Safety attributes of Pseudomonas sp. P26, an environmental microorganism with potential application in contaminated environments

Currently, the selection of non-pathogenic microorganisms that lack clinically relevant antimicrobial resistance is crucial to bioaugmentation strategies. Pseudomonas sp. P26 (P26) is an environmental bacterium of interest due to its ability to remove aromatic compounds from petroleum, but its safety characteristics are still unknown. The study aimed to: a) determine P26 sensitivity to antimicrobials, b) investigate the presence of quinolone and β-lactam resistance genes, c) determine the presence of virulence factors, and d) evaluate the effect of P26 on the viability of Galleria mellonella (an invertebrate animal model). P26 antimicrobial sensitivity was determined in vitro using the Kirby-Bauer agar diffusion method and the VITEK 2 automated system (BioMerieux®). Polymerase Chain Reaction was employed for the investigation of genes associated with quinolone resistance, extended-spectrum β-lactamases, and carbapenemases. Hemolysin and protease production was determined in human blood agar and skimmed-milk agar, respectively. In the in vivo assay, different doses of P26 were injected into Galleria mellonella larvae and their survival was monitored daily. Control larvae injected with Pseudomonas putida KT2440 (a strain considered as safe) and Pseudomonas aeruginosa PA14 (a pathogenic strain) were included. Pseudomonas sp. P26 was susceptible to most evaluated antimicrobials, except for trimethoprim-sulfamethoxazole. No epidemiologically relevant genes associated with quinolone and β-lactam resistance were identified. Hemolysin and protease production was only evidenced in the virulent strain (PA14). Furthermore, the results obtained in the in vivo experiment demonstrated that inocula less than 108 CFU/mL of P26 and P. putida KT2440 did not significantly affect larval survival, whereas larvae injected with the lowest dose of the pathogenic strain P. aeruginosa PA14 experienced instant mortality. The results suggest that Pseudomonas sp. P26 is a safe strain for its application in environmental bioremediation processes. Additional studies will be conducted to ensure the safety of this bacterium against other organisms.

Dibenzothiophene removal by environmental bacteria with differential accumulation of intracellular inorganic polyphosphate

Dibenzothiophene (DBT), which belongs to the group of polycyclic aromatic heterocycles of sulfur, is a model substance to study the removal of sulfur compounds from oil due to its recalcitrance to traditional and specific removal processes. The aim of this work was to evaluate DBT bioremoval by environmental bacteria and its relationship with polyphosphate (polyP) accumulation, cell surface characteristics and bioemulsifying activity. Pseudomonas sp. P26 achieved the highest DBT removal percentage (48%) after 7 days of incubation. Moreover, positive correlations were estimated between DBT removal and bioemulsifying activity and biofilm formation. A strain-dependent relationship between the content of intracellular polyP and the presence of DBT in the culture medium was also demonstrated. The study of these bacterial characteristics, which could promote DBT transformation, is a first approach to select DBT-removing bacteria, in order to develop bioformulations that are able to contribute to desulfurization processes of petroleum-derived pollutants in the future.

Bioremediation on a chip: A portable microfluidic device for efficient screening of bacterial biofilm with polycyclic aromatic hydrocarbon removal capacity

Polycyclic aromatic hydrocarbons (PAHs) are pollutants of critical environmental and public health concern and their elimination from contaminated sites is significant for the environment. Biodegradation studies have demonstrated the ability of bacteria in biofilm conformation to enhance the biodegradation of pollutants. In this study, we used our newly developed microfluidic platform to explore biofilm development, properties, and applications of fluid flow, as a new technique for screening PAHs-degrading biofilms. The optimization and evaluation of the flow condition in the microchannels were performed through computational fluid dynamics (CFD). The formation of biofilms by PAHs-degrading bacteria Pseudomonas sp. P26 and Gordonia sp. H19, as pure cultures and co-culture, was obtained in the developed microchips. The removal efficiencies of acenaphthene, fluoranthene and pyrene were determined by HPLC. All the biofilms formed in the microchips removed all tested PAHs, with the higher removal percentages observed with the Pseudomonas sp. P26 biofilm (57.4% of acenaphthene, 40.9% of fluoranthene, and 28.9% of pyrene). Pseudomonas sp. P26 biofilm removed these compounds more efficiently than planktonic cultures. This work proved that the conformation of biofilms enhances the removal rate. It also provided a new tool to rapid and low-cost screen for effective pollutant-degrading biofilms.

