Human Salmonellosis Research Articles

Pet Reptiles: A Potential Source of Transmission of Multidrug-Resistant Salmonella.

Salmonella spp. is widely considered one of the most important zoonotic pathogens worldwide. The close contact between reptiles and their owners provides favourable conditions for the transmission of zoonotic pathogen infections, and ~6% of human salmonellosis cases are acquired after direct or indirect contact with reptiles. Moreover, antimicrobial resistance is one of the most important health threats of the twenty-first century and has been reported in Salmonella strains isolated from pet reptiles, which could entail therapeutic consequences for their owners and breeders. The aim of this study was to assess Salmonella carriage by pet reptiles in pet shops and households, and their role in the transmission of antimicrobial resistance, to inform the owners about the possible risks factors. During the period between January 2019 and December 2019, 54 reptiles from pet shops and 69 reptiles from households were sampled in the Valencian Region (Eastern Spain). Three different sample types were collected from each reptile: oral cavity, skin, and cloacal swabs. Salmonella identification was based on ISO 6579-1:2017 (Annex D), serotyped in accordance with Kauffman-White-Le-Minor technique, and antibiotic susceptibility was assessed according to Decision 2013/652. The results of this study showed that 48% of the pet reptiles examined from households and pet shops carry Salmonella spp. All the strains isolated presented resistance to at least one antibiotic, and 72% were multidrug-resistant strains, the most frequently observed resistance patterns being gentamicin-colistin and gentamicin-colistin-ampicillin. The present study demonstrates that pet reptiles could be a source of human multidrug-resistant Salmonella infection. In this context, the most optimal prevention of multidrug-resistant Salmonella infections necessarily involves strict control of the sanitary status of reptile pet shops and hygienic handling by the individual owners at home.

Impact of the COVID-19 pandemic on human salmonellosis in the Netherlands.

The public health measures implemented to control coronavirus disease 2019 (COVID-19) may influence also other infectious diseases. Using national laboratory surveillance data, we assessed the impact of the COVID-19 pandemic on human salmonellosis in the Netherlands until March 2021. Salmonellosis incidence decreased significantly after March 2020: in the second, third and fourth quarters of 2020, and in the first quarter of 2021, the incidence decreased by 55%, 57%, 47% and 37%, respectively, compared to the same quarters of 2016-2019. The decrease was strongest among travel-related cases (94%, 84%, 79% and 93% in the aforementioned quarters, respectively). Other significant changes were: increased proportion of cases among older adults and increased proportion of invasive infections, decreased proportion of trimethoprim resistance and increased proportion of serovar Typhimurium monophasic variant vs. Enteritidis. This led to decreased contributions of laying hens and increased contributions of pigs and cattle as sources of human infections. The observed changes probably reflect a combination of reduced exposure to Salmonella due to restrictions on international travels and gatherings, closure of dine-in restaurants, catering and hospitality sectors at large and changes in healthcare-seeking and diagnostic behaviours.

The challenging task to select Salmonella target serovars in poultry: the Italian point of view.

According to the European Food Safety Authority (EFSA) and European Centre for Disease Prevention and Control (ECDC) annual report, human salmonellosis is mostly related to consumption of contaminated poultry products. Since 2003 in Europe, the Salmonella serovars considered relevant for human health and subject to control in breeding hens of Gallus gallus are: S. Enteritidis, S. Typhimurium (including the monophasic variant), S. Infantis, S. Hadar and S. Virchow. Herein, we investigated the Italian epidemiological situation from 2016 to 2018, comparing Salmonella serovar distributions in humans and poultry, in order to identify the target Salmonella serovars that, if controlled, would potentially have the largest public health impact in Italy. The results showed that control of S. Virchow and S. Hadar does no longer seem to be a priority in Italy and that S. Napoli and S. Derby, which are not included in the group of EU target serovars, are among the most frequent serovars isolated from humans in Italy. While S. Derby has its main reservoir in pigs, S. Napoli does not have a specific reservoir. However, because this serovar is frequently isolated from breeding poultry flocks and is characterised by causing severe human illness, it is a potential target Salmonella serovar in breeding hens of Gallus gallus in Italy.

