Medication Summary
Typically, a clinician chooses an antibiotic before synovial fluid culture results are known. Thus, the child's age and risk factors, as well as Gram stain results, should influence initial antibiotic coverage. Neonates are at risk for infection with gram-positive organisms, such as S aureus or group B streptococci, and gram-negative organisms, such as E coli.
For neonates without meningitis, a semisynthetic penicillin (eg, oxacillin) plus an aminoglycoside (eg, gentamicin) may be used. Neonates with concomitant meningitis and septic arthritis (SA) present a therapeutic challenge. Oxacillin does not penetrate the blood-brain barrier well, and ampicillin, although it offers better cerebrospinal fluid levels, does not provide adequate coverage against S aureus. In this case, a combination of vancomycin and a third-generation cephalosporin, such as ceftriaxone, is a reasonable choice for initial coverage.
S aureus is the most common cause of SA among nonneonates. Oxacillin alone should provide adequate coverage in older children who are immunocompetent, assuming that they are immunized for H influenzae type B. However, in communities in which MRSA-CA is prevalent, clindamycin is a better initial choice. A third-generation cephalosporin is the initial therapy for an adolescent possibly infected with gonococcus.
Once culture results and sensitivities are known, antibiotic selection can be more specific. For example, a child with group A beta hemolytic streptococcus (GABHS) infection could be treated with penicillin, whereas one growing anaerobes requires clindamycin.
Antibiotics
Class Summary
Empiric antimicrobial therapy must be comprehensive and should cover all likely pathogens in the context of the clinical setting.
Oxacillin (Bactocill in dextrose)
Oxacillin is a semisynthetic penicillin that is effective against staphylococci.
Gentamicin
Gentamicin is an aminoglycoside with good gram-negative activity. Dosing regimens are numerous; adjust the dose based on CrCl and changes in the volume of distribution.
Ceftriaxone (Rocephin)
Ceftriaxone is a third-generation cephalosporin with broad-spectrum, gram-negative activity. It has lower efficacy against gram-positive organisms and higher efficacy against resistant organisms. Ceftriaxone arrests bacterial growth by binding to 1 or more penicillin-binding proteins.
Penicillin G potassium (Pfizerpen)
This agent is active against most gram-positive organisms except S aureus, as well as some anaerobes. It interferes with the synthesis of cell wall mucopeptide during active multiplication, resulting in bactericidal activity against susceptible microorganisms.
Clindamycin (Cleocin)
Clindamycin is active against most gram-positive organisms and anaerobes. It inhibits bacterial growth, possibly by blocking dissociation of peptidyl transfer ribonucleic acid (t-RNA) from ribosomes, in that way causing RNA-dependent protein synthesis to arrest.
Vancomycin (Vancocin, Vancoled)
Vancomycin is used for the treatment of infections due to suspected or documented MRSA and for the treatment of serious or life-threatening infections due to S aureus.
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Emergency room photograph of an infant with septic arthritis of the left hip. The child holds his hip rigidly in the classic position of flexion, abduction, and external rotation, a position that maximizes capsular volume. The patient is relatively comfortable as long as the hip joint remains immobile in this position.
