First Nation-Wide Analysis of Food Safety and Acceptability Data in Lebanon

Risk Factors and Hospitalizations Associated with Pediatric Adenovirus and Rotavirus Infections in Northern Lebanon

Background and Objectives: Acute gastroenteritis (AGE) is a major contributor to pediatric morbidity and mortality worldwide. There is a scarcity of data on AGE in North Lebanon, a region profoundly affected by the Syrian refugee crisis and water sanitation issues. This study examines the prevalence, risk factors, and seasonal variations in adenovirus and rotavirus infections in children with AGE in North Lebanon. Materials and Methods: A cross-sectional study was conducted from September 2022 to August 2023 on 400 children (1 month to 5 years old) with AGE that were admitted to pediatric departments of three private hospitals in North Lebanon. Stool samples were collected and tested using chromatographic immunoassays. Comprehensive demographic and clinical data were collected and analyzed. Results: Rotavirus was the most frequent viral agent (28%), followed by adenovirus (12.3%) and mixed infections (5.5%). Rotavirus vaccination demonstrated a significant protective effect, and lower infection rates were associated with breastfeeding and consumption of bottled water (p < 0.001). Higher infection rates correlated with lower levels of maternal education and household incomes (p < 0.001). Malnutrition significantly increased susceptibility to rotavirus infections (p < 0.001). Conclusions: This study emphasized the urgent need for targeted public health interventions in North Lebanon to mitigate the burden of rotavirus and adenovirus-induced acute gastroenteritis among children.

Salmonella Prevalence and antibiotic resistance profile in raw poultry meat sold in North Lebanon: Insights from the COVID-19 pandemic and economic crisis

Salmonella-related foodborne illness is a significant public health concern, with the primary source of human infection being animal-based food products, particularly chicken meat. Lebanon is currently experiencing a dual crisis: the COVID-19 pandemic and an unprecedented economic crisis, which has resulted in substantial challenges to the public health system and food safety. This study aims to assess the prevalence and antibiotic resistance profile of Salmonella in raw poultry meat sold in North Lebanon during this dual crisis. A cross-sectional study was carried out between May 2021 and April 2022 across six different districts in North Lebanon. A total of 288 whole, unprocessed chickens were examined. The isolation and identification of Salmonella isolates were done based on cultural and biochemical properties. All isolates were subjected to antimicrobial susceptibility testing and phenotypic assays for Extended-Spectrum Beta-lactamase (ESBL) detection. The prevalence of Salmonella in raw poultry meat purchased in North Lebanon reached 18.05 % (52/288). The dry season and chilled chicken were significantly associated with an increased risk of Salmonella contamination (P < 0.05). Additionally, 34.61 % of the isolates were potential ESBL producers, and 57.69 % exhibited multidrug resistance (MDR). This study highlights the existence of MDR in chicken meat in North Lebanon, posing a potential health risk if undercooked chicken meat is consumed. This emphasizes the importance of the implementation of preventive strategies and hygienic procedures throughout the food chain to reduce the risk of Salmonella spp. contamination in chicken meats and its potential transmission to humans.

Emergence of Extended-Spectrum Cephalosporin- and Colistin-Resistant Enterobacterales in Otherwise Healthy University Students

Resistance to last resort antibiotics has been increasing, particularly in low- and middle-income countries such as Lebanon, which has well established challenges in antimicrobial stewardship and other public health and environmental issues. However, data on the emergence of antibiotic resistance in the community in Lebanon are limited. In this study, we assessed resistance to last resort antibiotics in the fecal samples of 111 otherwise healthy university students in north Lebanon. The results showed that 47.7% of the samples harbored extended-spectrum cephalosporin-resistant isolates, while 2.7% of the samples yielded colistin-resistant isolates. Furthermore, molecular analyses showed that the β-lactamase gene group, blaCTX-M-1 group, was detected in the majority (93%) of screened extended-spectrum β-lactamase isolates. In addition, the colistin-resistant Escherichia coli isolates carried mcr-1, including the novel mcr-1.26 variant, which was previously reported in clinical samples as well as in domesticated animals and the environment in Lebanon. Taken together, these findings highlight the occurrence of resistance to important antibiotics in the community, perhaps suggesting diffuse sources, including clinical and environmental settings, and multiple factors driving the spread of multidrug-resistant bacteria and resistance determinants. There is a pressing need for comprehensive antimicrobial stewardship programs and the implementation of evidence-based practices in clinical and community settings to mitigate the increasing spread of antimicrobial resistance.

