Presence and Persistence of Salmonella in Water: The Impact on Microbial Quality of Water and Food Safety

A multicenter genomic epidemiological investigation in Brazil, Chile, and Mexico reveals the diversity and persistence of Salmonella populations in surface waters

This study examined the diversity and persistence of Salmonella in the surface waters of agricultural regions of Brazil, Chile, and Mexico. Research groups (three in 2019-2020 and five in 2021-2022) conducted a long-term survey of surface water across 5-8 months annually (n = 30 monthly). On-site, each team filtered 10-L water samples with modified Moore Swabs to capture Salmonella, which were then isolated and identified using conventional microbiological techniques. Salmonella isolates were sequenced on Illumina platforms. Salmonella was present in 1,493/3,291 water samples (45.8%), with varying isolation rates across countries and years. Newport, Infantis, and Typhimurium were the most frequent among the 128 different serovars. Notably, 22 serovars were found in all three countries, representing almost half of the 1,911 different isolates collected. The resistome comprised 72 antimicrobial resistance (AMR) genes and six point mutations in three genes. At least one AMR determinant was observed in 33.8% (646/1,911) of the isolates, of which 47.4% (306/646) were potentially multidrug resistant. Phylogeny based on core genome multilocus sequence typing (cgMLST) showed that most isolates clustered according to sequence type and country of origin. Only 14 cgMLST multi-country clusters were detected among the 275 clusters. However, further analysis confirmed that close genetic relatedness occurred mostly among isolates from the same country, with three exceptions. Interestingly, isolates closely related phylogenetically were recovered over multiple years within the same country, indicating the persistence of certain Salmonella in those areas. In conclusion, surface waters in these regions are consistently contaminated with diverse Salmonella, including strains that persist over time.IMPORTANCESalmonella is a leading foodborne pathogen responsible for millions of illnesses, hospitalizations, and deaths annually. Although Salmonella-contaminated water has now been recognized as an important contamination source in the agrifood chain, there is a lack of knowledge on the global occurrence and diversity of Salmonella in surface water. Moreover, there has been insufficient research on Salmonella in surface waters from Latin American countries that are major producers and exporters of agricultural products. Incorporating genetic profiling of Salmonella isolates from underrepresented regions, such as Latin America, enhances our understanding of the pathogen's ecology, evolution, antimicrobial resistance, and pathogenicity. Moreover, leveraging genomic data derived from pathogens isolated from diverse geographical areas is critical for assessing the potential public health risk posed by the pathogen and expediting investigations of foodborne outbreaks. Ultimately, global efforts contribute significantly to reducing the incidence of foodborne infections.

Incidence, identification and antibiotic resistance of Salmonella spp. in the well waters of Tadla Plain, Morocco

Concerns about challenges with water availability in the Tadla Plain region of Morocco have grown as a result of groundwater contamination brought on by human activity, climate change, and insufficient groundwater management. The objective of the study is to measure the number of resistant bacteria in the groundwater of Beni Moussa and Beni Aamir, as well as to evaluate the level of water pollution in this area. 200 samples were therefore gathered from 43 wells over the course of four seasonal campaigns in 2017 and 2018. Additionally, the samples were examined to determine whether Salmonella species were present and if they were resistant to the 16 antibiotics that were tested. Salmonella spp. have been identified in 31 isolated strains in total, accounting for 18.02% of all isolated strains. Data on antibiotic resistance show that 58.1% of Salmonella spp. strains are multidrug-resistant (MDR); 38.7% of Salmonella strains are tolerant to at least six antibiotics, 19.4% to at least nine antibiotics, 9.7% to four to seven antibiotics, 6.5% to at least eleven antibiotics, and the remaining 3.2% to up to twelve antibiotics. A considerable level of resistance to cefepime (61.29%), imipenem (54.84%), ceftazidime (45.16%), ofloxacin (70.97%), and ertapenem (74.19%) was found in the data. Consequently, it is important to monitor and regulate the growth of MDR in order to prevent the groundwater's quality from declining.

Characteristics of Nontyphoid Salmonella Isolated from Human, Environmental, Animal, and Food Samples in Burkina Faso: A Systematic Review and Meta-Analysis

Salmonella is one of the world's leading causes of zoonotic and foodborne illnesses. Recently, antimicrobial resistance (AMR) has become one of the most critical challenges to public health and food safety. Herein, we employed a meta-analysis to determine the pooled prevalence and spatiotemporal distribution of serovars and antimicrobial resistance in NTS in Burkina Faso. To find eligible articles, a comprehensive literature search of PubMed, African Journals Online, ScienceDirect, Google Scholar, and the gray literature (university libraries) in Burkina was conducted for the period from 2008 to 2020. Studies meeting the inclusion criteria were selected and assessed for risk of bias. To assess the temporal and spatial relationships between serotypes and resistant strains from humans, animals, food, and the environment, a random-effects statistical model meta-analysis was carried out using the Comprehensive Meta-Analysis Version 3.0 program. The NTS prevalence rates were 4.6% (95% CI: 3-7) and 20.1% (95% CI: 6.6-47.4) in humans and animals, respectively, and 16.8% (95% CI: 10.5-25.8) and 15.6% (95% CI: 8.2-27.5) in food and the environment, respectively. Most NTS serovars were S. Derby, reported both in food and animals, and S. Typhimurium, reported in humans, while S. Croft II, S. Jodpur II, and S. Kentucky were the most prevalent in the environment. NTS isolates were highly resistant to erythromycin, amoxicillin, cefixime, and cephalothin, with a pooled prevalence of multidrug resistance of 29% (95% CI: 14.5-49.5). The results of this review show a high diversity of Salmonella serotypes, as well as high antibiotic resistance in Salmonella isolates from animal, human, food, and environmental samples in Burkina, calling for a consolidated "One Health" approach to better understand the drivers of pathogen emergence, spread, and antimicrobial resistance, as well as the formulation of intervention measures needed to limit the risk associated with the disease.

Diazoxon exposure increases susceptibility to infection by Salmonella Typhimurium

Various exogenous factors, such as microbiological and chemical contamination condition food security. Salmonella Typhimurium (S. Typhimurium) is the cause of salmonellosis. This bacterium utilizes phagocytosis to create bacterial reservoirs. On the other hand, exposure to chemical contaminants, such as pesticides, increases susceptibility to numerous infections. Therefore, this research aims to evaluate the effect of co-exposure to diazoxon and S. Typhimurium on the in vitro infection dynamics. For this purpose, human mononuclear cells were pre-exposed in vitro to diazoxon and then challenged with S. Typhimurium at 1, 8, and 24 h. Bacterial internalization, actin polymerization, and reactive oxygen species (ROS) were analyzed. Obtained data show that mononuclear cells previously exposed to diazoxon exhibit greater internalization of S. Typhimurium. Likewise, greater ROS production and an increase in actin polymerization were observed. Therefore, in the proposed scenario, obtained data suggest that co-exposure to diazoxon and S. Typhimurium increases susceptibility to acquiring an illness.

The escalating threat of human-associated infectious bacteria in surface aquatic resources: Insights into prevalence, antibiotic resistance, survival mechanisms, detection, and prevention strategies

Anthropogenic activities and climate change profoundly impact water quality, leading to a concerning increase in the prevalence and abundance of bacterial pathogens across diverse aquatic environments. This rise has resulted in a growing challenge concerning the safety of water sources, particularly surface waters and marine environments. This comprehensive review delves into the multifaceted challenges presented by bacterial pathogens, emphasizing threads to human health within ground and surface waters, including marine ecosystems. The exploration encompasses the intricate survival mechanisms employed by bacterial pathogens and the proliferation of antimicrobial resistance, largely driven by human-generated antibiotic contamination in aquatic systems. The review further addresses prevalent pathogenic bacteria, elucidating associated risk factors, exploring their eco-physiology, and discussing the production of potent toxins. The spectrum of detection techniques, ranging from conventional to cutting-edge molecular approaches, is thoroughly examined to underscore their significance in identifying and understanding waterborne bacterial pathogens. A critical aspect highlighted in this review is the imperative for real-time monitoring of biomarkers associated with waterborne bacterial pathogens. This monitoring serves as an early warning system, facilitating the swift implementation of action plans to preserve and protect global water resources. In conclusion, this comprehensive review provides fresh insights and perspectives, emphasizing the paramount importance of preserving the quality of aquatic resources to safeguard human health on a global scale.

