A number of bacteria use a class of chemical compounds called acyl-homoserine lactones (AHLs) as quorum sensing (QS) signals to coordinate their behavior at the population level, including pathogens like Pseudomonas aeruginosa. Blocking QS using antibodies is an attractive strategy for infection control as this process takes a central role in P. aeruginosa infections. Here the methods involved in the generation of high sensitivity anti-QS monoclonal antibodies from an immunized sheep phage display antibody library are described. A panel of AHL compounds conjugated to carrier proteins are used for sheep immunization and a phage display antibody library is constructed using the immune repertoire of sheep as a source of antibody genes. High sensitivity single chain antibody fragments (scFv) are isolated from the library using "smart selection strategies" and reformatted into single chain antibodies (scAbs). The resultant monoclonal antibodies: (1) recognize HSL compounds at low nanomolar concentrations; (2) have the potential to reduce virulence gene expression in P. aeruginosa; and (3) offer protection in a nematode model of infection.