Title : Prevalence and antibiotic resistance patterns of gram-negative bacteria isolated from cosmetic products
Abstract:
The detection of antibiotic-resistant (ABR) Gram-negative bacteria in cosmetic products represents a growing concern for public health, particularly given the non-sterile nature of these widely used items. Cosmetics are frequently applied to the skin, mucous membranes, or hair, and although they are not expected to be sterile, they must comply with microbial contamination limits set by international regulatory bodies. The presence of antibiotic-resistant bacteria in such products not only poses a direct risk of infection to users—especially those who are immunocompromised or have open wounds—but also creates a potential reservoir for resistance genes, contributing to the broader challenge of antimicrobial resistance (AMR). This study aimed to evaluate the microbiological quality of cosmetic products, with a specific focus on isolating Gram-negative bacteria and assessing their resistance patterns to commonly used antibiotics. A total of 21 bacterial isolates were recovered from cosmetic and mouthwash samples collected between 2019 and 2025. Using ISO 21149:2017 and ISO 22717:2015 methodologies, the study identified four Gram-negative bacterial genera: Pseudomonas aeruginosa (57%), Burkholderia cepacia complex (19%), Enterobacter spp. (14%), and Pluralibacter gergoviae (10%). Antibiotic susceptibility testing using the VITEK 2 Compact System revealed a range of resistance profiles. Notably, all B. cepacia complex isolates (100%) exhibited resistance to four antibiotics, indicating a strong multidrug-resistant (MDR) profile. In contrast, P. aeruginosa and Enterobacter spp. displayed limited resistance, and P. gergoviae showed no detectable resistance. The findings highlight the possible role of preservatives in creating selective pressure that contributes to resistance development, particularly when preservatives are used at sub-inhibitory concentrations or in products with frequent exposure to external contaminants. These results align with prior studies reporting preservative-resistant and antibiotic-resistant bacteria in cosmetic formulations, suggesting an urgent need for more stringent microbiological control practices. The heterogeneity of resistance patterns across different bacterial genera also underscores the complexity of microbial contamination and resistance dynamics in non-sterile products. Overall, this study emphasizes the critical need for routine surveillance of microbial contaminants in cosmetics, optimization of preservative systems, and the integration of rapid detection tools. These steps are essential not only for ensuring consumer safety but also for addressing the broader implications of AMR in everyday consumer products.
