Genome sequencing is revolutionizing clinical microbiology and our understanding of infectious diseases. Previous studies have largely relied on the sequencing of a single isolate from each individual. However, it is not clear what degree of bacterial diversity exists within, and is transmitted between individuals. Understanding this ‘cloud of diversity’ is key to accurate identification of transmission pathways. Here, we report the deep sequencing of methicillin-resistant Staphylococcus aureus among staff and animal patients involved in a transmission network at a veterinary hospital. We demonstrate considerable within-host diversity and that within-host diversity may rise and fall over time. Isolates from invasive disease contained multiple mutations in the same genes, including inactivation of a global regulator of virulence and changes in phage copy number. This study highlights the need for sequencing of multiple isolates from individuals to gain an accurate picture of transmission networks and to further understand the basis of pathogenesis.

Current staging of canine mast cell tumours (MCTs) practiced by many veterinarians involves a minimum of lymph node (LN) assessment, abdominal ultrasound and thoracic radiography. Historically, some have advocated buffy coat and bone marrow evaluation. Two hundred and twenty dogs with MCT seen at a referral clinic were staged using LN palpation/cytology, thoracic radiography and abdominal ultrasound. The utility of each method was evaluated by considering prevalence of spread and future behaviour. At presentation, 30.9% of dogs had metastases to the local LN; 6.8% of all the dogs also had distant metastases. No dog had or developed distant metastasis in the absence of LN metastasis. No dog had convincing evidence of pulmonary metastasis. In this series, the local LN was sentinel to metastasis and in the absence of local LN metastasis, the utility of further staging was low. Thoracic radiography was not useful in the staging of canine MCT.

This retrospective case series evaluates survival outcome of 94 dogs with high metastatic risk mast cell tumours (MCT). Patients were treated with a cytotoxic chemotherapy protocol or the tyrosine kinase inhibitor masitinib, in the presence of gross disease or as an adjunct to surgical resection of the primary tumour. In patients presenting with metastatic disease, surgical resection of the primary tumour with adjunctive therapy with any chemotherapy incurred a significant survival advantage [median survival time (MST): 278 days] compared to patients receiving chemotherapy without surgical excision of the primary tumour (MST: 91 days, P < 0.0001). Patients with a surgically excised Patnaik grade II tumour and high Ki-67 in the absence of metastatic disease treated with vinblastine and prednisolone showed a significantly longer survival (MST: 1946 days) than those treated with masitinib (MST: 369 days, P = 0.0037). Further prospective case-controlled clinical trials of high-risk MCTs are required to make precise evidence-based treatment decisions for individual patients.