Detection Of Salmonellae Research Articles

Graphene derivatives-based electrochemical sensors for salmonella detection: A Review

Graphene derivatives-based electrochemical sensors for salmonella detection: A Review

A 3D-Printed Electrochemical Immunosensor Employing Cd/Se ZnS QDs as Labels for the Rapid and Ultrasensitive Detection of Salmonella typhimurium in Poultry Samples

Salmonella is one of the leading causes of foodborne illnesses worldwide, with poultry products being a major source of contamination. Thus, the detection of salmonella in commercial poultry products is crucial to minimize the effects on public health. Electrochemical sensors are promising tools for bacteria detection due to their sensitivity, simplicity, and potential for on-site analysis. In this work, a three-dimensional (3D) printed electrochemical immunosensor for the determination of Salmonella typhimurium in fresh chicken through a sandwich immunoassay employing biotinylated anti-S. typhimurium antibody followed by streptavidin labeled with Cd/Se ZnS quantum dots (QDs) is presented. The device features three carbon-black polylactic acid electrodes and a holder, and the quantification of S. typhimurium is performed by anodic stripping voltametric (ASV) determination of the Cd(II) released after acidic dissolution of the QDs. To enhance sensitivity, an electroplated bismuth film was deposited on the working electrode, achieving a detection limit of 5 cfu/mL in a total assay time of 25 min, whereas 5 h of sample pre-enrichment was required for the detection of 1 cfu/25 mL of chicken rinse and chicken broth. The method is accurate, with %recovery values ranging from 93.3 to 113% in fresh chicken samples, and repeatable with intra- and inter- assay coefficient of variations <2 and 5%, respectively, indicating the suitability of the proposed immunosensor for the detection of S. typhimurium at the point-of-need.

Comparison of colourimetric loop-mediated isothermal amplification (LAMP), PCR and high-resolution melt curve analysis and culture-based diagnostic assays in the detection of three salmonella serotypes in poultry

ABSTRACT The accuracies of two molecular tests, PCR and loop-mediated isothermal amplification (LAMP) assay were compared with bacterial culture in detection of salmonella in poultry clinical samples. The icIR family transcriptional regulator gene was targeted and, out of 56 clinical specimens, 20 poultry field isolates were found positive for salmonella. Along with human isolates, reference strains of three different serovars, Salmonella Enteritidis (S. Enteritidis), S. Typhimurium and S. Infantis, were also tested. Eight different but genetically closely related bacterial genera (Klebsiella, Pseudomonas, Enterobacter, Campylobacter, Staphylococcus, Streptococcus, Escherichia and Pasteurella) were also used to evaluate the specificity of assay. The LAMP assay showed 80.8% sensitivity (95% CI, 0.66–0.95) and 100% specificity (95% CI, 0.71–1.00) when compared with microbiological culture and PCR, both with 100% sensitivity (95% CI, 0.87–1.00) and 100% specificity (95% CI, 0.71–1.00). High-resolution melt (HRM) curve analysis following PCR was able to differentiate between salmonella isolates based on their melting points, and all specimens were genotyped in three distinct HRM curve profiles. Each normalized melt curve profile represented one salmonella serotype and differences between the three melt profiles were correlated with nucleotide variations in the target gene sequences which demonstrated high discriminatory power of this technique. The colourimetric LAMP assay provided an alternative detection method capable of being used in the field, and showed analytical sensitivity for detection of 1 pg of salmonella DNA per reaction. The advantages and disadvantages of each test in detection of salmonella are discussed.