Prevalence of STEC virulence markers and Salmonella as a function of abiotic factors in agricultural water in the southeastern United States

Fresh produce can be contaminated by enteric pathogens throughout crop production, including through contact with contaminated agricultural water. The most common outbreaks and recalls in fresh produce are due to contamination by Salmonella enterica and Shiga toxin-producing E. coli (STEC). Thus, the objectives of this study were to investigate the prevalence of markers for STEC (wzy, hly, fliC, eaeA, rfbE, stx-I, stx-II) and Salmonella (invA) in surface water sources (n = 8) from produce farms in Southwest Georgia and to determine correlations among the prevalence of virulence markers for STEC, water nutrient profile, and environmental factors. Water samples (500 mL) from eight irrigation ponds were collected from February to December 2021 (n = 88). Polymerase chain reaction (PCR) was used to screen for Salmonella and STEC genes, and Salmonella samples were confirmed by culture-based methods. Positive samples for Salmonella were further serotyped. Particularly, Salmonella was detected in 6/88 (6.81%) water samples from all ponds, and the following 4 serotypes were detected: Saintpaul 3/6 (50%), Montevideo 1/6 (16.66%), Mississippi 1/6 (16.66%), and Bareilly 1/6 (16.66%). Salmonella isolates were only found in the summer months (May-Aug.). The most prevalent STEC genes were hly 77/88 (87.50%) and stx-I 75/88 (85.22%), followed by fliC 54/88 (61.63%), stx-II 41/88 (46.59%), rfbE 31/88 (35.22%), and eaeA 28/88 (31.81%). The wzy gene was not detected in any of the samples. Based on a logistic regression analysis, the odds of codetection for STEC virulence markers (stx-I, stx-II, and eaeA) were negatively correlated with calcium and relative humidity (p < 0.05). A conditional forest analysis was performed to assess predictive performance (AUC = 0.921), and the top predictors included humidity, nitrate, calcium, and solar radiation. Overall, information from this research adds to a growing body of knowledge regarding the risk that surface water sources pose to produce grown in subtropical environmental conditions and emphasizes the importance of understanding the use of abiotic factors as a holistic approach to understanding the microbial quality of water.

Total coliforms, microbial diversity and multiple characteristics of Salmonella in soil-irrigation water-fresh vegetable system in Shaanxi, China

Global occurrences of foodborne disease outbreaks have been documented, involving fresh agricultural produce contaminated by various pathogens. This contamination can occur at any point in the supply chain. However, studies on the prevalence of total coliforms, Salmonella and microbial diversity in vegetable and associated environments are limited. This study aimed to assess 1) the number of total coliforms (n = 299) and diversity of microbial communities (n = 52); 2) the prevalence, antibiotic susceptibility, genomic characteristics, and potential transmission relationships of Salmonella in soil-irrigation water-vegetable system (n = 506). Overall, 84.28 % samples were positive to total coliforms, with most frequently detected in soil (100 %), followed by irrigation water (79.26 %) and vegetables (62.00 %). A seasonal trend in coliform prevalence was observed, with significantly higher levels in summer (P < 0.05). Detection rates of Salmonella in soil, vegetable and irrigation water were 2.21 %, 4.74 % and 9.40 %. Fourteen serotypes and sequence types (STs) were respectively annotated in 56 Salmonella isolates, ST13 S. Agona (30.36 %, 17/56), ST469 S. Rissen (25.00 %, 14/56), and ST36 S. Typhimurium (12.50 %, 7/56) were dominant serotypes and STs. Thirty-one (55.36 %) isolates were multi-drug resistant, and the resistance was most frequently found to ampicillin (55.36 %, 31/56), followed by to sulfamethoxazole (51.79 %, 29/56) and tetracycline (50.00 %, 28/56). The genomic characteristics and antibiotic resistance patterns of Salmonella isolates from soil, vegetables, and irrigation water within a coherent geographical locale exhibited remarkable similarities, indicating Salmonella may be transmitted among these environments or have a common source of contamination. Microbial alpha diversity indices in soil were significantly higher (P < 0.05) than that in vegetable and irrigation water. The microbial phylum in irrigation water covered that in the vegetable, demonstrating a significant overlap in the microbial communities between the vegetables and the irrigation water.

Unveiling the genomic landscape of Salmonella enterica serotypes Typhimurium, Newport, and Infantis in Latin American surface waters: a comparative analysis

Surface waters are considered ecological habitats where Salmonella enterica can persist and disseminate to fresh produce production systems. This study aimed to explore the genomic profiles of S. enterica serotypes Typhimurium, Newport, and Infantis from surface waters in Chile, Mexico, and Brazil collected between 2019 and 2022. We analyzed the whole genomes of 106 S. Typhimurium, 161 S. Newport, and 113 S. Infantis isolates. Our phylogenetic analysis exhibited distinct groupings of isolates by their respective countries except for a notable case involving a Chilean S. Newport isolate closely related to two Mexican isolates, showing 4 and 13 single nucleotide polymorphisms of difference, respectively. The patterns of the most frequently detected antimicrobial resistance genes varied across countries and serotypes. A strong correlation existed between integron carriage and genotypic multidrug resistance (MDR) across serotypes in Chile and Mexico (R > 0.90, P < 0.01), while integron(s) were not detected in any of the Brazilian isolates. By contrast, we did not identify any strong correlation between plasmid carriage and genotypic MDR across diverse countries and serotypes.IMPORTANCEUnveiling the genomic landscape of S. enterica in Latin American surface waters is pivotal for ensuring public health. This investigation sheds light on the intricate genomic diversity of S. enterica in surface waters across Chile, Mexico, and Brazil. Our research also addresses critical knowledge gaps, pioneering a comprehensive understanding of surface waters as a reservoir for multidrug-resistant S. enterica. By integrating our understanding of integron carriage as biomarkers into broader MDR control strategies, we can also work toward targeted interventions that mitigate the emergence and dissemination of MDR in S. enterica in surface waters. Given its potential implications for food safety, this study emphasizes the critical need for informed policies and collaborative initiatives to address the risks associated with S. enterica in surface waters.

Growth assessment of Salmonella enterica multi-serovar populations in poultry rinsates with commonly used enrichment and plating media

Isolation of Salmonella from enrichment cultures of food or environmental samples is a complicated process. Numerous factors including fitness in various selective enrichment media, relative starting concentrations in pre-enrichment, and competition among multi-serovar populations and associated natural microflora, come together to determine which serovars are identified from a given sample. A recently developed approach for assessing the relative abundance (RA) of multi-serovar Salmonella populations (CRISPR-SeroSeq or Deep Serotyping, DST) is providing new insight into how these factors impact the serovars observed, especially when different selective enrichment methods are used to identify Salmonella from a primary enrichment sample. To illustrate this, we examined Salmonella-positive poultry pre-enrichment samples through the selective enrichment process in Tetrathionate (TT) and Rappaport Vassiliadis (RVS) broths and assessed recovery of serovars with each medium. We observed the RA of serovars detected post selective enrichment varied depending on the medium used, initial concentration, and competitive fitness factors, all which could result in minority serovars in pre-enrichment becoming dominant serovars post selective enrichment. The data presented provide a greater understanding of culture biases and lays the groundwork for investigations into robust enrichment and plating media combinations for detecting Salmonella serovars of greater concern for human health.

The optimisation of Salmonella surveillance programmes for pullet and layer farms using local farm density as a risk factor

Human salmonellosis cases are often caused by Salmonella serovars Enteritidis and Typhimurium and associated with the consumption of eggs and egg products. Many countries therefore implemented general surveillance programmes on pullet and layer farms. The identification of risk factors for Salmonella infection may be used to improve the performance of these surveillance programmes. The aims of this study were therefore to determine 1) whether local farm density is a risk factor for the infection of pullet and layer farms by Salmonella Enteritidis and Typhimurium and 2) whether the sampling effort of surveillance programmes can be reduced by accounting for this risk factor, while still providing sufficient control of these serovars. We assessed the importance of local farm density as a risk factor by fitting transmission kernels to Israeli surveillance data during the period from June 2017 to April 2019. The analysis shows that the risk of infection by serovars Enteritidis and Typhimurium significantly increased if infected farms were present within a radius of approximately 4 km and 0.3 km, respectively. We subsequently optimized a surveillance programme that subdivided layer farms into low and high risk groups based on the local farm density with and allowed the sampling frequency to vary between these groups. In this design, the pullet farms were always sampled one week prior to pullet distribution. Our analysis shows that the risk-based surveillance programme is able to keep the between-farm R0 of serovars Enteritidis and Typhimurium below 1 for all pullet and layer farms, while reducing the sampling effort by 32% compared to the currently implemented surveillance programme in Israel. The results of our study therefore indicate that local farm density is an important risk factor for infection of pullet and layer farms by Salmonella Enteritidis and Typhimurium and can be used to improve the performance of surveillance programmes.

Point-of-Care Diagnostic System for Viable Salmonella Species via Improved Propidium Monoazide and Recombinase Polymerase Amplification Based Nucleic Acid Lateral Flow

Salmonella species are prominent foodborne microbial pathogens transmitted through contaminated food or water and pose a significant threat to human health. Accurate and rapid point-of-care (POC) diagnosis is gaining attention in effectively preventing outbreaks of foodborne disease. However, the presence of dead bacteria can interfere with an accurate diagnosis, necessitating the development of methods for the rapid, simple, and efficient detection of viable bacteria only. Herein, we used an improved propidium monoazide (PMAxx) to develop a nucleic acid lateral flow (NALF) assay based on recombinase polymerase amplification (RPA) to differentiate viable Salmonella Typhimurium. We selected an RPA primer set targeting the invA gene and designed a probe for NALF. RPA-based NALF was optimized for temperature (30-43 °C), time (1-25 min), and endonuclease IV concentration (0.025-0.15 unit/µL). PMAxx successfully eliminated false-positive results from dead S. Typhimurium, enabling the accurate detection of viable S. Typhimurium with a detection limit of 1.11 × 102 CFU/mL in pure culture. The developed method was evaluated with spiked raw chicken breast and milk with analysis completed within 25 min at 39 °C. This study has potential as a tool for the POC diagnostics of viable foodborne pathogens with high specificity, sensitivity, rapidity, and cost-effectiveness.

