Vibrio cholerae O1 and Escherichia coli O157:H7 from drinking water and wastewater in Addis Ababa, Ethiopia.

BACKGROUND: In Addis Ababa, Ethiopia, open ditches along innner roads in residential areas serve to convey domestic wastewater and rainwater away from residences. Contamination of drinking water by wastewater through faulty distribution lines could expose households to waterborne illnesses. This prompted the study to assess the microbiological safety of wastewater and drinking water in Addis Ababa, identify the pathogens therein, and determine their antibiotic resistance patterns. RESULTS VIBRIO CHOLERAE: O1, mainly Hikojima serotype, was isolated from 23 wastewater and 16 drinking water samples. Similarly, 19 wastewater and 10 drinking water samples yielded Escherichia coli O157:H7. V. cholerae O1 were 100% resistant to the penicillins (Amoxacillin and Ampicillin), and 51-82% were resistant to the cephalosporins. About 44% of the V. cholerae O1 isolates in this study were Extended Spectrum Beta-Lactamase (ESBL) producers. Moreover, 26% were resistant to Meropenem. Peperacillin/Tazobactam was the only effective ß-lactam antibiotic against V. cholerae O1. V. cholerae O1 isolates showed 37 different patterns of multiple resistance ranging from a minimum of three to a maximum of ten antimicrobials. Of the E. coli O157:H7 isolates, 71% were ESBL producers. About 96% were resistant to Ampicillin. Amikacin and Gentamicin were very effective against E. coli O157:H7 isolates. The isolates from wastewater and drinking water showed multiple antibiotic resistance against three to eight antibiotic drugs. CONCLUSIONS: Open ditches for wastewater conveyance along innner roads in residence areas and underground faulty municipal water distribution lines could be possible sources for V. cholerae O1 and E. coli O157:H7 infections to surrounding households and for dissemination of multiple drug resistance in humans and, potentially, the environment.

Natural approach of using nisin and its nanoform as food bio-preservatives against methicillin resistant Staphylococcus aureus and E.coli O157:H7 in yoghurt.

BACKGROUND: Natural antimicrobial agents such as nisin were used to control the growth of foodborne pathogens in dairy products. The current study aimed to examine the inhibitory effect of pure nisin and nisin nanoparticles (nisin NPs) against methicillin resistant Staphylococcus aureus (MRSA) and E.coli O157:H7 during the manufacturing and storage of yoghurt. Nisin NPs were prepared using new, natural, and safe nano-precipitation method by acetic acid. The prepared NPs were characterized using zeta-sizer and transmission electron microscopy (TEM). In addition, the cytotoxicity of nisin NPs on vero cells was assessed using the 3-(4,5-Dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) assay. The minimum inhibitory concentrations (MICs) of nisin and its nanoparticles were determined using agar well-diffusion method. Further, fresh buffalo's milk was inoculated with MRSA or E.coli O157:H7 (1 × 106 CFU/ml) with the addition of either nisin or nisin NPs, and then the inoculated milk was used for yoghurt making. The organoleptic properties, pH and bacterial load of the obtained yoghurt were evaluated during storage in comparison to control group. RESULTS: The obtained results showed a strong antibacterial activity of nisin NPs (0.125 mg/mL) against MRSA and E.coli O157:H7 in comparison with control and pure nisin groups. Notably, complete eradication of MRSA and E.coli O157:H7 was observed in yoghurt formulated with nisin NPs after 24 h and 5th day of storage, respectively. The shelf life of yoghurt inoculated with nisin nanoparticles was extended than those manufactured without addition of such nanoparticles. CONCLUSIONS: Overall, the present study indicated that the addition of nisin NPs during processing of yoghurt could be a useful tool for food preservation against MRSA and E.coli O157:H7 in dairy industry.

Characterization of diarrheagenic Escherichia coli from different cattle production systems in Brazil.

