Pathogenic Bacterial Contamination Research Articles

CRISPR-Cas12a-based nanoparticle biosensor for detection of pathogenic bacteria in food

Pathogenic bacterial contamination of food is a major challenge in food safety and public health management. To monitor pathogenic bacteria in food, a rapid, sensitive, and specific pathogen detection method is needed. CRISPR-Cas12a has been developed as a sensitive method for detecting pathogenic bacteria, but its output signal is fluorescent, which need equipment to detect. Here, the nanoparticle probe was designed to detect the activity of Cas12a and were able to visualize the assay results by observing the color change by naked eyes. The target sequences of pathogenic bacteria were amplified by recombinase polymerase, then recognized and bound by the crRNA and Cas12a complex. The activated Cas12a cleaved the linker-ssDNA connecting the nanoparticles, causing the nanoparticles to transition from aggregation to dispersion, and the color showed as purple. The sensitivity analysis showed that the limits of detection (LOD) reached 1 × 10°CFU/mL, 1 × 104 CFU/mL, 1 × 102 CFU/mL, 1 × 103 CFU/mL, 1 × 101 CFU/mL for Escherichia coli, Salmonella typhimurium, Vibrio parahaemolyticus, Staphylococcus aureus, and Listeria monocytogenes, which were all specific for five bacteria in the milk samples. Therefore, this method is a dependable, fast, sensitive and specific method, which make the CRIPSR-Cas12a detection method more useful in bacterial pathogenic detection.

CRISPR/Cas12a-Triggered Visible-Light-Driven Photoelectrochemical Assay with Single-Nucleotide Resolution for Drug-Resistant Foodborne Salmonella Detection.

The prevalence of foodborne pathogenic bacteria, especially drug-resistant strains, such as Salmonella enterica, poses serious threats to public health, highlighting the requirement for the development of rapid and precise detection methods. Herein, a CRISPR/Cas12a-triggered visible-light-driven photoelectrochemical (PEC) assay (CasPEC) was developed using a SiO2-quenched BiVO4/MoS2 p/n-type heterojunction as the photoactive material. The CRISPR/Cas12a recognition endowed the CasPEC assay with high specificity capable of resolving single-nucleotide polymorphisms (SNPs) and identifying SNP-involved drug-resistant bacteria. SiO2 was linked to the surface of the BiVO4/MoS2 heterojunction by single-stranded DNA (ssDNA), which would be cleaved by target-activated CRISPR/Cas12a. This cleavage of ssDNA resulted in the detachment of SiO2, thereby achieving a "signal-on" PEC output. Leveraging the multiple-turnover CRISPR cleavage and the outstanding photoactive performance of PEC signaling, the CasPEC assay for S. enterica showed a detection limit of 103 colony-forming units (CFU)/mL and the ability to detect as few as 0.01% drug-resistant strains. The CasPEC assay can accurately sense the S. enterica contamination in complex food matrices, including beef and milk. These findings demonstrated the great potential of the CasPEC assay for detecting pathogenic bacterial contamination in food, particularly concerning food safety related to SNP-involved drug-resistant bacteria.

Chirality differences of three borneols contribute to controlling Escherichia coli biofilm formation by chemotaxis mediating movement

SummaryEscherichia coli (E. coli) biofilm is the major cause of its high lethality in foodborne illness. Controlling E. coli biofilm formation is a critical way to reduce foodborne diseases. Here, chiral borneol isomers (L‐borneol, D‐borneol, and isoborneol) were identified as E. coli chemorepellents, which reduced reversible adhesion at the initial stage of biofilm formation. Borneols directly inhibited biofilm production and their inhibitory capacities were associated with the chiral stereochemical structures (L‐borneol > D‐borneol > isoborneol). A transcriptomic study revealed the inhibitory mechanism of borneols was attributed to the bacterial motility intention and motility energy system. The most effective isomer, L‐borneol, reduced bacterial energy metabolism and increased E. coli chemotaxis motility intention through the up‐regulation of genes associated with flagellar assembly and bacterial chemotaxis pathways. This work demonstrates that borneols are biofilm inhibitors and supports the potential of borneols as a stereochemical antimicrobial strategy to reduce foodborne pathogenic bacterial contamination.

