Lactobacillus species are widely used as probiotics and starter cultures for a variety of foods, supported by a long history of safe usage. Although more than 35 species meet the European Food Safety Authority (EFSA) criteria for qualified presumption of safety status, the safety of Lactobacillus species and their carriage of antibiotic resistance (AR) genes is under continuing ad hoc review. To comprehensively update the identification of AR in the genus Lactobacillus, we determined the antibiotic susceptibility patterns of 182 Lactobacillus type strains and compared these phenotypes to their genotypes based on genome-wide annotations of AR genes. Resistances to trimethoprim, vancomycin, and kanamycin were the most common phenotypes. A combination of homology-based screening and manual annotation identified genes encoding resistance to aminoglycosides (20 sequences), tetracycline (18), erythromycin (6), clindamycin (60), and chloramphenicol (42). In particular, the genes aac(3) and lsa, involved in resistance to aminoglycosides and clindamycin, respectively, were found in Lactobacillus spp. Acquired determinants predicted to code for tetracycline and erythromycin resistance were detected in Lactobacillus ingluviei, Lactobacillus amylophilus, and Lactobacillus amylotrophicus, flanked in the genome by mobile genetic elements with potential for horizontal transfer. IMPORTANCE Lactobacillus species are generally considered to be nonpathogenic and are used in a wide variety of foods and products for humans and animals. However, many of the species examined in this study have antibiotic resistance levels which exceed those recommended by the EFSA, suggesting that these cutoff values should be reexamined in light of the genetic basis for resistance discussed here. Our data provide evidence for rationally revising the regulatory guidelines for safety assessment of lactobacilli entering the food chain as starter cultures, food preservatives, or probiotics and will facilitate comprehensive genotype-based assessment of strains for safety screening.

Biofilms are sessile communities of bacteria typically embedded in an extracellular polymeric matrix. Bacterial cells embedded in biofilms are inherently recalcitrant to antimicrobials, compared to cells existing in a planktonic state, and are notoriously difficult to eradicate once formed. Avenues to tackle biofilms thus far have largely focussed on attempting to disrupt the initial stages of biofilm formation, including adhesion and maturation of the biofilm. Such an approach is advantageous as the concentrations required to inhibit formation of biofilms are generally much lower than removing a fully established biofilm. The crisis of antibiotic resistance in clinical settings worldwide has been further exacerbated by the ability of certain pathogenic bacteria to form biofilms. Perhaps the most notorious biofilm formers described from a clinical viewpoint have been methicillin-resistant Staphylococcus aureus (MRSA), Staphylococcus epidermidis, Pseudomonas aeruginosa, Gardnerella vaginalis and Streptococcus mutans, the latter of which is found in oral biofilms. Due to the dearth of novel antibiotics in recent decades, compounded by the increasing rate of emergence of resistance amongst pathogens with a propensity for biofilm formation, solutions are urgently required to mitigate these crises. Bacteriocins are a class of antimicrobial peptides, which are ribosomally synthesised and often are more potent than their antibiotic counterparts. Here, we review a selection of studies conducted with bacteriocins with the ultimate objective of inhibiting biofilms. Overall, a deeper understanding of the precise means by which a biofilm forms on a substrate as well as insights into the mechanisms by which bacteriocins inhibit biofilms is warranted.