The current study was designed to demonstrate the microbiological quality of oral liquid antibiotics. The in vitro antibacterial potential of the antibiotics was checked. In this regard three samples of oral liquid suspension of Flucoxacillin collected from different drug stores of Dhaka city were tested. All the samples were found to be loaded with total viable bacteria and fungi in the average of 104 cfu/ml and the bacterial and fungal load exceeded United States Pharmacopeia (USP) or British Pharmacopeia (BP) limit (≤102 cfu/ml for bacteria and 10 cfu/ml for fungi). Pathogenic bacteria were also encountered among which Pseudomonas spp. was predominant as they found in all samples. Escherichia coli and Staphylococcus spp. were found in majority of the samples. All the samples ofantibiotic exhibited substantial killing effect on E. coli, Staphylococcus spp. and fungi. Flucoxacillin samples had effect on them. E. coli, Klebsiella spp., Staphylococcus spp. and fungi. Flucoxacillin had the elevated antimicrobial effect on Staphylococcus spp.