Infections Caused by Shigella (Shigellosis)

The Shigella bacteria are among the most common pathogens causing intestinal infections worldwide. Their spread primarily occurs through contact with food and water contaminated with feces, as well as touching infected surfaces. Such infections often occur in crowded and hygienically problematic environments, where the risk of outbreaks increases.

Shigella bacteria are particularly dangerous because a very low number of bacteria may be sufficient to cause an infection. The bacteria can withstand stomach acid, allowing them to easily adhere once they enter the digestive system. During an infection, the bacteria penetrate the epithelial layer of the colon, causing severe inflammation and tissue destruction. There are several different strains of the Shigella genus that cause illnesses in various locations and environments.

Infections caused by Shigella can pose serious health problems, making it essential for public health authorities and individuals to be aware of prevention and treatment options.

Characteristics of Shigella Bacteria

Shigella bacteria are classified as Gram-negative bacteria that lack a capsule, are non-motile, and can survive in the presence or absence of oxygen. The Shigella genus includes four different serogroups. Among these, Shigella dysenteriae, Shigella flexneri, Shigella boydii, and Shigella sonnei are the most significant. The first three groups are extremely similar, while S. sonnei differs biochemically from the others.

Shigella flexneri is the most commonly occurring strain in developing countries, responsible for about 60% of diarrhea cases. In contrast, Shigella sonnei is the most prevalent pathogen in developed countries, causing approximately 80% of cases. Shigella dysenteriae typically leads to outbreaks and thus warrants particular attention.

The infectivity of Shigella bacteria is extremely high, as as few as 100 bacterial cells may be sufficient for infection. This characteristic allows the bacteria to spread rapidly within communities, especially in environments where hygiene conditions are inadequate. Toxins produced by the bacteria, such as Shiga toxin, are particularly dangerous as they can lead to severe complications, such as hemolytic uremic syndrome.

Symptoms and Course of Shigellosis

The intestinal infection caused by Shigella bacteria is referred to as shigellosis, with symptoms appearing within one to two days after infection. Patients typically experience watery, mucoid stools, which can be bloody in more severe cases. Another characteristic symptom of the disease is abdominal pain, along with a constant urge to defecate, even when the bowel is empty.

Symptoms of shigellosis also include bloating and fever. The course of the disease usually lasts about a week, but the normalization of stool may take months. In severe cases, various complications can arise, such as dehydration, resulting from significant fluid loss. Additionally, intestinal inflammation can become so severe that it causes perforation, requiring immediate medical intervention. Neurological symptoms, such as drowsiness and seizures, may also appear in more severe forms of the disease.

The diagnosis of shigellosis is made through laboratory tests, which also allow for the examination of the bacteria’s sensitivity to antibiotics. This helps doctors select the appropriate treatment strategy.

Treatment and Prevention of Shigellosis

Milder forms of shigellosis generally resolve without treatment; however, patients should be encouraged to consume plenty of fluids and rest. Replenishing electrolytes and following a bland diet are also recommended during recovery. It is important to avoid lactose-containing foods, as they can exacerbate symptoms and prolong the illness.

In severe cases, antibiotic treatment may be necessary, but due to the frequent use of antibiotics, bacterial antibiotic resistance is widespread. Treatment options may include specific antibacterial agents that can be effective against Shigella strains.

Infectivity typically lasts from one to three weeks, so adhering to proper hygiene measures is crucial. The key to preventing Shigella infections lies in maintaining personal hygiene and following food safety rules. Currently, there is no vaccine available for shigellosis, so prevention relies on hygiene measures.

Shigellosis is a notifiable disease, meaning that the infected individual must inform their doctor, who will also notify public health authorities. The patient must not leave the community while symptoms persist and should be isolated in an infectious disease unit. Epidemiological monitoring is also mandatory for direct contacts until two negative stool samples can be provided.