IMMUNOLOGICAL AND BIOSSENSORY TECHNIQUES FOR DETECTION OF SALMONELLA IN FOOD DERIVED FROM FISH FARMING - REVIEW

Salmonellosis is the world's most common foodborne illness. In Brazil, foods contaminated by salmonella lead the statistics. Therefore, the aim of this study is, through biotechnological knowledge, to compile alternative and innovative techniques for the detection of salmonella in foods, such as fish-farming derivatives, immunological and biosensorial techniques. This is a descriptive exploratory data survey of a qualitative nature, aiming at data analysis. Research and data collection were carried out in bibliographic databases: Academic Google, Scielo, CAPES journals and institutional repositories using specific descriptors - in Portuguese and English, with words and terms separated by the Boolean operators 'AND' and 'OR'. Some innovative and alternative methods are available to identify the presence of salmonella in food. Immunological and biosensory techniques, despite being less frequent in the scientific literature than molecular methods, are techniques that present high specificity and sensitivity. These techniques have been the most developed alternative methods in fish in recent years. And, they can employ both molecular and immunological techniques in biorecognition, which is characterized as an advantage of not having a requirement for pre-enrichment of the sample. According to the literature found, the techniques covered in this study are quick to respond, which speeds up decision-making by researchers and technicians, which makes the techniques very promising for industrial application.

A label-free electrochemical immunosensor for rapid detection of salmonella in milk by using CoFe-MOFs-graphene modified electrode

The presence of Salmonella in food has been a serious threat to human health all over the world. Herein, a novel electrochemical immunosensor based on CoFe-MOFs-graphene nanocomposite was constructed to detect Salmonella in milk. The synergy of the large specific surface area and high porosity of CoFe-MOFs and the good electrical conductivity of graphene materials greatly enhanced the current signal of the nanocomposite. Gold nanoparticles were modified on CoFe-MOFs-graphene hybrids by a simple electrodeposition method. Anti-Salmonella antibody was immobilized onto the surface of the constructed electrode through the formation of a stable Au–NH2 bond. Scanning electron microscopy was employed to reveal the structure of the CoFe-MOFs-graphene nanocomposite, and the elements of the nanocomposite were observed by energy-dispersive X-ray spectroscopy. In addition, Fourier transform infrared (FT-IR) and X-ray powder diffraction (XRD) were used to analyze the structure of related materials. Under optimal experimental parameters, the constructed immunosensor detected a wide linear range of Salmonella from 2.4 × 102 CFU mL−1 to 2.4 × 108 CFU mL−1 with a detection limit of 1.2 × 102 CFU mL−1 (S/N = 3). The immunosensor showed good stability, selectivity, and reproducibility. The designed immunosensor provides a new strategy for the rapid detection of foodborne pathogens.

One-step differential detection of Salmonella enterica serovar Typhi, serovar Paratyphi A and other Salmonella spp. by using a quadruplex real-time PCR assay

Diseases caused by typhoidal and non-typhoidal Salmonella remain a considerable threat to both developed and developing countries. Based on the clinical symptoms and serological tests, it is sometimes difficult to differentiate the Salmonella enterica serovar Paratyphi A (S. enterica serovar Paratyphi A) from serovar Typhi (S. enterica serovar Typhi). In this study, we developed a quadruplex real-time polymerase chain reaction (PCR) assay with an internal amplification control (IAC), to simultaneously differentiate S. enterica serovar Paratyphi A from serovar Typhi and to detect other Salmonella serovars which cause salmonellosis in humans. This assay was evaluated on 155 salmonellae and non-salmonellae strains and demonstrated 100% specificity in species differentiation. Inclusion of an IAC did not affect the efficiency of the assay. Further evaluation using a blind test on spiked stool, blood and food specimens showed that the detection limit was at 103 –104 CFU/mL (or g) and a high PCR efficiency with different targets (R2 > 0.99), except for S. enterica serovar Paratyphi A in blood. This assay has been applied to clinical specimens to detect the causative agents of gastrointestinal infections and has successfully identified 6 salmonellosis patients from the 50 diarrhoea patients. The quadruplex real-time PCR developed in this study could enhance the detection and differentiation of salmonellae. This assay could be applied to stools, blood and food based on the notable performance in the simulation tests and field evaluation.

Tryptamine-functionalized magnetic nanoparticles for highly sensitive detection of Salmonella typhimurium.

