Search Results (6)

Background/Objectives: Salmonella Saintpaul (SSa) is increasingly linked to foodborne outbreaks in Brazil and globally. Despite its rising public health significance, its epidemiology, genomic diversity, and pathogenic potential remain underexplored. This study addresses these gaps through a comprehensive global analysis of SSa population dynamics, outbreak patterns, and genetic structures, along with an in-depth phenotypic and genomic characterization of strain PP_BR059, isolated from a hospitalized patient in Ceará, Brazil. Methods: We analyzed 1,953 publicly available SSa genomes using core-genome multi-locus sequence typing (cgMLST), antimicrobial resistance (AMR) profiling, pan-genome analysis, and phylogenetic inference. A genome-wide association study (GWAS) identified genetic determinants of virulence and AMR. The invasiveness and intracellular survival of PP_BR059 were assessed using in vitro macrophage infection assays, while whole-genome sequencing (WGS) provided genetic insights. Results: Phylogenetic analysis identified 49 sequence types (STs), with ST-50 (787 genomes) and ST-27 (634 genomes) being most prevalent. ST-50 included all clinical strains from South America, including PP_BR059. AMR analysis showed 60% of SSa genomes were pan-susceptible, while ST-27 had the highest proportion of AMR strains. GWAS revealed distinct evolutionary lineages within ST-50 and ST-27. PP_BR059 exhibited lower macrophage invasion (3.82%) but significantly higher intracellular survival at 2 h (68.72%) and 20 h (25.68%) post-infection. WGS confirmed a pan-susceptible AMR profile and plasmid absence. Conclusions: This study highlights SSa’s global dissemination, evolutionary trends, and pathogenic variability, emphasizing the need for molecular surveillance to inform public health interventions. Full article

Recent genomic characterisation of translocating Escherichia coli HMLN-1 isolated from mesenteric lymph nodes (MLNs) and blood of a patient with a fatal case of pancreatitis revealed the presence of a type 6 secretion system (T6SS) that was not present in non-translocating E. coli strains. This strain was also genomically similar to adherent-invasive E. coli (AIEC) LF82 pathotype. We aimed to identify the role of T6SS-1 in the pathogenesis of this strain and other pathogenic E. coli. The HMLN-1 strain was initially tested for the presence of six virulence genes (VGs) associated with AIEC strains and an iron sequestering system. Additionally, HMLN-1’s interaction with a co-culture of Caco-2:HT29-MTX cells and its intra-macrophagic survival was evaluated. We subsequently screened a collection of 319 pathogenic E. coli strains isolated from patients with urinary tract infection (UTI), diarrhoea, inflammatory bowel disease (IBD) and septicaemia for the presence of T6SS-1 and its expression related to adhesion, invasion and translocation via the above co-culture of the intestinal cell lines. The results showed that HMLN-1 harboured four of the AIEC-associated VGs (dsbA, htrA, ompC and afaC). Screening of the pathogenic E. coli collection detected the presence of the T6SS-1 genes in septicaemic and UTI E. coli strains at a significantly higher level than diarrhoea and IBD strains (p < 0.0001). The high expression of T6SS-1 in E. coli HMLN-1 upon adhesion and invasion, as well as its high prevalence among extra-intestinal E. coli strains, suggests a role for T6SS-1 in the pathogenesis of translocating E. coli. Full article

Yersinia pseudotuberculosis is an extracellular foodborne pathogen and usually causes self-limiting diarrhea in healthy humans. MgtC is known as a key subversion factor that contributes to intramacrophage adaptation and intracellular survival in certain important pathogens. Whether MgtC influences the fitness of Y. pseudotuberculosis is unclear. According to in silico analysis, MgtC in Y. pseudotuberculosis might share similar functions with other bacterial pathogens, such as Salmonella. Studies indicated that MgtC was clearly required for Y. pseudotuberculosis growth in vitro and bacterial survival in macrophages under Mg²⁺ starvation. Transcriptome analysis by RNA-seq indicated that 127 differentially expressed genes (DEGs) (fold change > 2 and p < 0.001) were discovered between wild-type PB1+ and mgtC mutant inside macrophages. However, a lack of MgtC only moderately, albeit significantly, reduced the virulence of Y. pseudotuberculosis in mice. Overall, this study provides additional insights for the role of MgtC in Y. pseudotuberculosis. Full article

