The use of lactic acid bacteria (LAB) in the fermentation process to produce fermented foods has a long history. Furthermore, LAB are beneficial microorganisms known for their health-promoting characteristics. During fermentation, LAB have the capacity to produce significant amounts of bioactive substances, such as peptides, bacteriocins, lactic acid, exopolysaccharides (EPSs), enzymes, and others. Lactococcus lactis as one of the best-known and well-characterized species of LAB serves as a model organism for studying LAB. For a very long time, L. lactis has been used in milk fermentation, both in well-monitored industrial settings and on a small scale in traditional operations. Furthermore, L. lactis is a vital microorganism in the dairy food fermentation industry due to its role in acidification, flavor development, and the creation of various dairy products, including cheese, fermented butter, and others. The novelty of this review is the comprehensive and organized presentation of the main benefits of the use of L. lactis in milk fermentation processes including technological and safety features relevant for the dairy industry, probiotic potential, the ability to produce bioactive compounds (e.g., bacteriocins, GABA), and the recent development of such bacteria research methods like whole genome sequencing (WGS).

Escherichia coli, a major opportunistic pathogen in chickens, poses a serious threat to poultry production and public health via potential zoonotic transmission of ESBL-producing strains. Therefore, this study aimed to emphasize broilers as early carriers of ESBL E. coli and provide deeper insights into antimicrobial resistance of these bacteria. Prevalence and antimicrobial resistance (MIC) testing of ESBL E. coli in cloacal and environmental samples from one-day-old and five-day-old broilers was conducted on three different growth cycles from a conventional poultry farm in Lithuania. Confirmed prevalence of ESBL E. coli in cloacal samples ranged from 0% to 57.5%, and in environmental swabs from 0% to 25%. All 102 ESBL E. coli isolates were susceptible to meropenem, imipenem, fosfomycin, and colistin. However, 93.14% of the strains were resistant to ceftriaxone (89.06–100%, depending on bacteria isolation source), 97.06% to ciprofloxacin (95.31–100%), and 66.67% to tetracycline (26.09–100%). Additionally, 80.39% of ESBL E. coli strains exhibited multidrug resistance. In total, 23 different antimicrobial resistance profiles were confirmed, with CRO/AMS/AUG/CIP/SXT/TE and CRO/CIP being the most common, detected in 18 of the 102 strains. The detection of widespread antimicrobial-resistant ESBL E. coli in five-day-old broilers emphasizes the need to implement control strategies early in the broiler production cycle.

Campylobacter jejuni is known as one of the main causative agents of gastroenteritis in humans worldwide, and the rise of antimicrobial resistance (AMR) in Campylobacter is a growing public health challenge of special concern. Whole-genome sequencing (WGS) was used to characterize genetic determinants of AMR in 53 C. jejuni isolates from dairy cattle, broiler products, wild birds, and humans in Lithuania. The WGS-based study revealed 26 C. jejuni AMR markers that conferred resistance to various antimicrobials. Genetic markers associated with resistance to beta-lactamases, tetracycline, and aminoglycosides were found in 79.3%, 28.3%, and 9.4% of C. jejuni isolates, respectively. Additionally, genetic markers associated with multidrug resistance (MDR) were found in 90.6% of C. jejuni isolates. The WGS data analysis revealed that a common mutation in the quinolone resistance-determining region (QRDR) was R285K (854G > A) at 86.8%, followed by A312T (934G > A) at 83% and T86I (257C > T) at 71.7%. The phenotypic resistance analysis performed with the agar dilution method revealed that ciprofloxacin (CIP) (90.6%), ceftriaxone (CRO) (67.9%), and tetracycline (TET) (45.3%) were the predominant AMR patterns. MDR was detected in 41.5% (22/53) of the isolates tested. Fifty-seven virulence genes were identified in all C. jejuni isolates; most of these genes were associated with motility (n = 28) and chemotaxis (n = 10). Additionally, all C. jejuni isolates harbored virulence genes related to adhesion, invasion, LOS, LPS, CPS, transportation, and CDT. In total, 16 sequence types (STs) and 11 clonal complexes (CC) were identified based on core-genome MLST (cgMLST) analysis. The data analysis revealed distinct diversity depending on phenotypic and genotypic antimicrobial resistance of C. jejuni.

Lactic acid bacteria (LAB) are essential in the production of fermented dairy products, contributing to desirable sensory attributes, safety, and shelf life. Traditionally, the health-promoting properties of fermented dairy products have been associated with live probiotic LAB; however, ensuring their viability during processing, storage and gastrointestinal passage remains challenging. This has shifted scientific interest toward postbiotics—preparations consisting of inactivated microbial cells, cell components and fermentation-derived metabolites capable of resulting in health benefits without the survival of microorganisms. LAB-derived postbiotics include bioactive peptides, exopolysaccharides and cell wall fragments, which may support gut barrier function, exert immunomodulatory or antimicrobial effects and improve technological performance in dairy matrices. Their stability, predictable functionality, and favourable safety profile make them suitable alternatives or supplements to traditional probiotics. In dairy applications, postbiotics can be produced in situ during fermentation or incorporated as formulated ingredients to enhance product functionality and deliver consistent bioactivity. In addition to highlighting the technological benefits of LAB-derived postbiotics in dairy systems and assessing new regulatory frameworks, this review summarizes the current understanding of their classification, composition, and mechanisms of action. Key challenges related to definition, standardization, safety assessment and labeling are discussed to support future development of postbiotic-enriched functional dairy foods.