Characterisation of anti‐Staphylococcus aureus activity of quercetin

Although many antibiotics are available for the treatment of bacterial infections, the emergence and global spread of antibiotic‐resistant bacteria is a community‐wide problem. To overcome this problem, we must explore alternative antimicrobials. This study investigated the antibacterial properties of quercetin, a flavonoid present in vegetables and fruits. Quercetin was tested against gram‐positive and gram‐negative bacteria and was found to exert selective antibacterial activity against Staphylococcus aureus, including methicillin‐resistant S. aureus (MRSA), and Staphylococcus epidermidis. Some clinical MRSA strains showed remarkable susceptibility to quercetin. In combination with antibiotics, such as oxacillin, ampicillin, vancomycin, gentamicin, and erythromycin, quercetin showed markedly enhanced antibacterial activity against MRSA. We also report quercetin‐induced aggregation of S. aureus cells; the morphological changes in these cells, as assessed by electron microscopy; and the colony‐spreading ability of quercetin‐sensitive MRSA, all of which revealed the unique antibacterial properties of quercetin against S. aureus.     

Short communication: First detection of Panton-Valentine leukocidin–positive methicillin-resistant Staphylococcus aureus ST30 in raw milk taken from dairy cows with mastitis in South Korea

We identified 199 Staphylococcus aureus isolates from quarter milk samples of 1,289 dairy cattle between 2014 and 2018. About 66% of the isolates were resistant to at least 1 antimicrobial agent; the highest rate of resistance was to penicillin, followed by resistance to ampicillin, erythromycin, and sulfadimethoxine. We obtained 30 methicillin-resistant S. aureus (MRSA) strains from 6 farms in 3 provinces. The MRSA strains exhibited a significantly higher resistance rate to most of the tested antimicrobials than the oxacillin-susceptible strains. The MRSA strains represented 5 genotypes: ST72-t324-SCCmec IV (n = 14), ST30-t1752-SCCmec IV (n = 8), ST188-t189-SCCmec NT (n = 6), ST188-t2284-SCCmec NT (n = 1), and NT-NT-SCCmec IV (n = 1). One of the ST188 MRSA strains represented a novel staphylococcal protein A (spa) type (t2284). In addition, 7 of the 8 ST30 MRSA strains were Panton-Valentine leukocidin (PVL)–positive and carried various staphylococcal enterotoxin encoding genes. This is the first report of PVL-positive ST30 MRSA-t1752-SCCmec IV from bovine mastitis in Korea. All of ST72-t324-SCCmec IV MRSA strains carried staphylococcal enterotoxin and leukotoxin encoding genes. They were also sensitive to most of the tested non-β-lactam antimicrobials. In contrast, ST188-t189 MRSA strains were resistant to multiple antimicrobials and predominantly carried the leukotoxin encoding gene. Taken together, these findings may indicate that dairy cows could be a major source for spreading MRSA strains, and contaminated milk could be a vehicle for transmission. Suitable hygienic measures should be established in dairy farms and processing plants to limit the likelihood of introducing MRSA into the food chain.     

Seeds,fermented foods,and agricultural by-products as sources of plant-derived antibacterial peptides

Abstract

The emergence of bacterial resistance against conventional antibiotics and the growing interest in developing alternative, natural antibacterial agents have prompted the search for plant-derived antibacterial peptides in recent decades. Different classes of endogenous antibacterial peptides have been identified from various plant species. Moreover, protein hydrolysates and hydrolysate-derived peptides with potent antibacterial effects have also been identified from numerous plant sources. Antibacterial peptides are often cationic and amphipathic, consisting of fewer than 100 amino acids. They are able to disrupt bacterial membrane integrity via pore formation and/or compromise bacterial metabolic processes. In this review, we summarize current knowledge on the characteristics and modes of action of antibacterial peptides, as well as salient points concerning the production of antibacterial protein hydrolysates from plant proteins. Examples of plant-derived antibacterial hydrolysates and peptides will be highlighted, with particular attention to less explored seeds, fermented plant foods and agricultural by-products. Promising future research directions with regards to the application of plant-derived antibacterial hydrolysates and peptides in food preservation, farm animal disease management, and nutraceutical/functional food development will be proposed.     

