Page 927 - Hall et al (2015) Principles of Critical Care-McGraw-Hill

658 PART 5: Infectious Disorders

while in close proximity (≤3 feet) to the index patient. For meningococ- TABLE 71-6 Predisposing Conditions and Microbiology in Brain Abscess
cal meningitis, chemoprophylaxis usually is recommended only for close
contacts (eg, household contacts, day-care contacts, nursery school con- Predisposing Condition Usual Bacterial Isolates
tacts, contacts who eat or sleep in the same dwelling, and close contacts Otitis media or mastoiditis Streptococci (anaerobic or aerobic), Bacteroides
such as in a military barracks or boarding school); it is not indicated and Prevotella sp, Enterobacteriaceae
for other groups (eg, office coworkers or classmates) unless there has
been intimate contact. However, one study has suggested that school- Sinusitis (frontoethmoidal or Streptococci, Bacteroides sp, Enterobacteriaceae,
Staphylococcus aureus, Haemophilus sp
sphenoidal)
aged children may be at increased risk of secondary infection when
classrooms are crowded and/or when contact during lunch or recess is Dental sepsis Mixed Fusobacterium, Prevotella, Bacteroides,
frequent. For travelers, chemoprophylaxis should be considered for any Actinomyces, and Streptococcus sp
passenger who had direct contact with the respiratory secretions of the Penetrating trauma or postneurosurgical Staphylococcus aureus, streptococci,
index patient, or anyone sitting next to the index patient on a prolonged state Enterobacteriaceae, Clostridium sp
flight (≥8 hours). Prophylaxis is not necessary for medical personnel Congenital heart disease Streptococci, Haemophilus sp
caring for cases unless there has been intimate contact (eg, mouth-to-
mouth resuscitation, or those who perform endotracheal intubation or Lung abscess, empyema, bronchiectasis Fusobacterium, Actinomyces, and Bacteroides
endotracheal tube management). Chemoprophylaxis may also need to sp Nocardia asteroides; streptococci
be administered to the index patient before hospital discharge because Bacterial endocarditis Staphylococcus aureus, streptococci
certain antimicrobial agents (eg, high-dose penicillin or chlorampheni- Immunosuppressed host Nocardia, Enterobacteriaceae
col) do not reliably eradicate meningococci from the nasopharynx of
colonized patients. All contacts (children and adults) of a patient with
H influenzae meningitis should receive chemoprophylaxis if exposure
has occurred in a household or day-care center containing children focus of infection, most often in the middle ear, mastoid air cells, or
4 years or younger (other than the index case), provided that the expo- paranasal sinuses. Early studies associated 40% of brain abscesses with
sure to H influenzae type b was in the week before presentation. otitis media, but this number has been decreasing in recent years.
The recommended drug of choice for chemoprophylaxis, for contacts However, if antibiotic therapy of otitis is neglected, there is an increased
of patients with either type of meningitis, is rifampin. For contacts of risk of intracranial complications. Brain abscess secondary to otitis
21
patients with H influenzae meningitis, rifampin at a daily dose of 20 mg/kg media is bimodally distributed, with peaks in children (acute otitis
(not exceeding 600 mg) for 4 consecutive days is most effective. For media) and in persons older than 40 years (chronic otitis media). Most
contacts of meningococcal cases, one rifampin dose of 10 mg/kg cases of brain abscess due to otitis media occur in the temporal lobe
(not exceeding 600 mg) twice a day for 2 days is effective. One dose and cerebellum. The etiologic agents in brain abscess secondary to otitis
of ciprofloxacin (500 or 750 mg) may also be effective for eradicat- media include a broad range of bacterial species, including streptococci,
ing nasopharyngeal carriage of meningococci; ciprofloxacin is not Bacteroides fragilis, and members of the Enterobacteriaceae.
recommended in pregnant women or in persons younger than 18 years Paranasal sinusitis continues to be an important condition predispos-
because of concerns of cartilage damage. Ciprofloxacin may well sup- ing to brain abscess, most commonly in persons ages 10 to 30 years. The
