Genetic and Functional Characterization of an MCR-3-Like Enzyme-Producing Escherichia coli Isolate Recovered from Swine in Brazil.

A collection of 126 pigs was screened for carriage of colistin-resistant Enterobacteriaceae in a farm in Minas Gerais, Brazil. Out of this collection, eight colistin-resistant Escherichia coli isolates were recovered, including one from Minas Gerais State producing a new MCR-3 variant (MCR-3.12). Analysis of the lipopolysaccharide revealed that MCR-3.12 had a function similar to that of MCR-1 and MCR-2 as a result of the addition of a phosphoethanolamine group to the lipid A moiety. Genetic analysis showed that the mcr-3.12 gene was carried by an IncA/C2 plasmid and was embedded in an original genetic environment. This study reports the occurrence of the MCR-3-like determinant in South America and is the first to demonstrate the functionality of this group of enzymes as a phosphoethanolamine transferase.

Edwardsiella tarda outbreak affecting fishes and aquatic birds in Brazil.

BACKGROUND: Edwardsiella tarda infections are frequent causes of severe outbreaks in the fish farming industry besides representing possible zoonotic risks. However, naturally occurring outbreaks that affect various species besides fishes are seldom described. AIM: To report an outbreak of acute mortality caused by E. tarda affecting multiple species that inhabited a natural pond in the state of São Paulo, Brazil. MATERIALS AND METHODS: Three adult tilapias, three Mallard ducks and one Snow egret were necropsied and subjected to further microbiological tests. Gross and microscopic lesions were documented. The antibiotic susceptibility and phylogenetic similarities among fish and avian strains were also determined. The E. tarda species was confirmed through MALDI-TOF, partial sodB sequencing and phylogenetic analysis. RESULTS: Macroscopical findings between the three species included intestinal dilatation, mucosal hyperaemia and mucous to liquid contents. Common histopathology findings included acute enteritis, increased number of intraepithelial lymphocytes with bacteria adhered to the intestinal epithelium and lymphoid depletion in the spleen. E. tarda was isolated from several organs from all affected species. The phylogeny employing amplified fragment length polymorphism (AFLP) of eleven strains revealed high similarity (>90%) among the isolates regardless of the affected species or sampled organs. Ten isolates of E. tarda showed susceptibility to all tested antibiotics. CONCLUSIONS: E. tarda was identified as the cause of death of the species examined. Further studies would be necessary to determine the virulence of these strains and the possible risks regarding public health.

Listeria monocytogenes encodes a functional ESX-1 secretion system whose expression is detrimental to in vivo infection.

Bacterial pathogenicity deeply depends on the ability to secrete virulence factors that bind specific targets on host cells and manipulate host responses. The Gram-positive bacterium Listeria monocytogenes is a human foodborne pathogen that remains a serious public health concern. To transport proteins across its cell envelope, this facultative intracellular pathogen engages a set of specialized secretion systems. Here we show that L. monocytogenes EGDe uses a specialized secretion system, named ESX-1, to secrete EsxA, a homolog of the virulence determinants ESAT-6 and EsxA of Mycobacterium tuberculosis and Staphylococcus aureus, respectively. Our data show that the L. monocytogenes ESX-1 secretion system and its substrates are dispensable for bacterial invasion and intracellular multiplication in eukaryotic cell lines. Surprisingly, we found that the EssC-dependent secretion of EsxA has a detrimental effect on L. monocytogenes in vivo infection.