Microbiological hazard identification in river waters used for recreational activities

Pathogenic bacteria, viruses, and parasites can cause waterborne disease outbreaks. The study of coastal water quality contributes to identifying potential risks to human health and to improving water management practices. The Río de la Plata River, a wide estuary in South America, is used for recreational activities, as a water source for consumption and as a site for sewage discharges. In the present study, as the first step of a quantitative microbial risk assessment of the coastal water quality of this river, a descriptive study was performed to identify the microbial pathogens prevalent in its waters and in the sewage discharged into the river. Two sites, representing two different potential risk scenarios, were chosen: a heavily polluted beach and an apparently safe beach. Conductivity and fecal contamination indicators including enterococci, Escherichia coli, F + RNA bacteriophages, and human polyomaviruses showed high levels. Regarding enterococci, differences between sites were significant (p-values <0.001). 93.3% and 56.5% of the apparently safe beach exceeded the recreational water limits for E. coli and enterococci. Regarding pathogens, diarrheagenic E. coli, Salmonella, and noroviruses were detected with different frequencies between sites. The parasites Cryptosporidium spp. and Giardia duodenalis were frequently detected in both sites. The results regarding viral, bacterial, and parasitic pathogens, even without correlation with conventional indicators, showed the importance of monitoring a variety of microorganisms to determine water quality more reliably and accurately, and to facilitate further studies of health risk assessment. The taxonomic description of microbial pathogens in river waters allow identifying the microorganisms that infect the population living on its shores but also pathogens not previously reported by the clinical surveillance system.

Iron/Copper/Phosphate nanocomposite as antimicrobial, antisnail, and wheat growth-promoting agent

BACKGROUND

One of the current challenges is to secure wheat crop production to meet the increasing global food demand and to face the increase in its purchasing power. Therefore, the current study aimed to exploit a new synthesized nanocomposite to enhance wheat growth under both normal and drought regime. The effectiveness of this nanocomposite in improving the microbiological quality of irrigation water and inhibiting the snail's growth was also assessed.

RESULTS

Upon the employed one-step synthesis process, a spherical Fe/Cu/P nanocomposite was obtained with a mean particle size of 4.35 ± 1.524 nm. Cu2+, Fe2+, and P4+ were detected in the dried nanocomposite at 14.533 ± 0.176, 5.200 ± 0.208, and 34.167 ± 0.203 mg/ml concentration, respectively. This nanocomposite was found to exert antibacterial activity against Escherichia coli and Salmonella typhi. It caused good inhibition percent against Fusarium oxysporum (43.5 ± 1.47%) and reduced both its germination rate and germination efficiency. The lethal concentration 50 (LC50) of this nanocomposite against Lanistes carinatus snails was 76 ppm. The treated snails showed disturbance in their feeding habit and reached the prevention state. Significant histological changes were observed in snail digestive tract and male and female gonads. Drought stress on wheat's growth was mitigated in response to 100 and 300 ppm treatments. An increase in all assessed growth parameters was reported, mainly in the case of 100 ppm treatment under both standard and drought regimes. Compared to control plants, this stimulative effect was accompanied by a 2.12-fold rise in mitotic index and a 3.2-fold increase in total chromosomal abnormalities.

CONCLUSION

The finding of the current study could be employed to mitigate the effect of drought stress on wheat growth and to enhance the microbiological quality of irrigation water. This is due to the increased efficacy of the newly synthesized Fe/Cu/P nanocomposite against bacteria, fungi, and snails. This methodology exhibits potential for promoting sustainable wheat growth and water resource conservation.

Contribution of rooftop rainwater harvesting to climate adaptation in the city of Hannover: Water quality and health issues of rainwater storage in cisterns and ponds

Rooftop rainwater harvesting systems and blue-green infrastructure are becoming important resilience alternatives for urban climate adaptation. This study sheds light on the largely unreported physicochemical and microbiological quality of private roof-harvested rainwater (RHRW). We aimed to identify the physicochemical and microbiological characteristics of RHRW, explore potential correlations between them and assess probable health risks associated with recreational interactions of children with the water. RHRW was collected from cisterns and ponds located in an inner courtyard in Hanover, Germany. Physicochemical parameters were measured on site and samples were collected once a month in two campaigns in 2020 and 2021. Escherichia coli concentrations ranged from 1 × 10° to 24.1 × 102 MPN/100 mL, Enterococci from 1 × 10° to 19.7 × 102 MPN/100 mL, Salmonella from 1 × 102 to 39 × 103 CFU/100 mL and Pseudomonas aeruginosa from 1 × 10° to 3 × 103 MPN/100 mL. Correlation analysis indicated potential relationships between bacteria, oxygen, and water temperature. The results of the health risk assessment indicated a potential risk of gastrointestinal illnesses due to exposure to Enterococci and Salmonella spp. present in the cisterns and ponds, highlighting the need for appropriate regulations and guidelines for RHRW aimed for non-potable uses. Blue-green infrastructure, when effectively managed and maintained, can offer benefits both by enhancing urban climate resilience and promoting citizens well-being.

A flow cytometric assay to detect viability and persistence of Salmonella enterica subsp. enterica serotypes in nuclease-free water at 4 and 25°C

Salmonella spp. is one of the most isolated microorganisms reported to be responsible for human foodborne diseases and death. Water constitutes a major reservoir where the Salmonella spp. can persist and go undetected when present in low numbers. In this study, we assessed the viability of 12 serotypes of Salmonella enterica subsp. enterica for 160 days in nuclease-free water at 4 and 25°C using flow cytometry and Tryptic Soy Agar (TSA) plate counts. The results show that all 12 serotypes remain viable after 160 days in distilled water using flow cytometry, whereas traditional plate counts failed to detect ten serotypes incubated at 25°C. Moreover, the findings demonstrate that 4°C constitutes a more favorable environment where Salmonella can remain viable for prolonged periods without nutrients. Under such conditions, however, Salmonella exhibits a higher susceptibility to all tested antibiotics and benzalkonium chloride (BZK). The pre-enrichment with Universal Pre-enrichment Broth (UP) and 1/10 × Tryptic Soy broth (1/10 × TSB) resuscitated all tested serotypes on TSA plates, nevertheless cell size decreased after 160 days. Furthermore, phenotype microarray (PM) analysis of S. Inverness and S. Enteritidis combined with principal component analysis (PCA) revealed an inter-individual variability in serotypes with their phenotype characteristics, and the impact of long-term storage at 4 and 25°C for 160 days in nuclease-free water. This study provides an insight to Salmonella spp. long-term survivability at different temperatures and highlights the need for powerful tools to detect this microorganism to reduce the risk of disease transmission of foodborne pathogens via nuclease-free water.

A Community Waterborne Salmonella Bovismorbificans Outbreak in Greece

BACKGROUND

In August 2022, the Hellenic National Public Health Organisation was notified about a gastroenteritis outbreak in town A in Southern Greece. Investigations aimed to identify the source and implement control measures.

METHODS

Case definition categories were used in a 1:3 case-control study. Cases and controls were interviewed about various exposures. Cases' stool samples were cultured on agar plates and characterised by serotyping, antimicrobial susceptibility testing and Pulse Field Gel Electrophoresis (PFGE). Environmental investigations included tap water sampling for microbiological and chemical analysis in town A and inspection of the water supply system.

RESULTS

We identified 33 cases (median age: 17 years). Tap water consumption was the only significant risk factor for gastroenteritis (OR = 5.46, 95% CI = 1.02-53.95). Salmonella (S.) Bovismorbificans isolated from eight stool and one tap water samples had identical PFGE profiles. No resistant isolates were identified. Residual chlorine levels were lower than the acceptable limits before and during the outbreak. We advised consumption of bottled water and adherence to strict hand hygiene rules until tap water was declared suitable for drinking.

CONCLUSIONS

Epidemiological and molecular data revealed a waterborne S. Bovismorbificans outbreak in town A. We recommend local water safety authorities to ensure that residual chlorine levels comply with the legislation towards water safety planning, to mitigate risks.

Salmonellosis: An Overview of Epidemiology, Pathogenesis, and Innovative Approaches to Mitigate the Antimicrobial Resistant Infections

Salmonella is a major foodborne pathogen and a leading cause of gastroenteritis in humans and animals. Salmonella is highly pathogenic and encompasses more than 2600 characterized serovars. The transmission of Salmonella to humans occurs through the farm-to-fork continuum and is commonly linked to the consumption of animal-derived food products. Among these sources, poultry and poultry products are primary contributors, followed by beef, pork, fish, and non-animal-derived food such as fruits and vegetables. While antibiotics constitute the primary treatment for salmonellosis, the emergence of antibiotic resistance and the rise of multidrug-resistant (MDR) Salmonella strains have highlighted the urgency of developing antibiotic alternatives. Effective infection management necessitates a comprehensive understanding of the pathogen's epidemiology and transmission dynamics. Therefore, this comprehensive review focuses on the epidemiology, sources of infection, risk factors, transmission dynamics, and the host range of Salmonella serotypes. This review also investigates the disease characteristics observed in both humans and animals, antibiotic resistance, pathogenesis, and potential strategies for treatment and control of salmonellosis, emphasizing the most recent antibiotic-alternative approaches for infection control.

