Vive la Resistance!

This month’s blog is going to beat on what should be a familiar drug… antibiotic resistance. Most of you would have learned this topic as part of your biology studies as it’s not only a fascinating example of the mechanism of natural selection in action on a time scale we can appreciate, but it is also hugely relevant to all of us as part of our day to day healthy living. I am sure many of you readers would have taken antibiotics at some time in your life and benefited from their effect… but what would happen if they stopped working? Up until recently, doctors have been able to rely on the fact that they had several different antibiotics available to tackle a bacterial infection; if the infection is resistant to one drug, then try another, and then another and so on until the infection is resolved. But in fact in the US and EU, there are only around 25 available antibiotics – could a strain of bacteria evolve to be resistant to them all. Recently sent a bacterial sample to the U.S. Centers for Disease Control and Prevention (aka the CDC, as often featured in many disaster movies!).

The bacteria, CDC scientists found, produced a nasty enzyme called New Delhi metallobetalactamase, known for disabling many antibiotics. The enzyme was first seen in a patient from India, which is where the patient in question broke her leg and received treatment before returning to the United States. The enzyme is worrisome because it arms bacteria against carbapenems, a group of last resort antibiotics reserved for the sickest patients with the most difficult to treat infections. The CDC’s final report revealed startling news: the bacteria raging in the woman’s body were resistant to all 26 antibiotics available in the USA. She died from septic shock; the infection shut down her organs. While incredibly frightening, this is fortunately still a very rare occurance; current estimates that there have been fewer than 10 cases of completely resistant bacterial infections in the United States. However, such absolute resistance to all available drugs, though incredibly rare, was once regarded as a far-off “nightmare scenario”. So what can be done? While progress on developing new antibiotics has slowed, some researchers are taking a new approach with their goal to flip the nightmare scenario and send a killer after the killer bacteria.

The strategy, referred to as a “living antibiotic,” would pit one group of bacteria — given as a drug and dubbed “the predators” — against the bacteria that are wreaking havoc among humans. The “predator” in this case is Bdellovibrio, a bacterium which may offer a new way to fight infections. It enters its bacterial host by force, squeezing in between the cell wall and inner membrane. The predator’s enzymes break down the prey’s innards. Next, the predator replicates, eventually bursting out of the dead prey with its progeny (sounds a bit like something from Alien). While in-human trials are still a way off, researchers have already had success using these predatory bacteria in animal model s. Furthermore, the approach offers a potential solution to the problem of antibiotic resistance – by using a “live” therapy, the predator may be able to keep pace with any defensive mechanisms the target bacteria develop.