Common Pathogenic Bacteria Found in Stool


Stool is the solid or semi-solid waste material that is eliminated from the digestive system through the anus. Stool contains various substances, such as undigested food, water, mucus, bile, and bacteria. Bacteria are microscopic organisms that are present in almost every environment, including the human body. Bacteria can be classified into different groups based on their shape, structure, metabolism, and staining properties. One of the common ways to classify bacteria is by their reaction to a dye called Gram stain. Bacteria that retain the purple color of the dye are called Gram-positive, while those that lose the color and appear pink are called Gram-negative.

The bacteria found in stool are representative of the bacteria that are present in the digestive system (gastrointestinal tract). Certain bacteria and fungi called normal flora inhabit everyone’s gastrointestinal tract. They play an important role in the digestion of food and their presence keeps a check on the growth of disease-causing bacteria. The normal flora of the gastrointestinal tract varies depending on the location, diet, age, and health status of the individual. Some of the common genera of bacteria that are part of the normal flora include Bacteroides, Bifidobacterium, Lactobacillus, Escherichia, Enterococcus, and Clostridium.

However, not all bacteria found in stool are harmless or beneficial. Some bacteria can cause infections and diseases in the gastrointestinal tract or other parts of the body. These bacteria are called pathogenic bacteria. Pathogenic bacteria can enter the gastrointestinal tract through contaminated food, water, or contact with infected animals or people. Some of the common pathogenic bacteria that can be found in stool include Salmonella, Shigella, Campylobacter, Vibrio, Helicobacter, Yersinia, Proteus, Staphylococcus, Listeria, Fusobacterium, and Bacillus . These bacteria can cause various symptoms and complications, such as diarrhea, vomiting, abdominal pain, fever, dehydration, inflammation, ulcers, bleeding, sepsis, and cancer.

A stool culture is a laboratory test that can identify the type and number of bacteria present in a stool sample. The test helps to determine if pathogenic bacteria are the cause of a person’s gastrointestinal symptoms (gastroenteritis). The test involves placing a small amount of stool on a special medium that allows the growth of bacteria. The medium is then incubated for a certain period of time and observed for any bacterial colonies. The colonies are then further tested for their characteristics and susceptibility to antibiotics.

In this article, we will discuss some of the common Gram-negative and Gram-positive bacteria that can be found in stool and their role in causing gastrointestinal diseases.