Acquired antibiotic resistance: are we born with it?

Area of Science:

• Microbiology
• Public Health
• Genetics

Background:

• Antibiotic resistance (AR) is a growing global health threat.
• Foodborne antibiotic-resistant (ART) bacteria may spread to humans through diet.
• Understanding the baseline AR in the human gut is crucial for assessing risks.

Purpose of the Study:

• To investigate the early development of antibiotic-resistant bacteria in infant gut microbiota.
• To determine the baseline prevalence of AR in infants without prior antibiotic exposure.
• To identify potential sources and drivers of early AR in the human gut.

Main Methods:

• Analysis of gut microbiota in 16 infants from birth to 1 year.
• Subjects were fed breast milk and/or infant formula, with no antibiotic exposure.
• Detection of antibiotic resistance genes and identification of bacterial species carrying them.

Main Results:

• Predominant antibiotic-resistant bacteria and multiple resistance genes were found in infant guts within the first week of life.
• ART populations shifted without antibiotic or dietary changes.
• Specific AR genes (tet(M), ermB, sul2, bla(TEM)) and carriers (Enterococcus, Staphylococcus, Klebsiella, Streptococcus, E. coli/Shigella) were identified.
• ART bacteria were not found in infant foods, but some breast milk samples contained skin-associated ART bacteria.

Conclusions:

• Early development of AR in the infant gut is independent of direct antibiotic exposure.
• Maternal and environmental microbial exposure appears to significantly impact early AR.
• ART populations can amplify within the host gut even without antibiotic selective pressure.