Individually ventilated cages – Microbiological containment testing

Abstract

Modern biomedical research projects need “high quality” laboratory animals in order to obtain repeatability and homogeneity of the experimental data and to reduce the number of animals. It is, thus necessary to use animals standardised with respect to genetic, microbiological and pathological conditions. Environmental control, by eliminating the chemical, physical and microbial contaminants, can guarantee more standardised housing conditions and, at the same time, highly reduce the biological risk for the personnel working with the animals in accordance with the European and Italian legislation. Among the physical parameters temperature and humidity have to be considered the most important for their influence on animal behavior and metabolism. The optimal values for temperature range between 20 and 23 °C and for humidity between 40 and 60 %; in fact it has been widely demonstrated that when these two parameters are too high, they enhance the growth of moulds and the life span of microorganisms and that most bacteria and fungi, that colonize man and animals, grow at temperatures between 25 and 40 °C.

Microbiological quality assurance of laboratory animals aims to produce animals that meet requirements for microbiological quality, and to maintain the same quality throughout the experiment. Outbreaks of infectious disease in laboratory animals have to a great extent adversely affected their use in biomedical research. Some microorganisms occurring in laboratory animals can also affect man (zoonosis) and this risk is also present in animals which are used as a source of sera and vaccines for use in man. Due to the introduction of specified pathogen free (SPF) animals outbreaks of infectious diseases have been in part replaced by more subtle microbial interference in the outcome of animal experiments. Plenty of viruses, mycoplasma, bacteria and parasites that may affect biomedical research exist for all laboratory animal species (Boot, 1996).

The Service for Quality and Assurance of Animal Experimentation routinely controls the animal housing environment. For several years it has been focusing its activity on monitoring microbiological conditions and even in the animal housing it has considered the indication of Whittard (Table 1), as acceptable levels of contamination. With regard to this problem we have analyzed the count of environmental microorganisms in the animal facility rooms and the isolating capacity of a ventilated cage system (IVC, Techniplast Gazzada, Varese, Italy) which has been conceived to protect, by filtering the supply and exhaust circulating air, both the housed animals and the working personnel. The experiment has been performed in a conventional animal facility to verify the possibility to use animals in mixed conditions i.e. animals housed in normal conditions and animals housed in IVC.