Aspergillus is a fungal genus which contains a known 20 species. These fungi manifest as molds, and they are very common in the natural environment. In fact, Aspergillus is so common that it is highly probable that you are breathing some spores in at this very moment. These fungi are of medical interest because several species are pathogenic, causing diseases in humans and animals. Disease caused by an infection with Aspergillus is known as aspergillosis. These fungi have been described since the 1700s.
These fungi form colonies in a wide range of colors, depending on the individual species. Some species grow very rapidly, while others are designed to conserve energy, and they may grow slowly, but steadily. Aspergillus species are aerobic, meaning that they need oxygen to survive, and they tend to prefer oxygen-rich environments. They grow on a variety of substrates, from the walls of homes to the leaves of plants.
Some Aspergillus species colonize food, causing spoilage. Others are relatively benign, unless they happen to land in the body of someone who has a vulnerable immune system. Other people are usually able to resist infection as long as they are generally healthy. One of the most common forms of aspergillosis is a lung infection; birds in particular are vulnerable, as are young children and people with existing lung conditions such as asthma. The fungi can colonize the respiratory tract, causing coughing and severe discomfort. Antifungal medications can be used to treat lung infections caused by Aspergillus species, along with supportive therapy to keep the patient's airway clear.
In people with compromised immune systems, it is possible to develop invasive aspergillosis, in which the fungi spread throughout the body. Several antifungal drugs can be used to treat this form of the infection, although invasive aspergillosis can overwhelm a patient's body if he or she is very sick. Cancer patients and people with AIDS are especially at risk of developing this form of aspergillosis, among many other opportunistic infections.
These fungi aren't all bad. A. oryzae is a species used in the fermentation of some traditional foods such as sake, and A. niger may not be a welcome guest when it colonizes the walls of a home, but it can be used to produce a number of medically useful compounds. With the discovery of additional species, scientists will undoubtedly discover more members of the Aspergillus genus with practical and beneficial uses.