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Applied and Environmental Microbiology Nov 2021Enteric pathogens, including Salmonella, are capable of long-term survival after desiccation and resist heat treatments that are lethal to hydrated cells. The mechanisms...
Enteric pathogens, including Salmonella, are capable of long-term survival after desiccation and resist heat treatments that are lethal to hydrated cells. The mechanisms of dry-heat resistance differ from those of wet-heat resistance. To elucidate the mechanisms of dry-heat resistance in Salmonella, screening of the dry-heat resistance of 108 Salmonella strains, representing 39 serotypes, identified the 22 most resistant and the 8 most sensitive strains for comparative genome analysis. A total of 289 genes of the accessory genome were differently distributed between resistant and sensitive strains. Among these genes, 28 proteins with a putative relationship to stress resistance were selected for to quantify relative gene expression before and after desiccation and expression by solid-state cultures on agar plates relative to cultures growing in liquid culture media. Of these 28 genes, 15 genes were upregulated (0.05) after desiccation or by solid-state cultures on agar plates. These 15 genes were cloned into the low-copy-number vector pRK767 under the control of the promoter. The expression of 6 of these 15 genes increased (0.05) resistance to dry heat and to treatment with pressure of 500 MPa. Our finding extends the knowledge of mechanisms of stress resistance in desiccated Salmonella to improve control of this bacterium in dry food. This study directly targeted an increasing threat to food safety and developed knowledge and targeted strategies that can be used by the food industry to help reduce the risk of foodborne illness in their dry products and thereby reduce the overall burden of foodborne illness. Genomic and physiological analyses have elucidated mechanisms of bacterial resistance to many food preservation technologies, including heat, pressure, disinfection chemicals, and UV light; however, information on bacterial mechanisms of resistance to dry heat is scarce. Mechanisms of tolerance to desiccation likely also contribute to resistance to dry heat, but this assumption has not been verified experimentally. It remains unclear how mechanisms of resistance to wet heat relate to dry-heat resistance. Thus, this study will fill a knowledge gap to improve the safety of dry foods.
Topics: Agar; Desiccation; Gene Expression Regulation, Bacterial; Salmonella enterica; Stress, Physiological
PubMed: 34586905
DOI: 10.1128/AEM.01683-21 -
Pathogens and Global Health Jan 2014Importing day-old ducklings (DOD) unknowingly infected with non-typhoid Salmonella (NTS) may be associated with disease risk. Domestic and international trade may...
Importing day-old ducklings (DOD) unknowingly infected with non-typhoid Salmonella (NTS) may be associated with disease risk. Domestic and international trade may enhance this risk. Salmonella enterica serovars, their virulence genes combinations and antibiotic resistance, garner attention for their potentiality to contribute to the adverse health effects on populations throughout the world. The aim of this study was to estimate the risk of imported versus domestic DOD as potential carriers of NTS. The results confirm the prevalence of salmonellosis in imported ducklings was 18·5% (25/135), whereas only 12% (9/75) of cases were determined in the domestic ducklings. Fourteen serovars (Salmonella enteritidis, Salmonella kisii, Salmonella typhimurium, Salmonella gaillac, Salmonella uno, Salmonella eingedi, Salmonella shubra, Salmonella bardo, Salmonella inganda, Salmonella kentucky, Salmonella stanley, Salmonella virchow, Salmonella haifa, and Salmonella anatum) were isolated from the imported ducklings, whereas only S. enteritidis, S. typhimurium, S. virchow, and S. shubra were isolated from the domestic ducklings. The isolated Salmonella serovars were 100% susceptible to only colistin sulphate and 100% resistant to lincomycin. The 14 Salmonella serovars were screened for 11 virulence genes (invA, avrA, ssaQ, mgtC, siiD, sopB, gipA, sodC1, sopE1, spvC, and bcfC) by PCR. The invA, sopB, and bcfC genes were detected in 100% of the Salmonella serovars; alternatively, the gipA gene was absent in all of the isolated Salmonella serovars. The 11 virulent genes were not detected in either of S. stanley or S. haifa serovars. The results confirm an association between antibiotic resistance and virulence of Salmonella in the DOD. This study confirms the need for a country adherence to strict public health and food safety regimes.