There is significant demand for the development of rapid, sensitive, and specific methods for detecting bacterial pathogens in order to identify the causes of food poisoning. Nucleic acid amplification tests (NAATs) allow for the culture-free detection of bacterial pathogens and are not as labor intensive and time consuming as culture-based detection methods. However, suitable sample preparation methods must be developed for the realization of simple, rapid, and sensitive NAATs. To resolve this problem, we developed a new sample preparation method that integrates bacterial pathogen enrichment and DNA extraction. We engineered magnetic nanoparticles (MNPs) with a physicochemical probe (tryptamine) for single-tube sample preparation with minimal sample loss. The tryptamine-functionalized MNPs (Indole@MNPs) showed inherent hydrophobicity owing to the indole side chain and a change in their zeta potential with a decrease in the pH. Because of their physicochemical characteristics, the Indole@MNPs could adsorb bacterial pathogens, thus allowing sample enrichment and DNA binding and release through weak electrostatic interactions via pH control. We successfully detected Salmonella enterica serovar Typhimurium, a common cause of bacterial food poisoning, at a concentration of 10 CFU/10 mL in milk samples using quantitative PCR. Thus, the proposed method allows for the simple and sensitive detection of Salmonella typhimurium and can be used for nontyphoidal salmonella detection to ensure food safety.

An aptamer biosensor based dual signal amplification system for the detection of salmonella typhimurium

Salmonella, a typical foodborne pathogen, always seriously threatens the health and even life of both humans and animals. However, highly sensitive and fast quantitative methods for its detection are remaining to be challenged. Herein, we presented an efficient method with dual signal amplification strategy by combining immune hybridization chain reaction (HCR) with surface enhanced Raman scattering (SERS) to high sensitively detect Salmonella typhimurium in food. After sample preparation, S. typhimurium were specifically captured by immunomagnetic beads (IMBs), then aptamers and hairpin-probes were added to trigger HCR to form nicked dsDNA, finally 4’,6-Diamidino-2-phenylindole dihydrochloride (DAPI) was incubated with HCR products and then the whole system was mixed with AgNP colloid to detect the SERS intensity at 1610 cm−1. As a result, a good linear relationship was achieved between SERS intensities and corresponding concentrations of S. typhimurium ranging from 10 to 105 CFU/mL, with a limit of detection (LOD) of 6 CFU/mL in 3.5 h. The proposed method has been successfully applied to capture and detect the S. typhimurium in spiked milk samples, and the results were consistent with those of the traditional plate counting method. The method, with combination of HCR and SERS, achieves double amplification of the detection signal and significantly improves the detection sensitivity of S. typhimurium. And it also shows good application potential for the highly sensitive detection of other contaminants in food.

Spatial Distribution of Salmonella enterica in Poultry Shed Environments Observed by Intensive Longitudinal Environmental Sampling.

Detection of salmonellae within poultry environments is an important component of many food safety programs, but sampling approaches vary greatly and may not enable the detection of salmonellae when bacteria are present at a low prevalence or concentration. Intensive longitudinal sampling within caged sheds enabled us to undertake a longitudinal analysis of the spatial distribution of salmonellae in caged shed environments. Both the number of samples collected and location of sample collection within a poultry shed were important to ensure the best chance of detecting Salmonella spp. Differences in the within-shed spatial distribution of Salmonella enterica subspecies enterica serovar Typhimurium [χ2(27, 1,538) = 54.4; P < 0.001] and Salmonella enterica subspecies enterica serovar Infantis [χ2(27, 1,538) = 79.8; P < 0.0001] were identified. More than one Salmonella enterica serovar was detected in each shed on the same sampling occasion; 5% of all samples contained more than one serovar. Samples collected on the north side of the shed (odds ratio [OR], 1.77; 95% confidence interval [CI], 1.17-2.68), on the sheltered side of the shed (OR, 1.90; 95% CI, 1.26-2.89), and during winter (OR, 48.41; 95% CI, 23.56-104.19) were more likely to be positive for salmonellae. The within-shed differences observed in the both the sample prevalence and spatial location of the serovar detected indicate that there are important shed microenvironmental factors that influence the survival and/or distribution of salmonellae. These factors should be taken into consideration when environmental surveillance is undertaken for salmonellae in flocks housed in cage sheds.IMPORTANCE Routine epidemiological surveillance for salmonellae in poultry relies initially on environmental sampling. Intensive, spatially homogenous sampling, as conducted within this study, confirmed that the sampling methodology conducted within a poultry environment is a nontrivial part of sampling design. The frequency of sampling is especially important when the prevalence of Salmonella spp. is low. These factors must be taken into consideration in the design of studies for the detection of salmonellae in poultry sheds.