Edaphoclimatic seasonal trends and variations of the Salmonella spp. infection in Northwestern Mexico.

Currently, Salmonella spp. is the bacterium causing the highest number of food-borne diseases (FADs) in the world. It is primarily associated with contaminated water used to that irrigates crops from intensive livestock farming. However, literature emphasizes that the reservoirs for Salmonella spp. remain in wildlife and there are unconventional sources or secondary reservoirs, such as soil. Human soil-borne diseases have not been modeled in spatial scenarios, and therefore it is necessary to consider soil and other climatic factors to anticipate the emergence of new strains or serotypes with potential threat to public and animal health. The objective of this research was to investigate whether edaphic and climatic factors are associated with the occurrence and prevalence of Salmonella spp. in Northwestern Mexico. We estimated the potential distribution of Salmonella spp. with an interpolation method of unsampled kriging areas for 15 environmental variables, considering that these factors have a seasonal dynamic of change during the year and modifications in longer periods. Subsequently, a database was generated with human salmonellosis cases reported in the epidemiological bulletins of the National System of Epidemiological Surveillance (SIVE). For the Northwest region, there were 30,595 human cases of paratyphoid and other salmonellosis reported have been reported in Baja California state, 71,462 in Chihuahua, and 16,247 in Sonora from 2002 to 2019. The highest prevalence was identified in areas with higher temperatures between 35 and 37 °C, and precipitation greater than 1000 mm. The edaphic variables limited the prevalence and geographical distribution of Salmonella spp., because the region is characterized by presenting a low percentage of organic matter (≤4.3), and most of the territory is classified as aridic and xeric, which implies that the humidity comprises ≤ 180 days a year. Finally, the seasonal time series indicated that in the states of Baja California and Chihuahua the rainy quarter of the year is 18.7% and 17.01% above a typical quarter respectively, while for Sonora the warmest quarter is 23.3%. It is necessary to deepen the relationship between different soil characteristics and climate elements such as temperature and precipitation, which influence the distribution of different soil-transmitted diseases.

Prevalence and phenotypic characterization of Salmonella enterica isolates from three species of wild marine turtles in Grenada, West Indies.

Background and Aim:Salmonella enterica causes enteric disease in mammals and may potentially be transmitted from marine turtles that shed the pathogen in the environment. Marine turtle-associated human salmonellosis is a potential public health concern in Grenada, as the island supports populations of leatherback turtles (Dermochelys coriacea), hawksbill turtles (Eretmochelys imbricata), and green turtles (Chelonia mydas) that interface with veterinarians and conservation workers, the local population, and the thousands of visitors that frequent the island yearly. To date, the prevalence of S. enterica has only been examined in a small subset of marine turtles in the Caribbean and no studies have been conducted in Grenada. The aim of this study was to quantify the prevalence of S. enterica in leatherback, hawksbill and green turtles in Grenada, characterize phenotypes and DNA profiles, and explore the potential risk to human health in the region.Materials and Methods:A total of 102 cloacal swabs were obtained from nesting leatherback turtles and foraging hawksbill and green turtles. Samples were cultured on enrichment and selective media and isolates were phenotypically characterized using serotyping, pulsed-phase gel electrophoresis, and antibiotic susceptibility. Enrichment broths were additionally screened by polymerase chain reaction (PCR) using S. enterica-specific primers.Results:S. enterica was cultured from 15/57 (26.3%) leatherback turtles, 0/28 hawksbill, and 0/17 green turtles. This included S. enterica serovars Montevideo, S. I:4,5,12:i:-, Salmonella Typhimurium, Salmonella Newport, S. I:6,7:-:-, and S. I:4,5,12:-:-. Five/15 leatherback turtles carried multiple serovars. Eight pulsotype groups were identified with multiple clustering; however, there was no clear association between pulsotype group and serotype profile. Five/71 isolates showed resistance to streptomycin or ampicillin. Twenty-one/57 leatherback turtles, 14/28 hawksbill turtles, and 8/17 green turtles tested positive for S. enterica by quantitative PCR.Conclusion:Nesting leatherback turtles actively shed S. enterica and poses a risk for zoonosis; however, the presence of viable pathogen in green and hawksbill species is unclear. These findings help elucidate the role of marine turtles as potential sources of zoonotic S. enterica and provide baseline data for one health research in Grenada and the wider Caribbean region.

