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1.
PLoS Negl Trop Dis ; 14(2): e0007875, 2020 02.
Artigo em Inglês | MEDLINE | ID: mdl-32084128

RESUMO

BACKGROUND: Clinical observations and animal studies have suggested that Salmonella intestinal carriage is promoted by concurrent Schistosoma infection. The present study assessed association of Salmonella intestinal carriage and Schistosoma mansoni infection among individuals in a Schistosoma endemic area in sub-Saharan Africa. METHODS: From November 2015 to March 2016, a cross-sectional community-wide study was conducted in Kifua II, a rural village in Kongo Central Province, Democratic Republic of Congo. Stool samples were collected and analyzed for Salmonella intestinal carriage (culture) and Schistosoma mansoni infection (Kato Katz microscopy with determination of egg load). Salmonella Typhimurium and Enteritidis isolates were assessed for genetic similarity with blood culture isolates obtained during the same period in a neighboring hospital using multi-locus variable-numbers tandem repeat analysis (MLVA). RESULTS: A total of 1,108 participants were included (median age 15 years (IQR: 7-36), male-to-female ratio of 1:1.1). The overall prevalence of Schistosoma mansoni infection and non-typhoidal Salmonella carriage was 51.2% (95% CI: 48.2-54.1) and 3.4% (95% CI: 2.5-4.7) respectively, with 2.2% (95% CI: 1.5-3.2) of participants coinfected. The proportion of Salmonella carriage tended to be higher among Schistosoma mansoni infected participants compared to non-infected participants but this difference did not reach statistical significance (4.2% versus 2.6%, p = 0.132). However, the proportion of Salmonella carriage among participants with a heavy Schistosoma mansoni infection was significantly higher compared to those with a light and moderate infection (8.7% versus 3.2%, p = 0.012) and compared to Schistosoma mansoni negatives (8.7% versus 2.6%, p = 0.002). The 38 Salmonella isolates comprised five and four Enteritidis and Typhimurium serotypes respectively, the majority of them had MLVA types identical or similar to those observed among blood culture isolates. CONCLUSION: Salmonella intestinal carriage was associated with a heavy intensity of Schistosoma mansoni infection. Further studies are needed to address causation.


Assuntos
Portador Sadio/microbiologia , Intestinos/microbiologia , Salmonella typhimurium/isolamento & purificação , Esquistossomose mansoni/parasitologia , Adolescente , Adulto , Animais , Portador Sadio/epidemiologia , Criança , Coinfecção/epidemiologia , Coinfecção/microbiologia , Coinfecção/parasitologia , Estudos Transversais , República Democrática do Congo/epidemiologia , Feminino , Humanos , Masculino , População Rural , Salmonella typhimurium/genética , Schistosoma mansoni/genética , Schistosoma mansoni/isolamento & purificação , Schistosoma mansoni/fisiologia , Esquistossomose mansoni/epidemiologia , Adulto Jovem
2.
Emerg Microbes Infect ; 9(1): 1-4, 2020.
Artigo em Inglês | MEDLINE | ID: mdl-31859589

RESUMO

CRISPR-based typing was performed to subtype isolates of S. Typhimurium and its monophasic variant Salmonella 4,[5],12:i:- from humans and animals between 2009 and 2017 in China. CRISPR typing classified all isolates into two lineages and four sub-lineages. All isolates from Lineage II and Lineage IB-1 were Salmonella Typhimurium. All of Salmonella 4,[5],12:i: - isolates were distributed in Lineage IA and Lineage IB-2, which all belonged to ST34 by MLST typing. Only Lineage IB-2 contained ST34 isolates from both Salmonella Typhimurium and Salmonella 4,[5],12:i:-. Among the isolates of ST34, TST4 was identified as the most common CRISPR type representing 86.5% of Salmonella 4,[5],12:i:- and 14.5 % of Salmonella Typhimurium mainly from pigs and humans. This study demonstrated that TST4-ST34 isolates were predominant in Salmonella 4,[5],12:i:-, and pig was the main reservoir for Salmonella 4,[5],12:i:- in China, which might have the potential to transmit to humans by pig production.


Assuntos
Repetições Palindrômicas Curtas Agrupadas e Regularmente Espaçadas , Reservatórios de Doenças , Técnicas de Genotipagem/métodos , Carne/microbiologia , Salmonella typhimurium/classificação , Salmonella typhimurium/isolamento & purificação , Sus scrofa , Animais , China , Diarreia/microbiologia , Eletroforese em Gel de Campo Pulsado , Humanos , Tipagem de Sequências Multilocus , Filogenia , Infecções por Salmonella/microbiologia , Salmonella typhimurium/genética
3.
Carbohydr Polym ; 228: 115408, 2020 Jan 15.
Artigo em Inglês | MEDLINE | ID: mdl-31635742

RESUMO

This report details the design of carboxymethylated cashew gum (CG) as a platform for antibody (Ab) immobilization, which can then be used as a biosensor for bacteria detection. The CG was isolated and characterized, followed by conversion to carboxymethyl cashew gum (CMCG). The CMCG film was a viable support for antibody immobilization; it was electrodeposited on gold surface using the cyclic voltammetry technique, applying a potential sweep from -1.0 V to 1.3 V with a scan rate of 50 mV s-1 and 10 scans. The COOH groups on the surface of the film were critical in promoting Ab bonding. The immobilization of the Ab was mediated by protein A (PrA) for recognition of the antigen. Voltammetry studies were used to monitor the antibody immobilization. Finally, the analytical response of the CMCG-PrA-Ab system was evaluated with the chronoamperometry technique and was found to detect Salmonella Typhimurium bacteria rapidly and efficiently.