Detecting Bacteria with Ultralow Concentrations by Enzymatic Cascade Reaction-Amplifying Strategy.

Bacteria can cause infectious diseases even at ultralow concentrations (<1 CFU/mL). It is important to rapidly identify bacterial contamination at ultralow concentrations. Herein, FITC-labeled gelatinase-sensitive nanoparticles (GNPs@FITCs) and NFM@GNP@FITCs are designed and fabricated as ultralow concentration bacteria detection platforms based on an enzymatic cascade reaction-amplifying strategy. Bacterial secretions could trigger the dissociation of GNPs@FITCs to release FITC, with gelatinase used as the model secretion. The detectable signal of ultralow concentration bacteria could be amplified effectively by the gelatinase-triggered cascade reaction. Bacterial concentration was evaluated by the change in fluorescence density. The results showed that the GNPs@FITCs and NFM@GNP@FITCs could be used for identifying bacterial contamination qualitatively, even when the bacterial contamination is lower than 1 CFU/mL. Moreover, the method has better timeliness and convenience, when compared with national standards. As solid films, NFM@GNP@FITCs have better long-term storage stability than GNPs@FITCs. The potential applications of GNPs@FITC and NFM@GNP@FITCs were proved by detecting pathogenic bacteria in food. All the results showed that the method has great potential for screening pathogenic bacterial contamination qualitatively.

Bacteriophage-assisted lysis and eluted genomic DNA-based detection of pathogenic bacterial contamination in food

Foodborne diseases represent a significant global health concern, with a substantial number of illnesses and fatalities reported annually owing to the consumption of contaminated food. Current methods for identifying foodborne pathogens cannot effectively distinguish live from dead bacteria or efficiently detect multiple targets. Therefore, we developed a selective detection method for three pathogenic bacteria in food samples that leverages bacteriophage-assisted live-cell lysis and exposed genomic DNA amplification. The antimicrobial activity and host specificity of these three bacteriophages were employed to confirm the target bacteria selectivity. Bacterial DNA purification using bacteriophage-assisted lysis demonstrated the superior activity of the selected phages in extracting DNA from Escherichia coli O157:H7 and Salmonella Typhimurium. The results from reactions involving the three strains, including Bacillus cereus, highlighted that a 1 h incubation period yielded the most efficient DNA extraction and purification. The polymerase chain reaction (PCR) products obtained were comparable in terms of concentration and purity with those generated using bacterial DNA prepared using a commercial kit. In the practical food sample application experiment, bacterial strains were successfully recovered and concentrated using a polyethersulfone filter, resulting in a concentration factor >3 for all samples. Furthermore, the concentration of purified bacterial DNA from contaminated kimchi cabbage exceeded 10 ng/μL. Notably, we could detect E. coli O157:H7, S. Typhimurium, and B. cereus spiked at 103 colony-forming units/mL using multiplex PCR. This innovative bacteriophage-based approach holds substantial promise for the selective and practical detection of live foodborne pathogens, thereby significantly advancing food safety standards.

Survival of enteric microorganisms in microalgal biomass after phycoremediation of swine wastewater

