Effect of L. plantarum cell-free extract and co-trimoxazole against Salmonella Typhimurium: a possible adjunct therapy

The impacts of antimicrobial and antifungal activity of cell-free supernatants from lactic acid bacteria in vitro and foods

Lactic acid bacteria (LAB) are distinguished by their ability to produce lactic acid, among other interesting metabolites with antimicrobial activity. A cell-free supernatant (CFS) is a liquid containing the metabolites resulting from microbial growth and the residual nutrients of the medium used. CFS from LAB can have antimicrobial activity due to organic acids, fatty acids, and proteinaceous compounds, among other compounds. This review aims to summarize the information about CFS production, CFS composition, and the antimicrobial (antibacterial and antifungal) activity of CFS from LAB in vitro, on foods, and in active packaging. In addition, the mechanisms of action of CFS on cells, the stability of CFS during storage, CFS cytotoxicity, and the safety of CFS are reviewed. The main findings are that CFS's antibacterial and antifungal activity in vitro has been widely studied, particularly in members of the genus Lactobacillus. CFS has produced strong inhibition of bacteria and molds on foods when applied directly or in active packaging. In most studies, the compounds responsible for antimicrobial activity are identified. A few studies indicate that CFSs are stable for 1 to 5 months at temperatures ranging from 4 to 35°C. The cytotoxicity of CFS on human cells has not been well studied. However, the studies that have been performed reported no toxicity of CFS. Therefore, it is necessary to investigate novel growth mediums for CFS preparation that are compatible with food sensory properties. More studies into CFS stability and cytotoxic effects are also needed.

Ionic liquids containing ketoconazole improving topical treatment of T. Interdigitale infection by synergistic action

This study aimed to exert the synergistic action of ketoconazole (KCZ) and ionic liquids (ILs) for improving antifungal effect. Various ILs were engineered and demonstrated different solubilization capacity for KCZ. Among them, the IL formed by choline and geranic acid ([Ch][Ger]) was the optimal one and able to imporve the solubility of KCZ by around 100-fold. The in vitro antifungal test revealed the [Ch][Ger] significantly inhibited the activity of T. Interdigitale and exerted the synergistic action with KCZ. Compared to Daktarin®, the [Ch][Ger] not only promoted KCZ to penetrate into deep skin layer but also improved in vivo anti-T. Interdigitale activity significantly. Besides, the [Ch][Ger] was able to strip the skin of the lesion site in a flaky manner to remove fungi more thoroughly. However, the skin can recover to be normal state after treatment and there was no evident skin irritation found in [Ch][Ger] group. The ILs may offer promising opportunities to deliver anti-fungal drugs to treat inner skin fungal infections by synergistic action.

Salmonella Strain Specificity Determines Post-typhoid Central Nervous System Complications: Intervention by Lactiplantibacillus plantarum at Gut-Brain Axis

Neurological complications occurring due to Salmonella infection in some typhoid patients remain a relatively unexplored serious complication. This study firstly aimed to explore whether disseminative ability of Salmonella from gut to brain is strain specific or not and on the basis of bacterial load, histopathology, and behavioral changes, it was observed that Salmonella enterica serovar Typhimurium NCTC 74 did not cause brain infection in murine model in contrast to Salmonella Typhimurium SL1344. Simultaneously, alarming escalation in antimicrobial resistance, making the existing antibiotics treatment inefficacious, prompted us to evaluate other bio-compatible strategies as a potential treatment option. In this context, the role of gut microbiota in influencing behavior, brain neurochemistry, and physiology by modulating key molecules associated with gut-brain axis has captured the interest of the scientific community. Followed by in vitro screening of potential probiotic strains for beneficial attributes, efficacy of the selected strain was systematically evaluated at various levels of gut-brain axis against Salmonella induced brain infection. Analysis of behavioral (depression, anxiety, and locomotor), neurochemical [gamma amino butyric acid and acetylcholinesterase (AChE)], neuropathological (brain and intestinal histology; bacterial burden), and immunohistochemical studies (tight junction proteins expression) revealed its role in preventing serious manifestations and proving its potential as "psychobiotic." To the best of our knowledge, this is the first report elaborating strain specificity of Salmonella in causing post-typhoidal neurological manifestations and simultaneous use of probiotic in managing the same by influencing the pathophysiology at gut-brain axis.

