Hygiene

Question

Hello,
MRSA can be as is known transmitted via the hands. New numbers from the internet (paul ehrlich institute, Germany) say, that 22% of the average population are MRSA carriers. Does that mean that one gets infected with MRSA in the short or long runs - and therefore become also a carrier? Or are the carriers not infectious for others, as long as they do not have open wounds etc. ?
Where does the main risk lie to get infected?
Many thanks for your answer.

Answer

Dear questioner,
according to the acutal epidemiological siutaion in Germany one does not become earlier or later automatically a carrier of MRSA. The main risk of a colonization with MRSA resp. an infection with this germ lies above all in hopsitals resp. other facilities of the health care system. Especially, this is a question of special risk factors. With your question you address however an overall very complex topic, which can not be answered here comprehensively comprising all aspects. However I can not give a general answer, as there can be in the end differing constellations, which are associated with different risks. In the following I will try to address the most important connections of your question (for further questions about MRSA please see e.g. www.mrsa-net.org).

S. aureus is a gram-positive bacterium and a frequent colonizing germ (intermittend or permanent) of the skin and mucosa of humans (but also animals). A colonization is per se not a special finding. Furthermore, S. aureus is a frequent cause of infection (e.g. abscesses, infections of the tissue, wounds and sepsis).
Especially frequent S. aureus colonizes the vestibule of the nose. From this location, S. aureus can be transmitted e.g. via the hands to other regions of the body or to other persons resp. other patients in the hospiatl and lead to a new colonization or even infection. Susceptible for infections are especially persons with risk factors (immuno-deficiency, diabetes, therapy with antibiotics, existance of predilection sites, as e.g preexisiting wounds or wounds after operations), as it can be found especially in patients of the hospital. Furthermore it is known, that a pre-existing colonization e.g. of the nasal vestibule (carrier state) dependent on the individual risk (preexisting illnesses, see above) can even be a risk factor for a later acquired infection in hospital.

In these mechanisms, S. aureus and MRSA are not different in general. A so-called MRSA (methicillin resistent S. aureus) is in so-far a special problem, as in this variant of a S. aureus the therapeutical possibilities are very limited due to a distinct resistance against antibiotic drugs. In the hospital one tries to reduce the number of infections with S. aureus and especially MRSA with numerous hygienic measures (e.g. disinfection of the hands). Equally, colonized MRSA-patients are isolated in the hospital strictly, in order to avoid a transmission to other patients. According to the infectious meaning of MRSA its spreading in the hospital is investigated very well. The frequence of MRSA in hospitals can vary strongly (hospital A versus hospital B resp. ward A versus ward B, resp. patients with chronic woulds versus patients with operation wounds). Hereby the frequency can lie around 20-25% (as mentioned by you) but also clearly below. Special groups of persons, which had frequent contact to medical facilites (frequent stays in the hospital, persons in old peoples homes, preexisting illnesses) are as a rule colonized more frequently with S. aureus resp. MRSA as the average population.
The more often a S. aureus resp. MRSA can be found as a colonizing germ, the more often it can come to a transmission resp. infection. This one tries to avoid by hygienic measures resp. to minimize. In the hospital for example, persons with risk factors for a colonization with MRSA are investigated before admission on a ward for the indeed existance of MRSA, in order to initiate early the required hygienic measures (isolation etc.). An absolute protection for transmission does not exist.
Also in the average population it is possible to transmit S. aureus resp. MRSA between persons. In case of MRSA, it has to come first to an exposition with a MRSA-carrier of course. The frequency of MRSA in the average population is however much smaller as in hospitals and lies clearly under 1%. Also outside of hospitals special groups of persons can be involved more frequently resp. function as a carrier [in the USA it has been shown e.g. for homosexuals, clients of tatoo-studios, inmates, sportsmen]. It has been shown, that here a frequent resp. tight contact resp. contaminated things are necessary (members of a household, sportsmen: showering together, exchange of clothes, towels, tricots, comtaminated tatooing-devices). It has been shown, that those MRSA which have been exchanged in the average population (cMRSA for "community") are not identical with those exchanged in hospitals (hMRSA for "hospital"). These cMRSA do however until now not play a role in Germany. The risk of getting exposed in the average population to an MRSA-carrier in Germany is therefore very small. Also here hygienc measures, like the reguar washing of the hands, protect against the colonization with MRSA or other potential germs.
Yours sincerely,
Michael Hogardt

11.01.2011