Cefepime cerebrospinal fluid concentrations in neonatal bacterial meningitis

New and old lessons from a devastating case of neonatal E coli meningitis

BACKGROUND

Neonatal Escherichia coli (E coli) meningitis results in significant morbidity and mortality. We present a case of a premature infant with extensive central nervous system (CNS) injury from recurrent E coli infection and the non-traditional methods necessary to identify and clear the infection.

CASE PRESENTATION

The infant was transferred to our institution's pediatric intensive care unit (PICU) after recurrence of E coli CNS infection requiring neurosurgical intervention. He had been treated for early onset sepsis (EOS) with ampicillin and gentamicin for 10 days followed by rapid development of ampicillin-resistant E coli septic shock and meningitis after discontinuation of antibiotics. Sterility of the CNS was not confirmed at the end of 21 days of cefepime therapy and was subsequently followed by recurrent ampicillin-resistant E coli septic shock and CNS infection. Despite 6 weeks of appropriate therapy with sterility of CSF by traditional methods, he suffered from intractable seizures with worsening hydrocephalus. Transferred to our institution, he underwent endoscopic 3rd ventriculostomy with cyst fenestration revealing purulent fluid and significant pleocytosis. An additional 3 weeks of systemic and intraventricular antibiotics with cefepime and tobramycin were given but a significant CNS neutrophil-predominant pleocytosis persisted (average of ∼ 21,000 cells/mm3). Repeated gram stains, cultures, polymerase chain reaction (PCR) testing, and metagenomic next generation sequencing (NGS) testing of CSF were negative for pathogens but acridine orange stain (AO) revealed numerous intact rod-shaped bacteria. After the addition of ciprofloxacin, sterility and resolution of CSF pleocytosis was finally achieved.

CONCLUSION

Neonatal E coli meningitis is a well-known entity but unlike other bacterial infections, it has not proven amenable to shorter, more narrow-spectrum antibiotic courses or limiting invasive procedures such as lumbar punctures. Further, microbiologic techniques to determine CSF sterility suffer from poorly understood limitations leading to premature discontinuation of antibiotics risking further neurologic damage in vulnerable hosts.

Treatment options for neonatal infections in the post-cefotaxime era

INTRODUCTION

: Cefotaxime has been used for the management of neonatal infections since the 1990s for suspected meningitis and to mitigate gentamicin-associated renal injury. Its shortage in 2015 and subsequent removal from the U.S. pharmaceutical market forced providers to consider alternatives. Ceftriaxone, a cephalosporin with an identical antibacterial spectrum of activity to cefotaxime, is contraindicated in neonates due to its risk of biliary pseudolithiasis. Ceftazidime was recommended as an alternative by the American Academy of Pediatrics but is inequivalent.

AREAS COVERED

: This article addresses indications for cephalosporin use and considerations when selecting an alternative to cefotaxime. Differences among cefotaxime, ceftriaxone, ceftazidime, and cefepime are discussed and compared to the standard-of-care presumptive regimen, ampicillin and gentamicin. The authors consider the data behind the neonatal contraindication to ceftriaxone and provide recommendations for their application to practice.

EXPERT OPINION

: The data against ceftriaxone use in neonates remain poor, particularly in the context of the cefotaxime shortage and lack of an equivalent alternative. Ceftriaxone could be considered in low-risk neonates without hyperbilirubinemia or exposure to calcium-containing fluids on a case-by-case basis. Ceftazidime monotherapy for presumptive management of neonatal infections is inappropriate; cefepime should be more frequently utilized in neonates who are poor candidates for ceftriaxone.

Potential Antibiotics for the Treatment of Neonatal Sepsis Caused by Multidrug-Resistant Bacteria

Neonatal sepsis causes up to an estimated 680,000 deaths annually worldwide, predominantly in low- and middle-income countries (LMICs). A significant and growing proportion of bacteria causing neonatal sepsis are resistant to multiple antibiotics, including the World Health Organization-recommended empiric neonatal sepsis regimen of ampicillin/gentamicin. The Global Antibiotic Research and Development Partnership is aiming to develop alternative empiric antibiotic regimens that fulfil several criteria: (1) affordable in LMIC settings; (2) activity against neonatal bacterial pathogens, including extended-spectrum β-lactamase producers, gentamicin-resistant Gram-negative bacteria, and methicillin-resistant Staphylococcus aureus (MRSA); (3) a licence for neonatal use or extensive experience of use in neonates; and (4) minimal toxicities. In this review, we identify five antibiotics that fulfil these criteria: amikacin, tobramycin, fosfomycin, flomoxef, and cefepime. We describe the available characteristics of each in terms of mechanism of action, resistance mechanisms, clinical pharmacokinetics, pharmacodynamics, and toxicity profile. We also identify some knowledge gaps: (1) the neonatal pharmacokinetics of cefepime is reliant on relatively small and limited datasets, and the pharmacokinetics of flomoxef are also reliant on data from a limited demographic range and (2) for all reviewed agents, the pharmacodynamic index and target has not been definitively established for both bactericidal effect and emergence of resistance, with many assumed to have an identical index/target to similar class molecules. These five agents have the potential to be used in novel combination empiric regimens for neonatal sepsis. However, the data gaps need addressing by pharmacokinetic trials and pharmacodynamic characterisation.

Cefepime Dosing in Neonates: What is the Evidence?

OBJECTIVE

Recommended cefepime dosing strategies in neonates varies in commonly utilized dosing references with regard to dose and frequency. The objective of this review is to summarize and evaluate the available literature describing cefepime dosing in neonatal patients.

