Human milk antibiotic residue levels and their relationship with delivery mode, maternal antibiotic use and maternal dietary habits.

OBJECTIVE: It is important to identify undesirable toxins and metabolites present in human milk that may be passed on to nursing infants. Such residues may derive from the antibiotics that are widely used to treat infectious diseases in both humans and food-producing animals. To the best of our knowledge, there are no reports in the literature on human milk antibiotic residue levels.

PATIENT AND METHODS: As a part of the Human Milk Artificial Pollutants (HUMAP) study, we aimed to evaluate human milk antibiotic residues among mothers with 7 to 90-day-old babies. Pregnant women who had received antibiotic treatment during pregnancy were excluded. The use of antibiotic prophylaxis with cefazoline sodium during labor was noted among the study subjects. Human milk antibiotic residues were evaluated with the InfiniPlex for Milk Array (Randox Laboratories, London, United Kingdom), a semi-automated system with a multi-array biochip designed to detect antibiotic residues and toxins.

RESULTS: The HUMAP study included 83 mothers, ranging in age from 17 to 41 years (mean 29.7 ± 6.2 years). Of these, 59% received cefazoline sodium shortly after birth, while 41% did not receive any antibiotics during the pregnancy, delivery or lactational periods. Testing revealed that 71/83 (85.5%) human milk samples were positive for beta-lactams and 12 (14.5%) samples were positive for quinolones. There was no difference in maternal age, gestational week, delivery type, sampling time, maternal dietary habits between the mothers with quinolones or beta-lactam residues in their milk and those without (p > 0.05 for both). Beta-lactam and quinolone residues were detected in 85.7% and 23.5%, respectively, of the human milk samples of mothers who did not receive antibiotics at birth and/or during the first seven days after birth.

CONCLUSIONS: We found that the majority of human milk samples included beta-lactams or quinolones, even though the mothers did not receive these antibiotics during pregnancy and lactation. Antibiotic residues in human milk may affect early maintenance of the intestinal microbiota. Previous studies have shown that antimicrobials in food might increase the risks of allergies and could lead to the development of antibiotic-resistant bacterial strains. Effective policies on food safety and appropriate antibiotic use during pregnancy and lactation are needed.