Bacteriocinogenic Lactococcus lactis subsp. lactis DF04Mi isolated from goat milk: characterization of the bacteriocin

Lactic acid bacteria capable of producing bacteriocins and presenting probiotic potential open innovative technological applications in the dairy industry. In this study, a bacteriocinogenic strain (Lactococcus lactis subsp. lactis DF4Mi) was isolated from goat milk, and studied for its antimicrobial activity. The bacteriocin presented a broad spectrum of activity, was sensitive to proteolytic enzymes, resistant to heat and pH extremes, and not affected by the presence of SDS, Tween 20, Tween 80, EDTA or NaCl. Bacteriocin production was dependent on the components of the culture media, especially nitrogen source and salts. When tested by PCR, the bacteriocin gene presented 100% homology to nisin Z gene. These properties indicate that this L. lactis subsp. lactis DF4Mi can be used for enhancement of dairy foods safety and quality.

Interaction of antimicrobial peptide Plantaricin149a and four analogs with lipid bilayers and bacterial membranes

The amidated analog of Plantaricin149, an antimicrobial peptide from Lactobacillus plantarum NRIC 149, directly interacts with negatively charged liposomes and bacterial membranes, leading to their lysis. In this study, four Pln149-analogs were synthesized with different hydrophobic groups at their N-terminus with the goal of evaluating the effect of the modifications at this region in the peptide's antimicrobial properties. The interaction of these peptides with membrane models, surface activity, their hemolytic effect on red blood cells, and antibacterial activity against microorganisms were evaluated. The analogs presented similar action of Plantaricin149a; three of them with no hemolytic effect (< 5%) until 0.5 mM, in addition to the induction of a helical element when binding to negative liposomes. The N-terminus difference between the analogs and Plantaricin149a retained the antibacterial effect on S. aureus and P. aeruginosa for all peptides (MIC50 of 19 µM and 155 µM to Plantaricin149a, respectively) but resulted in a different mechanism of action against the microorganisms, that was bactericidal for Plantaricin149a and bacteriostatic for the analogs. This difference was confirmed by a reduction in leakage action for the analogs. The lytic activity of Plantaricin149a is suggested to be a result of the peptide-lipid interactions from the amphipathic helix and the hydrophobic residues at the N-terminus of the antimicrobial peptide.

Prevalence of papC and usp Virulence Factors in Uropathogenic Escherichia coli Causing Asymptomatic Urinary Tract Infections in Adolescents.

Aims: To determine the prevalence of two virulence genes associated with uropathogenic Escherichia coli; papC gene of the P fimbriae for adherence to uro-epithelial cells and usp (uropathogen-specific protein) gene, a Vibrio cholerae toxin gene homologue. Study Design: Cross sectional. Place and Duration of Study: Department of Biochemistry and Biotechnology and the Clinical Analysis Laboratory, Kwame Nkrumah University of Science and Technology, Kumasi, between October 2011 and February 2012. Methodology: Escherichia coli isolates (n= 149) from an adolescent population of ages 13- 18 years (from a total sampled population of 85 males and 64 females) were screened for papC and usp, using specific primers for the two genes in polymerase chain reactions. Results: The usp gene was the most prevalent (72.48%), followed by papC (51.00%) and papC+usp (24.16%). Significant difference (P = .002) was observed between papC and usp and also papC and papC+usp (P < .0001). usp Gene prevalence was also significantly different from that of papC+usp (P < .0001). Conclusion: This study suggests that a higher proportion of strains of uropathogenic Escherichia coli implicated in UTI in the studied population possess the usp gene whose protein product potentially serves to reduce competing microbes in the urinary tract.

Genes de virulencia y bacteriocinas en cepas de Enterococcus faecalis aisladas desde diferentes muestras clínicas en la Región del Maule, Chile / Virulence genes and bacteriocins in Enterococcus faecalis strains isolated from different clinical samples in Maule Region, Chile

The presence of virulence genes (VG) and bacteriocins from different clinical samples was studied in Enterococcus faecalis isolated from urinary tract infections (UTI), bacteremia and endodontitis and was correlated with haemolysin and gelatinase activity. We evaluated the presence of VG by PCR in 150 strains of E. faecalis including cylA, aggA, efaA, eep, gelE, esp, as-48, bac31, entL50A/B, entA, entP, entB, enlA andentl071. Haemolysin and gelatinase activity was studied. gelE and cylA genes expressed hemolysin and gelatinase, respectively. This activity was observed in some strains of bacteremia, UTI and endodontitis. The highest number of VG was detected in bacteremic strains, being aggA and entA genes the most frequent. efaA, esp, entA, entL50A/B were associated with their clinical origin (p < 0.05). The most common genetic profile was aggA-eep-enlA-entL50A/B. E. faecalis from UTI, bacteremia and endodontitis presented different gene combinations. Some of the genes studied were related to their clinical origin. The results obtained in this study are similar to those reported in other countries.

