Meropenem prevents levofloxacin-induced resistance in penicillin-resistant pneumococci and acts synergistically with levofloxacin in experimental meningitis

Spider chart, greenness and whiteness assessment of experimentally designed multivariate models for simultaneous determination of three drugs used as a combinatory antibiotic regimen in critical care units: Comparative study

In this study, five earth-friendly spectrophotometric methods using multivariate techniques were developed to analyze levofloxacin, linezolid, and meropenem, which are utilized in critical care units as combination therapies. These techniques were used to determine the mentioned medications in laboratory-prepared mixtures, pharmaceutical products and spiked human plasma that had not been separated before handling. These methods were named classical least squares (CLS), principal component regression (PCR), partial least squares (PLS), genetic algorithm partial least squares (GA-PLS), and artificial neural network (ANN). The methods used a five-level, three-factor experimental design to make different concentrations of the antibiotics mentioned (based on how much of them are found in the plasma of critical care patients and their linearity ranges). The approaches used for levofloxacin, linezolid, and meropenem were in the ranges of 3-15, 8-20, and 5-25 µg/mL, respectively. Several analytical tools were used to test the proposed methods' performance. These included the root mean square error of prediction, the root mean square error of cross-validation, percentage recoveries, standard deviations, and correlation coefficients. The outcome was highly satisfactory. The study found that the root mean square errors of prediction for levofloxacin were 0.090, 0.079, 0.065, 0.027, and 0.001 for the CLS, PCR, PLS, GA-PLS, and ANN models, respectively. The corresponding values for linezolid were 0.127, 0.122, 0.108, 0.05, and 0.114, respectively. For meropenem, the values were 0.230, 0.222, 0.179, 0.097, and 0.099 for the same models, respectively. These results indicate that the developed models were highly accurate and precise. This study compared the efficiency of artificial neural networks and classical chemometric models in enhancing spectral data selectivity for quickly identifying three antimicrobials. The results from these five models were subjected to statistical analysis and compared with each other and with the previously published ones. Finally, the whiteness of the methods was assessed by the recently published white analytical chemistry (WAC) RGB 12, and the greenness of the proposed methods was assessed using AGREE, GAPI, NEMI, Raynie and Driver, and eco-scale, which showed that the suggested approaches had the least negative environmental impact. Furthermore, to demonstrate solvent sustainability, a greenness index using a spider chart methodology was employed.

Addition of daptomycin to levofloxacin increased the efficacy of levofloxacin monotherapy against a methicillin-susceptible Staphylococcus aureus strain in experimental meningitis and prevented development of resistance in vitro

Introduction. Daptomycin and levofloxacin were tested as monotherapies and in combination against the antibiotic-susceptible S. aureus strain MSSA 1112 in a rabbit meningitis model and the effect of the combination on induction of resistance was determined in vitro.

Hypothesis/Gap Statement. Treatment combination might be more efficacious than the monotherapies regarding antibacterial efficacy in vivo and development of resistance.

Aim. To demonstrate a synergy of the antibiotic combination daptomycin and levofloxacin in experimental meningitis, and also its ability to reduce the emergence of resistance against the antibiotics in vitro.

Methodology. Changes of the susceptibility to fluoroquinolones and daptomycin were determined by the measurement of the MIC and mutations were detected by whole genome sequence comparison of the mutants with the parent strain MSSA 1112. Meningitis was induced by intracisternal inoculation of 105 c.f.u. (colony forming unit) of MSSA 1112 and treatment was started 10 h later by injection of daptomycin (15 mg kg−1) and levofloxacin (10 mg kg−1) standard doses. Cerebrospinal fluid (CSF) samples were repeatedly collected during therapy in order to determine killing rates and results of bactericidal activity were expressed in Δlog10c.f.u. ml-1 over 8 h.

Results. The combination of daptomycin with levofloxacin was significantly (P<0.001) superior to levofloxacin monotherapy and increased the antibacterial activity of daptomycin. In vitro, MSSA 1112 was cycled over 6 days with either increasing concentrations of levofloxacin or daptomycin or with a combination of levofloxacin with half of the MIC of daptomycin or daptomycin with half of the MIC of levofloxacin leading to mutations in target genes as identified by whole genome sequence analysis. Addition of low concentration of daptomycin (0.25 mg l−1) reduced levofloxacin-induced resistance in vitro. Addition of levofloxacin in low concentration (0.125 mg l−1) did not influence daptomycin-induced resistance.

Conclusion. These findings highlight the lack of reciprocal interference of antibiotics in combination with regard to the development of resistance.

