Microbial inhibition methods

A comparison was made between this approach and the microbial inhibition method (Bacillus stearothermophilus disk assay according to [77]). No significant differences were found for AMO and AMP residues in milk within the reliable detection range of the microbial inhibition assay. The LC method was found more sensitive than the microbial inhibition method for residues lower than 10 yUg/L (78,79). 

The CHARM II test for tissues is relatively fast, easy to perform, and requires limited laboratory equipment. However, for antibacterials with established tolerance levels, it can serve only as a screening test because the results are not quantitative and therefore should be supported by additional quantitative chemical methods. The microbial receptor assay, with its broad-spectrum capability, can enhance any existing monitoring system as a first-line monitoring test or as a confirmation for any program using microbial inhibition tests. 

Application of some kind of sample treatment may have the potential to improve substantially the detection of certain antibacterials in milk by microbial routine methods (59). Treatment, for example, of milk samples with ammonium oxalate solution prior to analysis can lead to lower limits of detection of tetracyclines by both microbial inhibition and microbial receptor assays. This is due to the fact that tetracycline residues tend to form chelates with divalent cations and bind to proteins, which reduce their antibacterial efficacy. However, the oxalate treatment causes splitting of complex and/or protein bonds without increasing the detection limits of other antibacterials commonly used in dairy cows. 

A new analytical method was based on the treatment of SAs with p-aminobenzoic acid, forming derivatives suitable for UV detection. The SAs were extracted from the kidney and liver samples, with recoveries ranging from 55% to 100%. The reaction yield was tested by microbial inhibition tests sensitive to low concentrations of SAs. After the incubation with / -aminobenzoic acid, none of eight SAs produced an inhibition zone on the assay medium, which showed 100% conversion to the appropriate derivatives (162). 

C Ang, W Luo, CR Kiessling, K McKim, R Lochmann, CC Walker, HC Thompson. A bridging study between liquid chromatography and microbial inhibition assay methods for determining amoxicillin residues in catfish muscle. J AOAC Int 81 33-39, 1998. 

Furthermore, what is considered active is subjective. While one researcher might consider microbial inhibition at 1% as active, another would only consider activities of less than 0.025% to be active. Since test methods vary greatly, it is difficult to compare the results directly. In addition, the different methods tend to lead to different results due to many issues including, but not limited to, solubility and solvent choice. When standards are used, it is important to consider structurally related standards with similar solubilities in water. 

Microbial transformation method along with SAR studies has provided some novel metabolites that inhibit cholesterol biosynthesis. The phosphorylated derivatives (16 and 17) were produced by the conversion using several fungi [39]. Also, L-669262 (18) has been produced by microbial transformation of simvastatin, which is more active than simvastatin, its parent compound [40]. 

Stehly GR, Gingerich WH, Kiessling CR, Cutting JH, A bridging study for oxytetracycline in the edible fillet of rainbow trout Analysis by a liquid chromatographic method and the official microbial inhibition assay, J. AO AC Int. 1999 82(4) 866-870. 

Three methods may be used for the enumeration membrane filtration, plate count, and most probable number (MPN) method. The advantages of the membrane filter method are its low limit of detection (LOD) of < 1 CFU/g or mL and the efficient separation of the micro-organisms from components of the product, particularly antimicrobial agents. For the pour-plate method, the sample is generally 1 10 dissolved in the diluent, and 1 mL of the dilution is mixed with the agar. This corresponds to a LOD of 10 CFU/g or mL. The LOD is sometimes higher (e.g. 100 CFU/g or mL) if the product needs to be further diluted due to microbial inhibition, or lower in case of products with low microbial acceptance criteria. If the spread plate count technique is used the LOD is a factor of ten higher (>100 CFU/g or mL), because only 0.1 mL of the... 

Wheat protein-based materials are biodegradable and environment-friendly (27). A biodegradation study was performed in liquid medium using the standard ISO 14852 method. The wheat protein-based materials were completely degraded after 36 days (Figure 3) and no microbial inhibition due to toxic metabolite excretion was noted. 

Because the halogenated hydantoins are anchored and do not readily release fi ee chlorine, conventional methods for demonstrating antimicrobial efficacy based on the diffusive release of fi ee biocide into the local microenvironment— the so-called zone of microbial inhibition— cannot be applied. Inhibitory zones are minimal under circumstances where the challenge method depends on the slow release of biocides into an area populated by growing organisms, the net effect of which is to kill those which fall within a range of concentrations that is lethal. Retention of Cl on the grafted hydantoin demands that a test method be... 

A preservative is a substance that prevents or inhibits microbial growth and extends the shelf life of the drug products. In most pharmaceutical drug products, only a few compounds are typically selected as preservatives. For efficiency, a generic method should be developed for the types of preservatives that are more commonly used. For example, butylated hydroxytoluene (BHT) is an antioxidant commonly used in many solid dosage formulations to retard oxidative degradation of the excipients. 

The monitoring of cyanide with microbial sensor is possible in two ways. The first principle is based on the inhibition of respiration of Saccharomyces cervisiae by cyanide [102, 103]. This sensor showed a linear response in the range 0-15 pmol 1 by a response time of approximately 10 min and a stability of 9 days. Another method for the determination of cyanide is enabled by the use of cyanide-degrading microorganisms such as Pseudomonas fluorescens [1041. This bacterium specifically oxidizes cyanide by consuming oxygen ... 

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