Abattoir-based study of Salmonella prevalence in pigs at slaughter in Great Britain

Abstract Consumption of pork and pork products can be associated with outbreaks of human salmonellosis. Salmonella infection is usually subclinical in pigs, and farm-based control measures are challenging to implement. To obtain data on Salmonella prevalence, samples can be collected from pigs during the slaughter process. Here we report the results of a Great Britain (GB) based abattoir survey conducted by sampling caecal contents from pigs in nine British pig abattoirs during 2019. Samples were collected according to a randomised stratified scheme, and pigs originating from 286 GB farms were included in this survey. Salmonella was isolated from 112 pig caecal samples; a prevalence of 32.2% [95% confidence interval (CI) 27.4–37.4]. Twelve different Salmonella serovars were isolated, with the most common serovars being S. 4,[5],12:i:-, a monophasic variant of Salmonella Typhimurium (36.6% of Salmonella-positive samples), followed by S. Derby (25.9% of Salmonella-positive samples). There was no significant difference compared to the estimate of overall prevalence (30.5% (95% CI 26.5–34.6)) obtained in the last abattoir survey conducted in the UK (2013). Abattoir-based control measures are often effective in the reduction of Salmonella contamination of carcasses entering the food chain. In this study, the effect of abattoir hygiene practices on the prevalence of Salmonella on carcasses was not assessed. Continuing Salmonella surveillance at slaughter is recommended to assess effect of farm-based and abattoir-based interventions and to monitor potential public health risk associated with consumption of Salmonella-contaminated pork products.

The influence of climate change on the spread of human salmonellosis (Mini-review)

Human salmonellosis is one of the most important food-borne diseases, which is caused by the serovars of Salmonella enterica. The mesophilic and hydrophilic bacteria, Salmonella serovars are expected to spread and cause an increased number of cases as a result of climate change. The interdependence of human salmonellosis and climate change is a complex phenomenon. Therefore, it needs a multidisciplinary method of analysis. Especially in low-income regions, both extreme weather events and diseases and their coexistence cause real disasters to the poorest communities. This review gathers the epidemiological and socioeconomic aspects of human salmonellosis to assess the main driving forces of infection. As a result, it was ascertained that the application of different disciplines helped to appreciate the important role of poverty in the epidemiology of human salmonellosis.

Accurate and Rapid Methods for Detecting Salmonella spp. Using Polymerase Chain Reaction and Aptamer Assay from Dairy Products: A Review

Salmonella spp. is the most common cause of gastrointestinal food poisoning worldwide, and human salmonellosis is mostly caused by the consumption of contaminated food. Therefore, the development of rapid detection methods for Salmoenlla spp. and rapid identification of the source of infection by subtyping are important for the surveillance and monitoring of food-borne salmonellosis. Therefore, this review introduces (1) History and nomenclature of Salmoenlla spp., (2) Epidemiology of Salmoenlla spp., (3) Detection methods for Salmoenlla spp. – conventional culture method, genetic detection method, molecular detection methods, and aptamer, and (4) Subtyping methods for Salmoenlla spp. – pulsed-field gel electrophoresis and repetitive sequence-based polymerase chain reaction (PCR).

Non-typhoidal human salmonellosis in Rio Grande do Sul, Brazil: A combined source attribution study of microbial subtyping and outbreak data

Salmonella spp. remains the most significant foodborne pathogen in south Brazil, but its epidemiology tends to change over time. Using official and surrogate data, a microbial subtyping model attributed different Salmonella serovars to laying hens, pigs, broilers, and turkeys from 2005 to 2015 in Rio Grande do Sul (RS). Additional to the subtyping model, three sub-analyses of outbreak data attributed Salmonella spp. in humans to animal and non-animal food. Laying hens/eggs was the most important source of human salmonellosis in RS, with almost 40% (159 cases; 95% credibility interval, 43–247) attribution proportion, followed by pigs reared in Santa Catarina, a neighbor state (34.5%). The Salmonella serovars Enteritidis and Typhimurium were the most common serovars involved. Source-related parameters had wide credibility intervals but showed a higher risk of illness from contaminated eggs than from the other three animal-food sources. Analysis of the outbreak data corroborated the findings and indicated signs of decreasing importance for eggs and increasing importance for pork consumption.