Diarrheagenic E. coli (DEC) can cause severe diarrhea and is a public health concern worldwide. Cattle are an important reservoir for this group of pathogens, and once introduced into the abattoir environment, these microorganisms can contaminate consumer products. This study aimed to characterize the distribution of DEC [Shiga toxin-producing E. coli (STEC), enteroinvasive E. coli (EIEC), enteropathogenic E. coli (EPEC), enterotoxigenic E. coli (ETEC), and enteroaggregative E. coli (EAEC)] from extensive and intensive cattle production systems in Brazil. Samples (n = 919) were collected from animal feces (n = 200), carcasses (n = 600), meat cuts (n = 90), employee feces (n = 9), and slaughterhouse water (n = 20). Virulence genes were detected by PCR in 10% of animal samples (94/919), with STEC (n = 81) as the higher prevalence, followed by EIEC (n = 8), and lastly EPEC (n = 5). Animals raised in an extensive system had a higher prevalence of STEC (average 48%, sd = 2.04) when compared to animals raised in an intensive system (23%, sd = 1.95) (Chi-square test, P < 0.001). From these animals, most STEC isolates only harbored stx2 (58%), and 7% were STEC LEE-positive isolates that were further identified as O157:H7. This study provides further evidence that cattle are potential sources of DEC, especially STEC, and that potentially pathogenic E. coli isolates are widely distributed in feces and carcasses during the slaughter process.

Survival of O157 and non-O157 shiga toxin-producing Escherichia coli in Korean style kimchi.

Korean style kimchi contaminated with Shiga toxin-producing Escherichia coli (STEC) O157:H7 was the cause of an outbreak in Canada from December 2021 to January 2022. To determine if this STEC O157:H7 has greater potential for survival in kimchi than other STEC, the outbreak strain and six other STEC strains (O26:H11, O91:H21, O103:H2, O121:H19, and two O157:H7) were inoculated individually at 6 to 6.5 log CFU/g into commercially sourced kimchi and incubation at 4 °C. At intervals of seven days inoculated and control kimchi was plated onto MacConkey agar to enumerate lactose utilising bacteria. The colony counts were interpreted as enumerating the inoculated STEC, since no colonies were observed on MacConkey agar plated with uninoculated kimchi. Over eight weeks of incubation the pH was stable at 4.10 to 4.05 and the STEC strains declined by 0.7-1.0 log, with a median reduction of 0.9 log. The linear rate of reduction of kimchi outbreak STEC O157:H7 was -0.4 log per 30 days (Slope Uncertainty 0.05), which was not significantly different from the other O157 and nonO157 STEC strains (P = 0.091). These results indicate that the outbreak was not due to the presence of strain better adapted to survival in kimchi than other STEC, and that STEC can persist in refrigerated Korean style kimchi with a minimal decline over the shelf-life of the product.

Fates of attached E. coli o157:h7 on intact leaf surfaces revealed leafy green susceptibility.

Leafy greens, especially lettuce, are repeatedly linked to foodborne outbreaks. This paper studied the susceptibility of different leafy greens to human pathogens. Five commonly consumed leafy greens, including romaine lettuce, green-leaf lettuce, baby spinach, kale, and collard, were selected by their outbreak frequencies. The behavior of E. coli O157:H7 87-23 on intact leaf surfaces and in their lysates was investigated. Bacterial attachment was positively correlated with leaf surface roughness and affected by the epicuticular wax composition. At room temperature, E. coli O157:H7 had the best growth potentials on romaine and green-leaf lettuce surfaces. The bacterial growth was positively correlated with stomata size and affected by epicuticular wax compositions. At 37 °C, E. coli O157:H7 87-23 was largely inhibited by spinach and collard lysates, and it became undetectable in kale lysate after 24 h of incubation. Kale and collard lysates also delayed or partially inhibited the bacterial growth in TSB and lettuce lysate at 37 °C, and they sharply reduced the E. coli O157:H7 population on green leaf lettuce at 4 °C. In summary, the susceptibility of leafy greens to E. coli O157:H7 is determined by a produce-specific combination of physiochemical properties and temperature.

Hybrid nanoflower-based electrochemical lateral flow immunoassay for Escherichia coli O157 detection.