Recombinant expression, purification and PEGylation of Paneth cell peptide (cryptdin-2) with value added attributes against Staphylococcus aureus

Cryptdins are disulfide-rich cationic antimicrobial peptides secreted by mouse Paneth cells and are known to exhibit potent antimicrobial activity against various deadly pathogens. Keeping in view the extremely low yield obtained from mouse Paneth cells and high cost of synthetic peptide(s), herein, we have attempted to produce cryptdin-2 in Escherichia coli using recombinant technology. To avoid lethal effects of peptide on the host cells, cryptdin-2 was expressed as a fusion protein with thioredoxin as fusion partner which yielded 40 mg/L protein in the soluble fraction. Subsequently, mature cryptdin-2 was cleaved from the fusion partner and purified by cation exchange chromatography. Since conjugation of poly(ethylene) glycol (PEG) has been known to improve the biological properties of biomolecules, therefore, we further attempted to prepare PEG-conjugated variant of cryptdin-2 using thiol specific PEGylation. Though the antimicrobial activity of PEGylated cryptdin-2 was compromised to some extent, but it was found to have enhanced serum stability for longer duration as compared to its un-modified forms. Also, it was found to exhibit reduced toxicity to the host cells. Further, its synergism with gentamicin suggests that PEGylated cryptdin-2 can be used with conventional antibiotics, thereby indicating its possibility to be used as an adjunct therapy.

Probiotics as antifungal agents: Experimental confirmation and future prospects

Fungal burden throughout the world is very high and it keeps escalating due to increasing numbers of immunocompromised individuals. In contrast, the drugs used in management of fungal infections are so few some with high toxicity. Furthermore, highly resistant fungal pathogens are emerging for example Candida auris, Candida glabrata, Candida gullemondii and Aspergillus species among others. Thus now, more than ever, there is a need for combined efforts and an all round search for possible solutions to curb these problems. Therefore, the role of probiotics in management of fungal infections is indispensable. In fact, the antimicrobial activity of probiotics has been screened with promising results against microbial pathogens. Although, recent reports indicated that probiotics may also contribute to protect against fungal infections, the research done in checking antifungal activity of probiotics has used varied technology. This calls for harmonization of the methods used to screen and confirm the antimicrobial activity of probiotics and other candidate microorganisms. We therefore sought to address issues of disparity in probiotic research and their outcomes. Thus this paper is in order as it comprehensively reviews' publications, provides a summary of the methods and future prospects of probiotics as antifungal agents.

Salmonella infection - prevention and treatment by antibiotics and probiotic yeasts: a review

Global Salmonella infection, especially in developing countries, is a health and economic burden. The use of antibiotic drugs in treating the infection is proving less effective due to the alarming rise of antibiotic-resistant strains of Salmonella, the effects of antibiotics on normal gut microflora and antibiotic-associated diarrhoea, all of which bring a growing need for alternative treatments, including the use of probiotic micro-organisms. However, there are issues with probiotics, including their potential to be opportunistic pathogens and antibiotic-resistant carriers, and their antibiotic susceptibility if used as complementary therapy. Clinical trials, animal trials and in vitro investigations into the prophylactic and therapeutic efficacies of probiotics have demonstrated antagonistic properties against Salmonella and other enteropathogenic bacteria. Nonetheless, there is a need for further studies into the potential mechanisms, efficacy and mode of delivery of yeast probiotics in Salmonella infections. This review discusses Salmonella infections and treatment using antibiotics and probiotics.

Potential of 2, 2'-dipyridyl diselane as an adjunct to antibiotics to manage cadmium-induced antibiotic resistance in Salmonella enterica serovar Typhi Ty2 strain

One of the reasons for increased antibiotic resistance in Salmonella enterica serovar Typhi Ty2 is the influx of heavy metal ions in the sewage, from where the infection is transmitted. Therefore, curbing these selective agents could be one of the strategies to manage the emergence of multidrug resistance in the pathogen. As observed in our earlier study, the present study also confirmed the links between cadmium accumulation and antibiotic resistance in Salmonella. Therefore, the potential of a chemically-synthesised compound 2, 2'-dipyridyl diselane (DPDS) was explored to combat the metal-induced antibiotic resistance. Its metal chelating and antimicrobial properties were evidenced by fourier transform infrared spectroscopy (FTIR), field emission scanning electron microscopy (FE-SEM), and microbroth dilution method. Owing to these properties of DPDS, further, this compound was evaluated for its potential to be used in combination with conventional antibiotics. The data revealed effective synergism at much lower concentrations of both the agents. Thus, it is indicated from the study that the combination of these two agents at their lower effective doses might reduce the chances of emergence of antibiotic resistance, which can be ascribed to the multi-pronged action of the agents.