The microalgal biomass obtained from phycoremediation holds great potential for various biotechnological applications. However, it is important to address the issue of potential pathogenic bacterial contamination, which can be present in the wastewater treated during phycoremediation and may coexist with the harvested biomass. This study aimed to investigate the survival of enteric bacteria when present in microalgal biomass stored at temperature ranges that emulate environmental conditions typically found in tropical countries. For that, the biomass was intentionally contaminated with known quantities of Escherichia coli and Salmonella typhimurium. The contaminated biomass was stored at temperatures corresponding to different seasons in tropical countries: 10 °C (winter), 21 °C (spring/autumn), and 35 °C (summer). The results revealed that S. typhimurium was able to survive for 14 days at all tested temperatures. Conversely, E. coli exhibited a reduction of up to 6 log10 in 21 days when stored under spring and summer temperatures. However, when the biomass was stored at the winter temperature, the reduction in E. coli concentration was only 1 log10. The time required for 90% inactivation of S. typhimurium (T90) was determined to be approximately 3.725 days. However, to achieve 90% inactivation of E. coli at 10, 21, and 35 (°C), it took approximately 25.706, 4.217, and 3.906 days, respectively. These findings underscore the critical role of storage temperature in influencing the survival of bacteria over time. It is important to maintain aseptic conditions during the handling and storage of the biomass, particularly considering its intended applications and potential downstream uses.

Nutritional content and microbial contamination of fresh cold and frozen Bali beef in Mambal RPH production in Badung Regency, Bali Province

This study aims to determine the nutrition and microbial contamination of fresh, chilled, and frozen Bali beef. This study used a completely randomized design (CRD) direct pattern a 3x7, with 3 treatments and 7 repetitions of Bali beef. The treatments were: (P1) meat stored at room temperature (27°C-35°C) for less than 1 day (fresh meat), (P2) meat stored at 0°C-4°C for 1 day -2 days (cold meat), (P3) meat stored at a minimum temperature of -18°C with a storage time of 1-7 days (frozen meat). The variables observed in this study were the nutritional content of meat, namely water content, protein, fat, ash and carbohydrates as well as pathogenic bacterial contamination, namely Total Plate Count (TPC), Colliform and E-Colli. The results of this study showed that the nutritional content of water content and ash content in fresh, chilled and frozen meat had no significant effect. However, the protein content decreased significantly when the meat was frozen. The fat and carbohydrate content had the opposite result, namely, there was a significant increase when the meat was frozen. In terms of meat microbiological contamination on TPC, Coliform and E-colli variables, showed that frozen meat had the highest microbial population followed by fresh meat and cold meat had the lowest total pathogenic microbes.

Analysis of Contamination of Total Microbes, Coliform, Escherichia coli, and Staphylococcus aureus in Elementary School Children’s Snacks in Jimbaran area, Bali, Indonesia

School-age children like buying snacks after school. The snacks are sold on the roadside, therefore making them vulnerable to bacterial contamination, such as Coliform, Escherichia coli, and Staphylococcus aureus that cause foodborne diseases. Jimbaran is in South Kuta, Badung, Bali. There are 20 elementary schools in Jimbaran with 7,321 students. The purpose of this research was to determine pathogenic bacterial contamination in snacks. Sampling was done using Simple Random Sampling method, by selecting three types of snacks from five different elementary schools in Jimbaran. Testing pathogenic bacterial contamination using total plate count (TPC), Most Probable Number (MPN), and Staphylococcus aureus test. The results showed the highest average total microbes in cubit cake at Elementary School E is 34.06×104 CFU/g. The highest average of Coliforms in fried tofu at Elementary School B was 92.27×102 MPN/g. The highest average E. coli in omelets roll at Elementary School C was 63.93×102 MPN/g. The highest average S. aureus in cakkue cake at Elementary School D was 92.9×102 CFU/g. The conclusion were 45 samples had total microbial contamination, 22 samples were positive for Coliform, 16 samples were positive for E. coli, and 40 samples were positive for S. aureus. According to Indonesian Food Safety Standards (BPOM RI), 4.4% of the snacks tested were suitable for consumption, while 95.6% were not suitable for consumption.

Recyclable ferroferric oxide@titanium dioxide@molybdenum disulfide with enhanced enzyme-like activity under visible light for effectively inhibiting the growth of drug-resistant bacteria in sewage.