Assuntos
Anacardium/metabolismo , Técnicas Biossensoriais/métodos , Exsudatos de Plantas/química , Gomas Vegetais/química , Salmonella typhimurium/isolamento & purificação , Anticorpos/administração & dosagem
4.
PLoS Negl Trop Dis ; 13(10): e0007782, 2019 10.
Artigo em Inglês | MEDLINE | ID: mdl-31609964

RESUMO

BACKGROUND: Salmonella Typhimurium and Enteritidis are major causes of bloodstream infection in children in sub-Saharan Africa. This study assessed evidence for their zoonotic versus human reservoir. METHODS: Index patients were children with blood culture confirmed Salmonella infection recruited during a microbiological surveillance study in Nanoro, rural Burkina between May 2013 and August 2014. After consent, their households were visited. Stool from household members and livestock (pooled samples per species) as well as drinking water were cultured for Salmonella. Isolates with identical serotype obtained from index patient and any household sample were defined as "paired isolates" and assessed for genetic relatedness by multilocus variable number tandem-repeat analysis (MLVA) and whole-genome sequencing (WGS). RESULTS: Twenty-nine households were visited for 32/42 (76.2%) eligible index patients: two households comprised two index patients each, and in a third household the index patient had a recurrent infection. Among the 32 index patients, serotypes were Salmonella Typhimurium (n = 26), Salmonella Enteritidis (n = 5) and Salmonella Freetown (n = 1). All Typhimurium isolates were sequence type (ST)313. Median delay between blood culture sampling and household visits was 13 days (range 6-26). Salmonella was obtained from 16/186 (8.6%) livestock samples (13 serotypes) and 18/290 (6.2%) household members (9 serotypes). None of the water samples yielded Salmonella. Paired Salmonella Typhimurium isolates were obtained from three households representing four index patients. MLVA types were identical in two pairs and similar in the third (consisting of two index patients and one household member). WGS showed a strong genetic relatedness with 0 to 2 core genome SNPs difference between pairs on a household level. Livestock samples did not yield any Salmonella Typhimurium or Salmonella Enteritidis, and the latter was exclusively obtained from blood culture. Other serotypes shared by human and/or livestock carriers in the same household were Salmonella Derby, Drac, Tennessee and Muenster. CONCLUSIONS/SIGNIFICANCE: The current study provides further evidence of a human reservoir for invasive non-Typhoidal Salmonella (iNTS) in sub-Saharan Africa.


Assuntos
Reservatórios de Doenças/microbiologia , Características da Família , Infecções por Salmonella/microbiologia , Salmonella/classificação , Salmonella/isolamento & purificação , Adolescente , Animais , Burkina Faso/epidemiologia , Criança , Pré-Escolar , Monitoramento Ambiental , Fezes/microbiologia , Feminino , Humanos , Lactente , Gado , Masculino , Tipagem de Sequências Multilocus , Filogenia , Salmonella/genética , Infecções por Salmonella/epidemiologia , Salmonella enterica/genética , Salmonella enterica/isolamento & purificação , Salmonella enteritidis/genética , Salmonella enteritidis/isolamento & purificação , Salmonella typhimurium/genética , Salmonella typhimurium/isolamento & purificação , Sorogrupo , Microbiologia da Água , Sequenciamento Completo do Genoma
5.
Int J Food Microbiol ; 309: 108330, 2019 Nov 15.
Artigo em Inglês | MEDLINE | ID: mdl-31493566

RESUMO

A probabilistic model based on logistic regression was developed for a target log reduction of microorganisms inactivated by high hydrostatic pressure. Published inactivation data of Salmonella Typhimurium in broth for 4 and 5 log reductions, and Escherichia coli in buffer and carrot juice for 5 log reduction were used. The probabilities of achieving 4 or 5 log reductions for S. Typhimurium in broth and 5 log reduction for E. coli in buffer and carrot juice could be calculated at different pressure, temperature and time levels. The fitted interfaces of achieving/not achieving the target log reduction were consistent with the experimental data. Although the reliability of the predictions of the developed models could be questioned due to strain variation and different food matrix, a validation study has demonstrated that the developed models could be used to predict the target log reduction of these microorganisms at different pressure, temperature and time levels. This study has indicated that the probabilistic modeling for target log reductions can be useful tool for HHP inactivation of microorganisms, but further studies could be performed with several other factors such as pH and water activity of the food, concentration of certain additives as well as initial number of bacteria present in the food.