Protease-Sensitive Inhibitory Activity of Cell-free Supernatant of Lactobacillus crispatus 156 Synergizes with Ciprofloxacin, Moxifloxacin and Streptomycin Against Pseudomonas aeruginosa: An In Vitro Study

Ciprofloxacin and streptomycin are frequently prescribed for the treatment of medical conditions originating due to infection by Pseudomonas aeruginosa. However, fluoroquinolone administration has been linked to the outgrowth of Clostridium difficile pathogen, especially in immunocompromised patients. Secondly, frequent administration of antibiotics may lead to development of resistance in the pathogens. Thus, there is a need to explore innovative adjunct therapies to lower the therapeutic doses of the antibiotics. Herein, we evaluated the synergism, if any, between conventional antibiotics and the cell-free supernatant (CFS) of vaginal Lactobacillus crispatus 156 against P. aeruginosa MTCC 741. L. crispatus 156 was isolated from the human vaginal tract, and its CFS had broad-spectrum antimicrobial activity against various Gram-positive and Gram-negative pathogens, including P. aeruginosa. The inhibitory substance present in the CFS completely lost its activity after treatment with proteinases and was resistant to temperatures up to 80 °C and pH ranging from 2 to 6. The cumulative production of the inhibitory substance in CFS was studied, and it showed that the secretion of the inhibitory substance was initiated in middle log phase of growth and peaked in late log phase. Further, CFS synergized the activities of ciprofloxacin, moxifloxacin, and streptomycin as evaluated in terms of checkerboard titrations. It lowered the minimum inhibitory concentration (MIC) of ciprofloxacin by almost 30 times and MIC of both moxifloxacin and streptomycin by 8 times. Interestingly, pepsin treatment of CFS caused the complete abrogation of its synergistic effect with all the three antibiotics. Thus, from the study, it can be concluded that probiotic-based alternative therapeutic regimen can be designed for the treatment of P. aeruginosa infections.

Evaluation of Synergistic Interactions Between Cell-Free Supernatant of Lactobacillus Strains and Amikacin and Genetamicin Against Pseudomonas aeruginosa

BACKGROUND

The indiscriminate use of antibiotics in the treatment of infectious diseases can increase the development of antibiotic resistance. Therefore, there is a big demand for new sources of antimicrobial agents and alternative treatments for reduction of antibiotic dosage required to decrease the associated side effects.

OBJECTIVES

In this study, the synergistic action of aminoglycoside antibiotics and cell-free supernatant (CFS) of probiotic (Lactobacillus rahmnosus and L. casei) against Pseudomonas aeruginosa PTCC 1430 was evaluated.

MATERIALS AND METHODS

A growth medium for culturing of probiotic bacteria was separated by centrifugation. The antimicrobial effects of CFS of probiotic bacteria were evaluated using the agar well diffusion assay. The minimum inhibitory concentration (MIC) and minimum bactericidal concentration (MBC) were evaluated using the micro dilution method. Finally, an interaction between CFS and amikacin or gentamicin against P. aeruginosa PTCC 1430 was examined through the checkerboard method and fractional inhibitory concentration (FIC). Furthermore, CFSs from Lactobacillus strains were analyzed by reversed phase HPLC (RP-HPLC) for antimicrobial compounds.

RESULTS

The results showed a significant effect of CFS on the growth of P. aeruginosa. The MIC and MBC of CFS from L. casei were 62.5 µL⁄mL while the MIC and MBC of CFS from L. rhamnosus were 62.5 μL⁄mL and 125 μL⁄mL, respectively. Using the FIC indices, synergistic interactions were observed in combination of CFS and antibiotics. Fractional Inhibitory Concentration indices of CFS from L. casei and aminoglycoside antibiotics were 0.124 and 0.312 while FIC indices of CFS from L. rhamnosus and aminoglycoside antibiotics were 0.124 and 0.56, respectively showing a synergism effect. The results of RP-HPLC showed that CFS of Lactobacillus strains contained acetic acid, lactic acid and hydrogen peroxide (H2O2).

CONCLUSIONS

Our findings indicate that probiotic bacterial strains of Lactobacillus have a significant inhibitory effect on the growth of P. aeruginosa PTCC 1430. The antimicrobial potency of this combination can be useful for designing and developing alternative therapeutic strategies against P. aeruginosa infections.

