Survival Of Pathogenic Microorganisms Research Articles

Evaluation of Antioxidant, Antibacterial, and Anti-hemolytic Properties of Ethanol Extract from Plectranthus barbatus Andrews (Lamiaceae) Leaves

Polyphenols can act as antioxidants, antibacterial, antifungal, or insecticidal agents. Given that microbial infections and arboviruses transmitted by Aedes aegypti significantly contribute to global morbidity and mortality, there is an urgent need to discover new antimicrobials and insecticides. This study investigated the ethanol extract (PbLE) of Plectranthus barbatus Andrews (Lamiaceae) leaves for its chemical constituents, antioxidant, antimicrobial, anti-hemolytic, and larvicidal activities. Qualitative analysis by Thin Layer Chromatography revealed cinnamic derivatives, flavonoids, terpenes, and steroids in PbLE. Quantitative analysis showed that PbLE contained 98.64 ± 0.87 mg EAG/g of total phenols, with flavonoids comprising 21.84 ± 0.34 mg EQ/g (c.a. 22%). PbLE demonstrated scavenging activity against ABTS+ (IC50 = 3246.00 ± 0.97 µg/mL) and DPPH (IC50 = 1371.75 ± 0.94 µg/mL) free radicals and exhibited reducing ability in the phosphomolybdenum method (IC50 = 899.33 ± 0.73 µg/mL). Although PbLE did not affect the growth or survival of pathogenic microorganisms, it significantly reduced (c.a. 80% for the extract at 256 mg/mL) the hemolysis caused by Staphylococcus aureus in human erythrocytes. Furthermore, PbLE (7 mg/mL) caused 40% mortality of A. aegypti third-instar larvae after 48-h exposure. In conclusion, PbLE, rich in phenolic compounds, acts as an antioxidant that mitigates S. aureus virulence to human erythrocytes and reduces the viability of A. aegypti larvae. The data reported herein contribute to the science by exploring P. barbatus, a medicinal plant with a long history of traditional use, as source of bioactive compounds with pharmacological and insecticidal properties. The determination of LC50 and mechanisms of PbLE larvicidal activity are underway.

Polyethylene microplastics cooperate with Helicobacter pylori to promote gastric injury and inflammation in mice

Microplastics provide stable habitats for the colonization and survival of pathogenic microorganisms, and cooperate with microorganisms to pose a potential threat to human health. In this study, polyethylene microplastics (PE-MPs) in artificial gastric juice time-dependently decomposed and broke into small-diameter PE-MP fragments that were more stable than those in an aqueous solution. Helicobacter pylori adhered to the surfaces of the PE-MPs to form a biofilm. The gastric tissues of mice treated with PE-MPs first and mixture of PE-MPs and H. pylori were positive for H. pylori infection in the 10th and 14th weeks after treatment, whereas those infected with H. pylori first and H. pylori alone were positive only in the 14th week after treatment. PE-MPs were visible in the gastric, intestinal, and liver tissues of mice treated with PE-MPs. The average diameter of the PE-MP fragments in the liver was greater than those of fragments that entered the gastric or intestinal tissues, and the average diameter of PE-MPs in the PE-MPs only-treated mice was significantly smaller than those of PE-MPs entering the intestinal tissues of the other groups. The infiltration of inflammatory cells was most serious in the mice treated with the mixture of PE-MPs and H. pylori, or with PE-MPs first and then H. pylori. Of all the groups, the gastric organ index and MPO, IL6, and TNF-α levels were highest in the mice treated with the mixture of PE-MPs and H. pylori. These results indicate that the interaction between PE-MPs and H. pylori contributed to the rapid bacterial colonization of gastric mucosal epithelial cells, improved the efficiency of PE-MP entry into tissues, and promoted gastric injury and inflammation in mice. These findings suggest that microplastics may provide a stable habitat for H. pylori, and act synergistically with H. pylori to pose a potential threat to human health.

