98
A. SARAGEA E‘I‘ AL.
widespread phage type among gravis type strains was phage type XIV
which caused moderately severe cases. Subsequently it was followed by
XIV “a” phage type, isolated from all outbreaks, occurring in sanatoria
where children with poliomyelitis sequelae were concentrated.
Phage type XVI characterised a very large and severe outbreak in 1960,
phage type XI1 two other severe and large outbreaks, and phage type
VIII “a”, only one outbreak in 1962.
Subsequently phage type IX alone has been prevalent in all epidemics
but at present is found in only very rare, sporadic cases (one to two cases
yearly) all over the country. Phage types XI11 and XVII have not been
epidemic in Romania. The latter was identified in 1968 in only two healthy
carriers, who had come in contact with tourists from Hungary, where this
type was more common. Mitis phage types I, Ia, I1 and 111, intermedius
IV, V, VI and gravis non-toxigenic VII were only isolated from healthy
carriers and in non-epidemic areas.
In conclusion: by means of this scheme it has been possible to characterise 73% of all C. diphtheriae strains isolated in Romania during the epidemic period of 1956-1967, and 62% of strains received from other
geographical areas. Among strains isolated from other countries 99% of
the gravis strains were typable by this scheme.
The prevalence of a certain epidemic phage type could be followed in
various parts of the world. For instance phage type XVI has been identified
in a collection of strains isolated in Australia as long ago as 1938.
The same phage type was identified during the last decade in Europe
(Italy, Jugoslavia, Hungary) and Canada (Vancouver). Mitis I “a” has been
identified in the U.S.A. and Canada but never in Europe, before it suddenly appeared in Hungary in 1974. Some of the individuals carrying this
type had been visiting relatives in the U.S.A. one month before.
9. Limitations of the method
Worthy of note is the smaller typing capacity of the biotypes intermedius tox- and mitis tox- (39 and 19% respectively). These two biotypes
are more frequently isolated from healthy carriers and in non-epidemic
areas or periods. The failures of the “original” phage-typing scheme
indicate that while complete for gravis toxf strains the “original” basic
set of typing phages has to be supplemented for mitis, intermedius and
gravis tox- in order to increase the typability among these three biotypes to
higher levels.
The limits of this method, which became more evident in the postepidemic period of diphtheria in Romania recently, led to the development
of an additional phage-typing scheme (Maximescu et al., 1972).
A. SARAGEA E‘I‘ AL.
widespread phage type among gravis type strains was phage type XIV
which caused moderately severe cases. Subsequently it was followed by
XIV “a” phage type, isolated from all outbreaks, occurring in sanatoria
where children with poliomyelitis sequelae were concentrated.
Phage type XVI characterised a very large and severe outbreak in 1960,
phage type XI1 two other severe and large outbreaks, and phage type
VIII “a”, only one outbreak in 1962.
Subsequently phage type IX alone has been prevalent in all epidemics
but at present is found in only very rare, sporadic cases (one to two cases
yearly) all over the country. Phage types XI11 and XVII have not been
epidemic in Romania. The latter was identified in 1968 in only two healthy
carriers, who had come in contact with tourists from Hungary, where this
type was more common. Mitis phage types I, Ia, I1 and 111, intermedius
IV, V, VI and gravis non-toxigenic VII were only isolated from healthy
carriers and in non-epidemic areas.
In conclusion: by means of this scheme it has been possible to characterise 73% of all C. diphtheriae strains isolated in Romania during the epidemic period of 1956-1967, and 62% of strains received from other
geographical areas. Among strains isolated from other countries 99% of
the gravis strains were typable by this scheme.
The prevalence of a certain epidemic phage type could be followed in
various parts of the world. For instance phage type XVI has been identified
in a collection of strains isolated in Australia as long ago as 1938.
The same phage type was identified during the last decade in Europe
(Italy, Jugoslavia, Hungary) and Canada (Vancouver). Mitis I “a” has been
identified in the U.S.A. and Canada but never in Europe, before it suddenly appeared in Hungary in 1974. Some of the individuals carrying this
type had been visiting relatives in the U.S.A. one month before.
9. Limitations of the method
Worthy of note is the smaller typing capacity of the biotypes intermedius tox- and mitis tox- (39 and 19% respectively). These two biotypes
are more frequently isolated from healthy carriers and in non-epidemic
areas or periods. The failures of the “original” phage-typing scheme
indicate that while complete for gravis toxf strains the “original” basic
set of typing phages has to be supplemented for mitis, intermedius and
gravis tox- in order to increase the typability among these three biotypes to
higher levels.
The limits of this method, which became more evident in the postepidemic period of diphtheria in Romania recently, led to the development
of an additional phage-typing scheme (Maximescu et al., 1972).