Preclinical models to optimize treatment of tuberculous meningitis - A systematic review

Tuberculous meningitis (TBM) is the most devastating form of TB, resulting in death or neurological disability in up to 50% of patients affected. Treatment is similar to that of pulmonary TB, despite poor cerebrospinal fluid (CSF) penetration of the cornerstone anti-TB drug rifampicin. Considering TBM pathology, it is critical that optimal drug concentrations are reached in the meninges, brain and/or the surrounding CSF. These type of data are difficult to collect in TBM patients. This review aims to identify and describe a preclinical model representative for human TBM which can provide the indispensable data needed for future pharmacological characterization and prioritization of new TBM regimens in the clinical setting. We reviewed existing literature on treatment of TBM in preclinical models: only eight articles, all animal studies, could be identified. None of the animal models completely recapitulated human disease and in most of the animal studies key pharmacokinetic data were missing, making the comparison with human exposure and CNS distribution, and the study of pharmacokinetic-pharmacodynamic relationships impossible. Another 18 articles were identified using other bacteria to induce meningitis with treatment including anti-TB drugs (predominantly rifampicin, moxifloxacin and levofloxacin). Of these articles the pharmacokinetics, i.e. plasma exposure and CSF:plasma ratios, of TB drugs in meningitis could be evaluated. Exposures (except for levofloxacin) agreed with human exposures and also most CSF:plasma ratios agreed with ratios in humans. Considering the lack of an ideal preclinical pharmacological TBM model, we suggest a combination of 1. basic physicochemical drug data combined with 2. in vitro pharmacokinetic and efficacy data, 3. an animal model with adequate pharmacokinetic sampling, microdialysis or imaging of drug distribution, all as a base for 4. physiologically based pharmacokinetic (PBPK) modelling to predict response to TB drugs in treatment of TBM.

Treatment and prevention strategies to combat pediatric pneumococcal meningitis

Pneumococcal meningitis is a severe, life-threatening infection of the nervous system affecting infants, children and adults alike. The incidence of pneumococcal meningitis in infants and children less than 2 years of age in Europe is approximately 10 out of 100,000 per year, rising to approximately 148 out of 100,000 per year in Gambian infants. The use of highly sensitive tests such as PCR may increase the likelihood of detecting the infection by 20% or more. Epidemics of serotype 1 pneumococcal meningitis in northern Ghana, have had many of the characteristics of meningococcal meningitis epidemics. Neurologic sequelae may occur in 28-63% of cases, and serotype 3 is associated with a 2.54 relative risk of death. The pathogenic process can be divided into invasion, inflammatory pathways, bacterial toxicity and damage; pneumolysin being particularly associated with apoptosis. In the future, neuroprotection may be achieved, targeting this process at all these levels. Therapeutic guidelines have been published by the Infectious Diseases Society of America. Standard empiric therapy, in those aged greater than or equal to 1 month, is a third-generation cephalosporin plus vancomycin. There is insufficient evidence relating to the use or otherwise of corticosteroids in pneumococcal meningitis to make a firm recommendation. The advent of a pneumococcal conjugate vaccine is the most powerful tool available for the prevention of pneumococcal meningitis in all parts of the world.

Atypical metronidazole-induced encephalopathy in anaerobic brain abscess

Metronidazole-induced encephalopathy is a very rare complication of the long standing use of metronidazole. The encephalopathy is bilateral and symmetric in nature. We report on the magnetic resonance imaging (MRI) and clinical course of metronidazole-induced encephalopathy in a 60-year-old female with a persistent anaerobic brain abscess after draining of the abscess. After 3 months of metronidazole administration, the patient complained of dysarthria, tingling sense of all extremities, and left hemiparesis. MRI revealed symmetric hyperintensity lesions in medulla, pons, dentate nuclei of cerebellum, and splenium of corpus callosum, all of which represent typical findings of metronidazole-induced encephalopathy. In addition, asymmetric lesions in midbrain, thalamus, putamen and cerebral subcortical white matter were noted. The patient recovered after discontinuation of metronidazole and the remaining abscess was successfully treated with meropenem and levofloxacine.

Carbapenems: past, present, and future

In this review, we summarize the current "state of the art" of carbapenem antibiotics and their role in our antimicrobial armamentarium. Among the β-lactams currently available, carbapenems are unique because they are relatively resistant to hydrolysis by most β-lactamases, in some cases act as "slow substrates" or inhibitors of β-lactamases, and still target penicillin binding proteins. This "value-added feature" of inhibiting β-lactamases serves as a major rationale for expansion of this class of β-lactams. We describe the initial discovery and development of the carbapenem family of β-lactams. Of the early carbapenems evaluated, thienamycin demonstrated the greatest antimicrobial activity and became the parent compound for all subsequent carbapenems. To date, more than 80 compounds with mostly improved antimicrobial properties, compared to those of thienamycin, are described in the literature. We also highlight important features of the carbapenems that are presently in clinical use: imipenem-cilastatin, meropenem, ertapenem, doripenem, panipenem-betamipron, and biapenem. In closing, we emphasize some major challenges and urge the medicinal chemist to continue development of these versatile and potent compounds, as they have served us well for more than 3 decades.

