The purpose of a throat swab culture is to detect the presence of organisms in the throat that could cause infection. For instance, the presence of group A streptococcus bacteria in your throat is a key sign that you may have strep throat.If you have a sore throat and your physician suspects that you may have strep throat or another bacterial infection, he or she may order a throat swab culture.or instance, the presence of group A streptococcus bacteria in your throat is a key sign that you may have strep throat. If you have a sore throat and your physician suspects that you may have strep throat or another bacterial infection, he or she may order a throat swab culture.