Antibiotic-Resistant Bacteria: A Challenge for the Food Industry

Antibiotic-resistant bacteria were first described in the 1940s, but whereas new antibiotics were being discovered at a steady rate, the consequences of this phenomenon were slow to be appreciated. At present, the paucity of new antimicrobials coming into the market has led to the problem of antibiotic resistance fast escalating into a global health crisis. Although the selective pressure exerted by the use of antibiotics (particularly overuse or misuse) has been deemed the major factor in the emergence of bacterial resistance to these antimicrobials, concerns about the role of the food industry have been growing in recent years and have been raised at both national and international levels. The selective pressure exerted by the use of antibiotics (primary production) and biocides (e.g., disinfectants, food and feed preservatives, or decontaminants) is the main driving force behind the selection and spread of antimicrobial resistance throughout the food chain. Genetically modified (GM) crops with antibiotic resistance marker genes, microorganisms added intentionally to the food chain (probiotic or technological) with potentially transferable antimicrobial resistance genes, and food processing technologies used at sub-lethal doses (e.g., alternative non-thermal treatments) are also issues for concern. This paper presents the main trends in antibiotic resistance and antibiotic development in recent decades, as well as their economic and health consequences, current knowledge concerning the generation, dissemination, and mechanisms of antibacterial resistance, progress to date on the possible routes for emergence of resistance throughout the food chain and the role of foods as a vehicle for antibiotic-resistant bacteria. The main approaches to prevention and control of the development, selection, and spread of antibacterial resistance in the food industry are also addressed.     

Chemical composition, antioxidant and antibacterial properties of the essential oils of Etlingera elatior and Cinnamomum pubescens Kochummen

BACKGROUND: Plant essential oils are widely used as fragrances and flavours. Therefore, the essential oils from the leaves of Cinnamomum pubescens Kochummen (CP) and the whole plant of Etlingera elatior (EE) were investigated for their antioxidant, antibacterial and phytochemical properties. RESULTS: CP and EE were found to contain appreciable levels of total phenolic contents (50.6 and 33.41 g kg^?1 as gallic acid equivalent) and total flavonoid contents (205.6 and 244.8 g kg^?1 as rutin equivalent), respectively. DPPH free radical scavenging activity of CP is superior to EE (P < 0.05) showing IC₅₀ of 77.2 and 995.1 µg mL^?1, respectively. Methicillin‐resistant Staphylococcus aureus (MRSA), Bacillus subtilis, Pseudomonas aeruginosa and Salmonella choleraesuis were tested against CP and EE. Only MRSA was the most susceptible bacteria to CP. GC/MS studies resulted in the identification of 79 and 73 compounds in CP and EE, respectively. The most abundant components of EE included β‐pinene (24.92%) and 1‐dodecene (24.31%). While the major compound in CP were 1,6‐octadien‐3‐ol,3,7‐dimethyl (11.55%), cinnamaldehyde (56.15%) and 1‐phenyl‐propane‐2,2‐diol diethanoate (11.38%). CONCLUSION: This study suggests that the essential oils from Cinnamomum pubescens Kochummen and Etlingera elatior could be potentially used as a new source of natural antioxidant and antibacterial in the food and pharmaceutical industries. Copyright © 2010 Society of Chemical Industry     

Nanostructures for delivery of natural antimicrobials in food

ABSTRACT

Natural antimicrobial compounds are a topic of utmost interest in food science due to the increased demand for safe and high-quality foods with minimal processing. The use of nanostructures is an interesting alternative to protect and delivery antimicrobials in food, also providing controlled release of natural compounds such as bacteriocins and antimicrobial proteins, and also for delivery of plant derived antimicrobials. A diversity of nanostructures are capable of trapping natural antimicrobials maintaining the stability of substances that are frequently sensitive to food processing and storage conditions. This article provides an overview on natural antimicrobials incorporated in nanostructures, showing an effective antimicrobial activity on a diversity of food spoilage and pathogenic microorganisms.     