Identification and mechanistic analysis of an inhibitor of the CorC Mg2+ transporter

SummaryThe CorC/CNNM family of Na+-dependent Mg2+ transporters is ubiquitously conserved from bacteria to humans. CorC, the bacterial CorC/CNNM family of proteins, is involved in resistance to antibiotic exposure and in the survival of pathogenic microorganisms in their host environment. The CorC/CNNM family proteins possess a cytoplasmic region containing the regulatory ATP-binding site. CorC and CNNM have attracted interest as therapeutic targets, whereas inhibitors targeting the ATP-binding site have not been identified. Here, we performed a virtual screening of CorC by targeting its ATP-binding site, identified a compound named IGN95a with inhibitory effects on ATP binding and Mg2+ export, and determined the cytoplasmic domain structure in complex with IGN95a. Furthermore, a chemical cross-linking experiment indicated that with ATP bound to the cytoplasmic domain, the conformational equilibrium of CorC was shifted more toward the inward-facing state of the transmembrane domain. In contrast, IGN95a did not induce such a shift.

Structural basis for the Mg 2+ recognition and regulation of the CorC Mg 2+ transporter

The CNNM/CorC family proteins are Mg2+ transporters that are widely distributed in all domains of life. In bacteria, CorC has been implicated in the survival of pathogenic microorganisms. In humans, CNNM proteins are involved in various biological events, such as body absorption/reabsorption of Mg2+ and genetic disorders. Here, we determined the crystal structure of the Mg2+-bound CorC TM domain dimer. Each protomer has a single Mg2+ binding site with a fully dehydrated Mg2+ ion. The residues at the Mg2+ binding site are strictly conserved in both human CNNM2 and CNNM4, and many of these residues are associated with genetic diseases. Furthermore, we determined the structures of the CorC cytoplasmic region containing its regulatory ATP-binding domain. A combination of structural and functional analyses not only revealed the potential interface between the TM and cytoplasmic domains but also showed that ATP binding is important for the Mg2+ export activity of CorC.

Comparative study of antibacterial assay of Mentha piperita (in vivo and in vitro cultured) leaves extract on enveloped human pathogenic bacteria and its phytochemical screening

The purpose of this study was to examine the effectiveness of mint extract for the control of growth and survival of pathogenic microorganisms that are common cause of infections. Mint plants are rich in a wide variety of secondary metabolites such as tannins, terpenoids, alkaloids, flavonoids, glycosides, steroids, phenol etc. with the help of certain tests which confirm their presence. The antimicrobial activity of mint is due to the presence of various secondary metabolites. Therefore, mint plants can be used to isolate bioactive natural products that may serve as leads in the development of new pharmaceuticals drugs. We use both polar solvent aqueous and ethanol for the extraction of active components from leaves of the plant. Mentha extract showed antimicrobial activity against many bacterial strains like Bacillus subtilis, Enterococcus feacalis and Salmonella typhi. Mint leaves gaves considerable amount of antimicrobial activity higher with ethanol extract and least with water extract. The presence of useful phytochemicals in the samples has proved it to be very important plant both economically as well as medicinally.

Reduction in pathogenic load of wheat by tempering with saline organic acid solutions at different seasonal temperatures

As a raw agricultural commodity, wheat is exposed to microbial contamination; therefore, enteric pathogens may be among its microbiota creating a food safety risk in milled products. This research evaluates (1) the effectiveness of organic acids dissolved in saline solutions to reduce the counts of pathogenic microorganisms in soft and hard wheat, and also investigates the effect of seasonal temperature on (2) survivability of pathogens in wheat kernels and on (3) pathogen inactivation during tempering with saline organic acid solutions. Wheat samples were inoculated with cocktails of either 5 serovars of Salmonella enterica, 5 E. coli O157:H7 or 6 non-O157 Shiga toxin-producing E. coli (STEC) strains to achieve a concentration of ~7 log CFU/g. Inoculated samples were allowed to stand for 7-days at temperatures (2.0, 10.8, 24.2, 32 °C) corresponding to those experienced during winter, spring/fall, and summer (average and maximum) in the main wheat growing regions in the state of Nebraska, USA. Besides water, solutions containing acid (acetic or lactic 2.5% or 5.0% v/v) and NaCl (~26% w/v) were used for tempering the wheat to 15.0% (soft) and 15.5% (hard) moisture at the different seasonal temperatures. The survival of pathogenic microorganisms throughout the resting period, and before and after tempering was analyzed by plating samples on injury-recovery media. The survival rate of pathogenic microorganisms on wheat kernels was higher at temperatures experienced during the winter (2.0 °C) and spring/fall (10.8 °C) months. Regardless of tempering temperature, the initial pathogen load was reduced significantly by all solutions when compared to the control tempered with water (P ≤ .05). The combination of lactic acid (5.0%) and NaCl was the most effective treatment against Salmonella enterica, E. coli O157:H7 and non-O157 STEC, with average reduction values of 1.8, 1.8 and 1.6 log CFU/g for soft wheat and 2.6, 2.4 and 2.4 log CFU/g for hard wheat, respectively. Implementation of organic acids and NaCl in tempering water may have the potential to reduce the risk of pathogen contamination in milled products.

