Quinupristin/dalfopristin attenuates the inflammatory response and reduces the concentration of neuron-specific enolase in the cerebrospinal fluid of rabbits with experimental Streptococcus pneumoniae meningitis

A Review: Antimicrobial Therapy for Human Pythiosis

Human pythiosis is associated with poor prognosis with significant mortality caused by Pythium insidiosum. Antimicrobials’ in vitro and in vivo results against P. insidiosum are inconsistent. Although antimicrobials are clinically useful, they are not likely to achieve therapeutic success alone without surgery and immunotherapy. New therapeutic options are therefore needed. This non-exhaustive review discusses the rationale antimicrobial therapy, minimum inhibitory concentrations, and efficacy of antibacterial and antifungal agents against P. insidiosum. This review further provides insight into the immunomodulating effects of antimicrobials that can enhance the immune response to infections. Current data support using antimicrobial combination therapy for the pharmacotherapeutic management of human pythiosis. Also, the success or failure of antimicrobial treatment in human pythiosis might depend on the immunomodulatory effects of drugs. The repurposing of existing drugs is a safe strategy for anti-P. insidiosum drug discovery. To improve patient outcomes in pythiosis, we suggest further research and a deeper understanding of P. insidiosum virulence factors, host immune response, and host immune system modification by antimicrobials.

Inadequate Cerebrospinal Fluid Concentrations of Available Salvage Agents Further Impedes the Optimal Treatment of Multidrug-Resistant Enterococcus faecium Meningitis and Bacteremia

BACKGROUND

Vancomycin-resistant Enterococcus faecium (VRE) in particular has evolved as an important cause of hospital acquired infection, especially in immunocompromised hosts.

METHODS

We present a complex case of a patient with relapsed acute myeloid leukemia who underwent allogenic hematopoietic stem cell transplantation complicated by persistent VRE bacteremia and meningitis. To optimize therapy, various blood and cerebrospinal fluid (CSF) samples were sent to a research laboratory for extensive susceptibility testing, pharmacokinetic analyses, and time-kill experiments.

RESULTS

In vitro testing revealed resistance to all first-line treatment options and CSF sampling demonstrated sub-optimal central nervous system concentrations achieved by each antimicrobial agent administered in relation to their respective MIC value. Time-kill analyses at observed CSF concentrations confirmed the lack of bactericidal activity despite use of a four-drug combination regimen.

CONCLUSIONS

This work is the first to report CSF concentrations of oritavancin and tedizolid in humans and adds to the limited data regarding in vitro susceptibility of new antimicrobial agents such as eravacycline, omadacycline, and lefamulin against VRE. Our study provides new insights into various aspects of treatment of extensively drug-resistant Enterococcus faecium meningitis and bacteremia and supports the continued pursuit of precision medicine for these challenging cases.

Evaluation of neurofilament light chain in the cerebrospinal fluid and blood as a biomarker for neuronal damage in experimental pneumococcal meningitis

Background

Pneumococcal meningitis (PM) remains a global public health concern and affects all age groups. If acquired during infancy or childhood, permanent neurofunctional deficits including cognitive impairment, cerebral palsy, and secondary epilepsy are typical sequelae of neuronal injury. Determination of patients at risk for the development of brain injury and subsequent neurofunctional sequelae could help to identify patients for focused management. Neurofilament light chain (NfL) is an axonal cytoskeletal protein released upon neuronal injury into the cerebrospinal fluid (CSF) and blood. As little is known about the course of neurofilament release in the course of PM, we measured CSF and serum NfL levels longitudinally in experimental PM (ePM).

Methods

Eleven-day-old infant Wistar rats were infected intracisternally with Streptococcus pneumoniae and treated with ceftriaxone. At 18 and 42 h post-infection (hpi), the blood and CSF were sampled for NfL measurements by a single molecule array technology. Inflammatory cytokines and MMP-9 in CSF were quantified by magnetic bead multiplex assay (Luminex®) and by gel zymography, respectively.