PCR identification of Salmonella serovars for the E serogroup based on novel specific targets obtained by pan-genome analysis

Accurate serotyping of Salmonella is essential for epidemiological investigations and surveillance of Salmonella infections. Compared to traditional methods, polymerase chain reaction (PCR) is more sensitive and identifies Salmonella to the serotype level. Few genes have been used as a target for PCR serotyping; thus, research to identify specific targets of common serotypes is needed. The Salmonella E serogroup contains multiple pathogenic serotypes that have been associated with recent cases of human salmonellosis. Thus, this study mined new molecular targets for rapid detection of the E serogroup of Salmonella serovars. Using pan-genome analysis and the online BLAST program, specific genes of Salmonella serovars Weltevreden, London, Meleagridis, and Senftenberg were obtained. Primer sets were evaluated by PCR using target strains, 41 nontarget Salmonella serotypes and 22 non-Salmonella strains. There were 11, 5, 5, and 1 genes specific to S. Weltevreden, S. London, S. Meleagridis, and S. Senftenberg, respectively, with detection limits as low as 102 or 103 CFU/mL per assay for pure culture. Moreover, the primer sets satisfactorily identified Salmonella serotypes in artificially contaminated foods. These results demonstrated that pan-genome analysis identified new specific targets, and PCR serotyping could be a primary screening method or a supplement to the classical detection method.

Chicken cecal DNA methylome alteration in the response to Salmonella enterica serovar Enteritidis inoculation

BackgroundSalmonella enterica serovar Enteritidis (SE) is one of the pathogenic bacteria, which affects poultry production and poses a severe threat to public health. Chicken meat and eggs are the main sources of human salmonellosis. DNA methylation is involved in regulatory processes including gene expression, chromatin structure and genomic imprinting. To understand the methylation regulation in the response to SE inoculation in chicken, the genome-wide DNA methylation profile following SE inoculation was analyzed through whole-genome bisulfite sequencing in the current study.ResultsThere were 185,362,463 clean reads and 126,098,724 unique reads in the control group, and 180,530,750 clean reads and 126,782,896 unique reads in the inoculated group. The methylation density in the gene body was higher than that in the upstream and downstream regions of the gene. There were 8946 differentially methylated genes (3639 hypo-methylated genes, 5307 hyper-methylated genes) obtained between inoculated and control groups. Methylated genes were mainly enriched in immune-related Gene Ontology (GO) terms and metabolic process terms. Cytokine-cytokine receptor interaction, TGF-beta signaling pathway, FoxO signaling pathway, Wnt signaling pathway and several metabolism-related pathways were significantly enriched. The density of differentially methylated cytosines in miRNAs was the highest. HOX genes were widely methylated.ConclusionsThe genome-wide DNA methylation profile in the response to SE inoculation in chicken was analyzed. SE inoculation promoted the DNA methylation in the chicken cecum and caused methylation alteration in immune- and metabolic- related genes. Wnt signal pathway, miRNAs and HOX gene family may play crucial roles in the methylation regulation of SE inoculation in chicken. The findings herein will deepen the understanding of epigenetic regulation in the response to SE inoculation in chicken.

Rapid detection of flagellated and non-flagellated Salmonella by targeting the common flagellar hook gene flgE.

