An Official Outbreak Investigation of Acute Haemorrhagic Diarrhoea in Dogs in Norway Points to Providencia alcalifaciens as a Likely Cause

Pathogenic diversification of the gut commensal Providencia alcalifaciens via acquisition of a second type III secretion system

Providencia alcalifaciens is a Gram-negative bacterium found in various water and land environments and organisms, including insects and mammals. Some P. alcalifaciens strains encode gene homologs of virulence factors found in pathogenic Enterobacterales members, such as Salmonella enterica serovar Typhimurium and Shigella flexneri. Whether these genes are pathogenic determinants in P. alcalifaciens is not known. In this study, we investigated P. alcalifaciens-host interactions at the cellular level, focusing on the role of two type III secretion systems (T3SS) belonging to the Inv-Mxi/Spa family. T3SS1b is widespread in Providencia spp. and encoded on the chromosome. A large plasmid that is present in a subset of P. alcalifaciens strains, primarily isolated from diarrheal patients, encodes for T3SS1a. We show that P. alcalifaciens 205/92 is internalized into eukaryotic cells, lyses its internalization vacuole, and proliferates in the cytosol. This triggers caspase-4-dependent inflammasome responses in gut epithelial cells. The requirement for the T3SS1a in entry, vacuole lysis, and cytosolic proliferation is host cell type-specific, playing a more prominent role in intestinal epithelial cells than in macrophages or insect cells. In a bovine ligated intestinal loop model, P. alcalifaciens colonizes the intestinal mucosa and induces mild epithelial damage with negligible fluid accumulation in a T3SS1a- and T3SS1b-independent manner. However, T3SS1b was required for the rapid killing of Drosophila melanogaster. We propose that the acquisition of two T3SS has allowed P. alcalifaciens to diversify its host range, from a highly virulent pathogen of insects to an opportunistic gastrointestinal pathogen of animals.

Genome sequences of Clostridium perfringens isolated from diseased dogs

Two Clostridium perfringens isolates originating from two Norwegian dogs with acute hemorrhagic diarrhea were sequenced. Based on Illumina and Oxford Nanopore Technology sequencing, hybrid assemblies were generated, and one of the genomes was completed and closed. For both isolates, virulence genes and their genomic location have been identified.

Successful treatment of feline pancreatolithiasis associated with an ascending Providencia rettgeri infection using a novel surgical technique

A 12-year-old female spayed Domestic Shorthair cat presented with a 4-day history of lethargy, inappetence and vomiting. Physical findings included a grade 2/6 heart murmur and cranial abdominal pain on palpation. Serum biochemistry revealed elevated total bilirubin and liver enzymes activities. Abdominal ultrasound revealed multiple pancreatoliths, cholelithiasis and dilation of the pancreatic duct. During exploratory laparotomy, catheterisation of the pancreatic duct with retrograde and orthograde flushing to remove the pancreatoliths was performed via a distal enterotomy and proximal left apical partial pancreatectomy respectively. Catheterisation and flushing of the common bile duct were performed to confirm patency prior to cholecystectomy. Bacterial culture of pancreatoliths, pancreatic tissue and bile grew a heavy, pure growth of Providencia rettgeri. Fluorescent immunostaining histopathology revealed clusters of rod-shaped bacteria within the pancreatic parenchyma and gall bladder mucosa. The cat received pradofloxacin for two weeks. She made a complete recovery and remained well at a six-month follow-up.

Enteropathogenic Providencia alcalifaciens: A Subgroup of P. alcalifaciens That Causes Diarrhea

Despite being considered a normal flora, Providencia alcalifaciens can cause diarrhea. In a previous study, strain 2939/90, obtained from a diarrheal patient, caused invasion and actin condensation in mammalian cells, and diarrhea in a rabbit model. Four TnphoA mutants of 2939/90 produced negligible invasion and actin condensation in mammalian cells. Now, the parent strain and the mutants have been sequenced to locate TnphoA insertion sites and determine the effect on virulence. A TnphoA insertion was detected in the type three secretion system (T3SS) locus on a large plasmid and not in a T3SS locus on the chromosome. In 52 genomes of P. alcalifaciens surveyed, the chromosomal T3SS locus was present in all strains, including both P. alcalifaciens genomic clades, which we classified as group A and group B. Plasmid T3SS was present in 21 of 52 genomes, mostly in group A genomes, which included isolates from an outbreak of hemorrhagic diarrhea in dogs. The TnphoA insertion only in the plasmid T3SS locus affected the invasion phenotype, suggested that this locus is critical for causation of diarrhea. We conclude that a subgroup of P. alcalifaciens that possesses this plasmid-mediated T3SS is an enteric pathogen that can cause diarrheal disease.

Can shelter dog observers score behavioural expressions consistently over time?

A substantial number of dogs live in animal shelters worldwide. Stressors within the shelter environment can compromise their welfare, and scientific evaluations of feasible welfare assessment methods are therefore needed. Qualitative Behaviour Assessment (QBA) is a "whole-animal" approach used to assess welfare by observing animals' expressive behaviour. To investigate whether observers can score dogs' behavioural expressions consistently over time, this study replicated and extended previous research, by evaluating intra- and inter-observer reliability of QBA based on video recordings of shelter dogs. In Part I, nine veterinary nurse students received theoretical and practical training, and then scored 12 2 min video recordings of shelter dogs using a fixed list of behavioural descriptors. Three of the students undertook further practice and calibration using direct observations of dog behaviour in a local shelter. In Part II, the videos from Part I were scored by these three observers a second time, 15 months later. QBA data were analysed using principal component analysis (PCA), and reliability was assessed using Kendall's coefficient of concordance (W). In Part I, the inter-observer reliability was high for both components (0.78 for PC1 and 0.85 for PC2). In Part II, the inter-observer reliability was very high and moderate for PC1 and PC2, respectively (0.90 for PC1 and 0.65 for PC2). The intra-observer reliability was high for both components (W ≥ 0.86). Our results indicate that the fixed list of behavioural descriptors for shelter dogs can be used reliably when assessing videos, and that observers can score dogs' behavioural expressions consistently after a break of 15 months following the initial assessment. Nevertheless, the reduction in inter-observer-reliability of PC2 in Part II can indicate that some retraining and calibration may be required to avoid observer drift.

Closed Genome Sequences of Providencia alcalifaciens Isolates from Dogs

Eight Providencia alcalifaciens isolates from eight different dogs in Norway with acute hemorrhagic diarrhea were sequenced. Based on Illumina and Oxford Nanopore Technologies sequencing, all of the genomes were complete and closed after hybrid assembly.