Scale and detection method impacted Salmonella prevalence and diversity in ponds

Site-specific approaches for managing food safety hazards in agricultural water require an understanding of foodborne pathogen ecology. This study identified factors associated with Salmonella contamination in Virginia ponds. Grab samples (250 mL, N = 600) were collected from 30 sites across nine ponds. Culture- and culture-independent (CIDT)-based methods were used to detect Salmonella in each sample. Salmonella isolated by culture-based methods were serotyped by Kauffman-White classification. Environmental data were collected for each sample. McNemar's χ2 was used to determine if Salmonella detection differed by testing method. Separate mixed effect models were used to identify environmental factors associated with culture and CIDT-based Salmonella detection. Separate models were built for each pond, and for all ponds combined. Salmonella detection differed significantly (p < 0.001) between CIDT (31 %; 183/600)- and culture (13 %; 77/600)-based methods. Culture-based methods yielded 11 different serovars. All cultured Salmonella samples were confirmed by CIDT; 42.1 % of CIDT Salmonella-positive samples could be cultured. Associations between environmental factors and Salmonella detection also varied substantially by pond and detection method. In the all-pond model, associations were observed for five factors (total coliforms, Escherichia coli, air temperature, UV, rain) for both culture- and CIDT-based Salmonella detection. Rain prior to sampling (24 h) increased odds of Salmonella detection for culture (OR = 5.09) and CIDT (OR = 3.62) in the all-pond model. When all the pond data were used, models masked associations at the individual pond level, as there were noticeable differences between ponds and the odds of isolating Salmonella by environmental factors. Ponds were within a 187-ha area in this study, emphasizing water management needs to be individualized (i.e., assess hazards/risks by pond). Results also highlight detection methods and scale strongly affect observed water quality and should be considered when developing monitoring programs to develop guidance for growers.

Sensitivity of Salmonella Typhimurium to nisin in vitro and in orange juice under refrigeration

The influence of environmental factors on Salmonella sensitivity to nisin in vitro and in refrigerated orange juice were investigated. Nisin activity was observed in the different conditions, but the highest efficiency was achieved at lower pH (4.0) and with higher bacteriocin concentration (174 µM). Moreover, the bactericidal action was directly proportional to the incubation period. When tested in orange juice, nisin caused a reduction of up to 4.05 logarithm cycles in the Salmonella population. So, environmental factors such as low pH and low temperature favored the sensitization of Salmonella cells to the bactericidal action of nisin. Therefore, this may represent an alternative to control Salmonella in refrigerated foods.

Occurrence, Antimicrobial Resistance, and Virulence Profiles of Salmonella Serovars Isolated from Wild Reptiles in South Africa

Reptiles are carriers of an array of microorganisms, including significant zoonotic bacteria of the genus Salmonella, which cause a disease referred to as salmonellosis that affects both animals and humans. This study investigated the occurrence of Salmonella serovars in wild reptiles at Timbavati Private Game Reserve in Limpopo Province, South Africa, and examined their virulence and antimicrobial resistance gene profiles. A total of 19 wild reptiles were sampled, which resulted in 30 presumptive Salmonella isolates. The isolates were identified using polymerase chain reaction (PCR) by amplifying the invA gene and were further confirmed by 16S rRNA gene sequencing. Salmonella serovars were detected in chameleons (36.8%), lizards (31.6%), snakes (15.8%), and tortoises (15.8%). The use of 16S rRNA gene sequencing revealed that Salmonella enterica subsp. enterica serovar Salamae (30%), S. enterica subsp. enterica (16.7%), S. enterica subsp. enterica serovar Typhimurium (13.3%), and S. enterica subsp. enterica serovar Indiana (13.3%) were the four most common subspecies among the investigated 30 isolates. Detected virulence genes included pagN (100%), hilA (96.7%), ssrB (96.7%), prgH (86.7%), and marT (86.7%). The isolates exhibited resistance to nalidixic acid (43.3%) and kanamycin (43.3%), followed by streptomycin (16.7%) and ciprofloxacin (3.3%). Antibiotic-resistant genes were detected as follows: strA, strB, qnrA, qnrS, parC, aadA, aac(6')-Ib, and aac(6')-Ib-cr at 33.3%, 6.7%, 16.7, 13.3%, 10%, 23.3%, 6.7%, and 10%, respectively. The findings highlight the necessity of educational initiatives aimed at reducing reptile-related infections. Effective antibiotic treatment appears promising for infection, given the minimal drug resistance observed in reptile Salmonella serovars in the current study.

Serotype Distribution, Antimicrobial Resistance, Virulence Genes, and Genetic Diversity of Salmonella spp. Isolated from small-scale Leafy Green Vegetable Supply Chains in South Africa

Salmonella have been implicated in foodborne disease outbreaks globally and is a pressing concern in the South African small-scale sector due to inadequate hygiene standards and limited regulatory oversight, leading to a higher risk of foodborne diseases. By investigating irrigation water and leafy green vegetables produced by small-scale growers and sold through unregulated supply chains, this study was able to determine the presence, serotype distribution, virulence gene profiles, antibiotic resistance, and genetic diversity of Salmonella isolated from these sources. From 426 samples, 21 Salmonella-positive samples were identified, providing 53 Salmonella isolates. Of these, six different Salmonella serotypes and sequence types (STs) were identified, including Salmonella II 42:r: ST1208 (33.96%; n = 18), Salmonella Enteritidis: ST11 (22.64%; n = 12), Salmonella II 42:z29: ST4395 (16.98%; n = 9), Salmonella Havana: ST1524 (15.09%; n = 8), Salmonella Typhimurium: ST19 (9.43%; n = 5), and Salmonella IIIb 47:i:z: ST7890 (1.89%; n = 1). A total of 92.45% of the isolates were found to be multidrug-resistant, showing high rates of resistance to aztreonam (88.68%; n = 47), ceftazidime (86.79%; n = 46), nalidixic acid (77.36%; n = 41), cefotaxime (75.47%; n = 40), cefepime (71.70%; n = 38), and streptomycin (69.81%; n = 37). All isolates possessed the aac(6')-Iaa antimicrobial resistance gene, with a range of between 9 and 256 virulence genes. Eleven cluster patterns were observed from Enterobacterial Repetitive Intergenic Consensus sequence analyses, demonstrating high diversity among the Salmonella spp., with water and fresh produce isolates clustering, suggesting water as a potential contamination source. Plasmid replicon types were identified in 41.51% (n = 22) of the isolates, including Col(pHAD28) in Salmonella Havana (5.66%; n = 3), Col156 in Salmonella II 42:z29:- (1.89%; n = 1) and both IncFIB(S) and IncFII(S) in Salmonella Enteritidis (22.64; n = 12), Salmonella Typhimurium (9.43%; n = 5), and Salmonella Havana (1.89%; n = 1). This study highlights the presence of multidrug-resistant and multivirulent Salmonella spp. in the small-scale leafy green vegetable supply chains, underscoring the need for the development of a "fit-for-purpose" food safety management system within this system.

One Health Perspectives on Food Safety in Minimally Processed Vegetables and Fruits: From Farm to Fork

While food markets and food production chains are experiencing exponential growth, global attention to food safety is steadily increasing. This is particularly crucial for ready-to-eat products such as fresh-cut salads and fruits, as these items are consumed raw without prior heat treatment, making the presence of pathogenic microorganisms quite frequent. Moreover, many studies on foodborne illnesses associated with these foods often overlook the transmission links from the initial contamination source. The prevention and control of the dissemination of foodborne pathogens should be approached holistically, involving agricultural production, processing, transport, food production, and extending to final consumption, all while adopting a One Health perspective. In this context, our objective is to compile available information on the challenges related to microbiological contamination in minimally handled fruits and vegetables. This includes major reported outbreaks, specific bacterial strains, and associated statistics throughout the production chain. We address the sources of contamination at each stage, along with issues related to food manipulation and disinfection. Additionally, we provide potential solutions to promote a healthier approach to fresh-cut fruits and vegetables. This information will be valuable for both researchers and food producers, particularly those focused on ensuring food safety and quality.

Assessment of Biofilm Growth on Microplastics in Freshwaters Using a Passive Flow-Through System

Biofilms that colonize on the surface of microplastics (MPs) in freshwaters may pose a potential health risk. This study examined factors that influence MP-associated biofilm growth, including polymer type, degree of weathering, and source water quality. Weathered MPs produced in-lab were employed in biofilm trials conducted on site using a passive flow-through system with raw water at drinking water treatment facility intakes. Adenosine triphosphate (ATP) was used to quantify biofilm abundance; biofilm composition was assessed via metagenomic sequencing. Biofilm growth was observed on all polymer types examined and most prevalent on polyvinyl chloride (PVC), where ATP levels were 6 to 12 times higher when compared to other polymers. Pathogen-containing species including Salmonella enterica and Escherichia coli were present on all polymers with relative abundance up to 13.7%. S. enterica was selectively enriched on weathered MPs in specific water matrices. These findings support the need to research the potential accumulation of pathogenic organisms on microplastic surfaces.