Salmonella spp. can cause animal and human salmonellosis. In this study, we established a simple method to detect all Salmonella species by amplifying a specific region within the flgE gene encoding the flagellar hook protein. Our preliminary sequence analysis among flagella-associated genes of Salmonella revealed that although Salmonella Gallinarum and Salmonella Pullorum are lacking flagella, they did have flagella-associated genes, including flgE. To investigate in detail, a comparative flgE sequence analysis was conducted using different bacterial strains including flagellated and non-flagellated Salmonella as well as non-Salmonella strains. Two unique regions (481-529 bp and 721-775 bp of the reference sequence) within the flgE open reading frame were found to be highly conserved and specific to all Salmonella species. Next, we designed a pair of PCR primers (flgE-UP and flgE-LO) targeting the above two regions, and performed a flgE-tailored PCR using as template DNA prepared from a total of 76 bacterial strains (31 flagellated Salmonella strains, 26 non-flagellated Salmonella strains, and 19 other non-Salmonella bacteria strains). Results showed that specific positive bands with expected size were obtained from all Salmonella (including flagellated and non-flagellated Salmonella) strains, while no specific product was generated from non-Salmonella bacterial strains. PCR products from the positive bands were confirmed by DNA sequencing. The minimum detection amount for genomic DNA and bacteria cells reached 18.3 pg/μL and 100 colony-forming unit (CFU) per PCR reaction, respectively. Using the flgE-PCR method to detect Salmonella in artificially contaminated milk samples, as low as 1 CFU/mL Salmonella was detectable after an 8-h pre-culture. Meanwhile, the flgE-tailored PCR method was applied to evaluate 247 clinical samples infected with Salmonella from different chicken breeding farms. The detection results indicated that flgE-PCR could be used to specifically detect Salmonella in concordance with the traditional bacterial culture-based detection method. It is worthwhile noticed that identification results using flgE-tailored PCR should be completed within less than 1 day, expanding the result of much faster than the standard method, which took more than 5 days. Overall, the flgE-tailored PCR method can specifically detect flagellated and non-flagellated Salmonella and can serve as a powerful tool for rapid, simple, and sensitive detection of Salmonella species. KEY POINTS : • Targeting flgE gene for all Salmonella spp. found. • The established PCR assay is used to specifically detect all Salmonella spp. • The PCR method is applied to detect clinical Salmonella spp. samples within less than 1 day.

Characterization of Multidrug Resistance Patterns of Emerging Salmonella enterica Serovar Rissen along the Food Chain in China.

Salmonella spp. are recognized as important foodborne pathogens globally. Salmonella enterica serovar Rissen is one of the important Salmonella serovars linked with swine products in numerous countries and can transmit to humans by food chain contamination. Worldwide emerging S. Rissen is considered as one of the most common pathogens to cause human salmonellosis. The objective of this study was to determine the antimicrobial resistance properties and patterns of Salmonella Rissen isolates obtained from humans, animals, animal-derived food products, and the environment in China. Between 2016 and 2019, a total of 311 S. Rissen isolates from different provinces or province-level cities in China were included here. Bacterial isolates were characterized by serotyping and antimicrobial susceptibility testing. Minimum inhibitory concentration (MIC) values of 14 clinically relevant antimicrobials were obtained by broth microdilution method. S. Rissen isolates from humans were found dominant (67%; 208/311). S. Rissen isolates obtained from human patients were mostly found with diarrhea. Other S. Rissen isolates were acquired from food (22%; 69/311), animals (8%; 25/311), and the environment (3%; 9/311). Most of the isolates were resistant to tetracycline, trimethoprim-sulfamethoxazole, chloramphenicol, streptomycin, sulfisoxazole, and ampicillin. The S. Rissen isolates showed susceptibility against ceftriaxone, ceftiofur, gentamicin, nalidixic acid, ciprofloxacin, and azithromycin. In total, 92% of the S. Rissen isolates were multidrug-resistant and ASSuT (27%), ACT (25%), ACSSuT (22%), ACSSuTAmc (11%), and ACSSuTFox (7%) patterns were among the most prevalent antibiotic resistance patterns found in this study. The widespread dissemination of antimicrobial resistance could have emerged from misuse of antimicrobial agents in animal husbandry in China. These findings could be useful for rational antimicrobial usage against Salmonella Rissen infections.

