Page 924 - Hall et al (2015) Principles of Critical Care-McGraw-Hill

CHAPTER 71: Bacterial Infections of the Central Nervous System 655

S pneumoniae may be likely (see below). One other situation deserves
TABLE 71-2 Empirical Therapy of Purulent Meningitis
comment—in patients after neurosurgery or patients with CSF shunts or
Age Standard Therapy foreign bodies, likely infecting organisms include staphylococci (S epi-
<1 mo Ampicillin plus cefotaxime, or ampicillin plus an aminoglycoside b dermidis or S aureus), diphtheroids (including Propionibacterium acnes),
and gram-negative bacilli (including P aeruginosa). 13,29 Antimicrobial
1-23 mo Vancomycin plus a third-generation cephalosporin a
therapy in these situations should consist of vancomycin plus either
2-50 y Vancomycin plus a third-generation cephalosporin a ceftazidime, cefepime, or meropenem pending culture results.
>50 y Vancomycin plus ampicillin plus a third-generation cephalosporin a Once an infecting microorganism has been isolated, antimicrobial
therapy can be modified for optimal treatment. 21,29,32 Our antibiotics of
a Cefotaxime or ceftriaxone.
choice are listed in Table 71-4. Dosages for adults are listed in Table 71-5.
b Gentamicin, tobramycin, or amikacin. For bacterial meningitis due to susceptible strains of S pneumoniae
or N meningitidis, penicillin G and ampicillin are equally efficacious.
Although in past years pneumococci remained uniformly susceptible to
in whom antimicrobial therapy is delayed. Although many clinicians penicillin (minimal inhibitory concentration ≤0.06 µg/mL), worldwide
routinely perform CT before lumbar puncture, this is probably not reports have now documented resistant strains of pneumococci. In
necessary in most patients. In a recent retrospective study of 301 adults view of these recent trends, and because sufficient CSF concentra-
with suspected meningitis, the clinical features at baseline that were tions of penicillin are difficult to achieve with standard high paren-
33
associated with an abnormal finding on CT of the head were an age of at teral doses (initial CSF concentrations of ∼1 µg/mL), penicillin can
least 60 years, immunocompromise, a history of CNS disease, a history never be recommended as empirical antimicrobial therapy when
of seizure within 1 week before presentation, and the following neuro- S pneumoniae is considered a likely infecting pathogen. Further, suscep-
logic abnormalities: an abnormal level of consciousness, an inability to tibility testing must be performed on all CSF isolates. For strains that are
answer two consecutive questions correctly or to follow two consecutive resistant to penicillin (MIC ≥0.12 µg/mL, but sensitive to a third-genera-
commands, gaze palsy, abnormal visual fields, facial palsy, arm drift, tion cephalosporin (MIC <1 µg/mL), cefotaxime or ceftriaxone should be
leg drift, and abnormal language. These results need to be validated but used; for strains resistant to penicillin and third-generation cephalospo-
are a reasonable guide in determining which patients require CT before rins, vancomycin in combination with a third-generation cephalosporin
lumbar puncture. It is reasonable to proceed with lumbar puncture is the antimicrobial regimen of choice because vancomycin used alone,
without performing a CT scan in patients who do not have new-onset especially when combined with adjunctive dexamethasone, may not be
seizures, an immunocompromised state, signs that are suspicious for optimal therapy for patients with pneumococcal meningitis. This com-
space-occupying lesions (eg, papilledema or focal neurologic findings), bination should be continued pending results of susceptibility testing.
or moderate or severe impairment of consciousness. However, despite Adequate CSF concentrations of vancomycin, however, may be attained
29
these guidelines, the decision to perform a lumbar puncture without
first doing a CT scan must be individualized. In addition, a normal
CT scan does not always mean that performance of a lumbar puncture
is safe; clinical signs that suggest the need to delay lumbar puncture
include those of impending herniation (eg, deteriorating level of con- TABLE 71-4 Antimicrobial Therapy of Bacterial Meningitis
sciousness, particularly a Glasgow Coma Scale score ≤11; brain stem Organism Antibiotic of Choice
signs such as pupillary changes, posturing, or irregular respirations; or Streptococcus pneumoniae
a very recent seizure). 34
Our choices for empirical antibiotic therapy in patients with presumed Penicillin MIC ≤0.06 µg/mL Penicillin G or ampicillin
bacterial meningitis, based on age, are presented in Table 71-2. 21,29,32 For Penicillin MIC ≥0.12 µg/mL
neonates younger than 1 month, the most likely infecting organisms are Ceftriaxone or cefotaxime MIC <1.0 µg/mL Third-generation cephalosporin a
E coli, S agalactiae, and L monocytogenes; for those ages 1 to 23 months,
infection may be due to S pneumoniae, N meningitidis, S agalactiae, E Ceftriaxone or cefotaxime MIC ≥1.0 µg/mL Vancomycin plus a third-
coli, or H influenzae. From age 2 to 50 years, most cases of meningitis generation cephalosporin a,d
are due to N meningitidis and S pneumoniae. In older adults (≥50 years), Neisseria meningitidis Penicillin G or ampicillin, or a
the meningococcus and the pneumococcus are possible causes, as are third-generation cephalosporin a
L monocytogenes and gram-negative bacilli. For all patients in whom Haemophilus influenzae
S pneumoniae is a possible causative pathogen (essentially all patients
≥1 month of age), vancomycin should be added to empirical therapeutic β-Lactamase negative Ampicillin
regimens because highly penicillin- or cephalosporin-resistant strains of β-Lactamase positive Third-generation cephalosporin a
Enterobacteriaceae b Third-generation cephalosporin a
Pseudomonas aeruginosa Ceftazidime or cefepime c
c
c
TABLE 71-3 Targeted Antimicrobial Therapy for Acute Bacterial Meningitis Streptococcus agalactiae Penicillin G or ampicillin c
with Presumptive Pathogen Identification by Gram Stain Listeria monocytogenes Ampicillin or penicillin G c
c
Microorganism Recommended Therapy Staphylococcus aureus
Streptococcus pneumoniae Vancomycin plus a third-generation cephalosporin a,b Methicillin sensitive Nafcillin or oxacillin
Neisseria meningitidis Third-generation cephalosporin a Methicillin resistant Vancomycin
Haemophilus influenzae Third-generation cephalosporin a Staphylococcus epidermidis Vancomycin d
c
Streptococcus agalactiae Ampicillin or penicillin G c a Cefotaxime or ceftriaxone.
Listeria monocytogenes Ampicillin or penicillin G c b Choice of a specific antimicrobial agent should be guided by in vitro susceptibility testing.
c
a Cefotaxime or ceftriaxone. c Addition of an aminoglycoside should be considered.
b Some experts would add rifampin if dexamethasone is also given. d Addition of rifampin may be indicated.
c Addition of an aminoglycoside should be considered. MIC, minimal inhibitory concentration.

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