Survival Of Pathogenic Bacteria Research Articles

Survival of Pathogenic Bacteria: The Molecular Mechanism of the Heme-responsive Sensor Protein PefR

動物の血液に感染し「ヘム鉄」を栄養として生きている病原菌は，どのようにしてその濃度を感知し，摂りすぎによる毒性を回避しているのだろうか？ヘム濃度センサータンパク質PefRの作動メカニズムから，その謎に迫る．

Effects of sterilization methods on the survival of pathogenic bacteria in potting soil stored at various temperatures

Fresh food products can be contaminated with pathogenic bacteria in various agricultural environments. Potting soil is sterilized by heat sterilization and then reused. This study evaluated the effects of three sterilization methods (non-sterilized, pasteurized, and sterilized) on the survival of pathogenic bacteria in potting soil during storage for 60 days at 5, 15, 25, and 35 °C. The reduction in Escherichia coli O157:H7, Salmonella Typhimurium, and Staphylococcus aureus in potting soil was higher at higher temperatures (25 and 35 °C) than at lower temperatures (5 and 15 °C). The population of pathogenic bacteria in pasteurized and sterilized potting soil was reduced below the detectable levels within 30 days at 35 °C. In contrast, the population of Bacillus cereus did not change in potting soil during storage for 60 days at all temperatures. These results indicate that sterilization and storage temperature of potting soil are critical factors influencing the survival of pathogenic bacteria.

Horizontal Transfer of Virulence Factors by Pathogenic Enterobacteria to Marine Saprotrophic Bacteria during Co-Cultivation in Biofilm.

Environmental problems associated with marine pollution and climate warming create favorable conditions for the penetration and survival of pathogenic bacteria in marine ecosystems. These microorganisms have interspecific competitive interactions with marine bacteria. Co-culture, as an important research strategy that mimics the natural environment of bacteria, can activate silent genes or clusters through interspecies interactions. The authors used modern biotechnology of co-cultivation to dynamically study intercellular interactions between different taxa of bacteria—pathogenic enterobacteria Yersinia pseudotuberculosis and Listeria monocytogenes and saprotrophic marine bacteria Bacillus sp. and Pseudomonas japonica isolated in summer from the coastal waters of the recreational areas of the Sea of Japan. The results of the experiments showed that during the formation of polycultural biofilms, horizontal transfer of genes encoding some pathogenicity factors from Y. pseudotuberculosis and L. monocytogenes to marine saprotrophic bacteria with different secretion systems is possible. It was previously thought that this was largely prevented by the type VI secretion system (T6SS) found in marine saprotrophic bacteria. The authors showed for the first time the ability of marine bacteria Bacillus sp. and P. japonica to biofilm formation with pathogenic enterobacteria Y. pseudotuberculosis and L. monocytogenes, saprophytic bacteria with type III secretion system (T3SS). For the first time, a marine saprotrophic strain of Bacillus sp. Revealed manifestations of hyaluronidase, proteolytic and hemolytic activity after cultivation in a polycultural biofilm with listeria. Saprotrophic marine bacteria that have acquired virulence factors from pathogenic enterobacteria, including antibiotic resistance genes, could potentially play a role in altering the biological properties of other members of the marine microbial community. In addition, given the possible interdomain nature of intercellular gene translocation, acquired virulence factors can be transferred to marine unicellular and multicellular eukaryotes. The results obtained contribute to the paradigm of the epidemiological significance and potential danger of anthropogenic pollution of marine ecosystems, which creates serious problems for public health and the development of marine culture as an important area of economic activity in coastal regions.