Development of low-cost formulations of plant growth-promoting bacteria to be used as inoculants in beneficial agricultural technologies

Phosphorus is one of the main macronutrients for plant development. Despite its large deposits in soils, it is scarcely available for plants. Phosphate-solubilizing bacteria, belonging to the group of plant growth-promoting rhizobacteria (PGPR), are capable of mobilizing deposits of insoluble phosphates in the soil. The use of PGPR as inoculants provides an environmentally sustainable approach to increase crop production. The effectiveness of inoculants depends on their proper production, formulation and storage in order to ensure the application of the required number of viable microbial cells. In order to develop inexpensive technology, low-cost compounds for biomass production and protection should be used. After the biomass production process, the product should be formulated in a liquid or a solid form, taking into account required storage time, use of protectors/carriers, storage conditions (temperature, humidity, etc.), ease of application and maintenance of beneficial effects on crops. Careful determination of these optimal conditions would ensure a low-cost efficient inoculant that would promote the growth and yield of various crops.

Optimization of Low-Cost Culture Media for the Production of Biomass and Bacteriocin by a Urogenital Lactobacillus salivarius Strain

The aim of this work was to formulate a culture medium of lower cost than conventional laboratory media, in order to simultaneously obtain high amounts of both biomass and bacteriocin of vaginal Lactobacillus salivarius CRL 1328. The growth assays under different culture conditions were performed by using a 2(8-2) central composite experimental design, with a central point and sixteen additional points. The factors taken into consideration were glucose, lactose, yeast extract, tryptone, ammonium citrate, sodium acetate, MgSO4 and MnSO4. The simultaneous presence of a carbon source (mainly glucose), a nitrogen source (mainly yeast extract) and salts (mainly MnSO4, MgSO4 and sodium acetate) allowed the highest cell biomass and bacteriocin levels to be reached in the experimental design. Through the application of the desirability function, several optimal medium compositions to achieve efficient production of biomass and bacteriocin were predicted. The optimized growth media allow a cost reduction of around 25 to 40% compared with conventional broths. The results obtained represent an advance in the search of the most suitable strategies for the production of bioactive compounds for pharmaceutical products to prevent or treat female urogenital infections.

Immunomodulation of Lactobacillus reuteri CRL1324 on Group B Streptococcus Vaginal Colonization in a Murine Experimental Model

PROBLEM

Maternal Group B Streptococcus (GBS) colonization is a risk factor for infectious disease in newborns. One promising strategy is the modulation of vaginal defense to increase the host's ability to combat infection.

METHOD OF STUDY

The effect of intravaginal (i.va.) Lactobacillus reuteri CRL1324 inoculation on different immune cell populations, cytokines, and immunoglobulin isotypes in a murine model of GBS vaginal colonization was evaluated.

RESULTS

Seven i.va. inoculations of L. reuteri CRL1324 previous to GBS challenge showed an immunomodulatory effect on the cells and mediators of innate immunity, decreasing the number of neutrophils induced by the pathogen and increasing the activated macrophage population. Moreover, increases in B lymphocytes and IgA and IgG subclasses were observed in mice inoculated with L. reuteri CRL1324 and then challenged with GBS.

CONCLUSION

Lactobacillus reuteri CRL1324 shows a protective effect against GBS colonization that could be mediated by the modulation of the immune response.

Profiles and technological requirements of urogenital probiotics

Probiotics, defined as live microorganisms that, when administered in adequate amounts, confer a health benefit on the host, are considered a valid and novel alternative for the prevention and treatment of female urogenital tract infections. Lactobacilli, the predominant microorganisms of the healthy human vaginal microbiome, can be included as active pharmaceutical ingredients in probiotics products. Several requirements must be considered or criteria fulfilled during the development of a probiotic product or formula for the female urogenital tract. This review deals with the main selection criteria for urogenital probiotic microorganisms: host specificity, potential beneficial properties, functional specifications, technological characteristics and clinical trials used to test their effect on certain physiological and pathological conditions. Further studies are required to complement the current knowledge and support the clinical applications of probiotics in the urogenital tract. This therapy will allow the restoration of the ecological equilibrium of the urogenital tract microbiome as well as the recovery of the sexual and reproductive health of women.

