Bile-mediated aminoglycoside sensitivity in Lactobacillus species likely results from increased membrane permeability attributable to cholic acid

Acute Pre- and Post-administration of Lactiplantibacillus plantarum 2034 and Its Secretory Metabolites Ameliorates Hyperglycaemia, Hyperlipidaemia, and Oxidative Stress in Diabetic Rats

The global prevalence rate of diabetes in 2021 was 6.1% making diabetes one of the top 10 causes of death. Prolonged use of antidiabetic medications is associated with various side effects; therefore, alternative treatment strategies for diabetes need exploration. The antidiabetic properties of Lactiplantibacillus plantarum 2034 was explored both in in vitro and in vivo studies. Secretory metabolites of probiotic L. plantarum 2034 exhibited alpha-glucosidase, alpha-amylase, and lipase inhibitory activities, in vitro. Further, the antidiabetic efficacy of 2034 was evaluated in streptozotocin-nicotinamide-induced diabetic rats. In the therapeutic model, oral administration of L. plantarum resulted in normalization of body weight, fasting blood glucose, total cholesterol (TC), and liver enzymes, and significant (p < 0.05) reduction in insulin and triglyceride (TG) levels. Histological evaluation of pancreas, liver, and kidney showed restoration of normal architecture in probiotic-treated group. Similarly, in a preventive + therapeutic model, 14 days of pre-administration of 2034 in pre, pre + post, and cell-free supernatant resulted in significant reduction in glucose, TG, TC, and liver biochemistry of diabetic rats as compared to untreated diabetic rats. An oral glucose tolerance test showed that the glucose levels normalized within 90 min in all the treated groups. Further, the oxidative stress parameters were also studied that showed that in all the treated groups, the concentration of antioxidant enzymes significantly (p < 0.05) increased as compared to diabetic untreated rats. Thus, administration of L. plantarum 2034 and its metabolites successfully ameliorated hyperglycaemia and hypercholesterolemia in both the models probably due to inhibition of gut enzymes and by increasing the concentration of liver antioxidant enzymes.

Putative Probiotic Ligilactobacillus salivarius Strains Isolated from the Intestines of Meat-Type Pigeon Squabs

This study aims to screen for potential probiotic lactic acid bacteria from the intestines of meat-type pigeon squabs. Ligilactobacillus salivarius YZU37 was identified as the best comprehensive performed strain. Being acid- and bile salt-tolerant, it displayed growth-inhibition activities against Staphylococcus aureus ATCC25923, Escherichia coli ATCC25922, and Salmonella typhimurium SL1344, exhibited sensitivity to 6 commonly used antibiotics, and endowed with good cell surface hydrophobicity, auto-aggregation property, and anti-oxidant activities. Results of in vitro experiments indicated that the bacteriostatic effects of this strain were related to the production of proteinaceous substances that depend on acidic conditions. Whole-genome sequencing of L. salivarius YZU37 was performed to elucidate the genetic basis underlying its probiotic potential. Pangenome analysis of L. salivarius YZU37 and other 212 L. salivarius strains available on NCBI database revealed a pigeon-unique gene coding choloylglycine hydrolase (CGH), which had higher enzyme-substrate binding affinity than that of the common CGH shared by L. salivarius strains of other sources. Annotation of the functional genes in the genome of L. salivarius YZU37 revealed genes involved in responses to acid, bile salt, heat, cold, heavy metal, and oxidative stresses. The whole genome analysis also revealed the absence of virulence and toxin genes and the presence of 65 genes distributed under 4 CAZymes classes, 2 CRISPR-cas regions, and 3 enterolysin A clusters which may confer the acid-dependent antimicrobial potential of L. salivarius YZU37. Altogether, our results highlighted the probiotic potential of L. salivarius YZU37. Further in vivo investigations are required to elucidate its beneficial effects on pigeons.

Characterization of Autochthonous Lactic Acid Bacteria Isolated from a Traditional Ethiopian Beverage, Tella

This study aimed to isolate lactic acid bacteria (LAB) from a traditional Ethiopian fermented product, Tella, and evaluate their functional properties. Of forty-three isolates, seven LAB were screened and identified as Pediococcus pentosaceus, Latilactobacillus curvatus, Leuconostoc mesenteroides, and Lactiplantibacillus plantarum species. The isolates were tested for their alcohol tolerance, acid and bile resistance, auto-aggregation, co-aggregation, hydrophobicity, antibacterial activity, and antibiotic susceptibility. LAB isolates, specifically P. pentosaceus TAA01, L. mesenteroides TDB22, and L. plantarum TDM41, showed a higher degree of alcohol tolerance in 8% and 10% (w/v) ethanol concentrations. Additionally, these three isolates displayed survival rates >85% in both acidic pH and bile environments. Among the isolates, L. plantarum TDM41 demonstrated the highest auto-aggregation, co-aggregation, and hydrophobicity with (44.9 ± 1.7)%, (41.4 ± 0.2)%, and (52.1 ± 0.1)% values, respectively. The cell-free supernatant of the isolates exhibited antibacterial activity against foodborne pathogens of Escherichia coli, Salmonella Enteritidis, and Staphylococcus aureus. Each isolate exhibited various levels of resistance and susceptibility to seven antibiotics and resistance was observed against four of the antibiotics tested. After performing a principal component analysis, Pediococcus pentosaceus TAA01, L. mesenteroides TDB22, and L. plantarum TDM41 were selected as the most promising ethanol-tolerant probiotic isolates.

Screening and characterization of lactic acid bacteria and fermentation of gamma-aminobutyric acid-enriched bamboo shoots

In order to produce fermented bamboo shoots with functional properties, two strains of lactic acid bacteria were selected for inoculation and fermentation. One strain, Lactiplantibacillus plantarum R1, exhibited prominent potential probiotic properties (including gastrointestinal condition tolerance, adhesion ability, antimicrobial ability, and antibiotic resistance), while the other, Levilactobacillus brevis R2, demonstrated the capability of high γ-aminobutyric acid (GABA) production (913.99 ± 14.2 mg/L). The synergistic inoculation of both strains during bamboo shoot fermentation led to a remarkable increase in GABA content (382.31 ± 12.17 mg/kg), surpassing that of naturally fermented bamboo shoots by more than 4.5 times and outperforming mono-inoculated fermentation. Simultaneously, the nitrite content was maintained at a safe level (5.96 ± 1.81 mg/kg). Besides, inoculated fermented bamboo shoots exhibited an increased crude fiber content (16.58 ± 0.04 g/100 g) and reduced fat content (0.39 ± 0.02 g/100 g). Sensory evaluation results indicated a high overall acceptability for the synergistically inoculated fermented bamboo shoots. This study may provide a strategy for the safe and rapid fermentation of bamboo shoots and lay the groundwork for the development of functional vegetable products enriched with GABA.

