Whole Genome Sequencing of the Novel Probiotic Strain Lactiplantibacillus plantarum FCa3L.

Lactiplantibacillus plantarum is best known for its significant adaptive potential and ability to colonize different ecological niches. Different strains of L. plantarum are widely used as probiotics. To characterize the probiotic potential of the novel L. plantarum FCa3L strain isolated from fermented cabbage, we sequenced its whole genome using the Illumina MiSeq platform. This bacterial isolate had a circular chromosome of 3,365,929 bp with 44.3% GC content and a cyclic phage phiX174 of 5386 bp with 44.7% GC content. The results of in vitro studies showed that FCa3L was comparable with the reference probiotic strain L. plantarum 8PA3 in terms of acid and bile tolerance, adhesiveness, H2O2 production, and acidification rate. The strain 8PA3 possessed higher antioxidant activity, while FCa3L demonstrated superior antibacterial properties. The antibiotic resistance of FCa3L was more relevant to the probiotic strain than that of 8PA3, although a number of silent antibiotic resistance genes were identified in its genome. Genomic evidence to support adhesive and antibacterial properties, biosynthesis of bioactive metabolites, and safety of FCa3L was also presented. Thus, this study confirmed the safety and probiotic properties of L. plantarum FCa3L via complete genome and phenotype analysis, suggesting its potential as a probiotic, although further in vivo investigations are still necessary.

Alarming Antibiotic Resistance of Lactobacilli Isolated from Probiotic Preparations and Dietary Supplements.

In this study, we screened eight commercially available brands of Lactobacillus-containing probiotic preparations and dietary supplements for resistance towards commonly administered antibiotics of different classes. According to disc diffusion results, most of the isolates were resistant to vancomycin and susceptible to penicillin-type antibiotics (ampicillin and amoxicillin), carbapenems (imipenem, meropenem, and ertapenem), and inhibitors of protein synthesis (chloramphenicol, erythromycin, tetracycline, clarithromycin, and linezolid). However, based on minimum inhibitory concentration (MIC) values, six strains were reconsidered as resistant to tetracycline. All tested lactobacilli were resistant towards amikacin, ciprofloxacin, and norfloxacin. Resistance to cephalosporins was highly variable and decreased in the following order: ceftazidime/cefepime, ceftriaxone, cefotaxime, cefazolin, and cefoperazone. PCR screening for antibiotic resistance determinants in probiotic lactobacilli revealed a wide occurrence of vancomycin resistance gene vanX, ciprofloxacin resistance gene parC, and extended-spectrum ß-lactamase gene blaTEM. We also detected the tetK gene for tetracycline resistance in one isolate. Additionally, we identified discrepancies between the claims of the manufacturers and the identified species composition, as well as the enumerated amount of viable bacteria, for several products. The results of this study raise concerns about the safety of lactobacilli for human consumption as probiotics, as they may act as reservoirs of transferable antibiotic resistance genes.

Newly isolated lactic acid bacteria from silage targeting biofilms of foodborne pathogens during milk fermentation.

BACKGROUND: Raw milk, meat and plant materials are subjected to high risks of contamination by various pathogenic bacteria and thus their growth prevention is a great challenge in the food industry. Food fermentation by lactic acid bacteria (LAB) besides changing its organoleptic characteristics also helps to eliminate unfavorable microflora and represses growth of pathogens. To the date only few LABs has been reported to exhibit activity against bacteria embedded in the biofilms characterized by extreme resistance to antimicrobials, high exchange rate with resistance genes and represent high risk factor for foodborne disease development. RESULTS: Six novel LAB strains isolated from the clover silage exhibited pronounced antibacterial activity against biofilm embedded pathogens. We show explicitly that these strains demonstrate high acidification rate, completely repress the growth of E. coli, S. aureus and to a lesser extent P. aeruginosa as well as exhibit appropriate probiotic and milk-fermenting properties. Moreover, in contrast to the approved probiotic strain Lactobacillus plantarum 8PA3, the new isolates were able to efficiently eradicate preformed biofilms of these pathogens and prevent bacterial spreading originating from the biofilm. We suggest these strains as potential additives to the pre-cultures of conventional LAB strains as efficient tools targeting foodborne pathogens in order to prevent food contamination from either seeded raw material or biofilm-fouled equipment. CONCLUSIONS: The AG10 strain identified as L. plantarum demonstrate attractive probiotic and milk fermentation properties as well as high resistance to simulated gastric conditions thus appearing perspective as a starter culture for the prevention of bacterial contamination originating from fouled equipment during milk fermentation.

