Intraventricular antibiotics for bacterial meningitis in neonates

Evidence That Antibiotics Bind to Human Mitochondrial Ribosomal RNA Has Implications for Aminoglycoside Toxicity

Aminoglycosides are a well known antibiotic family used to treat bacterial infections in humans and animals, but which can be toxic. By binding to the decoding site of helix44 of the small subunit RNA of the bacterial ribosome, the aminoglycoside antibiotics inhibit protein synthesis, cause misreading, or obstruct peptidyl-tRNA translocation. Although aminoglycosides bind helix69 of the bacterial large subunit RNA as well, little is known about their interaction with the homologous human helix69. To probe the role this binding event plays in toxicity, changes to thermal stability, base stacking, and conformation upon aminoglycoside binding to the human cytoplasmic helix69 were compared with those of the human mitochondrial and Escherichia coli helix69. Surprisingly, binding of gentamicin and kanamycin A to the chemically synthesized terminal hairpins of the human cytoplasmic, human mitochondrial, and E. coli helix69 revealed similar dissociation constants (1.3-1.7 and 4.0-5.4 μM, respectively). In addition, aminoglycoside binding enhanced conformational stability of the human mitochondrial helix69 by increasing base stacking. Proton one-dimensional and two-dimensional NMR suggested significant and specific conformational changes of human mitochondrial and E. coli helix69 upon aminoglycoside binding, as compared with human cytoplasmic helix69. The conformational changes and similar aminoglycoside binding affinities observed for human mitochondrial helix69 and E. coli helix69, as well as the increase in structural stability shown for the former, suggest that this binding event is important to understanding aminoglycoside toxicity.

Clinical pharmacokinetics of antibacterials in cerebrospinal fluid

In the past 20 years, an increased discrepancy between new available antibacterials and the emergence of multidrug-resistant strains has been observed. This condition concerns physicians involved in the treatment of central nervous system (CNS) infections, for which clinical and microbiological success depends on the rapid achievement of bactericidal concentrations. In order to accomplish this aim, the choice of drugs is based on their disposition toward the cerebrospinal fluid (CSF), which is influenced by the physicochemical characteristics of antibacterials. A reduced distribution into CSF has been documented for beta-lactams, especially cephalosporins and carbapenems, on the basis of their hydrophilic nature. However, they represent a cornerstone of the majority of combined therapeutic schemes for their ability to achieve bactericidal concentrations, especially in the presence of inflamed meninges. The good tolerability of beta-lactams makes possible high daily dose intensities, which may be associated with increased probability of cure. Furthermore, the adoption of continuous infusion seems to be a fruitful option. Fluoroquinolones, namely moxifloxacin, and antituberculosis drugs, together with the agents such as linezolid, reach the highest CSF/plasma concentration ratio, which is greater than 0.8, and for most of these drugs it is near 1. For all drugs that are currently used for the treatment of CNS infections, the evaluation of pharmacokinetic/pharmacodynamic parameters, on the basis of dosing regimens and their time-dependent or concentration-dependent pattern of bacterial killing, remains an important aspect of clinical investigation and medical practice.

Current concepts in the treatment of bacterial meningitis beyond the neonatal period

The epidemiology and treatment approach to bacterial meningitis has changed dramatically since the advent of antimicrobial therapy. New vaccines against meningeal pathogens have been implemented into national immunization programs successfully around the world. Antibiotic resistance has had a considerable impact on the efficacy of several therapeutic agents. In this review, the authors will discuss the principles of antibiotic chemotherapy, focusing on new agents for the treatment of penicillin-resistant pneumococci and adjunctive treatments to reduce the inflammatory response to bacterial infection of the meninges.

Intraventricular antibiotics for bacterial meningitis in neonates

BACKGROUND

Neonatal meningitis may be caused by bacteria, especially gram-negative bacteria, which are difficult to eradicate from the cerebrospinal fluid (CSF) using safe doses of antibiotics. In theory, intraventricular administration of antibiotics would produce higher antibiotic concentrations in the CSF than intravenous administration alone, and eliminate the bacteria more quickly. However, ventricular taps may cause harm.

OBJECTIVES

To assess the effectiveness and safety of intraventricular antibiotics (with or without intravenous antibiotics) in neonates with meningitis (with or without ventriculitis) as compared to treatment with intravenous antibiotics alone.