Emerging issues in probiotic safety: 2023 perspectives

Probiotics are used for both generally healthy consumers and in clinical settings. However, theoretical and proven adverse events from probiotic consumption exist. New probiotic strains and products, as well as expanding use of probiotics into vulnerable populations, warrants concise, and actionable recommendations on how to work toward their safe and effective use. The International Scientific Association for Probiotics and Prebiotics convened a meeting to discuss and produce evidence-based recommendations on potential acute and long-term risks, risks to vulnerable populations, the importance for probiotic product quality to match the needs of vulnerable populations, and the need for adverse event reporting related to probiotic use. The importance of whole genome sequencing, which enables determination of virulence, toxin, and antibiotic resistance genes, as well as clear assignment of species and strain identity, is emphasized. We present recommendations to guide the scientific and medical community on judging probiotic safety.

Safety assessment and characterisation of Ligilactobacillus salivarius PS21603 as potential feed additive for swine

The present study aimed to characterise in vitro properties of the strain Ligilactobacillus salivarius PS21603 and evaluate in vivo piglets’ tolerance for its use as feed additive in swine. The ability of L. salivarius PS21603 of inhibiting enteropathogens’ growth in vitro was evaluated using a co-culture assay. Low pH tolerance, bile tolerance, and resistance to osmotic changes were evaluated. The antibiotic susceptibility profile of L. salivarius PS21603 was assessed through broth microdilution method. Whole genome sequencing (WGS) was performed to exclude the presence of antibiotic resistance genes. L. salivarius PS21603 showed a high antimicrobial activity in vitro, reducing in a mean of 6.16 log cfu/ml eight different enterotoxigenic Escherichia coli strains. Moreover, L. salivarius PS21603 showed resistance to osmotic changes and was able to survive to a pH above 3.5 during 24 h and up to pH 2 at least during 2 h. In addition, WGS revealed that L. salivarius PS21603 did not harbour any resistance genes and thus there was no risk of transmissibility. Finally, an in vivo 28-days safety and tolerance study was performed. For that, 384 healthy piglets (28±2 days old and 7.5±1.5 kg, at weaning) were divided into three treatment groups receiving a different dose of L. salivarius PS21603: T1, 109 cfu/day; T2, 107 cfu/day; T3, control. Piglet’s health status was daily controlled. Individual bodyweight and feed intake per pen were weekly recorded to determine performance parameters. Blood samples were collected in 16 piglets from each treatment group on days 0 and 28 for determination of cytokine profiles. L. salivarius PS21603 was safe and well tolerated by piglets, there were no differences in performance nor cytokine profile between treatment groups. In conclusion, L. salivarius PS21603 is a potential candidate for a probiotic prevention strategy against pig diarrhoea.

Lactobacillus acidophilus novel strain, MJCD175, as a potential probiotic for oral health in dogs

The oral cavity is the second-largest habitat for microorganisms, and a well-balanced oral microbiome contributes to preventing dental disorders caused by pathogenic bacteria. Since humans and dogs have different lifestyles and oral microbiome structures, the present study aimed to develop novel probiotics for dogs. A total 53 Lactobacillus spp. were isolated from healthy dogs, and nine isolates were identified as Lactobacillus acidophilus according to 16S rRNA gene sequencing. According to the high antimicrobial activity against the dental caries-causing bacterium Streptococcus mutans, single or three mixed strains were orally administered to dogs for 4 weeks with concentration of 10⁸-10⁹ CFU/day. Intraoral swab samples were collected before and after the administration, and changes of oral pathogen were analyzed using quantitative PCR. Among them, Porphyromonas gingivalis, a critical factor of periodontitis, was significantly reduced in the single-strain administered group. Based on the acid and bile salts tolerance characteristics of isolates, systemic effects were also analyzed by comparing serum immunoglobulin and reproductive ability before and after the administration. However, no significant changes were observed in the serum IgG level and sperm quality. Overall, these in vitro and in vivo results suggest that L. acidophilus isolates from dogs, especially L. acidophilus MJCD175, could be promising probiotic candidates to support oral health without systemic adverse effects in dogs.

Analysis and Characterization of Lactobacillus paragasseri and Lacticaseibacillus paracasei: Two Probiotic Bacteria that Can Degrade Intestinal Oxalate in Hyperoxaluric Rats

In the present study, we characterized the probiotic properties of two commercially available bacterial strains, Lactobacillus paragasseri UBLG-36 and Lacticaseibacillus paracasei UBLPC-87, and evaluated their ability to degrade oxalate in vitro and in a hyperoxaluria-induced nephrolithiasis rat model. UBLG-36 harboring two oxalate catabolizing genes, oxalyl coenzyme A decarboxylase (oxc) and formyl coenzyme A transferase (frc), was previously shown to degrade oxalate in vitro effectively. Here, we show that UBLPC-87, lacking both oxc and frc, could still degrade oxalate in vitro. Both these strains harbored several potential putative probiotic genes that may have conferred them the ability to survive in low pH and 0.3% bile, resist antibiotic stress, show antagonistic activity against pathogenic bacteria, and adhere to epithelial cell surfaces. We further evaluated if UBLG-36 and UBLPC-87 could degrade oxalate in vivo and prevent hyperoxaluria-induced nephrolithiasis in rats. We observed that rats treated with 4.5% sodium oxalate (NaOx) developed hyperoxaluria and renal stones. However, when pre-treated with UBLG-36 or UBLPC-87 before administering 4.5% NaOx, the rats were protected against several pathophysiological manifestations of hyperoxaluria. Compared to the hyperoxaluric rats, the probiotic pre-treated rats showed reduced urinary excretion of oxalate and urea (p < 0.05), decreased serum blood urea nitrogen and creatinine (p < 0.05), alleviated stone formation and renal histological damage, and an overall decrease in renal tissue oxalate and calcium content (p < 0.05). Taken together, both UBLG-36 and UBLPC-87 are effective oxalate catabolizing probiotics capable of preventing hyperoxaluria and alleviating renal damage associated with nephrolithiasis.