STUDY DESIGN

We performed a literature review in MEDLINE using the keyword cefepime. The search was limited to the English language, humans, and patients <2 months of age. We evaluated four pharmacokinetic studies and two studies describing the use of cefepime in clinical practice.

RESULTS

The available studies assessing cefepime serum concentrations in neonatal patients demonstrated maintenance of adequate pharmacokinetic parameters when utilizing a dosing frequency of every 12 hours, specifically for organisms with a minimum inhibitory concentration (MIC) ≤ 8 mg/L. In studies evaluating clinical outcomes of cefepime use in neonates, the most frequent adverse effects reported included seizures and hypophosphatemia. Microbiologic cure was demonstrated with a dosing regimen of 50 mg/kg per dose every 12 hours.

CONCLUSION

Cefepime dosed 30 to 50 mg/kg per dose every 12 hours may be appropriate to achieve a concentration two to four times above an MIC ≤ 8 mg/L for at least 60% of the dosing interval in neonatal patients.

Pharmacokinetics of antibacterial agents in the CSF of children and adolescents

The adequate management of central nervous system (CNS) infections requires that antimicrobial agents penetrate the blood-brain barrier (BBB) and achieve concentrations in the CNS adequate for eradication of the infecting pathogen. This review details the currently available literature on the pharmacokinetics (PK) of antibacterials in the CNS of children. Clinical trials affirm that the physicochemical properties of a drug remain one of the most important factors dictating penetration of antimicrobial agents into the CNS, irrespective of the population being treated (i.e. small, lipophilic drugs with low protein binding exhibit the best translocation across the BBB). These same physicochemical characteristics determine the primary disposition pathways of the drug, and by extension the magnitude and duration of circulating drug concentrations in the plasma, a second major driving force behind achievable CNS drug concentrations. Notably, these disposition pathways can be expected to change during the normal process of growth and development. Finally, CNS drug penetration is influenced by the nature and extent of the infection (i.e. the presence of meningeal inflammation). Aminoglycosides have poor CNS penetration when administered intravenously. Intrathecal gentamicin has been studied in children with more promising results, often exceeding the minimum inhibitory concentration. There are very limited data with intrathecal tobramycin in children. However, in the few patients that have been studied, the CSF concentrations were highly variable. Penicillins generally have good CNS penetration. Aqueous penicillin G reaches greater concentrations than procaine or benzathine penicillin. Concentrations remain detectable for ≥ 12 h. Of the aminopenicillins, both ampicillin and parenteral amoxicillin reach adequate CNS concentrations; however, orally administered amoxicillin resulted in much lower concentrations. Nafcillin and piperacillin are the final two penicillins with pediatric data: their penetration is erratic at best. Cephalosporins vary greatly in regard to their CSF penetration. Few first- and second-generation cephalosporins are able to reach higher CSF concentrations. Cefuroxime is the only exception and is usually avoided due to its adverse effects and slower sterilization of the CSF than third-generation agents. Ceftriaxone, cefotaxime, ceftazidime, cefixime and cefepime have been studied in children and are all able to adequately penetrate the CSF. As with penicillins, concentrations are greatest in the presence of meningeal inflammation. Meropenem and imipenem are the only carbapenems with pediatric data. Imipenem reaches higher CSF concentrations; however, meropenem is preferred due to its lower incidence of seizures. Aztreonam has also demonstrated favorable penetration but only one study has been completed in children. Both chloramphenicol and sulfamethoxazole/trimethoprim (cotrimoxazole) penetrate into the CNS well; however, significant toxicities limit their use. The small size and minimal protein binding of fosfomycin contribute to its favorable CNS PK. Although rarely used, it achieves higher concentrations in the presence of inflammation and accumulation is possible. Linezolid reaches high CSF concentrations; however, more frequent dosing might be required in infants due to their increased elimination. Metronidazole also has very limited information but it demonstrated favorable results similar to adult data; CSF concentrations even exceeded plasma concentrations at certain time points. Rifampin (rifampicin) demonstrated good CNS penetration after oral administration. Vancomycin demonstrates poor CNS penetration after intravenous administration. When combined with intraventricular therapy, CNS concentrations are much greater. Of the antituberculosis agents, isoniazid, pyrazinamide and streptomycin have been studied in children. Isoniazid and pyrazinamide have favorable CSF penetration. Streptomycin appears to produce unpredictable CSF levels. No pediatric-specific data are available for clindamycin, daptomycin, macrolides, tetracyclines, and fluoroquinolones. Daptomycin, fluoroquinolones, and tetracyclines have demonstrated favorable CNS penetration in adults; however, data are limited due to their potential pediatric-specific toxicities and newness within the marketplace. Macrolides and clindamycin have demonstrated poor CNS penetration in adults and thus have not been studied in pediatrics.

Pharmacokinetics of cephalosporins in the neonate: a review

The aim of this work was to review the published data on the pharmacokinetics of cephalosporins in neonates to provide a critical analysis of the literature as a useful tool for physicians. The bibliographic search was performed for articles published up to December 3, 2010, using PubMed. In addition, the book Neofax: A Manual of Drugs Used in Neonatal Care by Young and Mangum was consulted. The cephalosporins are mainly eliminated by the kidneys, and their elimination rates are reduced at birth. As a consequence, clearance is reduced and t1/2 is more prolonged in the neonate than in more mature infants. The neonate's substantial body water content creates a large volume of distribution (Vd) of cephalosporins, as these drugs are fairly water soluble. Postnatal development is an important factor in the maturation of the neonate, and as postnatal age proceeds, the clearance of cephalosporins increases. The maturation of the kidney governs the pharmacokinetics of cephalosporins in the infant. Clearance and t1/2 are influenced by development, and this must be taken into consideration when planning a cephalosporin dosage regimen for the neonate.