Topics: Animals; Animals, Domestic; Animals, Newborn; Bacteriophage Typing; Drug Resistance, Bacterial; Ducks; Egypt; Feces; Meat Products; Polymerase Chain Reaction; Public Health; Salmonella Infections, Animal; Salmonella enterica; Serotyping; Virulence Factors
PubMed: 24548159
DOI: 10.1179/2047773213Y.0000000118 -
Applied and Environmental Microbiology Aug 2019serovar Heidelberg is currently the 12th most common serovar of causing salmonellosis in the United States and results in twice the average incidence of blood...
serovar Heidelberg is currently the 12th most common serovar of causing salmonellosis in the United States and results in twice the average incidence of blood infections caused by nontyphoidal salmonellae. Multiple outbreaks of salmonellosis caused by Heidelberg resulted from the same poultry processor, which infected 634 people during 2013 and 2014. The hospitalization and invasive illness rates were 38% and 15%, respectively. We hypothesized that the outbreak strains of Heidelberg had enhanced stress tolerance and virulence capabilities. We sourced nine food isolates collected during the outbreak investigation and three reference isolates to assess their tolerance to heat and sanitizers, ability to attach to abiotic surfaces, and invasiveness We performed RNA sequencing on three isolates (two outbreak-associated isolates and a reference Heidelberg strain) with various levels of heat tolerance to gain insight into the mechanism behind the isolates' enhanced heat tolerance. We also performed genomic analyses to determine the genetic relationships among the outbreak isolates. Ultimately, we determined that (i) six Heidelberg isolates associated with the foodborne outbreak had enhanced heat tolerance, (ii) one outbreak isolate with enhanced heat tolerance also had an enhanced biofilm-forming ability under stressful conditions, (iii) exposure to heat stress increased the expression of Heidelberg multidrug efflux and virulence genes, and (iv) outbreak-associated isolates were likely transcriptionally primed to better survive processing stresses and, potentially, to cause illness. This study provides a deep analysis of the intrinsic stress tolerance and virulence capabilities of Heidelberg that may have contributed to the length and severity of a recent salmonellosis outbreak. Additionally, this study provides a comprehensive analysis of the transcriptomic response of strains to heat stress conditions and compares baseline stationary-phase gene expression among outbreak- and non-outbreak-associated Heidelberg isolates. These data can be used in assay development to screen isolates for stress tolerance and subsequent survival. This study adds to our understanding of the strains associated with the outbreak and informs ongoing regulatory discussions on in poultry.
Topics: Bacterial Proteins; Humans; Salmonella Food Poisoning; Salmonella Infections; Salmonella enterica; Stress, Physiological; United States
PubMed: 31175193
DOI: 10.1128/AEM.01065-19 -
BMC Microbiology Jul 2015This study investigated the prevalence, serotypes and antimicrobial sensitivity patterns of Salmonella enterica in environment in Ouagadougou, Burkina Faso. A total of...
BACKGROUND
This study investigated the prevalence, serotypes and antimicrobial sensitivity patterns of Salmonella enterica in environment in Ouagadougou, Burkina Faso. A total of 476 samples, consisting of 36 samples of tap water, 51 samples of well water, 87 samples of channel water, 44 samples of reservoir water, 238 samples of fish, and 20 samples of lettuce were examined using standard bacteriological procedures for Salmonella.
RESULTS
Salmonella were isolated from 98 samples. Salmonella were rare in drinking water, since they were not found at all from the tap water, and only in 2 % of well water. Salmonella were more common in the water of reservoir of Tanghin (15 %), reservoir of Yamtenga (20 %), and in the water channels in the city (from 20 to 31 %). Salmonella were commonly isolated from the fish (24 %) caught from the reservoir of Tanghin and from the lettuce (50 %) irrigated with water from Tanghin. The Salmonella isolates were found to represent 50 different serotypes. The 11 most common serotypes were Salmonella Bredeney and S. Colindale (both 8.2 %), S. Muenster (6.1 %), S. Korlebu (5.1 %), S. Eastbourne and S. Poona (both 4.1 %), and S. Agona, S. Derby, S. Drac, S. Senftenberg, S. Waycross (each 3.1 %), accounting for 51.3 % of all the isolates. In general, the Salmonella strains were sensitive to the antimicrobials tested, but two strains were resistant to streptomycin and many more intermediate to streptomycin or sulphonamide.
