The present invention relates to the field of bacterial Surface (S)-layer proteins, in particular to compounds capable of disrupting the bacterial S-Layer, specifically the S-Layer of Bacillus anthracis. More particularly, the invention provides for single domain antibodies for diagnosis and treatment of infection caused by pathogens with an S-Layer, in particular of Bacillus anthracis infection. The invention relates to S-Layer protein binding agents inhibiting bacterial growth and interrupting S-Layer assembly, useful in the treatment of bacterial infection, more specifically treatment of anthrax disease.