An electrochemical biosensor has been developed for detection of Escherichia coli O157 by integrating lateral flow with screen-printed electrodes. The screen-printed electrodes were attached under the lateral flow detection line, and organic-inorganic nanoflowers prepared from E. coli O157-specific antibodies as an organic component were attached to the lateral flow detection line. In the presence of E. coli O157, an organic-inorganic nanoflower-E. coli O157-antimicrobial peptide-labelled ferrocene sandwich structure is formed on the lateral flow detection line. Differential pulse voltammetry is applied using a smartphone-based device to monitor ferrocene on the detection line. The resulting electrochemical biosensor could specifically detect E. coli O157 with a limit of detection of 25 colony-forming units mL-1. Through substitution of antibodies of organic components in organic-inorganic nanoflowers, biosensors have great potential for the detection of other pathogens in biomedical research and clinical diagnosis.

A ratiometric SERS aptasensor based on catalytic hairpin self-assembly mediated cyclic signal amplification strategy for the reliable determination of E. coli O157:H7.

A ratiometric SERS aptasensor based on catalytic hairpin self-assembly (CHA) mediated cyclic signal amplification strategy was developed for the rapid and reliable determination of Escherichia coli O157:H7. The recognition probe was synthesized by modifying magnetic beads with blocked aptamers, and the SERS probe was constructed by functionalizing gold nanoparticles (Au NPs) with hairpin structured DNA and 4-mercaptobenzonitrile (4-MBN). The recognition probe captured E. coli O157:H7 specifically and released the blocker DNA, which activated the CHA reaction on the SERS probe and turned on the SERS signal of 6-carboxyl-x-rhodamine (ROX). Meanwhile, 4-MBN was used as an internal reference to calibrate the matrix interference. Thus, sensitive and reliable determination and quantification of E. coli O157:H7 was established using the ratio of the SERS signal intensities of ROX to 4-MBN. This aptasensor enabled detection of 2.44 × 102 CFU/mL of E. coli O157:H7 in approximately 3 h without pre-culture and DNA extraction. In addition, good reliability and excellent reproducibility were observed for the determination of E. coli O157:H7 in spiked water and milk samples. This study offered a new solution for the design of rapid, sensitive, and reliable SERS aptasensors.

Lcn2 deficiency accelerates the infection of Escherichia coli O157:H7 by disrupting the intestinal barrier function.

Bacterial infections result in intestinal inflammation and injury, which affects gut health and nutrient absorption. Lipocalin 2 (Lcn2) is a protein that reacts to microbial invasion, inflammatory responses, and tissue damage. However, it remains unclear whether Lcn2 has a protective effect against bacterial induced intestinal inflammation. Therefore, this study endeavors to investigate the involvement of Lcn2 in the intestinal inflammation of mice infected with Enterohemorrhagic Escherichia coli O157:H7 (E. coli O157:H7). Lcn2 knockout (Lcn2-/-) mice were used to evaluate the changes of inflammatory responses. Lcn2 deficiency significantly exacerbated clinical symptoms of E. coli O157:H7 infection by reducing body weight and encouraging bacterial colonization of. Compared to infected wild type mice, infected Lcn2-/- mice had significantly elevated levels of pro-inflammatory cytokines in serum and ileum, including interleukin (IL)-6, IL-1ß, and tumor necrosis factor-α (TNF-α), as well as severe villi destruction in the jejunum. Furthermore, Lcn2 deficiency aggravated intestinal barrier degradation by significantly reducing the expression of tight junction proteins occludin and claudin 1, the content of myeloperoxidase (MPO) in the ileum, and the number of goblet cells in the colon. Our findings indicated that Lcn2 could alleviate inflammatory damage caused by E. coli O157:H7 infection in mice by enhancing intestinal barrier function.

Occurrence of Escherichia Coli O157:H7 in lactating cows and dairy farm environment and the antimicrobial susceptibility pattern at Adami Tulu Jido Kombolcha District, Ethiopia.