Treatment of Drug-resistant Pneumococcal Meningitis

The approach to therapy in patients with pneumococcal meningitis has changed considerably over the past 20 years. Given the emergence of pneumococcal strains that are intermediately susceptible or highly resistant to penicillin, penicillin is not recommended as empiric therapy for presumed pneumococcal meningitis; the combination of vancomycin and a third-generation cephalosporin (either cefotaxime or ceftriaxone) should be used, pending isolation of the organism and in vitro susceptibility testing. For patients with pneumococcal meningitis caused by highly penicillin- or cephalosporin-resistant strains, the addition of rifampin can be considered if the organism is susceptible in vitro, the expected clinical or bacteriologic response is delayed, or the pneumococcal isolate has a cefotaxime or ceftriaxone minimal inhibitory concentration greater than 4 μg/mL. Meropenem is not a good option for monotherapy of highly penicillin- or cephalosporin-resistant strains, but use of a fluoroquinolone with in vitro activity against Streptococcus pneumoniae (specifically moxifloxacin) is an option in patients failing standard therapy; if used, however, it should be combined with a third-generation cephalosporin or vancomycin. Newer glycopeptides, daptomycin, and linezolid require further study to determine their efficacy in patients with pneumococcal meningitis.

Strategies and new developments in the management of bacterial meningitis

The principles of antimicrobial therapy for acute bacterial meningitis include use of agents that penetrate well into cerebrospinal fluid and attain appropriate cerebrospinal fluid concentrations, are active in purulent cerebrospinal fluid, and are bactericidal against the infecting pathogen. Recommendations for treatment of bacterial meningitis have undergone significant evolution in recent years, given the emergence of pneumococcal strains that are resistant to penicillin. Clinical experience with use of newer agents is limited to case reports, but these agents may be necessary to consider in patients who are failing standard therapy.

[Presumptive bacterial meningitis in adults: initial antimicrobial therapy]

CSF sterilization should be obtained very rapidly to reduce both mortality and morbidity due to bacterial meningitis. Thus, antibiotic treatment should be adapted to the suspected bacterium and administered as early as possible at high dosage with - if necessary - a loading dose and continuous perfusion. The rates of abnormal susceptibility to penicillin of Streptococcus pneumoniae, Neisseria meningitis and Haemophilus influenzae are 37%, 30% and 12% respectively. Thus, ceftriaxone or cefotaxim must be used as empirical treatment. Listeria monocytogenes remains fully susceptible to aminopenicillin, so, the combination aminopenicillin and aminoglycoside is the first-line treatment. Antibiotic resistance, allergy or contra-indications, are in fact rare but in these cases, antibiotic combinations are often needed. The latter are more or less complex and clinically validated; they include molecules such as vancomycine, fosfomycin, fluoroquinolone or linezolid.

[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.

Experimental study of meropenem in the therapy of cephalosporin-susceptible and -resistant pneumococcal meningitis

Meropenem is a carbapenem antibiotic that is highly active against the pathogens causing meningitis. Results with meropenem in the experimental rabbit model of penumococcal meningitis have been controversial, and the possible role of renal dehydropeptidase I in meropenem efficacy has been suggested. The aim of this study was to determine the efficacy of meropenem in two meningitis models and the possible influence of the animal model over results. Two strains of Streptococcus pneumoniae with different susceptibility to beta-lactams have been used in a guinea pig model and the classical rabbit meningitis model. Meropenem was bactericidal at 6 h in the guinea pig model against both strains with a reduction of >4 log ufc/ml. In the rabbit model it was bactericidal at 6 h against the susceptible strain, but against the resistant 3/8 therapeutical failures were recorded at 6 h, being bactericidal at 24 h. In conclusion, meropenem has shown bactericidal activity in both experimental models. This work emphasises the importance of an adequate election of the animal model for the appropriate development of studies of antimicrobial efficacy. We believe that guinea pig should be considered the best choice among laboratory animal species when assessing meropenem efficacy.

Therapeutic effects of bacteriophage Cpl-1 lysin against Streptococcus pneumoniae endocarditis in rats

Cpl-1, a pneumococcal phage lytic enzyme, was tested in rats with experimental endocarditis due to Streptococcus pneumoniae WB4. High-dose regimen Cpl-1 eliminated pneumococci from blood within 30 min and decreased bacterial titers in vegetations (>4 log10 CFU/g) within 2 h. Rapid bacterial lysis induced by Cpl-1 treatment increased cytokine secretion noticeably.

Preincubation of pneumococci with beta-lactams alone or combined with levofloxacin prevents quinolone-induced resistance without increasing intracellular levels of levofloxacin

Preincubation of pneumococci with sub-MIC concentrations of ceftriaxone (1/16x MIC), cefotaxime (1/8x MIC), and meropenem (1/4x MIC) alone or combined with levofloxacin (1/8x MIC) over 6 h prevents the emergence of levofloxacin-resistant mutants after 96 h of incubation but does not affect the intracellular accumulation of levofloxacin in two penicillin-resistant pneumococcal strains, suggesting a link between the mechanism of action of beta-lactams and the emergence of quinolone-induced resistance in pneumococci.