Complete genome analysis of Lactobacillus fermentum YLF016 and its probiotic characteristics

Lactobacillus fermentum (L. fermentum) YLF016 is a well-characterized probiotic with several favorable characteristics. This study aimed to analyze the probiotic characteristics of L. fermentum and uncover the genes implicated in its potential probiotic ability on the base of its genomics features. The complete genome of L. fermentum YLF016 was found to have a circular chromosome of 2,094,354 bp, and 51.46% G + C content without any plasmid. Its chromosome contained 2,130 predicted protein-encoding genes, 58 tRNA, and 15 rRNA-encoding genes. Also, it was found to have many other probiotic properties, such as a high survival rate in the gastrointestinal tract with strong adherence to intestinal cells, antibacterial activity against pathogens, and antioxidant activity. Moreover, the genome sequence analysis demonstrated specific genes coding for carbon metabolism pathway, genetic adaption, stress resistance, and adhesive ability. Further analysis revealed its non-hemolytic activity and its non-functional ability of virulence factors. In conclusion, L. fermentum YLF016 possesses many valuable probiotic properties that refer to its potential probiotic ability.

Synergistic activity of bile salts and their derivatives in combination with conventional antimicrobial agents against Acinetobacter baumannii

ETHNOPHARMACOLOGICAL RELEVANCE

Bile traditionally was used in wound healing, having erodent, antioxidant and antimicrobial potential. Acinetobacter baumannii is a frequent etiological agent of wound infections, exhibiting high level of resistance to conventional antibiotics.

AIM OF THE STUDY

To determine the effect of selected bile acid sodium salts and their 3-dehydro (i.e. 3-oxo) derivatives, as well as their combinations with commercial antibiotics against A. baumanniia, to confirm bile ethnopharmacological application in wound healing from aspect of microbiology.

MATERIALS AND METHODS

The sensitivity of reference and multidrug resistant (MDR) A. baumannii strains to bile salts, their derivatives and conventional antibiotics were examined by a microtiter plate method. The interaction of bile salts/derivatives and antibiotics was examined by a checkerboard method and time kill curve method. The interaction of bile salts with ciprofloxacin in terms of micelles formation was examined by DOSY NMR technique.

RESULTS

The bile salts sodium deoxycholate (Na-DCA) and sodium chenodeoxycholate (Na-CDCA), as well as their derivatives sodium 3-dehydro-deoxycholate (Na-3DH-DCA) and sodium 3-dehydro-chenodeoxycholate (Na-3DH-CDCA), potentiate antibiotic activity and resensitize A. baumannii. The bile salts and their derivatives enhance A. baumannii sensitivity to antibiotics, particularly those that should penetrate cell to exhibit activity. The sodium salts of bile acid derivatives, namely Na-3DH-DCA and Na-3DH-CDCA, showed synergy against both reference and MDR strain in combination with ciprofloxacin or gentamicin, while synergy with gentamicin was obtained in all combinations, regardless of bile salt type and bacterial strains. The synergy with Na-3DH-CDCA was further confirmed by the time-kill curve method, as bacterial number decreased after 12 h. NMR experiment revealed that this bile salt derivative and ciprofloxacin form co-aggregates when bile salts concentration was higher than critical micelle concentrations (CMC), which indicate the possibility that bile salts enhance ciprofloxacin cell penetration by membrane destabilization, contributing to the synergy.

CONCLUSION

The synergistic interactions between bile salts or derivatives with ciprofloxacin and particularly gentamicin represent a promising strategy for the treatment of A. baumannii wound infections.

Antibiotic Susceptibility Profiles of Lactic Acid Bacteria from the Human Vagina and Genetic Basis of Acquired Resistances

Lactic acid bacteria can act as reservoirs of antibiotic resistance genes that can be ultimately transferred to pathogens. The present work reports on the minimum inhibitory concentration (MIC) of 16 antibiotics to 25 LAB isolates of five Lactobacillus and one Bifidobacterium species from the human vagina. Acquired resistances were detected to kanamycin, streptomycin, chloramphenicol, gentamicin, and ampicillin. A PCR analysis of lactobacilli failed to identify genetic determinants involved in any of these resistances. Surprisingly, a tet(W) gene was detected by PCR in two Bifidobacterium bifidum strains, although they proved to be tetracycline-susceptible. In agreement with the PCR results, no acquired genes were identified in the genome of any of the Lactobacillus spp. strains sequenced. A genome analysis of B. bifidum VA07-1AN showed an insertion of two guanines in the middle of tet(W) interrupting the open reading frame. By growing the strain in the presence of tetracycline, stable tetracycline-resistant variants were obtained. An amino acid substitution in the ribosomal protein S12 (K43R) was further identified as the most likely cause of VA07-1AN being streptomycin resistance. The results of this work expand our knowledge of the resistance profiles of vaginal LAB and provide evidence for the genetic basis of some acquired resistances.

Preventing dysbiosis of the neonatal mouse intestinal microbiome protects against late-onset sepsis

Late-onset sepsis (LOS) is thought to result from systemic spread of commensal microbes from the intestines of premature infants. Clinical use of probiotics for LOS prophylaxis has varied owing to limited efficacy, reflecting an incomplete understanding of relationships between development of the intestinal microbiome, neonatal dysbiosis and LOS. Using a model of LOS, we found that components of the developing microbiome were both necessary and sufficient to prevent LOS. Maternal antibiotic exposure that eradicated or enriched transmission of Lactobacillus murinus exacerbated and prevented disease, respectively. Prophylactic administration of some, but not all Lactobacillus spp. was protective, as was administration of Escherichia coli. Intestinal oxygen level was a major driver of colonization dynamics, albeit via mechanisms distinct from those in adults. These results establish a link between neonatal dysbiosis and LOS, and provide a basis for rational selection of probiotics that modulate primary succession of the microbiome to prevent disease.