Anti-Staphylococcal Activity of Eugenia Jambolana L. Against Methicillin–Resistant Staphylococcus Aureus

The antibacterial activity of ethanol extracts of Eugenia jambolana L. and E. uniflora L. (Myrtaceae) were evaluated by agar-well diffusion method and MICs by microdillution method. E. jambolana showed antibacterial activity against MRSA strains (MIC < 1024 μg/mL). E. uniflora did not show significant antibacterial activity (MIC > 1024 μg/mL). It is therefore suggested that extracts from E. jambolana could be used as an anti– Staphylococcus agent. When compared with Methicillin and Gentamicin, the extract was more effective against, being a promising antibacterial agent. Based on the author's knowledge, this is the first report about the antibacterial activity of leave ethanol extract from Eugenia jambolana.     

ANTIBACTERIAL ACTIVITY OF EXTRACTS FROM FAMILY ZINGIBERACEAE AGAINST FOODBORNE PATHOGENS

Chloroformic extracts of selected Thai medicinal plants commonly employed to treat infections were investigated for their antibacterial activity against important foodborne pathogenic bacteria. These included Bacillus cereus, Staphylococcus aureus, methicillin‐resistant S. aureus (MRSA), Escherichia coli O157:H7, Salmonella Typhi and Shigella sp. Among 33 extracts tested, only chloroformic extracts of five plant species exhibited antibacterial properties. Alpinia galanga, Boesenbergia rotunda, Zingiber zerumbet and Piper betel were active against S. aureus. Barleria lupulina was active against B. cereus. Only the extract from P. betel leaves possessed activity against gram‐negative bacteria. As extracts from the three plant species belonging to family Zingiberaceae displayed strong activity against S. aureus, they were further tested against 17 clinical isolates. Minimum inhibitory concentration (MIC) values of B. rotunda, A. galanga and Z. zerumbet extracts against most clinical S. aureus isolates were 0.01, 0.19 and 0.79 mg/mL and the minimum bactericidal concentration (MBC) values were 0.19, 1.57 and >12.5 mg/mL, respectively. Significant growth inhibition of MRSA was observed in the cultures incubated in the presence of the B. rotunda extract, A. galanga and Z. zerumbet. B. rotunda exhibited the greatest activity among the three plant species against S. aureus at MIC, 2MIC and MBC within 2 h.     

Thiol-reactive natural antimicrobials and high pressure treatment synergistically enhance bacterial inactivation

Bacterial inactivation by high pressure (HP) treatment can be strongly enhanced in the presence of antimicrobial compounds, but the mechanism of this synergy is poorly understood. In the present study, screening of thirteen natural antimicrobial compounds (NACs) led to the identification of six NACs that exhibited synergy with HP treatment against eight Gram-negative and two Gram-positive bacteria. The strongest synergy was found with α,β-unsaturated aldehydes (t-cinnamaldehyde, t-2-hexenal, dimethylfumarate), isothiocyanates (allyl isothiocyanate, sulforaphane) and other electrophilic compounds (reuterin). The antibacterial activity of these compounds and their synergistic interaction with HP was linked to thiol reactivity based on (1) their reaction with cysteine in vitro, (2) their reduced minimal inhibitory concentration in an Escherichia coli gshA mutant which is defective in glutathione synthesis, and (3) the loss of synergy with HP in the presence of excess cysteine. These novel insights in the mechanisms leading to synergy will support the development of more effective hurdle technology applications of HP treatment and natural antimicrobials.Industrial relevanceHP treatment is an emerging mild processing technology that offers a better balance between microbiological safety and stability and quality retention compared to traditional heat-based pasteurization methods. The efficacy of microbial inactivation by HP treatment is improved in the presence of natural antimicrobials, but the basis of this synergistic interaction is poorly understood. In the present work, a specific antibacterial mode of action is shown to result in synergy, and this insight will facilitate the development of more effective combined treatments.     