ROmpF and OMVs as efficient subunit vaccines against Salmonella enterica serovar Enteritidis infections in poultry farms

Salmonella enterica serovar Enteritidis remains the most prevalent serotype causing human salmonellosis through the consumption of contaminated foods, especially poultry products. The development of a subunit vaccine against S. Enteritidis can not only protect chickens against Salmonella infection in the poultry industry but also cut the transmission sources. In this study, both the expressed recombinant outer membrane protein F (rOmpF) and extracted outer membrane vesicles (OMVs) were developed as subunit vaccines against S. Enteritidis challenge in chickens. Immunization with the subunit vaccine could induce not only antibody production but also strong cell-mediated immune response. Both rOmpF plus QuilA adjuvant and OMVs alone had highly protective efficacy against S. Enteritidis challenge and rapidly decreased the colonization of bacteria in chicken. These findings revealed the potential application of rOmpF and OMVs as subunit vaccines in the poultry industry.

Research of Salmonella spp. in mozzarella in the city of Belo Horizonte

Bacteria of the genus Salmonella are pathogens that cause salmonellosis in humans, a food infection caused by the consumption of food contaminated by the bacteria, this can occur due to the absence of hygiene practices in the milk production process, non-existent or improper refrigeration, absence of processes thermal or improperly, unqualified labor may also be present on poorly sanitized surfaces that come into contact with food. As these situations are commonly found in small and medium rural properties, the objective of this research was to analyze the presence of Salmonella spp. in Mozzarella cheese under different types of processing, sold in the retail area of the metropolitan region of Belo Horizonte, in addition to assessing the influence of manufacturing technology on the identity and quality of the cheese in question, as a way of guaranteeing the health and well-being of the potentially consuming human population.

Combining quantitative and qualitative approaches to determine viability of a potential Salmonella Typhimurium vaccination program in pigs in Belgium

Vaccinating pigs against Salmonella Typhimurium (ST) might be a way to control ST infections at farm level and reduce human infections. Two main issues have to be addressed before such a mandatory vaccination program can be implemented: the effective reduction of attributable human incidence has to be demonstrated and all socio-economic barriers impacting the attitude and motivation of the pig sector have to be lifted.The present research used a quantitative microbial risk assessment model to estimate the effect of different hypothetical Salmonella spp. and ST mitigation strategies on the annual prevalence of human salmonellosis along the minced pork production chain. In addition, a qualitative study aimed to list the potential concerns of the pig sector about the implementation of a hypothetical future vaccination program.The following themes were the most often mentioned: awareness, vaccine cost-benefit/effectiveness, legislation, monovalent vaccine, time and labour required to vaccinate, vaccine registration and trade restriction. Cost-effectiveness and cost-benefit of vaccination were cited by all the key interviewees (n = 12). However, based on the quantitative microbial risk assessment model, vaccination alone may not be sufficiently effective to reduce the annual human salmonellosis prevalence. A combination of different control measures along the food chain, with a special focus on interventions at the slaughterhouse, might be more effective in achieving the desired goal than vaccination alone.

Retrospective cost-utility analysis of the Non-typhoidal Salmonella control programme in Hungary

Salmonellosis is one of the most important foodborne infections in the European Union (EU), causing more than 90,000 human salmonellosis cases with an overall economic burden of 3 billion Euro annually (EFSA, 2014). Salmonella enterica serovar Enteritidis (S. Enteritidis or SE) and Salmonella enterica serovar Typhimurium (S. Typhimurium or ST) are the most pathogenic serotypes, also the most frequently reported serovars in humans in the EU. To fight against zoonotic diseases, including Salmonella, the EU established an extended control programme (Regulation (EC) No 2160/2003) that was launched in 2007. The cost-effectiveness of the control programme has not been examined at EU-level and there are only a limited number of national assessments available in the subject. The authors of the present paper conducted a retrospective cost-utility analysis of the Hungarian Salmonella Control Programme (HSCP) for the years 2007–2017. Costs and outcomes were considered from the state's perspective. Country-specific cost of illness estimates and a quality-adjusted life year (QALY) -based burden estimate have been developed for human salmonellosis cases. The programme's results were compared to a reference arm where incidence, hospitalization and mortality rates were extrapolated after 2007 by adjusting for the slight annual changes in population demographics, as if no control measures had been introduced in Hungary. The incremental cost-effectiveness ratio (ICER) was calculated and compared to the national health technology assessment (HTA) threshold, defined as 3xGDP per capita (EMMI, 2017). Since the calculated ICER value (27,150 EUR/QALY gain) was below the threshold (35,790 EUR/QALY gain), the HSCP was found to be cost-effective for the investigated time period. The analysis can serve as a model to carry out further analyses in relation to other pathogens or interventions and help the priority setting and decision-making processes of food safety in Hungary. Further discussion is needed on methodological questions, such as the perspective of the analysis or the inclusion or exclusion of various cost types.