Occurrence and distribution of Salmonella serovars associated with human infection isolated from irrigation waters and food-producing animals in southern Italy: eleven-year monitoring (2011-2021)

Salmonella is one of the main zoonotic agents causing foodborne diseases in Europe. The main reservoirs of the infection are represented by domestic and wild animals, and the infection occurs by direct contact or following the consumption of contaminated food or water. The study aimed to evaluate the presence of Salmonella spp. in food-producing animals and irrigation waters in southern Italy and the serovar distribution. From 2011 to 2021, a total of 473 samples from 6 different animal species (bovine, buffalo, goat, ovine, swine, poultry, and wild boars) and 313 irrigation water samples were collected and analyzed. The overall percentage of positive samples was 56.87% in organs, 50.85% in feces, and 20.45% in irrigation waters. By animal species, the most frequently detected serovar was Salmonella Typhimurium in bovine (17.39%), in buffalo (13.10%) and swine (28.21%), and S. Kentucky (24.78%) in poultry. The subspecies diarizonaeIIIb was frequently detected in goats (40.00%) and ovine (83.33%), while salamaeII (14.12%) and diarizonaeIIIb (11.76%) were frequently isolated in wild boars. In the irrigation water samples, the most frequently detected serovar was S. Napoli (25%). Results revealed that, although in Europe, control strategies aimed at preventing the spread of Salmonella have been implemented, the prevalence of this pathogen in food-producing animals and irrigation waters is high. Considering the risk to public health associated with the contamination of products or foods, more stringent control interventions are needed at primary production and along the food chain.

Microbial hitchhikers harbouring antimicrobial-resistance genes in the riverine plastisphere

BACKGROUND

The widespread nature of plastic pollution has given rise to wide scientific and social concern regarding the capacity of these materials to serve as vectors for pathogenic bacteria and reservoirs for Antimicrobial Resistance Genes (ARG). In- and ex-situ incubations were used to characterise the riverine plastisphere taxonomically and functionally in order to determine whether antibiotics within the water influenced the ARG profiles in these microbiomes and how these compared to those on natural surfaces such as wood and their planktonic counterparts.

RESULTS

We show that plastics support a taxonomically distinct microbiome containing potential pathogens and ARGs. While the plastisphere was similar to those biofilms that grew on wood, they were distinct from the surrounding water microbiome. Hence, whilst potential opportunistic pathogens (i.e. Pseudomonas aeruginosa, Acinetobacter and Aeromonas) and ARG subtypes (i.e. those that confer resistance to macrolides/lincosamides, rifamycin, sulfonamides, disinfecting agents and glycopeptides) were predominant in all surface-related microbiomes, especially on weathered plastics, a completely different set of potential pathogens (i.e. Escherichia, Salmonella, Klebsiella and Streptococcus) and ARGs (i.e. aminoglycosides, tetracycline, aminocoumarin, fluoroquinolones, nitroimidazole, oxazolidinone and fosfomycin) dominated in the planktonic compartment. Our genome-centric analysis allowed the assembly of 215 Metagenome Assembled Genomes (MAGs), linking ARGs and other virulence-related genes to their host. Interestingly, a MAG belonging to Escherichia -that clearly predominated in water- harboured more ARGs and virulence factors than any other MAG, emphasising the potential virulent nature of these pathogenic-related groups. Finally, ex-situ incubations using environmentally-relevant concentrations of antibiotics increased the prevalence of their corresponding ARGs, but different riverine compartments -including plastispheres- were affected differently by each antibiotic.

CONCLUSIONS

Our results provide insights into the capacity of the riverine plastisphere to harbour a distinct set of potentially pathogenic bacteria and function as a reservoir of ARGs. The environmental impact that plastics pose if they act as a reservoir for either pathogenic bacteria or ARGs is aggravated by the persistence of plastics in the environment due to their recalcitrance and buoyancy. Nevertheless, the high similarities with microbiomes growing on natural co-occurring materials and even more worrisome microbiome observed in the surrounding water highlights the urgent need to integrate the analysis of all environmental compartments when assessing risks and exposure to pathogens and ARGs in anthropogenically-impacted ecosystems. Video Abstract.

Persistence of Salmonella enterica subsp. enterica ser. Javiana, Listeria monocytogenes, and Listeria innocua in Hydroponic Nutrient Solution

This study aimed to determine the persistence of Salmonella Javiana, Listeria monocytogenes, and Listeria innocua in nonsterile, hydroponic nutrient solution (NS) at 15, 25, 30, and 37°C over a 21-day period to mimic time from seedling to mature lettuce. Bacteria were inoculated in modified Hoagland's NS at 106 CFU/mL and maintained at 15, 25, 30, and 37°C. Samples were collected at various time points, and bacteria were quantified. A mixed model was used to determine the effect of bacteria type, time (day), and temperature on bacteria concentration (log CFU/mL). The least-squares means were calculated to compare the mean log CFU/mL, and the mean values were compared with Tukey-Kramer honest significant difference test with a significance level of P = 0.05. Statistical analysis indicated that a 3-way interaction effect between temperature, time, and bacteria type had a significant impact on bacterial persistence in NS (P < 0.0001). At all temperatures, S. Javiana persisted in NS throughout the 21-day study period, compared to L. innocua and L. monocytogenes where persistence was limited to between 1 and 14 days. Similarly, decimal reduction values (D-values) of S. Javiana indicated longer persistence in NS than L. innocua and L. monocytogenes at most temperatures. For instance, at 15°C and 25°C, D-values for S. Javiana were estimated at 82 and 26 d, respectively, compared to D-values of 3.6 and ∼3 d for L. monocytogenes. Data indicate that the temperature of NS has a differential effect on the persistence of S. Javiana and Listeria spp. This study furthers the understanding of potential food safety risks associated with hydroponic systems and will contribute to the refinement of further studies to aid in the development of operation-specific risk profiles.

Prevention and Control of Human Salmonella enterica Infections: An Implication in Food Safety

Salmonella is a foodborne zoonotic pathogen causing diarrhoeal disease to humans after consuming contaminated water, animal, and plant products. The bacterium is the third leading cause of human death among diarrhoeal diseases worldwide. Therefore, human salmonellosis is of public health concern demanding integrated interventions against the causative agent, Salmonella enterica. The prevention of salmonellosis in humans is intricate due to several factors, including an immune-stable individual infected with S. enterica continuing to shed live bacteria without showing any clinical signs. Similarly, the asymptomatic Salmonella animals are the source of salmonellosis in humans after consuming contaminated food products. Furthermore, the contaminated products of plant and animal origin are a menace in food industries due to Salmonella biofilms, which enhance colonization, persistence, and survival of bacteria on equipment. The contaminated food products resulting from bacteria on equipment offset the economic competition of food industries and partner institutions in international business. The most worldwide prevalent broad-range Salmonella serovars affecting humans are Salmonella Typhimurium and Salmonella Enteritidis, and poultry products, among others, are the primary source of infection. The broader range of Salmonella serovars creates concern over multiple strategies for preventing and controlling Salmonella contamination in foods to enhance food safety for humans. Among the strategies for preventing and controlling Salmonella spread in animal and plant products include biosecurity measures, isolation and quarantine, epidemiological surveillance, farming systems, herbs and spices, and vaccination. Other measures are the application of phages, probiotics, prebiotics, and nanoparticles reduced and capped with antimicrobial agents. Therefore, Salmonella-free products, such as beef, pork, poultry meat, eggs, milk, and plant foods, such as vegetables and fruits, will prevent humans from Salmonella infection. This review explains Salmonella infection in humans caused by consuming contaminated foods and the interventions against Salmonella contamination in foods to enhance food safety and quality for humans.

Microwave disinfection strengthened by a biochar-based microwave absorbing material for sewage resource utilization

Proper disinfection treatment is the basic guarantee for safe utilisation of sewage. However, the commonly used disinfection methods are not suitable for nutrients containing reclaimed water. In this work, the microwave disinfection method assisted by a microwave-absorbing material in recycled water samples was investigated. Magnetic corn stalk biochar (MCSB), the microwave absorbing material, was prepared by high temperature carbonisation of corn stalk particles impregnated with ferrous sulfate. Escherichia coli and fecal coliforms were selected as target microorganisms to investigate the disinfection efficiency of MCSB assisted microwave radiation (MW/MCSB). The addition of microwave absorbing materials significantly improves the disinfection effect of water samples. Compared with the microwave radiation (MW) without MCSB, the bactericidal rate by using 107 CFU/L E. coli suspension increased from 63.5% to 100% at 480 W for 30 s after adding 4 g/L MCSB. Besides, the effects of MCSB dosage, microwave power, microwave radiation time, and initial bacterial concentration on disinfection efficiency were explored. Moreover, the bactericidal efficiency for actual sewage samples was also demonstrated by treating the effluent from septic tank sewage. The residual fecal coliforms in treated water samples met China's farmland irrigation water standard (GB 5084-2021). The result indicates that the proposed method of microwave disinfection strengthened by MCSB has a promising application prospect for reclaimed water disinfection.