With the development of social industry and the increase in domestic sewage discharge, pathogenic bacterial contamination in water has become a serious health and environmental problem. It is important to design sewage treatment reagents with effective pathogenic bacterial removal and recyclability. In this work, we developed a nanocomposite, Fe3O4@TiO2@MoS2, with once-for-all effects of photocatalytic, magnetic, and peroxidase-like activities for solving the above-mentioned problems. The loading of MoS2 may cause the band gap of Fe3O4@TiO2 to decrease from 3.11 eV to 2.85 eV, demonstrating increased photocatalytic activity under visible light, based on the synergistic impact of Fe3O4@TiO2 and MoS2. In return, the peroxidase-like activity of Fe3O4@TiO2@MoS2 was significantly higher than that of Fe3O4 and MoS2 alone, resulting in the generation of more hydroxyl radicals (˙OH) for combating the drug-resistant broad-spectrum β-lactamase-producing Escherichia coli and methicillin-resistant Staphylococcus aureus. The antibacterial mechanism study showed that Fe3O4@TiO2@MoS2 could effectively inhibit bacterial growth by destroying the bacterial biofilm and genome via the peroxidase-like activity as well as photocatalytic activity. In addition, Fe3O4@TiO2@MoS2 has excellent paramagnetic properties, which can achieve magnetic recovery after wastewater treatment. Even after three times of recycling, its antibacterial effect can remain above 98.8%.

Deteksi Cemaran Bakteri Salmonella spp. pada Ikan Bandeng Segar (Chanos chanos) di Tempat Pelelangan Ikan Gadukan Lumpur Kabupaten Gresik

Salmonella spp. is a bacterium that causes Salmonellosis and is a bacterium that can cause food-borne illness to humans. The presence of Salmonella spp. in fresh milkfish can affect quality aspects, quality deterioration in fishery products, and food safety. Microbiological testing is an important indicator in checking for contamination in food. The main factor causing contamination can be the presence of pathogenic bacterial contamination in food ingredients. The purpose of this study was to detect Salmonella spp. on fresh milkfish (Chanos chanos) sold at Fish Auction Places (FAP), Gresik Regency using the Total Plate Count (TPC) test indicator and Salmonella Shigella Agar (SSA) media culture. This study used a qualitative descriptive study which began with observing the location and taking samples of milkfish in the field, then proceeding with the isolation of Salmonella spp. from in-vitro samples of milkfish and analyzed qualitatively. The results showed that fresh milkfish samples were contaminated with microbes with the highest number of 6×105 CFU/g and were detected to contain Salmonella spp. on SSA media, so that milkfish sold at the Gadukan Lumpur Fish Auction Place in Gresik Regency cannot meet the Indonesian National Standard for fresh fish (2729-2021).

Formation of Predictive-Based Models for Monitoring the Microbiological Quality of Beef Meat Processed for Fast-Food Restaurants.

Consumption of raw or undercooked meat is responsible for 2.3 million foodborne illnesses yearly in Europe alone. The greater part of this illness is associated with beef meat, which is used in many traditional dishes across the world. Beneath the low microbiological quality of beef lies (pathogenic) bacterial contamination during primary production as well as inadequate hygiene operations along the farm-to-fork chain. Therefore, this study seeks to understand the microbiological quality pathway of minced beef processed for fast-food restaurants over three years using an artificial neural network (ANN) system. This simultaneous approach provided adequate precision for the prediction of a microbiological profile of minced beef meat as one of the easily spoiled products with a short shelf life. For the first time, an ANN model was developed to predict the microbiological profile of beef minced meat in fast-food restaurants according to meat and storage temperatures, butcher identification, and working shift. Predictive challenges were identified and included standardized microbiological analyses that are recommended for freshly processed meat. The obtained predictive models (an overall r2 of 0.867 during the training cycle) can serve as a source of data and help for the scientific community and food safety authorities to identify specific monitoring and research needs.

Seasonal Changes in the Microbial Communities on Lettuce (Lactuca sativa L.) in Chungcheong-do, South Korea.

