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ID Consult

Uptick in adult syphilis means congenital syphilis may be lurking

Publish date: December 17, 2018

More than 1 day of missed therapy requires restarting a new 10-day course. Use of other antimicrobial agents (such as ampicillin) is not validated, so any empiric ampicillin initially given for possible sepsis does not count toward the 10-day penicillin regimen. If nonpenicillin drugs must be used, close serologic follow-up must occur to ensure adequacy of response to therapy.

Possible syphilis

There are three alternative regimens, the same two as in proven/highly probable syphilis (above) plus a single-dose option

A. Aqueous crystalline penicillin G, as described above.

B. Procaine penicillin G, as described above.

C. Benzathine penicillin G at 50,000 U/kg per dose intramuscularly in a single dose.

Note: To be eligible for regimen C, an infant must have a complete evaluation that is normal (cerebrospinal fluid [CSF] examination, long-bone radiographs, and complete blood count with platelet count) and follow-up must be assured. Exception: Neonates born to mothers with untreated early syphilis at the time of delivery are at increased risk for congenital syphilis, and the 10-day course of penicillin G may be considered even if the complete evaluation is normal and follow-up is certain.

Less likely syphilis

One antibiotic regimen is available, but no treatment also may be an option.

A. Benzathine penicillin G as described above.

B. If mother’s NTT has decreased at least fourfold after appropriate early syphilis therapy or remained stably low, which indicates latent syphilis (VDRL less than 1:2; RPR less than 1:4), no treatment is an option but requires repeat serology every 2-3 months until infant is 6 months old.

Unlikely syphilis

No treatment is recommended unless follow-up is uncertain, in which case it is appropriate to give the infant benzathine penicillin G as described above.

Infant with positive NTT at birth

All neonates with reactive NTT need careful follow-up examinations and repeat NTT every 2-3 months until nonreactive. NTT in infants who are not treated because of less likely or unlikely syphilis status should drop by 3 months and be nonreactive by 6 months; this indicates NTT was passively transferred maternal IgG. If NTT remains reactive at 6 months, the infant is likely infected and needs treatment. Persistent NTT at 6-12 months in treated neonates should trigger repeat CSF examination and infectious diseases consultation about a possible repeat of the 10-day penicillin G regimen. If the mother was seroreactive, but the newborn’s NTT was negative at birth, testing of the infant’s NTT needs repeating at 3 months to exclude the possibility that the congenital syphilis was incubating when prior testing occurred at birth. Note: Treponemal-specific tests are not useful in assessing treatment because detectable maternal IgG treponemal antibody can persist at least 15 months.

Neonates with abnormal CSF at birth

Repeat cerebrospinal fluid evaluation every 6 months until results normalize. Persistently reactive CSF VDRL or abnormal CSF indexes not caused by another known cause requires retreatment for possible neurosyphilis, as well as consultation with an expert.

Summary

Decisions on managing infants of mothers with positive syphilis testing can be difficult. NTT are the essential test for newborns and some degree of laboratory or imaging work up often are needed. Consider consulting an expert in infectious diseases and/or perinatology if the gray areas do not readily become clear. Treatment of the correct patients with the right drug for the right duration remains the goal, as usual.

Dr. Harrison is a professor of pediatrics at University of Missouri-Kansas City and Director of Research Affairs in the pediatric infectious diseases division at Children’s Mercy Hospital – Kansas City. He said he had no relevant financial disclosures. Email him at pdnews@mdedge.com.