Staphylococcus aureus is a commensal bacterium that causes severe infections in soft tissue and the bloodstream. During infection, S. aureus manipulates host cell response to facilitate its own replication and dissemination. Here, we show that S. aureus significantly decreases the level of SUMOylation, an essential post-translational modification, in infected macrophages 24 h post-phagocytosis. The reduced level of SUMOylation correlates with a decrease in the SUMO-conjugating enzyme Ubc9. The over-expression of SUMO proteins in macrophages impaired bacterial intracellular proliferation and the inhibition of SUMOylation with ML-792 increased it. Together, these findings demonstrated for the first time the role of host SUMOylation response toward S. aureus infection. Full article

Growing evidence indicates that small noncoding RNAs (sRNAs) play important regulatory roles during bacterial infection. In Salmonella Typhimurium, several sRNAs are strongly up-regulated within macrophages, but little is known about their role during the infection process. Among these sRNAs, the well-characterized paralogs RyhB-1 and RyhB-2 are two regulators of gene expression mainly related with the response to iron availability. To investigate the role of the sRNAs RyhB-1 and RyhB-2 from S. Typhimurium in the infection of RAW264.7 macrophages, we analyzed several phenotypic traits from intracellular mutant strains lacking one and both sRNAs. Deletion of RyhB-1 and/or RyhB-2 resulted in increased intracellular survival and faster replication within macrophages. The bacterial metabolic status inside macrophages was also analyzed, revealing that all the mutant strains exhibited higher intracellular levels of ATP and lower NAD⁺/NADH ratios than the wild type. Expression analyses from bacteria infecting macrophages showed that RyhB-1 and RyhB-2 affect the intra-macrophage expression of bacterial genes associated with the Salmonella pathogenicity island 1 (SPI-1) and the type III secretion system (T3SS). With a two-plasmid system and compensatory mutations, we confirmed that RyhB-1 and RyhB-2 directly interact with the mRNAs of the invasion chaperone SicA and the regulatory protein RtsB. Altogether, these results indicate that the RyhB homologs contribute to the S. Typhimurium virulence modulation inside macrophages by reducing the intracellular growth and down-regulating the SPI-1 gene expression. Full article

Mucosa-associated Escherichia coli are increased in Crohn’s disease (CD) and colorectal cancer (CRC). CD isolates replicate within macrophages but the specificity of this effect for CD and its mechanism are unclear. Gentamicin exclusion assay was used to assess E. coli replication within J774.A1 murine macrophages. E. coli growth was assessed following acid, low-nutrient, nitrosative, oxidative and superoxide stress, mimicking the phagolysosome. Twelve of 16 CD E. coli isolates replicated >2-fold within J774.A1 macrophages; likewise for isolates from 6/7 urinary tract infection (UTI), 8/9 from healthy subjects, compared with 2/6 ulcerative colitis, 2/7 colorectal cancer and 0/3 laboratory strains. CD mucosal E. coli were tolerant of acidic, low-nutrient, nitrosative and oxidative stress. Replication within macrophages correlated strongly with tolerance to superoxide stress (rho = 0.44, p = 0.0009). Exemplar CD E. coli HM605 and LF82 were unable to survive within Nfκb1^-/- murine bone marrow-derived macrophages. In keeping with this, pre-incubation of macrophages with hydrocortisone (0.6 µM for 24 h) caused 70.49 ± 12.11% inhibition of intra-macrophage replication. Thus, CD mucosal E. coli commonly replicate inside macrophages, but so do some UTI and healthy subject strains. Replication correlates with resistance to superoxide and is highly dependent on macrophage NF-κB signalling. This may therefore be a good therapeutic target. Full article