Reduction and refinement of murine models of bacterial infection

Aims

This research aimed to reduce the use of animals in the investigation of clinically-relevant bacterial diseases by developing and implementing a method of monitoring infection using bioluminescence.

Background

Infectious diseases are a major cause of mortality and morbidity worldwide. Mice are often used to investigate disease pathogenesis and to develop treatments. Traditionally, infected animals are killed at defined time points and tissues removed to determine localisation and degree of infection, and response to treatment; a six time point experiment would use up to 36 animals. Non-invasive detection of bacteria within live animals enables longitudinal monitoring and reduces the number of mice used by avoiding culling cohorts at various time points and allowing each animal to act as its own control.

Research details and methods

Plasmid vectors were developed for expression of luciferase in the targeted bacteria.  Infection and disease progression were monitored in real time in mice by bioluminescence imaging.

Key impacts and findings

The project developed a clinically-relevant bioluminescent strain of Streptococcus pyogenes, a Gram positive bacterium associated with a range of human diseases. By monitoring the bioluminescence, infected mice could be studied for around four days without the need to cull groups at pre-determined time points. This allowed the number of animals to be reduced by four-fold. The technique also provided more precise quantitation of the bacterial infectious dose, and revealed previously unknown niches of infection. The ability to identify mice in which the disease was progressing rapidly enabled the use of improved humane endpoints to minimise suffering. 

• Research Review 2011: Exploiting bioluminescence in mouse studies of bacterial infection