Nonpathogens are usually harmless microbes that inhabit a living organism, such as Staphylococcus aureus and candida. Some nonpathogen microbes are bacteria that can be beneficiary for the human organism, such as lactic acid bacteria. Most nonpathogenic bacteria, lactococci and lactic acid bacteria, come from foods, such as dairy products, meat and some vegetables. These are also known as gram-positive bacteria and probiotics.
Pathogens, on the other hand, are bacteria, germs, parasites and viruses that cause infections and diseases. However, since the late 19th century, there has been a debate on how harmless some nonpathogen microbes really are. According to BMC Biology, the same microbe may exist in pathogenic and nonpathogenic states. In an individual with a deficient immune system, a nonpathogenic microbe may become an opportunistic pathogen, activating the bad genes in microbes that may then cause serious disease.
As of 2014, scientists continue to research the causes that can make a nonpathogen become a pathogen microbe. Pathogenic microbes often develop to become antibiotic resistant. According to BMC, antibiotics and surgery make an individual more vulnerable and may trigger the development of a pathogenic microbe that causes infections or disease. Staphylococcus is a microbe that often becomes a pathogen that causes hospital-acquired infections.