Lichtgedanken 03

Rubrik 19 03 | LICHT GEDANKEN Yeasts spur bacteria to produce more toxin Similarly as Candida albicans , various in- testine bacteria also belong to the facul- tative pathogenic species and may cause life-endangering infections, including sepsis. In the current research project CanBac by the Center for Sepsis Control and Care (CSSS), the researchers in the Jacobsen’s team, their colleagues from the HKI and the University examine the interplay of the organisms among themselves and towards their host – the human. »We cultivate intestinal absorptive cells, so-called enterocytes, and infect the- se with combinations of the examined microorganisms,« explains Dr Joanna Niemiec their experimental approach. »In the project, we want to understand how fungus and bacteria influence each other regarding their pathogenicity.« Dr Niemiec is a postdoctoral resear- cher and leads the project team CanBac within the Jacobsen’s research group. Among others, the researchers study the interplay between Candida albicans and the intestine bacterium Proteus mi- rabilis . The cell culture shows that both microorganisms, respectively, may da- mage the intestinal cells on a limited. If the intestine cells, however, are infected by both pathogens at the same time, the picture the researchers see is a strik- ing one: »In this case, almost every cell comes to its end,« sums up Dr Niemiec. »Here, we do see a synergetic, mutually intensified effect of both pathogens.« The first, yet not published findings from the Jena research team reveal the reasons for the devastating effect. There are various indications that the bacteria Proteus mirabilis produce an increased amount of toxin in the presence of Can- dida albicans . This hemolysin is a protein which lyses, i.e. dissolve, the cell mem- brane of the host organism. As a result, the cells die. »Essentially, the fungus makes the bacterium more toxic,« illus- trates Prof. Jacobsen. In comparison to this, the »aggressiveness« of the fun- gus—this being pathogenic, too—is not stimulated by the bacterium. Indeed, Candida albicans may produce a lethal toxin, i.e. candidalysin. However, it is rather unlikely that its production may be additionally boosted by a co-infec- tion with Proteus mirabilis . In the current examinations, the resear- chers want to find out by which che- mical »means of communications« the microbes communicate with each other. It is already clear that also other yeast fungi, for instance the common baker’s yeast Saccharomyces cerevisiae , spur Proteus mirabilis into the intensified pro- duction of hemolysin. »Additionally, we also want to find out whether the effects observed in the cell cultures are repro- ducible in vivo,« reveals Dr Niemiec. In this regard, studies on roundworms and mice are being planned. A targeted-oriented prophylaxis against fungi »Nonetheless, we can derive some use- ful aspects for the treatment of patients in intensive care from the findings al- ready,« makes Prof. Jacobsen clear. Ac- cording to her, every seriously ill pati- ent should undergo an individual risk assessment on how probable an emer- gence of sepsis may be. »If, for example, Candida albicans reduces other microor- ganisms after the patient has received an antibiotic therapy and the germ con- tent of Proteus mirabilis or another com- parable pathogen increases at the same time, a concrete, serious risk for the pa- tient exist.« In her opinion, a prophylactic therapy concentrated on fungi is advisable in such cases. On the other hand, Prof. Ja- cobsen is critical of general prophylac- tic measures against fungal infections using agents. »All in all, there are only a few antifungals; if they are generously used for prophylaxis, the fungi may be- come resistant, similarly to antibiotics.« Therefore, these agents should be used for specific purposes only. Dr Maria Joanna Niemiec (left) and the master's student Isabel Auge are plating mouse excrement to culture medium in order to determine the microorganisms in there. They want to find out how yeast fungi and intestine bacteria communicate with each other.