Two bacteriophages of Clostridium difficile

Abstract

Two temperate bacteriophages of differing morphology and host range were isolated by screening 94 isolates of Clostridium difficile. Phage 41 had a 300-nm flexible tail, whereas phage 56 had a shorter tail with a contractile sheath. Electron microscopy of phage 56 lysates exposed to elevated magnesium concentrations showed small virus-like particles which were 21 nm in diameter. The addition of MgCl2 to semisolid agar overlays enhanced both the titer and plaque size of phage 56. Phage 56 was more temperature labile than phage 41 and demonstrated unusual lability in buffer at pH 7.0. One-step growth and adsorption experiments revealed that both phages had latent periods of about 60 min, but phage 56 adsorbed to its indicator strain more efficiently. Phage 56, which was obtained from a toxigenic strain of C. difficile, was used to lysogenize its

Electron microscopic investigation of lysogeny of Clostridium difficile strains isolated from antibiotic‐associated diarrhea cases and from healthy carriers

“…Most of the intact phages resembled phage type BI, with a hexagonal head of varying size and a long noncontractile tail. This tail displayed a special flexibility in the phages found in strains 9 and 25 (Figure le), similar to that in phage 41 found by Mahony et al (9). Three C. difficile strains (strains 1 1 , 29 and 30) harbored a hexagonal phage head without a tail, resembling phage type D2.…”

“…There have been only a few communications about phages active on C. dgficile or obtained viously described clostridial phages. Mahony et al (9) tested 94 strains of C. dfficile and isolated only two spontaneously released bacteriophages (2%) (phage 41 and phage 56), active against four and five other C. dfficile strains, respectively. Both phages were fully characterized.…”

“…weight were present in non-toxigenic isolates as well (8), and thus it could not be confirmed that they are involved in toxin production. Phages have recently been isolated from C. diffi'cile strains (2,9,11,14) and some of them have been used for the typing of clinical isolates (12,14,17). Most of the phages were isolated from lysogenic C. difficile strains after mitomycin C induction (14), or they were spontaneously released (9).…”

“…Most of the phages were isolated from lysogenic C. difficile strains after mitomycin C induction (14), or they were spontaneously released (9). Only a small percent (4 or 2%, respectively) of the strains tested proved to harbor phage particles which could be propagated on a limited number of indicator strains (9,14). It has been suggested that the toxin production may be phage-mediated.…”

“…It has been suggested that the toxin production may be phage-mediated. Mahony et al (9) and Schallehn (1 3 ) recently examined this possibility, but could not convert non-toxigenic strains to toxin producers. The frequency of lysogenic strains revealed by plaque assays seems to be very low among C. difficile.…”