Salmonella Reading: A rare case of generalized salmonellosis in non-endemic region

Salmonella Reading is a rare serotype of Salmonella enterica and is associated with sporadic cases and rare outbreaks worldwide. This article describes a rare case of generalized S. Reading infection imported from Indonesia to Moscow, Russia. A 37-year-old man was admitted to the hospital with fever, weakness, and headache after returning from Indonesia. During his stay in Indonesia, he developed symptoms of a gastrointestinal infection, which resolved there. However, upon return to Moscow, his condition worsened due to high fever, and he was diagnosed with a generalized salmonellosis caused by S. Reading (positive blood and stool culture). This case highlights the importance of differential diagnosis in patients with fever. The health risks associated with traveling to exotic countries and the importance of preventive measures are emphasized. This is the first published case of S. Reading in Eastern Europe.

Comparison of Phenotype Nutritional Profiles and Phosphate Metabolism Genes in Four Serovars of Salmonella enterica from Water Sources

The surveillance of foods for Salmonella is hindered by bias in common enrichment media where serovars implicated in human illness are outgrown by less virulent serovars. We examined four Salmonella serovars, two common in human illness (Enteritidis and Typhimurium) and two that often dominate enrichments (Give and Kentucky), for factors that might influence culture bias. The four serovars had similar growth kinetics in Tryptic Soy Broth and Buffered Peptone Water. Phenotype microarray analysis with 950 chemical substrates to assess nutrient utilization and stress resistance revealed phenotype differences between serovars. Strains of S. Enteritidis had better utilization of plant-derived sugars such as xylose, mannitol, rhamnose, and fructose, while S. Typhimurium strains were able to metabolize tagatose. Strains of S. Kentucky used more compounds as phosphorus sources and grew better with inorganic phosphate as the sole phosphorus source. The sequences of nine genes involved in phosphate metabolism were compared, and there were differences between serovars in the catalytic ATP-binding domain of the histidine kinase phoR. Analysis of the predicted PhoR amino acid sequences from additional Salmonella genomes indicated a conservation of sequences each within the Typhimurium, Give, and Enteritidis serovars. However, three different PhoR versions were observed in S. Kentucky.

Quantum dot-labeled phage-encoded RBP 55 as a fluorescent nanoprobe for sensitive and specific detection of Salmonella in food matrices

As a commonly pathogenic bacterium, the rapid detection of Salmonella outbreaks and assurance of food safety require a highly efficient detection method. Herein, a novel approach to Salmonella detection using quantum dot-labeled phage-encoded RBP 55 as a fluorescent nanoprobe is reported. RBP 55, a novel phage receptor binding protein (RBP), was identified and characterized from phage STP55. RBP 55 was functionalized onto quantum dots (QDs) to form fluorescent nanoprobes. The assay was based on the combination of immunomagnetic separation and RBP 55-QDs, which formed a sandwich composite structure. The results showed a good linear correlation between the fluorescence values and the concentration of Salmonella (10¹-10⁷ CFU/mL) with a low detection limit of 2 CFU/mL within 2 h. The method was used to successfully detect Salmonella in spiked food samples. This approach can be used for the simultaneous detection of multiple pathogens by labeling different phage-encoded RBPs using polychromatic QDs in the future.

Enterocin LD3 from Enterococcus hirae LD3 Inhibits the Growth of Salmonella enterica subsp. enterica serovar Typhimurium ATCC 13311 in Fruit Juice

In order to prevent the growth of pathogens in food, bacteriocins produced by various probiotic lactic acid bacteria have been recognized as potential substitutes of chemical preservatives. In this study, enterocin LD3 was purified from the cell-free supernatant of a food isolate, Enterococcus hirae LD3 using multistep chromatography. In the fruit juice, lethal concentration (LC₅₀) of enterocin LD3 was found to be 260 µg/mL against Salmonella enterica subsp. enterica serovar Typhimurium ATCC 13311. The cells treated with enterocin LD3 were red colour indicating dead cells after propidium iodide staining, while untreated cells were found blue after staining with 4', 6-diamidino-2-phenylindole. The mechanism of cell killing was analyzed using infrared spectrum of cells treated with enterocin LD3 which was found altered in the range of 1,094.30 and 1,451.82 cm^-1 corresponding to nucleic acids and phospholipids, respectively. The morphology of target cells were severely ruptured and lysed as observed under electron microscopy. Thus, the present study suggested that enterocin LD3 showed bactericidal activity against Salm. enterica subsp. enterica serovar Typhimurium ATCC 13311 and may be applied as a bio-preservative for the safety of fruit juices.

A global genomic analysis of Salmonella Concord reveals lineages with high antimicrobial resistance in Ethiopia

Antimicrobial resistant Salmonella enterica serovar Concord (S. Concord) is known to cause severe gastrointestinal and bloodstream infections in patients from Ethiopia and Ethiopian adoptees, and occasional records exist of S. Concord linked to other countries. The evolution and geographical distribution of S. Concord remained unclear. Here, we provide a genomic overview of the population structure and antimicrobial resistance (AMR) of S. Concord by analysing genomes from 284 historical and contemporary isolates obtained between 1944 and 2022 across the globe. We demonstrate that S. Concord is a polyphyletic serovar distributed among three Salmonella super-lineages. Super-lineage A is composed of eight S. Concord lineages, of which four are associated with multiple countries and low levels of AMR. Other lineages are restricted to Ethiopia and horizontally acquired resistance to most antimicrobials used for treating invasive Salmonella infections in low- and middle-income countries. By reconstructing complete genomes for 10 representative strains, we demonstrate the presence of AMR markers integrated in structurally diverse IncHI2 and IncA/C2 plasmids, and/or the chromosome. Molecular surveillance of pathogens such as S. Concord supports the understanding of AMR and the multi-sector response to the global AMR threat. This study provides a comprehensive baseline data set essential for future molecular surveillance.

Microorganisms in Organic Food-Issues to Be Addressed

The review aimed to analyse the latest data on microorganisms present in organic food, both beneficial and unwanted. In conclusion, organic food's microbial quality is generally similar to that of conventionally produced food. However, some studies suggest that organic food may contain fewer pathogens, such as antibiotic-resistant strains, due to the absence of antibiotic use in organic farming practices. However, there is little discussion and data regarding the importance of some methods used in organic farming and the risk of food pathogens presence. Concerning data gaps, it is necessary to plan and perform detailed studies of the microbiological safety of organic food, including foodborne viruses and parasites and factors related to this method of cultivation and specific processing requirements. Such knowledge is essential for more effective management of the safety of this food. The use of beneficial bacteria in organic food production has not yet been widely addressed in the scientific literature. This is particularly desirable due to the properties of the separately researched probiotics and the organic food matrix. The microbiological quality of organic food and its potential impact on human health is worth further research to confirm its safety and to assess the beneficial properties resulting from the addition of probiotics.

Snapshot of the pollution-driven metabolic and microbiota changes in Carassius gibelio from Bucharest leisure lakes

In the last decades, increased intakes of contaminants and the habitats' destruction have produced drastic changes in the aquatic ecosystems. The environmental contaminants can accumulate in aquatic organisms, leading to the disturbance of the antioxidant/prooxidant balance in fish. In this context, we evaluated the level of organic, inorganic and microbiological pollutants in four leisure lakes (Chitila, Floreasca, Tei and Vacaresti) from Bucharest, the largest city of Romania, in order to compare their effects on hepatopancreas and gills metabolism and antioxidant defense mechanisms in Carassius gibelio, the most known and widespread freshwater fish in this country. The lowest level of oxidative stress was recorded in the case of fish collected from the Vacaresti lake, a protected wetland area where aquatic organisms live in wild environmental conditions. In contrast, significant oxidative changes were observed in the hepatopancreas and gills of fish from the Chitila, Floreasca and Tei lakes, such as reduced glutathione S-transferase activity and glutathione level, and increased degree of lipid peroxidation, being correlated with elevated levels of pesticides (such as 2,4'-methoxychlor) and Escherichia coli load in these organs. Although different patterns of pollutants' accumulation were observed, no important interindividual variations in cytosine methylation degree were determined. In conclusion, the presence and concentrations of metals, pesticides and antibiotics varied with the analyzed tissue and sampling site, and were correlated with changes in the cellular redox homeostasis, but without significantly affecting the epigenetic mechanisms.

Alien species invasion of deep-sea bacteria into mouse gut microbiota

INTRODUCTION

Deep sea has numerous bacteria which dominate in the biomass of deep-sea sediments. Some deep-sea bacteria may possess the capacity to destroy mammal health by the alteration of gut microbiota, acting as potential pathogens.

OBJECTIVES

Pathogenic bacteria are great threats to human health. However, the ultimate origin of pathogenic bacteria has not been intensively explored. In this study, therefore, the influence of deep-sea bacteria on the gut microbiota was evaluated on a global scale.

METHODS

The bacteria isolated from each of 106 deep-sea sediment samples were transplanted into mice in our study to assess the infectiousness of deep-sea bacteria.