Results

In ePM, CSF and serum NfL levels started to increase at 18 hpi and were 26- and 3.5-fold increased, respectively, compared to mock-infected animals at 42 hpi (p < 0.0001). CSF and serum NfL correlated at 18 hpi (p < 0.05, r = 0.4716) and 42 hpi (p < 0.0001, r = 0.8179). Both CSF and serum NfL at 42 hpi strongly correlated with CSF levels of IL-1β, TNF-α, and IL-6 and of MMP-9 depending on their individual kinetics.

Conclusion

Current results demonstrate that during the peak inflammatory phase of ePM, NfL levels in CSF and serum are the highest among CNS disease models studied so far. Given the strong correlation of CSF versus serum NfL, and its CNS-specific signal character, longitudinal measurements to monitor the course of PM could be performed based on blood sample tests, i.e., without the need of repetitive spinal taps. We conclude that NfL in the serum should be evaluated as a biomarker in PM.

RIFAMPICIN: an antibiotic with brain protective function

Besides its well known antibiotic activity rifampicin exerts multiple brain protective functions in acute cerebral ischemia and chronic neurodegeneration. The present mini-review gives an update of the unique activity of rifampicin in different diseases including Parkinson's disease, meningitis, stroke, Alzheimer's disease and optic nerve injury.

Pathogenesis and pathophysiology of pneumococcal meningitis

Pneumococcal meningitis continues to be associated with high rates of mortality and long-term neurological sequelae. The most common route of infection starts by nasopharyngeal colonization by Streptococcus pneumoniae, which must avoid mucosal entrapment and evade the host immune system after local activation. During invasive disease, pneumococcal epithelial adhesion is followed by bloodstream invasion and activation of the complement and coagulation systems. The release of inflammatory mediators facilitates pneumococcal crossing of the blood-brain barrier into the brain, where the bacteria multiply freely and trigger activation of circulating antigen-presenting cells and resident microglial cells. The resulting massive inflammation leads to further neutrophil recruitment and inflammation, resulting in the well-known features of bacterial meningitis, including cerebrospinal fluid pleocytosis, cochlear damage, cerebral edema, hydrocephalus, and cerebrovascular complications. Experimental animal models continue to further our understanding of the pathophysiology of pneumococcal meningitis and provide the platform for the development of new adjuvant treatments and antimicrobial therapy. This review discusses the most recent views on the pathophysiology of pneumococcal meningitis, as well as potential targets for (adjunctive) therapy.

[Antibiotic management of presumptive bacterial meningitis in adults (rational, methods, course, and follow-up)]

The annual incidence of community acquired meningitis ranges between 0.6 and four per 100,000 adults in industrialized countries. The most common causative bacteria are Streptococcus pneumoniae, Neisseria meningitidis, Listeria monocytogenes. The emergence of resistance to antibiotics, especially for S. pneumoniae, could explain the clinical failure of third generation cephalosporins used to treat adults with S. pneumoniae meningitis. The present therapeutic suggestions are more based on the extrapolation of an experimental model than on relevant clinical trials.

Pharmacologic options for CNS infections caused by resistant Gram-positive organisms

Infectious disease continues to evolve, presenting new and challenging clinical situations for practitioners. Specific to device-related and neurosurgical-related CNS infections, Gram-positive organisms are of growing concern. Current Infection Disease Society of America guidelines for the treatment of CNS infections offer little direction after conventional therapy, consisting of vancomycin, has failed or the patient has demonstrated intolerance. A review of literature evaluating alternative therapies, specifically linezolid, quinupristin/dalfopristin, daptomycin and tigecycline, will be presented. Interpretations of these data are offered followed by a brief presentation of future therapies, including ortavancin, telavancin, dalbavancin, ceftobiprole and iclaprim, all of which possess potent Gram-positive activity.

Gram-positive resistance: pathogens, implications, and treatment options: insights from the Society of Infectious Diseases Pharmacists

Despite the advent of new antibiotics, resistance in gram-positive pathogens, including staphylococci and enterococci, continues to increase. This is evident with the recent emergence of vancomycin-resistant Staphylococcus aureus . Newer treatment agents are available, including quinupristin-dalfopristin, linezolid, and daptomycin. In addition, investigational agents are being explored. Clinical trials have been conducted for various infections, such as skin and skin structure infections, pneumonia, and bloodstream infections. Antibacterial activity, site of infection, and potential for adverse effects must be taken into account when making decisions regarding therapy.

