Ärzte Zeitung online, 22.11.2008

When Harmless Bacteria Become Life-threatening

Legions of bacteria live on human skin and mucosa. Patients with compromised immune defences are susceptible to infection. Vaccination protects against many of the pathogenic strains of streptococci.

When Harmless Bacteria Become Life-threatening

A common cold could be the beginning of a severe infection: Bacteria which are otherwise kept in check by the immune system may then multiply vigorously. Photo: medicalpicture/Novartis Behring

By Helga Brettschneider

The human being is a biotope: legions of bacteria such as streptococci live in and on our bodies. These tiny spherical bacteria are found in the nasopharynx and on the skin. Actually, colonisation with large numbers of streptococci is normal and is not even noticed by the host. "All human beings repeatedly harbour various streptococcal species without these bacteria causing any disease," says Dr. Björn Jensen of Düsseldorf University Hospital. However, sometimes these bacteria can cause severe infections. At the MEDICA, the world's largest medical trade fair with parallel congress, Jensen will report on life-threatening forms of streptococcal infection at a lunchtime symposium.

These unicellular microorganisms become dangerous, for example, when the body's own immune defences are weakened, e.g. by chronic illness, an immune deficiency or simply advanced age. Bacteria which are otherwise kept in check by the immune system may then multiply vigorously. It is also dangerous when pathogens enter the blood stream - through a wound, for example. Once these pathogenic microbes are in the blood, they potentially have access to all organs of the body. Even the tiniest break in the skin or mucosal membranes may serve as a portal of entry. And some streptococcal species are especially virulent regardless of the route of entry.

The life-threatening diseases that can be triggered by streptococci include pneumonia, meningitis and bacterial endocarditis. Bacterial endocarditis is frequently caused by the Viridans group of streptococcal species. These usually live in the oropharynx and can cause dental caries. Whenever wounds occur in the mouth (during tooth extraction, for example), the infecting microbes can enter the blood stream and cause endocarditis. This condition can damage the cardiac valves and become life-threatening. Patients with defective, previously damaged or artificial heart valves are at the greatest risk since bacteria can easily lodge on injured or pathologically altered valves.

For this reason patients in these groups should receive antibiotic prophylaxis prior to dental procedures, says Jensen. The same applies before gastroscopy or colonoscopy procedures, which may also facilitate the spread of bacteria into the blood stream.

A strong sneeze is enough for the transmission

The pneumococci (Streptococcus pneumoniae) constitute an especially well-known species of streptococci. Apart from causing pneumonia and other upper respiratory infections, they can also cause meningitis. The nasopharynx of every second person is colonised with these pathogens. The bacteria are spread from person to person by droplet transmission: a strong sneeze will do the trick. However, the disease is usually triggered by endogenous pneumococci.

According to information supplied by the German Green Cross (DGK), about 12,000 people die each year in Germany of pneumococcal infections. One-half of these deaths occur within only 48 hours. Pneumonia and meningitis, in particular, can take a fatal course. Pneumococcal meningitis is a relatively rare disease with an estimated incidence of 1,100 annually. Pneumococcal pneumonia, which affects 100,000 to 300,000 people each year, is much more widespread. A sudden onset is characteristic of the disease, which strikes mainly people over age 50. "One minute a person is doing fine and one or two hours later he or she feels seriously ill," says Jensen. The symptoms include (painful) cough, purulent expectorate, high fever and chills. The respiratory and heart rates are both elevated. Frequently, the patients have dyspnoea. In older people, however, fever may be absent.

The disease is treated with antibiotics. Treatment should be instituted promptly since any delay lessens the patient's chance of survival. For several years doctors have been grappling with an additional problem: the increasing resistance of these bacteria to some antibiotics. This resistance makes treatment difficult and preventive vaccination all the more important. The vaccine for adults is effective against 23 especially common pneumococcal strains (out of more than 80!). Vaccination does not confer total protection against infection; however, it does prevent severe forms of the disease. In Germany vaccination is recommended for everyone over age 60 as well as for chronically ill individuals of any age. These include diabetics and people with cardiovascular, pulmonary or immune deficiency disorders.

A conjugated vaccine is recommended for infants

Furthermore, immunisation with a special (conjugated) vaccine is recommended for infants in the first year of life; this kind of vaccine is effective even when the immune system is still immature. The large benefits of vaccination have been confirmed, for example, by a study carried out in the U.S., where immunisation with a conjugated vaccine has already been widely recommended for the last eight years. In the U.S. there has been a sharp decline in the incidence of pneumonia among children under the age of two. The rate of hospital admissions due to pneumonia was reduced by more than 50 percent within a period of five years - from 11.5 per 1,000 children to 5.5 in 2004.

When Harmless Bacteria Become Life-threatening

Lunchtime Symposium
In German
Samstag, 22. 11. 2008,
13.15 bis 14.00 Uhr,
CCD.Süd, Raum 2
Leitung: Dr. Björn Jensen, Düsseldorf

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