Polyreactive antibodies are seen to have somewhat broad reactivity against both gram-positive and gram-negative bacteria, but can have drastically varying levels of affinity for different species, or no affinity at all for some species. For bacterial detection, more comprehensive and consistent results may be obtained by using antibodies against gram-positive or gram-negative bacteria individually.
For detecting gram-positive bacteria, anti-gram positive antibodies that are reactive against LTA can be used. LTA (lipoteichoic acid) is found in the cell walls of gram-positive bacteria. For gram-negative bacteria, one option is to use anti-gram negative endotoxin antibodies, since endotoxins are present in the cell walls of most gram-negative bacteria.
However, if wanting to simply visualize bacteria without the use of antibodies, an option is to perform gram-staining.