Bacteria can sense you're stressed!

Yep, they can! At least there seems to be a link between stress levels and infection.
One of the main hormones that is released in the body under stress is adrenaline. This helps bring about a Fight or Flight response, with effects such as an increase in heart rate, bronchodilation, and that unpleasant sensation of suddenly getting a dry mouth. These effects are due to adrenaline binding to receptors on different target cells (i.e. heart muscle cells, smooth muscle cells in the airways, or salivary glands) and triggering a signalling cascade within those cells, which initiates the responses seen.
Bacteria have been found to have adreceptors too (i.e. receptors that bind adrenaline). This means that invading bacteria should be able to detect adrenaline in the body as a response to stress. The question that poses itself now is: "How does adrenaline influence bacterial behaviour?" Unfortunately for us, they seem to love it! Bacteria use a method called Quorum Sensing to communicate to each other and assess their population density, as well as regulate the expression of virulence genes. It is thought that adrenaline is one of the hormones released by the human body that influences this mechanism by enhancing it and increases the bacteria's ability to replicate at the site of infection.
This is not only important in the field of medicine, where drugs developed to block adrenoceptors in bacteria may provide a way of combatting antibiotic resistance, one example of bacterial virulence, but also in the food industry, where the method of slaughter and animal keeping may play a role in increasing adrenaline levels in the muscle, which would make the meat more susceptable to bacterial colonisation.
This is just one of the many pathways that may be involved in the development of bacterial disease, and icreased susceptability to infection may well be due to the interplay and crosstalk between these pathways. But that's what makes it so fascinating!
So the next time your job gets you stressed or the kids are playing a bit too loudly, think about the bacteria that might be loving your high adrenaline levels ... on second thoughts - don't - that might make you even more stressed! :)

References:


http://www.pnas.org/content/100/15/8951.abstract?ijkey=6ccaada220c61e2c45a5c80d2cb7439e00291a50&keytype2=tf_ipsecsha