BIOCHEMICAL CHARACTERIZATION AND EFFECT OF BACTERIAL BLIGHT ON MICRO AND MACRO NUTRIENT CONCENTRATION IN POMEGRANATE

Bacterial blight is a serious disease of pomegranate. The disease affects the yield and quality of pomegranate fruits. In this present work, we investigated the biochemical characterization and role of micro and macro nutrients in diseased and healthy leaves of pomegranate. Pathogen was isolated infected leaves, twigs and fruits and grown on different culture media. Different biochemical tests (Gram staining, KOH, catalase, oxidase, starch hydrolysis, gelatin liquefaction) were performed to identify the bacteria. All these tests confirm the presence of Xanthomonas axonopodis pv punicae. Pathogenicity was done in the greenhouse using three different methods (Pin-pricked, infiltration and spray method) and symptoms appeared in 8 days; and infiltration method showed early symptoms compared to the spray and pin prick method. Ionic contents (Nitrogen, Potassium, Phosphorus, Magnesium, Calcium, Iron, Boron, Zinc and Copper) are reduced by using these nutrients for the growth, multiplication and survival of pathogenic bacteria. Proper application of these nutrients helps the host plant to improve its physiological and biochemical development and resistance to bacterial blight disease in pomegranate.

Short-chain aurachin D derivatives are selective inhibitors of E.\xa0coli cytochrome bd-I and bd-II oxidases

Cytochrome bd-type oxidases play a crucial role for survival of pathogenic bacteria during infection and proliferation. This role and the fact that there are no homologues in the mitochondrial respiratory chain qualify cytochrome bd as a potential antimicrobial target. However, few bd oxidase selective inhibitors have been described so far. In this report, inhibitory effects of Aurachin C (AurC-type) and new Aurachin D (AurD-type) derivatives on oxygen reductase activity of isolated terminal bd-I, bd-II and bo3 oxidases from Escherichia coli were potentiometrically measured using a Clark-type electrode. We synthesized long- (C10, decyl or longer) and short-chain (C4, butyl to C8, octyl) AurD-type compounds and tested this set of molecules towards their selectivity and potency. We confirmed strong inhibition of all three terminal oxidases for AurC-type compounds, whereas the 4(1H)-quinolone scaffold of AurD-type compounds mainly inhibits bd-type oxidases. We assessed a direct effect of chain length on inhibition activity with highest potency and selectivity observed for heptyl AurD-type derivatives. While Aurachin C and Aurachin D are widely considered as selective inhibitors for terminal oxidases, their structure–activity relationship is incompletely understood. This work fills this gap and illustrates how structural differences of Aurachin derivatives determine inhibitory potency and selectivity for bd-type oxidases of E. coli.

Synergistic potential of herbal plants and conventional antibiotics against multidrug-resistant bacteria

Multidrug-resistant bacteria strains are a threat globally since they are challenging the use of available conventional antibiotics and hence threatening health sectors globally. The spread of these strains has led to a rising rate in mortality and morbidity. There is an alarming urgent need to discover an alternative natural antimicrobial agent that can has potential bioactive compounds to inhibit the drug-resistant strains. The synergistic potential between herbal plants and conventional antibiotics may render alternative therapy possibilities against multidrug-resistant bacteria strains. Herbal plants have phytochemicals that have shown a promising effect against pathogens causing infection in humans, and have been investigated on their significance to inhibit the survival of pathogenic bacteria. The phytochemicals have also shown the potential to prevent genetic mutation in the organisms besides reversing the muted genetic factor into their initial state hence making them susceptible to the drug. Combination therapy of herbal plants and antibiotics increases its efficacy against the pathogen where it could not be denatured by only conventional strategy. Due to these assertions, synergistic activity should be employed as an alternative therapy strategy against multidrug-resistant microorganisms.

Comparative Review of the Responses of Listeria monocytogenes and Escherichia coli to Low pH Stress.

Acidity is one of the principal physicochemical factors that influence the behavior of microorganisms in any environment, and their response to it often determines their ability to grow and survive. Preventing the growth and survival of pathogenic bacteria or, conversely, promoting the growth of bacteria that are useful (in biotechnology and food production, for example), might be improved considerably by a deeper understanding of the protective responses that these microorganisms deploy in the face of acid stress. In this review, we survey the molecular mechanisms used by two unrelated bacterial species in their response to low pH stress. We chose to focus on two well-studied bacteria, Escherichia coli (phylum Proteobacteria) and Listeria monocytogenes (phylum Firmicutes), that have both evolved to be able to survive in the mammalian gastrointestinal tract. We review the mechanisms that these species use to maintain a functional intracellular pH as well as the protective mechanisms that they deploy to prevent acid damage to macromolecules in the cells. We discuss the mechanisms used to sense acid in the environment and the regulatory processes that are activated when acid is encountered. We also highlight the specific challenges presented by organic acids. Common themes emerge from this comparison as well as unique strategies that each species uses to cope with acid stress. We highlight some of the important research questions that still need to be addressed in this fascinating field.

