Evolving Antibiotic Resistance in Group B Streptococci Causing Invasive Infant Disease: 1970 – 2021

BACKGROUND: We sought to define the frequency of antibiotic resistance over time in a collection of invasive GBS isolates derived from infant early onset disease (EOD), late onset disease (LOD), and late-late onset disease (LLOD). METHODS: A multicenter retrospective review of infants born from 1970–2021 with GBS isolated from blood, cerebrospinal fluid, synovial fluid, cellulitis, or bone. All isolates were serotyped and antimicrobial susceptibility testing performed using disk diffusion. RESULTS: The most common serotypes in our 2017 isolates were III (n=1112, 55.1%), Ia (n=445, 22%), Ib (n=182, 9%) and II (n=146, 7.2%). A total of 945 (46.8%) isolates were from infants with EOD, 976 (48.3%) from LOD and 96 (4.75%) from LLOD. All isolates were penicillin susceptible. Compared to strains isolated < 2000, strains isolated ≥ 2000 showed significantly greater frequency of erythromycin (4.0% to 32.3%, P<0.0001) and clindamycin (1.5% to 17.5%, P<0.0001) resistance. Year of isolation (≥ 2000) and serotype V were significantly associated with erythromycin and/or clindamycin resistance. CONCLUSIONS: We document a rapid and significant increase in clindamycin and erythromycin resistance. As clindamycin may be considered in severely penicillin-allergic women needing GBS intrapartum prophylaxis, obstetricians, pediatricians and neonatologist should be aware of this disturbing trend.