Laboratory Evolution Assays and Whole-Genome Sequencing for the Development and Safety Evaluation of Lactobacillus plantarum With Stable Resistance to Gentamicin

The goal of this work was to use laboratory evolution assays and whole-genome sequencing to develop and test the safety of a probiotic, Lactobacillus plantarum, with high-level of resistance to gentamicin. The evolution of L. plantarum was evaluated under the selective pressure from gentamicin and subsequently when the selective pressure was removed. After 30 days of selective pressure from gentamicin, the minimum inhibitory concentration (MIC) of L. plantarum to gentamicin increased from 4 to 512 μg/mL and remained stable at this level. After removing the selective pressure, the resistance of L. plantarum to gentamicin decreased to 64 μg/mL after 20 days, and remained stable thereafter. Although the MIC declined it was still higher than the cut-off value recommended by EFSA, indicating that the acquisition of gentamicin-resistance was an irreversible process. Using whole-genome sequencing, gene mutations were identified in the strains that had undergone selection pressure from gentamicin as well as in the strains where the selection pressure was subsequently removed. Specifically, four non-synonymous mutations were detected including one single nucleotide polymorphism (SNP), one insertion, and two structural variants (SVs), of which the mutations in genes encoding the drug resistance MFS transporter and transcriptional regulator of AraC family were only detected in the strains under selective pressure from gentamicin. The results indicate that these mutations play an important role in increasing the resistant levels of L. plantarum to gentamicin. The mobility analysis of mutant genes confirmed that they were not located on mobile elements of the genome of highly resistant L. plantarum, indicating that horizontal gene transfer was not possible.

Genus-Wide Assessment of Antibiotic Resistance in Lactobacillus spp

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.IMPORTANCELactobacillus 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.

Safety of Lactobacillus plantarum ST8Sh and Its Bacteriocin

Total DNA extracted from Lb. plantarum ST8Sh was screened for the presence of more than 50 genes related to production of biogenic amines (histidine decarboxylase, tyrosine decarboxylase, and ornithine decarboxylase), virulence factors (sex pheromones, gelatinase, cytolysin, hyaluronidase, aggregation substance, enterococcal surface protein, endocarditis antigen, adhesion of collagen, integration factors), and antibiotic resistance (vancomycin, tetracycline, erythromycin, gentamicin, chloramphenicol, bacitracin). Lb. plantarum ST8Sh showed a low presence of virulence genes. Only 13 genes were detected (related to sex pheromones, aggregation substance, adhesion of collagen, tetracycline, gentamicin, chloramphenicol, erythromycin, but not to vancomycin, and bacitracin) and may be considered as indication of safety for application in fermented food products. In addition, interaction between Lb. plantarum ST8Sh and drugs from different groups were determined in order to establish possible application of the strain in combination with commercial drugs. Cytotoxicity of the semi-purified bacteriocins produced by Lb. plantarum ST8Sh was depended on applied concentration-highly cytotoxic when applied at 25 μg/mL and no cytotoxicity at 5 μg/mL.

In Vitro Antibacterial Activity of Unconjugated and Conjugated Bile Salts on Staphylococcus aureus

Bile salts are potent antimicrobial agents and are an important component of innate defenses in the intestine, giving protection against invasive organisms. They play an important role in determining microbial ecology of the intestine and alterations in their levels can lead to increased colonization by pathogens. We have previously demonstrated survival of the opportunistic pathogen Staphylococcus aureus in the human colonic model. Thus investigating the interaction between S. aureus and bile salts is an important factor in understanding its ability to colonize in the host intestine. Harnessing bile salts may also give a new avenue to explore in the development of therapeutic strategies to control drug resistant bacteria. Despite this importance, the antibacterial activity of bile salts on S. aureus is poorly understood. In this study, we investigated the antibacterial effects of the major unconjugated and conjugated bile salts on S. aureus. Several concentration-dependent antibacterial mechanisms were found. Unconjugated bile salts at their minimum inhibitory concentration (cholic and deoxycholic acid at 20 and 1 mM, respectively) killed S. aureus, and this was associated with increased membrane disruption and leakage of cellular contents. Unconjugated bile salts (cholic and deoxycholic acid at 8 and 0.4 mM, respectively) and conjugated bile salts (glycocholic and taurocholic acid at 20 mM) at their sub inhibitory concentrations were still able to inhibit growth through disruption of the proton motive force and increased membrane permeability. We also demonstrated that unconjugated bile salts possess more potent antibacterial action on S. aureus than conjugated bile salts.

In vitro and in vivo cholesterol lowering ability of Lactobacillus pentosus KF923750

Lactobacillus pentosus KF923750 was characterised for probiotic related properties and then characterised for cholesterol uptake in vitro as well as in vivo using rabbits fed a high-cholesterol diet. The survival percentage of L. pentosus KF923750 was 100% at pH 3, 52.18% at pH 2 and 36.21% at pH 2 plus pepsin. Similarly, this strain appeared resistant to bile (0.1% [98.42%], 0.3% [88.52%], 0.5% [75.60%] and 1% [71.15%]), after 4 h exposure. Moreover, L. pentosus KF923750 controlled growth of Escherichia coli ATCC 25922 and Staphylococcus aureus ATCC 25923 through the production of a bacteriocin-like inhibitory substance and anti-adhesive capabilities. L. pentosus KF923750 was non-cytotoxic to eukaryotic cells but sensitive to some antibiotics. Compared with rabbits fed a high-cholesterol diet but without L. pentosus KF923750 supplementation, the plasma total cholesterol, low-density lipoprotein cholesterol and triglycerides levels were significantly decreased in L. pentosus KF923750-fed rabbits by 11.54, 16.00 and 18.00%, respectively, with no significant change in high-density lipoprotein cholesterol levels. The histological sections of livers revealed lesions in all the rabbits that were fed a high-cholesterol diet, but these were less pronounced in rabbits ingesting L. pentosus KF923750. This study highlights the potential of lactobacilli, such as L. pentosus KF923750, in the treatment or prevention of hypercholesterolemia.

