opportunistic infections/pathogens

When we are prescribed antibiotics, we are trying to kill the pathogen that is causing all our problems. Now there are two types of antibiotics: broad spectrum and narrow spectrum antibiotics. Broad spectrum antibiotics will kill almost all the microbes inside us, whether they are pathogens or not. We all have millions of microbes within us. They exist in our gut, inside our oral cavity, in our ears, etc. These microbes cause us no harm and are supposed to be there.
Narrow spectrum antibiotics will only kill the pathogens.
In order to be prescribed a narrow spectrum antibiotic, the doctor will need to collect a specimen form you and send it to the lab for processing. Only then will he know what antibiotic to prescribe. But in the surgery there is usually no time to do this. So the doctor will usually prescribe a broad spectrum antibiotic. This is where all our troubles begin.
A good doctor will prescribe an antifungal medication at the same time as the broad spectrum antibiotic. When all the microbes are killed, it allows other microbes that usually dont cause disease to cause disease in you. This is called an opportunistic infection. These microbes get an "opportunity" to cause disease. A classic example of an opportunistic pathogen that will cause infection after you taking a broad spectrum antibiotic is Candida albicans which causes thrush. So taking an antifungal tretment with the antibiotic will prevent this opportunistic infection. Another way of preventing thrush is to eat live culture yoghurt every day that you are taking the antibiotic. Live culture yoghurts replace the microbes that are killed. Or you could even take a probiotic which serves the same function as the yoghurt.
A good doctor will tell you this. A "stupid" doctor will not. You end up with another problem whilst trying to solve one problem. Not nice.
Question time: What organisms are found in live culture yoghurts and probiotics?
How many organism are present in each probiotic tablet?
What are the guidlelines for taking probiotics?
Give one example of a broad spectrum and narrow spectrum antibiotic.