Assuntos
Escherichia coli/isolamento & purificação , Microbiologia de Alimentos/métodos , Conservação de Alimentos/métodos , Pressão Hidrostática , Salmonella typhimurium/isolamento & purificação , Contagem de Colônia Microbiana , Reprodutibilidade dos Testes , Temperatura
6.
Nat Commun ; 10(1): 4280, 2019 09 19.
Artigo em Inglês | MEDLINE | ID: mdl-31537784

RESUMO

Bloodstream infections by Salmonella enterica serovar Typhimurium constitute a major health burden in sub-Saharan Africa (SSA). These invasive non-typhoidal (iNTS) infections are dominated by isolates of the antibiotic resistance-associated sequence type (ST) 313. Here, we report emergence of ST313 sublineage II.1 in the Democratic Republic of the Congo. Sublineage II.1 exhibits extensive drug resistance, involving a combination of multidrug resistance, extended spectrum ß-lactamase production and azithromycin resistance. ST313 lineage II.1 isolates harbour an IncHI2 plasmid we name pSTm-ST313-II.1, with one isolate also exhibiting decreased ciprofloxacin susceptibility. Whole genome sequencing reveals that ST313 II.1 isolates have accumulated genetic signatures potentially associated with altered pathogenicity and host adaptation, related to changes observed in biofilm formation and metabolic capacity. Sublineage II.1 emerged at the beginning of the 21st century and is involved in on-going outbreaks. Our data provide evidence of further evolution within the ST313 clade associated with iNTS in SSA.


Assuntos
Adaptação Fisiológica/efeitos dos fármacos , Antibacterianos/farmacologia , Farmacorresistência Bacteriana Múltipla/genética , Salmonella typhimurium/efeitos dos fármacos , Salmonella typhimurium/genética , Adaptação Fisiológica/genética , Animais , Azitromicina/farmacologia , Biofilmes/crescimento & desenvolvimento , Linhagem Celular , Ciprofloxacino/farmacologia , República Democrática do Congo , Humanos , Camundongos , Camundongos Endogâmicos C57BL , Testes de Sensibilidade Microbiana , Plasmídeos/genética , Salmonella typhimurium/isolamento & purificação , Células THP-1 , Sequenciamento Completo do Genoma
7.
Pol J Microbiol ; 68(2): 173-183, 2019.
Artigo em Inglês | MEDLINE | ID: mdl-31257790

RESUMO

In this research, Salmonella species were isolated from the animal, insect and human enteric sources in Faisalabad, Punjab, Pakistan. These species were characterized by different microbiological and molecular techniques including polymerase chain reaction (PCR) by amplification of the 16S rRNA gene. Furthermore, sequencing of the amplicons confirmed all ten isolates as Salmonella strains. The antigenic cross-reactivity was found maximum between the HB1 (strain isolated from honeybee) antiserum and its antigen with an antibody titer of 1:128, while the HB1 antiserum showed a cross-reactive titer range of 1:8 to 1:64. On the basis of the highest geometric mean titer (GMT) shown by the antiserum of the HB1 antigen, it was selected as the best candidate for a cross-reactive live Salmonella oral antigen. Moreover, the HB1 antigen was used a live oral antigen (1 × 1010 CFU/ml) in a safety test in rabbits and proved to be avirulent. During the animal trial, three different oral doses of the HB1 live oral antigen were evaluated in four different rabbits' groups (R1, R2, R3, and R4). The dose number 2 of 0.5 ml (two drops orally and repeated after one week) gave the best GMT measured by indirect hemagglutination (IHA) as compared to the other two doses, while R4 group was kept as control. Results of the challenge protection test also validated the efficacy of the double dose of the HB1 live vaccine, which gave the highest survival percentage. Results of this study lay the foundation for a potential cross-reactive live oral Salmonella vaccine that has proved to be immunogenic in rabbits.In this research, Salmonella species were isolated from the animal, insect and human enteric sources in Faisalabad, Punjab, Pakistan. These species were characterized by different microbiological and molecular techniques including polymerase chain reaction (PCR) by amplification of the 16S rRNA gene. Furthermore, sequencing of the amplicons confirmed all ten isolates as Salmonella strains. The antigenic cross-reactivity was found maximum between the HB1 (strain isolated from honeybee) antiserum and its antigen with an antibody titer of 1:128, while the HB1 antiserum showed a cross-reactive titer range of 1:8 to 1:64. On the basis of the highest geometric mean titer (GMT) shown by the antiserum of the HB1 antigen, it was selected as the best candidate for a cross-reactive live Salmonella oral antigen. Moreover, the HB1 antigen was used a live oral antigen (1 × 1010 CFU/ml) in a safety test in rabbits and proved to be avirulent. During the animal trial, three different oral doses of the HB1 live oral antigen were evaluated in four different rabbits' groups (R1, R2, R3, and R4). The dose number 2 of 0.5 ml (two drops orally and repeated after one week) gave the best GMT measured by indirect hemagglutination (IHA) as compared to the other two doses, while R4 group was kept as control. Results of the challenge protection test also validated the efficacy of the double dose of the HB1 live vaccine, which gave the highest survival percentage. Results of this study lay the foundation for a potential cross-reactive live oral Salmonella vaccine that has proved to be immunogenic in rabbits.


