Introduction

Bacillus cereus biovar anthracis (Bcbva) is a novel anthrax causing agent infecting animals in African rainforest areas. Human infections were not yet confirmed, but exposure is likely due to hunting and consumption of "bush meat" and was also evidenced by seroprevalence studies in humans living in affected regions.

It is still largely unknown how animals get infected with Bcbva. One route of infection might be similar to that of Bacillus anthracis (BA) via spores released into the soil by dead animals. However, also monkey species living only in trees get regularly infected by Bcbva. It was shown that carrion flies which had fed on BA-infected carcasses can contaminate leaves with their excretions and thereby transmit the disease. Indeed, also Bcbva has been confirmed in carrion flies. These flies could potentially spread Bcbva and its spores to leaves and fruits which in turn get consumed by various monkey species.

We hypothesize that Bcbva is capable of persisting and even replicating on these leaves as biofilm and thereby considerably increasing the chance of infecting animals.

Methods

In this study, we use an in vivo model with Chlorophytum comosum (Spider Plant) to reconstruct biofilm formation and persistence of Bcbva and BA on the leaf surface.

To gain insight into biofilm formation, we use confocal laser scanning and electron microscopy. Multiplication and spore formation of Bcbva are confirmed by quantification methods such as colony forming unit determination and quantitative PCR (qPCR). At last, we aim to characterize and quantify the biofilm matrix composition by labeling with specific fluorescent markers and photometric measurement.

Results

First results of confocal and electron microscopy showed biofilm formation of Bcbva and BA on leaves. Quantification with qPCR even points to Bcbva being able to multiply on the leaf surface under our model conditions.

Conclusion

Even though the project is still ongoing, first results support our hypothesis on Bcbva and BA producing biofilm on leaves. Further insight on the biofilm formation could lead to a better understanding on how this deadly disease is spreading in wildlife.