Bacillus infection

Medical quality assurance by Dr. Albrecht Nonnenmacher, MD at December 30, 2016
StartDiseasesBacillus infection

Bacillus infections arise when a patient is infected with one of several different types of bacteria. These types of bacterial infections include bacteremia, anthrax, and different types of food poisoning.


Definition & Facts

Bacillus refers to a genus of bacterial species that share a few traits. They are all shaped like rods, and they all give a positive result on a gram test. Most of the species are harmless, but a few of them can cause dangerous infections, and those are the species that receive the most attention in medical literature. 

Bacillus anthracis is the most well-known of these species because it is responsible for causing anthrax, but other species, including Bacillus cereus also have significant medical importance. Bacillus bacteria are found all over the world, most often living in the soil, so most people are exposed to at least one of the species at some point during their life.

Symptoms & Complaints

The symptoms associated with a bacillus infection will vary depending on the species that caused it. Bacteremia, or the presence of bacteria in the blood, can occur as a result of exposure to any species. Bacillus bacteremia is usually a minor problem and rarely requires extensive treatment, but in a minority of cases it can cause serious medical issues, including sepsis and septic shock. These problems carry a risk of death, and infections can spread from one part of the body to another.

Many species of bacillus bacteria can also cause nausea, fatigue, and other flu-like symptoms, although these are not universal and are most common as a result of foodborne illnesses. The most dangerous species can cause skin lesions, necrotic ulcers, pneumonia, inflammation, and the vomiting of blood.

These infections are extremely dangerous and have a high mortality rate if they are left untreated, so they require immediate medical attention from a physician. All of these symptoms arise from a small number of bacillus species, and the majority of the species will not cause any symptoms in humans after exposure.


All bacillus infections are caused by exposure to a small number of bacterial species. There are three common vectors for entry into the human body. The most common infections arise when humans consume food which has been contaminated with bacillus bacteria. Raw vegetables can carry the infection, but the most common culprit is undercooked meat taken from herbivores, who are exposed to the bacteria as they graze.

Other infections occur when the bacteria makes contact with an open wound. This can easily happen when people injure themselves while working outdoors, since bacillus bacteria is extremely common in the soil.

It can also occur as the result of contaminated needles, or on rare occasions as part of a deliberate attack (e.g. anthrax has been used as a weapon of biological warfare). Finally, the bacteria can also enter the body through the eyes, nose, and other body cavities. That usually happens when people are exposed to the bacteria from nature and neglect to clean themselves after doing so, which allows the bacteria to enter their body as soon as they touch an open orifice.

Diagnosis & Tests

Physicians begin the process of diagnosing a bacillus infection when the patient reports their symptoms. In some cases, such as exposure to Bacillus anthracis, an infection will be the doctor's first guess. In other cases, they may need to test for other diseases before concluding that the patient suffers from a bacterial infection.

Once the doctor reaches that conclusion, they may choose to test the patient's blood to determine the type of bacteria that is causing the infection. They usually rely on a gram stain to do so. The test involves harvesting a sample of the bacteria from the patient and exposing them to a specific dye. Some bacteria have cell walls that will retain some of the dye after exposure, while others do not. A bacterial species that does retain the dye is called gram-positive, and that includes all bacillus species.

Treatment & Therapy

Bacillus infections are treated with a full course of antibiotics. The treatment is usually most effective when it is applied shortly after the patient is first exposed to the disease, so speed is essential. If exposure to bacillus bacteria can be confirmed before symptoms appear, some physicians will apply antibiotics immediately in order to maximize their impact. When possible, doctors prefer to tailor the antibiotics to the specific species that are infecting the patient.

If they are concerned about the speed of treatment, they may order the patient to take a mixture of antibiotics until blood tests reveal the nature of their infection, at which point they transition to a tailored treatment. In addition to the antibiotics, some doctors will prescribe treatment for individual symptoms in order to prevent damage to the body while the antibiotics do their work.

In the case of severe food poisoning, this often includes extra fluids in order to prevent dehydration, while other symptoms might be suppressed with pharmaceuticals. These treatments may be combined with observation in extreme cases to deal with emergency symptoms as they appear.

Prevention & Prophylaxis

Like all infections, the medical problems associated with Bacillus bacteria are best prevented through proper hygiene. People can minimize their risk by bathing or showering regularly, washing their hands after exposure to dirty surfaces, and keeping open wounds as clean as possible. Covering those wounds can also help.

In addition to staying clean, people can prevent infection through their food by cooking it thoroughly before eating. It is also possible to prevent some bacillus infections through vaccination, although vaccines are not available for all species.