BACKGROUND: Food-borne pathogens are the foremost causes of food-borne human illness in the world. Escherichia coli O157:H7 (E. coli O157:H7) is one of the major food-borne pathogenic bacteria around the world. Though evidence is lacking; especially in developing countries like Ethiopia, the potential health impact of E. coli O157:H7 can be high where food production, handling and consumption is often taking place under unhygienic conditions. In Ethiopia, studies reported E. coli and E. coli O157: H7 from food of animal origin, mainly meat and milk, and also animal surfaces and feces. The objective of the present study was to investigate the occurrence of E. coli O157:H7 in raw milk and the dairy production farm environment and further assess the antimicrobial resistance pattern of the bacterium. METHODS: Samples of milk from individual lactating cows' and dairy farm environmental samples (feces, water and manure) were collected at Adami Tulu Jido Kombolcha district (ATJKD) and analyzed for the presence of E. coli O157:H7. Standard microbiological techniques including culture, biochemical testing and serological test were performed to isolate and identify the bacterium. The bacterial isolates were evaluated for antimicrobial susceptibility patterns using disk diffusion method. A questionnaire was used to collect possible factors affecting E. coli O157:H7 occurrence. RESULTS: The overall prevalence of E. coli O157:H7 was 4.7% (19/408) (95% CI: 2.6; 6.7). Out of 19 E. coli O157:H7 isolates, 4/50, 7/154, 2/50, and 6/154 were from water, milk, manure, and feces samples, respectively. From potential risk factors considered in this study area, floor type, cleaning of pens, milking location and hand washing during the time of milking were significantly associated with the occurrence of E. coli O157:H7. The antimicrobial susceptibility pattern indicated varying degrees of resistance. All of the isolates were found to be resistant ampicillin, cephalothin, and rifampin, and 100% susceptibility was observed against the drugs: chloramphenicol, ciprofloxacin, gentamicin, nalidixic acid, kanamycin, and tetracycline. Concerning streptomycin, 63.15% of the isolates were susceptible and 36.8% showed intermediate susceptibility. CONCLUSIONS: The occurrence of multi-drug resistance E. coli O157:H7 observed both in lactating cows and in dairy farm environments can sustain a continuous transmission of the bacteria. The occurrence of multidrug-resistant E. coli o157:H7could hamper the control and prevention efforts.

Establishment of real-time fluorescence and visual LAMP for rapid detection of Escherichia coli O157:H7 and kits construction.

Escherichia coli O157:H7 is a common pathogenic bacterium in food and water that can pose a threat to human health. The aim of this study was to develop loop-mediated isothermal amplification (LAMP) method for the detection of E. coli O157:H7 in food based on the specific gene Ecs_2840 and to construct rapid detection kits based on the established methods. Specifically, we established two methods of real-time fluorescent LAMP (RT-LAMP) and visual LAMP with calcein as an indicator. In pure bacterial culture, the cell sensitivity and genomic sensitivity of the RT-LAMP kit were 8.8 × 100 CFU ml-1 and 4.61 fg µl-1, respectively. The sensitivity of the visual LAMP kit was 2.35 × 100 CFU ml-1 and 4.61 fg µl-1. Both kits had excellent specificity and anti-interference performance. In addition, milk inoculated with 2.26 × 100 CFU ml-1E. coli O157:H7 could be detected within the reaction time after enrichment for 3 h. The results showed that the LAMP kits were rapid, sensitive, and specific for the detection of E. coli O157:H7 in food and had good application prospects in food safety surveillance.

Growth models for Salmonella, E. coli O157:H7 and L. monocytogenes give different predictions for pathogen growth in cut leafy greens transportation, but are consistent in identifying higher risk conditions.

Leafy greens are frequently implicated in foodborne disease outbreaks and cut-leafy greens are a food that requires time and temperature control for safety. Predictive microbiology uses mathematical models to predict the growth of bacteria based on environmental conditions. The objective of our study was to compare published square root growth models for Salmonella (n = 6), pathogenic E. coli (n = 6) and Listeria monocytogenes (n = 4) using real world transport temperature data. Data from trucks transporting fresh-cut leafy greens during cross-country shipments were used as temperature inputs to the models. Bacterial growth was computed using the temperatures from each probe in every truck over the duration of transit, which resulted in 12-18 growth predictions per truck for each model. Each model generally gave significantly different predictions than other models for the same organism. The exception was for the two Salmonella models predicting the least growth and the two Salmonella models predicting the most growth which gave predictions that were not significantly different. Although different models tended to give different predictions, their ability to rank risk by truck was generally consistent across models. While absolute risk might be dependent upon choice of model, relative risk is independent of model choice.

Adhesion of Escherichia coli O157:H7 during sublethal injury and resuscitation: Importance of pili and surface properties.

