Intra-abdominal infections occur when bacteria usually present in the gastrointestinal tract (GIT) leak into adjacent tissues. Surgery, trauma, or diseases may cause injuries to the mucous membrane or changes within the normal flora. Infected organs are usually the gallbladder, bile ducts, and the intestine. The inflammation of the gallbladder (cholecystitis) is usually caused by Escherichia coli and enterococci. Symptoms can be fever, gradual or sudden pain in the upper abdomen (belly), nausea and vomiting. The bile ducts transporting the bile from the liver into the small intestine can be infected (cholangitis) by Escherichia coli, enterococci, or anaerobes from the gut as well.

Acute infectious diarrhea is most commonly caused by and Campylobacter, Shigella, Salmonella species and toxin-producing Escherichia coli. Shifts in the composition of the normal flora owing to disease or treatment, i.e. antibiotic treatment, and contamination of food and water sources usually leads to infectious diarrhea.

Skin infections are most commonly caused by bacteria, followed by mycosis and viral diseases. Most bacterial infections of the skin are caused by Staphylococcus aureus, streptococci, and pseudomonads. Folliculitis is the inflammation of hair follicles, possibly leading to permanent hair loss. Impetigo and Ecthyma are inflammatory skin diseases characterized by pustules leaving scars and pigmentation, if untreated. Skin infections may interrupt the integrity of the skin, the natural defense barrier of the non-specific immune response, facilitating invasion of possible pathogens. Diabetes can result in severe infections of the skin, i.e. diabetic gangrene.

Bone and joint infections include most commonly septic arthritis and osteomyelitis, caused by pathogens such as Staphylococcus aureus. Infection with Gonococcus in sexually active young men and women can also lead to an inflammation of the joints (septic arthritis). Inflammation of the bone is painful and may lead to the formation of abscesses.