Use of Viburnum Opulus L.(Caprifoliaceae) in Dyeing and Antibacterial Finishing of Cotton

ABSTRACT

It is known that use of chemicals can cause different problems to human health and environment. Therefore, studies to find alternative chemical free finishing processes in textile are now interesting topics. In the light of this, it was tried to minimize chemical uses for antibacterial finishing of cotton by using plant sources “cranberry fruit” and “cranberry fruit branch extract” in dyeing processes. The dyeing experiments were carried out at two different temperatures for different durations. Then, the samples were analyzed in terms of K/S, CIE L*a*b*C* and h° values, light fastness, washing fastness, and antibacterial efficiencies. Consequently, it was found that the two natural dye sources could color the cotton-knitted fabrics, and in general, the washing fastness of dyed samples with both natural dye sources was good, but light fastness values were limited and in dyeing processes by using cranberry fruit branch extract it was poor. Moreover, it was seen that among the tested plantal sources, good antibacterial efficiency against the tested bacteria were obtained with the use of cranberry fruit juice in dyeing processes at low temperature and for lower durations.     

First report of methicillin‐resistant Staphylococcus aureus in tank cultured dusky kob (Argyrosomus japonicus), and evaluation of three phenotypic methods in the detection of MRSA

This study was conducted to ascertain the occurrence of methicillin‐resistant Staphylococcus aureus (MRSA) in marine finfish (Argyrosomus japonicus) harvested from the wild and two re‐circulatory aquaculture systems, and evaluating the reliability of three phenotypic methods in the detection of methicillin resistance. A total of 120 dusky kob fish were sampled for S. aureus detection using conventional methods and confirmed by polymerase chain reaction (PCR) targeting the nuc gene. Methicillin resistance was determined by molecular detection of the mecA gene. Using mecA as the defining standard, the specificities and sensitivities of cefoxitin disc diffusion, oxacillin screen agar, and growth of S. aureus on Brilliance MRSA II Agar were evaluated. A total of 321 presumptive S. aureus isolates were recovered by culture, out of which 202 (62.9%) were confirmed by PCR. Of these, 33 (16.3%) strains were mecA positive while 169 (83.7%) were mecA negative. The sensitivities and specificities of MRSA detection was 93.9 and 91.7%, 81.8 and 92.3%, and 87.9 and 94.1% for cefoxitin disc, oxacillin screen agar test, and Brilliance MRSA II agar, respectively. This is so far the first report of MRSA in dusky kob aquaculture in South Africa. In the absence of molecular techniques, cefoxitin disc diffusion test is recommended along with any other phenotypic method to improve MRSA detection from samples of veterinary origin.

Practical implications

Methicillin‐resistant Staphylococcus aureus currently presents one of the greatest challenges for medical research worldwide, as well as is one of the most important causes of bacteria gastroenteritis due to preformed toxins in foods. There is a dearth of knowledge on marine foods as carriers/sources of MRSA infection. There are also major discrepancies obtained with MRSA detection methods, making effective detection of this pathogen complicated. The results from this study show that healthy aquaculture fish are reservoirs of MRSA, thus it is necessary to regularly monitor marine foods. Cefoxitin disc diffusion test is recommended as the preferred method for detection of MRSA from fish/food samples where molecular methods are lacking.     

Novel approaches in improving the quality and safety aspects of processed meat products through high pressure processing technology - A review

BackgroundIn recent years, there has been growing consumer demand for the minimally processed and chemical additives free Ready-To-Eat (RTE) healthier meat products. On the other hand processed and RTE meat products have been notified as the primary cause for food borne outbreaks in different countries that commonly associated with emerging pathogens such as Salmonella, Listeria monocytogenes and Escherichia coli species.Scope and approachHigh pressure processing (HPP) has been renewed as a best non-thermal intervention for extending the shelf-life and safety of RTE meat products without altering the sensory and nutritional properties. Meat products are complex medium with different physical and chemical compositions that influence the lethality of the microorganisms during HPP. Using high pressure levels (above 600 MPa) for complete sterility of meat products may not be economically feasible more over it may negatively affect the product quality characteristics. The present review aimed to explore the recent research investigations addressed the multi hurdle approaches to increase the effectiveness of HPP at lower processing levels in order to reduce the processing costs and to improve the safety and quality of processed meat products.Key findings and conclusionsThe combination of natural antimicrobials (plant bioactive compounds and bacteriocins) and antioxidants (plant phenolic compounds) as additional hurdles through different mechanisms (active and intelligent packaging) during HPP can definitely be an effective and innovative intervention in ensuring the complete safety of processed meat products. Moreover, the development of low salt meat products with optimum quality attributes can be highly possible through HPP technology.     

