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Germs that infect humans

Streptococcus pyogenes

Streptococcus pyogenes

© Dennis Kunkel Microscopy, Inc.

Microorganism: Streptococcus pyogenes

Disease: necrotizing fasciitis (flesh-eating disease)

Mechanism of action of the microorganism: the bacterium usually enters the body through a minor wound such as a cut or bruise, or through a surgical wound. It multiplies in the fascia (the tissues covering the muscles), and produces toxins which destroy them. The dead tissue looks like chewed flesh, giving the disease its popular name.

Symptoms of the disease: the early stages of the disease are characterized by muscle pain, fever, vomiting, diarrhea, and malaise. Other symptoms include a drop in blood pressure, skin rash, and persistent pain at the site of infection. In extreme cases, the disease may result in toxic shock and even death.

There are many strains of Streptococcus pyogenes. While one strain causes necrotizing fasciitis, others are responsible for a variety of diseases, including throat and skin infections, scarlet fever, and rheumatic fever. The symptoms of scarlet fever are skin rash on the trunk, fever, sore throat, and a strawberry tongue. Rheumatic fever is an autoimmune disease whose symptoms are inflammation of the joints, the tissues under the skin, and the central nervous system, and damage to the heart valves.

Incubation period: one to three days.

Contagious period: ten to 21 days, although this may be reduced to less than 24 hours if appropriate antibiotic treatment is begun.

Hosts: humans.

Transmission: direct contact with infected persons or with objects contaminated by contact with airborne droplets. Victims may be the host of the bacteria that attack them, as Streptococcus pyogenes is naturally present in some people.

Treatment of the disease: antibiotics, primarily penicillin.

Geographic distribution of the microorganism: worldwide, although some strains are only found in some locations.

Prevention: information campaigns on the mechanism of transmission. Avoidance of situations, such as contact with infected individuals, which favor bacterial transmission.

Vaccine: none.