Antibacterial Activity of Organic Acids on the Growth of Selected Bacteria in Meat Samples

Meat can harbour a large variety of pathogenic and spoilage microorganisms which include mesophilic and psychrophilic bacteria, during slaughtering and further processing. These microorganisms may be sources of infection to human and spoilage of meat. Organic acids are generally recognized as safe antimicrobial agents and the low dilute solutions of organic acids are generally without affecting on the desirable sensory properties of meat; in addition, they do not create residual problems when used as carcass decontaminants. Spray wash treatments utilizing three concentrations (1, 1.5 and 2%) of acetic, lactic, propionic and formic acids (individually and/or in combination of two acids) were performed to evaluate their efficacy in reducing numbers of Escherichia coli O157:H7, Staphylococcus aureus, Listeria monocytogenes, Salmonella Typhimurium and Pseudomonas putida on meat tissues stored at 4±1ºC. The procured beef pieces were decontaminated with hot water and then inoculated with E. coli O157:H7, S. aureus, L. monocytogenes, S. Typhimurium and P. putida seperately which then were spray washed with organic acids for 15 seconds either individually or in combination of two acids separately. The population of E. coli O157:H7, S. Typhimurium, S. aureus, L. monocytogenes and P. putida (P 1.5% concentration > 1% concentration. Mean log reductions of E. coli O157:H7, S. Typhimurium, S. aureus, L. monocytogenes and P. putida showed that the antibacterial effect of formic acid > lactic acid > acetic acid > propionic acid. Combinations of two organic acids indicated a stronger inhibitory effect on selected bacteria compared to the effect of each acid alone. The combinations of acetic and formic, lactic and formic, and propionic and formic acids showed higher reductions effect at ranges of 0.22-1.67, 0.26-1.55, 1.43-1.56, 1.43-1.69 and 0.44-1.59 log10 cfu/ml for E. coli O157:H7, S. Typhimurium, S. aureus, L. monocytogenes and P. putida respectively, more than combinations of acetic and lactic, acetic and propionic, and lactic and propionic acids. The combination of lactic and formic acids showed the highest reduction effect, where more than 3 log10 cfu/ml, of all bacterial species were reduced. The populations of S. aureus and L. monocytogenes as Gram-positive bacteria reduced more significantly (P<0.05) than the population of E. coli O157:H7, S. Typhimurium and P. putida as Gram-negative bacteria. The results of this study indicated that formic acid is a good antibacterial agent for decontaminating animals’ carcass surfaces especially when mixed with lactic acid

Novel approach of vaccination against Brucella abortus 544 based on a combination of fusion proteins, human serum albumin and brucella abortus Lipopolysaccharides.

Lipopolysaccharide (LPS) of Brucella abortus is an essential component for developing the subunit vaccine against brucellosis. B. abortus LPS was extracted by n-butanol, purified by ultracentrifugation and detoxified by alkaline treatment. Pyrogenicity and toxicity of B. abortus LPS and detoxified–LPS (D-LPS) were analyzed and compared with LPS of E. coli. Different groups of mice were immunized intraperitoneally with purified B. abortus LPS, D-LPS, a combination of LPS with human serum albumin (LPS-HSA) and B. abortus S19 bacteria; besides, control mice were inoculated with sterile saline. Two doses of vaccine were given 4 weeks apart. Mice were challenged intraperitoneally with virulent B. abortus 544 strain 4 weeks after the second dose of vaccine. Sera and spleens of mice were harvested 4 weeks after challenge. LPS-B. abortus was 10,000-fold less potent in LAL test and 100-fold less potent in eliciting fever in rabbits than in E. coli LPS. And D-LPS was very less potent in LAL test and eliciting fever in rabbits ordinary LPS. The antibody titer of anti-LPS immunoglobulin G (IgG) was higher than D-LPS. However, mice immunized with either LPS, D-LPS or LPS-HSA vaccines showed a significant protection against infection of the spleen (p<0.01). There was no significant difference between mice immunized with LPS and D-LPS in terms of protection (p<0.99). Therefore, it was concluded that D-LPS and LPS-HSA for B. abortus can be used as safer and more potent vaccines than ordinary LPS-B. abortus vaccine

The Prevalence of ESBLs Producing Klebsiella pneumoniae Isolates in Some Major Hospitals, Iran

Aims of this study were to investigate on antibiotic resistance and molecular epidemiology of K.pneumoniae producing ESBLs isolates of respiratory tract infections in some major hospitals in Iran. K.pneumonaie were obtained of patients with RTI. K. pneumoniae producing ESBLs detected by screening, confirming and PCR methods. During the 12-month period, a total of one hundred and thirteen of K.pneumoniae were found from RTI in three cities in different region of Iran which Sixty seven strains (59.2%) were ESBLs producer. In Ilam hospitals, seventeen strains (43.6%), in Milad hospital, thirty-seven strains (74%) and in Emam Reza hospital, thirteen strains (54.2%) were ESBLs producer. The findings showed that among sixty-seven K.pneumoniae producing ESBLs, Sixty-three strains (94%) were positive for blaSHV, eleven strains (16.4%) contained blaTEM and sixteen strains (23.9%) harbored blaCTX-M. Imipenem was found as an effectiveness antibiotic. In the current study, Majority of the ESBLs production had occurred in Milad hospital in Tehran (74%). In conclusion, spreading ESBL-producing strains is a concern, as it causes limitations to the antimicrobial agents for optimal treatment of patients