CONCLUSION
This study highlights the common prevalence of Salmonella and the high diversity of Salmonella serotypes in aquatic environment in Ouagadougou, Burkina Faso. Therefore, various human activities linked to water and consumption of water-related products, such as fish and lettuce, can lead to human Salmonella infections.
Topics: Animals; Anti-Bacterial Agents; Burkina Faso; Drug Resistance, Bacterial; Fishes; Fresh Water; Lactuca; Microbial Sensitivity Tests; Prevalence; Salmonella enterica; Serogroup
PubMed: 26228572
DOI: 10.1186/s12866-015-0484-7 -
Microbial Genomics Oct 2021Non-typhoidal is an important gastrointestinal pathogen causing a considerable burden of disease. Resistance to third generation cephalosporins poses a serious threat...
Non-typhoidal is an important gastrointestinal pathogen causing a considerable burden of disease. Resistance to third generation cephalosporins poses a serious threat for treatment of severe infections. In this study occurrence, phylogenetic relationship, and mechanisms of third generation cephalosporin resistance were investigated for clinical non-typhoidal isolates in Germany. From 2017 to 2019, we detected 168 unique clinical isolates with phenotypic resistance to third generation cephalosporins in a nation-wide surveillance. Compared to previous years, we observed a significant (=0.0002) and consistent increase in resistant isolates from 0.41 % in 2005 to 1.71 % in 2019. In total, 34 different serovars were identified, most often . Infantis (=41; 24.4 %), . Typhimurium (=27; 16.1 %), . Kentucky (=21; 12.5 %), and . Derby (=17; 10.1 %). Whole genome analyses revealed extended-spectrum β-lactamase (ESBL) genes as main cause for third generation cephalosporin resistance, and most prevalent were (=55), (=25), and (=23). There was no strict correlation between serovar, phylogenetic lineage, and ESBL type but some serovar/ESBL gene combinations were detected frequently, such as and in . Infantis or in . Kentucky. The ESBL genes were mainly located on plasmids, including IncI, IncA/C variants, emerging pESI variants, and a novel harbouring plasmid. We conclude that third generation cephalosporin resistance is on the rise among clinical isolates in Germany, and occurrence in various serovars is most probably due to multiple acquisition events of plasmids.
Topics: Anti-Bacterial Agents; Cephalosporin Resistance; Cephalosporins; Drug Resistance, Multiple, Bacterial; Germany; Humans; Microbial Sensitivity Tests; Phylogeny; Plasmids; Salmonella enterica; Serogroup; beta-Lactamases
PubMed: 34693903
DOI: 10.1099/mgen.0.000698 -
International Journal of Food... May 2021Our previous study demonstrated that whole genome sequencing (WGS) data generated by Oxford Nanopore Technologies (ONT) can be used for rapid and accurate prediction of...
Our previous study demonstrated that whole genome sequencing (WGS) data generated by Oxford Nanopore Technologies (ONT) can be used for rapid and accurate prediction of selected Salmonella serotypes. However, one limitation is that established methods for WGS-based serotype prediction, utilizing data from either ONT or Illumina, cannot differentiate certain serotypes and serotype variants with the same or closely related antigenic formulae. This study aimed to evaluate nanopore sequencing and additional data analysis for identification of Salmonella enterica Choleraesuis var. Kunzendorf and S. enterica Orion var. 15, 34, thus overcoming this limitation. Five workflows that combined different flow cells, library construction methods and basecaller models were evaluated and compared. The workflow that consisted of the R9 flow cell, rapid sequencing library construction kit and guppy basecaller with base modified model performed best for Single Nucleotide Polymorphism (SNP) analysis. With this workflow, 99.98% of matching identity between assembled genomes from ONT and that from Illumina was achieved. Less than five high-quality SNPs differed when comparing sequencing data between ONT and Illumina. SNP typing successfully identified Choleraesuis var. Kunzendorf. While prophage prediction further differentiated Orion var. 15, 34 from the other two Orion variants. Our study improves the readiness of ONT as a Salmonella subtyping and source tracking tool for food industry applications.