Hygienic sanitary risk and microbiological quality of meat and meat-contact surfaces in traditional butcher shops and retail establishments- lessons from a developing country

In this study, we determined both hygienic sanitary risk and microbiological quality of raw meat and meat-contact surfaces in butcher shops and retails from the North Governorate in Lebanon. A total of 55 samples were analyzed (36 raw meat and 19 environmental swabs). The overall counts of pathogenic bacteria indicate high levels of contamination of both minced meat and contact surfaces. Presumptive Salmonella and Listeria were found in the samples. Salmonella spp. was observed in 63.8% of all cuts, of whom 41.6% is detected from butcher shops' meat. L. monocytogenes was present in 47.2% of meat from butcher shops and 30.5% of retails. Total aerobic count followed by S. aureus and fecal coliforms were the most detected pathogens in environmental swabs. Most visited facilities presented moderate hygienic sanitary risk, with average scores of 55.25 in butchers' shops and 65.25 in retail. Findings highlight the necessity for governmental surveillance and implementation of food safety laws.

Raw Meat Consumption and Food Safety Challenges: A Survey of Knowledge, Attitudes, and Practices of Consumers in Lebanon

A key contributor to foodborne illnesses is consuming contaminated ready-to-eat foods, including raw meats. The latter is a common practice in Lebanon, a country that suffers from widespread pollution and food safety challenges. However, studies on the safety of raw meat consumption in Lebanon are limited. In this study, an attempt was made to investigate the knowledge, attitudes, and practices (KAPs) of the Lebanese population toward the potential risk associated with the consumption of raw meats, and to identify factors that affect KAP levels. An online survey (n = 577) was administered to Lebanese adults aged 18 years and above to assess their KAPs. The results showed that 74.5% of the participants consumed raw meat, 44% had good food safety knowledge, and 30.7% exhibited good practices. However, more than half of the participants (61.9%) showed a positive attitude toward food safety. There was a significant association between knowledge and attitude (p < 0.001), attitude and practices (p < 0.001), and knowledge and practices (p < 0.001), thereby indicating that an increase in food safety education could translate into better practices in this population. Accordingly, efforts to enhance education on food safety are warranted to reduce the potential risk of food poisoning associated with raw meat consumption in Lebanon.

Parasitic Contamination of Fresh Leafy Green Vegetables Sold in Northern Lebanon

Contaminated, raw or undercooked vegetables can transmit parasitic infections. Here, we investigated parasitic contamination of leafy green vegetables sold in local markets in the Tripoli district, Lebanon, during two consecutive autumn seasons (2020-2021). The study involved the microscopic examination of 300 samples of five different types of vegetables (60 samples per type) and used standardized qualitative parasitological techniques for some protozoa and helminths. The results showed that 16.7% (95% interval for p: 12.6%, 21.4%) (50/300) of the vegetable samples were contaminated with at least one parasite. The most frequently detected parasite was Blastocystis spp. (8.7%; 26/300); this was followed in frequency by Ascaris spp. (3.7%; 11/300). Among the different vegetable types, lettuce (23.3%; 14/60) was the most contaminated, while arugula was the least contaminated (11.7%; 7/60). The statistical analysis did not reveal any significant association between the prevalence of parasitic contamination and the investigated risk factors, which included collection date, vegetable type, market storage status, and wetness of vegetables at the time of purchase (p > 0.05). The high prevalence of parasitic contamination also suggested the potential presence of other microbial pathogens. These findings are important because leafy green vegetables are preferentially and heavily consumed raw in Lebanon. Thus, implementing effective measures that target the farm-to-fork continuum is recommended in order to reduce the spread of intestinal pathogens.

