Neem has been known as the "village pharmacy," because it's useful against such a wide range of diseases and ailments. Neem fights pathogens at all stages of their life cycle, from eggs to larva to adult. It also helps remove the toxins released by the parasites when they die.
Extract of neem can eradicate both young roundworms, as well as their eggs. Total eradication of second-stage juvenile nematodes was found at 40% neem extract, but it took 100% of undilated neem to eradicate egg and inhibit their production.
Researchers have found a chemical compound, azadirachtin, to be an important component of neem’s effectiveness against bacteria. Azadirachtin is a phytochemical (specifically a limonoid) that is extracted from the neem seed, effective against bacteria and parasites in a number of ways.
Additionally, the nimbidin in neem seed is another chemical responsible for fighting inflammation, fungi, fever, histamines, and more. Because of these chemicals, neem has a broad-spectrum effect against bacteria.