Bovine Lactoferrin can Decrease the In Vitro Biofilm Production and Show Synergy with Antibiotics Against Listeria and Escherichia coli Isolates.

BACKGROUND: Bovine Lactoferrin (bLf) has been reported as antimicrobial, antiviral, immunomodulatory and anticancer protein. Escherichia coli and Listeria spp. are food-borne bacteria that can produce illness in human being and mammals, the emergent antimicrobial drug resistance has been reported in these pathogens. OBJECTIVE: The aim for this study was to evaluate the bLf effect on in vitro biofilm production and the synergic effect of antibiotics on E. coli and Listeria isolates. METHODS: E. coli and Listeria specimens were isolated from bovine carcasses and slaughterhouses surfaces, respectively. Biofilm formation was analyzed with or without bLf, incubated for 48 h and spectrophotometry, cell viability was analyzed by colony-forming unit (CFU) and the synergistic effect of bLf with ampicillin, oxytetracycline, and streptomycin was evaluated through the fractional concentration index (FCI). RESULTS: Our results show that a low bLf concentration (0.8 µM) can diminish the in vitro biofilm production in Listeria isolates; also improves the in vitro oxytetracycline and streptomycin activity against E. coli, and ampicillin activity against Listeria isolates. CONCLUSION: bLf can affect the biofilm production in Listeria isolates from slaughterhouses surfaces and shown synergic effect with ampicillin. Also has a synergic effect with oxytetracycline and streptomycin against E. coli isolates from bovine carcasses.

Screening of the Enterocin-Encoding Genes and Antimicrobial Activity in Enterococcus Species.

In the current study, a total of 135 enterococci strains from different sources were screened for the presence of the enterocin-encoding genes entA, entP, entB, entL50A, and entL50B. The enterocin genes were present at different frequencies, with entA occurring the most frequently, followed by entP and entB; entL50A and L50B were not detected. The occurrence of single enterocin genes was higher than the occurrence of multiple enterocin gene combinations. The 80 isolates that harbor at least one enterocin-encoding gene (denoted "Gene(+) strains") were screened for antimicrobial activity. A total of 82.5% of the Gene(+) strains inhibited at least one of the indicator strains, and the isolates harboring multiple enterocin-encoding genes inhibited a larger number of indicator strains than isolates harboring a single gene. The indicator strains that exhibited growth inhibition included Listeria innocua strain CLIP 12612 (ATCC BAA-680), Listeria monocytogenes strain CDC 4555, Enterococcus faecalis ATCC 29212, Staphylococcus aureus ATCC 25923, S. aureus ATCC 29213, S. aureus ATCC 6538, Salmonella enteritidis ATCC 13076, Salmonella typhimurium strain UK-1 (ATCC 68169), and Escherichia coli BAC 49LT ETEC. Inhibition due to either bacteriophage lysis or cytolysin activity was excluded. The growth inhibition of antilisterial Gene+ strains was further tested under different culture conditions. Among the culture media formulations, the MRS agar medium supplemented with 2% (w/v) yeast extract was the best solidified medium for enterocin production. Our findings extend the current knowledge of enterocin-producing enterococci, which may have potential applications as biopreservatives in the food industry due to their capability of controlling food spoilage pathogens.

Effect of citral and carvacrol on the susceptibility of Listeria monocytogenes and Listeria innocua to antibiotics.

UNLABELLED: The aim of this study was to evaluate the antibiotic susceptibility of Listeria innocua (L. innocua) and Listeria monocytogenes (L. monocytogenes) cells in the presence of citral and carvacrol at sublethal concentrations in an agar medium. The presence of terpenes in the L. monocytogenes and L. innocua culture medium provided a reduction in the minimal inhibitory concentration (MIC) of all the antibiotics tested. These effects were dependent on the concentration of terpenes present in the culture medium. The combination of citral and carvacrol potentiated antibiotic activity by reducing the MIC values of bacitracin and colistin from 32.0 and 128.0 µg ml⁻¹ to 1.0 and 2.0 µg ml⁻¹, respectively. Thus, both Listeria species became more susceptible to these drugs. In this way, the colistin and bacitracin resistance of L. monocytogenes and L. innocua was reversed in the presence of terpenes. Results obtained in this study show that the phytochemicals citral and carvacrol potentiate antibiotic activity, reducing the MIC values of cultured L. monocytogenes and L. innocua. SIGNIFICANCE AND IMPACT OF THE STUDY: Phytochemicals citral and carvacrol potentiate antibiotic activity of erythromycin, bacitracin and colistin by reducing the MIC values of cultured Listeria monocytogenes and Listeria innocua. This effect in reducing the MIC values of the antibiotics tested in both micro-organisms was increased when natural antimicrobials were combined. This finding indicated that the combination among terpenes and antibiotic may contribute in reducing the required dosage of antibiotics due to the possible effect of terpenes on permeation barrier of the micro-organism cell membrane.

Efecto de polimixina B sobre el mecanismo hemolítico del género Listeria / Effect of polymyxin B on the hemolytic mechanism of the genus Listeria

El contacto de polimixina B, sobre hematíes humanos produjo un efecto sobre la actividad hemolítica de las hemolisinas del género Listeria. A bajas concentraciones de antibiótico, se observó un efecto promotor de la hemólisis; verificándose una inhibición de la lisis eritrocitaria a altas concentraciones de polimixina B. Este comportamiento permitió definir perfiles hemolíticos para cada una de las especies hemolíticas del género en estudio. Listeria monocytogenes y Listeria seeligeri presentaron perfiles superponibles con un máximo hemolítico a 1.000 U/ml de polimixina B. Listeria ivanovii presentó dos picos hemolíticos: uno coincidente con aquél presentado por Listeria monocytogenes y Listeria seeligeri a 1.000 U/ml y un segundo pico a 4.000 U/ml de polimixina B (AU)

Efecto de polimixina B sobre el mecanismo hemolítico del género Listeria / Effect of polymyxin B on the hemolytic mechanism of the genus Listeria

El contacto de polimixina B, sobre hematíes humanos produjo un efecto sobre la actividad hemolítica de las hemolisinas del género Listeria. A bajas concentraciones de antibiótico, se observó un efecto promotor de la hemólisis; verificándose una inhibición de la lisis eritrocitaria a altas concentraciones de polimixina B. Este comportamiento permitió definir perfiles hemolíticos para cada una de las especies hemolíticas del género en estudio. Listeria monocytogenes y Listeria seeligeri presentaron perfiles superponibles con un máximo hemolítico a 1.000 U/ml de polimixina B. Listeria ivanovii presentó dos picos hemolíticos: uno coincidente con aquél presentado por Listeria monocytogenes y Listeria seeligeri a 1.000 U/ml y un segundo pico a 4.000 U/ml de polimixina B

[Effect of polymyxin B on the hemolytic mechanism of the genus Listeria]. / Efecto de polimixina B sobre el mecanismo hemolítico del género Listeria.

The contact between polymyxin B and human blood cells produced a double effect on the haemolytic activity of Listeria monocytogenes, L. seeligeri and L. ivanovii hemolysins. At low polymyxin B concentrations the antibiotic promoted erythrocyte lysis whereas at higher antibiotic levels, hemolysis inhibition was observed. According to the effects of polymyxin B, hemolytic profiles were established for each hemolysin. L. monocytogenes and L. seeligeri exhibited a similar profile with maximum hemolytic activity at 1000 U/ml polymyxin B. L. ivanovii displayed a different profile, with two maximum hemolytic activities: one similar to that showed by L. monocytogenes and L. seeligeri at 1000 U/ml, and another peak of hemolysis at 4000 U/ml polymyxin B.