Whole genome sequence analysis of the first reported isolate of Salmonella Agona carrying blaCTX-M-55 gene in Brazil

This study analyzes the genomic findings of the first report of Salmonella isolate carrying the blaCTX-M-55 gene, recovered from a bacteremic patient from Brazil. A bacterial isolate positive for the blaCTX-M-55 gene was submitted to antimicrobial susceptibility testing by disk diffusion and epsilometric test. Whole genome sequencing was performed using Illumina technology. Conjugation assay was performed; plasmid sizes determined by S1-PFGE and plasmid content were investigated by hybrid assembly after MinION long reads sequencing. Isolate 288_18 was identified as sequence type ST13, resistant to ampicillin, cefotaxime, ceftazidime, cefepime, ceftriaxone, and aztreonam. A transferable IncFII plasmid sized approximately 67 kb was found to carry the blaTEM-1 and blaCTX-M-55 in a module consisting of IS26-blaTEM-1B-WbuC-blaCTX-M-55-IS26. In addition, an 117 kb IncI1plasmid was also identified in the 288_18 isolate, but without additional resistance genes. To the best of our knowledge, this is the first report of blaCTX-M-55 in Salmonella isolated from human infection in Brazil. The occurrence of blaCTX-M-55 in the IncFII epidemic plasmid in a relevant clinical human isolate of Salmonella Agona underscores the urgent need for enhanced and effective continuous surveillance for controlling its dissemination.

Caracterização fenotípica e molecular de isolados de Salmonella spp. e Escherichia coli Patogênica Extraintestinal resistentes às polimixinas / Phenotypic and molecular characterization of Salmonella spp. and extraintestinal pathogenic Escherichia coli resistant to polymyxins

A resistência antimicrobiana está se tornando um grande desafio para saúde pública devido ao aumento da resistência aos beta-lactâmicos em geral. Os isolados de Salmonella spp. e Escherichia coli são os mais frequentes agentes causadores de doenças de transmissão hídrica e alimentar, mas também podem causar doenças invasivas graves, principalmente em imunodeprimidos, idosos e crianças. Ambos os patógenos vêm apresentando perfis de resistência as principais classes de antibióticos, nestes casos é necessária a busca de uma nova opção terapêutica, como por exemplo, as polimixinas. Em 2015, surgiu o primeiro relato da resistência às polimixinas mediado pelo gene mcr (mobile colistin resistance), que se disseminou por diversos continentes e ocasionou uma grande preocupação global em saúde pública. O objetivo deste trabalho foi identificar e caracterizar os mecanismos que medeiam à resistência à polimixinas em cepas de Salmonella spp. e E. coli Patogênica extraintestinal (ExPEC). Foi realizado a triagem pelo teste da gota e teste da CIM frente a colistina e polimixina B no total de 1026 isolados de Salmonella enterica e 159 isolados de ExPEC. Nos isolados resistentes foi verificado a presença de mutações nos genes (pmrA/B, phoP/Q) associados à resistência às polimixinas, e através da PCR foi feita a identificação dos genes de resistência plasmidial (mcr). Das 124 cepas de Salmonella resistentes a colistina e polimixina B, apenas um isolado foi positivo para o gene mcr-1, e este gene foi detectado em um plasmídeo do grupo IncX4. A cepa 2018.466 foi caracterizada como S. Choleraesuis proveniente de sangue de origem humana. Foram identificados 44 isolados de Salmonella spp. apresentando mutações em pmrA e pmrB. Dos 56 isolados de ExPEC resistentes a colistina, 21 isolados apresentaram o gene mcr-1. Este gene foi detectado em plasmídeos do grupo IncX4 (n=17) e em plasmídeos do grupo IncF (n=4). Cinco isolados de E.coli não apresentaram mutações nos genes estudados,sendo que três eram positivos para o gene mcr-1, enquanto as demais cepas apresentaram mutações em pmrA/B e phoP/Q. A tipagem pela PFGE foi realizada nos isolados de E.coli positivos para o gene mcr-1, com o objetivo de verificar a diversidade genética encontrada entre elas. Foram identificados 18 perfis genéticos, sem um clone principal...(AU)

Antimicrobial resistance is becoming a major public health challenge due to increasing resistance to beta-lactams in general. Salmonella spp. and Escherichia coli are the most frequent causative agents of diseases transmitted by water and food, but they can also cause serious invasive diseases, especially in immunosuppressed individuals, the elderly and children. Both pathogens have shown resistance profiles to the main classes of antibiotics, in these cases it is necessary to search for a new therapeutic option, such as polymyxins. In 2015, the first report of resistance to polymyxins mediated by the mcr gene (mobile colistin resistance) appeared, which spread across several continents and caused a major global concern in public health. The objective of this work was to identify and characterize the mechanisms that mediate resistance to polymyxins in strains of Salmonella spp. and extraintestinal pathogenic E. coli (ExPEC). Screening by drop test and MIC test against colistin and polymyxin B was performed on a total of 1026 Salmonella enterica isolates and 159 ExPEC isolates. In the resistant isolates, the presence of mutations in the genes (pmrA/B, phoP/Q) associated with resistance to polymyxins was verified, and through PCR the plasmid resistance genes (mcr) were identified. Of the 124 Salmonella strains resistant to colistin and polymyxin B, only one isolate was positive for the mcr-1 gene, and this gene was detected in a plasmid from the IncX4 group. Strain 2018.466 was characterized as S. Choleraesuis from blood of human origin. Forty-four Salmonella spp. showing mutations in pmrA and pmrB. Of the 56 colistin-resistant ExPEC isolates, 21 isolates harbored the mcr-1 gene. This gene was detected in plasmids from the IncX4 group (n=17) and in plasmids from the IncF group (n=4). Five E.coli isolates did not show mutations in the genes studied, three of which were positive for the mcr-1 gene, while the other strains showed mutations in pmrA/B and phoP/Q. Typing by PFGE was performed on E.coli isolates positive for the mcr-1 gene, with the objective of verifying the genetic diversity found among them. Eighteen genetic profiles were identified, without a main clone...(AU)