Topics: Bacterial Typing Techniques; High-Throughput Nucleotide Sequencing; Nanopore Sequencing; Polymorphism, Single Nucleotide; Salmonella enterica
PubMed: 33774575
DOI: 10.1016/j.ijfoodmicro.2021.109167 -
BMC Evolutionary Biology Jun 2019The emergence of antimicrobial-resistant (AMR) strains of the important human and animal pathogen Salmonella enterica poses a growing threat to public health. Here, we...
BACKGROUND
The emergence of antimicrobial-resistant (AMR) strains of the important human and animal pathogen Salmonella enterica poses a growing threat to public health. Here, we studied the genome-wide evolution of 90 S. enterica AMR isolates, representing one host adapted serotype (S. Dublin) and two broad host range serotypes (S. Newport and S. Typhimurium).
RESULTS
AMR S. Typhimurium had a large effective population size, a large and diverse genome, AMR profiles with high diversity, and frequent positive selection and homologous recombination. AMR S. Newport showed a relatively low level of diversity and a relatively clonal population structure. AMR S. Dublin showed evidence for a recent population bottleneck, and the genomes were characterized by a larger number of genes and gene ontology terms specifically absent from this serotype and a significantly higher number of pseudogenes as compared to other two serotypes. Approximately 50% of accessory genes, including specific AMR and putative prophage genes, were significantly over- or under-represented in a given serotype. Approximately 65% of the core genes showed phylogenetic clustering by serotype, including the AMR gene aac (6')-Iaa. While cell surface proteins were shown to be the main target of positive selection, some proteins with possible functions in AMR and virulence also showed evidence for positive selection. Homologous recombination mainly acted on prophage-associated proteins.
CONCLUSIONS
Our data indicates a strong association between genome content of S. enterica and serotype. Evolutionary patterns observed in S. Typhimurium are consistent with multiple emergence events of AMR strains and/or ecological success of this serotype in different hosts or habitats. Evolutionary patterns of S. Newport suggested that antimicrobial resistance emerged in one single lineage, Lineage IIC. A recent population bottleneck and genome decay observed in AMR S. Dublin are congruent with its narrow host range. Finally, our results suggest the potentially important role of positive selection in the evolution of antimicrobial resistance, host adaptation and serotype diversification in S. enterica.
Topics: Anti-Bacterial Agents; Evolution, Molecular; Humans; Phylogeny; Salmonella enterica; Serogroup
PubMed: 31226931
DOI: 10.1186/s12862-019-1457-5 -
Clinical Microbiology Reviews Apr 2004Nontyphoid Salmonella strains are important causes of reportable food-borne infection. Among more than 2,000 serotypes, Salmonella enterica serotype Choleraesuis shows... (Review)
Review
Nontyphoid Salmonella strains are important causes of reportable food-borne infection. Among more than 2,000 serotypes, Salmonella enterica serotype Choleraesuis shows the highest predilection to cause systemic infections in humans. The most feared complication of serotype Cholearesuis bacteremia in adults is the development of mycotic aneurysm, which previously was almost uniformally fatal. The advances in diagnostic techniques, surgical care, and antimicrobial therapy have greatly improved the survival of these patients. However, the recent emergence of serotype Choleraesuis that is resistant to ampicillin, chloramphenicol, trimethoprim-sulfamethoxazole, and, notably, fluoroquinolone antibiotics has aroused concern about the use of these agents for the empirical treatment of systemic infection caused by this organism. In view of the serious implications of the situation, the chain of transmission and mechanism of resistance should be carefully studied to reduce the spread of infection and threat to human health. To date, there are no vaccines available to prevent serotype Choleraesuis infections in humans. The availability, in the near future, of the genome sequence of serotype Cholearesuis will facilitate the development of effective vaccines as well as the discovery of new targets for novel antimicrobial agents.
Topics: Anti-Bacterial Agents; Drug Resistance, Bacterial; Humans; Salmonella Infections; Salmonella Vaccines; Salmonella enterica; Serotyping; Virulence
PubMed: 15084503
DOI: 10.1128/CMR.17.2.311-322.2004 -
Antimicrobial Agents and Chemotherapy May 2015Salmonella enterica is one of the most common causes of bacterial foodborne illness in the United States. Although most Salmonella infections are self-limiting,...