RESULTS

The results showed that some bacteria from deep sea, an area that has existed since the earth was formed, could proliferate in mouse gut. Based on the infectious evaluation of the bacteria from each of 106 deep-sea sediments, the bacteria isolated from 13 sediments invaded the gut bacterial communities of mice, leading to the significant alteration of mouse gut microbiota. Among the 13 deep-sea sediments, the bacteria isolated from 9 sediments could destroy mouse health by inducing glucose metabolism deterioration, liver damage and inflammatory symptom. As an example, a bacterium was isolated from deep-sea sediment DP040, which was identified to be Bacillus cereus (termed as Bacillus cereus DP040). Bacillus cereus DP040 could invade the gut microbiota of mice to change the gut microbial structure, leading to inflammatory symptom of mice. The deep-sea sediments containing the bacteria destroying the health of mice were distributed in hydrothermal vent, mid-ocean ridge and hadal trench of the Indian Ocean, the Atlantic Ocean and the Pacific Ocean.

CONCLUSION

Our findings demonstrate that deep sea is an important origin of potential pathogenic bacteria and provide the first biosecurity insight into the alien species invasion of deep-sea bacteria into mammal gut microbiota.

Emergence of colistin resistance and characterization of antimicrobial resistance and virulence factors of Aeromonas hydrophila, Salmonella spp., and Vibrio cholerae isolated from hybrid red tilapia cage culture

Background

Tilapia is a primary aquaculture fish in Thailand, but little is known about the occurrence of antimicrobial resistance (AMR) in Aeromonas hydrophila, Salmonella spp., and Vibrio cholerae colonizing healthy tilapia intended for human consumption and the co-occurrence of these AMR bacteria in the cultivation water.

Methods

This study determined the phenotype and genotype of AMR, extended-spectrum β-lactamase (ESBL) production, and virulence factors of A. hydrophila, Salmonella spp., and V. cholerae isolated from hybrid red tilapia and cultivation water in Thailand. Standard culture methods such as USFDA's BAM or ISO procedures were used for the original isolation, with all isolates confirmed by biochemical tests, serotyping, and species-specific gene detection based on PCR.

Results

A total of 278 isolates consisting of 15 A. hydrophila, 188 Salmonella spp., and 75 V. cholerae isolates were retrieved from a previous study. All isolates of A. hydrophila and Salmonella isolates were resistance to at least one antimicrobial, with 26.7% and 72.3% of the isolates being multidrug resistant (MDR), respectively. All A. hydrophila isolates were resistant to ampicillin (100%), followed by oxytetracycline (26.7%), tetracycline (26.7%), trimethoprim (26.7%), and oxolinic acid (20.0%). The predominant resistance genes in A. hydrophila were mcr-3 (20.0%), followed by 13.3% of isolates having floR, qnrS, sul1, sul2, and dfrA1. Salmonella isolates also exhibited a high prevalence of resistance to ampicillin (79.3%), oxolinic acid (75.5%), oxytetracycline (71.8%), chloramphenicol (62.8%), and florfenicol (55.3%). The most common resistance genes in these Salmonella isolates were qnrS (65.4%), tetA (64.9%), bla _TEM (63.8%), and floR (55.9%). All V. cholerae isolates were susceptible to all antimicrobials tested, while the most common resistance gene was sul1 (12.0%). One isolate of A. hydrophila was positive for int1, while all isolates of Salmonella and V. cholerae isolates were negative for integrons and int _SXT. None of the bacterial isolates in this study were producing ESBL. The occurrence of mcr-3 (20.0%) in these isolates from tilapia aquaculture may signify a serious occupational and consumer health risk given that colistin is a last resort antimicrobial for treatment of Gram-negative bacteria infections.

Conclusions

Findings from this study on AMR bacteria in hybrid red tilapia suggest that aquaculture as practiced in Thailand can select for ubiquitous AMR pathogens, mobile genetic elements, and an emerging reservoir of mcr and colistin-resistant bacteria. Resistant and pathogenic bacteria, such as resistance to ampicillin and tetracycline, or MDR Salmonella circulating in aquaculture, together highlight the public health concerns and foodborne risks of zoonotic pathogens in humans from cultured freshwater fish.

Ecology and epidemiology of Salmonella spp. isolated from the environment and the roles played by wild animals in their maintenance

Salmonella is a ubiquitous organism of public health importance that causes diarrhea and other systemic disease syndromes. The ecology and epidemiology of the organism in addition to the roles played by wild animals are important in understanding its disease. Relevant published peer-reviewed literature was obtained after imputing the study's keywords into the Google search engine. The publications were thereafter saved for the study. The study revealed the ecology of Salmonella is directly related to its epidemiology. These were found to be either positively or negatively influenced by the living and non-living parts of the environment. Free-ranging and captive wild animals can serve as asymptomatic carriers of Salmonella, therefore, help to maintain the cycle of the disease since wildlife serves as reservoir hosts to over 70% of emerging zoonotic diseases. Cockroaches transmit Salmonella through their feces, and body parts and when ingested by birds and animals. The statistically significant over 83% of Salmonella isolation in lizards suggests the reptile could be a source of Salmonella distribution. Snakes, foxes, badgers, rodents, and raccoons have been reported to have Salmonella as a natural component of their gut with the ability to shed the organism often. The high occurrence (>45%) of diverse Salmonella serovars coupled with the fact that some of these animals were handled, kept as pets and consumed by man portends these animals as potential sources of transmission of the organism and the disease. The etiology and epidemiology of Salmonella are overtly affected by several environmental factors which also determine their survival and maintenance. The roles played by wild animals in the relationship, transmission, growth or interaction within and between Salmonella spp., the occurrence, prevalence, and distribution of the organism help maintain the organism in the environment. An understanding of the roles played by the different parts of the environment and wild animals in the ecology and epidemiology of Salmonella can help make informed decisions on the prevention and control of the diseases it causes. This review aimed to investigate the relationship between ecology, epidemiology, and environment, including the roles played by wild animals in the maintenance of the organism and its disease.

Drinking Water From Private Wells and Risks to Children

Drinking water for approximately 23 million US households is obtained from private wells. These wells can become contaminated by pollutant chemicals or pathogenic organisms, leading to significant illness. Although the US Environmental Protection Agency and all states offer guidance for construction, maintenance, and testing of private wells, most states only regulate the construction of new private water wells. With a few exceptions, there is little regulation after construction. Well owners are responsible for their own wells. Children may also drink well water at child care or when traveling. Illness resulting from children’s ingestion of contaminated water can be severe. This report reviews relevant aspects of groundwater and wells; describes the common chemical and microbiologic contaminants; gives an algorithm with recommendations for inspection, testing, and remediation for wells providing drinking water for children; and provides references and Internet resources for more information.

A One-Year Systematic Study to Assess the Microbiological Profile in Oysters from a Commercial Harvesting Area in Portugal

As filter-feeding animals farmed in water bodies exposed to anthropogenic influences, oysters can be both useful bioremediators and high-risk foodstuffs, considering that they are typically consumed raw. Understanding the dynamic of bacterial and viral load in Pacific oyster (Crassostrea gigas) tissues, hemolymph, outer shell surface biofilm, and farming water is therefore of great importance for microbiological risk assessment. A one-year survey of oysters collected from a class B production area (Canal de Mira, on the Portuguese western coast) revealed that these bivalve mollusks have a good depurating capacity with regard to bacteria, as Salmonella spp. and viable enterococci were not detected in any oyster flesh (edible portion) samples, despite the fact that these bacteria have regularly been found in the farming waters. Furthermore, the level of Escherichia coli contamination was clearly below the legal limit in oysters reared in a class B area (>230-≤4600 MPN E. coli/100 g). On the contrary, norovirus was repeatedly detected in the digestive glands of oysters sampled in autumn, winter, and spring. However, their presence in farming waters was only detected during winter.

Isolation and identification of major bacteria from three Ethiopian rift valley lakes live and processed fish, and water samples: implications in sanitary system of fish products

Bacterial pathogens are a great threat to fish production. Gram-negative bacteria are among the major bacterial fish pathogens and are zoonotic with the potential to infect humans. This cross-sectional study was conducted to isolate and identify major gram-negative bacteria from live and processed fish, and water samples from Lakes Hawassa, Langanoo and Ziway. A total of 674 different types of samples: 630 tissue samples (210 samples for each intestine, Kkidney and liver collected from 210 live fish (Oreochromis niloticus, Cyprinus carpio and Clarias gariepinus), 20 processed fish samples from lake Ziway fish processing center and 24 lake water samples were included in the study from each lake. The mean values of pH, temperature, dissolved oxygen and nitrate in all water samples were within the normal range at which most freshwater fish species become non-stressed. Of a total of 674 samples included in the study, bacteria were isolated from 154(22.8%) samples with significant difference (P < 0.05) observed in some isolates with respect to sample origin. Of these 154 isolates, 103(66.8%) isolates were gram-negative bacteria consisting of 15 species based on morphology and a range of biochemical tests. From live fish samples, Escherichia coli was the dominant species with 15 isolates followed by Edwardsiella tarda (12), Salmonella Paratyphi (10), Salmonella Typhi (9),  Shigella dysenteriae (7), Shigella flexneri (7), Klebsiella pneumonia (7), Enterobacter aerogenes (6), Enterobacter cloacae (5), Pseudomonas aeruginosa (5), Vibrio parahemolyticus (5), Aeromonas sobria (4), Citrobacter freundii (4), Citrobacter koseri (4) and Plesiomonas shigelloides (3). The detection of the common fecal coliforms (E. coli, K. pneumoniae and E. aerogenes) and Salmonella spp. in processed fish indicates the potential danger of passage of pathogenic bacteria and/or their poisons to humans via infected and/or contaminated fish products. Human infection by pathogenic fish bacteria and food poisoning is possible through contamination of fish product in fish production chain due to inadequate handling, poor hygiene and contact with contaminated water. Therefore, producers, consumers and all other stakeholders need to be cautious during handling, processing and consumption of fish harvested from the study lakes.