Assessment of the Microbiological Acceptability of White Cheese (Akkawi) in Lebanon and the Antimicrobial Resistance Profiles of Associated Escherichia coli

Dairy foods are a staple in Lebanon, a low- and middle-income country that has been experiencing serious challenges to food safety and antimicrobial stewardship among other issues. The microbiological acceptability of dairy products has been of increasing concern. This is partially due to the failing economy and prolonged power outages that affect the quality of raw material and disrupt the dairy cold chain, respectively. Therefore, we assessed the microbiological acceptability of Akkawi, a popular white-brined cheese in Lebanon. For this purpose, we quantified the densities of Escherichia coli (a fecal indicator) and Staphylococcus aureus in cheeses collected from Lebanese retail stores. Additionally, we evaluated the antibiotic resistance profiles of the E. coli isolated from the cheese. E. coli and S. aureus were detected in 40 (80%) and 16 (32%) of the 50 cheese samples, respectively. Notably, 40 (80%) and 16 (32%) of the samples exceeded the maximum permissible limit of E. coli and S. aureus, respectively. A high percentage of the 118 E. coli isolated from the cheeses showed resistance to clinically and agriculturally important antibiotics, while 89 (75%) isolates were classified as multidrug-resistant (MDR). Given that Akkawi can be consumed without cooking, our findings highlight serious food safety and antimicrobial resistance problems that require immediate interventions.

The indelible toll of enteric pathogens: Prevalence, clinical characterization, and seasonal trends in patients with acute community-acquired diarrhea in disenfranchised communities

BACKGROUND

There is little information on the epidemiology of enteric pathogens in Lebanon, a low- and middle-income country that suffers from a myriad of public health challenges. To address this knowledge gap, we aimed to assess the prevalence of enteric pathogens, identify risk factors and seasonal variations, and describe associations between pathogens among diarrheic patients in the Lebanese community.

METHODOLOGY AND PRINCIPAL FINDINGS

A multicenter cross-sectional community-based study was conducted in the north of Lebanon. Stool samples were collected from 360 outpatients suffering from acute diarrhea. Based on fecal examination using the BioFire® FilmArray® Gastrointestinal Panel assay, the overall prevalence of enteric infections was 86.1%. Enteroaggregative Escherichia coli (EAEC) was the most frequently identified (41.7%), followed by enteropathogenic E. coli (EPEC) (40.8%) and rotavirus A (27.5%). Notably, two cases of Vibrio cholerae were identified, while Cryptosporidium spp. (6.9%) was the most common parasitic agent. Overall, 27.7% (86/310) of the cases were single infections, and the majority, 73.3% (224/310), were mixed infections. Multivariable logistic regression models showed that enterotoxigenic E. coli (ETEC) and rotavirus A infections were significantly more likely to occur in the fall and winter compared to the summer. Rotavirus A infections significantly decreased with age but increased in patients living in rural areas or suffering from vomiting. We identified strong associations in the co-occurrence of EAEC, EPEC, and ETEC infections and a higher percentage of rotavirus A and norovirus GI/GII infections among EAEC-positive cases.

CONCLUSIONS

Several of the enteric pathogens reported in this study are not routinely tested in Lebanese clinical laboratories. However, anecdotal evidence suggests that diarrheal diseases are on the rise due to widespread pollution and the deterioration of the economy. Therefore, this study is of paramount importance to identify circulating etiologic agents and prioritize dwindling resources to control them and limit outbreaks in the future.

