First some background. There are billions of bacteria in a person's body. Some say that there are more bacterial cells than human cells in the human body. There are many types of bacteria that live on and in the human body, each preferring a different environment or part of the human body.
One of the functions of the bacteria in the human body is to keep away bad bacteria. In effect, the natural bacteria that live on the human body are a part of the human immune system. The good bacteria are very well adapted to living on the human body and generally out-breed bad bacteria just due to their sheer numbers. So bad bacteria find it difficult to get a foothold on the human body. According to Wikipedia:
Within the genitourinary and gastrointestinal tracts, commensal flora serve as biological barriers by competing with pathogenic bacteria for food and space and, in some cases, by changing the conditions in their environment, such as pH or available iron. This reduces the probability that pathogens will reach sufficient numbers to cause illness. However, since most antibiotics non-specifically target bacteria and do not affect fungi, oral antibiotics can lead to an "overgrowth" of fungi and cause conditions such as a vaginal candidiasis (a yeast infection). There is good evidence that re-introduction of probiotic flora, such as pure cultures of the lactobacilli normally found in unpasteurized yogurt, helps restore a healthy balance of microbial populations in intestinal infections in children and encouraging preliminary data in studies on bacterial gastroenteritis, inflammatory bowel diseases, urinary tract infection and post-surgical infections.
When a broad spectrum antibiotic is used by a person, it doesn't discriminate between good bacteria and bad bacteria. It kills ALL bacteria in the person's body, including good bacteria. This leaves the body like a sitting duck for bad bacteria and viruses and fungi to gain a foothold and multiply out of control.
Now you can see why gun control and antibiotic misuse are similar? By preventing normal citizens from carrying firearms, criminals with guns have the edge because the citizens have nothing to defend themselves with.