Lettuce is one of the most consumed vegetables worldwide. However, it has potential risks associated with pathogenic bacterial contamination because it is usually consumed raw. In this study, we investigated the changes in the bacterial community on lettuce (Lactuca sativa L.) in Chungcheong-do, South Korea, and the prevalence of foodborne pathogens on lettuce in different seasons using 16S rRNA gene-based sequencing. Our data revealed that the Shannon diversity index showed the same tendency in term of the number of OTUs, with the index being greatest for summer samples in comparison to other seasons. Moreover, the microbial communities were significantly different between the four seasons. The relative abundance of Actinobacteriota varied according to the season. Family Micrococcaceae was most dominant in all samples except summer, and Rhizobiaceae was predominant in the microbiome of the summer sample. At the genus level, the relative abundance of Bacillus was greatest in spring samples, whereas Pseudomonas was greatest in winter samples. Potential pathogens, such as Staphylococcus and Clostridium, were detected with low relative abundance in all lettuce samples. We also performed metagenome shotgun sequencing analysis on the selected summer and winter samples, which were expected to be contaminated with foodborne pathogens, to support 16S rRNA gene-based sequencing dataset. Moreover, we could detect seasonal biomarkers and microbial association networks of microbiota on lettuce samples. Our results suggest that seasonal characteristics of lettuce microbial communities, which include diverse potential pathogens, can be used as basic data for food safety management to predict and prevent future outbreaks.

Molecular Characterization and Antibiogram Profiling of the Isolated Food-Borne Pathogenic Bacteria on Fresh-Cut Salad Vegetables

Fresh cut salad vegetables (FCSV) play a significant role in our healthy and balance diet. The consumption of raw salad vegetables are vectors for the transmission of various infectious diseases, which is a public health issue in developing and developed world. Therefore, the aim of this present study was to evaluate the microbial contamination of ready-to-eat salad vegetables sold in different local vendors in Kushtia and Jhenaidah districts in Bangladesh. A total of 21different ready-to-eat FCSV samples were collected aseptically and analyzed immediately in our laboratory. A total viable bacterial count (TVBC) was enumerated up to 107 CFU/g in the tested samples. The highest number (3.01±1.4 × 107 CFU/g) of TVBC was found in Coriander leaf (Coriandrum sativum) and least microbial load (2.33±1.05 × 105 CFU/g) was observed in Red spinach. On the basis of morphological differentiation randomly selected bacterial isolates (Aeromonas sp., Citrobacter sp., Enterobacter sp., Pectobacterium sp., and Staphylococcus sp.) were identified by 16S rRNA gene sequencing. Moreover, most of the isolates were showed as multidrug-resistant bacteria via the antibiogram profiling testing. The overall antimicrobial susceptibility profile showed that the tested bacterial isolates were resistant against Erythromycin (15μ g), Penicillin G (10 unites), Nalidixic acid (30 μg), Ceftriaxone (30 μg), Ceftazidime (30 μg), susceptible against Kanamycin (30 μg), Polymyxin B (300 units), CO-Trimoxazole (25 μg), Colistin (10 μg), Doxycycline (30 μg) and intermediate against Nalidixic acid (30 μg), CO-Trimoxazole (25 μg), and Kanamycin (30 μg). Pathogenic bacterial contamination of FCSV, hygienic practices should be maintained before consumption. J. of Sci. and Tech. Res. 3(1): 77-84, 2021

A dual-stimuli responsive electrochemiluminescence biosensor for pathogenic bacterial sensing and killing in foods

Pathogenic bacterial contamination of food-associated products threatens food safety. Herein, a dual-stimuli responsive electrochemiluminescence (ECL) sensor was constructed for the determination and sterilization of Staphylococcus aureus (S. aureus). Silver nanoclusters labeled hairpin DNA (H–Ag NCs) acted as the energy acceptor of ECL emission from CdS quantum dots (CdS QDs), generating resonance energy transfer (RET) and quenching ECL signal. After activation of DNA walker by S. aureus and cleavage of nicking endonuclease, Ag NCs were liberated from CdS QDs surface, and then gold nanoparticles (Au NPs) were introduced. ECL signal was enhanced by the energy transfer from ECL-excited surface plasmon resonance (SPR) in Au NPs to CdS QDs. Consequently, the proposed method performed well in S. aureus test with a linear range of 5–108 CFU/mL. This sensing system achieved the high discrimination and killing of S. aureus in foods, illuminating the reliability in practical applications.