Clindamycin is neuroprotective in experimental Streptococcus pneumoniae meningitis compared with ceftriaxone

In animal models of Streptococcus pneumoniae meningitis, rifampin is neuroprotective in comparison to ceftriaxone. So far it is not clear whether this can be generalized for other protein synthesis-inhibiting antimicrobial agents. We examined the effects of the bactericidal protein synthesis-inhibiting clindamycin (n = 12) on the release of proinflammatory bacterial components, the formation of neurotoxic compounds and neuronal injury compared with the standard therapy with ceftriaxone (n = 12) in a rabbit model of pneumococcal meningitis. Analysis of the CSF and histological evaluation were combined with microdialysis from the hippocampal formation and the neocortex. Compared with ceftriaxone, clindamycin reduced the release of lipoteichoic acids from the bacteria (p = 0.004) into the CSF and the CSF leucocyte count (p = 0.011). This led to lower extracellular concentrations of hydroxyl radicals (p = 0.034) and glutamate (p = 0.016) in the hippocampal formation and a subsequent reduction of extracellular glycerol levels (p = 0.018) and neuronal apoptosis in the dentate gyrus (p = 0.008). The present data document beneficial effects of clindamycin compared with ceftriaxone on various parameters linked with the pathophysiology of pneumococcal meningitis and development of neuronal injury. This study suggests neuroprotection to be a group effect of bactericidal protein synthesis-inhibiting antimicrobial agents compared with the standard therapy with beta-lactam antibiotics in meningitis.

Clinical pharmacokinetics of quinupristin/dalfopristin

Quinupristin/dalfopristin is a streptogramin antibacterial with a wide spectrum of Gram-positive antibacterial activity. The drug has minimal oral absorption and is administered intravenously as a fixed 30 : 70 ratio of quinupristin to dalfopristin. A linear relationship has been observed between the dose administered and maximum plasma concentrations. Single-dose administration of 7.5 mg/kg produced a maximal plasma concentration of 2.3-2.7 mg/L for quinupristin and 6.1-8.2 mg/L for dalfopristin. The area under the concentration-time curve (AUC) obtained with the same dose was 2.7-3.3 and 6.5-7.7 mg. h/L for quinupristin and dalfopristin, respectively. Repeated administration results in 13-21% increases in maximum plasma concentrations and 21-26% increases in AUC for both quinupristin and dalfopristin. Quinupristin and dalfopristin exhibit steady-state volumes of distribution of 0.46-0.54 and 0.24-0.30 L/kg, respectively. Quinupristin exhibits higher protein binding (55-78%) than dalfopristin (11-26%), though both entities distribute well into tissues. Concentrations exceeding those in blood have been reported for the kidney, liver, spleen, salivary glands and white blood cells of primates. Extravascular penetration, as measured in blister fluid, is 40-80%. Both quinupristin and dalfopristin are extensively metabolised via nonenzymatic reactions. Quinupristin is conjugated to form two active compounds, a cysteine moiety and a glutathione moiety. Dalfopristin is hydrolysed to the active metabolite pristinamycin IIA. The metabolites exert antibacterial activity similar to that of the parent compounds. Quinupristin/dalfopristin is excreted primarily in the faeces (75-77%), with lesser renal excretion (15-19%). The elimination half-lives of quinupristin and dalfopristin are similar, and are 0.7-1.3 hours after single doses. The metabolites have slightly longer half-lives, ranging from 1.2 to 1.8 hours. With repeated doses, plasma clearance of quinupristin and dalfopristin is reduced by approximately 20% compared with single doses, resulting in clearances of 0.7-0.8 L/h/kg. Saturable protein binding has been hypothesised as a causative mechanism. Quinupristin/dalfopristin is an inhibitor of cytochrome P450 3A4, resulting in multiple drug interactions. Ciclosporin AUC increased by 5-222% when coadministered with quinupristin/dalfopristin. Careful monitoring of patients receiving drugs that are substrates of cytochrome P450 3A4 is suggested.Quinupristin/dalfopristin is administered at 7.5 mg/kg every 8-12 hours, depending upon the severity of infection. The pharmacodynamic parameter linked with antibacterial activity for quinupristin/dalfopristin appears to be the ratio of AUC to the minimal inhibitory concentration. The additional activity of a prolonged post-antibiotic effect may also be important for efficacy.

