Invasive non-typhoidal Salmonella (iNTS) aminoglycoside-resistant ST313 isolates feature unique pathogenic mechanisms to reach the bloodstream.

Invasive non-typhoidal Salmonella (iNTS) from the clonal type ST313 (S. Typhimurium ST313) is the primary cause of invasive salmonellosis in Africa. Recently, in Brazil, iNTS ST313 strains have been isolated from different sources, but there is a lack of understanding of the mechanisms behind how these gut bacteria can break the gut barrier and reach the patient's bloodstream. Here, we compare 13 strains of S. Typhimurium ST313, previously unreported isolates, from human blood cultures, investigating aspects of virulence and mechanisms of resistance. Initially, RNAseq analyses between ST13-blood isolate and SL1344 (ST19) prototype revealed 15 upregulated genes directly related to cellular invasion and replication, such as sopD2, sifB, and pipB. Limited information is available about S. Typhimurium ST313 pathogenesis and epidemiology, especially related to the global distribution of strains. Herein, the correlation of strains isolated from different sources in Brazil was employed to compare clinical and non-clinical isolates, a total of 22 genomes were studied by single nucleotide polymorphism (SNPs). The epidemiological analysis of 22 genomes of S. Typhimurium ST313 strains grouped them into three distinct clusters (A, B, and C) by SNP analysis, where cluster A comprised five, group B six, and group C 11. The 13 clinical blood isolates were all resistant to streptomycin, 92.3% of strains were resistant to ampicillin and 15.39% were resistant to kanamycin. The resistance genes acrA, acrB, mdtK, emrB, emrR, mdsA, and mdsB related to the production of efflux pumps were detected in all (100%) strains studied, similar to pathogenic traits investigated. In conclusion, we evidenced that S. Typhimurium ST313 strains isolated in Brazil have unique epidemiology. The elevated frequencies of virulence genes such as sseJ, sopD2, and pipB are a major concern in these Brazilian isolates, showing a higher pathogenic potential.

A new complex of silver(I) with probenecid: Synthesis, characterization, and studies of antibacterial and extended spectrum ß-lactamases (ESBL) inhibition activities.

This article describes the in vitro antibacterial and ß-lactamase inhibition of a novel silver(I) complex with the sulfonamide probenecid (Ag-PROB). The formula Ag2C26H36N2O8S2·2H2O for the Ag-PROB complex was proposed based on elemental analysis. High-resolution mass spectrometric studies revealed the existence of the complex in its dimeric form. Infrared, nuclear magnetic resonance spectroscopies and Density Functional Theory calculations indicated a bidentate coordination of probenecid to the silver ions by the oxygen atoms of the carboxylate. In vitro antibacterial activities of Ag-PROB showed significant growth inhibitory activity over Mycobacterium tuberculosis, S. aureus, and P. aeruginosa PA01biofilm-producers, B. cereus, and E. coli. The Ag-PROB complex was active over multi-drug resistant of uropathogenic E. coli extended spectrum ß-lactamases (ESBL) producing (EC958 and BR43), enterohemorrhagic E. coli (O157:H7) and enteroaggregative E. coli (O104:H4). Ag-PROB was able to inhibit CTX-M-15 and TEM-1B ESBL classes, at concentrations below the minimum inhibitory concentration for Ag-PROB, in the presence of ampicillin (AMP) concentration in which EC958 and BR43 bacteria were resistant in the absence of Ag-PROB. These results indicate that, in addition to ESBL inhibition, there is a synergistic antibacterial effect between AMP and the Ag-PROB. Molecular docking results revealed potential key residues involved in interactions between Ag-PROB, CTX-M-15 and TEM1B, suggesting the molecular mechanism of the ESBL inhibition. The obtained results added to the absence of mutagenic activity and low cytotoxic activity over non-tumor cell of the Ag-PROB complex open a new perspective for future in vivo tests demonstrating its potential of use as an antibacterial agent.