Assuntos
Antígenos de Bactérias/imunologia , Abelhas/microbiologia , Salmonelose Animal/prevenção & controle , Salmonella typhimurium/imunologia , Salmonella typhimurium/isolamento & purificação , Vacinas Tíficas-Paratíficas/imunologia , Animais , Antígenos de Bactérias/administração & dosagem , DNA Bacteriano/genética , Fezes/microbiologia , Reação em Cadeia da Polimerase , RNA Ribossômico 16S/genética , Coelhos , Salmonelose Animal/microbiologia , Salmonella typhimurium/classificação
8.
Analyst ; 144(16): 4795-4802, 2019 Aug 05.
Artigo em Inglês | MEDLINE | ID: mdl-31274133

RESUMO

A simple and robust fluorescence sensing strategy has been developed for the detection of pathogenic bacteria by the combination of the dual functionality of phi29 DNA polymerase with isothermal circular strand displacement polymerization (ICSDP). The strategy relies on target-triggered formation of a mature primer that initiates the cyclic strand displacement polymerization reaction with the aid of dual functional phi29; thus, amplified detection of the target can be achieved. To our knowledge, this work is the first report where dual functional phi29-assisted ICSDP has been employed for fluorescence sensing of pathogenic bacteria. It is worth noting that a hairpin pre-primer is introduced that can be trimmed into a mature primer for initiating ICSDP via the 3' → 5' proofreading exonuclease activity of phi29, which contributes to the ultrahigh specificity of the strategy owing to the elimination of the unwished nonspecific extension. On the basis of the present amplification strategy, our biosensor exhibits excellent specificity and sensitivity toward S. typhimurium with an excellent detection limit as low as 1.5 cfu mL-1. In addition, the strategy offers the advantages of a simplified operation, shortened analysis time, and highly sensitive detection of pathogens with only a one-step reaction. Furthermore, by redesigning the corresponding binding molecules, the proposed strategy can be easily extended for the detection of a wide spectrum of analytes. Hence, the dual functional phi29-assisted ICSDP strategy indeed creates a robust and convenient fluorescence sensing platform for the identification of pathogenic bacteria and related food safety analysis.


Assuntos
DNA Bacteriano/análise , DNA Polimerase Dirigida por DNA/química , Salmonella typhimurium/isolamento & purificação , Fagos Bacilares/enzimologia , Bacillus subtilis , Técnicas Biossensoriais/métodos , Sondas de DNA/química , Sondas de DNA/genética , DNA Bacteriano/genética , Escherichia coli , Fluoresceínas/química , Corantes Fluorescentes/química , Sequências Repetidas Invertidas , Limite de Detecção , Listeria , Técnicas de Amplificação de Ácido Nucleico/métodos , Hibridização de Ácido Nucleico , Espectrometria de Fluorescência , Proteínas Virais/química
9.
Biosensors (Basel) ; 9(3)2019 Jul 28.
Artigo em Inglês | MEDLINE | ID: mdl-31357708

RESUMO

Leafy vegetables have been associated with high-profile outbreaks causing severe illnesses. Timely and accurate identification of potential contamination is essential to ensure food safety. A surface plasmon resonance (SPR) assay has been developed for the detection of Salmonella Typhimurium in leafy vegetables. The assay utilizes a pair of well characterized monoclonal antibodies specific to the flagellin of S. Typhimurium. Samples of romaine lettuce contaminated with S. Typhimurium at different levels (between 0.9 and 5.9 log cfu/g) were pre-enriched in buffered peptone water. Three SPR assay formats, direct assay, sequential two-step sandwich assay, and pre-incubation one-step sandwich assay were evaluated. All three assay formats detect well even at a low level of contamination (0.9 log cfu/g). The SPR assay showed a high specificity for the detection of S. Typhimurium in the presence of other commensal bacteria in the romaine lettuce samples. The results also suggested that further purification of flagellin from the sample preparation using immunomagnetic separation did not improve the detection sensitivity of the SPR assay. The functional protocol developed in this study can be readily used for the detection of S. Typhimurium in leafy vegetables with high sensitivity and specificity.


Assuntos
Técnicas Biossensoriais , Alface/microbiologia , Salmonella typhimurium/isolamento & purificação , Ressonância de Plasmônio de Superfície/métodos , Flagelina/imunologia , Microbiologia de Alimentos
10.
Anal Chim Acta ; 1078: 151-160, 2019 Oct 31.
Artigo em Inglês | MEDLINE | ID: mdl-31358213

RESUMO

Herein, we report a new signal amplification scheme for quantitative biochemical analysis based on gold nanoparticle (GNPs) catalyzed polymerization of transparent silane solution to milky white and turbid siloxane. Using immunoassay as a proof of concept, GNP labeled immunoprobe was used to bind captured antigen and catalyse the polymerization reaction allowing sensitive biochemical investigation. The polymerization reaction was optimized for standard 96 well polystyrene microtiter plates and we discovered that sodium lactate acts as an enhancer in the polymerization reaction as it reduces detection time to merely 30 min. The sensing strategy was applied to detection and quantification of Salmonella Typhimurium in water and egg samples and the platform showed excellent visibly quantifiable analytical response up to 100 cells mL-1. Furthermore, clinical utility and potential of the method was validated by detecting Vi capsular polysaccharide (Vi antigen) responsible for typhoidal Salmonellosis in human serum in sandwich format with a detection limit of 1 ng mL-1. The method serves as the first report towards nanoparticle triggered polymerization for development of rapid and low cost quantitative biochemical assay.


