Development and validation of a microbiological agar assay for determination of orbifloxacin in pharmaceutical preparations

Assessment of Plasma Tylosin Concentrations: A Comparative Study of Immunoassay, Microbiological Assay, and Liquid Chromatography/Mass Spectrometry

Employing affordable and uncomplicated sample preparation techniques to recommend the most efficient antibacterial therapy could help reduce antibiotic-resistant bacteria. This study evaluated the suitability of immunoassays and microbiological assays as alternatives for liquid chromatography/mass spectrometry (LC/MS) in determining plasma tylosin concentrations after intramuscular administration at a dose of 20 mg/kg to both healthy and diseased pigs in clinical veterinary practice. The diseased pigs were confirmed using the target genes Actinobacillus pleuropneumoniae (apxIVA) and Pasteurella multocida (kmt1). The methods showed good linearity, precision, and accuracy. In both healthy and diseased pigs, a significant correlation was observed between LC/MS and the microbiological assay (Pearson correlation coefficient: 0.930, p < 0.001 vs. Pearson correlation coefficient: 0.950, p < 0.001) and between LC/MS and the enzyme-linked immunosorbent assay (ELISA) (Pearson correlation coefficient: 0.933; p < 0.001 vs. Pearson correlation coefficient: 0.976, p < 0.001). A strong correlation was observed between the microbiological assay and the ELISA in both healthy and diseased pigs (Pearson correlation coefficient: 0.911; p < 0.001 vs. Pearson correlation coefficient: 0.908, p < 0.001). A Bland-Altman analysis revealed good agreement between the methods, i.e., 95% of the differences were within the limits of agreement. Therefore, the microbiological assay and the ELISA, which demonstrated sufficient precision and accuracy, can be viable alternatives to LC/MS when it is unavailable.

Status of Physicochemical and Microbiological Analytical Methods of Gatifloxacin: A Review

Background

Gatifloxacin (GAT), an antimicrobial of the fourth generation of fluoroquinolones, has a broad spectrum of action with activity against Gram-positive and Gram-negative, aerobic and anaerobic organisms, including mycobacteria.

Objective

The objective of this review is to discuss about (i) characteristics, (ii) properties, and (iii) analytical methods of gatifloxacin.

Results

Among the methods described in the literature for the evaluation of GAT, the most frequent was HPLC (50%) for both the analysis of pharmaceutical and biological matrixes. GAT has no monograph described in official compendia. Methods for evaluating GAT in pharmaceutical matrixes were the most found in the literature, 79%. Acetonitrile (42%), methanol (20%), and buffer solution (16%) were the most used diluents. GAT, being an antimicrobial, must be analyzed by physical-chemical and microbiological methods, since the evaluation of potency is essential. In this context, the literature is scarce (4%).

Conclusions

There is a gap in the literature for environmentally friendly methods for evaluating GAT. Faster, more optimized and dynamic microbiological methods, as well as physicochemical methods, use less aggressive solvents with fewer steps and less waste. Currently, pharmaceutical analyses require reliable analytical methods, but also safe for both the analyst and the environment.

Highlights

This review shows the status of analytical methods, both physicochemical and microbiological, for the analysis of GAT in pharmaceutical and biological matrixes, also addressing its context in green and sustainable analytical chemistry.