Nanocapsules loaded with iron-saturated bovine lactoferrin have antimicrobial therapeutic potential and maintain calcium, zinc and iron metabolism

AIM

This study aimed to evaluate the potential antimicrobial efficacy of alginate gel-encapsulated ceramic nanocarriers loaded with iron-saturated bovine lactoferrin (Fe-bLf) nanocarriers/nanocapsules (AEC-CP-Fe-bLf NCs).

MATERIALS & METHODS

The antimicrobial activities of non-nanoformulated apo (iron free), Fe-bLf and native forms of Australian bLf against pathogenic Salmonella typhimurium (wild strain) were studied in vitro. The efficacy of AEC-CP-Fe-bLf NCs were checked in vivo using Balb/c mice model.

RESULTS

The study revealed that native bLf is more effective in combating infection than the conventional drug ciprofloxacin (0.4 mg/ml). The efficacy of the drug was also revealed in vivo when BALB/c mice that, after being challenged with S. typhimurium (200 μl of 10(8) CFU/ml suspension), were fed orally with a nanoformulated bLf diet and the infection was observed to be eliminated. However, chronic infection developed in the group of infected mice that did not receive any drug treatment, as well as the mice treated with ciprofloxacin. The immune response to bacterial infection and to various drug treatments thereafter was studied in the mice.

CONCLUSION

The study concludes that bLf and nanoformulated Fe-bLf are more effective in the treatment of Salmonella-infected mice than ciprofloxacin.

Efficacy of cryptdin-2 as an adjunct to antibiotics from various generations against salmonella

Emerging drug resistance in Salmonella coupled with the recent poor success rate of antibiotic discovery programs of the pharmaceutical industry is a cause for significant concern. It has forced the scientific community to look for alternative new classes of antimicrobial compounds. In this context, combinations of antimicrobial peptides (AMPs) and conventional antibiotics have gained interest owing to their versatile applications. The present study was therefore planned to evaluate the synergistic effects, if any, of cryptdin-2, a mouse Paneth cell alpha-defensin, in combination with four different antibiotics i.e. ciprofloxacin, ceftriaxone, cefotaxime and chloramphenicol, which are conventionally used against Salmonella. Minimum bactericidal concentrations of the selected antimicrobial agents were determined by micro and macro broth dilution assays. In-vitro synergy between the agents was evaluated by fractional bactericidal concentration index (checkerboard test) and time-kill assay. Cryptdin-2-ciprofloxacin, cryptdin-2-ceftriaxone and cryptdin-2-cefotaxime combinations were found synergistic as evident by in vitro assays. This synergism provides an additional therapeutic choice by allowing the use of conventional antibiotics in conjunction with AMPs against MDR Salmonella.

Value addition in the efficacy of conventional antibiotics by Nisin against Salmonella

Frequent and indiscriminate use of existing battery of antibiotics has led to the development of multi drug resistant (MDR) strains of pathogens. As decreasing the concentration of the antibiotic required to treat Salmonellosis might help in combating the development of resistant strains, the present study was designed to assess the synergistic effects, if any, of nisin, in combination with conventional anti-Salmonella antibiotics against Salmonella enterica serovar Typhimurium. Minimum inhibitory concentrations (MICs) of the selected antimicrobial agents were determined by micro and macro broth dilution assays. In-vitro synergy between the agents was evaluated by radial diffusion assay, fractional inhibitory concentration (FIC) index (checkerboard test) and time-kill assay. Scanning electron microscopy (SEM) was also performed to substantiate the effect of the combinations. In-vivo synergistic efficacy of the combinations selected on the basis of in-vitro results was also evaluated in the murine model, in terms of reduction in the number of Salmonellae in liver, spleen and intestine. Nisin-ampicillin and nisin-EDTA combinations were observed to have additive effects, whereas the combinations of nisin-ceftriaxone and nisin-cefotaxime were found to be highly synergistic against serovar Typhimurium as evident by checkerboard test and time-kill assay. SEM results revealed marked changes on the outer membrane of the bacterial cells treated with various combinations. In-vivo synergy was evident from the larger log unit decreases in all the target organs of mice treated with the combinations than in those treated with drugs alone. This study thus highlights that nisin has the potential to act in conjunction with conventional antibiotics at much lower MICs. These observations seem to be significant, as reducing the therapeutic concentrations of antibiotics may be a valuable strategy for avoiding/reducing the development of emerging antibiotic resistance. Value added potential of nisin in the efficacy of conventional antibiotics may thus be exploited not only against Salmonella but against other Gram-negative infections as well.