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Study on hospital infections: Patients introduce resistant ESBL germs to hospitals

  • InfectoGnostics researcher preparing a sample for testing. (InfectoGnostics / Fotostudio Ebenbild)

One in eight newly hospitalised patients is already a carrier of ESBL-forming bacteria, scientists from the InfectoGnostics Research Campus Jena have now proven in an observational study involving 1,334 patients. Although infections with the patient’s own ESBL pathogens remained an exception in the study, the researchers showed that the pathogens were able to transfer their resistance genes to other bacterial strains in the hospital. InfectoGnostics scientists from the Jena University Hospital, from industry partner Abbott and from the Leibniz Institute of Photonic Technology were all involved in the clinical study. The results were published in the scientific journal PLOS One.

Publication: Hagel S, Makarewicz O, Hartung A, Weiß D, Stein C, Brandt C, Schumacher U, Ehricht R, Patchev V, Pletz MW: ESBL colonization and acquisition in a hospital population: The molecular epidemiology and transmission of resistance genes, PLOS ONE (2019) DOI: 10.1371/journal.pone.0208505

Extended Spectrum beta-lactamases (ESBL) are enzymes that act as a kind of a “life insurance” for bacteria: Once the bacterium is able to produce such an enzyme, it can successfully defend itself against numerous antibiotics that are used in hospitals and also prescribed by GPs. The consequence: Increasingly, doctors have no other choice but to resort to reserve antibiotics in order to control infections. Thus, continuing a cycle that renders more and more antibiotics ineffective.

ESBL-forming bacteria do not mainly spread in hospitals, but rather colonise the healthy intestine, primarily via food intake. This colonisation in itself is not dangerous as long as affected patients are healthy.
In serious operations or in the case of patients with low immunity, however, these germs can lead to infections. Now, a team from the InfectoGnostics Research Campus Jena has examined the colonisation rate in patients newly admitted to hospital in an observational study, and evaluated whether this rate increases throughout the hospital stay. In addition to this, the researchers analysed which factors cause the colonisation with the pathogen.

Almost every fourth patient from a nursing home is a carrier of ESBL-forming bacteria

For the study, 1,334 patients were tested for ESBL-forming intestinal bacteria: initially upon hospital admission, then after treatment and - where possible - also six months after hospitalisation. The close collaboration between the hospital, research team and the industry proved to be of great benefit, as the lead authors of the study, Dr. Stefan Hagel, Dr. Oliwia Makarewicz and Prof. Mathias Pletz from the Center for Infectious Diseases and Infection Control of the Jena University  Hospital, reported: “At the hospital, we were able to collect the relevant samples and also important patient data, while Daniel Weiß and Prof. Ralf Ehricht from Abbott and IPHT adapted the CarbDetect AS-2 test that was developed on the campus for the analysis of rectal swabs. " Makarewicz explains. The test results were jointly analysed by the partners in their microbiological research laboratory.

The results of the study showed just how widespread ESBL-forming bacteria are in the population today: For every eighth patient tested (12.7 percent), it was possible to detect an ESBL germ upon hospital admission. This situation is even more dramatic in nursing home patients, however. Here, almost one in four patients (23.8 percent) is already a carrier of the multi-drug-resistant germs. Despite this high colonisation rate with ESBL pathogens, actual infections with the patient’s “own” ESBL germ during hospitalization were extremely rare: In the study, only one single patient was infected with their own pathogen.

Danger as a result of the transfer of resistance genes to other bacterial strains

The low number of infections in the hospital, however, is not yet a reason to give the all-clear, Dr. Makarewicz explains: “On the one hand, the number of actual infections in departments such as oncology, geriatrics or the intensive care unit is much higher, since high-risk patients with weakened immune systems are primarily treated here. On the other hand, we were able to demonstrate once again in our analyses that the genetic information for multi-drug-resistance is also transferred via plasmids to other types of bacteria in the intestine - new multi-drug-resistant pathogens can thus develop very quickly. It must be assumed that colonisation germs of this type can transfer resistances to hospital germs. The role of these small strands of DNA in the transfer of resistance is an issue which has received not nearly enough consideration in hospital practice to date. “