102
A. SARAGEA ET AL.
3000 C. diphtheriae strains from abroad, the additional scheme is more
likely to undergo further developments. The system on which it is partly
based, i.e. the plasticity of the highly virulent 951 “L” phage and the
possibility to restrict it in previously phage-resistant bacteria, makes it
possible to obtain new specific phages for strains from different areas of the
world.
2. Practical value and egiciency of the additional phage typing scheme
Both schemes are useful epidemiological tools. The original one for
situations of epidemic occurrence of gravis toxf and/or intermedius toxf, and
of some intermedius tox- C. diphtheriae strains, the additional scheme for
endemic or post-epidemic situations, when tox- C. diphtheriae strains
generally prevail.
However, there are circumstances in which the latter phage typing
scheme can also be useful in epidemic situations. One particular type, for
instance, type “K”, displaying sensitivity against host restricted phage
no. 23, has characterised a large number of intermedius tox+ strains from an
outbreak in San Antonio, Texas, in 1972 (McCloskey et al., 1972). It was
thus possible by means of this additional type to differentiate and elucidate
the double source of infection of this epidemic (gravis toxf, original phage
type XIV in one section of the population and intermedius toxf additional
phage type “K” in another). Phage type “K” has two receptors, one for the
additional phage 23, which produces strong lytic reactions, and the other
irregularly sensitive to the original phage 11. This phage type is widespread
throughout the south-west U.S.A. and Canada (Toshach et al., 1977).
After the outbreak mentioned above, this type was identified by the authors
among strains isolated from Indian reservations in New Mexico and
Arizona. It seems to be an endemic ancestral type in the U.S.A. rather than
a recent import. It was also frequently isolated from cutaneous lesions, leg
ulcers, nose and ear suppurations in Canadian eskimoes.
The use of the additional phage typing scheme enabled the authors to
follow changes in the distribution of C. diphtheriae strains in Romania in
the post-epidemic period, to study the distribution of healthy carriers and
of atypical clinical forms. Among the additional phage types, the most
frequent was gravis tox- phage type “L”.
It is still the prevalent phage type in healthy carriers, and is followed in
order of frequency by phage types B, D, J and A.
3. Subtypes of the original intermedius phage type V
During the development of the additional phage typing scheme it was
observed that two intermedius tox- strains, belonging to original phage type
V, commonly isolated from healthy carriers, showed different lytic patterns
A. SARAGEA ET AL.
3000 C. diphtheriae strains from abroad, the additional scheme is more
likely to undergo further developments. The system on which it is partly
based, i.e. the plasticity of the highly virulent 951 “L” phage and the
possibility to restrict it in previously phage-resistant bacteria, makes it
possible to obtain new specific phages for strains from different areas of the
world.
2. Practical value and egiciency of the additional phage typing scheme
Both schemes are useful epidemiological tools. The original one for
situations of epidemic occurrence of gravis toxf and/or intermedius toxf, and
of some intermedius tox- C. diphtheriae strains, the additional scheme for
endemic or post-epidemic situations, when tox- C. diphtheriae strains
generally prevail.
However, there are circumstances in which the latter phage typing
scheme can also be useful in epidemic situations. One particular type, for
instance, type “K”, displaying sensitivity against host restricted phage
no. 23, has characterised a large number of intermedius tox+ strains from an
outbreak in San Antonio, Texas, in 1972 (McCloskey et al., 1972). It was
thus possible by means of this additional type to differentiate and elucidate
the double source of infection of this epidemic (gravis toxf, original phage
type XIV in one section of the population and intermedius toxf additional
phage type “K” in another). Phage type “K” has two receptors, one for the
additional phage 23, which produces strong lytic reactions, and the other
irregularly sensitive to the original phage 11. This phage type is widespread
throughout the south-west U.S.A. and Canada (Toshach et al., 1977).
After the outbreak mentioned above, this type was identified by the authors
among strains isolated from Indian reservations in New Mexico and
Arizona. It seems to be an endemic ancestral type in the U.S.A. rather than
a recent import. It was also frequently isolated from cutaneous lesions, leg
ulcers, nose and ear suppurations in Canadian eskimoes.
The use of the additional phage typing scheme enabled the authors to
follow changes in the distribution of C. diphtheriae strains in Romania in
the post-epidemic period, to study the distribution of healthy carriers and
of atypical clinical forms. Among the additional phage types, the most
frequent was gravis tox- phage type “L”.
It is still the prevalent phage type in healthy carriers, and is followed in
order of frequency by phage types B, D, J and A.
3. Subtypes of the original intermedius phage type V
During the development of the additional phage typing scheme it was
observed that two intermedius tox- strains, belonging to original phage type
V, commonly isolated from healthy carriers, showed different lytic patterns