Exploring the relationship between exposure to technological and gastrointestinal stress and probiotic functional properties of lactobacilli and bifidobacteria

Strains of Lactobacillus and Bifidobacterium are considered probiotic because of their associated potential health benefits. Probiotics are commonly administered orally via incorporation into food products. Microorganisms for use as probiotics encounter stress conditions, which include acid, bile, osmotic, oxidative, heat and cold stresses. These can occur during processing and storage and during passage through the gastrointestinal tract, and can affect viability. Probiotic bacteria have to remain viable to confer any health benefits. Therefore, the ability to withstand technological and gastrointestinal stresses is crucial probiotic selection criteria. While the stress tolerance mechanisms of lactobacilli and bifidobacteria are largely understood, the impact of exposure to stressful conditions on the functional properties of surviving probiotic microorganisms is not clear. This review explores the potentially positive and negative relationships between exposure to stress conditions and probiotic functional properties, such as resistance to gastric acid and bile, adhesion and colonization potential, and tolerance to antibiotics. Protective strategies can be employed to combat negative effects of stress on functional properties. However, further research is needed to ascertain synergistic relationships between exposure to stress and probiotic properties.

Antimicrobial resistance genes and modelling of treatment failure in bacterial vaginosis: clinical study of 289 symptomatic women

Clinical management of bacterial vaginosis (BV) is difficult owing to inaccurate diagnostic tests, limited drug choices, and a high rate of recurrence. To our knowledge, there has not been a previous study of antimicrobial resistance (AMR) genes in community practice using next-generation sequencing (NGS). A case-control study (1 : 1 age-matched with and without BV) was undertaken in a series of 326 nongravid women of reproductive age with symptoms of BV to determine the prevalence of AMR genes. NGS was used to describe the complete vaginal microbiota and identify bacterial genes associated with resistance to: macrolides and/or lincosamides - ermA, ermB, ermC, erM, ermTR and mefA; tetracyclines, β-lactams, streptomycin, gentamicin and/or tobramycin - acrA, acrB, mecA, tet, tetA, tolC and aac2; 5-nitroimadazoles - nim and nimB; and triazoles - cdr1 and mdr1. An evidence base was created to inform treatment decisions applicable to individual patients. AMR genes were identified in all drug classes: macrolides, 35.2 %; lincosamides, 35.6 %; tetracyclines, 21.8 %; aminoglycosides (streptomycin, gentamicin and tobramycin), 5.2 % each; 5-nitroimidazoles, 0.3 %; and triazoles, 18.7 %. There was more than a fourfold-higher frequency of AMR genes in pathogens from BV than from non-BV patients for macrolides (58.2 versus 12.3 %, respectively), lincosamides (58.9 versus 12.3 %) and tetracyclines (35.6 versus 8.0 %) (Fisher's exact test; all p < 0.001). For each patient with BV, the spectrum of resistance genes was matched to the pathogens present. AMR genes were present in the majority of vaginal microbiomes of patients with symptoms of BV.

Synergistic Effect of Oleanolic Acid on Aminoglycoside Antibiotics against Acinetobacter baumannii

Difficulties involved in treating drug-resistant pathogens have created a need for new therapies. In this study, we investigated the possibility of using oleanolic acid (OA), a natural pentacyclic triterpenoid, as a natural adjuvant for antibiotics against Acinetobacter baumannii. High concentrations of OA can kill cells, partly because it generates reactive oxygen species. Measurement of the fractional inhibitory concentration (FIC) for OA and time-kill experiments demonstrated that it only synergizes with aminoglycoside antibiotics (e.g., gentamicin, kanamycin). Other classes of antibiotics (e.g., ampicillin, rifampicin, norfloxacin, chloramphenicol, and tetracycline) have no interactions with OA. Microarray and quantitative reverse transcription-PCR analysis indicated that genes involved in ATP synthesis and cell membrane permeability, the gene encoding glycosyltransferase, peptidoglycan-related genes, phage-related genes, and DNA repair genes were upregulated under OA. OA highly induces the expression of adk, which encodes an adenylate kinase, and des6, which encodes a linoleoyl-CoA desaturase, and deletion of these genes increased FICs; these observations indicate that adk and des6 are involved in the synergism of OA with aminoglycosides. Data obtained using 8-anilino-1-naphthalenesulfonic acid, fluorescence-conjugated gentamicin, and membrane fatty acid analysis indicates that adk and des6 are involved in changes in membrane permeability. Proton-motive force and ATP synthesis tests show that those genes are also involved in energy metabolism. Taken together, our data show that OA boosts aminoglycoside uptake by changing membrane permeability and energy metabolism in A. baumannii.

Probiotic features of Lactobacillus strains isolated from Ragusano and Pecorino Siciliano cheeses

In the present study 177 Lactobacillus spp. strains, isolated from Ragusano and Pecorino Siciliano cheeses, were in vitro screened for probiotic traits, and their characteristics were compared to those of Lactobacillus rhamnosus GG, commercial strain. Based on acidic and bile salt resistance, thirteen Lactobacillus strains were selected. The multiplex-PCR application revealed that nine strains belonged to L. rhamnosus species and four to Lactobacillus paracasei species. All selected strains were further investigated for transit tolerance in simulated upper gastrointestinal tract (GI), for adhesion capacity to human intestinal cell lines, for hydrophobicity, for co-aggregation and auto-aggregation and for antimicrobial activities. Moreover, antibiotic resistance, hemolytic and bile salt hydrolase activities were investigated for safety assessment. Viable counts after simulated gastric and duodenal transit revealed that overall the selected lactobacilli tolerated better pancreatic juice and bile salts than acidic juice. In particular, three L. rhamnosus strains (FS10, FS2, and PS11) and one L. paracasei strain (PM8) increased their cell density after the simulated GI transit. The same strains showed also high percentage of auto-aggregation and co-aggregation with Escherichia coli. All strains were effective against both Staphylococcus aureus and E. coli and variability was achieved versus Listeria monocytogenes and Enterococcus faecalis used as pathogenic indicator strains. Different behavior was revealed by strains for adhesion ability and hydrophobicity, which are not always linked each other and are strongly strain-dependent. From the safety point of view, no isolate showed hemolytic and bile salt hydrolase activities, except one, and most of the strains were sensitive to a broad range of clinical antibiotics. This work showed that the L. rhamnosus FS10 and the L. paracasei PM8 are good promising probiotic candidates for further in vivo investigations.