Dataset for transcriptome analysis of Salmonella enterica subsp. enterica serovar Typhimurium strain 14028S response to starvation.

Salmonella enterica is an ubiquitous pathogen throughout the world causing gastroenteritis in humans and animals. Survival of pathogenic bacteria in the external environment may be associated with the ability to overcome the stress caused by starvation. The bacterial response to starvation is well understood in laboratory cultures with a sufficiently high cell density. However, bacterial populations often have a small size when facing this challenge in natural biotopes. The aim of this work was to find out if there are differences in the transcriptomes of S. enterica depending on the factor of cell density during starvation. Here we present transcriptome data of Salmonella enterica subsp. enterica serovar Typhimurium str. 14028S grown in carbon rich or carbon deficient medium with high or low cell density. These data will help identify genes involved in adaptation of low-density bacterial populations to starvation conditions.

The effects of novel bioactive carboxymethyl cellulose coatings on food-borne pathogenic bacteria and shelf life extension of fresh and sauced chicken breast fillets

The aims of the present study were to evaluate the effects of carboxymethyl cellulose (CMC) coatings containing Ziziphora clinopodioides (ZEO; 0, 0.25 and 0.5%) and Mentha spicata (MEO; 0 and 0.5%) essential oils on pathogenic bacteria (i.e. Listeria monocytogenes, Staphylococcus aureus, Escherichia coli O157:H7, Salmonella typhimurium and Campylobacter jejuni) and shelf life extension of fresh and sauced chicken breast fillets under refrigerated condition for two weeks. The order of bacterial spoilage population (i.e. total viable count, psychrotrophic count, Pseudomonas spp., P. fluorescens and Enterobacteriaceae), survival of pathogenic bacteria and lipid oxidation of coated samples are as follows: CMC > CMC + MEO 0.5% > CMC + ZEO 0.25% > CMC + ZEO 0.5% > CMC + ZEO 0.25% + MEO 0.5% > CMC + ZEO 0.5% + MEO 0.5%. Our findings indicated that application of CMC coatings containing ZEO in combination with MEO can reduce the number of test pathogens and increase the shelf life of fresh and sauced chicken breast fillets.

Role of two-component regulatory systems in intracellular survival of Mycobacterium tuberculosis.

The typical two-component regulatory systems (TCSs), consisting of response regulator and histidine kinase, play a central role in survival of pathogenic bacteria under stress conditions such as nutrient starvation, hypoxia, and nitrosative stress. A total of 11 complete paired two-component regulatory systems have been found in Mycobacterium tuberculosis, including a few isolated kinase and regulatory genes. Increasing evidence has shown that TCSs are closely associated with multiple physiological process like intracellular persistence, pathogenicity, and metabolism. This review gives the two-component signal transduction systems in M. tuberculosis and their signal transduction roles in adaption to the environment.

Survival of Escherichia coli O157:H7 and Listeria monocytogenes in an acidified low-fat mayonnaise based hibachi sauce

Survival of pathogenic bacteria under acidic conditions may pose a significant food safety challenge and should be assessed when developing new food products. The objective of this study was to determine the antimicrobial effect of two acidulants against Escherichia coli O157:H7 and Listeria monocytogenes in a low-fat mayonnaise based hibachi sauce subjected to different preparation and storage conditions. A mixture of seasoning and acidulants was heated to 82.2 °C and cooled. This was combined with a low-fat mayonnaise and acidified with either 0.25 g lactic acid/100 g sauce, 0.25 g, or 0.5 g vinegar/100 g sauce. The sauce was then inoculated with L. monocytogenes and E. coli O157:H7 at the levels of ca. 6 log CFU/g each, and stored at 4 or 23 °C. Both pathogens survived longer at 4 than at 23 °C (P < 0.001). Acidulant significantly affected survival of both bacteria (P < 0.001) with the order of average antimicrobial efficacy being 0.25 and 0.5 g lactic acid/100 g sauce > 0.5 g vinegar/100 g sauce > unacidified control. At 23 °C, populations of both bacteria decreased by at least 4 log CFU/g after 72 h of storage in formulations containing 0.25 g lactic acid/100 g sauce. Acidification with lactic acid can improve food safety of mayonnaise based sauces in case of post processing contamination.