Assuntos
Ouro/química , Imunoensaio/métodos , Nanopartículas Metálicas/química , Polissacarídeos Bacterianos/sangue , Salmonella typhimurium/isolamento & purificação , Siloxanas/síntese química , Animais , Anticorpos/imunologia , Galinhas , Água Potável/microbiologia , Ovos/microbiologia , Contaminação de Alimentos/análise , Humanos , Limite de Detecção , Tamanho da Partícula , Polimerização , Polissacarídeos Bacterianos/imunologia , Estudo de Prova de Conceito , Salmonella typhimurium/imunologia , Silanos/química , Temperatura
11.
Biosens Bioelectron ; 140: 111333, 2019 Sep 01.
Artigo em Inglês | MEDLINE | ID: mdl-31153017

RESUMO

Early screening of foodborne pathogens is a key to ensure food safety. In this study, we developed a microfluidic biosensor for online and sensitive detection of Salmonella based on immunomagnetic separation, fluorescence labeling and smartphone video processing. First, the immune magnetic nanoparticles were used to specifically separate and efficiently concentrate the target bacteria and the magnetic bacteria were formed. Then, the magnetic bacteria were labeled with the immune fluorescent microspheres and the fluorescent bacteria were formed. Finally, the fluorescent bacteria were continuously injected into the microfluidic chip on the smartphone-based fluorescent microscopic system, and the fluorescent spots were online counted using the smartphone App based on inter-frame difference algorithm to obtain the amount of the target bacteria. Under the optimal conditions, this proposed biosensor was able to quantitatively detect Salmonella typhimurium ranging from 1.4 × 102 to 1.4 × 106 CFU/mL, and its lower detection limit was 58 CFU/mL. This biosensor could be extended for detection of multiple foodborne pathogens using different fluorescent materials.


Assuntos
Carga Bacteriana/instrumentação , Técnicas Biossensoriais/instrumentação , Dispositivos Lab-On-A-Chip , Salmonella typhimurium/isolamento & purificação , Smartphone/instrumentação , Desenho de Equipamento , Fluorescência , Contaminação de Alimentos/análise , Microbiologia de Alimentos , Inocuidade dos Alimentos , Humanos , Separação Imunomagnética , Limite de Detecção , Aplicativos Móveis , Infecções por Salmonella/microbiologia
12.
PLoS Negl Trop Dis ; 13(6): e0007297, 2019 06.
Artigo em Inglês | MEDLINE | ID: mdl-31170153

RESUMO

BACKGROUND: Invasive non-typhoidal Salmonella (iNTS) serovars S. Typhimurium and S. Enteritidis are major etiologic agents of invasive bacterial disease among infants and young children in sub-Saharan Africa, including in Mali. Early studies of iNTS serovars in several countries indicated that S. Typhimurium was more prevalent than S. Enteritidis, including in Mali before 2008. We investigated genomic and associated phenotypic changes associated with an increase in the relative proportion of iNTS caused by S. Enteritidis versus S. Typhimurium in Bamako, Mali, during the period 2002-2012. METHODOLOGY/PRINCIPAL FINDINGS: Comparative genomics studies identified homologs of tetracycline resistance and arsenic utilization genes that were associated with the temporal shift of serovars causing iNTS shift, along with several hypothetical proteins. These findings, validated through PCR screening and phenotypic assays, provide initial steps towards characterizing the genomic changes consequent to unknown evolutionary pressures associated with the shift in serovar prevalence. CONCLUSIONS/SIGNIFICANCE: This work identified a shift to S. Enteritidis from the more classic S. Typhimurium, associated with iNTS in Bamako, Mali, during the period 2002-2012. This type of shift in underlying iNTS pathogens are of great importance to pediatric public health in endemic regions of sub-Saharan Africa. Additionally, this work demonstrates the utility of combining epidemiologic data, whole genome sequencing, and functional characterization in the laboratory to identify and characterize genomic changes in the isolates that may be involved with the observed shift in circulating iNTS agents.


Assuntos
Bacteriemia/epidemiologia , Bacteriemia/microbiologia , Evolução Molecular , Genótipo , Infecções por Salmonella/epidemiologia , Infecções por Salmonella/microbiologia , Salmonella typhimurium/genética , Genômica , Humanos , Mali/epidemiologia , Prevalência , Salmonella typhimurium/classificação , Salmonella typhimurium/isolamento & purificação , Fatores de Virulência/genética
13.
Artigo em Inglês | MEDLINE | ID: mdl-31214517

