Effects of P22 bacteriophage on salmonella Enterica subsp. enterica serovar Typhimurium DMC4 strain biofilm formation and eradication

Over the last decades, several antimicrobial agents have been made available. Due to increasing antimicrobial resistance, bacteriophages were rediscovered for their potential applications against bacterial infections. In the present study, biofilm inhibition and eradication of Salmonella enterica subsp. enterica serovar Typhimurium DMC4 strain (S. Typhimurium) was evaluated with respect to different incubation periods at different P22 phage titrations. The efficacy of P22 phage on biofilm formation and eradication of S. Typhimurium DMC4 strain was screened in vitro on polystyrene and stainless steel surfaces. The biofilm forming capacity of S. Typhimurium was significantly reduced at higher phage titrations (106 pfu/mL ≤). All phage titers (104-108 pfu/mL) were found to be effective at the end of the 24 h-incubation period whereas higher phage titrations were found to be effective at the end of the 48 h and 72 h of incubation. P22 phage has less efficacy on already formed, especially mature biofilms (72 h-old biofilm). Notable results of P22 phage treatment on S. Typhimurium biofilm suggest that P22 phage has potential uses in food systems

The Role Of Stj Fimbrial Operon In The Intestinal Persistence Of Salmonella Typhimurium In Mice

Salmonella Typhimurium contains 13 operons coding for fimbriae with unique binding specificities to host epithelial surfaces. stj operon is only detected in S. Typhimurium genome suggesting that Stj fimbria may effect serovarspecific virulence characteristics. In this study, the role of stj fimbrial operon in the long-term persistence of S. Typhimurium was identified by competitive infection experiment in genetically resistant mouse (CBA) model system. Knock-out mutation of stjA (major subunit of the Stj fimbria) gene reduced recovery of S. Typhimurium from fecal samples and its colonization to spleen, cecum and mesenteric lymph nodes over a 34-day time period (p < 0.05). This data indicate that stj fimbrial operon has a role in long-term intestinal persistence of S. Typhimurium in CBA mice.WoSScopu

THERMAL INACTIVATION KINETICS OF LACTOCOCCUS LACTIS SUBSP LACTIS BACTERIOPHAGE PLL98-22

Survival curves of Lactococcus lactis subsp. lactis bacteriophage pll98 inactivated by heat were obtained at seven temperature values (50-80 degrees C) in M17 broth and skim milk. Deviations from first-order kinetics in both media were observed as sigmoidal shapes in the survival curves of pll98. An empirical model with four parameters was used to define the thermal inactivation. Number of parameters of the model was reduced from four to two in order to increase the robustness of the model. The reduced model produced comparable fits to the full model. Both the survival data and the calculations done using the reduced model (time necessary to reduce the number of phage pll98 six-or seven-log10) indicated that skim milk is a more protective medium than M17 broth within the assayed temperature range

Characterization Of Antibiotic Resistance In Salmonella Enterica Isolates Determined From Ready-To-Eat (Rte) Salad Vegetables

In the last decade, ready-to-eat (RTE) salad vegetables are gaining increasing importance in human diet. However, since they are consumed fresh, inadequate washing during processing can bring on some foodborne illnesses, like salmonellosis, since these food items have natural contamination from soil and water. During 2009–2010, a total of 81 samples were purchased arbitrarily from local markets in Ankara, and were examined for Salmonella contamination. Salmonella screening was performed by using anti-Salmonella magnetic beads system and polymerase chain reaction (PCR) identification of the suspected colonies. Then, the antibiotic resistance profiles of four Salmonella strains identified (strains RTE-1, RTE-2, RTE-3, and RTE-4) were also investigated, since the mechanism by which Salmonella spp. have accumulated antibiotic resistance genes is of interest. All strains showed resistance against sulfonamides (MIC > 128 mg/L). Further results suggested that associated sulfonamide resistance genes were encoded by the 55.0 kb plasmid of strain RTE-1 that involves no integrons. As a result of using two primers (P1254 and P1283) in randomly amplified polymorphic DNA-PCR (RAPD-PCR) analysis, two common amplicons (364 bp and 1065 bp) were determined. The findings of this study provide support to the adoption of guidelines for the prudent use of antibiotics in order to reduce the number of pathogens present on vegetable and fruit farms. Besides, since it is shown that these bacteria started to gain resistance to antibiotics, it is necessary to further investigate the prevalence of them in foods.PubMedWoSScopu

Stress Response Kinetics of Two Nisin Producer Strains of Lactococcus lactis spp. lactis

The purpose of this study is to determine the survival and nisin production behaviors of two strains of Lactococcus lactis under different stress conditions that represent the food ecosystem. In this respect, the survival ratios of two nisin producers were determined under different pH, temperature, NaCl, and bile salt concentrations. Then, nisin production levels of the strains were determined at each stress conditions. Both strains had similar growth or inactivation patterns under the same stress conditions. NaCl and bile salt stresses on the survival ratio of the strains could be successfully described by the exponential decay function, whereas Gaussian function produced good fits for temperature and pH stresses. The nisin activity of two nisin producers (in their mid-exponential and/or early stationary phase) decreased dramatically under all stress conditions, except osmotic (NaCl) and low temperature applications. The results of this study showed that two nisin producers had similar adaptive responses under severe stress conditions, which could be described by appropriate mathematical equations. Moreover, the effect of harsh environment on the nisin activity of L. lactis strains depends on the stress factors applied

Application Of Bacteriocin-Like Inhibitory Substances (Blis)-Producing Probiotic Strain Of Lactobacillus Plantarum In Control Of Staphylococcus Aureus In White-Brined Cheese Production

The aim of this study was to investigate the antimicrobial activity of an autochthonous probiotic strain of bacteriocin-like inhibitory substances (BLIS)-producing Lactobacillus plantarum, previously isolated from a Tulum cheese and satisfied technological criteria as adjunct culture in cheese production, in reducing Staphylococcus aureus during production and ripening of white-brined cheeses. Cheeses were manufactured in two trials from pasteurized milk artificially contaminated with S. aureus to the mean level of 6.243 log MPN mL(-1). Lb. plantarum BG33 was added at 1% as adjunct to the starter culture. The study was also carried out with control group cheeses produced without the adjunct culture. S. aureus counts were monitored for up to 90 days by RAM's 5-tube MPN method and each positive tube of MPN (most probable number) method was confirmed by PCR amplification of a 400 bp fragment of the nuc gene. which encodes the thennostable nuclease of S. aureus. The capacity of lb. plantarunt BG33 to reduce S. aureus count was found as 0.9 log unit on the 18th day of ripening. After 39 and 59 days of ripening, Lb. plantarum BG33 lowered S. aureus count by 1.9 and 2.0 log units, respectively, when compared to control group cheeses in which it was lowered by 0.5 and 1.0 log units, respectively. As a result, the BLIS activity of Lb. plantarum BG33 throughout ripening of white-brined cheese could make it useful as bioprotective adjunct culture in white-brined cheese production to prevent S. aureus growth which is an important foodborne pathogen in respect of safe cheese production.WoSScopu