Virulence tests

The emergence of multidrag-resistant microorganism strains requires novel methods for antimicrobial resistance and virulence testing. The functional assays for establishing drag resistance, reviewed here, are based on MS and stable isotopes... 

Demirev P. Emerging instrumental methods for antimicrobial resistance and virulence testing. In Havlicek V, Spizek J, editors. Natural products analysis instrumentation, methods, and applications. New Jersey Wiley 2014. p. 25—42. 

With attenuated viral vaccines the potential hazards are those associated with reversion of the virus during production to a degree of virulence capable of causing disease in vaccinees. To a large extent this possibility is controlled by very careful selection of a stable seed but, especially with live attenuated poliomyelitis vaccine, it is usual to compare the neurovirulence of the vaccine with that of a vaccine known to be safe in field use. The technique involves the intraspinal inoculation of monkeys with a reference vaccine and with the test vaccine and a comparison ofthe neurological lesions and symptoms, if any, that are caused. If the vaccine causes abnormalities in excess of those caused by the reference it fails the test. 

Wigdorovitz et al. [39] used a TMV expression vector to produce VP1, the 26-kDa structural protein from FMDV, and tested it in mice. Mice injected intraperitoneally with leaf extracts prepared from infected plants mounted an antibody response against the plant-derived protein. All immunized mice were protected when challenged with virulent FMDV. One-year old calves immunized with plant extracts containing VP1 also developed FMDV-specific antibody responses. 

Leithoff, H., Peek, R.D., Borck, V., Gottsche, R., Kirk, H. and Grinda, M. (1999). Toxic values derived from EN113 tests—are they determined by the virulence of the test fungus —Results from a round robin test. International Research Group on Wood Preservation, Doc. No. IRGAVP 99-20176. 

In a subsequent study calves were experimentally infected orally with a sublethal dose of the calf virulent strain S. typhimurium SVA44 and skin tested 3 weeks later (Table I) (57). 

Tier 2 also include host resistance models, tests in which an animal is exposed to a xenobiotic and then challenged with an infectious agent or tumor cells. This is considered the ultimate test for an adverse effect on the immune system. However, it should be noted that the amount of immune suppression that can be tolerated is greatly dependent on the dose and virulence of the challenging agent, as well as the genetics of the host. Manipulation of these variables can affect greatly results obtained in host resistance tests. 

The major concerns with vaccine production are firstly, is the virus harmless and secondly is the vaccine free of adventitious agents. If the vaccine is produced from a virulent virus it is essential that the virus is completely inactivated before vaccine distribution. If attenuated strains are used the stability of the attenuation must be monitored. In both cases cell cultures are used in tests. 

Extraneous contamination can be a problem and the use of human serum is discouraged since early batches of yellow fever vaccine became contaminated with hepatitis B virus. For similar reasons normal human diploid fibroblast strains are the preferred cells as they can be shown to be free, not only of contaminating virulent viruses but also of transforming viruses (Furesz et al 1988). Such cells have replaced primary cells but they must be regularly tested for... 

One of the most serious problems on plant disease control is the virulence of virus diseases. Trials to develop antiviral antibiotics have been enthusiastically conducted by many workers. Consequently, many antibiotics have been revealed to be effective on inhibiting the multiplication of several plant viruses by in vitro test and pot test. They are blasticidin S, laurusin, bihoromycin, miharamycin, citrinin and aabomycin A etc. However,... 

Virulence and Potency Testing Live attenuated viral vaccines are considered to have a theoretical risk of reversion to virulence that needs to be tested. This is done by monitoring genetic or phenotypic markers of attenuation or virulence and can include in vitro and in vivo potency tests [62],... 

Effects of mammalian sera on avirulent and virulent bacteria were determined by using attenuated (BCG) and virulent (H37Rv) strains of tubercle bacilli and avirulent (strain A) and virulent (strain C) strains of E. coli. All strains were obtained from the culture collection of the Department of Microbiology, Miami University. Bacterial virulence and the infection-promoting effect of iron were determined in Swiss-Webster mice. The degree of virulence of tubercle bacilli for iron-untreated and iron-treated mice has been shown previously (2). In this study, the pathogenicity of E. coli strains was tested by three experiments in which groups of 10 mice were injected intraperitoneally with 5 X 108 cells of strain A and strain C. Mice infected with the strain C died within two days whereas 80-90% of mice inoculated with strain A survived the infection. On the basis of these and several similar experiments (see... 

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