Uptake of Ozenoxacin and Other Quinolones in Gram-Positive Bacteria

The big problem of antimicrobial resistance is that it requires great efforts in the design of improved drugs which can quickly reach their target of action. Studies of antibiotic uptake and interaction with their target it is a key factor in this important challenge. We investigated the accumulation of ozenoxacin (OZN), moxifloxacin (MOX), levofloxacin (LVX), and ciprofloxacin (CIP) into the bacterial cells of 5 species, including Staphylococcus aureus (SA4-149), Staphylococcus epidermidis (SEP7602), Streptococcus pyogenes (SPY165), Streptococcus agalactiae (SAG146), and Enterococcus faecium (EF897) previously characterized.The concentration of quinolone uptake was estimated by agar disc-diffusion bioassay. Furthermore, we determined the inhibitory concentrations 50 (IC50) of OZN, MOX, LVX, and CIP against type II topoisomerases from S. aureus.The accumulation of OZN inside the bacterial cell was superior in comparison to MOX, LVX, and CIP in all tested species. The accumulation of OZN inside the bacterial cell was superior in comparison to MOX, LVX, and CIP in all tested species. The rapid penetration of OZN into the cell was reflected during the first minute of exposure with antibiotic values between 190 and 447 ng/mg (dry weight) of bacteria in all strains. Moreover, OZN showed the greatest inhibitory activity among the quinolones tested for both DNA gyrase and topoisomerase IV isolated from S. aureus with IC50 values of 10 and 0.5 mg/L, respectively. OZN intracellular concentration was significantly higher than that of MOX, LVX and CIP. All of these features may explain the higher in vitro activity of OZN compared to the other tested quinolones.

Miniaturized Microbiological Method to Determine the Potency of Rifaximin in Tablets

BACKGROUND

Rifaximin, a semi-synthetic antimicrobial, does not present microbiological method described in official compendia, and there is a lack of literature on this topic. The quality control of antimicrobials is extremely important to evaluate the real potency of pharmaceutical products.

OBJECTIVE

A miniaturized turbidimetric method for determining the potency of rifaximin in tablets was developed and validated by turbidimetry, according to the international guidelines.

METHOD

Escherichia coli ATCC 10536 IAL 2393, brain heart infusion (BHI) broth, inoculum at 8%, rifaximin in purified water with 20% ethanol at 5, 10, and 20 μg/mL and 530 nm were used.

RESULTS

The method was considered selective for rifaximin, as the adjuvants did not show activity; linear with correlation coefficients 0.9998 for standard and 0.9999 for sample; accurate with 99.73% recovery; precise with RSD less than 3%; and robust in the face of small variations in (i) rifaximin volume, (ii) proportion of ethanol, (iii) inoculum volume.

CONCLUSIONS

The method is considered adequate and safe to evaluate the potency of rifaximin in tablets, contemplating speed, low cost, low waste generation, and ease of operation.

HIGHLIGHTS

This work usescurrent, sustainable, and green analytical chemistry and can be used in the routine analyses of rifaximin by laboratories and the pharmaceutical industry around the world.

Analytical Methods for the Quality Control of Veterinary Antimicrobials Medicines

Veterinary medicinal products (VMPs) are used for the prevention and treatment of diseases in animals. The safety and efficacy of these products must be proven by quality control tests. Special attention should be paid to veterinary antimicrobials medicines (VAMs), as changes in their potency can compromise pharmacotherapeutic treatment and contribute to microbial resistance. The aim of this work was to review the analytical methods available for assessing the quality of VAMs, to analyze regulatory issues and quality control programs. The review was performed on selected papers in the PubMed, ScienceDirect, Scopus and Virtual Health Library databases, between 2005 and 2020. After applying exclusion criteria, 19 studies were obtained. Of the analytical studies, the majority (61.54%) used the HPLC technique. In addition, methods by CE (15.39%) and by SPM, FIA and microbiological assay (7.69% each) were found. In studies of monitoring of VAMs available on the market, changes in tylosin, spiramycin, ampicillin, tetracyclines and penicillins were observed. This is worrying, as these quality deviations can contribute to the development of resistant microorganisms. Although international efforts have been implemented at the regulatory level to ensure the quality of VAMs, it was realized with this study that there is much to evolve in the development of new analytical methods and in monitoring the quality of VAMs. With this, it is expected that this study will instigate scientists in the analytical, regulatory, microbiological and veterinary fields to develop new research so that the demands necessary to guarantee the quality of VAMs are increasingly met.