The survival of pathogenic bacteria and plant growth promoting bacteria during mesophilic anaerobic digestion in full-scale biogas plants.

The introduction of biogas plants is a promising way to recycle organic wastes with renewable energy production and reducing greenhouse gas. Application of anaerobic digestate as a fertilizer reduces the consumption of chemical fertilizers. In this study, the survival of pathogenic bacteria and plant growth promoting bacteria (PGPB) in two full-scale biogas plants operated at mesophilic condition were investigated. Feedstock and anaerobic digestate samples were collected from biogas plants and bacteria load in samples were detected using standard dilution plate method. Pathogenic bacteria were reduced to not detected level through mesophilic digestion tank except for Campylobacter. However, it could be reduced by 98.7% through a sterilization tank. Bacillus was detected at 8.00 and 7.81 log10 CFU/g dry matter in anaerobic digestates, and it was also resistant to sterilization tank. Bacillus spp. is considered to be the safe bacteria that hold remarkable abilities for promoting plant growth. The results showed that treatment at biogas plants is effective to reduce pathogenic bacteria in dairy manure, and sterilization could further reduce the sanitary risks of pathogenic bacteria relating to anaerobic digestate application. Anaerobic digestates could also be utilized as bio-fertilizer as the high load of plant growth promoting bacteria.

Impact of relative humidity, inoculum carrier and size, and native microbiota on Salmonella ser. Typhimurium survival in baby lettuce

The effects of relative humidity (RH), fluctuating climate conditions, inoculum size and carrier on the survival of Salmonella enterica serovar Typhimurium on baby lettuce in environmental test chambers were studied. Buffered peptone water (BPW), distilled water (DW), and irrigation water (IW) were compared as inoculum carriers. Additionally, survival of Salmonella in suspensions prepared using filtered and unfiltered IW was assessed. Salmonella Typhimurium survived better on baby lettuce plants at high RH independently of the inoculum size. When lettuce plants were grown under fluctuating environmental conditions, Salmonella survival was similar under both RH conditions. Regarding the inoculum carrier, the inoculated microorganism survived better on lettuce plants when BPW was used as carrier both at high and low RH. Survival rate of Salmonella in IW was affected by the presence of native microbiota. Native microbiota present in IW did not affect survival of Salmonella or the levels of mesophilic bacteria on the baby lettuce leaves. The information obtained in the present study contributes to the knowledge on the effect of environmental conditions on pathogenic bacteria survival on growing edible plants. These results are useful when selecting the methodology to carry out experimental studies on the survival of microbial pathogens under different pre-harvest conditions.

PATHOGENIC BACTERIA IN WATERS AND DRINKING WATER-ASSOCIATED BIOFILMS

In this review, the dissemination of bacterial pathogens in natural waters and the mechanisms of their transmission in drinking water, and the role of water-associated biofilms for their survival or growth are discussed. The current state of the studies on biofilm-formation potential of the emerged pathogens in drinking water and the role of interspecies interactions for attachment and survival of pathogenic bacteria in the biofilm community is summarized. The contribution of the biofilms for increasing antimicrobial resistance of pathogens is discussed.

Effects of the Essential Oil from Origanum vulgare L. on Survival of Pathogenic Bacteria and Starter Lactic Acid Bacteria in Semihard Cheese Broth and Slurry