Acinetobacter pittii biofilm formation on inanimate surfaces after long-term desiccation

The survival of pathogenic micro-organisms in the healthcare environment has a major role in nosocomial infections. Among the responsible mechanisms enabling nosocomial pathogens to persist with these stress conditions is their ability to resist desiccation and to form biofilms. To investigate the survival behaviour of Acinetobacter pittii isolates on inert surfaces and saline microcosms. Five A.pittii clinical strains were spotted over white laboratory coat fragments, glass, and plastic surfaces, or inoculated into sterile saline and monitored at room temperature for a period of 43 days. Although the permanence on solid surfaces negatively affected the culturability of the strains used, a fraction of stressed cells survived for at least the period of study. On average, A.pittii culturability was reduced by 77.3%, 80.9%, and 68.1% in white coat, plastic, and glass surfaces, respectively. However, ∼85.6% of the populations retain their culturability in saline solution. Culturability correlated with the presence of cells with an intact membrane, as demonstrated after live/dead staining. Supplementation of the culture medium with sodium pyruvate favoured the culturability of strains from all conditions; but, in general, A.pittii populations did not enter a viable but non-culturable state. After long-term desiccation, all A.pittii strains retained, or even increased, their ability to form biofilms after they had been fed with nutrient media. This suggests that A.pittii may recover easily from desiccation and may express adherence factors to infect new hosts after rehydration.

Interaction between Thermotolerant Coliforms and Rhizobacteria in Soil Fertilized with Treated Domestic Wastewater

ABSTRACT Studies on the survival of pathogenic microorganisms in the soil after use of wastewater for fertilization of agricultural crops report the effects of moisture, pH, organic matter, and soil temperature on microorganisms. There are few studies that assess the survival of these microorganisms in the rhizosphere of plants fertilized with wastewater. Thus, the aim of this study was to quantify the number of fecal coliforms and rhizobacteria (fluorescent Pseudomonas spp., Bacillus spp,) in the rhizosphere of winter and summer [...]

Survival and growth of Salmonella Typhimurium, Escherichia coli O157:H7 and Staphylococcus aureus in eggplant dip during storage

Eggplant dip is an internationally popular appetizer, prepared in some instances under uncertain hygienic conditions with inconsistent refrigeration. This study examined the effects of citric acid on the survival of pathogenic microorganisms (Salmonella Typhimurium, Escherichia coli O157:H7 and Staphylococcus aureus) and naturally present organisms (lactic acid bacteria, LAB, aerobic bacteria, APC and yeast and mold, YM) in eggplant dip during storage. Eggplant dip with 0, 0.2, 0.4, 0.6 or 0.8% citric acid was inoculated with S. Typhimurium, E. coli O157:H7 or S. aureus and stored at 4, 10 and 21°C for ≤15d. Throughout the study, the survival of the inoculated microorganisms was monitored, and LAB, APC, YM numbers and pH were determined. There was no significant (p>0.05) effect of citric acid on inoculated S. Typhimurium and E. coli O157:H7. Salmonella and E. coli O157:H7 survived >7d with little reduction in viability. Reduction of S. aureus viability increased with citric acid concentration and reached>3.0 log10 CFU/g by 15d at 4°C.Citric acid had no effect (p>0.05) on the background YM during storage at 4, 10 and 21°C or LAB stored at 4 and 10°C, while at 21°C, 0.6 and 0.8% citric acid significantly reduced LAB. Citric acid had no effect (p>0.05) on the APC in samples stored at 4°C but it had significant effects on samples stored at 10 and 21°C.Work reported showed that the use of citric acid at 0.4–0.8% can inhibit the growth of S. aureus in eggplant dip, but adequate refrigeration is essential to minimize risk from this and other pathogens in this product.

The sensitivity of bacterial foodborne pathogens to Croton blanchetianus Baill essential oil.