Salmonella enterica is one of the most common causes of bacterial foodborne illness in the United States. Although most Salmonella infections are self-limiting, antimicrobial treatment of invasive salmonellosis is critical. The primary antimicrobial treatment options include fluoroquinolones or extended-spectrum cephalosporins, and resistance to these antimicrobial drugs may complicate treatment. At present, S. enterica is composed of more than 2,600 unique serotypes, which vary greatly in geographic prevalence, ecological niche, and the ability to cause human disease, and it is important to understand and mitigate the source of human infection, particularly when antimicrobial resistance is found. In this study, we identified and characterized 19 S. enterica serotype Albert isolates collected from food animals, retail meat, and humans in the United States during 2005 to 2013. All five isolates from nonhuman sources were obtained from turkeys or ground turkey, and epidemiologic data suggest poultry consumption or live-poultry exposure as the probable source of infection. S. enterica serotype Albert also appears to be geographically localized to the midwestern United States. All 19 isolates displayed multidrug resistance, including decreased susceptibility to fluoroquinolones and resistance to extended-spectrum cephalosporins. Turkeys are a likely source of multidrug-resistant S. enterica serotype Albert, and circulation of resistance plasmids, as opposed to the expansion of a single resistant strain, is playing a role. More work is needed to understand why these resistance plasmids spread and how their presence and the serotype they reside in contribute to human disease.
Topics: Anti-Bacterial Agents; Drug Resistance, Multiple, Bacterial; Humans; Midwestern United States; Phylogeny; Salmonella enterica; Serogroup
PubMed: 25733501
DOI: 10.1128/AAC.05183-14 -
Applied and Environmental Microbiology Jan 2019Under stressful conditions, forms multinucleated elongated filaments. The triggers and outcomes of filamentation are not well characterized. serotypes Newport,...
Under stressful conditions, forms multinucleated elongated filaments. The triggers and outcomes of filamentation are not well characterized. serotypes Newport, Javiana, and Typhimurium were evaluated for their ability to form filaments upon exposure to 20 mM pelargonic acid. Newport was used as a model to investigate the progression and fate of filamentation via culturable population size, cell length, and viability assays. All serotypes displayed filament formation after 16 h of incubation. Pelargonic acid amendment of tryptic soy broth (TSBpel) produced a 5-log CFU reduction compared to TSB after 24 h (0.05), and the growth rate decreased (0.02). Cell elongation started within 12 h, peaked at 16 h, and was followed by filament disintegration at 20 to 24 h. The ratio of filaments to regular-sized cells (F/R) in TSBpel was 3.87 ± 0.59 at 16 h, decreasing to 0.23 ± 0.04 and 0.03 ± 0.01 (0.05) at 20 and 24 h, respectively. Mg supplementation repressed filamentation (F/R = 0.25 ± 0.11) and enhanced culturable cell counts (0.05). Continued exposure to pelargonic acid inhibited growth in TSB and M9 compared to that in unamended media (0.05). However, in M9 medium without Mg amended with 20 mM pelargonic acid (M9pel), filament fragmentation progressed independently of pelargonic acid or Mg When cells were pretreated with pelargonic acid to induce filamentation and then transferred to fresh medium, a positive effect of Mg was noted under nutrient-deficient conditions, with higher live/dead cell ratios in M9 supplemented with 5 mM Mg (M9Mg) than in M9 (0.05). No change was observed when pelargonic acid was also added. Filamentation was ubiquitous in all serotypes tested, transient, and sensitive to Mg Fragmentation, but not recovery, progressed irrespective of antimicrobial or Mg presence. Some bacteria form elongated multinucleated structures, or filaments, when exposed to stress. The filamentous form of foodborne bacterial pathogens can interfere with food protection practices and diagnostic testing. Filamentation in Newport was investigated in response to pelargonic acid, a compound naturally found in several fruit and vegetables, and also used commercially as an herbicide. readily formed filaments when exposed to pelargonic acid. Filaments were not stable, however, and fragmented to individual cells even when the fatty acid was still present, recovering fully when the stress was alleviated. A deeper exploration of the molecular mechanisms regulating filamentation and the conditions that induce it in agriculture and the food supply chain is needed to devise strategies that curb this response.
Topics: Fatty Acids; Salmonella enterica; Serogroup; Stress, Physiological
PubMed: 30446555
DOI: 10.1128/AEM.02191-18