Socio-demographic determinants of knowledge, attitude and practices towards food safety among Lebanese population during the economic crisis: a cross-sectional study

BACKGROUND

Lebanon has been gripped by an economic crisis and the local currency has lost more than 90% of its value; besides, a lack of consistent electricity supply which has contributed to rising concerns about food safety especially among households. This study aimed to assess Lebanese society knowledge, attitude and practice towards food safety during the economic crisis.

METHODS

A cross-sectional study was conducted in Lebanon between September 5 and January 30, 2021. Data was collected through an online survey that included information on socio-demographic characteristics, knowledge, attitude and practice of Lebanese consumers towards food safety. Two multivariate regression models were performed on the knowledge and practices as a dependent variable. 95% confidence interval was calculated. All tests were two-sided and statistical significance was set at p-value < 0.05.

RESULTS

The majority of participants had good knowledge regarding food safety (74.9%) while more than half of the respondents adopted good preventive practices (62.8%). Multivariate regression of factors associated with good knowledge regarding food safety showed married participants (adjusted OR = 2.1; p < 0.0001), who had university degree and above (adjusted OR = 2.0; p < 0.0001), and who had income < 1,500,000 LBP (adjusted OR = 1.7; p < 0.0001) had a significantly good knowledge score compared to their counterparts. Finally, participants aged more than 35 years old and who had income higher than 1,500,000 LBP (adjusted OR = 1.8; p < 0.0001 and adjusted OR = 1.9; p = 0.01 respectively) were positively associated to good practice towards food safety.

CONCLUSION

This study offers useful insights into the knowledge, attitude and practices of Lebanese consumers towards food safety during the economic crisis.

Microbiological and chemical evaluation of dairy products commercialized in the Lebanese market

Background and Aim

Cheese is considered an essential component of the Lebanese table, however, several foodborne illnesses have been reported due to cheese consumption. This study aimed to assess the microbiological quality and the occurrence of antibiotic and pesticide residues in two traditional Lebanese cheeses, Akkawi and Baladiyeh. In addition, drug resistance of isolated pathogens from the cheese samples was evaluated.

Materials and Methods

Fifty Akkawi and Baladiyeh cheese samples were obtained in duplicate from 37 different commercial brands in supermarkets and shops from various regions of Lebanon. Samples of different weights were either individually vacuum packed or soaked in brine unpacked where it was placed in plastic bag after being purchased. Samples were homogenized to determine antibiotic and pesticide residues using liquid and gas chromatography coupled to mass spectrometry, and microbiological evaluation was performed according to the International Organization for Standardization reference analytical methods. The disk diffusion method was used to determine the susceptibility of these isolates to antibiotics.

Results

Microbiologically, 17% of Akkawi and 14% of Baladiyeh samples were found to be non-conforming. The bacterial isolates (n = 29) were tested for their susceptibility to 11 different antibiotics commonly prescribed in the Lebanese community or used for treating infections caused by Gram-negative bacteria and listeriosis. Each isolate was found to be resistant to at least three antibiotics. Liquid and gas chromatography coupled to mass spectroscopy analysis showed the absence of pesticide residues in all samples. However, sulfamethazine antibiotic residue was found in 14% of the samples.

Conclusion

The results suggest that the cheese samples tested could cause foodborne illnesses due to the detection of pathogenic bacteria and are a public health concern due to the presence of antibiotic residues and the transmission of multidrug-resistant organisms.

Detection and Determination of Staphylococcus aureus in Camel Milk and Associated Factors in Fedis, Eastern Hararghe, Ethiopia

Background

Camel milk is the key food for pastoralists in the arid and semi-arid areas of the eastern lowlands of Ethiopia. Unless it is handled under good hygienic conditions, milk can be a good medium for bacterial growth and can lead to foodborne diseases caused by various pathogenic microorganisms, such as Staphylococcus aureus. The current study was aimed to determine the prevalence of Staphylococcus aureus in raw camel milk and associated factors in Fedis, Eastern Ethiopia.