This study assessed the inhibitory effects of the essential oil from Origanum vulgare L. (OVEO) on Staphylococcus aureus, Listeria monocytogenes, and a mesophilic starter coculture composed of lactic acid bacteria (Lactococcus lactis subsp. lactis and L. lactis subsp. cremoris) in Brazilian coalho cheese systems. The MIC of OVEO was 2.5 μl/ml against both S. aureus and L. monocytogenes and 0.6 μl/ml against the tested starter coculture. In cheese broth containing OVEO at 0.6 μl/ml, no decrease in viable cell counts (VCC) of both pathogenic bacteria was observed, whereas the initial VCC of the starter coculture decreased approximately 1.0 log CFU/ml after 24 h of exposure at 10°C. OVEO at 1.25 and 2.5 μl/ml caused reductions of up to 2.0 and 2.5 log CFU/ml in S. aureus and L. monocytogenes, respectively, after 24 h of exposure in cheese broth. At these same concentrations, OVEO caused a greater decrease of initial VCC of the starter coculture following 4 h of exposure. Higher concentrations of OVEO were required to decrease the VCC of all target bacteria in semisolid coalho cheese slurry compared with cheese broth. The VCC of Lactococcus spp. in coalho cheese slurry containing OVEO were always lower than those of pathogenic bacteria under the same conditions. These results suggest that the concentrations of OVEO used to control pathogenic bacteria in semihard cheese should be carefully evaluated because of its inhibitory effects on the growth of starter lactic acid cultures used during the production of the product.

Influence of argon modified atmosphere packaging on the growth potential of strains of Listeria monocytogenes and Escherichia coli

Modified atmosphere packaging (MAP) based on carbon dioxide (CO2) – nitrogen (N2) gas mixtures has been applied to maintain the safety and quality of ready-to-eat (RTE) meat products. The use of argon (Ar) gas as a supplement to CO2–N2 mixtures or as substitute for N2 is a current approach to enhance the effectiveness of MAP. As there is limited information on the effect of Ar MAP on the growth behaviour or the survival of pathogenic bacteria in RTE foods, the aim of the present study was to assess the influence of Ar in MAP on the growth of Listeria monocytogenes and Escherichia coli strains under different conditions. For this purpose, a CO2–N2 (20:80) atmosphere was compared with a CO2–N2–Ar (30:30:40) and CO2–Ar (30:70) atmosphere based on the assessment of bacterial growth (δ) on a gelatin-agar medium and ham. Additionally, a shelf life monitoring study was performed to evaluate the effect of these treatments on the background microflora of ham. The findings suggest that under the CO2–N2 MAP the product matrices supported the growth (δ > 0.5 log CFU g−1) of L. monocytogenes throughout an observation period of 21 days at 4 ± 2 °C. On the contrary, both MAP containing Ar were equally able to reduce the δ below 0.5 log CFU g−1. In this regard it was irrelevant whether L. monocytogenes was inoculated in depth (per slice) or at the surface (top slice) of the ham. Regarding the influence of the different gas atmospheres on E. coli all gas mixtures applied had the capacity to reduce the δ of E. coli below −0.5 log CFU g−1. Further, shelf-life extension could not be managed with the gas atmospheres considered.

Empirical Modeling of Fouling Rate of Milk Pasteurization Process : A case study

Abstract Fouling in heat exchanger becomes a major problem of dairy industry and it increases the production cost. These are lost productivity, additional energy, additional equipment, chemical, manpower, and environmental impact. Fouling also introduces the risk of food safety due to the improper heating temperature which allow the survival of pathogenic bacteria in milk, introducing biofilm formation of pathogenic bacteria in equipments and spreading the pathogenic bacteria to milk. The aim of this study is to determine the fouling rate during pasteurization process in heat exchanger of pasteurized milk produced by Village Cooperative Society (KUD) “X” in Malang, East Java Indonesia by using empirical modeling. The fouling rate is found as 0.3945 o C/h with the heating process time ranged from 0 to 2 hours and temperature difference (hot water inlet temperature and milk outlet temperature) ranged from 0.654 to 1.636 o C. The fouling rate depends on type and characteristics of heat exchangers, time and temperature of process, milk type, age of milk, seasonal variations, the presence of microorganism and more. This results will be used to plan Cleaning In Place (CIP) and to design the control system of pasteurization process in order to maintain the milk outlet temperature as standard of pasteurization.

