Pathological Features and Genomic Characterization of an Actinobacillus equuli subsp. equuli Bearing Unique Virulence-Associated Genes from an Adult Horse with Pleuropneumonia

Maedeh Kamali; Mariano Carossino; Fabio Del Piero; Laura Peak; Maria S Mitchell; Jackie Willette; Rose Baker; Fuyong Li; Ákos Kenéz; Udeni B R Balasuriya; Yun Young Go

doi:10.3390/pathogens12020224

Pathological Features and Genomic Characterization of an Actinobacillus equuli subsp. equuli Bearing Unique Virulence-Associated Genes from an Adult Horse with Pleuropneumonia

Pathogens. 2023 Jan 31;12(2):224. doi: 10.3390/pathogens12020224.

Authors

Maedeh Kamali¹, Mariano Carossino^{2

3}, Fabio Del Piero^{2

3}, Laura Peak², Maria S Mitchell², Jackie Willette⁴, Rose Baker⁴, Fuyong Li¹, Ákos Kenéz¹, Udeni B R Balasuriya^{2

3}, Yun Young Go¹

Affiliations

¹ Department of Infectious Diseases and Public Health, Jockey Club College of Veterinary Medicine, City University of Hong Kong, Hong Kong SAR, China.
² Louisiana Animal Disease Diagnostic Laboratory, School of Veterinary Medicine, Louisiana State University, Baton Rouge, LA 70803, USA.
³ Department of Pathobiological Sciences, School of Veterinary Medicine, Louisiana State University, Baton Rouge, LA 70803, USA.
⁴ Veterinary Teaching Hospital and Department of Veterinary Clinical Sciences, School of Veterinary Medicine, Louisiana State University, Baton Rouge, LA 70803, USA.

Abstract

Actinobacillus equuli subsp. equuli is the etiological agent of sleepy foal disease, an acute form of fatal septicemia in newborn foals. A. equuli is commonly found in the mucous membranes of healthy horses' respiratory and alimentary tracts and rarely causes disease in adult horses. In this study, we report a case of a 22-year-old American Paint gelding presenting clinical signs associated with an atypical pattern of pleuropneumonia subjected to necropsy. The gross and histopathological examinations revealed a unilateral fibrinosuppurative and hemorrhagic pleuropneumonia with an infrequent parenchymal distribution and heavy isolation of A. equuli. The whole genome sequence analysis indicated that the isolate shared 95.9% homology with the only other complete genome of A. equuli subsp. equuli available in GenBank. Seven virulence-associated genes specific to the isolate were identified and categorized as iron acquisition proteins, lipopolysaccharides (LPS), and capsule polysaccharides. Moreover, four genes (glf, wbaP, glycosyltransferase family 2 protein, and apxIB) shared higher amino acid similarity with the invasive Actinobacillus spp. than the reference A. equuli subsp. equuli genome. Availability of the whole genome sequence will allow a better characterization of virulence determinants of A. equuli subsp. equuli, which remain largely elusive.

Keywords: Actinobacillus equuli subsp. equuli; equine actinobacillosis; whole genome sequencing.

Grants and funding

Yun Young Go is supported by start-up (9610462) and intramural (APRC-9610530) funds from the City University of Hong Kong, Hong Kong SAR, China. Mariano Carossino was also supported by start-up funds (PG009641) from the School of Veterinary Medicine, LSU, Louisiana, USA. In addition, support was also obtained from F.D.A. Veterinary Laboratory Investigation and Response Network (Vet-LIRN; grant number AWD-47109-1/U18FD006442) awarded to Udeni Balasuriya and the Louisiana Animal Disease Diagnostic Laboratory (PG009095).