Rapid screening of antimicrobial probiotics using CRISPR cascade

Animal bacterial infection is increasingly threatening human health. Here we report a nucleic acid amplification-free CRISPR genetic assay that allows to rapidly screen potential food-origin antimicrobial probiotics. The assay (termed CRISPRzyme assay) is based on a CRISPR-DNAzyme cascade, where the target gene sequentially activated Cas12a protein and DNAzyme, yielding a limit of detection of 62 CFU Vibrio parahaemolyticus, 86 CFU Salmonella Typhimurium, and 82 CFU Listeria monocytogenes. The elimination of nucleic acid amplification shortens processing time and operational complexity. The assay was used to rapidly screen antimicrobial probiotics by end-measurement of fluorescence of pathogenic bacteria. Particularly, it can estimate the in vivo antimicrobial effect due to its capacity for pathogen quantification in complex samples. We found that isolates of Bacillus and lactic acid bacteria separated from fermented food exhibited strong antimicrobial activity for fish pathogen, Vibrio parahaemolyticus, and identified surfactin as the key antimicrobial component. The CRISPRzyme assay could ease antimicrobial probiotics screening, and constitutes a new tool for combatting pathogenic bacterial contamination and infection.

SECONDARY METABOLITE OF SUMBAWA ALGAE AND ITS POTENTIAL AS NATURAL PRESERVATIVE CANDIDATES (AN ANTIMICROBIAL STUDIES)

Pathogenic bacterial contamination was a serious matter due to its capability in reducing food quality and health. This study aimed to select various types of algae in Luk Coast, Sumbawa Regency that have the potential to produce antibacterial compounds for natural food preservatives. Algae on Luk Coast was identified by means of morphological characters, followed by sample preparation and extraction of secondary metabolites (bioactive compounds). Algae extracts were used in antibacterial tests against food spoilage bacteria, such as Escherecia coli, Staphylococcus aureus, Salmonella thypi, Enterobacter cloacae and Pantoea agglomerans. Five types of algae identified were Padina sp., Halimeda opuntia, Sargassum horneri, Sargassum crassifolium and Galaxaura rugose. The five algae have the growth-inhibiting ability toward the tested bacteria. The highest inhibition zone was obtained from the 100% algae extract concentration.

Determination of Factors that Contribute to the Prevalence of Diarrhoea among Children Under Five Years of Age in Association with the Status of Drinking Water Sources at Bububu, Zanzibar

This study aimed to determine the contributing factors for diarrhoea prevalence among children under-five years at Bububu, Zanzibar. The study applied a cross-sectional research design that used quantitative methods. Data were collected from 97 mothers/caregivers of the children. Structured questionnaires were used for assessing socio-economic factors contributing to diarrhoea. Laboratory experiments were carried out to assess the quality of drinking water sources. Most Probable Number (MPN) count per 100 ml was measured from drinking water sources. Multivariate logistic analysis was computed to assess independent factors of childhood diarrhoea. The prevalence of diarrhoea was significantly associated with; the caregiver’s level of education, large family size, nature of toilet used, drinking water storage, drinking water sources, belief that water is safe, household waste disposal, poor storage of baby’s food and washing hands with soap (p &lt; 0.05). Pathogenic bacterial contamination was found to be high in borehole water sources and harvested rainwater compared to piped water sources (p &lt; 0.05). Health education, drinking water treatment, improved sanitation and hygiene could have significant importance in the reduction of diarrhoea prevalence among under-five children in the study area.&#x0D; Keywords: Prevalence of diarrhoea, Social-economic factors, Bacteriological contamination, Drinking water, Under-five children.