Evaluation of the impact of wastewater in the rural commune of Jmaa Moulblad on the bacteriological water quality of the Grou River (Rabat region, Morocco)

In the region of Rabat, shallow watercourses are currently threatened by the magnitude of urban and industrial discharges, mainly due to its growing demography and the continuous development of the agricultural and industrial sectors. This study aims to evaluate the impact of wastewater from the rural commune of Jmaa Moulblad on the bacteriological water qualityof the Grou River. In order to measure the pollution levels of this watercourse, our study focused on the enumeration of fecal contamination indicator bacteria such as total coliforms (TC), faecal coliforms (FC) and intestinal enterococci (EI), as well as the detection of salmonella. Water samples were taken by season during the 2016/2017 period at four stations on the Grou River. The results obtained describe a worrying state of the watercourse, particularly at the S 2 station located directly at the mouth of the wastewater of the rural commune of Jmaa Moulblad which is rejected without prior treatment. If protective measures are not taken, the perpetual degradation of the quality of these waters would certainly lead to the loss of this watercourse, which is of paramount importance in the region.

Clinical results of the use of the highest approved dose of monthly paliperidone palmitate: PICTURE sub-analysis study

Contamination of eggs with Salmonella enterica is a significant risk factor contributing to foodborne disease. Periods of peak egg contamination were identified by conducting longitudinal environmental and egg sampling in 7 layer flocks until they were 50 weeks of age. A total of 714 environmental samples and 8958 eggs were cultured using standard methods for the detection of salmonellae. Pooled egg contamination with Salmonella Typhimurium or Salmonella Infantis was detected at a true prevalence (TP) of 0.002 (95% CI = 0.001, 0.004) or 0.005 (95% CI = 0.004, 0.007), respectively. S. Typhimurium and S. Infantis were detected in individual egg components; in shell rinse at a TP of 0.014 (95% CI = 0.005, 0.038), in shell and membrane at a TP of 0.01 (95% CI = 0.003, 0.032), and in albumen and yolk content at a TP of 0.007 (95% CI = 0.001, 0.027). The concentration of salmonellae in all fractions was <1 CFU/mL. The TP of Salmonella enterica in eggs was highest at the onset of lay. Higher egg prevalence was associated with a lower body weight, higher egg production, higher egg weight and mass than the breed standard for age, and poorer feed conversion efficiency. Flock physiology appears to have an important influence on the detection of eggs contaminated with Salmonella enterica.

An economic analysis of salmonella detection in fresh produce, poultry, and eggs using whole genome sequencing technology in Canada

The study estimates the annual costs of nontyphoidal Salmonellosis (referred to as Salmonellosis from hereon) from fresh produce, poultry and eggs in Canada. It also estimates the economic benefits from introduction of Whole Genome Sequencing (WGS) in detection of Salmonellosis clusters and outbreaks. Monetary and non-monetary costs from Salmonellosis are estimated. Monetary costs are divided into direct healthcare, indirect, federal and producer costs. Probability models are used to account for uncertainty in the cost-of-illness estimates. Two types of non-monetary costs have been estimated: Disability-adjusted Live Years and Quality-adjusted Life Years. These estimates are then used to calculate the economic impact of WGS on detection of Salmonellosis. The estimated incidence of illnesses is 47,082 annually, which represents a cost of $287.78 million (total cases) and $166.28 million (reported cases) from the traditional technology. The total net benefit from introduction of WGS is estimated to range from $5.21 million-$90.25 million. All monetary values are in CAD unless stated otherwise. WGS will help in reducing the economic burden from Salmonellosis. These estimates help will aid policy related decision making.

