There has been a lot in the press recently about carbapenem resistant enterobacteraciae (CRE).

As people with a professional interest in infection, it is important we know in detail the origins of carbapenems and carbapenemases. Such knowledge and understanding also focuses the mind when trying to control them.

Carbapenems are derived from Thienamycin, a naturally occuring substance found in Streptomyces cattleya, which is a bacteria found commonly in soil in the environment. Other bacteria residing close to these carbapenem like substances in the environment thus have to protect themselves to avoid being destroyed. Thus carbapenemases evolved in other environmental bacteria such as Bacillus cereus, Bacillus anthracis and Shewanella, amongst others.

What we have done is take these naturally occuring compounds, purified them (with only very minor modifications), concentrated them and started administering them to humans in the form of carbapenem antibiotics, thus ramping up the selection pressure on the human bacterial flora.

It is thus not surprising that human enterobacteraciae, faced with this selection pressure have decided that they want defences against carbapenems, and have “acquired” the resistance genes from the environmental bacteria, most likely by transfer on mobile genetic elements.

Many people still perceive carbapenemases as being a relatively new phenomenen. We know that they are not new however. Both carbapenems and carbapenemases have probably been around for millions of years. We have just moved the battle between carbapenems and carbapenemases from the “hills” into the human flora, where it really matters….

Michael

Off camping this weekend!, I will write a short article next week sometime on “protecting the carbapenems”.