Molecular ecology and risk factors for third-generation cephalosporin-resistant Escherichia coli carriage by dogs living in urban and nearby rural settings

OBJECTIVES: To compare faecal third-generation cephalosporin-resistant (3GC-R) Escherichia coli isolates from dogs living in a city and in a rural area ∼30 km away; to compare isolates from dogs, cattle and humans in these regions; and to determine risk factors associated with 3GC-R E. coli carriage in these two cohorts of dogs. METHODS: Six hundred dogs were included, with faecal samples processed to recover 3GC-R E. coli using 2 mg/L cefotaxime. WGS was by Illumina and risk factor analyses were by multivariable linear regression using the results of an owner-completed survey. RESULTS: 3GC-R E. coli were excreted by 20/303 rural and 31/297 urban dogs. The dominant canine 3GC-R ST was ST963 (bla(CMY-2)), which also accounted for 25% of CMY-2-producing E. coli in humans. Phylogenetic overlap between cattle and rural dog CTX-M-14-producing E. coli ST117 was observed as well as acquisition of pMOO-32-positive E. coli ST10 by a rural dog, a plasmid common on cattle farms in the area. Feeding raw meat was associated with carrying 3GC-R E. coli in rural dogs, but not in urban dogs, where swimming in rivers was a weak risk factor. CONCLUSIONS: Given clear zoonotic potential for resistant canine E. coli, our work suggests interventions that may reduce this threat. In rural dogs, carriage of 3GC-R E. coli, particularly CTX-M producers, was phylogenetically associated with interaction with local cattle and epidemiologically associated with feeding raw meat. In urban dogs, sources of 3GC-R E. coli appear to be more varied and include environments such as rivers

Improving Nitrofurantoin Resistance Prediction in Escherichia coli from Whole Genome Sequence by Integrating NfsA/B Enzyme Assays

Nitrofurantoin resistance in Escherichia coli is primarily caused by mutations damaging two enzymes, NfsA and NfsB. Studies based on small isolate collections with defined nitrofurantoin MICs have found significant random genetic drift in nfsA and nfsB making it extremely difficult to predict nitrofurantoin resistance from whole genome sequence (WGS) where both genes are not obviously disrupted by nonsense or frameshift mutations or insertional inactivation. Here we report a WGS survey of 200 E. coli from community urine samples, of which 34 were nitrofurantoin resistant. We characterised individual non-synonymous mutations seen in nfsA and nfsB among this collection using complementation cloning and assays of NfsA/B enzyme activity in cell extracts. We definitively identified R203C, H11Y, W212R, A112E, A112T and A122T in NfsA and R121C, Q142H, F84S, P163H, W46R, K57E and V191G in NfsB as amino acid substitutions that reduce enzyme activity sufficiently to cause resistance. In contrast, E58D, I117T, K141E, L157F, A172S, G187D and A188V in NfsA and G66D, M75I, V93A and A174E in NfsB, are functionally silent in this context. We identified that 9/166 (5.4%) of nitrofurantoin susceptible isolates were “pre-resistant”, defined as having loss of function mutations in nfsA or nfsB. Finally, using NfsA/B enzyme activity assay and proteomics we demonstrated that 9/34 (26.5%) of nitrofurantoin resistant isolates carried functionally wild-type nfsB or nfsB/nfsA. In these cases, enzyme activity was reduced through downregulated gene expression. Our biological understanding of nitrofurantoin resistance is greatly improved by this analysis, but is still insufficient to allow its reliable prediction from WGS data

Is there a place on the shelf for Aliskiren?

Increased renin-angiotensin-aldosterone system (RAAS) activity contributes to target-organ damage and increases cardiovascular risk by elevating blood pressure (BP) and through direct effects on the heart, kidneys, brain, and vascular endothelium. Pharmacologic blockade of RAAS effectively reduces BP and limits or reverses various forms of target-organ damage, including cardiac heart failure, coronary artery disease, chronic kidney disease, and left ventricular hypertrophy. Direct renin inhibitors selectively inhibit human renin and have a therapeutic potential similar to angiotensin-converting enzyme inhibitors and angiotensin II receptor blockers. Aliskiren is the only orally active direct renin inhibitor that has been approved for the treatment of hypertension and has been shown to have favorable effects on target-organ damage. It effectively reduces BP and has favorable effects on heart failure and proteinuria in diabetic patients. Additional outcome trials are needed to establish the role of this new class of antihypertensive medication in preventing cardiovascular outcomes