Application of proteomics in lab diagnosis

Proteomics is defined as a large-scale study of proteins, in particular their functions and structures. This review was aimed to introduce the application of proteomics in lab diagnosis. Beforehand, we introduce the methods, which were used in proteomics also the advantages and disadvantages of proteomics are challenged. In the end, the necessity of proteomics for understanding the structure, function, and interaction of proteins in different fields of sciences including biomarkers, drug discovery, etc. will be discussed

Practical and Novel Sterilization Approach for the Pathogenic Staphylococcus aureus Bacteria.

Problem statement: Decontaminating meat surfaces has been the big concern of meat industry. Thus, various intervention strategies have been studied to reduce the level of bacteria on animals’ carcass surfaces. Approach: Mixture of different concentrations 1, 1.5 and 2% of acetic, lactic, propionic and formic acids at 1:1 ratio were spray washed on inoculated meat to evaluate their efficacy in reducing numbers of Staphylococcus aureus on meat tissue at 4±1°C. The beef pieces were decontaminated with hot water and then inoculated with S. aureus which then were spray washed with treatments for 15 sec separately. Results: Spray wash combinations of acetic and formic, lactic and formic and propionic and formic acids reduced the number of S. aureus at a range of 1.18-1.43 log cfu mL-1 more than combinations of acetic and lactic, acetic and propionic and lactic and propionic acids on meat tissue. Increasing the concentration of used acids increased the lethality of treatments as lethal effect of 2% concentration >1.5% concentration >1%concentration. Conclusion: Lactic and formic acids Combination showed the strongest lethal effect on S. aureus among other treatments. Moreover, this study showed that the combination of lactic and formic acids treatment is a feasible, safe, and economical decontamination method which is highly recommended for use rather than other combinations or single organic acids

Roles of oxidative stress and Nrf2 signaling in pathogenic and non-pathogenic cells: a possible general mechanism of resistance to therapy

The coordinating role of nuclear factor erythroid-2-related factor 2 (Nrf2) in cellular function is undeniable. Evidence indicates that this transcription factor exerts massive regulatory functions in multiple signaling pathways concerning redox homeostasis and xenobiotics, macromolecules, and iron metabolism. Being the master regulator of antioxidant system, Nrf2 controls cellular fate, influencing cell proliferation, differentiation, apoptosis, resistance to therapy, and senescence processes, as well as infection disease success. Because Nrf2 is the key coordinator of cell defence mechanisms, dysregulation of its signaling has been associated with carcinogenic phenomena and infectious and age-related diseases. Deregulation of this cytoprotective system may also interfere with immune response. Oxidative burst, one of the main microbicidal mechanisms, could be impaired during the initial phagocytosis of pathogens, which could lead to the successful establishment of infection and promote susceptibility to infectious diseases. There is still a knowledge gap to fill regarding the molecular mechanisms by which Nrf2 orchestrates such complex networks involving multiple pathways. This review describes the role of Nrf2 in non-pathogenic and pathogenic cells

Evaluation of sensory and biochemical changes in freshwater catfish stored under vacuum and different modified atmospheres.

The present study was carried out to compare the influence of six different packaging atmospheres (air, vacuum and MAPs including 5% O2 + 40% CO2 + 55% N2, 5% O2 + 60% CO2 + 35% N2, 5% O2 + 80% CO2 + 15% N2 and 100% CO2) on the biochemical and sensory attributes of freshwater catfish fillets stored at 4 °C. Fillets were monitored for biochemical parameters (pH, total volatile bases nitrogen (TVBN), lipid oxidation) and sensory attributes for 21 days. Proximate and fatty acid composition were also determined in fresh fillets. The sensory quality of all fillets was acceptable during the first 13 ± 1 days of storage in air, 16 ± 1 days of storage in vacuum and MAP1, 18 ± 1 days of storage in MAP2 and 20 ± 1 days of storage in MAP3. The overall sensory scores for fillets which were packed under 100% CO2 were higher than the acceptable limit at the end of storage. It was found that fillets consisted of 5.71 g lipid per 100 g which is susceptible to oxidation due to the high amount of unsaturated fatty acids (63.86%) versus saturated fatty acids (31.14%). Vacuum packed and 100% CO2 fillets showed the lowest TBARS values while air-stored samples showed the highest TBA values. TVBN increased negligibly during storage in all treatments and never exceeded the acceptability limit (35 mg N per 100 g). It can be concluded that 100% CO2 was the best evaluated atmosphere for storage of catfish fillets at 4 °C with superior biochemical and sensory attributes