Escherichia coli O157:H7 can recover from sublethally injured (SI) state, which causes threat of foodborne illness. Adhesion plays a key role in the carriage of pathogens in food. In this study, we investigated the adhesion ability of SI and recovered E. coli O157:H7 wildtype and its three pili-deficient mutants (curli, type 1 fimbriae, and type IV pili) on six food-related surfaces. Plate counting was used to determine adhesion population after washing and oscillating the surfaces. Spinach exhibited the stronger adhesion population of E. coli O157:H7 than the other fresh produces (p < 0.05). In addition, at least one key pili dominated adhesion on these surfaces, and curli was always included. The adhesion population and contribution of different types of pili were jointly affected by surface and physiological state. This can be attributed to high hydrophobicity and positive charge density on surface and different expression levels of csgB, fimA, fimC and ppdD in SI and recovered cells. Among glucose, mannose, maltose, fructose, lactose, and sucrose, addition of 0.5% mannose could reduce adhesion of cells at all physiological states on stainless steel. Overall, this research will provide support for controlling adhesion of SI and recovered E. coli O157:H7.

The conjugative transfer of plasmid-mediated mobile colistin resistance gene, mcr-1, to Escherichia coli O157:H7 and Escherichia coli O104:H4 in nutrient broth and in mung bean sprouts.

The emergence of mobile colistin resistant gene (mcr-1) in Enterobacteriaceae has become a global public health concern. Dissemination of the mcr-1 gene through conjugation of bacteria associated with food may occur. This research investigated the transfer frequency of the mcr-1 gene among Escherichia coli in liquid media and during growth of mung bean sprouts. The donor strain E. coli NCTC 13846 (mcr-1 positive) and recipient strains of E. coli O157:H7 and E. coli O104:H4 were used. Mating experiments in vitro were conducted at 4, 25, and 37 °C for up to 36 h. The in vivo mating experiments (growing sprouts) were conducted in a sprout growth chamber with irrigation of 1 min/h over 6 days following inoculation of mung bean seeds with the donor and a recipient. The highest transfer frequencies in TSB media, 2.86E-07 and 3.24E-07, occurred at 37 °C after mating for 24 h for E. coli O104:H4 and E. coli O157:H7, respectively. Transconjugants were not detected in liquid media at 4 °C. Moreover, transfer frequency (5.68E-05 per recipient) of mcr-1 was greater during mung bean sprout growth for E. coli O104:H4 compared to E. coli O157:H7 (1.02E-05 per recipient) Day 3 to Day 6. This study indicates that the transfer of antibiotic resistant gene(s) among bacteria during mung bean sprout production may facilitate the spread of antibiotic resistant bacteria in the environment and to humans.

Acid shock protein Asr induces protein aggregation to promote E. coli O157:H7 entering viable but non-culturable state under high pressure carbon dioxide stress.

Under stressful conditions, bacteria can enter viable but non-culturable (VBNC) state to survive. VBNC cells lost ability to grow on routine culture medium but are still alive and may revive in suitable conditions. The revived cells can consume nutrients or produce toxins, leading to food spoilage or human illness, posing great risk to food safety and public health. Previously, we have reported that high pressure carbon dioxide (HPCD), an environment-friendly sterilization technology, can induce VBNC formation. However, the underlying mechanism is unclear. By performing a comprehensive transcriptomic analysis, we revealed that HPCD initiated high expression of asr, encoding an acid shock protein, could promote VBNC formation of E. coli O157:H7. Quantitative reverse transcription PCR analysis suggested that high expression of asr (i) inhibited acid resistance (AR) systems, resulting in endogenous proton accumulation; (ii) inhibited hchA expression, a protein stabilizing factor. The two effects resulted in endogenous protein aggregation, which was highly correlated to VBNC formation. Accordingly, HPCD-stressed cells exhibited decreased efficiency of electron transfer chain and ATP production, which was also contributory to cytoplasmic protein aggregation. Taken together, HPCD-initiated high expression of Asr coupled with decreased ATP production led to protein aggregation, finally promoted the cells to enter VBNC state.

Rapid and sensitive detection of E. coli O157:H7 by lateral flow immunoassay and silver enhancement.

