178
T. BERGAN
I. GENERAL INTRODUCTION
Shigellosis constitutes a- very significant problem on a world scale.
Historically, dysentery has decided the fate of battles, due to epidemics
within army contingents, but today-at least in regions with a developed
sewage and food control system--it is particularly associated with closed
communities with deficient hygiene or close contact such as between
inmates of mental institutions, children’s homes, prisons, refugee or deportation camps. Often, explosive epidemics are caused by contaminated
milk, or milk products like butter, cheese, ice cream as well as lettuce, or
contaminated water (ZieschC and Rische, 1973). In many countries, e.g. in
Scandinavia, shigellosis is now infrequent and usually not endemic,
but reflects imported cases, Shigella sonnei dominates with only rare
isolates of S. flexne-ri. In the U.S.A., S . sonnei constitutes some 85%
and S . Jexneri about 14% of the shigellae (Pruneda and Farmer, 1977).
S. sonnei is also the most important species in Japan and large parts of
Africa (ZieschC and Rische, 1973). In non-industrialised countries, S.
dysenteriae is more frequent than in industrialised nations, where S. sonnei
and S . flexneri are the dominating species.
A factor that would tend to select for S. flexneri and S. sonnei is the circumstance that these species survive longer outside the body, in e.g. water,
milk, and other foods (Nass, 1965; Steltzner and Urbach, 1969; ZieschC
and Rische, 1973).
Elucidating the source of a Sh$ella infection may present a considerable
problem. Phage typing of the isolates may be an essential tool in both
endemic and epidemic situations. Typing may be the only way to determine
the source of infection of persons who have been exposed to several possible sources. In our days of rapid transport, it may be important that the
type of an infecting strain be recognised as identical to one that dominates
in a particular geographical area through which the patient has recently
travelled.
Shigella has been typed by a number of procedures such as serological
typing, biotyping, and bacteriocin typing, in addition to phage typing.
Serotyping is not sufficiently distinctive in an epidemiological context, but
is invaluable for species diagnosis in this genus (aide infra).
Phage typing is of particular significance, because it enables subtyping of
each serotype and therefore is satisfactory for efficient epidemiological
tracing. For S. dysenteriae and S . boydii, for which phage typing would be
of considerable importance in large parts of the world, only few reports
have appeared (Bercovici et al., 1972; Goldhar and Eylan, 1974; Goldhar
et al., 1974). In contrast, the number of different phage typing sets for S.
sonnei and S. Jexneri have proliferated. Many typing sets have been used
T. BERGAN
I. GENERAL INTRODUCTION
Shigellosis constitutes a- very significant problem on a world scale.
Historically, dysentery has decided the fate of battles, due to epidemics
within army contingents, but today-at least in regions with a developed
sewage and food control system--it is particularly associated with closed
communities with deficient hygiene or close contact such as between
inmates of mental institutions, children’s homes, prisons, refugee or deportation camps. Often, explosive epidemics are caused by contaminated
milk, or milk products like butter, cheese, ice cream as well as lettuce, or
contaminated water (ZieschC and Rische, 1973). In many countries, e.g. in
Scandinavia, shigellosis is now infrequent and usually not endemic,
but reflects imported cases, Shigella sonnei dominates with only rare
isolates of S. flexne-ri. In the U.S.A., S . sonnei constitutes some 85%
and S . Jexneri about 14% of the shigellae (Pruneda and Farmer, 1977).
S. sonnei is also the most important species in Japan and large parts of
Africa (ZieschC and Rische, 1973). In non-industrialised countries, S.
dysenteriae is more frequent than in industrialised nations, where S. sonnei
and S . flexneri are the dominating species.
A factor that would tend to select for S. flexneri and S. sonnei is the circumstance that these species survive longer outside the body, in e.g. water,
milk, and other foods (Nass, 1965; Steltzner and Urbach, 1969; ZieschC
and Rische, 1973).
Elucidating the source of a Sh$ella infection may present a considerable
problem. Phage typing of the isolates may be an essential tool in both
endemic and epidemic situations. Typing may be the only way to determine
the source of infection of persons who have been exposed to several possible sources. In our days of rapid transport, it may be important that the
type of an infecting strain be recognised as identical to one that dominates
in a particular geographical area through which the patient has recently
travelled.
Shigella has been typed by a number of procedures such as serological
typing, biotyping, and bacteriocin typing, in addition to phage typing.
Serotyping is not sufficiently distinctive in an epidemiological context, but
is invaluable for species diagnosis in this genus (aide infra).
Phage typing is of particular significance, because it enables subtyping of
each serotype and therefore is satisfactory for efficient epidemiological
tracing. For S. dysenteriae and S . boydii, for which phage typing would be
of considerable importance in large parts of the world, only few reports
have appeared (Bercovici et al., 1972; Goldhar and Eylan, 1974; Goldhar
et al., 1974). In contrast, the number of different phage typing sets for S.
sonnei and S. Jexneri have proliferated. Many typing sets have been used