# The Invisible Threat of Antibiotic Resistance in Food
## 3 Antibiotic Resistance in Traditional Foods
### Antibiotic Resistance in Dairy/Fermented Foods  
Antibiotic Resistance of LAB in Fermented Dairy Products  
Lactic acid bacteria are Gram-positive, non-spore forming, catalase-negative, acid-tolerant, aerotolerant, usually non-motile cocci or rods (_Lactiplantibucillus_, _Lactobacillus_, _Enterococcus_, _Streptococcus_, _Leuconostoc_, _Weisella_, _Pediococcus_, _Lactococcus_, etc.). LAB constitute the most crucial microorganisms in fermented foods, such as yogurts, cheeses, and salami. The current trends in the food industry and the growing demand for healthy foods have led to the development of fermented dairy foods that provide health-promoting antimicrobial metabolites, prebiotic substances, diverse probiotic bacteria with immune system stimulating effects, unique flavors, and nutritional benefits shaped by regional ingredients and processing methods [207; 208]. Different LAB and bifidobacteria are used as starter cultures and probiotics to create fermented functional foods and remain active in the product, interacting with microbiota and intestinal wall cells during transit [209]. When employed as protective cultures, the antimicrobial metabolites they produce (such as bacteriocins, organic acids, and H\({}_{2}\)O\({}_{2}\)) are utilized for their effectiveness against the spoilage-causing and pathogenic microorganisms (such as _L. monocytogenes_, _Cistridium_, and _Bacillus_ species) present in food [210; 211; 212; 213]. As bioprotective cultures, they are regarded as an alternative to antibiotics in animal production, due to their impact on pH and ability to act as antimicrobial agents in inhibiting zoonotic pathogens [214; 215]. While LAB are recognized as safe and widely used in food and fermented products, they have the potential to harbor antibiotic-resistant genes, colonize the intestine, and facilitate horizontal transferring of these genes to commensal and pathogenic bacteria in the food chain; therefore, they are considered as \"reservoirs\" of ARGs [216; 217; 218; 219; 220]. Fermented foods contain significant amounts of LAB, leading to their high consumption by consumers. LAB in the human gut have the potential to share genetic components with other nearby microbes [221; 222]. Physical proximity of bacteria in the gut invariably raises the likelihood of HGT [223; 224; 225]. This probability is elevated even further when antibiotic resistance genes are on MGEs, such as on plasmids [218]. Thus, LAB can act as a source of environmental antibiotic resistance genes [224; 226]. Wild-type LAB strains and commercial starters both contribute to ARG dissemination throughout the food chain. The latter's impact was initially documented by [PERSON] et al. in 2005 [227]. Since then, multiple publications have demonstrated that GRAS strains, such as those used in food starters, are capable of acquiring antibiotic resistance determinants and transferring them to other strains [228]. [PERSON] et al. [229] reported the in vivo transfer of wild-type antibiotic resistance plasmids from _Lactiplantiobacillus plantarum_ (formerly _Lactobacillus plantarum_), which were isolated from fermented dry sausage, to _Enterococcus faecalis_ into JH2-2, a natural inhabitant of the human gut. The transfer of resistance genes between commercial strains and commensal gut bacteria in vitro and in vivo was confirmed by other studies [226; 228; 229; 230; 231; 232]. [PERSON] et al. [224] presented evidence of the transfer of the erythromycincis resistance gene from _Lactiplantiobacillus plantarum_ (formerly _Lactobacillus plantarum_) and _Lactiplantiobacillus brevis_ (formerly _Lactobacillus brevis_) to _Enterococcus faecalis_. From this, it can be inferred that fermented dairy products can also serve as a possible medium for antibiotic-resistant bacteria to enter into the human body. Recently, it was demonstrated that in addition to commensal LAB strains showing single or multiple antibiotic resistance, resistance genes were also reported in probiotic GRAS strains [219].