hippocampal expression of interleukin-1β, tumor necrosis factor-α, nuclear factor kappa-B, and cyclooxygenase-2. Moreover, rifampicin mitigated SE-induced neuronal apoptosis as indicated by fewer positive cytochrome c immunostained cells and lower caspase-3 activity in the hippocampus. Furthermore, Morris water maze testing at 7 days after SE induction showed that rifampicin pretreatment can improve cognitive dysfunction. Therefore, rifampicin, currently used in the management of meningitis, has a potential additional advantage of ameliorating its epileptic sequelae.

Global etiology of bacterial meningitis: A systematic review and meta-analysis

Bacterial meningitis is a global public health concern, with several responsible etiologic agents that vary by age group and geographical area. The aim of this systematic review and meta-analysis was to assess the etiology of bacterial meningitis in different age groups across global regions. PubMed and EMBASE were systematically searched for English language studies on bacterial meningitis, limited to articles published in the last five years. The methodological quality of the studies was assessed using a customized scoring system. Meta-analyses were conducted to determine the frequency (percentages) of seven bacterial types known to cause meningitis: Escherichia coli, Haemophilus influenzae, Neisseria meningitidis, Streptococcus pneumoniae, group B Streptococcus agalactiae, Staphylococcus aureus, and Listeria monocytogenes, with results being stratified by six geographical regions as determined by the World Health Organization, and seven age groups. Of the 3227 studies retrieved, 56 were eligible for the final analysis. In all age groups, S. pneumoniae and N. meningitidis were the predominant pathogens in all regions, accounting for 25.1-41.2% and 9.1-36.2% of bacterial meningitis cases, respectively. S. pneumoniae infection was the most common cause of bacterial meningitis in the 'all children' group, ranging from 22.5% (Europe) to 41.1% (Africa), and in all adults ranging from 9.6% (Western Pacific) to 75.2% (Africa). E. coli and S. pneumoniae were the most common pathogens that caused bacterial meningitis in neonates in Africa (17.7% and 20.4%, respectively). N. meningitidis was the most common in children aged ±1-5 years in Europe (47.0%). Due to paucity of data, meta-analyses could not be performed in all age groups for all regions. A clear difference in the weighted frequency of bacterial meningitis cases caused by the different etiological agents was observed between age groups and between geographic regions. These findings may facilitate bacterial meningitis prevention and treatment strategies.

Role of rifampin for the treatment of bacterial infections other than mycobacteriosis

OBJECTIVES

Rifampin was initially approved for the treatment of tuberculosis. Because of its low toxicity, broad-spectrum activity, and good bioavailability, rifampin is now commonly administered as combination antimicrobial therapy for the treatment of various infections caused by organisms other than mycobacteria. This review summarizes the most recent clinical studies on the use of rifampin combinations for treating four common non-mycobacterial infections: acute bacterial meningitis, infective endocarditis and bacteraemia, pneumonia, and biofilm-related infections.

METHODS

We performed a literature search of clinical studies published in English from January 2005 to June 2016 using the PubMed database with the search terms "rifampin" with "meningitis" or "infective endocarditis and bacteraemia" or "pneumonia" or "prosthetic joint infections.

RESULTS

Current evidence to support a rifampin combination therapy as a treatment for non-mycobacterial infections was largely based on in vitro/in vivo studies and non-comparable retrospective case series. Additionally, controlled clinical trials that directly compared outcomes resulting from rifampin treatment versus treatment without rifampin were limited.

CONCLUSIONS

Rifampin combination therapy appears promising for the treatment of non-mycobacterial infections. However, further definitive clinical trials are necessary to validate its use because the risk of adverse drug-drug interactions and of the emergence of rifampin resistance during treatment may outweigh the potential benefits.

Streptococcus pneumoniae and lytic antibiotic therapy: are we adding insult to injury during invasive pneumococcal disease and sepsis?

Streptococcus pneumoniae (S. pneumoniae), otherwise known as 'the pneumococcus', is a fascinating microbe that continues to pose a significant problem to public health. Currently there are no specific National Institute for Clinical Excellence (NICE) or British Thoracic Society (BTS) clinical guidelines referring to the treatment of invasive pneumococcal infection. NICE clinical guidelines suggest the use of lytic β-lactam antibiotic regimens for the management of community-acquired pneumonia and bacterial meningitis; infections for which S. pneumoniae is a likely causative organism. Lytic antibiotics have been shown to increase the release of pneumolysin (the highly inflammatory and damaging toxin of the pneumococcus), thus theoretically increasing host damage, which may lead to a decline of clinical outcomes in vulnerable patients. In light of this information, should the use of non-lytic antibiotics, such as quinolones, rifamycins and macrolides, be considered for the treatment of invasive pneumococcal disease?