New therapies for pneumococcal meningitis

The treatment of pneumococcal meningitis remains a major challenge, as reflected by the continued high morbidity and case fatality of the disease. The worldwide increase of penicillin-resistant pneumococci and more recently cephalosporin- and vancomycin-tolerant pneumococci has jeopardised the efficacy of standard treatments based on extended spectrum cephalosporins alone or in combination with vancomycin. This review provides a summary of newly developed antibiotics tested in the rabbit meningitis model. In particular, newer beta-lactam monotherapies (cefepime, meropenem, ertapenem), recently developed quinolones (garenoxacin, gemifloxacin, gatifloxacin, moxifloxacin) and a lipopeptide antibiotic (daptomycin) are discussed. A special emphasis is placed on the potential role of combination treatments with some of the new compounds, which are of interest based on the background of increasing resistance problems due to their often synergistic activity in the rabbit model of pneumococcal meningitis.

Modulation of release of proinflammatory bacterial compounds by antibacterials: potential impact on course of inflammation and outcome in sepsis and meningitis

Several bacterial components (endotoxin, teichoic and lipoteichoic acids, peptidoglycan, DNA, and others) can induce or enhance inflammation and may be directly toxic for eukaryotic cells. Bactericidal antibiotics which inhibit bacterial protein synthesis release smaller quantities of proinflammatory/toxic bacterial compounds than B-lactams and other cell wall-active drugs. Among the B-lactams, compounds binding to penicillin-binding protein 2 (PBP-2) release smaller amounts of bacterial substances than antibacterials inhibiting PBP-3. Generally, high antibiotic concentrations (more than 10 times the MIC) induce the release of fewer bacterial proinflammatory/toxic compounds than concentrations close to the MIC. In several in vitro and in vivo systems, bacteria treated with protein synthesis inhibitors or B-lactams inhibiting PBP-2 induce less inflammation than bacteria treated with PBP-3-active B-lactams. In mouse models of Escherichia coli peritonitis sepsis and of Streptococcus pneumoniae meningitis, lower release of proinflammatory bacterial compounds was associated with reduced mortality. In conclusion, sufficient evidence for the validity of the concept of modulating the release of proinflammatory bacterial compounds by antibacterials has been accumulated in vitro and in animal experiments to justify clinical trials in sepsis and meningitis. A properly conducted study addressing the potential benefit of bacterial protein synthesis inhibitors versus B-lactam antibiotics will require both strict selection and inclusion of a large number of patients. The benefit of this approach should be greatest in patients with a high bacterial load.

Successful treatment of vancomycin-resistant enterococcus meningitis with linezolid: Case report and review of the literature

OBJECTIVE

To describe the successful treatment of a case of vancomycin-resistant enterococcus meningitis with linezolid.

DESIGN

Case report and review of the literature.

PATIENTS

The patient is a 35-yr-old man who suffered a cerebellar hemorrhage after embolization of a cerebellar arteriovenous malformation. The patient underwent ventriculostomy drainage and craniectomy. The patient was on broad-spectrum antibiotics for pneumonia including vancomycin. The patient remained febrile and grew vancomycin-resistant Enterococcus faecium from the cerebrospinal fluid.

INTERVENTIONS

The patient was treated with intravenous chloramphenicol without success. On postoperative day 16, the patient was begun on intravenous linezolid.

MAIN RESULTS

The patient received 4 wks of intravenous linezolid with complete eradication of the meningitis.

CONCLUSIONS

Intravenous linezolid appears to be a safe and effective therapy for vancomycin-resistant enterococcus meningitis.

