Modeling and predicting the biofilm formation of Salmonella Virchow with respect to temperature and pH

Biofilm formation of Salmonella Virchow was monitored with respect to time at three different temperature (20, 25 and 27.5 °C) and pH (5.2, 5.9 and 6.6) values. As the temperature increased at a constant pH level, biofilm formation decreased while as the pH level increased at a constant temperature, biofilm formation increased. Modified Gompertz equation with high adjusted determination coefficient (Radj2) and low mean square error (MSE) values produced reasonable fits for the biofilm formation under all conditions. Parameters of the modified Gompertz equation could be described in terms of temperature and pH by use of a second order polynomial function. In general, as temperature increased maximum biofilm quantity, maximum biofilm formation rate and time of acceleration of biofilm formation decreased; whereas, as pH increased; maximum biofilm quantity, maximum biofilm formation rate and time of acceleration of biofilm formation increased. Two temperature (23 and 26 °C) and pH (5.3 and 6.3) values were used up to 24 h to predict the biofilm formation of S. Virchow. Although the predictions did not perfectly match with the data, reasonable estimates were obtained. In principle, modeling and predicting the biofilm formation of different microorganisms on different surfaces under various conditions could be possible

Genetic diversity of food originated Salmonella isolates

Currently, Salmonella enterica is the most common bacterial foodborne pathogen, causing serious extraintestinal disease. Typing methods play an important role on pathogens’ source tracking, knowing the source(s) of bacteria in pharmaceutical sciences, preventing and controlling the diarrhea and food-poisoning outbreaks. The purpose of this study is to use different moleculer typing methods to determine the genetic variability of 38 foodborne Salmonella isolates that were previously identified by biochemical tests. The methods were evaluated by four molecular techniques including 16S rRNA sequencing, PFGE, PCR-RFLP and invA-spvC PCR. 16S rRNA sequencing results showed that four of the 38 isolates were Escherichia coli, Proteus mirabilis and Citrobacter murliniae, and the others were Salmonella enterica. Thirty-eight strains were subtyped by XbaI-PFGE into 20 profiles with different clusters, while they were subtyped by 16S rRNA-RFLP into 9 profiles with a single cluster. Out of two Salmonella isolates, the invasion gene (invA) was detected in all other Salmonella isolates (94%) and the virulence gene (spvC) was detected in 11% of Salmonella isolates. Our results suggested that the PFGE subtyping is the prominent method for the evaluation and benchmarking of molecular subtyping

Regulation of biofilm formation bymarTinSalmonellaTyphimurium

In this study, we aimed at identifying the regulatory role ofmarTgene, known as the regulator ofmisL, on 15 different biofilm-related genes inS.Typhimurium 14028 strain. We also tested the strains for their ability to form biofilm and determined the adherence characteristics of the wild type and the mutant strains of the organism on Caco-2 and HEp-2 cells. For comparative analyses of the candidate genes, individual gene mutations were created via antibiotic gene cassette insertion into each gene of interest.marTgene was cloned behind an arabinose inducible BAD promoter in order to controlmarTexpression. This recombinant plasmid was transfer into each of the 15 mutant strains to investigate the level of expression of each single gene in the presence and absence ofmarTinduction. Besides determination of variations in biofilm formation by each mutant strain, the attachment characteristics of them onto Caco-2 and HEp-2 cell lines were also reported. As a result of attachments experiments on polystyrene surfaces, it was determined that the biofilm production capacity of each mutant strain decreased in a statistically significant manner (p < 0.05). QRT-PCR trials indicated that themarTgene regulates the expression of 14 genes, namelyfimA,fimD,fimF,fimH,stjB,stjC,csgA,csgD,ompC,sthB,sthE,rmbA,fliZandyaiC, in a positive manner. QRT-PCR studies were also revealed that the MarT protein positively regulates its own promoter. When the adherence characteristics of the mutant strains and the wild-type were investigated by using Caco-2 and HEp-2 cells, it was determined that the single gene mutations did have no effect on bacterial adhesion. In view of our mutational analyses and biofilm formation studies, it was concluded thatfliZ,ompC,rmbA,stjBandstjCgenes are related with biofilm formation inSalmonella,besides other cellular functions of them. Taken together, our data suggested that the regulatory role of MarT protein is not only restricted to the regulation ofmisLgene expression, but it rather acts as a general regulator on the biofilm-related genes inSalmonella