Methods

A cross-sectional study was conducted from December 2, 2018 to May 26, 2019 in Fedis, Eastern Hararghe, Ethiopia. The questionnaire was used to determine the hygienic practices of camel milkers and sellers. Laboratory analysis was conducted to determine the level of Staphylococcus aureus. A total of 156 (78 from households and 78 from selling sites) milk samples were collected randomly from selected camel herd owners and selling sites for the isolation and enumeration of Staphylococcus aureus. Data analysis was carried out using SPSS software version 22.0. Finally, Chi-square and Fisher's exact tests were used to analyze the data. A P-value of .05 was considered as the cut-off point for statistical significance.

Results

A total of 156 samples, including 78 samples of raw milk from the households and 78 samples from the market were purchased to determine Staphylococcus aureus. Out of 156 samples, Staphylococcus aureus was detected in 60 (38.5%) samples, of which 27 (34.6%) and 33 (42.3%) were among those collected from household and market, respectively. The overall mean Staphylococcus aureus count was 4.83 log CFU/mL, with household and market samples accounted for 2.76 and 5.08 log CFU/mL, respectively. Furthermore, 23 (38.3%) of the samples were contaminated with Staphylococcus aureus beyond the recommended level (4-5 log CFU/mL). There was a statistically significant association (P-value of <.05) between the prevalence of Staphylococcus aureus and other variables such as age of the camel, parity, lactation stages, and sources of milk.

Conclusion

More than one-third of milk samples were contaminated with Staphylococcus aureus at levels higher than the maximum permitted level. The findings of the current study suggests that there is a potential risk of foodborne infection and intoxication. Therefore, implementation of adequate hygiene and safety practices is very important to prevent the consumption of contaminated fruit juices, which leads to foodborne illness.

Pathogenic Bacterial Species in Locally Prepared Fresh Fruit Juices Sold in Juice Houses of Eastern Ethiopia

Fruit juices are important components of a healthy diet and a dietary source of nutrients, vitamins, and fiber and vital for human health. However, unless it is handled with safety and hygienic conditions, food can be a vehicle for the transmission of various agents of diseases resulting in food borne outbreaks. Thus, this study aimed to determine common pathogenic bacterial species in locally prepared fresh fruit juices sold in juice houses of Eastern Ethiopia. A cross-sectional study design was conducted from 1 January to 27 March 2020, in eastern Ethiopia. Seventy-eight juice samples were collected aseptically using a sterilized collecting jar from each juice house. Pour plate count method was used to determine Staphylococcus, Salmonella, and Shigella species. Finally, the data were analyzed using descriptive statistical tests such as Chi-square and Fisher's exact tests. P-value of .05 was considered as a cut point for statistical significance. The study found Staphylococcus count ranged from 1.68 log CFU/mL with the mean value of 4.204 log CFU/mL. Overall, 58 (74.4%) of the fruit juice samples had Staphylococcus count, 19 (24.4%) had Salmonella and 12 (15.4%) had Shigella higher than the maximum permitted limit of Gulf standard, 2000 set for any type of fruit juice. In general, the study found more than two-thirds of fruit juice samples had at least 1 pathogenic bacteria species higher than the maximum permitted limit and potentially hazardous to consumer health. Thus, regular supervision and application of food hygiene and safety are essential to improve the quality of fruit juice and to prevent the consumption of contaminated fruit juices, which leads to food borne illness.

Bacteriological Quality of Locally Prepared Fresh Fruit Juice Sold in Juice Houses of Eastern Ethiopia

BACKGROUND

Currently, fresh fruit juices are widely consumed as a drink worldwide due to their nutritional values and health benefits. Fresh fruit juices are an important source of nutrients, vitamins, and fibers that are important for human health. Fruit juices are nutritious and perishable food that can serve as an ideal medium for the growth and multiplication of pathogenic microorganisms. Therefore, this study aimed to determine the bacteriological quality of locally prepared fresh fruit juices sold in juice houses of eastern Ethiopia from 4 April to 12 June 2020.