In vitro and in vivo effects of beneficial vaginal lactobacilli on pathogens responsible for urogenital tract infections

The aim of this work was to evaluate the effects of beneficial human vaginal lactobacilli (Lb) on urogenital pathogens through in vitro and in vivo experiments. Co-aggregative and antimicrobial properties between five vaginal Lb strains and urogenital pathogens or potential pathogens (Streptococcus agalactiae, Staphylococcus aureus and Candida albicans strains) were assayed. Also, associative cultures of Lb strains and S. agalactiae were performed and bacterial growth, pH, lactic acid and hydrogen peroxide (H2O2) were determined at different times. Based on the results obtained, the in vivo studies were assayed in mice with Lactobacillus gasseri CRL 1509 or Lactobacillus salivarius CRL 1328 inoculated intravaginally (i.v.) and then challenged i.v. with S. agalactiae. Results were analysed by ANOVA (repeated measures and general linear models). Most of the Lb strains increased the percentage of aggregation of S. agalactiae strains. Only one strain (Lactobacillus reuteri CRL 1324) positively affected the aggregation of S. aureus and none increased the aggregation of C. albicans. The inhibition of the growth of S. agalactiae strains by production of organic acids by lactobacilli was evidenced. The Lb-S. agalactiae co-cultures showed a significant inhibition of the pathogen after 4 h and 8 h of incubation. Parallel increases in lactic acid and H2O2 levels were observed. However, in the experimental murine model, no significant differences were obtained in the number of streptococci recovered from the vaginal tract of control mice and those inoculated with Lb. In conclusion, vaginal Lb exhibited in vitro co-aggregative and antimicrobial effects on S. agalactiae strains, suggesting that they could be promising candidates for protection against S. agalactiae challenge. However, as these effects were not evidenced in the murine model used, further animal studies under different experimental conditions should be conducted to evaluate the preventive effect of Lb against challenge with S. agalactiae.

Beneficial lactobacilli: effects on the vaginal tract in a murine experimental model

Vaginal probiotics containing lactic acid bacteria with activity towards pathogenic microorganisms that cause urogenital tract infections have been proposed as a valid strategy for their prophylaxis and therapy. A murine experimental model was set up to evaluate the colonization capability of beneficial human lactobacilli and their effects on the mouse vaginal mucosa and innate immune cells. Five Lactobacillus strains were intravaginally inoculated into previously estrogenized BALB/c mice. The significance of the effects observed in the vaginal tract was determined by analysis of variance using the general linear model. The numbers of viable vaginal lactobacilli were significantly higher at proestrous-estrous than those at the metaestrous-diestrous phase and decreased markedly on the days after inoculation. Lactobacilli inoculation did not cause cytological or histological modifications of the murine vaginal tract. Moreover, the intravaginal administration of Lactobacillus salivarius CRL (Centro de Referencia para Lactobacilos culture collection) 1328 and Lactobacillus gasseri CRL 1263 did not affect the amounts of granulocytes and macrophages present in vaginal washings. In conclusion, the results demonstrate that vaginal lactobacilli did not produce adverse effects on the murine vaginal tract. Therefore, they could be proposed as safe probiotic candidates to promote a balanced microbiota in the urogenital tract.

