Comparative analysis of an mcr-4 Salmonella enterica subsp. enterica monophasic variant of human and animal origin.

Objectives: In this study we compared the recently described mcr-4-positive Salmonella enterica monophasic variant, isolated in 2016 in two Italian patients affected by gastroenteritis, with the first mcr-4-positive Salmonella isolate identified in 2013 in a pig at slaughter in Italy. Methods: WGS of the two Salmonella isolates of human origin was performed using a MiSeq instrument (Illumina). The phylogenetic analysis was performed by SNP analysis, comparing genomes of the mcr-4-positive isolates of swine and human origin with 82 Salmonella genomes downloaded from the EnteroBase Salmonella database. Complete sequences of plasmids carrying mcr-4.2 were obtained and compared. Transformation experiments were performed to transfer the mcr-4 plasmids into a colistin-susceptible Escherichia coli recipient strain. Results: Comparative genomics demonstrated that the Salmonella of swine origin did not cluster with the isolates of human origin. The mcr-4.2 gene variant identified in the Salmonella of human origin was located on a ColE-like plasmid. This plasmid showed different replication and mobilization genes with respect to those previously described in the ColE plasmid carrying the mcr-4.1 variant, identified in Salmonella of swine origin. Conclusions: The divergence in genomes, plasmids and gene variants demonstrated that there was not a unique mcr-4-positive, monophasic Salmonella lineage circulating in animals and causing gastroenteritis in humans in Italy. There was no horizontal transfer of the same plasmid among Salmonella strains of animal and human origin, but the mcr-4 gene and a fragment of the plasmid identified in the animal strain were mobilized by an IS1294 into a different ColE plasmid.

Clinical Validation of SensiTest Colistin, a Broth Microdilution-Based Method To Evaluate Colistin MICs.

The global spread of multidrug-resistant Gram-negative bacteria has led to the return of colistin for treating severe infections. Recently, different plasmid-mediated genes conferring resistance to this drug were described and reported worldwide. International committees (EUCAST/CLSI) reevaluated inconsistencies surrounding colistin antimicrobial susceptibility testing (AST), concluding that broth microdilution (BMD) should serve as the reference method for AST. The development of an accurate, reproducible commercial test based on BMD is therefore highly desirable. SensiTest Colistin (STC), a BMD-based compact 4-test panel containing the lyophilized antibiotic in 7 2-fold dilutions (0.25 to 16 µg/ml) was here compared with the EUCAST-CLSI standard reference method (BMD) and, for some isolates, with the automated Phoenix 100 system (PHX). A total of 353 bacterial strains were evaluated by two different laboratories; 137 isolates were resistant to colistin (19 were intrinsically resistant, 83 harbored the mcr-1 gene). Essential agreement (EA) between STC and BMD was obtained for 339 out of the 353 strains tested (96.0%). Overall categorical agreement was obtained for 349 out of the 353 strains analyzed (98.9%). Two major errors (MEs; 0.93%) and two very major errors (VMEs; 1.46%) were documented. STC appeared to be a simple but highly reliable test with good reproducibility even with panels stored at room temperature or at 35°C. Moreover, STC showed a good performance with strains carrying the mcr-1 gene, with a 98.8% EA. As the secondary endpoint of our study, VMEs for PHX were documented for 6 isolates (10%).

Detection of mcr-4 positive Salmonella enterica serovar Typhimurium in clinical isolates of human origin, Italy, October to November 2016.

In this study we report the detection of the recently described mcr-4 gene in two human isolates of Salmonella enterica serovar Typhimurium. The strains were isolated from faecal samples of two Italian patients with gastroenteritis, collected in 2016. The identified mcr-4 genes (variant mcr-4.2) differed from the mcr-4 gene originally described in a Salmonella strain of swine origin from Italy. Salmonella species could represent a hidden reservoir for mcr genes.

[Treating Clostridium difficile infection with faecal transplantation: donor microbiological testing]. / Terapia delle infezioni da Clostridium difficile con trapianto di feci: controlli microbiologici sul donatore.

Clostridium difficile associated diseases (CDADs) or C. difficile infections (CDIs) are increasing in incidence, severity and mortality. Among patients with CDIs, those with recurrent disease are less responsive to traditional therapies with commonly used drugs, such as metronidazole and vancomycin. Faecal microbiota transplantation is an old therapeutic procedure that has been recently proposed as a safe and effective treatment for CDI patients non-responsive to antibiotic therapy. In this paper we discuss the microbiological procedures that should be performed on faecal microbiota donors.