As a matter of principle whenever two or more drugs are combined in fixed dosages, the rationality of fixed drug combination (FDC) has to be proved. Any FDC of which rationality is not proved is deemed to be irrational. Therefore one cannot seek reasons for irrationality. The FDC of cefoperazone + sulbactum has not been approved by US FDA despite the fact that cefoperazone is the research molecule of Pfizer, an American company. In some other developed countries such as Britain and Australia, cefoperazone has been discarded and is no more marketed. By and large, ceftazidime and cefotaxime are considered superior to cefoperazone. In fact there is no condition where cefoperazone alone or concurrently with sulbactum is the drug of choice.
Cefixime with lactobacillus is not a rational combination. Such a combination is not approved in any advanced country.