Understanding pathogenicity of Streptococcus mitis in immuno-compromised individuals
Antimicrobial resistance is one of the most important threats to global public health. It complicates treatment of infections caused by bacteria, viruses, parasites and fungi and threatens many aspects of modern medicine, including cancer therapy. Research focusing on understanding bacterial pathogenicity can result in novel approaches to prevent and treat bacterial infections with a potential benefit of reducing the use of conventional antibiotics, reserving their use for serious drug-resistant infections. Commensal microbes normally colonize the human body without producing disease, but can cause serious infections in immunocompromised individuals. The purpose of this study is to improve our understanding of the pathogenicity of the human opportunistic pathogen Streptococcus mitis (S. mitis).
The use of mice is unavoidable in this study, but we have selected the number of mice (99 Balb/c mice in total) in accordance with previous research and aimed to reduce the number of animals used while maintaining a sufficient number for statistically significant results. The experiment will be carried out in three independent replicates. Additionally, we will begin with a pilot study to determine the proper dose, which will significantly decrease the number of animals needed in the long term. The mice will not suffer severely from the treatment, but will contract a systemic infection with S. mitis, which will induce discomfort for up to 7 days. To ensure minimal suffering, the mice will be checked twice daily and scored according to the attached scoring sheet and proper measures will be taken depending on the score of each animal.
This study will increase our understanding of the pathogenicity of opportunistic pathogens in general and S. mitis specifically. The results can help the development of novel approaches to prevent or treat bacterial infections.
The use of mice is unavoidable in this study, but we have selected the number of mice (99 Balb/c mice in total) in accordance with previous research and aimed to reduce the number of animals used while maintaining a sufficient number for statistically significant results. The experiment will be carried out in three independent replicates. Additionally, we will begin with a pilot study to determine the proper dose, which will significantly decrease the number of animals needed in the long term. The mice will not suffer severely from the treatment, but will contract a systemic infection with S. mitis, which will induce discomfort for up to 7 days. To ensure minimal suffering, the mice will be checked twice daily and scored according to the attached scoring sheet and proper measures will be taken depending on the score of each animal.
This study will increase our understanding of the pathogenicity of opportunistic pathogens in general and S. mitis specifically. The results can help the development of novel approaches to prevent or treat bacterial infections.
Etterevaluering
We classify the procedures as severe, cf. the Regulation annex B.
The systemic infection will cause discomfort for up to 7 days. The animals will be followed up closely with regards to specific clinical signs.
All projects involving severe procedures must be retrospectively assessed by the Norwegian Food Safety Authority.
The systemic infection will cause discomfort for up to 7 days. The animals will be followed up closely with regards to specific clinical signs.
All projects involving severe procedures must be retrospectively assessed by the Norwegian Food Safety Authority.
Begrunnelse for etterevalueringen
Research focusing on understanding bacterial pathogenicity can result in novel approaches to prevent and treat bacterial infections with a potential benefit of reducing the use of conventional antibiotics.
The purpose of this study has been to increase the knowledge of the pathogenicity of Streptococcus mitis (S. mitis), particularly the role of the cyclic di-adenosine monophosphate (c-di-AMP) signaling system.
The experimenters were unable to establish a progressive bacterial infection in the pilot study, which was required to determine the role of c-di-AMP signalling in S. mitis pathogenesis. However, information gained in the pilot study suggested that the study would be fruitful with small alterations to the experimental set-up and goals. Instead of using signs of severe disease as a read-out, the experimenters decided to use bacterial survival in the cardiovascular system, liver and spleen as read-out. This would allow them to determine the role of the c-di-AMP signalling system in the ability of S. mitis to survive in blood and organs of immunocompromised mice, and this is a feature that is essential for establishment of infection. The experimenters were planning on performing the main experiment with these changes during the spring, but the Covid-19 pandemic and the concomitant shut-down disrupted these plans.
Only 40 of the planned 99 animals were used. The study was delayed due to optimization of parameters in vitro between the pilot part and the main experiment, and due to the Covid-19 pandemic, the study was stopped.
To acheive the aims of the study, the score sheet would have to be altered to allow greater variation in body weight, or include a time element, for example 10-15% weight loss sustained for 24 hours.
The experiment has allowed the experimenters to gain information on the dose of bacteria required to make animals sick, and they have learned that the experimental set-up has to be altered. Instead of using animals showing signs of severe disease as a result of progressive infection as a read-out, they will use occurrence of bacteria in certain key organs (spleen, heart, liver) as read-out. The study has therefore provided important information that will be utilized in the design of a follow-up experiment where the experimenters will assess the ability of their mutants to survive in the cardiovascular system, liver and spleen. This is relevant for the bacteria used in this study since they are known to cause blood stream infections and endocarditis.
The purpose of this study has been to increase the knowledge of the pathogenicity of Streptococcus mitis (S. mitis), particularly the role of the cyclic di-adenosine monophosphate (c-di-AMP) signaling system.
The experimenters were unable to establish a progressive bacterial infection in the pilot study, which was required to determine the role of c-di-AMP signalling in S. mitis pathogenesis. However, information gained in the pilot study suggested that the study would be fruitful with small alterations to the experimental set-up and goals. Instead of using signs of severe disease as a read-out, the experimenters decided to use bacterial survival in the cardiovascular system, liver and spleen as read-out. This would allow them to determine the role of the c-di-AMP signalling system in the ability of S. mitis to survive in blood and organs of immunocompromised mice, and this is a feature that is essential for establishment of infection. The experimenters were planning on performing the main experiment with these changes during the spring, but the Covid-19 pandemic and the concomitant shut-down disrupted these plans.
Only 40 of the planned 99 animals were used. The study was delayed due to optimization of parameters in vitro between the pilot part and the main experiment, and due to the Covid-19 pandemic, the study was stopped.
To acheive the aims of the study, the score sheet would have to be altered to allow greater variation in body weight, or include a time element, for example 10-15% weight loss sustained for 24 hours.
The experiment has allowed the experimenters to gain information on the dose of bacteria required to make animals sick, and they have learned that the experimental set-up has to be altered. Instead of using animals showing signs of severe disease as a result of progressive infection as a read-out, they will use occurrence of bacteria in certain key organs (spleen, heart, liver) as read-out. The study has therefore provided important information that will be utilized in the design of a follow-up experiment where the experimenters will assess the ability of their mutants to survive in the cardiovascular system, liver and spleen. This is relevant for the bacteria used in this study since they are known to cause blood stream infections and endocarditis.