Antimicrobial activity in cord blood units: occurrence and levels of antibiotics.

Background: Antibiotic prophylaxis treatment at delivery is highly recommended for reducing the risk of infection for mothers positive for group B streptococcus. It is therefore expected that some cord blood (CB) products will contain residual antibiotics. This study aimed to determine the incidence and level of β-lactam antibiotics in CB products.

Study Design And Methods: The antimicrobial activity of 60 CB plasma by-products was evaluated using disk diffusion assays on 10 bacteria species. Plasma samples showing antimicrobial activity were either treated with β-lactamase enzyme to inhibit β-lactam antibiotics or heated to 56°C for 30 minutes to inhibit complement proteins. β-Lactam antibiotic concentrations were determined by comparison with a standard curve obtained with known concentrations of antibiotics.

Results: Antimicrobial activity against mostly Gram-positive microorganisms was observed in 33% of CB units. The β-lactamase enzyme abolished the antimicrobial activity in the majority of these CB products. Up to 5 μg/mL penicillin and 14 μg/mL ampicillin were measured in these products.

Conclusion: Approximately one-third of CB products contain significant amounts of plasma with residual antibiotics, which can affect the survival and growth of bacterial contaminants when performing the sterility test and potentially lead to false-negative results. Additional work is required to better understand whether residual antibiotics in CB affect penicillin-allergic patients.