Does only the age of the hen matter in Salmonella enterica contamination of eggs?

Contamination of eggs with Salmonella enterica is a significant risk factor contributing to foodborne disease. Periods of peak egg contamination were identified by conducting longitudinal environmental and egg sampling in 7 layer flocks until they were 50 weeks of age. A total of 714 environmental samples and 8958 eggs were cultured using standard methods for the detection of salmonellae. Pooled egg contamination with Salmonella Typhimurium or Salmonella Infantis was detected at a true prevalence (TP) of 0.002 (95% CI = 0.001, 0.004) or 0.005 (95% CI = 0.004, 0.007), respectively. S. Typhimurium and S. Infantis were detected in individual egg components; in shell rinse at a TP of 0.014 (95% CI = 0.005, 0.038), in shell and membrane at a TP of 0.01 (95% CI = 0.003, 0.032), and in albumen and yolk content at a TP of 0.007 (95% CI = 0.001, 0.027). The concentration of salmonellae in all fractions was <1 CFU/mL. The TP of Salmonella enterica in eggs was highest at the onset of lay. Higher egg prevalence was associated with a lower body weight, higher egg production, higher egg weight and mass than the breed standard for age, and poorer feed conversion efficiency. Flock physiology appears to have an important influence on the detection of eggs contaminated with Salmonella enterica.

Distribution of Salmonella Enteritidis in internal organs and variation of cecum microbiota in chicken after oral challenge

The aim study was to explore the distribution of Salmonella Enteritidis (S. enteritidis) in internal organs and variation of cecum microbiota in newly hatched chicken after oral challenge during a 21-day period. The quantities of S. enteritidis DNA in different internal organs (heart, liver, spleen, stomach, pancreas, small intestine, blood and cecum contents) were determined by real-time fluorescent quantitative polymerase chain reaction (FQ-PCR). The result showed that all of the above-mentioned samples were positive at 12 h post inoculation (PI) after oral challenge. The highest copy numbers of S. enteritidis in all tissue were heart and liver, with about 2 × 102 to 6 × 106 copies of DNA target sequences/0.5 g. The copy number of S. enteritidis in the stomach was only lower than the heart and liver. The blood at 8 d PI, the pancreas at 10 d PI, the heart at 14 d PI and the stomach at 17 d PI didn't have a positive result. However, the liver, spleen, cecum contents and small intestine were all positive during the 21-day period. The cecum contents at 0 d PI, 4 d PI and 10 d PI from the control group and experiment group were collected for bacterial 16 S rRNA sequencing targeting the V3-V4 hypervariable region. The result showed that at the 0 d PI, the main cecum microbiota ingredient of the two-day old chicken was Enterobacteriaceae (Proteobacteria) and the other microbiology species were fewer. At the 10 d PI, the microbiota ingredient of cecum became abundant and stable mainly including the families Ruminococcaceae (Firmicutes), Enterobacteriaceae (Proteobacteria), Lachnospiraceae (Firmicutes) and clostridiacaea (Firmicutes) both of the two group, suggesting Salmonella infection with 2-day old chicken might not significantly change cecum microbiota community. The study indicated the major organs, which carried numerous S. enteritidis, providing a significantly guideline for salmonella detection in poultry and revealed the main microbiota ingredient of chicken cecum.