The aim of this study was to assess the activity of essential oil extracted from the leaves of C. blanchetianus Baill, popularly known as “marmeleiro”, in inhibiting the growth and survival of pathogenic microorganisms in food by determining their survival in vitro and by observing the behaviour of Listeria monocytogenes inoculated into a food model (meat cubes) that was stored at refrigeration temperature (7 ± 1 °C) for 4 days. The results indicated a bactericidal effect against Aeromonas hydrophila and Listeria monocytogenes and bacteriostatic action against Salmonella Enteritidis. A bacteriostatic effect on meat contaminated with L. monocytogenes was found for all concentrations of essential oils tested. These results showed that essential oil from the leaves of C. blanchetianus Baill represents an alternative source of potentially natural antimicrobial agents that may be used as a food preservative.

The Effects of a Pickling Process on the Reduction of Escherichia coli O157:H7, Listeria monocytogenes, Salmonella spp. and Staphylococcus aureus Inoculated onto Hard‐Cooked Eggs

AbstractTraditional methods of food preservation, such as pickling, have reemerged as popular approaches for home and commercial food processing. The process of pickling hard‐cooked eggs (HCE) can be an effective method of preventing the growth and survival of pathogenic microorganisms. Because of the variety of pickling processes, HCE manufacturers must validate their pickling process for Food and Drug Administration (FDA) approval and demonstrate 5‐log reductions of pathogens associated with the product. In this study, a rapid one‐step pickling process was evaluated for its ability to reduce Salmonella spp., Listeria monocytogenes, Staphylococcus aureus and Escherichia coli O157:H7 inoculated onto HCE for 14 days at room temperature. All pathogens inoculated onto HCE were reduced by (>5.0 logs) within 24 h and were undetectable following enrichment. The data obtained in this study may be of interest to regulatory officials and processors of HCE seeking pathogen reduction validation for their products.Practical ApplicationsPickling of HCE is an effective preservation method capable of preventing pathogen growth and survival. Although the use of organic acids for food preservation is not a new concept, few published studies have scientifically validated the ability of pickling methods to inhibit pathogen growth and survival on specific foods. Because of the regulatory requirements set forth by the FDA, acidified foods sold commercially must be validated through scientific studies, which demonstrate 5‐log reductions of pathogens associated with the product. Previous studies have utilized a two‐step pickled egg pickling process and demonstrated complete kill of various pathogens within 96 h. In this study, we evaluate a rapid one‐step pickling process utilizing a reformulated pickling solution and produce a complete kill of selected pathogens within 24 h, drastically reducing the cost and increasing the efficiency of a commercial pickled egg pickling process.

CONTROLE DE TEMPO E TEMPERATURA NA PRODUÇÃO DE REFEIÇÕES DE RESTAURANTES COMERCIAIS NA CIDADE DE GOIÂNIA-GOIÁS

All food types are susceptible to contamination by micro-organisms from the storage until the time of distribution. During the processing, there may occur survival and multiplication of micro-organisms in food, if the conditions are favorable, for example, exposure time and temperatures inadequate. This work aimed to analyze the binomial time and temperature, and assess the risks of contamination, survival and multiplication of micro-organisms in foods and preparations, from receipt to distribution of meals in commercial restaurants in Goiânia, state of Goiás . So temperatures were measured and marked the time when these foods were exposed, and applied a check-list tok assessment contamination risk, survival and multiplication of micro-organisms in the preparations evaluated. The results indicated that there is no control of the binomial time and temperature. It was found inadequate temperatures at all stages of production, except for heat treatment. As for food the major mismatches in temperature occurred in the protein dishes, pasta, and salad. We concluded that this control is extremely important for microbiological quality and that some analyzed food types are exposed to risks of contamination, multiplication and / or survival of pathogenic microorganisms.

Distribution of horizontally transferred heavy metal resistance operons in recent outbreak bacteria

Mankind is confronted by the outbreaks of highly virulent and multi-drug resistant pathogens. The outbreak strains often belong to well-known diseases associated species such as Salmonella, Klebsiella and Mycobacterium, but even normally commensal and environmental microorganisms may suddenly acquire properties of virulent bacteria and cause nosocomial infections. The acquired virulence is often associated with lateral exchange of pathogenicity genomic islands containing drug and heavy metal resistance determinants. Metal ions are used by the immune system of macro-organisms against bactericidal agents. The ability to control heavy metal homeostasis is a factor that allows the survival of pathogenic microorganisms in macrophages. In this paper, we investigate the origin of heavy metal resistance operons in the recent outbreak strains and the possible routes which may lead to acquisitions of these genes by potentially new pathogens. We hypothesize that new outbreak microorganisms appear intermittently on an intersection of the non-specialized, genetically naïve strains of potential pathogens and virulence factor comprising vectors (plasmid and/or phages) newly generated in the environmental microflora. Global contamination of the environment and climate change may also have an effect toward the acceleration and appearance of new pathogens.

