An Oral Inoculation Infant Rabbit Model for Shigella Infection

Refining the gut colonization Zophobas morio larvae model using an oral administration of multidrug-resistant Escherichia coli

BACKGROUND

The darkling beetle Zophobas morio can be implemented as an alternative in vivo model to study different intestinal colonization aspects. Recently, we showed that its larvae can be colonized by multidrug-resistant Escherichia coli strains administered via contaminated food (for 7 d) for a total experimental duration of 28 d.

METHOD

In the present work, we aimed to shorten the model to 14 d (T14) by administering the previously used CTX-M-15 extended-spectrum β-lactamase-producing ST131 E. coli strain Ec-4901.28 via a single oral administration (5 µL dose of 108 CFU/mL), using a blunt 26s-gauge needle connected to a 250 μL gastight syringe. Force-feeding was performed either without or with (larvae placed on ice for 10 min before injection) anaesthesia. In addition, phage-treated larvae were orally injected with 10 µL of INTESTI bacteriophage cocktail (∼105-6 PFU/mL) on d 4 (T4) and 7 (T7).

RESULTS

Growth curve analyses showed that, while larvae rapidly became colonized with Ec-4901.28 (T1, ∼106-7 CFU/mL), only those anaesthetized maintained a high bacterial load (∼102-3 vs. ∼105-6 CFU/mL) and survival rate (76% vs. 99%; P < 0.001) by T14. Moreover, bacteriophage administration to anaesthetized larvae significantly reduced the bacterial count of INTESTI-susceptible Ec-4901.28 at T14 (5.17 × 105 vs. 2.26 × 104, for non-treated and phage-treated larvae, respectively; P = 0.04).

CONCLUSIONS

The methodological refinements applied to establish the intestinal colonization model simplify the use of Z. morio larvae, facilitate prompt evaluation of novel decolonization approaches and reduce experiments involving vertebrate animals in accordance with the Replacement, Reduction and Refinement principles.

Shigella sonnei: epidemiology, evolution, pathogenesis, resistance and host interactions

Shigella sonnei is a major cause of diarrhoea globally and is increasing in prevalence relative to other Shigella because of multiple demographic and environmental influences. This single-serotype species has traditionally received less attention in comparison to Shigella flexneri and Shigella dysenteriae, which were more common in low-income countries and more tractable in the laboratory. In recent years, we have learned that Shigella are highly complex and highly susceptible to environmental change, as exemplified by epidemiological trends and increasing relevance of S. sonnei. Ultimately, methods, tools and data generated from decades of detailed research into S. flexneri have been used to gain new insights into the epidemiology, microbiology and pathogenesis of S. sonnei. In parallel, widespread adoption of genomic surveillance has yielded insights into antimicrobial resistance, evolution and organism transmission. In this Review, we provide an overview of current knowledge of S. sonnei, highlighting recent insights into this globally disseminated antimicrobial-resistant pathogen and assessing how novel data may impact future vaccine development and implementation.

Cascaded signal amplification strategy for ultra-specific, ultra-sensitive, and visual detection of Shigella flexneri

Pathogen infections including Shigella flexneri have posed a significant threat to human health for numerous years. Although culturing and qPCR were the gold standards for pathogen detection, time-consuming and instrument-dependent restrict their application in rapid diagnosis and economically less-developed regions. Thus, it is urgently needed to develop rapid, simple, sensitive, accurate, and low-cost detection methods for pathogen detection. In this study, an immunomagnetic beads-recombinase polymerase amplification-CRISPR/Cas12a (IMB-RPA-CRISPR/Cas12a) method was built based on a cascaded signal amplification strategy for ultra-specific, ultra-sensitive, and visual detection of S. flexneri in the laboratory. Firstly, S. flexneri was specifically captured and enriched by IMB (Shigella antibody-coated magnetic beads), and the genomic DNA was released and used as the template in the RPA reaction. Then, the RPA products were mixed with the pre-loaded CRISPR/Cas12a for fluorescence visualization. The results were observed by naked eyes under LED blue light, with a sensitivity of 5 CFU/mL in a time of 70 min. With no specialized equipment or complicated technical requirements, the IMB-RPA-CRISPR/Cas12a diagnostic method can be used for visual, rapid, and simple detection of S. flexneri and can be easily adapted to monitoring other pathogens.