Comparison of antimicrobial resistance in Salmonella and Campylobacter isolated from turkeys in the Midwest USA

The current study was carried out to determine the antimicrobial resistance profiles and evaluate some molecular characteristics of a set of Salmonella and Campylobacter isolates recovered from production line turkeys in the Midwest region of the United States. A total of 94 birds identified as being positive for both Salmonella and Campylobacter spp. were selected for study. All Salmonella isolates were examined for antimicrobial resistance using the methods employed in the National Antimicrobial Resistance Monitoring System (NARMS). Campylobacter isolates were subjected to similar analysis using the Etest^®. In addition, polymerase chain reaction (PCR) was carried out to determine the presence of the antimicrobial resistance associated genes, integrase (int1), class 1 integrons (Salmonella and Campylobacter) and a multidrug efflux pump (Campylobacter spp.). Results from the study showed that the Salmonella and Campylobacter isolates examined displayed resistance to a number of antimicrobials, with Salmonella and Campylobacter isolates being resistant to at least three antimicrobials while some isolates showed resistances to 6 or 8 different antimicrobials. In addition, 68.1% of the Salmonella isolates tested were found to be positive for the class I integrase gene (int1), 28.7% possessed a 1000 bp gene cassette and 17% possessed an 800 bp gene cassette. All Campylobacter isolates were negative for int1, but 36.2% tested positive for the Campylobacter multidrug efflux pump (CmeB). A considerable number of Salmonella and Campylobacter isolates tested displayed varying degrees of antimicrobial resistance as well as the presence of some factors associated with the carriage and persistence of antimicrobial resistance. Similarities in the types of antimicrobial resistance observed in Campylobacter and Salmonella strains was evident. The results of this study suggest that prescribing practice at the farm level may be a factor in promoting antimicrobial resistance in more than one species of organism. Such practices may, therefore, contribute to the potential health risk for consumers should micro-organisms carrying multiple antimicrobial resistances enter the food chain. This study may be one of the first to report on the incidence of the multidrug efflux pump (CmeB) in Campylobacters recovered from processed turkeys. The antimicrobial resistance and molecular characteristics of Salmonella and Campylobacter is discussed.     

Antioxidant and antimicrobial activity of Satureja montana L. extracts

BACKGROUND: This study aimed to evaluate the antioxidant and antimicrobial activity of extracts (aqueous, ethanolic and essential oil) from Satureja montana and to characterise the chemical composition of its essential oil. RESULTS: Satureja montana L. essential oil had relatively high antimicrobial activities against the seven species of bacteria tested. In contrast, aqueous extracts did not reveal antibacterial activity, and the ethanol extract was not effective against Salmonella typhimurium. The major volatile constituents of the essential oil were carvacrol (306 g L^?1), thymol (141 g L^?1), and carvacrol methyl ether (63 g L^?1). The strongest antioxidant capacity was obtained with the hot water extracts of S. montana, whereas the plant essential oil revealed the highest phenolic content. CONCLUSION: The findings indicate that the bioactive extracts of S. montana have strong potential for use as natural antimicrobials and antioxidants in the preservation of processed food. Copyright © 2011 Society of Chemical Industry     

The origin of the antibacterial property of bamboo

Bamboo is an eco-friendly and multifunctional plant. Bamboo clothing has recently entered the textile market with a claim for its antimicrobial properties, but without scientific evidence. In this study, the antibacterial activity of plant extracts from Australian-grown bamboo (Phyllostachys pubescens) is investigated. Bamboo extracts were made using water, dimethyl sulphoxide (DMSO) and dioxane and their antibacterial properties were compared against Gram-negative bacteria, Escherichia coli. It was found that the extract made in 20% DMSO aqueous solution showed weak antibacterial activity, whereas the extract made using 90% dioxane aqueous solution exhibited strong antibacterial activity, even after 20 times dilution. The results indicate that antibacterial agents of P. pubescens are located in lignin, not in hemicellulose or other water-soluble chemical components.     

