Antibiotics kill most of the parasites that people carry in their bodies and reduce the chances of transmission from person to person. There are over 2,000 different parasites that can infect humans, but only a few are resistant to common antibiotics. Most other parasites are also resistant to some antibiotic medications. Some parasitic diseases, like the tapeworm or tapeworm eggs, are difficult to treat because they are so numerous and difficult to find in the body. Some parasites are resistant to many antibiotics. Some are not. When parasites are resistant, they can cause infections and the human body can no longer fight the infection. When an antibiotic is used on a parasite it doesn't necessarily stop the infection. Some infections go away, but then the parasite will start back up. If the parasite is resistant to the antibiotic, it may go from being a simple parasite that is just causing a mild infection to a more serious disease. Some people will find out they are being treated for tapeworms and other parasites after they have been diagnosed with tapeworm. If an antibiotic is not working, there is no longer anything in the human body to help it fight the infection. I hope this is clear.