Dear Sethiya , I will give you another example, Doxcycyclin as bacteriostatic antibiotic with another bactericidal antibiotics as clarithromycin and PPI as triple therapy in H. pylori eradication.

The co-administration of antibiotic does not depend if they are bacteriostatic or bactericidal, depend on how they act together (antagonistic, synergistic or  additive action). What may happen some times is that bactericidal antibiotics kill better proliferating cells (actively growing), and the inclusion of a bacteriostatic antibiotic can arrest the growth and prevent the killing by the bactericidal one, but it depend on the combination. Hope this help.

Dear Alexandro

Can you comments on combination of Lincomycin and Colistin, and Levofloxacin and colistin

Some brief explanation here

Tetracyclines and penicillin (combination of bacteriostatic and bactericidal): Antagonistic action: Not recommended to use together

It’s a different scenario to combining tetracyclines and penicillin as they are different classes of antibiotic, and both are cidal as opposed to the latter combo (one cidal and one static). Yes, that’s because amino glycosides act at a different site on the bacterial cell than the penicillins do. Aminoglycosides kill by inhibiting bacterial protein synthesis and penicillins kill by cell wall formation inhibition. Of course it needs new peptidoglycan, cause it needs to divide into two, remember? If not, there won’t be enough peptidoglycan for the cell to give rise to 2 progeny cells.

The combination of trimethoprim and sulfamethoxizole are used together because they inhibit successive steps in the folic acid pathway and therefore act synergistically. The choice for antibiotic use is determined by the likely organism the drug is to target. For example, gram positive, gram negative, mycoplasma, pseudomonas, etc. You wouldn't use a macrolide and a tetracycline together because they are both inhibitors of protein synthesis and would target the same type of bacteria although they are both bacteriostatic. You are more likely to use penicillin and an aminoglycoside together because they will provide synergy even though they are both bacteriocidal.

Combination of Lincomycin and Colistin (combination of bacteriostatic and bactericidal): Lincomycin acts by inhibition of protein synthesis of Gram positive bacteria, whereas colistin is a bactericidal drug that binds to lipopolysaccharides and phospholipids in the outer cell membrane of Gram-negative bacteria. It competitively displaces divalent cations from the phosphate groups of membrane lipids, which leads to disruption of the outer cell membrane, leakage of intracellular contents, and bacterial death.

Combination of Levofloxacin and Colistin (combination of bacteriostatic and bactericidal):

Levofloxacin is a broad-spectrum antibiotic that is active against both Gram-positive and Gram-negative bacteria. Like all quinolones, it functions by inhibiting the two type II topoisomerase enzymes, namely DNA gyrase and topoisomerase IV. Topoisomerase IV is necessary to separate DNA that has been replicated (doubled) prior to bacterial cell division. With the DNA not being separated, the process is stopped, and the bacterium cannot divide. DNA gyrase, on the other hand, is responsible for supercoiling the DNA, so that it will fit in the newly formed cells. Both mechanisms amount to killing the bacterium, that is, levofloxacin acts as a bactericide. Whereas colistin is a bactericidal drug that binds to lipopolysaccharides and phospholipids in the outer cell membrane of Gram-negative bacteria. It competitively displaces divalent cations from the phosphate groups of membrane lipids, which leads to disruption of the outer cell membrane, leakage of intracellular contents, and bacterial death.

what a disadvantages of mixing two drug bacteriostatic and bactericidal

The tetracyclines are bacteriostatic against many Grampositive and Gram-negative bacteria and are also active against rickettsiae, Mycoplasma, Chlamydia, which cause lymphogranuloma venerum, psittacosis and trachoma, as well as amoebae.

Dear sir

i think it is better when you make combination to combine 2 drugs act by different mechanisms rather than their mode of killing, the mode of killing depends on the clinical situation, bacterial load and drug concentration, Aminoglycosides are classified as bacteriostatic by some authors. At higher concentrations, however, aminoglycosides display a very rapid bactericidal effect

simply because there’s no additional benefits of doing so.

Taking an example of Tetracycline & Penicillin

Tetracycline halts protein synthesis which is crucial for bacterial cell to replicate. Cells do not have enough protein to get ready for replication. Thus, it will not divide.

As for penicillin, it acts by inhibiting the cross-linking of nascent peptidoglycan, only when there is a newly synthesized peptidoglycan when cells are replicating.

putting both of medication together:

tetracycline will eventually stop bacterial replication, so no synthesis of new peptidoglycans.

without new peptidoglycans, there will be no cross-linking, then penicillin cannot elicit its response.

It's believed that they antagonize each other. Thus reducing efficacy. That has been held believe for up to 50years now. More scientific evidence is required to disprove this argument.