Development of a new recombinant starter culture bacterium for milk coagulation

Milk clotting enzyme is the key factor for the production of different types of cheese. Hence, calf rennet (chymosin) is traditionally used as a milk coagulant in cheese manufacturing. As the increase in cheese manufacturing globally, coincided with a decline in the supply of calf rennet, it became imperative that substitutes for rennet be found. Recently, the use of fungal mucor rennin, in industrial cheese manufacturing, has become prevalent. Lactococcus lactis is a lactic acid bacterium which is generally used as a starter in dairy industries for the production of various types of hard and soft cheeses. Therefore, due to the key role of milk clotting enzyme as well as starter culture bacteria in cheese manufacturing, this study was an attempt to express recombinant mucor rennin (MPR) enzyme by L. lactis to produce milk coagulation enzyme. It is a novel milk clotting procedure using recombinant bacterium capable of milk coagulation. To achieve this, the amplified MPR gene was sub-cloned into pAMJ-LacF expression vector. The food grade pAMJ-LacF expression vector was created by sub-cloning the amplified LacF gene in pAMJ399 vector which lost its erythromycin gene. The recombinant pAMJ-LacF-MPR vector was then electro-transferred into L. lactis NZ3900 and plated onto Elliker-L medium. The plasmid extraction and restriction digestion methods were performed to check the presence of insertion; in addition, the SDS-PAGE and western blotting were carried out to detect the MPR protein expression of recombinant L. lactis carrying MPR gene. The protein assay, milk clotting activity (MCA) and proteolytic activity (PA) of purified recombinant MPR protein were also studied after optimizing the growth rate, and protein expression of recombinant L. lactis carrying MPR gene. Finally, milk coagulation ability of recombinant L. lactis carrying MPR gene was tested. Nucleotide sequencing of DNA insertion from the clone revealed that the MPR activity corresponded to an open reading frame consisting of 1218 bp coding for a 43.45-kDa MPR protein. A clear band on 43.45-kDa size on SDS-PAGE and western blotting confirmed the successful expression of MPR protein by recombinant L. lactis. Optimizing the growth rate of recombinant L. lactis showed the highest cell biomass for the cultures incubated at 33°C. The MPR protein assay results indicated that the highest MPR enzyme, approximately 65.6 μg/ml.h, were obtained for cultures which were incubated at pH 5.5 and 30°C. Statistical analysis of results revealed that there was no significant difference (P<0.05) between MPR protein expression at 30 and 33°C but a significant difference was noted with the expressed MPR protein at 27 and 36°C. Analysis of the mean of the results of milk clotting activity and MCA/PA of purified recombinant MPR protein for the highest purified levels of expressed protein at pH 5.5 and temperatures 30, 33, 27 and 36°C and control showed 870.54, 809.86, 491.85, 358.54 and 651.38 SU/ml for milk clotting activity and 7914, 7362.36, 4471.36, 3259.45 and 5664.17 SU/OD for MCA/PA,respectively. The thermal and pH stability results of purified recombinant MPR protein showed that the recombinant MPR protein is stable at the pH range 3.5–7.5 and thermal stability range 20-50°C. Interestingly, milk coagulation was observed after inoculating milk with recombinant L. lactis carrying MPR gene due to the high expression rate of MPR enzyme by recombinant L. lactis. The mean of the results indicated that the milk coagulated after 220 and 205 min when inoculated milk were incubated at 33°C, under static and agitation conditions, respectively. The curd yield results showed 14.35 g/100ml compared to 13.86 g/100ml solid curd for milk added recombinant L. lactis carrying MPR gene and commercial rennet, respectively. The plasmid stability results also showed that the recombinant pAMJ-LacF-MPR vector has high stability around 88.9% after 200 generations in L. lactis. This study presents novel findings, as the L. lactis was used for the first time as a cell factory for the production of recombinant rennin. In addition, this study introduced a novel milk clotting procedure using recombinant bacterium capable of milk coagulation. The recombinant L. lactis carrying MPR gene, created in this study, has the ability to function as starter culture for acidifying and subsequently coagulating milk by producing mucor rennin as the milk coagulant agent. Thus, these findings would have a significant impact on the cheese industry

Optimized antibacterial measures against Escherichia coli O157:H7 and Staphylococcus aureus

Varied mixtures of different concentrations 1, 1.5 and 2% of acetic (AA), lactic (LA), propionic (PA) and formic (FA) acids at 1:1 ratio were spray-washed on inoculated meat to evaluate their efficacy in reducing loads of Escherichia coli O157:H7 andStaphylococcus aureus on meat tissue. It was found that increasing the concentration of the used organic acids increased the bacterial lethality proportionally. And significant difference (P<0.05) was observed in the lethal effect of different mixtures and concentrations of the used organic acids. As a novel combination, FA treatments as combinations with AA, LA, and PA, especially FA with LA, reduced bacterial loads greatly, up to 3 logs cfu/ml and eradicated inoculated bacteria, E. coli O157:H7 and S. aureuscompletely within 3-6 days. This reduction was higher than that incurred by other combinations. Significantly, higher log reductions by the used organic acids were obtained for S. aureus than for E. coli O157:H7. It was concluded that the combination of LA and FA treatment was a highly promising, feasible, and economical method of decontaminating meat surface from both E. coli O157:H7 and S. aureus bacteria. Moreover, it is safe if compared with other approaches