Characterization of Lactobacillus isolated from dairy samples for probiotic properties

In the present study twelve Lactobacillus isolates (LBS 1-LBS 12) were characterized for probiotic properties. Out of the twelve, eight isolates (LBS 1-6, 8 and 11) were bile resistant (survival > 50% at 0.3% bile salt w/v) and five isolates (LBS 1, 2, 5, 6 and 11) were found acid pH value resistant (survival > 50% at pH 3). All twelve isolates inhibited the growth of Staphylococcus aureus whereas isolate LBS 2 also inhibited the growth of Escherichia coli and Salmonella typhimurium. Antibiotic susceptibility testing of isolates was also performed and isolate LBS 2 was selected for further study based on its broad spectrum effect in clinical pathogen inhibition. LBS 2 was characterized phenotypically at Institute of Microbial Technology (IMTECH), Chandigarh, India and was confirmed as Lactobacillus rhamnosus by 16S rDNA sequencing and subsequent analysis using BLAST. The gene sequence was deposited in GenBank with accession number KJ562858. Scanning electron microscopy (SEM) study was used to study in vitro epithelial cell adherence and bile salt effect on isolate LBS 2. Epithelial cells adherence assay showed positive results and surface roughness of LBS 2 increased with increase in bile salt (0.15-0.45% w/v).

In vitro selection and characterization of new probiotic candidates from table olive microbiota

To date, only a few studies have investigated the complex microbiota of table olives in order to identify new probiotic microorganisms, even though this food matrix has been shown to be a suitable source of beneficial lactic acid bacteria (LAB). Two hundred and thirty eight LAB, belonging to Lactobacillus plantarum, Lactobacillus pentosus and Leuconostoc mesenteroides species, and isolated from Nocellara Etnea table olives, have been screened in this survey through an in vitro approach. A simulation of transit tolerance in the upper human gastrointestinal tract, together with autoaggregation and hydrophobicity, have been decisive in reducing the number of LAB to 17 promising probiotics. None of the selected strains showed intrinsic resistances towards a broad spectrum of antibiotics and were therefore accurately characterized on an undifferentiated and 3D functional model of the human intestinal tract made up of H4-1 epithelial cells. As far as the potential colonization of the intestinal tract is concerned, a high adhesion ratio was observed for Lb. plantarum O2T60C (over 9%) when tested in the 3D functional model, which closely mimics real intestinal conditions. The stimulation properties towards the epithelial barrier integrity and the in vitro inhibition of L. monocytogenes adhesion and invasion have also been assessed. Lb. plantarum S1T10A and S11T3E enhanced trans-epithelial electrical resistance (TEER) and therefore the integrity of the polarized epithelium in the 3D model. Moreover, S11T3E showed the ability to inhibit L. monocytogenes invasion in the undifferentiated epithelial model. The reduction in L. monocytogenes infection, together with the potential enhancement of barrier integrity and an adhesion ratio that was above the average in the 3D functional model (6.9%) would seem to suggest the Lb. plantarum S11T3E strain as the most interesting candidate for possible in vivo animal and human trials.

A novel approach for antibody nanocarriers development through hydrophobic ion-pairing complexation

IgG-Fab fragment, a model antibody protein was hydrophobically modified by a novel approach of ion-pairing complexation. Three different sulphated ion-pairing agents were utilised including sodium dodecyl sulphate, taurocholic acid and dextran sulphate (DS). The formations of hydrophobic ion-pairing (HIP) complexes were dependant on pH and molar ratio of ion-pairing agent to Fab. Aqueous solubilities of HIP complexes were very low compared to Fab alone. In particular, when dextran sulphate was added as ion-pairing agent, formed Fab:DS HIP complexes were least soluble in water. Further, nanoparticles (NPs) loaded with drug and Fab:DS HIP complex were prepared and characterised with respect to encapsulation efficiency and size. We observed significant improvement in encapsulation efficiency for Fab:DS HIP complex-loaded nanoparticles. This study demonstrates a novel approach of formulating antibody-loaded nanoparticles which can also be employed for delivery of large antibodies.

Antibiotic resistance of Lactobacillus pentosus and Leuconostoc pseudomesenteroides isolated from naturally-fermented Aloreña table olives throughout fermentation process

Antimicrobial resistance of Lactobacillus pentosus (n=59) and Leuconostoc pseudomesenteroides (n=13) isolated from Aloreña green table olives (which are naturally-fermented olives from Málaga, Spain) to 15 antibiotics was evaluated. Most Lb. pentosus (95%) and all Lc. pseudomesenteroides were resistant to at least three antibiotics. Principal component analysis determined that the prevalence of antibiotic resistance in LAB throughout the fermentation process was highly dependent on the fermenter where the fermentation took place. All Lb. pentosus and Lc. pseudomesenteroides strains were highly sensitive to amoxicillin and ampicillin (MIC≤2 μg/ml), and also to chloramphenicol (MIC≤4 μg/ml), gentamicin and erythromycin (MIC≤16 μg/ml). However, they were phenotypically resistant to streptomycin (83-100%, MIC>256 μg/ml), vancomycin and teicoplanin (70-100%, MIC>128 μg/ml), trimethoprim (76% of Lb. pentosus and 15% of Lc. pseudomesenteroides, MIC>128 μg/ml), trimethoprim/sulfomethoxazol (71-100%, MIC>4-64 μg/ml) and cefuroxime (44% of Lb. pentosus and 85% of Lc. pseudomesenteroides, MIC>32-128 μg/ml). Lb. pentosus was susceptible to tetracycline and clindamycin, while 46% of Lc. pseudomesenteroides strains were resistant to these antibiotics. Only Lb. pentosus strains were resistant to ciprofloxacin (70%, MIC>4-64 μg/ml), although no mutations in the quinolone resistance determining regions of the genes encoding GyrA and ParC were found, thus indicating an intrinsic resistance. Similarly, no genes encoding possible transferable resistance determinants for the observed phenotypic resistance were detected by PCR. In some cases, a bimodal distribution of MICs was observed for some antibiotics to which both LAB species exhibited resistance. Nevertheless, such resistances resulted from an intrinsic mechanism, non-transferable or non-acquired resistance determinants which may in part be due to chromosomally encoded efflux pumps (NorA, MepA and MdeA). Results of the present study demonstrate that all Lb. pentosus and Lc. pseudomesenteroides strains lack transferable resistance-related genes (cat, bla, blaZ, ermA, ermB, ermC, msrA/B, ereA, ereB, mphA, mefA, tet(M), tet(O), tet(S), tet(W), tet(L), tet(K), aad(E), aac(6')-Ie-aph(2')-Ia, aph(2')-Ib, aph(2')-Ic, aph(2')-Id, aph(3')-IIIa, ant(4')-Ia, dfrA, dfrD, vanA, vanB, vanC and vanE) and should therefore, according to Qualified Presumption of Safety criteria, be considered safe for future application as starter cultures or as probiotics.