METHODS

A cross-sectional study was used that included administrative questionnaires and laboratory-based investigations. A total of 78 fruit juice samples that include mango, avocado, papaya, and mixed juices were collected aseptically from the juice houses. The most probable number method was used to determine the total coliform, fecal coliform and Escherichia coli. The pour plate count method was used to determine the total viable bacteria count. Finally, data were analyzed using descriptive statistical tests that included analysis of variance, Chi-square and Fisher's exact tests. A P-value of .05 was considered as a cut-off point for statistical significance.

RESULTS

Among the 78 juice samples analyzed, 85.9% of the samples had total viable bacterial count, 64.1% had total coliform count, 60.3% had fecal coliform, and 33.3% of the samples had Escherichia coli higher than the maximum permitted level of Gulf standard 2000. The study found a significant association between bacterial contamination and educational status (χ2 = 31.663), training in food hygiene and safety (χ2 = 23.04), method of fruit preservation (χ2 = 17.98), place to keep the juice (χ2 = 13.7), action done with the juice gone bad (χ2 = 12.78), frequency of cleaning materials used to keep the juice (χ2 = 12.78), type of dish washing (χ2 = 19.75), availability of hand washing equipment (χ2 = 12.78), and types of waste receptacles (χ2 = 26.25) (P-value <.05) (Table 5).

CONCLUSION

In general, majority of fruit juice samples were contaminated with one or more different bacteria species higher than the maximum permitted level. Furthermore, the study found the association between bacterial contamination and other variables such as hygienic and safety conditions. Therefore, the implementation of adequate hygiene and safety practices is very important to prevent the consumption of contaminated fruit juices, which leads to foodborne illness.

Genome sequence of a multidrug-resistant Campylobacter coli strain isolated from a newborn with severe diarrhea in Lebanon

A multidrug-resistant (MDR) Campylobacter coli (C. coli) strain was isolated from a 2-month-old newborn who suffered from severe diarrhea in Lebanon. Here, whole-genome sequencing (WGS) analysis was deployed to determine the genetic basis of antimicrobial resistance and virulence in the C. coli isolate and to identify its epidemiological background (sequence type). The identity of the isolate was confirmed using API® Campy, MALDI-TOF, and 16S rRNA gene sequencing analysis. The antimicrobial susceptibility phenotype was determined using the disk diffusion assay. Our analysis showed that resistance to macrolide and quinolone was potentially associated with the presence of multiple point mutations in antibiotic targets on the chromosomal DNA. Furthermore, tetracycline and aminoglycoside resistance were encoded by genes on a pTet plasmid. The bla_OXA-61, which is associated with beta-lactam resistance, was also detected in the C. coli genome. A set of 30 genes associated with the virulence in C. coli was detected using WGS analysis. MLST analysis classified the isolate as belonging to a new sequence type (ST-9588), a member of ST-828 complex which is mainly associated with humans and chickens. Taking together, this study provides the first WGS analysis of Campylobacter isolated from Lebanon. The detection of a variety of AMR and virulence determinants strongly emphasizes the need for studying the burden of Campylobacter in Lebanon and the Middle East and North Africa (MENA) region, where information on campylobacteriosis is scant.

Development of national dietary and lifestyle guidelines for pregnant women in Lebanon

Although a number of international diet and lifestyle guidelines during pregnancy (DLGP) exist in the literature, contextualization to low- and middle-income settings is less common. The aim of this study was to present the Lebanese DLGP and to describe the process followed for their development. A mixed-method approach was used including a review and synthesis of existing international DLGP and a consensus building nominal group technique (NGT) with a multidisciplinary group of experts (n = 11). During the meeting, participants identified the themes of the guidelines, formulated the wording of each themes' guideline and translated the guidelines to the Arabic language. Consensus was defined as an agreement of 80%. Reviewing the literature, a list of 17 main topics were found to be common themes for the DLGP. For the Lebanese DLGP, participants in the NGT meeting selected seven themes from this list: gestational weight gain, diet diversity, hydration, food safety, harmful foods, physical activity and breastfeeding. In addition, the group formulated three themes based on merging/modifying existing themes: supplementation, alcohol and smoking and religious fasting. Two context-specific new themes emerged: wellbeing and nutrition resilience. For each of the identified themes, the group agreed upon the wording of its guidelines and description. This study is the first from the Eastern Mediterranean Region to develop through consensus building, context and culture-specific dietary and lifestyle guidelines for pregnant women. Putting maternal nutrition at the heart of tackling malnutrition and its detrimental health outcomes is a core investment for a better maternal and child health.