Desde diferentes muestras clínicas se determinó la presencia de genes codificantes de factores de virulencia (FV) y bacteriocinas en Enterococcus faecalis aislados desde infecciones del tracto urinario (ITU), bacteriemias y endodontitis, correlacionándose con la actividad hemolisina y gelatinasa. En 150 cepas de E. faecalis fue evaluada mediante RPC la presencia de cylA, aggA, efaA, eep, gelE, esp, as-48, bac31, entL50A/B, entA, entP, entB, enlA, y ent1071 determinándose actividad hemolisina y gelatinasa. Los genes cylA y gelE expresaron hemolisina y gelatinasa, respectivamente. Esta actividad fue observada en algunas de las cepas causantes de bacteriemia, ITU y endodontitis. El mayor número de genes estudiados se detectó en cepas bacteriémicas. Los genes aggA y entA, fueron los más frecuentes. Los genes efaA, esp, entL50/AB y entA se asociaron a su origen clínico (p < 0,05). El perfil genético más recurrente fue aggA-eep-enlA-entL50A/B. Enterococcusfaecalis de ITU, bacteriemias y endodontitis presentaron distintas combinaciones génicas. AAlgunos de los genes estudiados se relacionaron con su origen clínico. Los resultados obtenidos son similares a los reportados en otros países.

Mode of action and in vitro susceptibility of mastitis pathogens to macedocin ST91KM and preparation of a teat seal containing the bacteriocin

Mastitis is considered to be the most economically costly disease affecting the dairy industry. Regular dosage of animals with antibiotics, including use of prophylactic concentrations, may select for resistant strains. The purpose of this study was to determine the mode of action of a new bacteriocin (macedocin ST91KM), to evaluate the antimicrobial resistance of mastitis pathogens to antibiotics commonly used in treatment remedies, and to introduce the possible use of an alternative antimicrobial agent. The bacteriocin macedocin ST91KM, produced by Streptococcus gallolyticus subsp. macedonicus ST91KM, is bactericidal to Streptococcus agalactiae, Streptococcus dysgalactiae, Streptococcus uberis and Staphylococcus aureus associated with mastitis infections, including strains resistant to methicillin and oxacillin. Sensitive cells were deformed and secreted nucleotides, K+ and â-galactosidase when exposed to macedocin ST91KM. Adsorption of the peptide to target cells decreased in the presence of solvents, suggesting that receptors on the cell surfaces have lipid moieties. No adsorption was recorded in the presence of MgCl2, KI and Na2CO3, suggesting that ionic strength plays an important role. A teat seal preparation containing macedocin ST91KM effectively released the peptide and inhibited the growth of S. agalactiae. Macedocin ST91KM could form the basis for alternative dry cow therapy to prevent mastitis infections in dairy cows as it is effective against pathogens that display resistance to conventional antibiotic therapy.

Genetic basis for mutacin N and of its relationship to mutacin I.

BACKGROUND & OBJECTIVES: The mutans streptococci (MS) are a group of 7 species of dental cariesassociated bacteria of which Streptococcus mutans and Streptococcus sobrinus are the most important in humans. Many MS produce bacteriocin-like inhibitory substances (BLIS), some of which have been characterised as small peptides capable of inhibiting the growth of closely-related species. These peptides have most commonly been referred to as mutacins. S. mutans strains N and UA140 appear to have closely similar BLIS activities. Both produce mutacins that seem to target the same species of bacteria. On closer analysis however, these two strains have been shown to produce distinctly different mutacins, known as mutacin N and mutacin I respectively. In the present study the mutacin N structural gene (mutN) was cloned and compared with the mutacin I structural gene (mutA). METHODS: Cloning and sequencing of S. mutans N was done. The distribution of mutN using DNA from 216 streptococcal strains was determined by dot blotting. RESULTS: Mut N was cloned and sequenced from an 1800 bp Bam HI/Eco RI fragment. PCR with the mutN primers mutNF and mutNR on the four mutN-positive strains identified identical bands to S. mutans N. The location of mutN differs significantly from that of mutA in that it is directly upstream of comC, a gene encoding a putative competence stimulating factor. INTERPRETATION & CONCLUSION: The close upstream proximity of mutN to comC suggests a link between mutacin N production and competence development. Further studies need to be done to detect competence-related genes in S. mutans strain N.