Microbiological RMs

The most difficult situations are encountered with living organisms or substances for which activities must be measured. BCR has developed storage in gelatine capsules for microbiological RMs and CRMs [16]. 

Steffan RJ, RM Atlas (1991) Polymerase chain reactions, applications in environmental microbiology. Annu... 

Bartha R. Atlas RM. 1977. The microbiology of oil spills. Adv Appl Microbiol 22 225-266. 

Akers MJ, Taylor CJ. Official methods of preservative evaluation and testing. In Denyer SP, Baird RM, eds. Guide to Microbiological Control in Pharmaceuticals. London Elhs Horwood, 1990 292-303. 

The size of the droplets in food emulsions varies considerably and may range from 0.1 gtn to more than 20 /rm. Consequently proper characterization of the droplet size distribution is important, not only because of the above mentioned texture related reasons, but also in view of microbiological aspects. 

Paterson IC, Chamley AK, Cooper RM, Clarkson JM Partial characterization of specific inducers of a cuticle-degrading protease from the insect pathogenic fungus Metarhizium anisopliae. Microbiology 1994 140 3153-3159. 

Alsop RM (1983) In Bushell ME (ed) Progress in industrial microbiology. Elsevier, Amsterdam,... 

Bossert I, Bartha R. 1984. The fate of petroleum in soil ecosystems. In Atlas RM, ed. Petroleum microbiology. New York, NY MacMillan Publishing Company, 435-473. 

As described above, microbiological measurements are of a different nature than chemical measurements. Nevertheless, the needs for quality control are similar. RMs and CRMs are only available from a few suppliers and their use is linked to the type of material delivered. Capsules of RMs available from SVM in the Netherlands and lenticules from PHLS propose the same type of approach. These materials are added to the matrix — water or food — before the measurement procedure starts. BCR-CRMs... 

Despite the burning need for RMs and CRMs in microbiological measurement disciplines only very few materials exist. Basically, the type of materials, in terms of objectives, necessary for chemists are also needed by microbiologists. 

In all cases, the analyst will count cfp. The RMs of BCR are not certified through most probable number techniques (MPN). Microbiological CRMs are always certified through (a) given method(s) i.e. the certified value depends upon the analytical method. For all these reasons and particularities, special rules for the use of CRMs in microbiology have been developed by RIVM for BCR. The following sections dealing with the use of CRMs are directly extracted from a report prepared by J.A. van Dommelen [12]. 

In principle, the certification of RMs for microbiological parameters does not differ from the approach used by BCR for chemical parameters. They fall into the category of method-dependent CRMs certified for an activity. In fact, the microbes will behave differently from one type of method (in particular the culture medium) to another. For selective media the resuscitation rate of the microbes in the RM will change. Injured bacteria will have difficulties to form colonies on these media. This reflects the biological activity of the strain after stabilisation. As the method will strongly affect the result, it must be verified that the method was applied in a similar way by all participants. This means that accurate protocols have been prepared and tested beforehand in a feasibility study. The first step of the evaluation of the certification study will be to verify that the protocol was strictly followed. This protocol will be made available to the users of the CRM. 

Two parallel improvement programmes have been started in 1986 for the development of RMs and possibly CRMs for the quality control of microbiological determinations. The first project focused on target bacteria important for monitoring food of which the CRMs are fully described in chapter 7 the second project dealt with water contaminants. These studies have been described in details elsewhere [35] and are summarised below. The projects had two objectives ... 

Taylor GR, Graves RM, Brock-Ett RM, Ferguson JK, Mieszkuc BJ. Skylab environmental and crew microbiology studies. 1977 NASASP-377. 

Metabolite Profiles in Liver. The total radioactive residue in all 12 livers was efficiently extracted with a mixture of formic, trifluoroacetic, and hydrochloric acids. After neutralization of the acids with ammonium hydroxide and partial purification by solid phase extraction techniques, HPLC/RAM analysis produced essentially a two-component profile. The minor component was pirlimycin itself in relative amounts of 27.6% 9.7%. The bulk of the residue, 77%, was a single substance and was identified by co-chromatography with an authentic standard and by FAB/MS as pirlimycin sulfoxide (PS). The microbiological analysis of the extracts confirmed this relative ratio since PS has an antibiotic activity 142 times less than that of pirlimycin against M.luteus. The ratio of pirlimycin to total residue was therefore established and will provide the necessary correlation of residue depletion needed for the calculation of residue marker concentration (Rm) and the establishment of a tissue withdrawal period. 

The composition of the material and the parameters investigated should remain unchanged over the entire period of use of the material. The study of the material stability in time will mainly depend on its role. If the material is going to be used in a short term interlaboratory study, the stability has to be monitored only over the real duration of the exercise and additionally mimic situations which may be encountered during its short lifetime, e.g. transport under severe climatic conditions. This may vary from some hours (e.g. microbiological samples) to several years for a CRM. The (in)stability should be studied or known before the RM is produced and should be monitored on the batch of RM. 

RM Baird. Preservative efficacy testing in the pharmaceutical industries. In MRW Brown, P Gilbert, eds. Microbiological Quahty Assurance A Guide Towards Relevance and Reproducibility of Inocula. New York CRC Press, 1995, pp. 149-162. 

Skyring GW, Lynch RM, Smith GD. In Cohen Y, Rosenberg E, eds. Microbial Mats Physiological Ecology of Benthic Microbial Communities. Washington, D.C. American Society for Microbiology, 1989 170-179. 

Donlan RM (2001) Biofilm formation a clinically relevant microbiological process. Clin Infect Dis 33 1387-1392... 

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