Application of an indirect immunofluorescent staining method for detection of Salmonella enteritidis in paraffin slices and antigen location in infected duck tissues

Identification of foodborne pathogenic bacteria using confocal Raman microspectroscopy and chemometrics

Rapid and accurate identification of foodborne pathogenic bacteria is of great importance because they are often responsible for the majority of serious foodborne illnesses. The confocal Raman microspectroscopy (CRM) is a fast and easy-to-use method known for its effectiveness in detecting and identifying microorganisms. This study demonstrates that CRM combined with chemometrics can serve as a rapid, reliable, and efficient method for the detection and identification of foodborne pathogenic bacteria without any laborious pre-treatments. Six important foodborne pathogenic bacteria including S. flexneri, L. monocytogenes, V. cholerae, S. aureus, S. typhimurium, and C. botulinum were investigated with CRM. These pathogenic bacteria can be differentiated based on several characteristic peaks and peak intensity ratio. Principal component analysis (PCA) was used for investigating the difference of various samples and reducing the dimensionality of the dataset. Performances of some classical classifiers were compared for bacterial detection and identification including decision tree (DT), artificial neural network (ANN), and Fisher's discriminant analysis (FDA). Correct recognition ratio (CRR), area under the receiver operating characteristic curve (ROC), cumulative gains, and lift charts were used to evaluate the performance of models. The impact of different pretreatment methods on the models was explored, and pretreatment methods include Savitzky-Golay algorithm smoothing (SG), standard normal variate (SNV), multivariate scatter correction (MSC), and Savitzky-Golay algorithm 1st Derivative (SG 1st Der). In the DT, ANN, and FDA model, FDA is more robust for overfitting problem and offers the highest accuracy. Most pretreatment methods raised the performance of the models except SNV. The results revealed that CRM coupled with chemometrics offers a powerful tool for the discrimination of foodborne pathogenic bacteria.

Dual Transcriptomic Analyses Unveil Host-Pathogen Interactions Between Salmonella enterica Serovar Enteritidis and Laying Ducks (Anas platyrhynchos)

Salmonella enteritidis (SE) is a pathogen that can readily infect ovarian tissues and colonize the granulosa cell layer such that it can be transmitted via eggs from infected poultry to humans in whom it can cause food poisoning. Ducks are an important egg-laying species that are susceptible to SE infection, yet the host–pathogen interactions between SE and ducks have not been thoroughly studied to date. Herein, we performed dual RNA-sequencing analyses of these two organisms in a time-resolved infection model of duck granulosa cells (dGCs) by SE. In total, 10,510 genes were significantly differentially expressed in host dGCs, and 265 genes were differentially expressed in SE over the course of infection. These differentially expressed genes (DEGs) of dGCs were enriched in the cytokine–cytokine receptor interaction pathway via KEGG analyses, and the DEGs in SE were enriched in the two-component system, bacterial secretion system, and metabolism of pathogen factors pathways as determined. A subsequent weighted gene co-expression network analysis revealed that the cytokine–cytokine receptor interaction pathway is mostly enriched at 6 h post-infection (hpi). Moreover, a number of pathogenic factors identified in the pathogen–host interaction database (PHI-base) are upregulated in SE, including genes encoding the pathogenicity island/component, type III secretion, and regulators of systemic infection. Furthermore, an intracellular network associated with the regulation of SE infection in ducks was constructed, and 16 cytokine response-related dGCs DEGs (including IL15, CD40, and CCR7) and 17 pathogenesis-related factors (including sseL, ompR, and fliC) were identified, respectively. Overall, these results not only offer new insights into the mechanisms underlying host–pathogen interactions between SE and ducks, but they may also aid in the selection of potential targets for antimicrobial drug development.

Application of lectin-based biosensor technology in the detection of foodborne pathogenic bacteria: a review

Foodborne diseases caused by pathogenic bacteria pose a serious threat to human health.