Effect of deficiency of tumor necrosis factor alpha or both of its receptors on Streptococcus pneumoniae central nervous system infection and peritonitis

Tumor necrosis factor alpha (TNF-alpha) and TNF-beta are key mediators in bacterial inflammation. We therefore examined the role of TNF-alpha and its two receptors in murine pneumococcal central nervous system infection. TNF-alpha knockout mice and age- and sex-matched controls and TNF receptor (p55 and p75)-deficient mice and heterozygous littermates were infected intracerebrally with a Streptococcus pneumoniae type 3 strain. Mice were monitored until death or were killed 36 h after infection. Bacterial titers in blood, spleen, and brain homogenates were determined. Leukocyte infiltration and neuronal damage were assessed by histological scores. TNF-alpha-deficient mice died earlier than the controls after intracerebral infection although overall survival was similar. TNF-alpha deficiency did not inhibit leukocyte recruitment into the subarachnoid space and did not lead to an increased density of bacteria in brain homogenates. However, it caused a substantial rise of the concentration of S. pneumoniae cells in blood and spleen. Spleen bacterial titers were also increased in p55- and p75-deficient mice. TNF receptor-deficient mice showed decreased meningeal inflammation. Neuronal damage was not affected by either TNF-alpha or TNF receptor deficiency. In a murine model of pneumococcal peritonitis, 10(2) CFU of S. pneumoniae produced fatal peritonitis in TNF-alpha-deficient, but not wild-type, mice. Early leukocyte influx into the peritoneum was impaired in TNF-alpha-deficient mice. The lack of TNF-alpha or its receptors renders mice more susceptible to S. pneumoniae infections.

Activity of LY333328 in experimental meningitis caused by a Streptococcus pneumoniae strain susceptible to penicillin

In a rabbit model of Streptococcus pneumoniae meningitis single doses of 10 and 2.5 mg of the glycopeptide LY333328 per kg of body weight reduced bacterial titers in cerebrospinal fluid (CSF) almost as rapidly as ceftriaxone at 10 mg/kg/h (changes in log CFU, -0.29 +/- 0.21 and -0.26 +/- 0.22 versus -0.34 +/- 0.15/ml/h). A dose of 1 mg/kg was bacteriostatic (change in log CFU, 0.01 +/- 0.11/ml/h). In two animals receiving LY333328 at a dose of 40 mg/kg the bacterial titers were reduced by 0.54 and 0.51 log CFU/ml/h. The penetration of CSF by LY333328 was 1 to 5%. The concentrations of lipoteichoic and teichoic acids in CSF and neuronal damage were similar in ceftriaxone- and LY333328-treated animals.

Quinupristin-dalfopristin: an overview

Synercid (RP 59500), the first injectable streptogramin antibiotic, is composed of two semisynthetic pristinamycin derivatives, quinupristin and dalfopristin. Individually, each component has bacteriostatic activity against staphylococci and streptococci, but together, the agents exhibit synergy, leading to bactericidal activity. The combination drug, however, is bacteriostatic against Enterococcus faecium and has poor activity against Enterococcus faecalis. Despite a short half-life, an extended postantibiotic effect allows the agent to be dosed every 8-12 hours. Both drugs are largely hepatically metabolized and excreted in bile. Although not metabolized by cytochrome P450 3A4, quinupristin-dalfopristin can inhibit agents that are metabolized through this pathway. Dosage adjustments may be necessary in patients with hepatic dysfunction. Alterations in renal function have minimal effects on the agent's pharmacokinetics. Adverse events include arthralgia, myalgias, and infusion-related pain. Based on available data, quinupristin-dalfopristin appears to have a role in treating severely ill patients with infections due to multiresistant gram-positive pathogens.

Quinupristin/dalfopristin: a review of its use in the management of serious gram-positive infections

