11. SEROTYPING OF LISTERIA MONOCYTOGENES AND RELATED SPECIES 47
This also seems true for many other isolates from similar sources which
are also non-haemolysing (as shown by the CAMP-test as the most
sensitive method) and not virulent and which show a similar antigenic
make-up. Such isolates have not been designated any further, since they
are obviously closely related to serotypes 4f and 4g. A survey of antigen
combinations so far determined in the authors’ laboratory is given in
Table VII.
These strains are Listeria incertae sedzi (L. innocua) and should not be
confused with classical L. monocytogenes.
L. monocytogenes isolates from pathological sources almost invariably
belong to serotypes 1/2a, 1/2b and 1/2c, 3a, 3b, and 3c, 4b and 5 ( L . monocytogenes sub judice!). They represent over 98% of several thousand
cultures studied by the senior author since 1951.
The distribution of serotypes throughout the world is not uniform.
I n the U.S.A. and Canada serotype 4b prevails at a proportion of 65% to
80% of all strains (King and Seeliger, 1959). I n the Eastern European
countries, in West Africa, in Central Germany, Finland and Sweden
serotype 1/2a is most frequently found, while in Western Europe, particularly in France (Seeliger and Linzenmeier, 1955 ; Lucas and Seeliger
1957; Hohne et al., 1975) and in the Netherlands (Kampelmacher et al.,
1966) serotypes 1/2a and 4b are being isolated in about the same proportion. I n Western Germany serotype 1/2a prevailed until 1958. Since
then a definite shift toward serotype 4b has been noted which in some
outbreaks prevailed.
Serological differentiation has been of great help in the identification of
suspected cultures, but no progress in the elucidation of the epidemiology
and epizootiology of listeriosis has resulted from this work. As a matter of
fact serotypes 1/2a and 4b have been isolated even from the same animal,
or the mother has excreted a serotype different from that of her listeric
child. These observations are indicative of mixed infections rather than of
serological instability of the organisms.
G. Cross-reactions
Overlapping serological reactions between the Listeria serotypes and
other species of bacteria have repeatedly been observed. Comparative
studies have constantly demonstrated a serological dissimilarity between
L. monocytogenes and strains of the Erysipelothrix group (Barber, 1939;
Julianelle and Pons, 1939). Seeliger found some enterococcus strains which
were strongly agglutinated by Listeria serotypes 4a and 4b antiserum, but
not by sera of the other serotypes. Some serological cross-reactions were
also reported between Listeria and certain E . coli strains (Jaeger and Myers,
1954). The same applies to L. monocytogenes and Staphylococcus aureus
This also seems true for many other isolates from similar sources which
are also non-haemolysing (as shown by the CAMP-test as the most
sensitive method) and not virulent and which show a similar antigenic
make-up. Such isolates have not been designated any further, since they
are obviously closely related to serotypes 4f and 4g. A survey of antigen
combinations so far determined in the authors’ laboratory is given in
Table VII.
These strains are Listeria incertae sedzi (L. innocua) and should not be
confused with classical L. monocytogenes.
L. monocytogenes isolates from pathological sources almost invariably
belong to serotypes 1/2a, 1/2b and 1/2c, 3a, 3b, and 3c, 4b and 5 ( L . monocytogenes sub judice!). They represent over 98% of several thousand
cultures studied by the senior author since 1951.
The distribution of serotypes throughout the world is not uniform.
I n the U.S.A. and Canada serotype 4b prevails at a proportion of 65% to
80% of all strains (King and Seeliger, 1959). I n the Eastern European
countries, in West Africa, in Central Germany, Finland and Sweden
serotype 1/2a is most frequently found, while in Western Europe, particularly in France (Seeliger and Linzenmeier, 1955 ; Lucas and Seeliger
1957; Hohne et al., 1975) and in the Netherlands (Kampelmacher et al.,
1966) serotypes 1/2a and 4b are being isolated in about the same proportion. I n Western Germany serotype 1/2a prevailed until 1958. Since
then a definite shift toward serotype 4b has been noted which in some
outbreaks prevailed.
Serological differentiation has been of great help in the identification of
suspected cultures, but no progress in the elucidation of the epidemiology
and epizootiology of listeriosis has resulted from this work. As a matter of
fact serotypes 1/2a and 4b have been isolated even from the same animal,
or the mother has excreted a serotype different from that of her listeric
child. These observations are indicative of mixed infections rather than of
serological instability of the organisms.
G. Cross-reactions
Overlapping serological reactions between the Listeria serotypes and
other species of bacteria have repeatedly been observed. Comparative
studies have constantly demonstrated a serological dissimilarity between
L. monocytogenes and strains of the Erysipelothrix group (Barber, 1939;
Julianelle and Pons, 1939). Seeliger found some enterococcus strains which
were strongly agglutinated by Listeria serotypes 4a and 4b antiserum, but
not by sera of the other serotypes. Some serological cross-reactions were
also reported between Listeria and certain E . coli strains (Jaeger and Myers,
1954). The same applies to L. monocytogenes and Staphylococcus aureus