Estimation of combined effects of carbon and nitrogen sources on the growth and bacteriocin production of Lactobacillus salivarius from human source

Vaginal Lactobacillus salivarius CRL 1328 (Centro de Referencia para Lactobacilos Culture Collection) or the bacteriocin that produces could be included in a urogenital probiotic formula to prevent urogenital infections in women. The objective of this work was to determine the effects of different carbon and nitrogen sources on the growth and bacteriocin production of this microorganism. A fractional factorial design 3(5-1) was applied to evaluate the effects of five nutrients (glucose, lactose, yeast extract, tryptone and meat peptone), at three different concentrations (0, 1 and 2%). Results were statistically analyzed for linear and quadratic effects of nutrients, along with their interactions. All the nutrients tested stimulated the cell growth and bacteriocin production, but lactose had not a significant influence on the last response. The linear effects of higher magnitude on biomass and bacteriocin production were those of yeast extract and tryptone. The results demonstrated that there were significant interactions between the different nutrients, depending on the response evaluated. Maximum bacteriocin production was reached in different growth media with a lower cost than conventional culture media used in the laboratory. These findings will contribute to the design of a pharmaceutical product for the restoration of ecological balance of urogenital tract.

Stability of freeze-dried vaginalLactobacillusstrains in the presence of different lyoprotectors

The industrial use of lactic acid bacteria as probiotic cultures depends on the preservation techniques employed, which are required to guarantee stable cultures in terms of viability and functional activity. The aim of this study was to evaluate the effects of 12% lactose and 12% sucrose suspended in water or reconstituted skim milk on the survival and expression of beneficial characteristics during freeze-drying and subsequent storage of 6 vaginal lactobacilli strains. A cubic polynomial model was also used for the first time to evaluate the effects of different protectors on survival behavior during storage. Different survival patterns were observed among the strains considered. The presence of both lactose and sucrose in water or in 6% skim milk as the suspension medium proved to be effective in maintaining a high degree of survival and expression of potentially probiotic characteristics (production of antimicrobial substances or auto-aggregation capabilities) of most strains after lyophilization and long-term storage. This study constitutes a valuable step to obtain concentrated cultures with the highest stability of microorganisms for pharmaceutical purposes.

Viability of vaginal probiotic lactobacilli during refrigerated and frozen storage

The viability of six different strains of probiotic vaginal Lactobacillus was examined in two different cryoprotective media, during refrigerated versus frozen storage, and using two traditional types of stock cultures for starting the biomass production. Freezing at -20 degrees C and -70 degrees C had much less adverse effect on viability than did storage at 7 degrees C, and the reduction in viability was greater at -20 degrees C than at -70 degrees C. The strains showed variation in the extent of the viability losses during both types of storage. Milk-yeast extract (MYE) was shown to be the more suitable protective medium to maintain viability of the strains during the storage. The vaginal Lactobacillus strains are most stable in MYE at -70 degrees C with only a small decrease of the viability observed under these conditions. The viable cell counts of Lactobacillus paracasei CRL 1251 and CRL 1289, L. crispatus CRL 1266 and L. salivarius CRL 1328 remained around 1 x 10(8) CFU/mL after 24 months of storage at -70 degrees C, or up to 18 months for L. acidophilus CRL 1259.

Effect of some pharmaceutical excipients on the survival of probiotic vaginal lactobacilli

Lactobacilli are the predominant microorganisms of the vaginal bacterial microbiota, and they play a major role in the maintenance of a healthy urogenital tract. In consequence, the interest in their potential use as probiotics has significantly increased during the last decade. In the present study we assessed the influence of different excipients on the survival of 4 probiotic vaginal lactobacilli incorporated into glycerinated gelatin ovules and stored at 5 degrees C for 60 d. Results showed that viability after storage was a strain-dependent characteristic, but inclusion of ascorbic acid significantly increased survival in 3 of the 4 strains tested. The best survival was observed for Lactobacillus salivarius CRL 1328 in ovules containing skimmed milk. No significant differences in viability were observed between control ovules (glycerogelatin base without excipients) and those containing lactose or Tween 80 for any of the strains tested. Lactobacillus acidophilus CRL 1259 and Lactobacillus crispatus CRL 1266 were, respectively, the most resistant and sensitive strains to the storage with the different substances. In conclusion, these results provide a basis for selecting excipients to improve the survival of lactobacilli in a probiotic product, in an attempt to ensure the delivery of an adequate number of viable cells to the urogenital tract.

