Reductions in neonatal listeriosis: "Collateral benefit" of Group B streptococcal prophylaxis?

Objectives: We tested the hypothesis that declines in Listeria monocytogenes in infants are related to declines in rates of early-onset Group B Streptococcus (GBS) infections associated with widespread prophylaxis using agents with Listeria activity. Methods: We performed a retrospective cohort analysis using a national administrative database Pediatric Health Information System (PHIS). We searched for ICD-codes for Listeriosis in infants <30 days old and for early-onset GBS infection of any kind in infants <5 days old during the study period. Results: We identified 183 cases of Listeriosis in infants <30 days in the PHIS database from 1992 to 2013. We noted a statistically significant decline in case rates over the years studied: 4.78 cases per 10,000 admissions (1992-1995) to 2.24 (1996-2002) to 1.31 from (2003-2013) (< 0.0001). Case rates of early-onset GBS dropped significantly over the study period: 30.10 cases per 1000 admissions (1992-1995) to 21.70 (1996-2002) to 18.57 (2003-2013) (< 0.0001). There was a statistically significant correlation between yearly rates of Listeriosis and early-onset GBS (rho: 0.53; p = 0.01). Conclusions: These results support the hypothesis of a "collateral benefit" to widespread GBS prophylaxis and further support the position that empiric antibiotic regimens for febrile infants may no longer require Listeria activity.