RESUMO

Non-typhoidal Salmonella (NTS) strains are Gram negative bacterial pathogens that are associated with foodborne illness worldwide. During the process of infection, Salmonella uses two molecular injectisomes known as Type 3 Secretion Systems (T3SS) to secrete virulence factors that are encoded by Salmonella Pathogenicity Island-1 (SPI-1) and SPI-2 into host cells. These secretion systems play a major role in virulence, as shown in various animal models, but little is known about their role in human infections. In Saudi Arabia, NTS strains frequently cause human infections but data regarding these pathogenic strains is fairly limited. The aim of this study was to characterize Salmonella human clinical isolates in Riyadh, Saudi Arabia, by determining their serotype, testing for the presence of SPI-1 and SPI-2 genes and to determine the antibiotic resistance profiles of these strains. Using the rapid Check and Trace Salmonella ™ (CTS) system our results demonstrate that S. Enteritidis and S. Typhimurium were the predominant serovars, followed by S. Livingstone, S. Kentucky and S. Poona among a list of 36 serovars reported for the first time in the country. In addition, SPI-1 genes were detected in 99% of the isolates, while the sifA gene (SPI-2) was not detected in 13.5% of the isolates. These results suggest that both the SPI-1 and SPI-2 virulence determinants are important for human infection. Moreover, we report the presence of a Multi-Drug (MDR) carbapenem resistant S. Kentucky isolate harboring the bla OXA-48 gene not reported previously in Saudi Arabia.


Assuntos
Proteínas de Bactérias/isolamento & purificação , Proteínas de Membrana/isolamento & purificação , Salmonella enteritidis/isolamento & purificação , Salmonella typhimurium/isolamento & purificação , Sorogrupo , Febre Tifoide/microbiologia , Fatores de Virulência/genética , Animais , Antibacterianos/farmacologia , Proteínas de Bactérias/genética , Carbapenêmicos/farmacologia , Modelos Animais de Doenças , Farmacorresistência Bacteriana Múltipla , Genoma Bacteriano , Genótipo , Humanos , Proteínas de Membrana/genética , Salmonella enteritidis/classificação , Salmonella enteritidis/efeitos dos fármacos , Salmonella enteritidis/genética , Salmonella typhimurium/classificação , Salmonella typhimurium/efeitos dos fármacos , Salmonella typhimurium/genética , Arábia Saudita/epidemiologia , Sorotipagem , Sistemas de Secreção Tipo III/genética , Sistemas de Secreção Tipo III/isolamento & purificação , Virulência , beta-Lactamases/genética
14.
Analyst ; 144(15): 4505-4512, 2019 Aug 07.
Artigo em Inglês | MEDLINE | ID: mdl-31225571

RESUMO

Pathogenic bacteria such as Shiga toxigenic Escherichia coli and Salmonella can cause severe food-borne diseases. Rapid and sensitive detection of these foodborne pathogens is essential to ensure food safety. In this study, a novel method based on cell elongation induced by beta-lactam antibiotics for direct microscopic counting of Gram-negative bacteria was established. Combined with the sample preparation steps of membrane filtration and magnetic separation, the detection of E. coli O157:H7 and Salmonella enterica serotype Typhimurium was achieved by direct optical microscopic counting of the number of elongated bacteria. The limit of detection of E. coli O157:H7 and S. typhimurium could reach 20 CFU mL-1. The recovery tests for E. coli O157:H7 and S. typhimurium in water and milk samples showed acceptable recovery values between 93.6% and 106.2%. This method is sensitive, cost effective, and rapid (<2 h) and shows great potential for the detection of Gram-negative pathogens in various environmental and food samples.


Assuntos
Carga Bacteriana/métodos , Escherichia coli O157/isolamento & purificação , Separação Imunomagnética/métodos , Salmonella typhimurium/isolamento & purificação , Animais , Antibacterianos/farmacologia , Anticorpos Monoclonais/imunologia , Aztreonam/farmacologia , Escherichia coli O157/efeitos dos fármacos , Escherichia coli O157/imunologia , Limite de Detecção , Fenômenos Magnéticos , Leite/microbiologia , Salmonella typhimurium/efeitos dos fármacos , Salmonella typhimurium/imunologia , Microbiologia da Água
15.
Biosens Bioelectron ; 141: 111317, 2019 Sep 15.
Artigo em Inglês | MEDLINE | ID: mdl-31226602

RESUMO

This work reports a new paper-based sensing platform and its application in a label-free potentiometric immunosensor for Salmonella typhimurium detection based on the blocking surface principle. A paper-based strip electrode was integrated with a filter paper pad which acted as a reservoir of the internal solution. The design offers a convenient platform for antibody immobilization and sampling, proving also that is a simple and affordable methodology to control an ionic flux through a polymer membrane. Two different immunosensing interfaces were assembled on the developed paper-strip electrode. The simplest interface relied on direct conjugation of the antibody to the polymer membrane and the second one resorted to an intermediate layer of a polyamidoamine dendrimer, with an ethylenediamine core from the fourth generation. Electrochemical impedance spectroscopy was used to assess the successive interface modification steps and the resulting analytical performance of both immunosensors was compared. For such, the potential shift derived from the blocking effect of the ionic flux caused by antigen-antibody conjugation was correlated with the logarithm of the Salmonella typhimurium concentration in the sample. In optimized conditions, a limit of detection of 5 cells mL-1 was achieved. As a proof-of-concept, the proposed method was applied to apple juice samples, demonstrating to be a suitable prototype to be used in real scenarios in useful time (<1 h assay).