Nanoporous gold as a suitable substrate for preparation of a new sensitive electrochemical aptasensor for detection of Salmonella typhimurium

Nowadays, achievement to easy, fast, reliable and cost-effective techniques and tools is one of the most important challenges in detection of microorganisms. Salmonella typhimurium is one of the most important pathogenic bacteria that affect the human health and environmental infections. In this work we report a new, stable, biocompatible and cost-effective platform for construction of an aptasensor based on nanoporous gold (NPG) for detection of S. typhimurium. Nanoporous gold is electrochemically synthesized using Au-Cu alloy at the surface of Au/GCE. Thiol functionalized aptamer is used for effective linking to the surface of NPG/Au/GCE via self-assemble monolayers (SAMs) formation. Morphological and voltammetric characterizations of the fabricated aptasensor were performed by cyclic voltammetry (CV), electrochemical impedance spectroscopy (EIS), scanning electron microscopy (SEM) and energy dispersive spectroscopy (EDS). The purposed aptasensor is capable to detect S. typhimurium in a wide linear dynamic range 6.5×102 to 6.5×108CFUmL−1 with a LOQ of 6.5×101CFUmL−1 and LOD of 1CFUmL−1. The prepared aptasensor showed some significant advantages such as sensitivity, selectivity, repeatability and ability to distinguish between live and dead bacteria cells. The prepared biosensor is successfully applied for salmonella detection in real samples such as egg.

Antibody fragmentation technique for salmonella detection by SPR based biosensor

This chapter describes and discusses the different proposed low salinity/engineered water injection (LSWI/EWI) models for both sandstones and carbonates. The general approach of modeling low salinity water is discussed. This includes linear interpolation between two sets of relative permeability curves, capillary pressure curves, and residual oil saturation values representing an oil-wet state (initial condition) and water-wet state (final condition) using an interpolating factor. Moreover, field-scale modeling and optimization of LSWI/EWI is included. Also, tracer modeling of LSWI/EWI is discussed.

ELIME assay vs Real-Time PCR and conventional culture method for an effective detection of Salmonella in fresh leafy green vegetables

The detection of Salmonella according to EC regulation is still primarily based on traditional microbiological culture methods that may take several days to be completed.The purpose of this work is to demonstrate the applicability of an Enzyme-Linked-Immuno-Magnetic-Electrochemical (ELIME) assay, recently developed by our research group for the detection of salmonella in irrigation water, in fresh (raw and ready-to-eat) leafy green vegetables by comparison with Real-Time PCR (RTi-PCR) and ISO culture methods.Since vegetables represent a more complex matrix than irrigation water, preliminary experiments were carried out on two leafy green vegetables that resulted negative for salmonella by the ISO method. 25g of these samples were experimentally inoculated with 1–10 CFU of S. Napoli or S. Thompson and pre-enriched for 20h in two different broths. At this time aliquots were taken, concentrated at different levels by centrifugation, and analyzed by ELIME and RTi-PCR. Once selected the best culture medium for salmonella growth, and the optimal concentration factor suitable to reduce the sample matrix effect, enhancing the out-put signal, several raw and ready-to-eat leafy green vegetables were artificially inoculated and pre-enriched. Aliquots were then taken at different incubation times and analyzed with both techniques. Results obtained showed that 20 and 8h of pre-enrichment were required to allow the target salmonella (1–10 CFU/25g) to multiply until reaching a detectable concentration by ELIME and RTi-PCR assays, respectively. A confirmation with the ISO culture method was carried out. Based on the available literature, this is the first report of the application of an ELISA based method for the detection of Salmonella in vegetables.

Validation of the Applied Biosystems 7500 Fast Instrument for the Detection of Salmonellae with SureTect Salmonella Species PCR Kit.

