188
T. BERGAN
IV. BACTERIUM-PHAGE IN'I'ERAC'I'IONS
A. Source of Shigella bacteriophages
A large number of Shigella isolates are lysogenic (Hammarstrom, 1947,
1949; Quynh, 1967, 1969; Rische, 1968a, b). Among S. sonnei, the frequency of lysogenic strains has been analysed in a number of studies
(Table IV). Gromkova (1966) found that 12 of 30 strains were lysogenic,
some even polylysogenic. S. jexneri may be less lysogenic than S. sonnei.
Thus, Milch et al. (1968) using 11 indicators found only 9% lysogeny
among 272 strains. Lysogeny has also been determined in S. dysenteriae
and S . boydii (Bercovici et al., 1972; Goldhar and Eylan, 1974). Sh2ella
phages have also been isolated from residual waters (Bercovici et al., 1972).
B. Modification and restriction of phage DNA
Host modification and restriction of phages are well-known phenomena
in enterobacteriae. The phenomena are important in the phage typing
T A B L E V I
Frequency of lysogeny observed in S. sonnei
No. of
Procedure
Lysogeiiic
strains
of deterstrains (yo in
Reference
Year studied
mination
parenthesis)
Comments
Gromkova
Emelyanov
Stepenkovskajaa
Q v n h
Q w n h
ZieschC and
Rische
Chanishvili and
Chanishvili
1966
30
1966
120
1967
15
1968 1500
1969
97
1969
112
1973
1975
UV and
12(40)
spontaneous
Spontaneous
43(36)
Spontaneous
12(80)
UV
(45.2)
Spontaneous
29(30)
Spontaneous
3 5 (3 1)
(60)
84
Twenty-four of
the strains
were virulent
Donor strains of
same lysotype
used four
indicator strains
Used five indicator strains
Unpublished data
of Rische and
Horn
a Cited from Ziescht and Rische (1973) (in which not referenced).