plant rifampin for chemoprophylaxis in adults. However, three cases frontal lobe is the predominant abscess site; when brain abscess com-
of ciprofloxacin-resistant N meningitidis have been reported in North plicates sphenoid sinusitis, the temporal lobe or sella turcica is usually
52,54
Dakota and Minnesota, leading the CDC to no longer recommend involved. Streptococci are the predominant bacterial species involved
51
ciprofloxacin for meningococcal chemoprophylaxis in selected coun- in brain abscess secondary to sinusitis, although anaerobes, S aureus,
ties in these states. In one study, ceftriaxone (250 mg intramuscularly in and gram-negative bacilli have been isolated.
adults or 125 mg in children) was shown to eliminate the meningococ- Dental infections are a less common source of brain abscess; infec-
cal serogroup A carrier state in 97% of patients for up to 2 weeks and is tions of molar teeth seem most often to be the cause. The frontal lobe is
probably the safest alternative for meningococcal chemoprophylaxis in usually involved, but temporal lobe extension has also been described.
pregnant women. Azithromycin (500 mg orally once) was also shown to A second mechanism of brain abscess formation is hematogenous
be as effective as a four-dose regimen of rifampin in the eradication of dissemination to the brain from a distant focus of infection. These
meningococci from the nasopharynx. 21 abscesses are usually multiple and multiloculated, and they have a higher
mortality rate than do abscesses that arise secondary to contiguous
foci of infection. 52,54 The most common sources in adults are chronic
BRAIN ABSCESS pyogenic lung diseases, especially lung abscess, bronchiectasis, empy-
■ EPIDEMIOLOGY AND ETIOLOGY ema, and cystic fibrosis. Anaerobes (Fusobacterium and Bacteroides
species) and streptococci are likely infecting pathogens in this situation,
Brain abscess is one of the most serious complications of head and neck as are Nocardia and Actinomyces species. Brain abscess may also occur
infections. Even in the antibiotic era, mortality from brain abscess was hematogenously from wound and skin infections, osteomyelitis, pelvic
not appreciably different from that in the era before antibiotics (about infection, cholecystitis, and other intra-abdominal infections. Another
30%-60%) until the past decade, when mortality decreased to between predisposing factor leading to hematogenously acquired brain abscess
0% and 24%. This improvement is likely due to recent developments is cyanotic congenital heart disease (accounting for 5%-15% of all brain
52
in diagnosis and treatment, which includes the availability of more abscess cases, with higher percentages in some pediatric series), most
effective antimicrobial therapy, new surgical techniques, and especially commonly due to tetralogy of Fallot and transposition of the great ves-
the availability of CT scanning, which allows for an improved mortality sels. Brain abscess is rare during bacterial endocarditis (<5% of cases in
related to earlier diagnosis and a more accurate method of postoperative most series), despite the presence of persistent bacteremia. Hereditary
follow-up. The incidence of neurologic sequelae in patients who survive hemorrhagic telangiectasia is a predisposing factor almost always
their brain abscess ranges from 20% to 70%; mortality rates are much observed in patients with coexisting pulmonary arteriovenous malfor-
higher (27%-85%) in those whose abscess is complicated by intraven- mations; perhaps it allows septic emboli to cross the pulmonary circula-
tricular rupture. 53 tion without capillary filtration. The risk of developing brain abscess in
Bacteria can reach the brain by several different mechanisms. The patients with hereditary hemorrhagic telangiectasia ranges from 5% to
factors predisposing to brain abscess and the etiologic agents in each 9%, and is 1000 times greater than in the general population. 52,55 Brain
circumstance are presented in Table 71-6. 52,54 The most common patho- abscesses have also developed after esophageal dilatation and sclerosing
genic mechanism of brain abscess formation is spread from a contiguous therapy for esophageal varices.

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