SEARCH METHODS

The Cochrane Library, Issue 2, 2007; MEDLINE; EMBASE; CINAHL and Science Citation Index were searched in June 2007. The Oxford Database of Perinatal Trials was searched in June 2004. Pediatric Research (abstracts of proceedings) were searched (1990 to April 2007) as were reference lists of identified trials and personal files. No language restrictions were applied.This search was updated in May 2011.

SELECTION CRITERIA

Selection criteria for study inclusion were: randomised or quasi-randomised controlled trials in which intraventricular antibiotics with or without intravenous antibiotics were compared with intravenous antibiotics alone in neonates (< 28 days old) with meningitis. One of the following outcomes was required to be reported: mortality during initial hospitalisation; neonatal or infant mortality, or both; neurodevelopmental outcome; duration of hospitalisation; duration of culture positivity of CSF and side effects.

DATA COLLECTION AND ANALYSIS

All review authors abstracted information for outcomes reported and one review author checked for discrepancies and entered data into RevMan 5.1. Risk ratio (RR), risk difference (RD), number needed to treat for an additional beneficial outcome (NNTB) or number needed to treat for an additional harmful outcome (NNTH), and mean difference (MD), using the fixed-effect model are reported with 95% confidence intervals (CI).

MAIN RESULTS

The updated search in June 2011 did not identify any new trials. One study is included in the review. This study assessed the effect of intraventricular gentamicin in a mixed population of neonates (69%) and older infants (31%) with gram-negative meningitis and ventriculitis. Mortality was statistically significantly higher in the group that received intraventricular gentamicin in addition to intravenous antibiotics compared to the group receiving intravenous antibiotics alone (RR 3.43; 95% CI 1.09 to 10.74; RD 0.30; 95% CI 0.08 to 0.53); NNTH 3; 95% CI 2 to 13). Duration of CSF culture positivity did not differ significantly (MD -1.20 days; 95% CI -2.67 to 0.27).

AUTHORS' CONCLUSIONS

In one trial that enrolled infants with gram-negative meningitis and ventriculitis, the use of intraventricular antibiotics in addition to intravenous antibiotics resulted in a three-fold increased RR for mortality compared to standard treatment with intravenous antibiotics alone. Based on this result, intraventricular antibiotics as tested in this trial should be avoided. Further trials comparing these interventions are not justified in this population.

Penetration of drugs through the blood-cerebrospinal fluid/blood-brain barrier for treatment of central nervous system infections

The entry of anti-infectives into the central nervous system (CNS) depends on the compartment studied, molecular size, electric charge, lipophilicity, plasma protein binding, affinity to active transport systems at the blood-brain/blood-cerebrospinal fluid (CSF) barrier, and host factors such as meningeal inflammation and CSF flow. Since concentrations in microdialysates and abscesses are not frequently available for humans, this review focuses on drug CSF concentrations. The ideal compound to treat CNS infections is of small molecular size, is moderately lipophilic, has a low level of plasma protein binding, has a volume of distribution of around 1 liter/kg, and is not a strong ligand of an efflux pump at the blood-brain or blood-CSF barrier. When several equally active compounds are available, a drug which comes close to these physicochemical and pharmacokinetic properties should be preferred. Several anti-infectives (e.g., isoniazid, pyrazinamide, linezolid, metronidazole, fluconazole, and some fluoroquinolones) reach a CSF-to-serum ratio of the areas under the curves close to 1.0 and, therefore, are extremely valuable for the treatment of CNS infections. In many cases, however, pharmacokinetics have to be balanced against in vitro activity. Direct injection of drugs, which do not readily penetrate into the CNS, into the ventricular or lumbar CSF is indicated when other effective therapeutic options are unavailable.

