pediatrics
Bacterial Meningitis in Infants Over 3 Months of Age
Treatment of Bacterial Meningitis in Infants
Antimicrobial therapy As soon as bacterial meningitis is diagnosed (actually or presumptively), IV access should be secured and appropriate antimicrobial drugs (and possibly corticosteroids) should be given. Empiric antimicrobial therapy for infants > 3 monthsis directed at the common pathogens: pneumococci, meningococci, andH. influenzaetype b. A typical drug regimen includes Ceftriaxoneorcefotaximeplus Vancomycin Cefotaximeandceftriaxoneare extremely effective against the organisms that usually cause bacterial meningitis in infants > 3 months. The major difference between these drugs is thatceftriaxonehas a much longer serum half-life thancefotaxime.Vancomycinis given because some pneumococcal strains in certain areas are not susceptible to 3rd-generation cephalosporins. In areas (and institutions) where most pneumococci are susceptible to penicillin,vancomycinmay not be necessary, particularly if no gram-positive cocci are seen on the CSF Gram stain; decision to withholdvancomycinshould typically be made in consultation with an infectious disease specialist. Once the infecting organism is identified, more specifically targeted drugs are used; for example,vancomycinmay no longer be required. After immediate empiric antimicrobial drugs have been started, results of CSF and/or blood cultures are used to select a more specifically targeted drug while waiting for microbial identification and susceptibility test results. (See table Specific Therapy for Bacterial Meningitis in Infants Over 3 Months of Age Once Identification and Susceptibility Results Are Known and see table IfS. pneumoniaeis suspected(eg, because gram-positive cocci in pairs are seen on a Gram stain of the CSF), the empiricvancomycinshould be continued until susceptibility test results are available.Vancomycinis stopped if the isolate is susceptible to penicillin or the 3rd-generation cephalosporins; if the isolate isnotsusceptible,vancomycinis continued (and some clinicians addrifampin). Becausedexamethasonecan decrease the CSF penetrance (and thus effectiveness) ofvancomycin, some experts advise that eitherdexamethasoneshould not be given or, if given, thatrifampinbe added concurrently. Disease caused byN. meningitidisis treated reliably withpenicillin Gorampicillinat high doses, or alternatively by a 3rd-generation cephalosporin. If penicillin orampicillintherapy is used, it is followed by a 2-day course of twice-dailyrifampinto clear the carrier state and prevent relapse (rifampinis not necessary if a 3rd-generation cephalosporin is used to complete therapy). IfH. influenzae type bis suspected or proved,disease may be treated reliably with eitherceftriaxoneorcefotaxime;ampicillinmay be used only if the isolate is proved susceptible. Ifampicillintherapy is used, it is followed by a 4-day course of once-dailyrifampinto clear the carrier state and prevent relapse (rifampinis not necessary if a 3rd-generation cephalosporin is used to complete therapy). Specific antimicrobial therapy for other rare infections (eg,S. agalactiae,E. coli,L. monocytogenes,S. aureus) should be selected in consultation with an infectious disease specialist. Pathogen Pathogen Therapy Therapy Streptococcus pneumoniae Penicillin MIC ≤ 0.06 mcg/mL andceftriaxoneorcefotaximeMIC ≤ 0.5 mcg/mL:Penicillin Gorampicillinfor 10–14 days;ceftriaxoneorcefotaximealso acceptable Penicillin MIC ≥ 0.12 mcg/mL andceftriaxoneorcefotaximeMIC ≤ 0.5 mcg/mL:Ceftriaxoneorcefotaximefor 10–14 days Penicillin MIC ≥ 0.12 mcg/mL andceftriaxoneorcefotaximeMIC ≥ 1.0 mcg/mL:Ceftriaxoneorcefotaxime,plusvancomycinwith or withoutrifampinfor 10–14 days Neisseria meningitidis Penicillin Gorampicillinfor 7 days (must be followed byrifampinto eliminate carrier state) Alternatives:Ceftriaxoneorcefotaxime Haemophilus influenzaetype b Ceftriaxoneorcefotaximefor 10 days Alternative:Ampicillinif isolate is susceptible (must be followed byrifampinto eliminate carrier state) MIC = minimum inhibitory concentration. Drug Drug Infants and Children Infants and Children Ampicillin 50–75 mg/kg every 6 hours Cefotaxime 50–75 mg/kg every 6 hours Ceftriaxone 40–50 mg/kg every 12 hours or 80–100 mg/kg every 24 hours Penicillin G 50,000–66,667 units/kg every 4 hours or 75,000–100,000 units/kg every 6 hours Rifampin 10 mg/kg every 12 hours Vancomycin 10–15 mg/kg every 6 hours The use of corticosteroids (eg,dexamethasone) as adjunctive therapy in bacterial meningitis has been studied for decades and continues to be controversial. The beneficial effects of corticosteroids in reducing neurologic morbidity appear to vary with the age of the patient (child or adult), the specific bacterial etiology, and even whether the patient lives in an industrialized country or in the developing world. At present, evidence suggests thatdexamethasonereduces hearing impairment in infants and children living in industrialized countries who have bacterial meningitis caused byH. influenzaetype b. The effectiveness ofdexamethasonein meningitis caused by other organisms remains unproved, although some studies of adults in industrialized countries with meningitis caused byS. pneumoniaereport improved neurologic outcomes and reduced mortality.Dexamethasonedoes not appear to benefit children or adults with bacterial meningitis who live in developing countries, nor does it seem to benefit neonates with meningitis. Thus,dexamethasone0.15 mg/kg IV should be given before, or within 1 hour after, antimicrobial therapy in children > 6 weeks of age with meningitis caused byH. influenzaetype b. The drug is continued every 6 hours for 4 days in confirmedH. influenzaetype b meningitis. Some experts also recommend using this samedexamethasoneregimen in children with pneumococcal meningitis who are > 6 weeks of age. For optimal efficacy,dexamethasonemust be started at the time of diagnosis; this is not always possible, unless the Gram stain of the fluid or epidemiologic factors (eg, disease contact history) can yield an immediate etiologic diagnosis. In regions where children have been given routineH. influenzaetype b and pneumococcal conjugate vaccines, bacterial meningitis caused by these organisms will be rare. For these reasons, along with the conflicting evidence regarding the benefits ofdexamethasonetherapy, many pediatric infectious disease experts no longer routinely give corticosteroids to infants with meningitis. 