Partial characterization of bacteriocins produced by two Lactobacilus strains with probiotic properties

The probiotic characteristics of Lactobacillus brevis BG18 and Lb. plantarum BG33, isolated from traditional Turkish Tulum cheese were assessed. These two bacteriocinproducer strains exhibited good probiotic characteristics such as resistance in media containing 0.3% bile salt, pepsin (3 mg mL–1), and pancreatine (1 mg mL–1) as well as acid resistance at pH 2. They were also adhered to Caco-2 epithelial cells in a manner comparable to Escherichia coli LMG3083 (ETEC) and Salmonella Typhimurium SL1344. The strains produced a heat-stable antimicrobial compound that was shown to be proteinaceous in nature, and therefore, referred to as bacteriocins. The bacteriocins were able to inhibit growth of a number grampositive bacteria such as Listeria monocytogenes, Clostridium botulinum, Staphylococcus aureus and Bacillus cereus. Tricine-SDS-PAGE of the active fraction resulted in single bands with estimated molecular masses of 2.5 kDA and 2.7 kDA for Lb. brevis BG18 and Lb. plantarum BG33 bacteriocins, respectively

Effects of sub-MIC antibiotic concentrations on biofilm production of Salmonella Infantis

In the present study, 13 Salmonella Infantis strains, which have been originated from Turkey, were selected due to their clinical and industrial relevance, sufficient biofilm producing capability and multidrug resistance. Although all tested strains were built up of thin pellicle, optimum pellicle formation has occurred at 28 °C. All S. Infantis biofilms were categorized as ‘bdar’ morphotype following the incubation at both 20 and 28 °C, while they were categorized as ‘saw’ morphotype at 37 °C. Under a certain incubation temperature (28 °C), 84.62% of strains have formed strong biofilm structures. By using the disk diffusion method, high levels of resistance have been observed among tested bacteria against nalidixic acid (100%), spectinomycin (100%), streptomycin (92.3%), tetracycline (92.3%), kanamycin (76.9%) and neomycin (76.9%). Further studies were performed with S. Infantis DMC 12 strain, due to its capability to produce biofilm and multidrug resistance phenotype. Gentamycin (>64 µg/mL, 2 × MIC) and tetracycline (>128 µg/mL, 4 × MIC) were determined as the most effective antibiotics against biofilm formation. The biofilm forms have showed increased antimicrobial resistance when it was compared to the planktonic bacteria. The highest resistance rates of the biofilm bacteria were observed to neomycin (12 × MIC) followed by spectinomycin (10 × MIC) and streptomycin (10 × MIC). Biofilm structure was induced as a result of nalidixic acid, spectinomycin, tetracycline and neomycin treatment at sub-MIC concentrations of tested antibiotics

The role of bcsE gene in the pathogenicity of Salmonella

The effects of the bcsE gene and BcsE protein on bacterial physiology and pathogenicity in SalmonellaTyphimurium and Salmonella Group C1 were investigated. It was observed that biofilm and pellicle formation did not occur in the bcsE gene mutants of wild-type strains. Besides, the 'rdar' (red, dry, rough) biofilm morphotype in wild-type strains changed significantly in the mutants. In terms of the bcsE gene, the swimming and swarming motility in mutant strains showed a dramatic increase compared to the wild-type strains. The Salmonella bcsE gene was cloned into Escherichia coli BL21, and the his-tagged protein produced in this strain was purified to obtain polyclonal antibodies in BALB/c mice. The antibodies were showed labeled antigen specificity to the BscE protein. As a result of immunization and systemic persistence tests carried out with BALB/c mice, BscE protein was determined to trigger high levels of humoral and cellular responses (Th1 cytokine production, IgG2a/IgG1 > 1). Systemic persistence in the liver and spleen samples decreased by 99.99% and 100% in the bcsE mutant strains. Finally, invasion abilities on HT-29 epithelial cells of wild-type strains were utterly disappeared in their bcsE gene mutant strains.This article describes the role of BcsE, which is a c-di-GMP binding protein, in Salmonella biofilm formation properties and pathogenicity