Principles of antimicrobial therapy

We have discussed important factors involved in choosing appropriate antimicrobial regimens for the treatment of bacterial meningitis and brain abscess to illustrate common themes relevant to the treatment of these diseases. We have limited this review to these conditions for two main reasons: (1) the principles involved in optimal antimicrobial therapy for these diseases likely apply to others CNS infections, such as viral and fungal diseases; and (2) little pharmacological information is currently available for other types of CNS infections. Many of the studies addressing the relevant pharmacological and microbiological aspects of antimicrobial therapy for CNS infections have been performed in experimental animal models and, as a result, the information derived from these studies may be different when examined in appropriate human studies. Our current understanding of appropriate antimicrobial therapy for CNS infections may be summarized as follows: 1. Choose bactericidal antimicrobials that effectively cross the BBB to achieve CSF concentrations well above the MBC (≥ 10-fold) for the suspected bacterial pathogen(s). 2. Take into consideration the relevant PD parameters the bactericidal activity of the antimicrobials used to treat bacterial meningitis, such as t > MBC or AUC/MBC. 3. Tailor the antimicrobial regimen based on microbiological information, once available. However, with respect to brain abscess therapy, keep in mind that anaerobes are commonly involved, but difficult to culture, and consider including antianaerobic therapy even if the bacterial cultures do not grow anaerobes. 4. Treat bacterial meningitis caused by nonmeningococcal pathogens for 7-10 days, but monitor clinical progress to determine whether the patient should continue on a more prolonged antimicrobial course. Meningococcal meningitis may be treated with 3-4 days of effective antimicrobial therapy, again with the caveat that the patients clinical course should dictate duration of therapy. 5. Treat brain abscess, preferably after aspiration/drainage, for at least 6 weeks with intravenous antimicrobials for brain abscess on the clinical response (e.g., improved symptoms, lack of new neurological findings) and radiographic changes (e.g., reduction in cavity size).

Meningitis and Encephalomyelitis in Horses

This article provides an overview of meningitis and encephalomyelitis in horses, including diagnostic tests, treatment developments, and preventative measures reported in the equine and human medical literature of the past few years.

Intraventricular antibiotics for bacterial meningitis in neonates

BACKGROUND

Neonatal meningitis may be caused by bacteria, especially gram-negative bacteria, which are difficult to eradicate from the cerebrospinal fluid (CSF) using safe doses of antibiotics. In theory, intraventricular administration of antibiotics would produce higher antibiotic concentrations in the CSF than intravenous administration alone, and eliminate the bacteria more quickly. However, ventricular taps may cause harm.

OBJECTIVES

To assess the effectiveness and safety of intraventricular antibiotics (with or without intravenous antibiotics) in neonates with meningitis (with or without ventriculitis) as compared to treatment with intravenous antibiotics alone.

SEARCH STRATEGY

MEDLINE, EMBASE, The Cochrane Library, Issue 2, 2004, Science Citation Index, and the Oxford Database of Perinatal Trials were searched in June 2004. Pediatric Research (abstracts of proceedings) were searched (1990 - April 2004) as were reference lists of identified trials and personal files. No language restrictions were applied.

SELECTION CRITERIA

Selection criteria for study inclusion were: Randomized or quasi-randomized controlled trials in which intraventricular antibiotics with or without intravenous antibiotics were compared with intravenous antibiotics alone in neonates (< 28 days old) with meningitis. One of the following outcomes was required to be reported: mortality during initial hospitalization, neonatal and/or infant mortality, neurodevelopmental outcome, duration of hospitalization, duration of culture positivity of CSF and side effects.

DATA COLLECTION AND ANALYSIS

All reviewers abstracted information for outcomes reported and one reviewer checked for discrepancies and entered data into RevMan 4.2. Relative risk (RR), risk difference (RD), number needed to treat (NNT) or number needed to harm (NNH), and mean difference (MD), using the fixed effects model are reported with 95% confidence intervals (CI). The fixed effect model was used for meta-analysis.

MAIN RESULTS

One study was included in the review. This study assessed the effect of intraventricular gentamicin in a mixed population of neonates (69%) and older infants (31%) with gram negative meningitis and ventriculitis. Mortality was statistically significantly higher in the group that received intraventricular gentamicin in addition to intravenous antibiotics compared to the group receiving intravenous antibiotics alone [RR 3.43 (95% CI, 1.09, 10.74; RD 0.30 (95% CI, 0.08, 0.53); NNH was 3 (95% CI; 2 ,13)]. Duration of CSF culture positivity did not differ significantly (MD -1.20 days (95% CI, -2.67, 0.27).

REVIEWERS' CONCLUSIONS

In one trial, enrolling infants with gram negative meningitis and ventriculitis, the use of intraventricular antibiotics in addition to intravenous antibiotics resulted in a 3 fold increased RR for mortality compared to standard treatment with intravenous antibiotics alone. Based on this result, intraventricular antibiotics as tested in this trial should be avoided. Further trials comparing these interventions are not justified in this population.