# Characterization of a Highly Toxigenic Clostridium tetani Strain from a Calf’s Castration Site

## TL;DR

A highly toxin-producing strain of Clostridium tetani was isolated from a calf in Japan, which may have implications for both animal and human health due to its strong toxin production.

## Contribution

The discovery of a highly toxigenic C. tetani strain in a calf provides new insights into tetanus pathogenesis in low-susceptibility hosts.

## Key findings

- The strain OPLHC-2022-Y645 showed the highest tetanus toxin production among tested isolates.
- Genomic analysis linked the strain to a previously reported high toxin-producing lineage in Japan.
- The calf's rapid tetanus progression may be due to the strain's strong toxin production.

## Abstract

We have isolated a high tetanus toxin-producing strain of Clostridium tetani from a calf. Due to their low sensitivity to tetanus toxin, calves may only develop tetanus when the bacteria produce exceptionally large amounts of toxin. If this hypothesis is correct, then strains with high toxin production would be selectively favored in low-susceptibility mammals such as calves and cattle, particularly if the disease were to become widespread. This has significant implications for human clinical settings as well. An increase in cases caused by these highly productive strains could diminish the efficacy of immunoglobulin antitoxin therapy.

Background: This case report describes a calf that underwent castration at a Japanese livestock farm and subsequently died after developing clinical signs of tetanus, including muscle rigidity and difficulty standing. Methods: A postmortem examination was performed, focusing on indurated lesions at the castration site, which were subjected to bacteriological and genetic analyses. Results: Clostridium tetani strain OPLHC-2022-Y645 was isolated from the purulent lesion. Whole-genome sequencing revealed a close genetic relationship to strain KHSU-254310-026, which belongs to the high toxin-producing lineage Clade 1-3 previously reported in Japan. Immunoassays demonstrated that OPLHC-2022-Y645 exhibited the highest tetanus toxin production among isolates tested to date. Conclusions: Whole-genome sequencing and immunoassay findings suggest that the rapid progression of tetanus in this calf could be associated with the strong toxin-producing capacity of the OPLHC-2022-Y645 strain.