Genomic insights into extensively drug-resistant Pseudomonas aeruginosa isolated from a diarrhea case in Kolkata, India

Aim: To characterize extensively drug-resistant Pseudomonas aeruginosa from a patient with diarrhea. Materials & methods: Antimicrobial susceptibility was tested by the disk diffusion method. The P. aeruginosa genome was sequenced to identify virulence, antibiotic resistance and prophages encoding genes. Results: P. aeruginosa had a wide spectrum of resistance to antibiotics. Genomic analysis of P. aeruginosa revealed 76 genes associated with antimicrobial resistance, xenobiotic degradation and the type three secretion system. Conclusion: This is the first report on diarrhea associated with P. aeruginosa. Since no other organism was identified, the authors assume that the patient had dysbiosis due to antibiotic exposure, leading to antibiotic-associated diarrhea. The in vivo toxicity expressed by the pathogen may be associated with T3SS.

Microbiomics Revealed the Disturbance of Intestinal Balance in Rabbits with Diarrhea Caused by Stopping the Use of an Antibiotic Diet

The harmful effects of diarrhea on the growth performance of rabbits have been well documented, but the details of the potential mechanism of intestinal diarrhea when antibiotics are stopped are still unclear. Here, PacBio sequencing technology was used to sequence the full length 16S rRNA gene of the microbiota of intestinal content samples, in order to characterize the bacterial communities in the small intestine (duodenum and jejunum) and large intestine (colon and cecum) in normal Hyplus rabbits and those with diarrhea. The histopathological examination showed that intestinal necrosis occurred in different degrees in the diarrhea group, and that the mucosal epithelium was shed and necrotic, forming erosion, and the clinical manifestation was necrosis. However, the intestinal tissue structure of the normal group was normal. The results revealed that there were significant differences in bacterial communities and structure between the diarrhea and normal groups of four intestinal segments (p < 0.05). In general, 16 bacterial phyla, 144 bacterial genera and 22 metabolic pathways were identified in the two groups. Tax4Fun functional prediction analysis showed that KEGG related to amino acid metabolism and energy metabolism was enriched in the large intestines of rabbits with diarrhea, whereas lipid metabolism was more abundant in the small intestine of rabbits with diarrhea. In conclusion, the change in the relative abundance of the identified dominant microbiota, which could deplete key anti-inflammatory metabolites and lead to bacterial imbalance and diarrhea, resulted in diarrhea in Hyplus rabbits that stopped using antibiotics.

The type 3 secretion effector IpgD promotes S. flexneri dissemination

The bacterial pathogen Shigella flexneri causes 270 million cases of bacillary dysentery worldwide every year, resulting in more than 200,000 deaths. S. flexneri pathogenic properties rely on its ability to invade epithelial cells and spread from cell to cell within the colonic epithelium. This dissemination process relies on actin-based motility in the cytosol of infected cells and formation of membrane protrusions that project into adjacent cells and resolve into double-membrane vacuoles (DMVs) from which the pathogen escapes, thereby achieving cell-to-cell spread. S. flexneri dissemination is facilitated by the type 3 secretion system (T3SS) through poorly understood mechanisms. Here, we show that the T3SS effector IpgD facilitates the resolution of membrane protrusions into DMVs during S. flexneri dissemination. The phosphatidylinositol 4-phosphatase activity of IpgD decreases PtdIns(4,5)P₂ levels in membrane protrusions, thereby counteracting de novo cortical actin formation in protrusions, a process that restricts the resolution of protrusions into DMVs. Finally, using an infant rabbit model of shigellosis, we show that IpgD is required for efficient cell-to-cell spread in vivo and contributes to the severity of dysentery.

The intracellular pathogen Shigella flexneri is the causative agent of bacillary dysentery (blood in stool). Invasion of epithelial cells and cell-to-cell spread are critical determinants of S. flexneri pathogenesis. Cell-to-cell spread relies on the formation of membrane protrusions that project into adjacent cells and resolve into vacuoles. The molecular mechanisms supporting this dissemination process are poorly understood. In this study, we show that S. flexneri employs the phosphatidylinositol phosphatase activity of the T3SS effector protein IpgD to manipulate phosphoinositides in the protrusion membrane. Manipulation of phosphoinositide signaling restricts the formation of actin networks underneath the protrusion membrane, which would otherwise prevent the scission of protrusions into vacuoles. We also demonstrate that IpgD is required for efficient dissemination in the colon of infant rabbits and contributes to the severity of disease. This study exemplifies how manipulation of phosphoinositide signaling by intracellular pathogens supports bacterial pathogenesis.

A colloidal gold immunochromatographic strip assay for the rapid detection of Shigella in milk and meat products

Anti-Shigella mAb was produced using IpaC and an immunochromatographic strip was developed to detect different serotypes of Shigella in food.