What are cocci?
Cocci are spherical bacteria that are either completely round or egg-shaped or elliptical in shape. The fact that certain types of bacteria are cocci, the medical layman can recognize the name ending -coccus. Cocci occur in different forms of organization, depending on which division they have not separated. The best known representatives are staphylococci, streptococci and enterococci.
If the bacteria that are normally present in every human being and animal encounter particularly favorable conditions and multiply rapidly, they can trigger dangerous illnesses and even lead to death. Particularly immunocompromised persons, diabetics, neurodermatitis and hospitalized persons (patients and hospital staff) are particularly at risk of contracting a cocci infection. Most cocci are treated with common antibiotics. However, there are already strains that are resistant to certain antibiotics.
The staphylococci were first described in 1884 by Friedrich Julius Rosenbach. Enterococci were formerly known as streptococci of serogroup D because, like streptococci, they have the group D-Lancefield antigen. Since 1984, however, they are considered as a separate cocci genus because of their divergent genetic structure. They belong to the lactobacilli (lactic acid bacteria).
Occurrence, distribution & characteristics
The globular bacteria are organized in groups of two (diplococci), tetrads (quadruplets), or as chain cocci, pack cocci (quadrangular aggregation of 8 and more globular bacteria) or cluster cocci (in grape form). Staphylococci are found in large numbers and colonize the surfaces of skin and mucous membranes in large numbers - which does not bother people with an intact immune system.
The gram-positive pathogens have no proper movement and feed on putrid substances (saprophag). Because they have a high pH tolerance, some disinfectants can not kill them. Even dehydration can not harm them.
Because they can quickly adapt to new environments through mutation, they spread rapidly and can cause epidemics. Transmission occurs from person to person through direct contact with an infected person, through infected items and food. The incubation period after infection with staphylococci is 4 to 10 days. Infected patients can not show symptoms until months later. In food poisoning it comes to a few hours to the first signs of disease.
Most important representatives are Staphylococcus aureus, which colonizes skin and mucous membranes and Staphylococcus epidermidis, which lives on the skin and other surfaces and is feared in hospitals because of its resistance to Penicillin and Methicillin. He is transmitted there via infected devices, blood, cough secretions, wound secretions and skin contact. Via transplanted heart valves, artificial joints and permanent venous catheters, it enters the patient's body.
Streptococci colonize the oral cavity and are usually harmless. The gram-positive globular bacteria organize individually or in pairs in more or less long chains. They can not move by themselves and do not form spores. Some strains are surrounded by a mucous envelope. They live anaerobically, but can be exposed to oxygen and are produced by fermentation processes. Enterococci also form chains and belong to the normal intestinal flora in animals and humans. They also occur in foods such as cheese and sausage.
Diseases & complaints
Staphylococcus aureus invades the bloodstream via wounds and injuries. Externally it causes eczema, boils and carbuncles. If it spreads through the bloodstream, it can cause heart and lung inflammation, hepatitis, meningitis and even blood poisoning. Particularly at risk are patients with a damaged skin barrier (neurodermatitis) and people with circulatory disorders of the skin.
Particularly problematic are the Staphylococcus aureus strains, which are now resistant to excessive use of antibiotics (MRSA strains). Very dangerous for the patient is also the toxic shock syndrome (circulatory failure due to explosive propagation of staphylococci in the body). In addition, staphylococci can cause food poisoning, as even the heat treatment does not kill the pathogen completely. Some strains are insensitive to heat. Staphylococcus epidermidis likes to attach to foreign materials and, despite adequate disinfection, enters the patient's body where it can cause infections and even blood poisoning. Old people with heart disease and weakened immune defense as well as freshly operated patients are particularly at risk. After amputations, the penetrated globular bacteria delay the healing process.
Streptococci cause tooth decay by attacking the enamel and are responsible for many infections in the ENT area such as middle ear and tonsillitis. In addition, they are considered to be the cause of pneumonia, purulent connective tissue inflammation (phlegmon), pus (impetigo), wound and urinary tract infections, scarlet fever, childbed fever and the Toxic Shock Syndrome (TSS).
Streptococci are usually treated well with penicillin. Enterococci can cause chronic urinary tract inflammation as they enter the urinary tract from the gut. In addition, they can cause pleura and heart inflammation. They are treated with a combination of aminopenicillin and aminoglycosides or - in the case of resistance to penicillin or oxacillin - with a combination of ampicillin and gentamycin.