Spore-forming bacteria include the devastating human pathogen Clostridioides difficile, the food spoilage pathogen Bacillus cereus and the bioterrorism agent Bacillus anthracis. Spores are the infectious particles of these pathogens and their resistant structure makes their eradication difficult. Their persistence properties enable the spread of disease, resulting in fatalities and economic devastation in health care settings, the food industry and public spaces in the case of weaponised anthrax. Despite this major burden, there are no strategies preventing spore production.
C. difficile is of considerable medical interest due to the disease burden and global challenge of managing the consequences of infection. Spores are a crucial mediator of C. difficile disease initiation, dissemination and re-infection and are highly resistant to current therapeutics.
Here we report the novel finding that cephamycin antibiotics can directly impact C. difficile spore production by inactivating spore-specific proteins. Through TEM imaging we observed that cephamycins block early sporulation stages. We found that this sporulation inhibition phenotype is generic using the spore-forming pathogens Paeniclostridium sordellii and B. cereus, a close relative of B. anthracis, confirming that cephamycins have broad applicability in anti-sporulation strategies.
The major anti-sporulation molecular target of the cephamycins was identified as a spore-specific penicillin-binding protein, SpoVD. Sporulation assays using a spoVD mutant confirmed its essential role in sporulation. SpoVD is found in other spore-forming bacteria, including B. anthracis and B. cereus. Through our binding assays we showed that the cephamycins target SpoVD in these pathogens.
Of clinical relevance, we found that co-treatment of mice with the cephamycin, cefotetan and the current primary C. difficile treatment vancomycin prevented disease re-infection. Our findings could therefore directly and immediately impact C. difficile infection treatment. Importantly, our results also provide new insights into disease prevention through targeting of the sporulation process, for the first time for any spore-forming pathogen. They also provide evidence of potential new anti-sporulation targets that could significantly advance drug development for other important spore-forming pathogens.