The aim of this study was to develop a sensitive lateral flow immunoassay (LFIA) for the rapid detection of Escherichia coli (E. coli) O157:H7, a pathogen contributor to diseases and fatalities worldwide. Au nanoparticles with high stability, uniform size, and shape were synthesized and coated with heterobifunctional PEG polymer with carboxyl groups, and they were bioconjugated to be used as label in sandwich-LFIA. Then, a silver enhancement strategy was developed as an accessible, rapid, and cost-effective approach for signal amplification to reduce the limit of detection (LOD). The optimal results were achieved when a solution of silver nitrate and hydroquinone/citrate buffer was added to the strips for 4 min. This led to a decrease in the visual LOD from 2 × 106 (CFU mL-1) to 2 × 103 (CFU mL-1), resulting in a threefold improvement in sensitivity compared to the conventional LFIA system. The specificity of the system was evaluated by using non-target bacteria (E. coli BL21 and E. coli T515) and its reliability was determined by testing commercial food samples (milk, tap water, and orange juice), demonstrating its effectiveness for quickly detecting pathogenic bacteria in food products.

Isolation, Characterization, and Comparative Genomic Analysis of Bacteriophage Ec_MI-02 from Pigeon Feces Infecting Escherichia coli O157:H7.

The most significant serotype of Shiga-toxigenic Escherichia coli that causes foodborne illnesses is Escherichia coli O157:H7. Elimination of E. coli O157:H7 during food processing and storage is a possible solution. Bacteriophages have a significant impact on bacterial populations in nature due to their ability to lyse their bacterial host. In the current study, a virulent bacteriophage, Ec_MI-02, was isolated from the feces of a wild pigeon in the United Arab Emirates (UAE) for potential future use as a bio-preservative or in phage therapy. Using a spot test and an efficiency of plating analysis, Ec_MI-02 was found to infect in addition to the propagation host, E. coli O157:H7 NCTC 12900, five different serotypes of E. coli O157:H7 (three clinical samples from infected patients, one from contaminated green salad, and one from contaminated ground beef). Based on morphology and genome analysis, Ec_MI-02 belongs to the genus Tequatrovirus under the order Caudovirales. The adsorption rate constant (K) of Ec_MI-02 was found to be 1.55 × 10-8 mL/min. The latent period was 50 min with a burst size of almost 10 plaque forming units (pfu)/host cell in the one-step growth curve when the phage Ec_MI-02 was cultivated using the propagation host E. coli O157:H7 NCTC 12900. Ec_MI-02 was found to be stable at a wide range of pH, temperature, and commonly used laboratory disinfectants. Its genome is 165,454 bp long with a GC content of 35.5% and encodes 266 protein coding genes. Ec_MI-02 has genes encoding for rI, rII, and rIII lysis inhibition proteins, which supports the observation of delayed lysis in the one-step growth curve. The current study provides additional evidence that wild birds could also be a good natural reservoir for bacteriophages that do not carry antibiotic resistance genes and could be good candidates for phage therapy. In addition, studying the genetic makeup of bacteriophages that infect human pathogens is crucial for ensuring their safe usage in the food industry.

Foodborne illnesses of Escherichia coli O157origin and its control measures.

Foodborne illnesses are leading source of morbidity and mortality in both developed and developing nations. Escherichia coli O157 is one of the most reported foodborne pathogen that emerged in the past few decades. South East Asia region suffers the highest average burden of diarrhoeal mortality, especially when it comes to child mortality.Query Many studies were undertaken in the developed nations to evaluate the role of E. coli O157 as one of the etiological agent in foodborne outbreaks. In this article, we discuss the distribution of E. coli O157 serotype in the food chains of South East Asian countries, with a special focus on India where more than half a million child diarrhoeal deaths occurs every year and the reasons for which is often not ascertained to the fullest extent. The article also describes in detail about the various detection methods and control measures with respect to E. coli O157. The aim of this study is to document and highlight the extent of Foodborne infections of E. coli O157 origin and thereby taking effective and proactive preventive measures.

Investigation of efficient thermal inactivation parameters of Escherichia coli O157:H7 in meatballs by grilling.