Review for Analytical Methods for the Determination of Sodium Cephalothin

Infections are the second leading cause of global morbidity and mortality, therefore it is highly important to study the antimicrobial agents such as cephalosporins. Cephalothin, an antimicrobial agent that belongs to the class of cephalosporins, has bactericidal activity and it is widely used in the Brazilian health system. In literature, some analytical methods are found for the identification and quantification of this drug, which are essential for its quality control, which ensures maintaining the product characteristics, therapeutic efficacy and patient's safety. The aim of this article is to review the available information on analytical methods for cephalothin. Thus, this study presents a literature review on cephalothin and the analytical methods developed for the analysis of this drug in official and scientific papers. It is essential to note that most of the developed methods used toxic and hazardous solvents, which makes necessary industries and researchers choose to develop environmental-friendly techniques, which will contribute to the harmonization of science, human, and environmental health.

Besifloxacin: A Critical Review of Its Characteristics, Properties, and Analytical Methods

Bacterial conjunctivitis has high impact on the health of the population, since it represents more than a third of ocular pathologies reported by health services worldwide. There is a high incidence of bacterial resistance to the antimicrobials most commonly used for the treatment of conjunctivitis. In this context, besifloxacin stands out, since it is a fluoroquinolone developed exclusively for topical ophthalmic use, presenting a low risk of developing resistance due to its reduced systemic exposure. Bausch & Lomb markets it as ophthalmic suspension, under the trade name Besivance™. Literature review on besifloxacin is presented, covering its pharmaceutical and clinical characteristics, and the analytical methods used to measure the drug in pharmaceutical products and biological samples. High performance liquid chromatography is the most used method for this purpose. A discussion on Green Chemistry is also presented, focusing the importance of the development of green analytical methods for the analysis of drugs.

Selection of appropriate analytical tools to determine the potency and bioactivity of antibiotics and antibiotic resistance

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 Current Case of Quinolones: Synthetic Approaches and Antibacterial Activity

Quinolones are broad-spectrum synthetic antibacterial drugs first obtained during the synthesis of chloroquine. Nalidixic acid, the prototype of quinolones, first became available for clinical consumption in 1962 and was used mainly for urinary tract infections caused by Escherichia coli and other pathogenic Gram-negative bacteria. Recently, significant work has been carried out to synthesize novel quinolone analogues with enhanced activity and potential usage for the treatment of different bacterial diseases. These novel analogues are made by substitution at different sites--the variation at the C-6 and C-8 positions gives more effective drugs. Substitution of a fluorine atom at the C-6 position produces fluroquinolones, which account for a large proportion of the quinolones in clinical use. Among others, substitution of piperazine or methylpiperazine, pyrrolidinyl and piperidinyl rings also yields effective analogues. A total of twenty six analogues are reported in this review. The targets of quinolones are two bacterial enzymes of the class II topoisomerase family, namely gyrase and topoisomerase IV. Quinolones increase the concentration of drug-enzyme-DNA cleavage complexes and convert them into cellular toxins; as a result they are bactericidal. High bioavailability, relative low toxicity and favorable pharmacokinetics have resulted in the clinical success of fluoroquinolones and quinolones. Due to these superior properties, quinolones have been extensively utilized and this increased usage has resulted in some quinolone-resistant bacterial strains. Bacteria become resistant to quinolones by three mechanisms: (1) mutation in the target site (gyrase and/or topoisomerase IV) of quinolones; (2) plasmid-mediated resistance; and (3) chromosome-mediated quinolone resistance. In plasmid-mediated resistance, the efflux of quinolones is increased along with a decrease in the interaction of the drug with gyrase (topoisomerase IV). In the case of chromosome-mediated quinolone resistance, there is a decrease in the influx of the drug into the cell.

