Abstract
BackgroundMultifocal spherical nonstaining cavities and gram-positive, rod-shaped, and endospore-forming bacteria were found in the liver of a sow that died suddenly. Clostridium novyi type B was identified and isolated from the sudden death case, and the isolate was characterized by molecular analyses and bioassays in the current study.ResultsC. novyi was isolated from the liver of a sow that died suddenly and was confirmed as C. novyi type B by differential PCR. The C. novyi isolate fermented glucose and maltose and demonstrated lecithinase activity, and the cell-free culture supernatant of the C. novyi isolate exhibited cytotoxicity toward Vero cells, demonstrating that the isolate produces toxins. In addition, whole-genome sequencing of the C. novyi isolate was performed, and the complete sequences of the chromosome (2.29 Mbp) and two plasmids (134 and 68 kbp) were identified for the first time. Based on genome annotation, 7 genes were identified as glycosyltransferases, which are known as alpha toxins; 23 genes were found to be related to sporulation; 12 genes were found to be related to germination; and 20 genes were found to be related to chemotaxis.ConclusionC. novyi type B was isolated from a sow in a sudden death case and confirmed by biochemical and molecular characterization. Various virulence-associated genes were identified for the first time based on whole-genome sequencing.
Highlights
Multifocal spherical nonstaining cavities and gram-positive, rod-shaped, and endospore-forming bacteria were found in the liver of a sow that died suddenly
Isolation of the C. novyi isolate After 72 h of anaerobic incubation, colonies showing irregular shapes with unclear borders appeared on agar media, and gram-positive, rod-shaped, endosporeforming bacteria were identified in the colonies (Fig. 1a and b)
Differential PCR was conducted on the DNA extracted from a single colony, which confirmed the isolate as C. novyi type B [14]
Summary
Multifocal spherical nonstaining cavities and gram-positive, rod-shaped, and endospore-forming bacteria were found in the liver of a sow that died suddenly. C. novyi is a grampositive, noncapsulated, motile obligatory anaerobe that produces endospores to resist unfavorable environments [1, 5]. Based on the toxins they produce, C. novyi are classified into four types: A, B, C and D. C. novyi type A produces alpha, gamma, delta and epsilon toxins. C. novyi type B produces alpha, beta, and zeta toxins, while type C produces gamma toxin [2, 6, 7]. C. novyi type D is considered to be a different species, Clostridium haemolyticum, because it does not produce alpha toxin and because the disease that it causes is different from those caused by types A and B [8]. C. novyi type A is frequently involved in gas gangrene infections in humans and animals, while type B is the etiological agent of
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