Nationwide Assessment of Water Quality in Rivers across Lebanon by Quantifying Fecal Indicators Densities and Profiling Antibiotic Resistance of Escherichia coli

The use of contaminated water has been associated with severe disease outbreaks. Due to widespread pollution with untreated sewage, concerns have been raised over water quality in Lebanon, a country with well-documented challenges in infrastructure. Here, we evaluated the water quality of major rivers in Lebanon by quantifying the densities of fecal indicator bacteria (fecal coliforms and Escherichia coli). Additionally, we assessed the dissemination of antibiotic-resistant E. coli in river water. Composite water samples (n = 132) were collected from fourteen rivers, and 378 E. coli were isolated and analyzed. Fecal coliforms and E. coli were detected in 96.29% and 95.5% of the samples, respectively. Additionally, 73.48–61.3% and 31.81% of the samples exceeded the microbiological acceptability standards for irrigation and the fecal coliform limit for recreational activities, respectively. The E. coli exhibited resistance to ampicillin (40% of isolates), amoxicillin + clavulanic acid (42%), cefepime (4%), cefotaxime (14%), cefalexin (46%), cefixime (17%), doripenem (0.3%), imipenem (0.5%), gentamicin (6%), kanamycin (9%), streptomycin (35%), tetracycline (35%), ciprofloxacin (10%), norfloxacin (7%), trimethoprim-sulfamethoxazole (32%), and chloramphenicol (13%). Notably, 45.8% of the isolates were classified as multidrug resistant (MDR). Our results highlight the need to urgently address fecal pollution and the dissemination of antibiotic resistance in Lebanese rivers.

Salmonella spvC Gene Inhibits Autophagy of Host Cells and Suppresses NLRP3 as Well as NLRC4

Salmonella spvC gene, encoding a phosphothreonine lyase on host mitogen-activated protein kinases, facilitates systemic infection of Salmonella while the precise mechanisms remain elusive. Autophagy and pyroptosis dependent on the activation of inflammasomes, as parts of innate immune response, contribute to host defense against Salmonella infection. Recently, we reported that spvC could inhibit pyroptosis. To explore the effect of spvC on autophagy and the relationship between its function in pyroptosis and autophagy, infection models of macrophages J774A.1 and epithelial HeLa cells co-cultured with Salmonella Typhimurium wild type, spvC deletion, site-directed mutant which lacks phosphothreonine lyase activity, or complemented strain were established. The levels of LC3 turnover and Beclin 1 of J774A.1 cells were determined by western blot. Confocal laser scanning microscopy was used to visualize the autophagic flux after being transfected with mRFP-GFP-LC3 plasmid in HeLa cells. Results showed that SpvC inhibited autophagosome formation through its phosphothreonine lyase activity. Additionally, analysis of nucleotide-binding oligomerization domain, leucine-rich repeat and pyrin domain-containing 3 (NLRP3) and NLR with CARD domain-containing 4 (NLRC4) in J774A.1 cells indicated that spvC decreased the protein levels of NLRP3 and NLRC4, which were significantly changed by autophagy inhibitor Bafilomycin A1. Together, our observations reveal a novel mechanism of spvC in Salmonella pathogenesis and host inflammatory response via inhibiting autophagy and NLRP3 as well as NLRC4. These pathways and their subversion by diverse pathogen virulence determinants are expected to throw light on the design of anti-infective agents.