Irrigation of Olives with Reclaimed Wastewaters and Deficit Strategies Affect Pathogenic Bacteria Contamination of Water and Soil.

This study aimed to evaluate pathogenic bacterial contamination of the water-soil-plant system in potted olive trees irrigated with reclaimed wastewater. Desalinated water (DW) obtained by treating municipal wastewater (SW) and reclaimed water (RW) obtained by mixing SW with the brine (BR) produced by DESERT technology (tertiary treatment by ultrafiltration, active carbon and reverse osmosis) were used. Two different irrigation regimes were compared: full irrigation (FI) and regulated deficit irrigation (RDI). During two irrigation seasons the concentrations of Escherichia coli, enterococci, spores of sulfite-reducing Clostridia (SRC) and Salmonella spp. were monitored in water, soil and fruit samples. Microbial concentrations in DW were always below the threshold for reuse in agriculture, while RW showed the highest level of contamination for all observed parameters. RDI management appeared to increase the soil content of SRC spores with respect to FI. Sporadically low SRC spore contamination was recorded in some fruits only in 2018, regardless of the irrigation source, probably because of accidental contamination during sampling or post-harvest handling. This study encourages the creation of a better regulatory framework reference, with specific guidelines for the use of RW as part of integrated environmental systems for the management of sustainable agriculture.

Multidrug-resistant enteroaggregative Escherichia coli (EAEC) enters dormant state during heat treatment: A potential hazard in municipal sludge

Reuse of sewage sludge is a general trend and land application is an essential way to reuse sludge. The outbreak of coronavirus disease has raised concerns about human pathogens and their serious threat to public health. The risk of pathogenic bacterial contamination from land application of municipal sludge has not been well assessed. The purpose of this study was to investigate the presence of pathogenic bacteria in municipal sewage sludge and to examine the survival potential of certain multidrug-resistant enteroaggregative Escherichia coli (EAEC) strain isolated from sewage sludge during heat treatment. The sewage sludge produced in the two wastewater treatment plants contained pathogenic bacteria such as pathogenic E. coli, Shigella flexneri, and Citrobacter freundii. The environmental strain of EAEC isolated from the sludge was resistant to eight types of antibiotics. It could also enter the dormant state after 4.5 h of treatment at 55 °C and regrow at 37 °C, while maintaining its antibiotic resistance. Our results indicate that the dormancy of EAEC might be why it is heat-resistant and could not be killed completely during the sludge heat treatment process. Owing to the regrowth of the dormant pathogenic bacteria, it is risky to apply the sludge to land even if the sludge is heat-treated, and there is also a risk of spreading antibiotic resistance.

Microbiota Analysis and Microbiological Hazard Assessment in Chinese Chive (Allium tuberosum Rottler) Depending on Retail Types.

Chinese chive (Allium tuberosum Rottler) has potential risks associated with pathogenic bacterial contamination as it is usually consumed raw. In this study, we investigated the microbiota of Chinese chives purchased from traditional markets and grocery stores in March (Spring) and June (Summer) 2017. Differences in bacterial diversity were observed, and the microbial composition varied across sampling times and sites. In June, potential pathogenic genera, such as Escherichia, Enterobacter, and Pantoea, accounted for a high proportion of the microbiota in samples purchased from the traditional market. A large number of pathogenic bacteria (Acinetobacter lwoffii, Bacillus cereus, Klebsiella pneumoniae, and Serratia marcescens) were detected in the June samples at a relatively high rate. In addition, the influence of the washing treatment on Chinese chive microbiota was analyzed. After storage at 26°C, the washing treatment accelerated the growth of enterohemorrhagic Escherichia coli (EHEC) because it caused dynamic shifts in Chinese chive indigenous microbiota. These results expand our knowledge of the microbiota in Chinese chives and provide data for the prediction and prevention of food-borne illnesses.