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Detection of group B streptococcal bacteremia in simulated intrapartum antimicrobial prophylaxis
Katherine K Hsu1, Stephen I Pelton, Daniel S Shapiro
1Maxwell Finland Laboratory for Infectious Diseases, Boston University School of Medicine and Boston Medical Center, Boston, MA, 02118, USA. khsu@bu.edu
The diagnostic value of negative blood cultures from neonates whose mothers receive intrapartum antimicrobial prophylaxis for prevention of perinatal group B streptococcal disease is uncertain. We investigated whether blood culture medium containing resin designed to adsorb antibiotic improved group B streptococcal detection following simulated intrapartum antimicrobial prophylaxis. Group B streptococcus (Streptococcus agalactiae) was preincubated with varying antibiotic concentrations before inoculation into BACTEC Peds Plus resin-containing medium, BACTEC Standard, or Trek ESP 80A. In the presence of 10 mcg/mL ampicillin, detection of both low (<500 CFU/mL) and high (>500 CFU/mL) S. agalactiae inocula ranged between 75-100% of resin-containing medium bottles; detection rates in both non-resin-containing media were lower. When S. agalactiae was detected, it was detected sooner with resin-containing medium. The addition of gentamicin to ampicillin did not affect sensitivity of resin-containing medium for S. agalactiae. In our model, resin-containing medium more consistently and more rapidly detected S. agalactiae than did either of two non-resin-containing media, in the presence of antibiotic levels likely present in fetal sera following intrapartum antimicrobial prophylaxis.
The diagnostic value of negative blood cultures from neonates whose mothers receive intrapartum antimicrobial prophylaxis for prevention of perinatal group B streptococcal disease is uncertain. We investigated whether blood culture medium containing resin designed to adsorb antibiotic improved group B streptococcal detection following simulated intrapartum antimicrobial prophylaxis. Group B streptococcus (Streptococcus agalactiae) was preincubated with varying antibiotic concentrations before inoculation into BACTEC Peds Plus resin-containing medium, BACTEC Standard, or Trek ESP 80A. In the presence of 10 mcg/mL ampicillin, detection of both low (<500 CFU/mL) and high (>500 CFU/mL) S. agalactiae inocula ranged between 75-100% of resin-containing medium bottles; detection rates in both non-resin-containing media were lower. When S. agalactiae was detected, it was detected sooner with resin-containing medium. The addition of gentamicin to ampicillin did not affect sensitivity of resin-containing medium for S. agalactiae. In our model, resin-containing medium more consistently and more rapidly detected S. agalactiae than did either of two non-resin-containing media, in the presence of antibiotic levels likely present in fetal sera following intrapartum antimicrobial prophylaxis.