Production of antimicrobial substances by lactic acid bacteria I: determination of hydrogen peroxide

Restoration of the balance of different ecological niches has been proposed as a way to control the income of pathogenic microorganisms. The genus Lactobacillus has been used in different human and animal tracts as probiotic microorganisms with this objective in mind. The characteristics of the strains proposed as probiotics have been published or patented under the process of elaboration of different types of products. One of the mechanisms suggested to control the vaginal ecosystem is the production of antagonistic substances (lactic acid, bacteriocins, or H2O2). The H2O2-producing microorganisms present in the vagina of healthy women have been suggested as some of the bacteria responsible for maintenance of ecological balance, mainly in pregnant women. The absence of these microorganisms is related to a higher risk of: bacterial vaginosis, recurrent urinary tract infections by Escherichia coli, and acquisition of human immunodeficiency virus type 1 (HIV-1). Bauer has proposed that H2O2-producing lactobacilli also might exert control over vaginal cancer through specific interactions of reactive oxygen species, such as superoxide anion, hydroxyl radicals, and hypochlorous acid. The conversion of H2O2 into more toxic compounds during the oxidative process is potentiated by peroxidase and halures. This enzyme and some halures, such as chloride and bromide, are present in vaginal washes in sufficient amounts to allow an optimal environment for successful inhibition of pathogens. In vitro tests provide an approach for determining the ability of lactobacilli to produce H2O2. The H2O2 amounts produced in such systems are probably not a direct reflection of what happens in the vaginal tract of women or animals, which is not yet know. However, there is a registered patent with an H2O2-generating L. crispatus strain, also supporting the use of H2O2-producing lactobacilli to restore the vaginal ecosystem.

Growth and lactic acid production by vaginal Lactobacillus acidophilus CRL 1259, and inhibition of uropathogenic Escherichia coli

Lactic acid-producing lactobacilli were selected from 134 human vaginal isolates by testing their capability to inhibit the growth of different pathogenic micro-organisms. Lactobacillus acidophilus CRL 1259 (from the CERELA Culture Collection) was selected to study the effects of temperature, pH and culture medium on growth and lactic acid production. Growth parameters were estimated by using the model of Gompertz. Kinetics of inhibition of uropathogenic Escherichia coli were evaluated in mixed cultures of the pathogen and L. acidophilus. Optimal conditions for growth and lactic acid production by L. acidophilus were pH 6.5 or 8.0 and 37 degrees C. Under these conditions, growth was higher in LAPTg (yeast extract/peptone/tryptone/Tween 80/glucose) broth than in MRS (De Man-Rogosa-Sharpe) broth. However, lactic acid production was more efficient in MRS broth. Under optimal conditions for lactic acid production, L. acidophilus inhibited the growth of E. coli. These results suggest that inclusion of L. acidophilus CRL 1259 in probiotic products for vaginal application would be beneficial.

Comparison of the growth and hydrogen peroxide production by vaginal probiotic lactobacilli under different culture conditions

OBJECTIVE

The purpose of this study was to determine the optimal conditions for the growth and hydrogen peroxide production by vaginal lactobacilli.

STUDY DESIGN

Two vaginal lactobacillus strains were cultured under different growth conditions (temperature, pH, agitation, and growth media) with a fractional factorial experimental design.

RESULTS

The optimal growth conditions of Lactobacillus paracasei CRL (Centro de Referencia para Lactobacilus Culture Collection) 1289 and Lactobacillus crispatus CRL 1266 were temperature 37 degrees C and initial pH 6.5, nonagitated cultures, in autolysat de levure; peptone, tryptone, Tween 80 et glucose (LAPTg) broth for L paracasei or in de Man-Rogosa-Sharpe (MRS) and LAPTg broths for L crispatus. The hydrogen peroxide production, detected only in agitated cultures, was higher at 37 degrees C and pH 6.5. The oxidative metabolite produced the self-inhibition of the lactobacilli growth. In mixed cultures of lactobacilli and Staphylococcus aureus under the optimal conditions of hydrogen peroxide production, the pathogen growth was inhibited.

CONCLUSION

The results provided information about the factors that affect the hydrogen peroxide production and about the most favorable conditions with which to obtain the highest biomass in the shortest possible time.