Flagellar Phenotypes Impact on Bacterial Transport and Deposition Behavior in Porous Media: Case of Salmonella enterica Serovar Typhimurium

Bacterial contamination of groundwater has always been an ecological problem worthy of attention. In this study, Salmonella enterica serovar Typhimurium with different flagellar phenotypes mainly characterized during host-pathogen interaction were analyzed for their transport and deposition behavior in porous media. Column transport experiments and a modified mobile-immobile model were applicated on different strains with flagellar motility (wild-type) or without motility (ΔmotAB), without flagella (ΔflgKL), methylated and unmethylated flagellin (ΔfliB), and different flagella phases (fliC^ON, fljB^ON). Results showed that flagella motility could promote bacterial transport and deposition due to their biological advantages of moving and attaching to surfaces. We also found that the presence of non-motile flagella improved bacterial adhesion according to a higher retention rate of the ΔmotAB strain compared to the ΔflgKL strain. This indicated that bacteria flagella and motility both had promoting effects on bacterial deposition in sandy porous media. Flagella phases influenced the bacterial movement; the fliC^ON strain went faster through the column than the fljB^ON strain. Moreover, flagella methylation was found to favor bacterial transport and deposition. Overall, flagellar modifications affect Salmonella enterica serovar Typhimurium transport and deposition behavior in different ways in environmental conditions.

Design and Development of Magnetic Iron Core Gold Nanoparticle-Based Fluorescent Multiplex Assay to Detect Salmonella

Salmonella is a bacterial pathogen which is one of the leading causes of severe illnesses in humans. The current study involved the design and development of two methods, respectively using iron oxide nanoparticle (IONP) and iron core gold nanoparticle (ICGNP), conjugated with the Salmonella antibody and the fluorophore, 4-Methylumbelliferyl Caprylate (4-MUCAP), used as an indicator, for its selective and sensitive detection in contaminated food products. Twenty double-blind beverage samples, spiked with Salmonella enteritidis, Staphylococcus aureus, and Escherichia coli, were prepared in sterile Eppendorf^® tubes at room temperature. The gold layer and spikes of ICGNPs increased the surface areas. The ratio of the surface area is 0.76 (IONPs/ICGNPs). The comparative sensitivity and specificity of the IONP-based and the ICGNP-based methods to detect Salmonella were determined. The ICGNP method shows the limit of detection is 32 Salmonella per mL. The ICGNPs had an 83.3% sensitivity and a 92.9% specificity value for the presence and detection of Salmonella. The IONP method resulted in a limit of detection of 150 Salmonella per mL, and a 66.7% sensitivity and 83.3% specificity for the presence and detection of Salmonella. The higher surface area of ICGNPs increases the efficiency of detection. The monitoring of Salmonella can thus be achieved by a rapid magnetic fluorescent assay using a smartphone for image capture and analyze, providing quantitative results. The findings from the present study would help to detect Salmonella rapidly in water. It can improve the microbial quality of water and food safety due to the presence of Salmonella in the water environment.

Variations in Bacterial Communities and Antibiotic Resistance Genes Across Diverse Recycled and Surface Water Irrigation Sources in the Mid-Atlantic and Southwest United States: A CONSERVE Two-Year Field Study

Reduced availability of agricultural water has spurred increased interest in using recycled irrigation water for U.S. food crop production. However, there are significant knowledge gaps concerning the microbiological quality of these water sources. To address these gaps, we used 16S rRNA gene and metagenomic sequencing to characterize taxonomic and functional variations (e.g., antimicrobial resistance) in bacterial communities across diverse recycled and surface water irrigation sources. We collected 1 L water samples (n = 410) between 2016 and 2018 from the Mid-Atlantic (12 sites) and Southwest (10 sites) U.S. Samples were filtered, and DNA was extracted. The V3-V4 regions of the 16S rRNA gene were then PCR amplified and sequenced. Metagenomic sequencing was also performed to characterize antibiotic, metal, and biocide resistance genes. Bacterial alpha and beta diversities were significantly different (p < 0.001) across water types and seasons. Pathogenic bacteria, such as Salmonella enterica, Staphylococcus aureus, and Aeromonas hydrophilia were observed across sample types. The most common antibiotic resistance genes identified coded against macrolides/lincosamides/streptogramins, aminoglycosides, rifampin and elfamycins, and their read counts fluctuated across seasons. We also observed multi-metal and multi-biocide resistance across all water types. To our knowledge, this is the most comprehensive longitudinal study to date of U.S. recycled water and surface water used for irrigation. Our findings improve understanding of the potential differences in the risk of exposure to bacterial pathogens and antibiotic resistance genes originating from diverse irrigation water sources across seasons and U.S. regions.

Role of RpoS in Regulating Stationary Phase Salmonella Typhimurium Pathogenesis-Related Stress Responses under Physiological Low Fluid Shear Force Conditions

The discovery that biomechanical forces regulate microbial virulence was established with the finding that physiological low fluid shear (LFS) forces altered gene expression, stress responses, and virulence of the enteric pathogen Salmonella enterica serovar Typhimurium during the log phase. These log phase LFS-induced phenotypes were independent of the master stress response regulator, RpoS (σ^S). Given the central importance of RpoS in regulating stationary-phase stress responses of S. Typhimurium cultured under conventional shake flask and static conditions, we examined its role in stationary-phase cultures grown under physiological LFS. We constructed an isogenic rpoS mutant derivative of wild-type S. Typhimurium and compared the ability of these strains to survive in vitro pathogenesis-related stresses that mimic those encountered in the infected host and environment. We also compared the ability of these strains to colonize (adhere, invade, and survive within) human intestinal epithelial cell cultures. Unexpectedly, LFS-induced resistance of stationary-phase S. Typhimurium cultures to acid and bile salts stresses did not rely on RpoS. Likewise, RpoS was dispensable for stationary-phase LFS cultures to adhere to and survive within intestinal epithelial cells. In contrast, the resistance of these cultures to challenges of oxidative and thermal stresses, and their invasion into intestinal epithelial cells was influenced by RpoS. These findings expand our mechanistic understanding of how physiological fluid shear forces modulate stationary-phase S. Typhimurium physiology in unexpected ways and provide clues into microbial mechanobiology and nuances of Salmonella responses to microenvironmental niches in the infected host.

IMPORTANCE Bacterial pathogens respond dynamically to a variety of stresses in the infected host, including physical forces of fluid flow (fluid shear) across their surfaces. While pathogens experience wide fluctuations in fluid shear during infection, little is known about how these forces regulate microbial pathogenesis. This is especially important for stationary-phase bacterial growth, which is a critical period to understand microbial resistance, survival, and infection potential, and is regulated in many bacteria by the general stationary-phase stress response protein RpoS. Here, we showed that, unlike conventional culture conditions, several stationary-phase Salmonella pathogenic stress responses were not impacted by RpoS when bacteria were cultured under fluid shear conditions relevant to those encountered in the intestine of the infected host. These findings offer new insight into how physiological fluid shear forces encountered by Salmonella during infection might impact pathogenic responses in unexpected ways that are relevant to their disease-causing ability.

Environmental and anthropogenic factors associated with the likelihood of detecting Salmonella in agricultural watersheds

Surface water is one of the primary sources of irrigation water for produce production; therefore, its contamination by foodborne pathogens, such as Salmonella, may substantially impact public health. In this study, we determined the presence of Salmonella in surface water and characterized the relationship between Salmonella detection and environmental and anthropogenic factors. From April 2019 to February 2020, 120 samples from 30 sites were collected monthly in four watersheds located in two different central Chile agricultural regions (N = 1080). Water samples from rivers, canals, streams, and ponds linked to each watershed were obtained. Surface water (10 L) was filtrated in situ, and samples were analyzed for the presence of Salmonella. Salmonella was detected every month in all watersheds, with a mean detection percentage of 28% (0%-90%) across sampling sites, regardless of the season. Overall, similar detection percentages were observed for both regions: 29.1% for Metropolitan and 27.0% for Maule. Salmonella was most often detected in summer (39.8% of all summer samples tested positive) and least often in winter (14.4% of winter samples). Random forest analysis showed that season, water source, and month, followed by latitude and river, were the most influential factors associated with Salmonella detection. The influences of water pH and temperature (categorized as environmental factors) and factors associated with human activity (categorized as anthropogenic factors) registered at the sampling site were weakly or not associated with Salmonella detection. In conclusion, Salmonella was detected in surface water potentially used for irrigation, and its presence was linked to season and water source factors. Interventions are necessary to prevent contamination of produce, such as water treatment before irrigation.