The Use of Phage as Diagnostic Systems

Abstract

Abstract The most common use of bacteriophage in detection methodology is phage typing. When developing panels of phage which will discriminate between isolates of the same species on the basis of lytic spectrum, phage are chosen specifically because of their narrow (and therefore discriminatory) host range. Since this is the use of phage most commonly encountered, a general impression has been created that phage have a narrow host range. Hence, one of the most commonly voiced criticisms of phage-based detection methods is that the host range of phage and therefore any test is limited, but this is far from the truth. When phage are selected for detection of species or of whole genera, those with the widest host range are chosen. A classic example of this is the phage Felix 01, first described as a broad-host-range phage infecting Salmonella enterica by Cherry et al. (8). Subsequent extensive studies of its host range have shown that it will usually infect more than 95% of Salmonella isolates (see 16 for a review). Similarly, in the Gram-positive genera, listeriaphage A511 was reported to infect 95% of the two major serotypes of Listeria associated with human disease (serotypes 1/2a and 4b; 17). More recently, systematic searches for broad-host-range lytic phage have demonstrated that they can be readily isolated from natural communities where the different bacterial genera are likely to be found (14). Hence, phage-based detection tests have been successfully developed, although few have met with commercial success.