Antimicrobial Resistance and Biofilm Formation Capacity of Salmonella enterica Serovar Enteritidis Strains Isolated from Poultry and Humans in Poland.

Salmonella enterica ser. Enteritidis (S. enterica ser. Enteritidis) is the most frequently detected serovar in human salmonellosis, and its ability to produce a biofilm and the risk of transmission from animals and food of animal origin to humans are significant. The main aim of the present work was to compare S. enterica ser. Enteritidis strains isolated from poultry and human feces in terms of resistance profiles, prevalence of selected resistance genes, and their potential for biofilm formation, by assessing their biofilm growth intensity, the prevalence and expression of selected genes associated with this phenomenon, and the correlation between increased antimicrobial resistance and biofilm formation ability of the two tested groups of S. enterica ser. Enteritidis. This study showed a difference in antimicrobial resistance (minimal inhibitory concentration value) between S. enterica ser. Enteritidis groups; however, the majority of multidrug-resistant (MDR) strains were isolated from poultry (environmental samples from chicken broilers, turkey broilers, and laying hens). Differences in the prevalence of resistance genes were observed; the most common gene among poultry strains was floR, and that among strains from humans was blaTEM. S. enterica ser. Enteritidis strains isolated from poultry under the tested incubation conditions exhibited better biofilm growth than strains isolated from humans. A higher level of gene expression associated with the production of cellulose was only detected in the S48 strain isolated from poultry. On the other hand, increased expression of genes associated with quorum sensing was observed in two strains isolated from poultry farms and one strain isolated from human feces.

Iron-Uptake Systems of Chicken-Associated Salmonella Serovars and Their Role in Colonizing the Avian Host

Iron is an essential micronutrient for most bacteria. Salmonella enterica strains, representing human and animal pathogens, have adopted several mechanisms to sequester iron from the environment depending on availability and source. Chickens act as a major reservoir for Salmonella enterica strains which can lead to outbreaks of human salmonellosis. In this review article we summarize the current understanding of the contribution of iron-uptake systems to the virulence of non-typhoidal S. enterica strains in colonizing chickens. We aim to address the gap in knowledge in this field, to help understand and define the interactions between S. enterica and these important hosts, in comparison to mammalian models.

Characterization of Salmonella Frintrop isolated from dromedary camels ( Camelus dromedarius )

Different studies have reported the prevalence and antibiotic resistance of Salmonella in dromedary camels and its role in camelid-associated salmonellosis in humans, but little is known about the epidemiology of Campylobacter in dromedaries. Here, we investigate the prevalence, genetic diversity and antibiotic resistance of Campylobacter and Salmonella in dromedary camels (Camelus dromedarius). A total of 54 individuals were sampled from two different dromedary farms located in Tenerife (Canary Islands, Spain). While all the samples were Campylobacter-negative, Salmonella prevalence was 5.5% (3/54), and the only serovar isolated was S.Frintrop. Pulsed-field gel electrophoresis analysis revealed a low genetic diversity, with all isolates showing a nearly identical pulsotype (similarity >95%). Our results indicate that dromedary camels could not be a risk factor for Campylobacter human infection, but seems to be a reservoir for Salmonella transmission. Since camel riding has become one of the main touristic attractions in several countries, and its popularity has increased considerably in recent years, a mandatory control, especially for zoonotic pathogens such as Campylobacter and Salmonella, should be implemented.