Clinical Features, Diagnosis, And Management - Infections of the Fetus and Newborn

CLINICAL FEATURES, DIAGNOSIS, AND MANAGEMENT

Acute Bacterial Sepsis

When a physician first encounters a sick newborn, the primary concern is whether the illness represents sepsis and/or meningitis caused by bacteria. This determination is important, because treatment is both feasible and extremely urgent. Clinical disease ap-parent at birth or developing within the first 3 days of life (early onset) has usually been acquired prenatally. Mortality can exceed 70%, even with prompt treatment. Later onset of symptoms is commonly associated with natal or postnatal acquisition of pathogens; however, these infections can also be severe. If meningitis develops, the overall mortality, even with treatment, ranges from 10 to 25%, and permanent neurologic damage may oc-cur in 30 to 50% of survivors. The two pathogens most commonly associated with neona-tal sepsis and meningitis are group B streptococci andE. coli.

The diagnosis of neonatal infections is based first on clinical suspicion. There is sometimes a history of recent maternal febrile illness immediately before or at birth. Other suggestive features include fetal distress, prolonged rupture of membranes (>12 hours), foul-smelling amniotic fluid, and premature delivery. The first signs and symp-toms of illness in the infant may be subtle and extremely variable, including respiratory distress, apneic episodes, cyanosis, irritability, unexplained jaundice, tachycardia, poor feeding, abdominal distention, and fever. Initial laboratory findings often include either leukocytosis, with an increased proportion of immature neutrophils, or leukopenia. The development of seizures, hypotension, or disseminated intravascular coagulation indicates a particularly grave prognosis.

Diagnostic tests for suspected infections must be initiated as quickly as possible, fol-lowed by empirical antimicrobial therapy while waiting for culture results. The major tests include examination and culture of cerebrospinal fluid and blood culture. The an-timicrobics initially chosen are those known to be effective against the pathogens most commonly encountered. They often include ampicillin for the streptococci (also useful for L. monocytogenes) and an aminoglycoside such as gentamicin for E. coli.

Other Bacterial and Chlamydial Infections

Although N. gonorrhoeae and C. trachomatis are common natally acquired infections, they are usually not associated with sepsis. Both can produce a severe conjunctivitis in the newborn that requires prompt diagnosis and treatment. Gonococcal ophthalmia is usu-ally apparent in the first 5 days after birth, whereas the onset of chlamydial conjunctivitis is frequently delayed until after the first week of life. Another significant illness associ-ated with natally acquired C. trachomatis infection is infant pneumonia syndrome. The onset of respiratory symptoms is often delayed, with most cases occurring between 2 weeks and 6 months of age.

Localized infections, such as cutaneous or subcutaneous abscesses, show a particular association with postnatally acquired S. aureus and occasionally with various Gram-negative bacteria. If the newborn is affected by a staphylococcal strain that produces ex-foliative toxin, the local lesion may be relatively trivial in contrast to the more widespread effect of circulating toxin on the skin, which is termed staphylococcal scalded skin syn-drome. Prompt treatment with an antistaphylococcal antimicrobial agent results in reso-lution of the disease within 2 weeks, usually with complete healing.

Syphilis

If prenatal infection by Treponema pallidum (congenital syphilis) is left untreated, the result can be long-term damage, often without apparent signs or symptoms in the newborn period. To minimize these risks, serologic screening is recommended for all pregnant women when first seen in early gestation and at delivery. In addition, serologic testing is recommended whenever clinical or epidemiologic circumstances suggest the possibility of exposure at any time during pregnancy. Prompt treatment of infected mothers during pregnancy, preferably with penicillin, markedly reduces the risk of fetal infection. Similar treatment is also effec-tive for the infected infant.