Antibiotic Resistance of LACTOBACILLUS Strains.

The study provides phenotypic and molecular analyses of the antibiotic resistance in 20 Lactobacillus strains including 11 strains newly isolated from fermented plant material. According to the results of disc diffusion method, 90% of tested lactobacilli demonstrated sensitivity to clindamycin and 95% of strains were susceptible to tetracycline, erythromycin, and rifampicin. Ampicillin and chloramphenicol were found to inhibit all bacteria used in this study. The vast majority of tested strains revealed phenotypic resistance to vancomycin, ciprofloxacin, and aminoglycosides. Most of Lactobacillus strains showed high minimum inhibitory concentrations (MICs) of cefotaxime, ceftriaxone, and cefazolin and therefore were considered resistant to cephalosporins. All the strains exhibited multidrug resistance. The occurrence of resistance genes was associated with phenotypic resistance, with the exception of phenotypically susceptible strains that contained genes for tetracycline (tetK, tetL) and erythromycin (ermB, mefA) resistance. The vanX gene for vancomycin resistance was among the most frequently identified among the lactobacilli (75% of strains), but the occurrence of the parC gene for ciprofloxacin resistance was sporadic (20% of strains). Our results mainly evidence the intrinsic nature of the resistance to aminoglycosides in lactobacilli, though genes for enzymatic modification of streptomycin aadA and aadE were found in 20% of tested strains. The occurrence of extended spectrum beta-lactamases (ESBL) was unknown in Lactobacillus, but our results revealed the blaTEM gene in 80% of strains, whereas blaSHV and blaOXA-1 genes were less frequent (20% and 15% of strains, respectively).

Characterization of Erythromycin and Tetracycline Resistance in Lactobacillus fermentum Strains.

Lactobacillus fermentum colonizing gastrointestinal and urogenital tracts of humans and animals is widely used in manufacturing of fermented products and as probiotics. These bacteria may function as vehicles of antibiotic resistance genes, which can be transferred to pathogenic bacteria. Therefore, monitoring and control of transmissible antibiotic resistance determinants in these microorganisms is necessary to approve their safety status. The aim of this study was to characterize erythromycin and tetracycline resistance of L. fermentum isolates and to estimate the potential transfer of resistance genes from lactobacilli to the other Gram-positive and Gram-negative bacteria. Among six L. fermentum strains isolated from human feces and commercial dairy products, five strains demonstrated phenotypic resistance to tetracycline. PCR screening for antibiotic resistance determinants revealed plasmid-located tetracycline resistance genes tet(K) and tet(M) in all strains and erythromycin resistance genes erm(B) in the chromosome of L. fermentum 5-1 and erm(C) in the plasmid of L. fermentum 3-4. All tested lactobacilli lacked conjugative transposon Tn916 and were not able to transfer tetracycline resistance genes to Staphylococcus aureus, Staphylococcus epidermidis, Listeria monocytogenes, Acinetobacter baumannii, Citrobacter freundii, and Escherichia coli by filter mating. Staphylococcus haemolyticus did not accept erythromycin resistance genes from corresponding Lactobacillus strains. Thus, in the present study, L. fermentum was not implicated in the spread of erythromycin and tetracycline resistance, but still these strains pose the threat to the environment and human health because they harbored erythromycin and tetracycline resistance genes in their plasmids and therefore should not be used in foods and probiotics.