Antimicrobial Efficacy of Citron Essential Oil on Spoilage and Pathogenic Microorganisms in Fruit‐Based Salads

The aim of this study was the evaluation of the effects of pure citral and citron essential oil on microbial spoilage and growth and survival of pathogenic microorganisms during storage. They were added in the syrup of industrial ready-to-eat fruit salads stored at 9 degrees C. Both citral (25 to 125 ppm) and citron essential oil (300, 600, 900 ppm) were able to prolong the microbial shelf life of the fruit-based salads. The essential oil gave excellent results, avoiding the undesirable effects attributable to the cytotoxicity of citral. Citron essential oil doubled the time needed for the wild microflora to reach concentrations able to produce a perceivable spoilage in condition of thermal abuse (9 degrees C). The same essential oil had reduced effects on the survival of Gram-negative species Salmonella Enteritidis and Escherichia coli, but showed a strong inhibition toward the Gram-positive pathogen Listeria monocytogenes.

Influence of mutation frequency on the persistence of Salmonella enterica serotypes in natural waters

Abstract In aquatic environments, the survival of pathogenic microorganisms, such as Salmonella spp., may represent a risk to public health. The mutation frequency was hypothesized to influence the persistence of Salmonella serotypes in environmental waters. The mean mutation frequency to rifampin resistance of the 11 major serotypes of Salmonella enterica isolated from the Tech River (Pyrénées-Orientales, France) was determined. Then, a comparison of the survival of three serotypes holding different mutation frequencies showed no significant differences, suggesting that a high mutation rate was not directly linked to increased persistence of Salmonella cells under stressful conditions. However, we demonstrated, via controlled experiments, that long-term starvation in natural water could influence the mutation frequency of the Salmonella Typhimurium serotype. This effect, which was not observed for the serotypes Virchow and Infantis, could be a way of adapting to stressful conditions for the serotype Typhimurium and could explain its recurrence in aquatic systems.

Influence of mutation frequency on the persistence of Salmonella enterica serotypes in natural waters

In aquatic environments, the survival of pathogenic microorganisms, such as Salmonella spp., may represent a risk to public health. The mutation frequency was hypothesized to influence the persistence of Salmonella serotypes in environmental waters. The mean mutation frequency to rifampin resistance of the 11 major serotypes of Salmonella enterica isolated from the Tech River (Pyrénées-Orientales, France) was determined. Then, a comparison of the survival of three serotypes holding different mutation frequencies showed no significant differences, suggesting that a high mutation rate was not directly linked to increased persistence of Salmonella cells under stressful conditions. However, we demonstrated, via controlled experiments, that long-term starvation in natural water could influence the mutation frequency of the Salmonella Typhimurium serotype. This effect, which was not observed for the serotypes Virchow and Infantis, could be a way of adapting to stressful conditions for the serotype Typhimurium and could explain its recurrence in aquatic systems.

Survival of legionella pneumophila and salmonella typhimurium in biofilm systems

Biofilms are found in many water supply systems where they form an environment in which different bacteria can be entrapped for long periods. Besides the aesthetic aspect, biofilm has a major contribution in biocorrosion, disinfection inefficiency and possibly may act as a reservoir for pathogenic and non-pathogenic microorganisms. In the present study, two pathogenic bacteria Legionella pneumophila and Salmonella typhimurium WG-49 were introduced into a biofilm simulation flow system supplied with sterile and non-sterile tap water. The survival of these microorganisms into the biofilm formed on glass and PVC coupons at two temperatures (24°C and 36°C) was compared in this system. On glass supports, under sterile conditions at 36°C, Legionella pneumophila sg3 decreased by 6 logs during 40d continuous recirculation. Under non-sterile conditions, L. pneumophila decreased by only half log <48d. S. typhimurium WG-49 under the same conditions showed an increase of 3 logs in the sterile system for 31d, while in the non-sterile system it dropped by only 0.5 log for 20d. At 24°C, L. pneumophila remained stable for >40d under sterile conditions. In non-sterile conditions, L. pneumophila dropped by 1 log for 35d. S. typhimurium, in a sterile system, remained almost unchanged, while in the non-sterile system an increase of 3 logs was observed for the first 21d and thereafter a decrease of 2 logs for the next 21d of the experiment. L. pneumophila on PVC coupons at 36°C survived better compared with glass support. The experimental data show that survival of pathogenic microorganisms into biofilm is variable and depends on many factors, making the survival prediction a difficult task. However, the survival results of L. pneumophila and S. typhimurium in time terms should raise important questions on their potential threat in water distribution systems.