Antibiotic resistance of lactic acid bacteria isolated from Chinese yogurts

The aim of this study was to evaluate the susceptibility of 43 strains of lactic acid bacteria, isolated from Chinese yogurts made in different geographical areas, to 11 antibiotics (ampicillin, penicillin G, roxithromycin, chloramphenicol, tetracycline, chlortetracycline, lincomycin, kanamycin, streptomycin, neomycin, and gentamycin). The 43 isolates (18 Lactobacillus bulgaricus and 25 Streptococcus thermophilus) were identified at species level and were typed by random amplified polymorphic DNA analysis. Thirty-five genotypically different strains were detected and their antimicrobial resistance to 11 antibiotics was determined using the agar dilution method. Widespread resistance to ampicillin, chloramphenicol, chlortetracycline, tetracyclines, lincomycin, streptomycin, neomycin, and gentamycin was found among the 35 strains tested. All of the Strep. thermophilus strains tested were susceptible to penicillin G and roxithromycin, whereas 23.5 and 64.7% of Lb. bulgaricus strains, respectively, were resistant. All of the Strep. thermophilus and Lb. bulgaricus strains were found to be resistant to kanamycin. The presence of the corresponding resistance genes in the resistant isolates was investigated through PCR, with the following genes detected: tet(M) in 1 Lb. bulgaricus and 2 Strep. thermophilus isolates, ant(6) in 2 Lb. bulgaricus and 2 Strep. thermophilus isolates, and aph(3')-IIIa in 5 Lb. bulgaricus and 2 Strep. thermophilus isolates. The main threat associated with these bacteria is that they may transfer resistance genes to pathogenic bacteria, which has been a major cause of concern to human and animal health. To our knowledge, the aph(3')-IIIa and ant(6) genes were found in Lb. bulgaricus and Strep. thermophilus for the first time. Further investigations are required to analyze whether the genes identified in Lb. bulgaricus and Strep. thermophilus isolates might be horizontally transferred to other species.

Characterization of Lactobacillus gasseri isolates from a breast-fed infant

The potential health benefits of probiotic bacteria have led to the isolation of new microbial strains for incorporation into food products. However, newly isolated candidate probiotic organisms do not automatically share the "generally recognized as safe" (GRAS) status of traditional lactic acid bacteria (LAB). Before their introduction into food products, the safety of new isolates has to be evaluated. The objective of this study was to characterize LAB isolates from the stool of a newborn infant, and evaluate their safety and probiotic potential, in vitro. Thirty colonies were identified as Lactobacillus gasseri through sequencing of 16S rDNA. Pulsed Field Gel Electrophoresis using restriction enzymes SmaI and Apa I revealed that 29 of the L. gasseri were nearly identical, however one isolate exhibited a distinctive DNA fingerprint. All 30 L. gasseri were evaluated for resistance to antibiotics, bile tolerance, hemolytic activity and antagonism toward selected pathogens. All 30 strains harbored three plasmids, with one strain that showed strong tolerance to 0.5% of bile and harbored a unique fourth plasmid encoding a putative multidrug resistance transporter protein (LmrB). No hemolytic activity or antagonism, beyond acid inhibition was observed. Three selected strains UFVCC1083, 1091 and 1112 showed strong resistance to simulated small intestinal and gastric juices and adhered in vitro to mucin and two intestinal epithelial cell lines, Caco-2 and HT-29. This study identified and characterized recently isolated L. gasseri strains from faeces of a breast fed infant as potential probiotic candidates for use in the human milk banks in Brazil.

Effects of ultrasound on growth, bioconversion of isoflavones and probiotic properties of parent and subsequent passages of Lactobacillus fermentum BT 8633 in biotin-supplemented soymilk

This study aimed to evaluate the effects of ultrasound on Lactobacillus fermentum BT 8633 in parent and subsequent passages based on their growth and isoflavone bioconversion activities in biotin-supplemented soymilk. The treated cells were also assessed for impact of ultrasound on probiotic properties. The growth of ultrasonicated parent cells increased (P<0.05) by 3.23-9.14% compared to that of the control during fermentation in biotin-soymilk. This was also associated with enhanced intracellular and extracellular (8.4-17.0% and 16.7-49.2%, respectively; P<0.05) β-glucosidase specific activity, leading to increased bioconversion of isoflavones glucosides to aglycones during fermentation in biotin-soymilk compared to that of the control (P<0.05). Such traits may be credited to the reversible permeabilized membrane of ultrasonicated parent cells that have facilitated the transport of molecules across the membrane. The growing characteristics of first, second and third passage of treated cells in biotin-soymilk were similar (P>0.05) to that of the control, where their growth, enzyme and isoflavone bioconversion activities (P>0.05) were comparable. This may be attributed to the temporary permeabilization in the membrane of treated cells. Ultrasound affected probiotic properties of parent L. fermentum, by reducing tolerance ability towards acid (pH 2) and bile; lowering inhibitory activities against selected pathogens and reducing adhesion ability compared to that of the control (P<0.05). The first, second and third passage of treated cells did not exhibit such traits, with the exception of their bile tolerance ability which was inherited to the first passage (P<0.05). Our results suggested that ultrasound could be used to increase bioactivity of biotin-soymilk via fermentation by probiotic L. fermentum FTDC 8633 for the development of functional food.

