An undescended testicle in male maltese dogs is not uncommon, though not necessarily prevalent. I wonder if the infection is related to that. (Infections can also affect the tear ducts BTW; that is why many tear stain removers contain antibiotics.)
Given his situation, this male is probably not suitable for breeding, and so should be neutered when he is old enough (at least 6 months old). During the neutering operation, they will remove the undescended testicle and that will remove that possibility for health complications. This procedure is a bit more extensive and little more expensive than just a plain neutering, but it must be done.
Pure bred dogs can get sick and have health problems just like any other animal, so whether or not the dog is pure bred is not a factor. However, if you were sold a dog having serious health problems or serious congenital defects, a reputable breeder should make good on it in one way or another. An undescended testicle is not usually a serious health problem, but as mentioned, is more cos tly at neutering time, which usually warrants a similar discount in the price for the dog.
:My five month old maltese Coco has had either a urinary tract infection or bladder infection for over three weeks, has been on anibiotics for this period, Vet wants to x-ray bladder tomorrow, anyone out there with similar problems? He also has blocked tear ducts and a retracted testicle, ( this was supposed to be a pure bred ) ha ha