Survival of Legionella pneumophila and Salmonella typhimurium in biofilm systems

Biofilms are found in many water supply systems where they form an environment in which different bacteria can be entrapped for long periods. Besides the aesthetic aspect, biofilm has a major contribution in biocorrosion, disinfection inefficiency and possibly may act as a reservoir for pathogenic and non-pathogenic microorganisms. In the present study, two pathogenic bacteria Legionella pneumophila and Salmonella typhimurium WG-49 were introduced into a biofllm simulation flow system supplied with sterile and non-sterile tap water. The survival of these microorganisms into the biofilm formed on glass and PVC coupons at two temperatures (24°C and 36°C) was compared in this system. On glass supports, under sterile conditions at 36°C, Legionella pneumophila sg3 decreased by 6 logs during 40d continuous recirculation. Under non-sterile conditions, L. pneumophila decreased by only half log <48d. S. typhimurium WG-49 under the same conditions showed an increase of 3 logs in the sterile system for 31d, while in the non-sterile system it dropped by only 0.5 log for 20d. At 24°C, L pneumophila remained stable for >40d under sterile conditions. In non-sterile conditions, L pneumophila dropped by 1 log for 35d. S. typhimurium, in a sterile system, remained almost unchanged. while in the non-sterile system an increase of 3 logs was observed for the first 21d and thereafter a decrease of 2 logs for the next 21d of the experiment. L pneumophila on PVC coupons at 36°C survived better compared with glass support. The experimental data show that survival of pathogenic microorganisms into biofilm is variable and depends on many factors, making the survival prediction a difficult task. However, the survival results of L. pneumophila and S. typhimurium in time terms should raise important questions on their potential threat in water distribution systems.

Pathogen reduction capabilities of freeze/thaw sludge conditioning

Freezing and thawing sludge has become an economically feasible technique of sludge conditioning in regions where natural freezing is available. Even though the dramatic effects of freeze/thaw on dewatering have been studied extensively, its effects on the survival of pathogenic microorganisms have not been investigated. If freeze/thaw conditioning can be shown to reduce pathogenic microorganisms, then sludges treated in this fashion can be disposed of on land with less risk of health effects. In this paper, the effects of freezing rate, temperature and time in the frozen state on the removal of pathogens are tested. The response of seven indicators of microbial contamination; fecal coliforms, Salmonella, plaque forming units, fecal streptococci, poliovirus, helminths and protozoa to the freeze/thawing of both aerobically and anaerobically digested sludges is examined. Fecal coliforms, fecal streptococci, and plaque forming units are chosen as the commonly used indicators of bacteria and viruses, respectively in wastewater sludges. Pathogenic bacteria ( Salmonella), virus (Poliovirus) and parasites ( Ascaris suum and Cryptosporidium parvum) tested in the second phase are chosen as sample microorganisms in their respective classes. Freeze/thaw sludge conditioning is proven to be an effective means of removing most pathogenic microorganisms. Fecal streptococci are found to be the best indicator of the effectiveness of freeze/thawing on enteric bacteria. Results of this study indicate that freeze/thaw conditioning coupled with sludge digestion can significantly enhance the overall pathogenic microorganism reduction achieved in a wastewater treatment plant. Added effectiveness by freeze/thaw treatment may become critical for a plant in meeting the pathogen reduction requirements by U.S. regulations prior to any practice of land application or land disposal of sludge.

MKES Tools: A microbial kinetics expert system for developing and assessing food production systems

MKES Tools is a microbial kinetics expert system for developing food production systems and assessing product safety. The specific information required as input are: (1) a flowchart of the production system, (2) the factors affecting the survival and growth of food-borne pathogens and (3) the ranges of variation for each factor's parameters. With this information, MKES Tools simulates the growth and survival of pathogenic microorganisms when subjected to many different factor/parameter situations. The responses obtained are then used to estimate the significance of each factor's parameters.