Assuntos
Técnicas Biossensoriais/instrumentação , Análise de Alimentos/instrumentação , Sucos de Frutas e Vegetais/microbiologia , Potenciometria/instrumentação , Salmonella typhimurium/isolamento & purificação , Anticorpos Imobilizados/química , Técnicas Eletroquímicas/instrumentação , Eletrodos , Humanos , Imunoensaio/instrumentação , Limite de Detecção , Papel , Fitas Reagentes/análise , Infecções por Salmonella/microbiologia
16.
PLoS One ; 14(6): e0218325, 2019.
Artigo em Inglês | MEDLINE | ID: mdl-31216306

RESUMO

Based on the high sensitivity and stable fluorescence of CdTe quantum dots (QDs) in conjunction with a specific DNA aptamer, the authors describe an aptamer-based fluorescence assay for the determination of Salmonella Typhimurium. The fluorescence detection and quantification of S. Typhimurium is based on a magnetic separation system, a combination of aptamer-coated Fe3O4 magnetic particles (Apt-MNPs) and QD-labeled ssDNA2 (complementary strand of the aptamer). Apt-MNPs are employed for the specific capture of S. Typhimurium. CdTe QD-labeled ssDNA2 was used as a signaling probe. Simply, the as-prepared CdTe QD-labeled ssDNA2 was first incubated with the Apt-MNPs to form the aptamer-ssDNA2 duplex. After the addition of S. Typhimurium, they could specifically bind the DNA aptamer, leading to cleavage of the aptamer-ssDNA2 duplex, accompanied by the release of CdTe QD-labeled DNA. Thus, an increased fluorescence signal can be achieved after magnetic removal of the Apt-MNPs. The fluorescence of CdTe QDs (λexc/em = 327/612 nm) increases linearly in the concentration range of 10 to 1010 cfu•mL-1, and the limit of detection is determined to be 1 cfu•mL-1. The detection process can be performed within 2 h and is successfully applied to the analysis of spiked food samples with good recoveries from 90% to 105%.


Assuntos
Aptâmeros de Nucleotídeos/química , Técnicas Biossensoriais , Infecções por Salmonella/diagnóstico , Salmonella typhimurium/isolamento & purificação , Compostos de Cádmio/química , Óxido Ferroso-Férrico/química , Fluorescência , Humanos , Pontos Quânticos/química , Infecções por Salmonella/microbiologia , Salmonella typhimurium/patogenicidade , Telúrio/química
17.
J Microbiol Biotechnol ; 29(6): 962-972, 2019 Jun 28.
Artigo em Inglês | MEDLINE | ID: mdl-31216839

RESUMO

Non-typhoidal Salmonella (NTS) is one of the most frequent causes of bacterial foodborne illnesses. Considering that the main reservoir of NTS is the intestinal tract of livestock, foods of animal origin are regarded as the main vehicles of Salmonella infection. In particular, poultry colonized with Salmonella Typhimurium (S. Typhimurium), a dominant serotype responsible for human infections, do not exhibit overt signs and symptoms, thereby posing a potential health risk to humans. In this study, comparative genomics approaches were applied to two S. Typhimurium strains, ST1539 and ST1120, isolated from a duck slaughterhouse and a pig farm, respectively, to characterize their virulence and antimicrobial resistance-associated genomic determinants. ST1539 containing a chromosome (4,905,039 bp; 4,403 CDSs) and a plasmid (93,876 bp; 96 CDSs) was phylogenetically distinct from other S. Typhimurium strains such as ST1120 and LT2. Compared to the ST1120 genome (previously deposited in GenBank; CP021909.1 and CP021910.1), ST1539 possesses more virulence determinants, including ST64B prophage, plasmid spv operon encoding virulence factors, genes encoding SseJ effector, Rck invasin, and biofilm-forming factors (bcf operon and pefAB). In accordance with the in silico prediction, ST1539 exhibited higher cytotoxicity against epithelial cells, better survival inside macrophage cells, and faster mice-killing activity than ST1120. However, ST1539 showed less resistance against antibiotics than ST1120, which may be attributed to the multiple resistanceassociated genes in the ST1120 chromosome. The accumulation of comparative genomics data on S. Typhimurium isolates from livestock would enrich our understanding of strategies Salmonella employs to adapt to diverse host animals.


