Resistance of Pathogens to Antibiotics

Pathogens include bacteria, viruses and fungi which are capable of causing diseases. Alexander Fleming discovered penicillin in 1928, but it took 12 more years until a method was found that could be used to produce it in sufficient quantities to be used in hospitals. It came in time to save the lives of many WWII soldiers who would have otherwise died because their wounds became infected. Since penicillin, scientists have developed many other antibiotics to target certain types of pathogens - namely, specific strains of bacteria. Antibiotics do not destroy viruses or fungi.

In recent times, antibiotic-resistant strains of bacteria have appeared which pose a threat to human health as they are very difficult to kill. The usual example of this is the MRSA bacterium in hospitals. This has developed a resistance to antibiotics but can be controlled by good hygiene - visitors to hospital wards are required to use a special alcohol based hand cleanser when entering and leaving a ward and regular use of bleach or other disinfectants when cleaning hospitals keep this dangerous bacterium under control.

But how do these resistant strains of bacteria arise? Firstly, there is the overuse of antibiotics. At one time, doctors would prescribe antibiotics 'just in case'. In other words, if a patient did not show signs of having a bacterial infection, they would still prescribe antibiotics to prevent infection. This allowed bacteria plenty of opportunity to mutate and develop a resistance.

Secondly, a course of antibiotics usually lasts from 7 - 10 days. Normally by day 3 or 4, you start to feel a lot better as the majority of the bacteria have been killed and some people then stop taking them. But the most resistant bacteria are still in your system and the rest of the course is designed to kill as many of these as possible leaving the remaining bacteria to be killed by your own immune system. Stopping taking a course of antibiotics early leaves too many of these resistant bacteria for your system to fully destroy and they can then be passed on to other people.