WS16.2 Highly multiplexed molecular detection of CF lung infections

The acquisition of iron is critical for the survival of pathogenic bacteria including the cystic fibrosis (CF) pathogen B. cenocepacia. Siderophores are low molecular mass iron chelators secreted by bacteria in order to solubilise and internalise ferric iron. Ornibactin is the most abundant of four siderophores produced by B. cenocepacia and is pivotal to the virulence of this opportunistic pathogen. An accurate method of quantifying this important virulence factor will facilitate both pathogenesis studies and the development and evaluation of therapies targeting iron acquisition. Ornibactin was extracted and purified from B. cenocepacia iron-depleted cultures and identified using reverse-phase HPLC and LC-MS analysis. Purified ornibactin was then conjugated to the carrier protein BSA using photo-activation chemistry. Resultant polyclonal antibodies against the ornibactin-conjugate were raised in rabbits and the presence of serum antibodies to both ornibactin and ferric-ornibactin confirmed using immunoblot and Western blot analysis. A competitive ferricornibactin ELISA was then developed by coating ELISA plates with a second ornibactin-BSA conjugate to which the positive rabbit sera and ornibactin positive sample compete for binding. Bound antibodies are detected using an anti-rabbit HRP conjugate which catalyses a colorimetric reaction. The linear range of the ELISA occurs between 0 and 500 ng/ml indicating an extremely sensitive assay. The ferric-ornibactin competitive ELISA is currently under evaluation for the detection of ferric-ornibactin in a range of clinical specimens.

Role of Cold Climate and Freeze–Thaw on the Survival, Transport, and Virulence of Yersinia enterocolitica

Surface and near-surface soils in cold climate regions experience low temperature and freeze-thaw (FT) conditions in the winter. Microorganisms that are of concern to groundwater quality may have the potential to survive low temperature and FT in the soil and aqueous environments. Although there is a body of literature on the survival of pathogenic bacteria at different environmental conditions, little is known about their transport behavior in aquatic environments at low temperatures and after FT. Herein, we studied the survival, transport, and virulence of a Gram-negative bacterial pathogen, Yersinia enterocolitica, when subjected to low temperature and several FT cycles at two solution ionic strengths (10 and 100 mM) in the absence of nutrients. Our findings demonstrate that this bacterium exhibited higher retention on sand after exposure to FT. Increasing the number of FT cycles resulted in higher bacterial cell surface hydrophobicity and impaired the swimming motility and viability of the bacterium. Moreover, the transcription of flhD and fliA, the flagellin-encoding genes, and lpxR, the lipid A 3'-O-deacylase gene, was reduced in low temperature and after FT treatment while the transcription of virulence factors such as ystA, responsible for enterotoxin production, ail, attachment invasion locus gene, and rfbC, O-antigen gene, was increased. Y. enterocolitica tends to persist in soil for long periods and may become more virulent at low temperature in higher ionic strength waters in cold regions.

Inhibition of biofilm formation and antibacterial properties of a silver nano-coating on human dentine

The survival of pathogenic bacteria in the oral cavity depends on their successful adhesion to dental surfaces and their ability to develop into biofilms, known as dental plaque. Bacteria from the dental plaque are responsible for the development of dental caries, gingivitis, periodontitis, stomatitis and peri-implantitis. Certain metal nanoparticles have been suggested for infection control and the management of the oral biofilm. Here, it is shown that application of a silver nano-coating directly on dentine can successfully prevent the biofilm formation on dentine surfaces as well as inhibit bacterial growth in the surrounding media. This silver nano-coating was found to be stable (>98.8%) and to maintain its integrity in biological fluids. Its antibacterial activity was compared to silver nitrate and the widely used clinical antiseptic, chlorhexidine. The bacterial growth and cell viability were quantitatively assessed by measuring the turbidity, proportion of live and dead cells and lactate production. All three bioassays showed that silver nanoparticles and silver nitrate dentine coatings were equally highly bactericidal (>99.5%), while inhibiting bacterial adhesion. However, the latter caused significant dentine discolouration (ΔE* = 50.3). The chlorhexidine coating showed no antibacterial effect. Thus, silver nanoparticles may be a viable alternative to both chlorhexidine and silver nitrate, protecting from dental plaque and secondary caries when applied as a dentine coating, while they may provide the platform for creating anti-biofilm surfaces in medical devices and other biomedical applications.