Development and validation of UV spectrophotometric method for orbifloxacin assay and dissolution studies

New, simple and cost effective UV-spectrophotometric method was developed for the estimation of orbifloxacin in pharmaceutical formulation. Orbifloxacin was estimated at 290 nm in 0.5 M hydrochloric acid. Linearity range was found to be 1.0-6.0 μg mL-1. The method was tested and validated for various parameters according to main guidelines. The proposed method was successfully applied for the determination of orbifloxacin in tablets. The results demonstrated that the procedure is accurate, precise and reproducible, while being simple, economical and less time consuming. It can be suitably applied for the estimation of orbifloxacin in routine quality control and dissolution studies.

Development and validation of microbial bioassay for quantification of Levofloxacin in pharmaceutical preparations

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.

Development and validation of a microbiological assay for determination of chlorhexidine digluconate in aqueous solution

Chlorhexidine (CHX) is a broad-spectrum antiseptic that is used in many topical pharmaceutical formulations. Because there is no official microbiological assay reported in the literature that is used to quantify CHX, this paper reports the development and validation of a simple, sensitive, accurate and reproducible agar diffusion method for the dosage of chlorhexidine digluconate (CHX-D) in an aqueous solution. The assay is based on the inhibitory effect of CHX-D upon the strain of Staphylococcus aureus ATCC 25923, which is used as the test microorganism. The design 3x3 parallel-line model was used. The results were treated statistically by analysis of variance (ANOVA), and they were excellent in terms of linearity (r = 0.9999), presenting a significant regression between the zone diameter of growth inhibition and the logarithm of the concentration within the range of 0.5 to 4.5%. The results obtained were precise, having relative standard deviations (RSD) for intra-day and inter-day precision of 2.03% and 2.94%, respectively. The accuracy was 99.03%. The method proved to be very useful and appropriate for the microbiological dosage of CHX-D in pharmaceutical formulations; it might also be used for routine drug analysis during quality control in pharmaceutical industries.

A novel and rapid microbiological assay for ciprofloxacin hydrochloride

The present work reports a simple, fast and sensitive microbiological assay applying the turbidimetric method for the determination of ciprofloxacin hydrochloride (CIPRO HCl) in ophthalmic solutions. The validation method yielded good results and included excellent linearity, precision, accuracy and specificity. The bioassay is based on the inhibitory effect of CIPRO HCl upon the strain of Staphylococcus epidermidis ATCC 12228 used as the test microorganism. The results were treated statistically by analysis of variance (ANOVA) and were found to be linear (r=0.9994, in the range of 14.0-56.0 µg/mL), precise (intraday RSD%=2.06; interday RSD%=2.30) and accurate (recovery=99.71%). The turbidimetric assay was compared to the UV spectrophotometric and HPLC methods for the same drug. The turbidimetric bioassay described on this paper for determination of ciprofloxacin hydrochloride in ophthalmic solution is an alternative to the physicochemical methods disclosed in the literature and can be used in quality control routine.

Development and validation of a successful microbiological agar assay for determination of ceftriaxone sodium in powder for injectable solution

Ceftriaxone sodium is a cephalosporin with broad-spectrum antimicrobial activity and belongs to the third generation of cephalosporins. Regarding the quality control of medicines, a validated microbiological assay for the determination of ceftriaxone sodium in powder for injectable solution has not been reported yet. This paper reports the development and validation of a simple, accurate and reproducible agar diffusion method to quantify ceftriaxone sodium in powder for injectable solution. The assay is based on the inhibitory effect of ceftriaxone sodium on the strain of Bacillus subtilis ATCC 9371 IAL 1027 used as test microorganism. The results were treated statistically by analysis of variance and were found to be linear (r = 0.999) in the selected range of 15.0-60.0 μg/mL, precise with a relative standard deviation (RSD) of repeatability intraday = 1.40%, accurate (100.46%) and robust with a RSD lower than 1.28%. The results demonstrated the validity of the proposed bioassay, which allows reliable ceftriaxone sodium quantitation in pharmaceutical samples and therefore can be used as a useful alternative methodology for the routine quality control of this medicine.