Antimicrobial and Safety Properties of Lactobacilli Isolated from two Cameroonian Traditional Fermented Foods

Twenty-one Lactobacillus isolates from "Sha'a" (a maize - based fermented beverage) and "Kossam" (traditionally fermented cow milk) were selected in accordance with their antagonistic activities and tested for their bacteriocinogenic potential as well as safety properties. These isolates were preliminarily identified as Lactobacillus plantarum (62%), Lactobacillus rhamnosus (24%), Lactobacillus fermentum (10%) and Lactobacillus coprophilus (4%) based on phenotypic characteristics and rep-PCR genomic fingerprinting. Twelve (57.1%) out of the 21 strains tested were found to be bacteriocin producers, as revealed by the sensitivity of their antimicrobial substances to proteolytic enzymes (Trypsin, Proteinase K) and inhibition of other Lactobacillus spp. These bacteriocinogenic strains showed no positive haemolytic and gelatinase activities and proved to be sensitive to penicillin G, ampicillin, tetracycline, erythromycin, amoxicillin, chloramphenicol, co-trimoxazole and doxycyclin, but resistant to ciprofloxacin and gentamicin. The bacteriocins showed a broad inhibitory activity against Gram-positive and Gram-negative pathogenic bacteria, several of which are classified as especially dangerous by the World Health Organization, as well as Multidrug-resistant strains. These include Staphylococcus aureus, Salmonella enterica subsp. enterica serovare Typhi, Bacillus cereus, Streptococcus mutans, Escherichia coli, Pseudomonas aeruginosa, Klebsiella pneumoniae and Shigella flexneri. These Lactobacillus strains are promising candidates for use as protective cultures in food fermentation.

Antibiotic resistance in lactic acid bacteria and Micrococcaceae/Staphylococcaceae isolates from artisanal raw milk cheeses, and potential implications on cheese making

Antibiotic susceptibility against 19 antimicrobial agents was evaluated in isolates of the genera Lactococcus (46 isolates), Leuconostoc (22), Lactobacillus (19), Staphylococcus (8), Enterococcus (7), and Microccoccus/Kocuria (5) obtained from the predominant microflora of nonrecent and recent types of artisanal raw cow's milk cheeses. Beta-lactams showed broad activity against all genera, although leuconostocs and lactobacilli were highly resistant to oxacillin (80% to 95.5%). Resistance to aminoglycosides was frequent for lactococci and enterococci (particularly for streptomycin), whereas lower rates of resistance were detected for lactobacilli and leuconostocs. Technologically interesting traits for the food industry were distributed among isolates that showed different degrees of resistance to common antibiotics. However, isolates showing resistance to less than 2 antibiotics were mainly those with properties of greatest technological interest (acidifying activity, proteolytic/lipolytic activities, or diacetyl production).

Orally delivered microencapsulated live probiotic formulation lowers serum lipids in hypercholesterolemic hamsters

Elevated serum cholesterol is a major risk factor for coronary artery disease. Nutritional therapies such as probiotics have been suggested to manage elevated cholesterol. This study investigates the cholesterol and triglyceride lowering potential of a microencapsulated feruloyl esterase-producing Lactobacillus fermentum 11976 (LF11976) probiotic formulation. Male Bio F(1)B hamsters were assigned to two groups to receive either the microcapsule probiotic formulation (containing LF11976 cells at 12.51 log colony-forming units/mL) or placebo formulation (empty) microcapsules, twice daily, by oral gavage for 18 weeks. For the duration of the study, animals were fed a hypercholesterolemic diet. Serum total cholesterol, low-density lipoprotein (LDL) cholesterol, and the atherogenic index were 21.36%, 31.43%, and 32.59% lower in the group gavaged with the microencapsulated probiotic formulation than in the placebo control group after 18 weeks (P < .05). Histology studies showed reduced progression of atherosclerotic lesions in animals treated with microencapsulated LF11976 as compared to control animals. Treatment with microencapsulated LF11976 formulation produces significant reductions in serum total cholesterol, LDL cholesterol, and serum triglyceride levels in diet-induced hypercholesterolemic hamsters. Findings suggest the potential of the oral microencapsulated probiotic cell formulation as a functional nutritional alternative for managing excessive serum cholesterol and triglyceride levels.

Decolorization of water and oil-soluble azo dyes by Lactobacillus acidophilus and Lactobacillus fermentum

The capability of Lactobacillus acidophilus and Lactobacillus fermentum to degrade azo dyes was investigated. The bacteria were incubated under anaerobic conditions in the presence of 6 microg/ml Methyl Red, Ponceau BS, Orange G, Amaranth, Orange II, and Direct Blue 15; 5 microg/ml Sudan I and II; or 1.5 microg/ml Sudan III and IV in deMann-Rogosa-Sharpe broth at 37 degrees C for 36 h, and reduction of the dyes was monitored. Both bacteria were capable of degrading all of the water-soluble azo dyes to some extent. They were also able to completely reduce the oil-soluble diazo dyes Sudan III and IV but were unable to reduce the oil-soluble monoazo dyes Sudan I and II to any significant degree in the concentrations studied. Growth of the bacteria was not significantly affected by the presence of the Sudan azo dyes. Metabolites of the bacterial degradation of Sudan III and IV were isolated and identified by liquid chromatography electrospray ionization tandem mass spectrometry analyses and compared with authentic standards. Aniline and o-toluidine (2-methylaniline), both potentially carcinogenic aromatic amines, were metabolites of Sudan III and IV, respectively.

Efflux-mediated drug resistance in bacteria: an update

Drug efflux pumps play a key role in drug resistance and also serve other functions in bacteria. There has been a growing list of multidrug and drug-specific efflux pumps characterized from bacteria of human, animal, plant and environmental origins. These pumps are mostly encoded on the chromosome, although they can also be plasmid-encoded. A previous article in this journal provided a comprehensive review regarding efflux-mediated drug resistance in bacteria. In the past 5 years, significant progress has been achieved in further understanding of drug resistance-related efflux transporters and this review focuses on the latest studies in this field since 2003. This has been demonstrated in multiple aspects that include but are not limited to: further molecular and biochemical characterization of the known drug efflux pumps and identification of novel drug efflux pumps; structural elucidation of the transport mechanisms of drug transporters; regulatory mechanisms of drug efflux pumps; determining the role of the drug efflux pumps in other functions such as stress responses, virulence and cell communication; and development of efflux pump inhibitors. Overall, the multifaceted implications of drug efflux transporters warrant novel strategies to combat multidrug resistance in bacteria.

Role of transporter proteins in bile tolerance of Lactobacillus acidophilus

Lactobacillus acidophilus NCFM derivatives containing deletion mutations in the transporter genes LBA0552, LBA1429, LBA1446, and LBA1679 exhibited increased sensitivity to bile. These strains showed unique patterns of sensitivity to a variety of inhibitory compounds, as well as differential accumulations of ciprofloxacin and taurocholate.