The aim of the study was to investigate the safe cooking parameters to eliminate E.coli O157:H7 in commonly consumed meatball types, by simulating the meatball formula and the cooking practices of restaurants. Ground meat was inoculated around 7 ± 1 log cfu/g with a cocktail of 5 strains of E.coli O157:H7. The meatballs were prepared with different ingredients and seasonings depending on the type (kasap or Inegöl). The cooking experiments were conducted on a grill, at two different temperatures, 170 and 180 °C. Results show that, in order to achieve ≥ 5 log destruction of E.coli O157:H7 in Kasap and Inegöl meatballs cooked at 170 °C, the internal temperature should reach to 85 °C. On the other hand, when the meatballs were grilled at 180 °C, 5 log reductions were achieved by cooking the meatballs to an internal temperature of 80 °C for Kasap meatballs and 85 °C for Inegöl meatballs. Differences in the meatball formulation and shape affected the thermal destruction of E.coli O157:H7. Measuring of the grill temperature and core temperature of meatballs during cooking and reaching the target temperatures for each type of meatball would help prevent Shiga toxin-producing E.coli (STEC) infections in public eating establishments.

Seed inoculation with antagonistic bacteria limits occurrence of E. coli O157:H7gfp + on baby spinach leaves.

BACKROUND: During the last decades, outbreaks of foodborne illnesses have increasingly been linked to fresh and/or minimally processed fruit and vegetables. Enterohemorrhagic Escherichia coli was the causal agent for major outbreaks in Europe with leafy green vegetables and sprouts. To improve food safety, microbial antagonism has received attention during recent years and could be one of the solution to prevent contamination of food borne pathogens on fresh produce. Here we investigate the antagonistic effect of three bacterial strains (Pseudomonas orientalis, P. flavescens and Rhodococcus sp.) isolated from spinach leaves against E. coli O157:H7gfp + under laboratory and greenhouse conditions. RESULTS: Our results shows that significantly less culturable E.coli O157:H7gfp + were retrieved from the spinach canopy subjected to antagonist seed treatment than canopy inoculation. Seeds inoculated with Rhodococcus sp. significantly reduced growth of E. coli O157:H7gfp + compared with the other antagonists. The result from the in vitro study shows a significant reduction of growth of E. coli O157:H7gfp+, but only after 44 h when E. coli O157:H7gfp + was propagated in a mixture of spent media from all three antagonists. CONCLUSIONS: The antagonistic effect on phyllospheric E.coli O157:H7gfp + observed after seed inoculation with Rhodococcus sp. might be an indication of induced resistance mechanism in the crop. In addition, there was a small reduction of culturable E.coli O157:H7gfp + when propagated in spent media from all three antagonists. Nutritional conditions rather than metabolites formed by the three chosen organisms appear to be critical for controlling E. coli O157:H7gfp+.

Effects of temperature, pH and sodium chloride on antimicrobial activity of magnesium oxide nanoparticles against E. coli O157:H7.

AIM: This study was done to determine the effects of temperature, pH and sodium chloride (NaCl) on antimicrobial activity of magnesium oxide (MgO) nanoparticles (NPs) against E. coli O157:H7. METHODS AND RESULTS: Culture conditions were established by varying the pH (5.0, 7.2 and 9.0), NaCl concentration (0.5, 2.0, 3.5 and 5.0%, w/v), and incubation temperatures (4, 12, 22 and 37°C). At each condition, the antimicrobial activities of MgO-NPs (0, 1, 2 and 4 mg/ml) against E. coli O157:H7 were measured. Four-way analysis of variance indicated interactions among all factors had a significant effect (p ≤ 0.05) on the antimicrobial activity of MgO-NPs. The concentration of MgO-NPs necessary to cause a 5-log reduction of E. coli O157:H7 under the most inhibitory conditions (37°C, pH 9.0, and 5.0% NaCl) was 0.50 mg/ml of MgO-NPs. CONCLUSION: The antimicrobial activity of the MgO-NPs increased significantly (p ≤ 0.05) with increased temperature, pH and NaCl concentration in TSB. SIGNIFICANCE AND IMPACT OF THE STUDY: The influence of intrinsic and extrinsic factors on antimicrobial activity of MgO-NPs we found will contribute to the development of microbial decontamination strategies using MgO in the food industry.