Comparative transcriptome analysis reveals PERP upregulated during Salmonella Enteritidis challenge in laying ducks

Salmonella Enteritidis (SE) can be transmitted to eggs through cecum or the ovary from infected layers and causes food poisoning in humans. The mechanism of cecal transmission has been extensively studied. However, the mechanism and route of transovarian transmission of SE remain unclear. In this study, the ducks were orally inoculated with SE, and the ovarian follicles and stroma were collected to detect SE infection. The immune responses were triggered and the innate and adaptive immune genes (TLR4, NOD1, AvβD7, and IL-1β) were upregulated significantly during the SE challenge. Moreover, the ovary tissues (small follicle and stroma) of susceptible and resistant-laying ducks were performed by RNA sequencing. We obtained and identified 23 differentially expressed genes (DEGs) between susceptible and resistant-laying ducks in both small follicle and stroma tissues ( p < 0.05). The DEGs were predominately identified in the p53 signaling pathway. The expression of key genes (p53, MDM2, PERP, caspase-3, and Bcl-2) involved in the signaling pathway was significantly higher in granulosa cells (dGCs) from SE-infected ducks than those from uninfected ducks. Moreover, the overexpression of PERP resulted in further induction of p53, MDM2, caspase-3, and Bcl-2 during SE infection in dGCs. Whereas, an opposite trend was observed with the knockdown of PERP. Besides, it is further revealed that the PERP could enhance cell apoptosis, SE adhesion, and SE invasion in SE-infected dGCs overexpression. Altogether, our results demonstrate the duck PERP involved in the ovarian local immune niche through p53 signaling pathway in dGCs challenged with SE.

Evaluation of the colonization capabilities of Salmonella Enteritidis in quails using an RT-PCR approach

We used a real-time PCR assay and indirect fluorescent antibody (IFA) assay to detect genomic DNA of Salmonella Enteritidis in the internal organs of quails after an oral challenge. The results showed that S. Enteritidis was detected in all the samples at different time points. This study will assist a future understanding of the pathogenesis of S. Enteritidis.

The population of a high-virulence strain of Salmonella enterica serovar Enteritidis in subcutaneously infected partridge: a quantitative time-course study using real-time PCR

This research was undertaken to determine the population of a high-virulence strain of Salmonella enterica serovar Enteritidis in partridge by a fluorescent quencher PCR assay and to correlate these findings with the results obtained from the immunohistochemical localization and histopathological examinations of selected Salmonella enterica serovar Enteritidis-infected tissues. To make the results meaningful, a side-by-side bacteriology method (indirect immuno-fluorescent antibody staining) was performed too. The results of indirect immuno-fluorescent antibody staining and immunohistochemical localization were similar to the fluorescent quencher PCR assay. The time course of the appearance of bacterial antigens and tissue lesions in various tissues was coincident with the levels of the bacterial DNA loads at the infection sites. This suggests that Salmonella enterica serovar Enteritidis loads in internal organs are closely correlated with the progression of the infection.

The pathogenesis of Salmonella enteritidis in experimentally infected ducks: a quantitative time-course study using taqman polymerase chain reaction

Ducks were subcutaneously infected with a high-virulence strain of Salmonella enterica ssp. enterica serovar Enteritidis (Salmonella Enteritidis). The kinetics of the Salmonella Enteritidis genomic DNA loads, the immunohistochemical localization of the bacterial antigens, and the histopathological examination in various tissues were investigated. The results showed that the time course of the appearance of the Salmonella Enteritidis bacterial antigens and the lesions in various tissues was coincident with the bacterial load of the organism in various infected tissues. This suggests that Salmonella Enteritidis loads in systemic organs are closely correlated with the progression of the infection.

Replication kinetics of Salmonella enteritidis in internal organs of ducklings after oral challenge: a quantitative time-course study using real-time PCR

This research was undertaken to understand the replication kinetics of Salmonella enteritidis (S. enteritidis) in the internal organs of ducklings after oral challenge over a 2 wk period. A serovar-specific real-time, fluorescence-based quantitative polymerase chain reaction (FQ-PCR) assay was used to detect genomic DNA of S. enteritidis in the blood and the internal organs at different time points respectively. The results showed that the spleen was positive at 12 h post inoculation (PI) and the blood was at 14 h PI. The organism was detected in the liver and heart at 16 h PI, the pancreas and kidney were positive at 20 h PI, and the final organ to show a positive results was the gallbladder at 22 h PI. The copy number of S. enteritidis DNA in each tissue reached a peak at 24 h-36 h PI, with the liver and spleen containing the highest concentration of S. enteritidis. The blood, heart, kidney, pancreas, and gallbladder had low concentrations. S. enteritidis populations began to decrease and were not detectable at 3 d PI, but were still present up to 2 wk for the spleen without causing apparent symptoms. To make the results meaningful, a side-by-side bacteriology method (IFA) was performed. The results of IFA were similar to the FQ-PCR assay. This research provided a significant data for understanding the life cycle of S. enteritidis in the internal organs, and may help to understand the pathogenesis of S.entertidis in the future.