Antibiotic susceptibility profiles of gut Enterobacterales of breast-fed and formula-fed babies in Calabar, Nigeria

Antibiotic resistance in Enterobacterales poses significant threats to infant health, with feeding practices potentially influencing bacterial colonization patterns and resistance profiles. This study aimed to determine the prevalence and antibiotic susceptibility patterns of Enterobacterales in breast-fed versus formula-fed infants and assess multiple antibiotic resistance (MAR) indices. Bacterial isolates were collected from 240 infants categorized by feeding method. Antibiotic susceptibility testing was performed against six antibiotics (ampicillin, gentamicin, streptomycin, ceftazidime, sulfamethoxazole/trimethoprim, and augmentin). MAR indices were calculated for all isolates. Of 240 infants sampled, 38.3% harbored Enterobacterales, exclusively in formula-fed babies. Among formula-fed infants, 32% had mixed E. coli and Salmonella, 24% E. coli alone, and 20% Salmonella alone, while breast-fed babies showed only E. coli in 26.7%. Meconium samples yielded no pathogens. Breast-fed isolates demonstrated 100% resistance to ampicillin, sulfamethoxazole/trimethoprim, and augmentin, with highest sensitivity to streptomycin (68.8%). Formula-fed isolates showed universal ampicillin resistance in both E. coli and Salmonella, with moderate sensitivity to gentamicin and ceftazidime (54-67%). Formula-fed infants showed better sensitivity to gentamicin (77%) and streptomycin (70%). Mean MAR index was 0.7, with 100% of isolates exceeding 0.2 (0.8 breast-fed, 0.73 formula-fed). Formula-fed infants demonstrated higher Enterobacterales colonization with concerning multidrug resistance patterns. All isolates exhibited clinically significant MAR indices, indicating urgent need for antimicrobial stewardship in pediatric populations.