Assuntos
Farmacorresistência Bacteriana , Genoma Bacteriano/genética , Aves Domésticas , Salmonelose Animal/microbiologia , Salmonella typhimurium/genética , Salmonella typhimurium/patogenicidade , Matadouros , Animais , Antibacterianos/farmacologia , Proteínas de Bactérias/genética , Sobrevivência Celular , Farmacorresistência Bacteriana/genética , Feminino , Células HeLa , Humanos , Camundongos , Camundongos Endogâmicos BALB C , Filogenia , Plasmídeos/genética , Prófagos/genética , República da Coreia , Salmonella typhimurium/classificação , Salmonella typhimurium/isolamento & purificação , Sorogrupo , Suínos , Virulência/genética
18.
Biotechnol Appl Biochem ; 66(5): 842-849, 2019 Sep.
Artigo em Inglês | MEDLINE | ID: mdl-31228877

RESUMO

Salmonella Typhimurium is a major cause of food poisoning. To solve the limitations of the routine enzyme linked immunosorbent assay such as laborious assay procedure, lack of long-term enzyme stability, and insufficient sensitivity, we provided a non-enzymatic colorimetric immunosorbent assay platform to overcome these problems. The highly photostable redox dye particles was constructed by silica particles (diameter = 598 ± 14.4 nm) loaded with methylene blue (Si-MB) and applied to be a label for immunoassay of S. Typhimurium. The sandwich assay format involved incubation of an analyte in a microplate wells modified with monoclonal anti-Salmonella, followed by exposure to a polyclonal anti-Salmonella/Si-MB bioconjugate and then measurement of absorbance at 598 nm. The platform had an assay time of 20 min, could detect heat-killed Salmonella with a limit of detection of 48 CFU mL-1 , and gave good recoveries in milk. The labels could be stored at 4 °C for 70 days without any deterioration.


Assuntos
Imunoensaio , Azul de Metileno/química , Salmonella typhimurium/isolamento & purificação , Dióxido de Silício/química , Tamanho da Partícula , Processos Fotoquímicos , Propriedades de Superfície
19.
Vet Pathol ; 56(5): 681-690, 2019 09.
Artigo em Inglês | MEDLINE | ID: mdl-31106677

RESUMO

Salmonella is a major foodborne pathogen and pork is one of the main sources of human salmonellosis. Understanding the pathogenesis and progression of the infection within the host is of interest to establish potential approaches to control the disease in pigs. The present study evaluates factors such as intestinal colonization, fecal shedding, and pathogen persistence by 2 studies using experimental challenge with Salmonella Typhimurium in weaned pigs and euthanasia at different time points (1, 2, and 6 and 2, 14, and 30 days postinfection [dpi], respectively). Histopathology of intestine at early time points (1 dpi and 2 dpi) showed severe damage to the epithelium together with an increase in polymorphonuclear cells and macrophages (P < .001), particularly in jejunum and ileum. Large quantities of Salmonella were detected within the contents of the ileum, cecum, and colon in early infection. Salmonella could also be observed in the medulla of tonsils and mesenteric lymph nodes. From 6 dpi onward, signs of recovery were observed, with progressive restoration of the epithelium, reduction of the inflammatory infiltrate, and elimination of Salmonella from the mucosa. Concentration of Salmonella in feces and ileum content decreased, but shedding did not cease even at 4 weeks after infection. Persistence of the bacteria in mesenteric lymph nodes was identified within the connective tissue at 14 and 30 dpi. Our results demonstrate a recovery of the disease after an initial acute phase but also show persistence within the lumen and surrounding lymphoid tissue. These findings are relevant to developing effective control strategies.


Assuntos
Gastroenteropatias/veterinária , Trato Gastrointestinal/microbiologia , Tecido Linfoide/microbiologia , Salmonelose Animal/microbiologia , Salmonella typhimurium/isolamento & purificação , Doenças dos Suínos/microbiologia , Animais , Fezes/microbiologia , Gastroenteropatias/microbiologia , Suínos
20.
Anal Bioanal Chem ; 411(20): 5233-5242, 2019 Aug.
Artigo em Inglês | MEDLINE | ID: mdl-31127336

RESUMO

Foodborne illness is a common yet preventable public health concern generating significant costs for the healthcare system, making systems to accurately detect this pathogen a topic of current research. Enzyme-based immunoassays are highly desirable because they offer shorter response times compared to traditional culture-based methods. Biosensors employing the electrochemical and optical detection of a substrate oxidized by horseradish peroxidase (HRP) have been used to successfully detect biomolecules; however, their inability to handle large sample volumes severely limits their application to food safety despite their accuracy and reliability. Here, we describe a biosensor with the capacity to process a large sample volume by utilizing an Ag/AgCl reference electrode, a platinum counter electrode, and a porous working electrode made from graphite felt coated with antibodies specific for Salmonella common structural antigens. This design allows samples to flow-through the electrode while capturing target pathogens. Following sample exposure, HRP-conjugated antibodies facilitate pathogen detection that culminates in an oxidation reaction with the output analyzed via Osteryoung square wave voltammetry. Detection limits of 1000 Salmonella enterica serotype Typhimurium cells were achieved using this newly devised flow-through, enzyme-amplified, electrochemical biosensor in samples as large as 60 mL. The low cost of the sensor allows for incorporation into disposable detection devices while its design not only broadens its applicability in sample processing but also permits the detection of various microbes by simply exchanging the antibodies.


Assuntos
Anticorpos Antibacterianos/análise , Técnicas Biossensoriais , Técnicas Eletroquímicas/instrumentação , Eletrodos , Peroxidase do Rábano Silvestre/metabolismo , Salmonella typhimurium/isolamento & purificação , Limite de Detecção , Porosidade , Reprodutibilidade dos Testes , Salmonella typhimurium/imunologia
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