Impact of Atrazine Exposure on the Microbial Community Structure in a Brazilian Tropical Latosol Soil.

Atrazine is a triazine herbicide that is widely used to control broadleaf weeds. Its widespread use over the last 50 years has led to the potential contamination of soils, groundwater, rivers, and lakes. Its main route of complete degradation is via biological means, which is carried out by soil microbiota using a 6-step pathway. The aim of the present study was to investigate whether application of atrazine to soil changes the soil bacterial community. We used 16S rRNA gene sequencing and qPCR to elucidate the microbial community structure and assess the abundance of the atrazine degradation genes atzA, atzD, and trzN in a Brazilian soil. The results obtained showed that the relative abundance of atzA and trzN, encoding triazine-initiating metabolism in Gram-negative and -positive bacteria, respectively, increased in soil during the first weeks following the application of atrazine. In contrast, the abundance of atzD, encoding cyanuric acid amidohydrolase-the fourth step in the pathway-was not related to the atrazine treatment. Moreover, the overall soil bacterial community showed no significant changes after the application of atrazine. Despite this, we observed increases in the relative abundance of bacterial families in the 4th and 8th weeks following the atrazine treatment, which may have been related to higher copy numbers of atzA and trzN, in part due to the release of nitrogen from the herbicide. The present results revealed that while the application of atrazine may temporarily increase the quantities of the atzA and trzN genes in a Brazilian Red Latosol soil, it does not lead to significant and long-term changes in the bacterial community structure.

Draft genome sequence of a multidrug-resistant CTX-M-65-producing Escherichia coli ST156 colonizing a giant anteater (Myrmecophaga tridactyla) in a Zoo.

OBJECTIVES: This study aimed to report the draft genome sequence of a multidrug-resistant (MDR) Escherichia coli colonizing a giant anteater (Myrmecophaga tridactyla) in a Brazilian Zoo. METHODS: The genome was sequenced using the Illumina MiSeq Platform and de novo genome assembly was performed using SPAdes v. 3.9. The draft genome sequence was annotated using NCBI Prokaryotic Genome Annotation Pipeline. Antibiotic resistance genes, virulence genes, sequence type, serotype and plasmid incompatibility groups were identified using tools from the Center for Genomic Epidemiology. RESULTS: The genome presented 4970 coding sequences and a GC content of 50.2%. Several antimicrobial resistance genes associated with resistance to ß-lactams (blaTEM-1A and blaCTX-M-65), aminoglycosides [aph(6)-ld, aph(3″)-lb, aph(4)-la, aac(3)-lVa, aadA1 and aadA2], tetracyclines (tetB), sulphonamides (sul2 and sul3), trimethoprim (dfrA8 and dfrA12) and phenicols (floR and cmlA1) were identified. Moreover, mutations in quinolone resistance-determining regions (QRDR) were found. This E. coli isolate also presented virulence genes and belonged to serotype ONT:H25 and ST156 (CC156). CONCLUSION: This is the first report of a draft genome sequence of a CTX-M-65-producing E. coli ST156 obtained from a zoo animal, which can be used by genomic surveillance platforms, in order to track transmission dynamics of extended-spectrum ß-lactamase (ESBL)-producing E. coli at the human-animal interface.

Characterization of IcmF of the type VI secretion system in an avian pathogenic Escherichia coli (APEC) strain.

The intracellular multiplication factor (IcmF) protein is a component of the recently described type VI secretion system (T6SS). IcmF has been shown to be required for intra-macrophage replication and inhibition of phagosome-lysosome fusion in Legionella pneumophila. In Vibrio cholerae it is involved in motility, adherence and conjugation. Given that we previously reported that two T6SS genes (hcp and clpV) contribute to the pathogenesis of a septicaemic strain (SEPT362) of avian pathogenic Escherichia coli (APEC), we investigated the function of IcmF in this strain. Further elucidation of the virulence mechanisms of APEC is important because this pathogen is responsible for financial losses in the poultry industry, and is closely related to human extraintestinal pathogenic E. coli (ExPEC) strains, representing a potential zoonotic risk, as well as serving as a reservoir of virulence genes. Here we show that an APEC icmF mutant has decreased adherence to and invasion of epithelial cells, as well as decreased intra-macrophage survival. The icmF mutant is also defective for biofilm formation on abiotic surfaces. Additionally, expression of the flagella operon is decreased in the icmF mutant, leading to decreased motility. The combination of these phenotypes culminates in this mutant being altered for infection in chicks. These results suggest that IcmF in APEC may play a role in disease, and potentially also in the epidemiological spread of this pathogen through enhancement of biofilm formation.