O_G...if I can help.
There is a little more to the principals and practice of medicine than just the book, Home Doctor and the modern link to a website with a long list of possible causes and diseases most of which inappropriate and unheard of by the reader.
I think your question to Woofgang is why do Gp's give antibiotics to an infection that may well be viral and not bacterial.
The key word is prophylactic......to stop an infection before it starts.
First of all, the patient may be immune deficient as indicated by a drug regime or an underlying disease, asthma or in the case mentioned above, absence of a spleen......clearly an indication for prophylactic antibiotics.
But, one of the commoner reasons is that of the GP knowing his or her patient and understanding that he or she will never accept the advice of the doctor without a prescription for antibiotics and hence to save himself a load of hassle, he prescribes them.
Is that justifiable? Yes in my opinion it is.
Many patients have their own idea of their medical management and will not budge until it is dispensed......see many posts on AB.
Has that helped O_G?