Introduction: Infant feeding represents a critical developmental stage during which exposure to pathogenic microorganisms can pose serious health risks. The World Health Organization recommends exclusive breastfeeding for the first six months, followed by diversified feeding for up to 24 months. However, infant food products such as fruit compotes and powdered milk may serve as suitable media for the growth of pathogens, particularly Staphylococcus aureus.

Staphylococcus aureus is a foodborne pathogen capable of producing heat-stable enterotoxins and forming biofilms, which enhance its persistence and resistance in food processing environments. This study aimed to isolate and identify S. aureus from commercial infant foods and evaluate its biofilm-forming ability.

Methods: Three powdered milk samples and three fruit compote samples marketed in Tlemcen, Algeria, were analyzed. Serial decimal dilutions were plated on Baird-Parker and Chapman agar for enumeration. Isolates were identified through Gram staining and biochemical tests (catalase, oxidase, coagulase, hemolysis). Biofilm formation was assessed on Congo Red agar, microtiter plates, and glass surfaces at room temperature over incubation periods of 1, 1.5, 2, 2.5, 3, and 24 hours.

Results: Microbiological analysis revealed contamination levels of up to 14.36 × 10³ CFU/ml in fruit compotes and 22.45–40.09 × 10³ CFU/g in powdered milk. Biochemical testing confirmed the presence of S. aureus. All strains tested positive on Congo Red agar, indicating exopolysaccharide production. Most isolates exhibited weak to moderate biofilm formation, while strain 3 (from powdered milk sample 3) showed strong biofilm maturity (OD = 0.325) and notable adhesion to glass, suggesting potential for surface colonization.

Conclusion: These findings underscore the microbiological risk associated with infant foods and highlight the importance of stringent hygiene practices, microbial monitoring, and targeted biofilm control in food processing environments.