Antibiotics are the chemotherapeutic agents that kill or inhibit the pathogenic microorganisms. Resistance of microorganism to antibiotics is a growing problem around the world due to indiscriminate and irrational use of antibiotics. In order to overcome the resistance problem and to safely use antibiotics, the correct measurement of potency and bioactivity of antibiotics is essential. Microbiological assay and high performance liquid chromatography (HPLC) method are used to quantify the potency of antibiotics. HPLC method is commonly used for the quantification of potency of antibiotics, but unable to determine the bioactivity; whereas microbiological assay estimates both potency and bioactivity of antibiotics. Additionally, bioassay is used to estimate the effective dose against antibiotic resistant microbes.Simultaneously, microbiological assay addresses the several parameters such as minimal inhibitory concentration (MIC), minimum bactericidal concentration (MBC), mutation prevention concentration (MPC) and critical concentration (Ccr) which are used to describe the potency in a more informative way. Microbiological assay is a simple, sensitive, precise and cost effective method which gives reproducible results similar to HPLC. However, the HPLC cannot be a complete substitute for microbiological assay and both methods have their own significance to obtain more realistic and precise results.

The aim of this study was to develop and validate a simple, sensitive, precise and cost-effective one-level agar diffusion (5+1) bioassay for estimation of potency and bioactivity of Levofloxacin in pharmaceutical preparation which has not yet been reported in any pharmacopoeia. Among 16 microbial strains, Bacillus pumilus ATCC-14884 was selected as the most significant strain against Levofloxacin. Bioassay was optimized by investigating several factors such as buffer pH, inoculums concentration and reference standard concentration. Identification of Levofloxacin in commercial sample Levoflox tablet was done by FTIR spectroscopy. Mean potency recovery value for Levofloxacin in Levoflox tablet was estimated as 100.90%. A validated bioassay method showed linearity (r2=0.988), precision (Interday RSD=1.05%, between analyst RSD=1.02%) and accuracy (101.23%, RSD=0.72%). Bioassay was correlated with HPLC using same sample and estimated potencies were 100.90% and 99.37%, respectively. Results show that bioassay is a suitable method for estimation of potency and bioactivity of Levofloxacin pharmaceutical preparations.

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Cefuroxime is a semi-synthetic antibiotic of the cephalosporin group and has broad-spectrum antimicrobial activity. HPLC methods, detailed in various pharmacopoeias, are generally used for the quantitative determination of the potency of cefuroxime but are unable to determine its bioactivity against microorganisms. In comparison to HPLC methods bioassay methods are simple and inexpensive however, a bioassay for the determination of both the potency and bioactivity of cefuroxime has not yet been reported in any pharmacopoeia. This article is focused on the development of a bioassay method for the quantification of cefuroxime axetil in pharmaceutical preparations. The bioassay was performed with different microbial strains and Kocuria rhizophila ATCC-9341 was selected as the most susceptible microorganism against cefuroxime axetil. The percent potency of market samples were estimated by a two-level bioassay method. The potency of market samples of Biocef, Ceftech and Ceftum were found to be 100.71% (RSD 1.09%), 101.07% (RSD 1.16%) and 100.44% (RSD 1.08%), respectively. The Biocef intermediate precision RSD between days and between analysts were 1.08% and 1.01%, respectively. The specificity of the bioassay for the analysis of Biocef was also studied in parallel with the Pharmacopoeial HPLC method and the potency was calculated as 101.09%. Resultsshow that a bioassay method can be used for the quality control of cefuroxime axetil in raw materials and pharmaceutical preparations.