A novel rspA gene regulates biofilm formation and virulence of Salmonella Typhimurium.

Salmonella spp. are facultative anaerobic, Gram-negative, rod-shaped bacteria and belongs to the Enterobacteriaceae family. Although much has been known about Salmonella pathogenesis, the functional characterizations of certain genes are yet to be explored. The rspA (STM14_1818) is one such gene with putative dehydratase function, and its role in pathogenesis is unknown. The background information showed that rspA gene is upregulated in Salmonella when it resides inside macrophages, which led us to investigate its role in Salmonella pathogenesis. We generated the rspA knockout strain and complement strain in S. Typhimurium 14028. Ex-vivo and in-vivo infectivity was looked at macrophage and epithelial cell lines and Caenorhabditis elegans (C. elegans). The mutant strain differentially formed the biofilm at different temperatures by altering the expression of genes involved in the synthesis of cellulose and curli. Besides, the mutant strain is hyperproliferative intracellularly and showed increased bacterial burden in C. elegans. The mutant strain became more infectious and lethal, causing faster death of the worms than the wild type, and also modulates the worm's innate immunity. Thus, we found that the rspA deletion mutant was more pathogenic. In this study, we concluded that the rspA gene differentially regulates the biofilm formation in a temperature dependent manner by modulating the genes involved in the synthesis of cellulose and curli and negatively regulates the Salmonella virulence for longer persistence inside the host.

Pregnancy, infection, and epigenetic regulation: A complex scenario.

A unique immunological condition, pregnancy ensures fetus from maternal rejection, allows adequate fetal development, and protects against microorganisms. Infections during pregnancy may lead to devastating consequences for pregnant women and fetuses, resulting in the mother's death, miscarriage, premature childbirth, or neonate with congenital infection and severe diseases and defects. Epigenetic (heritable changes in gene expression) mechanisms like DNA methylation, chromatin modification, and gene expression modulation during gestation are linked with the number of defects in the fetus and adolescents. The feto-maternal crosstalk for fetal survival during the entire gestational stages are tightly regulated by various cellular pathways, including epigenetic mechanisms that respond to both internal as well outer environmental factors, which can influence the fetal development across the gestational stages. Due to the intense physiological, endocrinological, and immunological changes, pregnant women are more susceptible to bacterial, viral, parasitic, and fungal infections than the general population. Microbial infections with viruses (LCMV, SARS-CoV, MERS-CoV, and SARS-CoV-2) and bacteria (Clostridium perfringens, Coxiella burnetii, Listeria monocytogenes, Salmonella enteritidis) further increase the risk to maternal and fetal life and developmental outcome. If the infections remain untreated, the possibility of maternal and fetal death exists. This article focused on the severity and susceptibility to infections caused by Salmonella, Listeria, LCMV, and SARS-CoV-2 during pregnancy and their impact on maternal health and the fetus. How epigenetic regulation during pregnancy plays a vital role in deciding the fetus's developmental outcome under various conditions, including infection and other stress. A better understanding of the host-pathogen interaction, the characterization of the maternal immune system, and the epigenetic regulations during pregnancy may help protect the mother and fetus from infection-mediated outcomes.

Implications of differences between point-of-care blood gas analyser and laboratory analyser potassium results on hyperkalaemia diagnosis & treatment.

BACKGROUND: Hyperkalaemia is managed in the emergency department (ED) following measurement of potassium results by blood gas analysers (BGA) or laboratory analysers (LAB). AIMS: To determine the prevalence of clinically significant differences between BGA and LAB potassium results and the impact on ED hyperkalaemia management. METHODS: Retrospective analysis of time-matched ED BGA and LAB potassium samples from 2019 to 2020 (taken within 15 min, one or both results ≥6.0 mmol/L). Mean differences and 95% limits of agreement (LoA) were determined for pairs with one or both results ≥6.0 mmol/L and a separate 500 consecutive sample pairs. RESULTS: Four hundred eighty-eight matched BGA and LAB samples met the inclusion criteria. Of these, 201 (41.2%) differed by ≤0.5 mmol/L, 169 (34.6%) included a haemolysed LAB sample, and 12 (2.5%) had an unreportable BGA sample. One hundred six (21.7%) pairs differed by >0.5 mmol/L, and 60/106 (57%) had normal LAB potassium results, but BGA indicated moderate/severe hyperkalaemia (two of these pairs received hyperkalaemia treatment). Of patients with a haemolysed LAB sample, or where pairs differed by >0.5 mmol, 48 were treated with insulin and five (10.4%) experienced hypoglycaemia. Mean differences and LoA for pairs with LAB results <6.0 mmol/L but BGA ≥6.0 mmol/L demonstrated unacceptable agreement, with 18 (25.7%) BGA results exceeding 8.0 mmol/L. CONCLUSIONS: Potentially significant discordance may occur between BGA and LAB potassium results. Clinicians need to be aware of factors impacting both analytical methods' accuracy (such as poor venepuncture or sample handling, (K) EDTA interference) and undetectable haemolysis with BGA measurements. We recommend BGA hyperkalaemia be confirmed with LAB results using a non-haemolysed sample where time permits.

Immune modulations and survival strategies of evolved hypervirulent Salmonella Typhimurium strains.

BACKGROUND: Evolving multidrug-resistance and hypervirulence in Salmonella is due to multiple host-pathogen, and non-host environmental interactions. Previously we had studied Salmonella adaptation upon repeated exposure in different in-vitro and in-vivo environmental conditions. This study deals with the mechanistic basis of hypervirulence of the passaged hypervirulent Salmonella strains reported previously. METHODS: Real-time PCR, flow cytometry, western blotting, and confocal microscopy were employed to check the alteration of signaling pathways by the hypervirulent strains. The hypervirulence was also looked in-vivo in the Balb/c murine model system. RESULTS: The hypervirulent strains altered cytokine production towards anti-inflammatory response via NF-κB and Akt-NLRC4 signaling in RAW-264.7 and U-937 cells. They also impaired lysosome number, as well as co-localization with the lysosome as compared to unpassaged WT-STM. In Balb/c mice also they caused decreased antimicrobial peptides, reduced nitric oxide level, altered cytokine production, and reduced CD4+ T cell population leading to increased organ burden. CONCLUSIONS: Hypervirulent Salmonella strains infection resulted in an anti-inflammatory environment by upregulating IL-10 and down-regulating IL-1ß expression. They also evaded lysosomal degradation for their survival. With inhibition of NF-κB and Akt signaling, cytokine expression, lysosome number, as well as the bacterial burden was reverted, indicating the infection mediated immune modulation by the hypervirulent Salmonella strains through these pathways. GENERAL SIGNIFICANCE: Understanding the mechanism of adaptation can provide better disease prognosis by either targeting the bacterial gene or by strengthening the host immune system that might ultimately help in controlling salmonellosis.