Foodborne Pathogens Prevention and Sensory Attributes Enhancement in Processed Cheese via Flavoring with Plant Extracts

Cheese contaminations with foodborne bacterial pathogens, and their health outbreaks, are serious worldwide problems that could happen from diverse sources during cheese production or storage. Plants, and their derivatives, were always regarded as the potential natural and safe antimicrobial alternatives for food preservation and improvement. The extracts from many plants, which are commonly used as spices and flavoring agents, were evaluated as antibacterial agents against serious foodborne pathogens, for example Listeria monocytogenes, Salmonella Typhimurium, Staphylococcus aureus, and Escherichia coli O157:H7, using qualitative and quantitative assaying methods. Dairy‐based media were also used for evaluating the practical application of plant extracts as antimicrobial agents. Most of the examined plant extracts exhibited remarkable antibacterial activity; the extracts of cinnamon, cloves, garden cress, and lemon grass were the most powerful, either in synthetic or in dairy‐based media. Flavoring processed cheese with plant extracts resulted in the enhancement of cheese sensory attributes, for example odor, taste, color, and overall quality, especially in flavored samples with cinnamon, lemon grass, and oregano. It can be concluded that plant extracts are strongly recommended, as powerful and safe antibacterial and flavoring agents, for the preservation and sensory enhancement of processed cheese.     

Prevalence and characterization of methicillin-resistant Staphylococcus aureus carrying mecA or mecC and methicillin-susceptible Staphylococcus aureus in dairy sheep farms in central Italy

Between January and May 2012, a total of 286 bulk tank milk samples from dairy sheep farms located in central Italy were tested for the presence of Staphylococcus aureus. One hundred fifty-three samples were positive for S. aureus (53.5%), with an average count of 2.53 log cfu/mL. A total of 679 S. aureus colonies were screened for methicillin resistance by the cefoxitin disk diffusion test, and 104 selected cefoxitin-susceptible isolates were also tested for their susceptibility to other antimicrobials representative of the most relevant classes active against Staphylococcus spp. by using the Kirby-Bauer disk diffusion method. Two methicillin-resistant Staphylococcus aureus (MRSA) isolates, carrying respectively the mecA and the mecC genes, were detected in 2 samples from 2 different farms (prevalence 0.7%). The mecA-positive MRSA isolate was blaZ positive, belonged to spa type t127, sequence type (ST)1, clonal complex (CC)1, carried a staphylococcal cassette chromosome mec (SCCmec) type IVa, and was phenotypically resistant to all the β-lactams tested and to erythromycin, streptomycin, kanamycin, and tetracycline. The mecC-positive MRSA isolate was negative for the chromosomally or plasmid-associated blaZ gene but positive for the blaZ allotype associated with SCCmec XI (blaZ-SCCmecXI), belonged to spa type 843, ST(CC)130, carried a SCCmec type XI, and was resistant only to β-lactams. Both MRSA were negative for the presence of specific immune-evasion and virulence genes such as those coding for the Panton-Valentine leucocidin, the toxic shock syndrome toxin 1, and the immune evasion cluster genes. Regarding the presence of the major S. aureus enterotoxin genes, the mecC-positive MRSA tested negative, whereas the ST (CC)1 mecA-positive MRSA harbored the seh gene. Among the 104 methicillin-susceptible S. aureus isolates examined for antimicrobial susceptibility, 63 (60.58%) were susceptible to all the antimicrobials tested, and 41 (39.42%) were resistant to at least 1 antimicrobial. In particular, 23 isolates (22.12%) were resistant to tetracycline, 16 (15.38%) to sulfonomides, 14 (13.46%) to trimethoprim and sulfamethoxazole, and 9 (8.65%) to ampicillin, whereas only 1 isolate was resistant to both fluoroquinolones and aminoglycosides. The high prevalence of S. aureus found in bulk tank milk samples and the isolation of MRSA, although at a low prevalence, underlines the importance of adopting control measures against S. aureus in dairy sheep farms to minimize the risks for animal and public health. Moreover, this study represents the first report of mecC-positive MRSA isolation in Italy and would confirm that, among livestock animals, sheep might act as a mecC-MRSA reservoir. Although this lineage seems to be rare in dairy sheep (0.35% of farms tested), because mecC-positive MRSA are difficult to detect by diagnostic routine methods employed for mecA-positive livestock-associated MRSA, diagnostic laboratories should be aware of the importance of searching for the mecC gene in all the mecA-negative S. aureus isolates displaying resistance to oxacillin, cefoxitin, or both.     

