Skip to Main Content

Chapter 6: Infectious Diseases

Sky Lee

COMMON ANTIBIOTICS

These classes of antibiotics are most commonly used to treat infectious diseases:

  • β-lactams include high-dose amoxicillin ± clavulanate, ampicillin ± sulbactam, and piperacillin + tazobactam (antipseudomonal); and cephalosporins such as ceftriaxone, cefotaxime, cefuroxime, and cefepime (antipseudomonal).

  • Fluorquinolones include ciprofloxacin, levofloxacin (antipseudomonal), gemifloxacin, and moxifloxacin.

  • Macrolides include azithromycin and clarithromycin (an erythromycin used less commonly and usually not as monotherapy for pneumonia).

  • Carbapenems include ertapenem, meropenem (antipseudomonal), imipenem ± cilastatin (antipseudomonal), and doripenem (antipseudomonal).

CENTRAL NERVOUS SYSTEM INFECTIONS

Acute Bacterial Meningitis

Meningeal infections are associated with profound inflammatory responses. Without treatment, mortality can be >50%. Survivors usually have severe morbidity. Typical bacterial pathogens include Streptococcus pneumoniae, Neisseria meningitidis, group B streptococci, and Listeria monocytogenes (Table 6.1).

image KEY FACT

The classic triad of bacterial meningitis consists of fever, altered mental status, and nuchal rigidity. Virtually all patients have at least one of these symptoms.

Table 6.1Causes and Treatment of Bacterial Meningitis
View Table||Download (.pdf)
Table 6.1 Causes and Treatment of Bacterial Meningitis
AGE/TREATMENT GROUP COMMON MICROORGANISMS EMPIRIC ANTIBIOTICS—FIRST CHOICE SEVERE PENICILLIN ALLERGY
<1 month of age Group B strep, E coli, Listeria Ampicillin and cefotaxime/gentamicin N/A
1 month to 50 years of age S pneumoniae, N meningitidis, H influenzaea Ceftriaxone/cefotaxime + vancomycin Aztreonam or carbapenemb + vancomycin
>50 years of age S pneumoniae, Listeria, gram-negative bacilli Ceftriaxone/cefotaxime + ampicillin + vancomycin Fluoroquinolone or aztreonam or carbapenemb (N meningitidis) + TMP-SMX (Listeria) + vancomycin
Impaired cellular immunity (or alcohol use disorder) S pneumoniae, L monocytogenes, gram-negative bacilli Ceftazidime or cefepime + ampicillin + vancomycin TMP-SMX + vancomycin
Postneurosurgery or post–head trauma S pneumoniae, S aureus, gram-negative bacilli (incl. Pseudomonas) Meropenem, cefepime, or ceftazidime + vancomycin Aztreonam or ciprofloxacin + vancomycin

Adapted with permission from Tierney LM, et al. Current Medical Diagnosis & Treatment, 44th ed. New York: McGraw-Hill, 2005:1251.

aH influenzae type B has greatly ↓ in pediatrics as a result of vaccination.

bAgent choice depends on patient age and clinical situation.

Symptoms/Exam

  • Symptoms include headache, photophobia, and nausea/vomiting. Neonates may present with fever or hypothermia and subtle signs, including lethargy, poor feeding, and/or bulging fontanelles.

  • Less common presentations are rash (Figure 6.1); cranial nerve palsies; cerebral involvement in the form of seizures, aphasia, or focal neurologic deficits (eg, syphilitic meningitis); and coma.

  • Traditional signs thought to correlate with meningeal irritation include Kernig sign (with the thigh and knee flexed, passive leg extension leads to pain) and Brudzinski sign (passive flexion of the neck leads to spontaneous flexion of the hip and knees). However, these signs are not sensitive for the diagnosis of bacterial meningitis.

  • Atypical presentations are common in neonates, infants, the elderly, and immunocompromised patients.

    ...

Pop-up div Successfully Displayed

This div only appears when the trigger link is hovered over. Otherwise it is hidden from view.

This site uses cookies to provide, maintain and improve your experience. MH Privacy Center Close