Infant Mouse Model for the Study of Shedding and Transmission during Streptococcus pneumoniae Monoinfection
M Ammar Zafar1, Masamitsu Kono2, Yang Wang3
1Department of Microbiology, New York University, New York, New York, USA.
Abstract:
One of the least understood aspects of the bacterium Streptococcus pneumoniae (pneumococcus) is its transmission from host to host, the critical first step in both the carrier state and the disease state. To date, transmission models have depended on influenza A virus coinfection, which greatly enhances pneumococcal shedding to levels that allow acquisition by a new host. Here, we describe an infant mouse model that can be utilized to study pneumococcal colonization, shedding, and transmission during bacterial monoinfection. Using this model, we demonstrated that the level of bacterial shedding is highest in pups infected intranasally at age 4 days and peaks over the first 4 days postchallenge. Shedding results differed among isolates of five different pneumococcal types. Colonization density was found to be a major factor in the level of pneumococcal shedding and required expression of capsule. Transmission within a litter occurred when there was a high ratio of colonized "index" pups to uncolonized "contact" pups. Transmission was observed for each of the well-colonizing pneumococcal isolates, with the rate of transmission proportional to the level of shedding. This model can be used to examine bacterial and host factors that contribute to pneumococcal transmission without the effects of viral coinfection.
Insights
A new infant mouse model reveals Streptococcus pneumoniae transmission dynamics during bacterial monoinfection. This study highlights colonization density and capsule expression as key factors in pneumococcal shedding and host-to-host spread.
Area of Science:
- Microbiology
- Infectious Diseases
- Bacterial Pathogenesis
Background:
- Streptococcus pneumoniae (pneumococcus) transmission is poorly understood.
- Existing models rely on influenza A virus coinfection, complicating the study of bacterial monoinfection dynamics.
Purpose of the Study:
- To develop and utilize an infant mouse model for studying pneumococcal colonization, shedding, and transmission during bacterial monoinfection.
- To identify factors influencing pneumococcal transmission independent of viral coinfection.
Main Methods:
- Establishment of an infant mouse model for intranasal challenge with Streptococcus pneumoniae.
- Quantification of bacterial shedding and colonization levels over time.
- Assessment of transmission rates within litters based on colonization status and shedding levels.
Main Results:
- Bacterial shedding was highest in 4-day-old pups, peaking within 4 days post-infection.
- Colonization density, requiring capsule expression, was a major determinant of shedding levels.
- Transmission occurred when a high ratio of colonized pups to uncolonized pups was present, with transmission rates proportional to shedding levels.
Conclusions:
- The infant mouse model allows for the study of pneumococcal transmission without viral coinfection effects.
- Colonization density and capsule expression are critical for pneumococcal shedding and subsequent transmission.
- Host and bacterial factors influencing pneumococcal transmission can be investigated using this model.
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