Broad-spectrum antibiotic estimated 10-100 trillion multiple organisms that colonize the human body. As a side-effect of therapy, antibiotics can change the body's normal microbial content by attacking indiscriminately both the pathological and naturally occurring, beneficial or harmless bacteria found in the intestines, lungs and bladder. The destruction of the body's normal bacterial flora is thought to disrupt immunity, nutrition, and lead to a relative overgrowth in some bacteria or fungi. An overgrowth of drug-resistant microorganisms can lead to a secondary infection such as "Clostridium difficile" ("C. diff") or candidiasis ("thrush"). This side-effect is more likely with the use of broad-spectrum antibiotics, given
Cavalier-Smith's system of classification distinguishes chromists from plants. Cavalier-Smith's eighth kingdom, Archezoa is now defunct. He now assigns former members of the kingdom Archezoa to the phylum Amoebozoa. Cavalier-Smith referred to what remained of the protist kingdom, after he removed the kingdoms Archezoa and Chromista, as the "kingdom Protozoa". In 1993, this kingdom contained 18 phyla as summarized in the following table: The phylum Opalozoa was established by Cavalier-Smith in 1991. By 1998, Cavalier-Smith had reduced the total number of kingdoms from eight to six: Animalia, Protozoa, Fungi, Plantae (including red and green algae), Chromista and Bacteria. Five of Cavalier-Smith's kingdoms are classified as