Antibacterial Activities of the Extracts of Some Herbs Used in Turkish Herby Cheese Against Listeria Monocytogenes Serovars

In this study, antimicrobial activities of the four different extracts (in methanol, ethanol, n‐hexane and water) of some herbs including Allium vineale, Chaerophyllum macropodum , and Prangos ferulacea were investigated against Listeria monocytogenes serovars 1/2b, 4b, and 4ab. For many centuries, these herbs were used in food production in Turkey. While water extracts of all the plants did not show any antibacterial activity, the other extracts of these plants showed variable degrees of antibacterial activity against L. monocytogenes serovars tested. The extracts of Allium vineale showed higher antibacterial activity than the other plants. The methanol extracts of all the plants exhibited higher activity than the ethanol and n-hexane extracts. L. monocytogenes 4ab was the most sensitive serovar to extracts of these plants. The results indicated that the methanol and ethanol extracts of these plants displayed remarkable activity against L. monocytogenes serovars and therefore, they could be used as natural anti-Listeria monocytogenes additives in herby cheese.     

A Multiplex PCR Assay for the Rapid and Sensitive Detection of Methicillin‐Resistant Staphylococcus aureus and Simultaneous Discrimination of Staphylococcus aureus from Coagulase‐Negative Staphylococci

Abstract: Methicillin‐resistant Staphylococcus aureus (MRSA) is a global health concern, which had been detected in food and food production animals. Conventional testing for detection of MRSA takes 3 to 5 d to yield complete information of the organism and its antibiotic sensitivity pattern. So, a rapid method is needed to diagnose and treat the MRSA infections. The present study focused on the development of a multiplex PCR assay for the rapid and sensitive detection of MRSA. The assay simultaneously detected 4 genes, namely, 16S rRNA of the Staphylococcus genus, femA of S. aureus, mecA that encodes methicillin resistance, and one internal control. It was rapid and yielded results within 4 h. The analytical sensitivity and specificity of the multiplex PCR assay was evaluated by comparing it with the conventional method. The analytical sensitivity of the multiplex PCR assay at the DNA level was 10 ng DNA. The analytical specificity was evaluated with 10 reference staphylococci strains and was 100%. The diagnostic evaluation of MRSA was carried out using 360 foodborne staphylococci isolates, and showed 99.1% of specificity, 96.4% of sensitivity, 97.5% of positive predictive value, and 97.3% of negative predictive value compared to the conventional method. The inclusion of an internal control in the multiplex PCR assay is important to exclude false‐negative cases. This test can be used as an effective diagnostic and surveillance tool to investigate the spread and emergence of MRSA.     

Sprouting and Solid-State Bioprocessing by Rhizopus oligosporus Increase the In Vitro Antibacterial Activity of Aqueous Soybean Extracts Against Helicobacter pylori

Abstract

Helicobacter pylori infection has been implicated as a major cause of gastric inflammation, peptic ulcer disease, and gastric cancer. While antibiotics have been the mainstay of current therapies for gastrointestinal disease linked to H. pylori infection, negative side-effects and antibiotic resistance issues have strengthened the need for alternative therapeutic strategies. In the search for new antimicrobial agents, much recent research has focused on the potential of dietary phenolic compounds. In this study, soybean extracts enriched for phenolic content via sprouting or solid-state bioprocessing by the dietary fungus Rhizopus oligosporus were investigated for in vitro antibacterial activity against H. pylori. Helicobacter pylori growth inhibition by soybean extracts was increased most effectively by 2?d sprouting or 2?d R. oligosporus bioprocessing. Anti-H. pylori activity was not associated with antioxidant activity, but was linked to extracts when activity of the phenolic-polymerizing enzymes guaiacol peroxidase (in sprouted soybean extracts) and laccase (in R. oligosporus-bioprocessed soybean extracts) were the highest. This suggests the potential involvement of polymeric phenolics in the anti-H. pylori activity of soybean extracts and possible mechanisms for such action are discussed.