New Study Shows How Gender Affects Gut Antibiotic Resistance Globally

New Delhi: A new global study led by researchers from the University of Turku in Finland has found that antibiotic resistance in the human gut varies by gender and country income levels. The study, published on May 19, 2025, in the journal npj Biofilms and Microbiomes, analyzed over 14,600 gut metagenomes (genetic material from gut microbes) collected from people across 32 countries.

The research team, led by Professor Leo Lahti, focused on differences in antibiotic resistance genes (ARGs)—the genes that make bacteria resistant to antibiotics. One of the key findings was that in high-income countries (HICs), women had about 9% more antibiotic resistance genes in their gut microbiomes compared to men. This may be due to higher antibiotic exposure, increased contact with resistant bacteria, or biological factors that make women more likely to carry these bacteria.

On the other hand, in low- and middle-income countries (LMICs), men had a higher ARG load than women. However, the researchers noted that this difference became less significant when factors like age, lifestyle, and environmental conditions were taken into account. Interestingly, gender differences in resistance patterns only appeared in adults, not in children, suggesting that adult behaviors, healthcare access, or biological differences play a bigger role.

Postdoctoral researcher Katariina Pärnänen explained:

"This suggests that lifestyle, biological differences, or healthcare-related factors may influence these differences more in adulthood than in childhood."

The study also found that women in high-income countries had a slightly greater variety of resistance genes, indicating a wider range of antibiotic resistance in their gut bacteria.

Beyond gender, the researchers discovered that age and country of residence strongly influenced antibiotic resistance. Infants and elderly people showed the highest resistance gene loads and diversity. Regions with high antibiotic use—particularly in lower-income settings—showed greater resistance, likely due to poor sanitation, hygiene issues, and overuse of antibiotics.

The authors believe these findings can help shape more effective, gender-sensitive, and region-specific strategies to combat the growing global health threat of antibiotic resistance.

As Pärnänen concluded:

"Understanding gender differences in antibiotic resistance is key to designing equitable and effective healthcare interventions. Our study will lay the groundwork for further research to reduce health inequalities related to antibiotic resistance."