Corynebacterium oculi-related bacterium may act as a pathogen and carrier of antimicrobial resistance genes in dogs: a case report.

BACKGROUND: The genus Corynebacterium comprises well-known animal and human pathogens as well as commensals of skin and mucous membranes. Species formerly regarded as contaminants are increasingly being recognized as opportunistic pathogens. Corynebacterium oculi has recently been described as a human ocular pathogen but has so far not been reported in dogs. CASE PRESENTATION: Here we present two cases of infection with a novel Corynebacterium sp., a corneal ulcer and a case of bacteriuria. The two bacterial isolates could not be identified by MALDI-TOF MS. While 16 S rRNA gene (99.3% similarity) and rpoB (96.6% identity) sequencing led to the preliminary identification of the isolates as Corynebacterium (C.) oculi, whole genome sequencing revealed the strains to be closely related to, but in a separate cluster from C. oculi. Antimicrobial susceptibility testing showed high minimal inhibitory concentrations of lincosamides, macrolides, tetracycline, and fluoroquinolones for one of the isolates, which also contained an erm(X) and tet-carrying plasmid as well as a nonsynonymous mutation leading to an S84I substitution in the quinolone resistance determining region of GyrA. CONCLUSIONS: While the clinical signs of both dogs were alleviated by antimicrobial treatment, the clinical significance of these isolates remains to be proven. However, considering its close relation with C. oculi, a known pathogen in humans, pathogenic potential of this species is not unlikely. Furthermore, these bacteria may act as reservoir for antimicrobial resistance genes also in a One Health context since one strain carried a multidrug resistance plasmid related to pNG3 of C. diphtheriae.

CNGB3 Missense Variant Causes Recessive Achromatopsia in Original Braunvieh Cattle.

Sporadic occurrence of inherited eye disorders has been reported in cattle but so far pathogenic variants were found only for rare forms of cataract but not for retinopathies. The aim of this study was to characterize the phenotype and the genetic aetiology of a recessive form of congenital day-blindness observed in several cases of purebred Original Braunvieh cattle. Electroretinography in an affected calf revealed absent cone-mediated function, whereas the rods continue to function normally. Brain areas involved in vision were morphologically normal. When targeting cones by immunofluorescence, a decrease in cone number and an accumulation of beta subunits of cone cyclic-nucleotide gated channel (CNGB3) in the outer plexiform layer of affected animals was obvious. Achromatopsia is a monogenic Mendelian disease characterized by the loss of cone photoreceptor function resulting in day-blindness, total color-blindness, and decreased central visual acuity. After SNP genotyping and subsequent homozygosity mapping with twelve affected cattle, we performed whole-genome sequencing and variant calling of three cases. We identified a single missense variant in the bovine CNGB3 gene situated in a ~2.5 Mb homozygous genome region on chromosome 14 shared between all cases. All affected cattle were homozygous carriers of the p.Asp251Asn mutation that was predicted to be deleterious, affecting an evolutionary conserved residue. In conclusion, we have evidence for the occurrence of a breed-specific novel CNGB3-related form of recessively inherited achromatopsia in Original Braunvieh cattle which we have designated OH1 showing an allele frequency of the deleterious allele of ~8%. The identification of carriers will enable selection against this inherited disorder. The studied cattle might serve as an animal model to further elucidate the function of CNGB3 in mammals.

Cross talk among cells promoting anterior chamber-associated immune deviation.

The visual axis of the eye focuses light images precisely on the retina. The retina is intolerant of distortion that might be induced by innate or immune inflammation. In addition, the corneal endothelium and the neurosensory retina are unable to regenerate if injured by trauma or inflammation. Within the environment of this visual organ a phenomenon called ocular immune privilege provides the eye with the necessary immune protection against infectious agents by allowing the expression of the least deleterious immune effector mechanisms. Moreover, the mechanisms of immune privilege are multiple, overlapping, and include both active and passive suppression of innate and immune inflammation. At the very basis of an effective immune response are cellular interactions and their cross talk. Central to the ability of cells to communicate are the intercellular channels that are established to isolate signals and movement of proteins between cells. Within this secure nano-environment, cells signal each other and even exchange proteins. Studies reviewed here are centered on knowledge and exploration of the tolerogenic synapse rather than the immunogenic synapse. The unique cells (invariant natural killer T cells, F4/80+ antigen-presenting cells, and T and B lymphocytes) that cluster within the marginal zone following injection of antigen in the anterior chamber (AC) express a phenotype of cell surface molecules that that seem to be uniquely critical for the development of AC-associated immune deviation. How these cell surface molecules behave during the cellular interactions that result in the development of regulatory T cells and peripheral tolerance induced through the eye is discussed.

Clinical experience with butyl-2-cyanoacrylate adhesive in the management of canine and feline corneal disease.

PURPOSE: To examine and evaluate clinical indications and postoperative outcome in a series of small animal patients in which corneal disease was managed by the application of butyl 2-cyanoacrylate adhesive. MATERIALS AND METHODS: In this retrospective study all small animal patients were identified that presented to the Royal Veterinary College, University of London over a 2-year period, in which corneal disease was managed by the application of butyl 2-cyanoacrylate. Indications for application, complicating factors prior to gluing, glue retention time, postoperative comfort, and extent of subsequent corneal reaction and scarring were noted for each case. Long-term follow-up data concerning visual and cosmetic outcome were obtained from owners and referring veterinarians. RESULTS: Thirty-seven patients (28 dogs and 9 cats), in which 39 eyes were treated, were identified. Indications for corneal gluing in this series included stromal ulceration (26/39 eyes); descemetocele (4/39 eyes); corneal laceration/foreign body (5/39 eyes); lamellar keratectomy (3/39 eyes) and superficial ulceration (1/39 eyes). At least one factor responsible for initiation, persistence or progression of the ulcer was identified in 66.7% of eyes prior to corneal gluing. These included keratomalacia; confirmed bacterial keratitis; corneal edema related to endothelial disease and keratoconjunctivitis sicca. Cyanoacrylate was generally well tolerated by patients with only 8/34 eyes demonstrating transient blepharospasm and increased lacrimation postoperatively. Retention time of cyanoacrylate varied widely from < 1 week to approximately 6 months, but was < 2 months in the majority (89%) of eyes. Exaggerated corneal vascularization was an infrequent postoperative complication, noted in only six canine eyes, and did not appear to be related to initial corneal disease, glue retention time or breed. CONCLUSIONS: Butyl 2-cyanoacrylate offers a convenient, economical and effective alternative to other treatment modalities, such as conjunctival grafts, in the management of corneal defects in canine and feline patients.