Quinupristin/dalfopristin is the first parenteral streptogramin antibacterial agent, and is a 30:70 (w/w) ratio of 2 semisynthetic pristinamycin derivatives. The combination has inhibitory activity against a broad range of gram-positive bacteria including methicillin-resistant staphylococci, vancomycin-resistant Enterococcus faecium (VREF), drug-resistant Streptococcus pneumoniae, other streptococci, Clostridium perfringens and Peptostreptococcus spp. The combination also has good activity against selected gram-negative respiratory tract pathogens including Moraxella catarrhalis, Legioniella pneumophila and Mycoplasma pneumoniae. Quinupristin/dalfopristin has poor activity against E. faecalis. The combination is bactericidal against staphylococci and streptococci, although constitutive erythromycin resistance can affect its activity. As for many other agents, quinupristin/dalfopristin is generally bacteriostatic against E. faecium. In patients with methicillin-resistant S. aureus (MRSA) or VREF infections participating in prospective emergency-use trials, quinupristin/dalfopristin 7.5 mg/kg every 8 or 12 hours achieved clinical or bacteriological success in > or =64% of patients. Emergence of resistance to quinupristin/dalfopristin was uncommon (4% of patients) in those with VREF infections. Quinupristin/dalfopristin 7.5 mg/kg 8- or 12-hourly also achieved similar clinical success rates to comparator agents in patients with presumed gram-positive complicated skin and skin structure infections or nosocomial pneumonia (administered in combination with aztreoman) in 3 large multicentre randomised trials. Systemic adverse events associated with quinupristin/dalfopristin include gastrointestinal events (nausea, vomiting and diarrhoea), rash and pruritus. Myalgias and arthralgias also occur at an overall incidence of 1.3%, although higher rates (2.5 to 31%) have been reported in patients with multiple comorbidities. Venous events are common if the drug is administered via a peripheral line; however, several management options (e.g. use of central venous access, increased infusion volume) may help to minimise their occurrence. Hyperbilirubinaemia has been documented in 3.1% of quinupristin/dalfopristin recipients versus 1.3% of recipients of comparator agents. Quinupristin/dalfopristin inhibits cytochrome P450 3A4 and therefore has the potential to increase the plasma concentrations of substrates of this enzyme.

CONCLUSIONS

Quinupristin/dalfopristin, the first parenteral streptogramin, offers a unique spectrum of activity against multidrug-resistant gram-positive bacteria. In serious gram-positive infections for which there are other treatment options available, the spectrum of activity and efficacy of quinupristin/ dalfopristin should be weighed against its tolerability and drug interaction profile. However, in VREF or unresponsive MRSA infections, where few proven treatment options exist, quinupristin/dalfopristin should be considered as a treatment of choice for these seriously ill patients.

The effect of the pneumococcal toxin, pneumolysin on brain ependymal cilia

Densely ciliated ependymal cells cover the ventricular surface of the brain and cerebral aqueducts separating cerebrospinal fluid, which is infected in meningitis, from neuronal tissue. We have established an ex vivo model that allows measurement of ependymal ciliary beat frequency, using high-speed video analysis, during incubation with bacterial toxins. Ciliated ependyma, from Wistar rats, was exposed to the pneumococcal toxin, pneumolysin, and a mutant form with markedly reduced cytotoxic activity (;0.1%). Wild-type pneumolysin (1500 HU/ml and 150 HU/ml: 10 and 1 microg/ml) caused rapid ciliary stasis (30-150 s), sloughing of cilia and cytoplasmic extrusion. Ciliary slowing before stasis was seen at 15 HU/ml (0.1 microg/ml); however, no effect on ciliary beat frequency was seen at lower concentrations (1.5 HU/ml and 0.15 HU/ml: 0.01 and 0.001 microg/ml). Mutant pneumolysin, 99.9% deficient in haemolytic activity, caused rapid ciliary stasis at 10 microg/ml but no effect was seen at lower concentrations (1-0.1 microg/ml). Pneumolysin, at levels which may be produced during severe pneumococcal meningitis, may cause rapid ependymal ciliary stasis.

Lower lipoteichoic and teichoic acid CSF concentrations during treatment of pneumococcal meningitis with non-bacteriolytic antibiotics than with ceftriaxone

In the rabbit model of Streptococcus pneumoniae meningitis, treatment with rifabutin, quinupristin-dalfopristin, moxifloxacin and trovafloxacin led to smaller increases of the CSF concentrations of the pro-inflammatory cell wall components lipoteichoic and teichoic acids (LTA and TA) than did treatment with ceftriaxone. Low doses of moxifloxacin were associated with higher LTA and TA concentrations in CSF than were high doses.