The Thermo Scientific SureTect™ Salmonella species real-time PCR assay is a rapid alternative method designed for the detection of salmonellae in a wide range of foods, animal feeds, and production-environment samples. The assay has previously been validated according to the AOAC Research Institute Performance Tested Methods(SM) program using Thermo Scientific PikoReal™ PCR cycler and Thermo Scientific SureTect Software Performance Tested Method 051303). This report details the method-modification study performed to validate an updated assay format, utilizing a reduced target probe concentration and an extension of the PCR cycler platform to enable the use of the kit with a Applied Biosystems 7500 Fast PCR cycler and Applied Biosystems RapidFinder™ Express 2.0 software. During this validation study, a matrix study was conducted on a subset of the method's claimed matrixes, comparing the performance of the modified SureTect Salmonella species kit (a reduced target probe concentration with a 7500 Fast platform) to the reference method detailed in ISO 6579:2002. No significant difference by probability of detection statistical analysis was found between SureTect or International Organization for Standardization methods for any of the matrixes analyzed during the study. Inclusivity and exclusivity studies using the modified method demonstrated accurate results for the 117 Salmonella and 36 non-Salmonella strains tested. Multiple production lots of the newly formatted kit were evaluated and found to be consistent with the current assay. Robustness studies confirmed that the change to the kit had no impact on the assay's performance when alterations were made to method parameters having the greatest potential impact on assay performance.

Development of a Simple, Peripheral-Blood-Based Lateral-Flow Dipstick Assay for Accurate Detection of Patients with Enteric Fever.

Enteric fever is a systemic infection caused by typhoidal strains of Salmonella enterica and is a significant cause of mortality and morbidity in many parts of the world, especially in resource-limited areas. Unfortunately, currently available diagnostic tests for enteric fever lack sensitivity and/or specificity. No true clinically practical gold standard for diagnosing patients with enteric fever exists. Unfortunately, microbiologic culturing of blood is only 30 to 70% sensitive although 100% specific. Here, we report the development of a lateral-flow immunochromatographic dipstick assay based on the detection of Salmonella enterica serovar Typhi (S Typhi) lipopolysaccharide (LPS)-specific IgG in lymphocyte culture secretion. We tested the assay using samples from 142 clinically suspected enteric fever patients, 28 healthy individuals residing in a zone where enteric fever is endemic, and 35 patients with other febrile illnesses. In our analysis, the dipstick detected all blood culture-confirmed S Typhi cases (48/48) and 5 of 6 Salmonella enterica serovar Paratyphi A blood cultured-confirmed cases. The test was negative in all 35 individuals febrile with other illnesses and all 28 healthy controls from the zone of endemicity. The test was positive in 19 of 88 individuals with suspected enteric fever but with negative blood cultures. Thus, the dipstick had a sensitivity of 98% compared to blood culture results and a specificity that ranged from 78 to 100% (95% confidence interval [CI], 70 to 100%), depending on the definition of a true negative. These results suggest that this dipstick assay can be very useful for the detection of enteric fever patients especially in regions of endemicity.

Enhancement of immunohistochemical detection of Salmonella in tissues of experimentally infected pigs.

Salmonella Typhimurium is one of the main pathogens compromising porcine and human health as well as food safety, because it is a prevailing source of foodborne infections due to contaminated pork. A prominent problem in the management of this bacteriosis is the number of subclinically infected carrier pigs. As very little is known concerning the mechanisms allowing Salmonella to persist in pigs, the objective of this study was to develop an immunohistochemical approach for the detection of salmonellae in tissue of pigs experimentally infected with Salmonella Typhimurium. Samples were obtained from a challenge trial in which piglets of the German Landrace were intragastrically infected with Salmonella enterica serovar Typhimurium DT104 (1.4-2.1×1010 CFU). Piglets were sacrificed on days 2 and 28 post infection. Tissue samples of jejunum, ileum, colon, ileocecal mesenteric lymph nodes (Lnn. ileocolici), and tonsils (Tonsilla veli palatini) were fixed in Zamboni’s fixative and paraffin-embedded. Different immunohistochemical staining protocols were evaluated. Salmonella was detected in varying amounts in the tissues. Brown iron-containing pigments in the lymph nodes interfered with the identification of Salmonella if DAB was used as a staining reagent. Detergents like Triton X-100 or Saponin enhanced the sensitivity. It seems advisable not to use a detection system with brown staining for bacteria in an experimental setup involving intestinal damage including haemorrhage. The use of detergents appears to result in a higher sensitivity in the immunohistochemical detection of salmonellae.