11. BEROTYPING OF LIS7ERIA MONOCY7'OGENE.S AND RELATED SPECIES 37
specimens collected in nature (Weiss and Seeliger, 1975 ; Seeliger, 1975 ;
Seeliger, 1976). These isolates usually are devoid of any animal pathogenicity and belong to a group of serotypes listed in Table VII.
They are, in the writer's opinion, not true L. monocytogenes and may
represent a different, closely related species.
I n case of doubt, the lack of haemolysing properties should always be
demonstrated by the CAMP test as described by Brzin and Seeliger (1974),
if horse blood is not available (see below).
As shown in Fig. 1 L. monocytogenes-classical serotypes show a very
distinct P-haemolysis, which differs from the much stronger haemolytic
action of serotype 5 of Ivanov. The serotypes 4f and 4g as well as related
varieties completely lack haemolysis and belong to a new spacies, Listeria
innocua (Seeliger and Schoofs, 1977).
C. The CAMPphenomenon in Listeria
The CAMP phenomenon is a simple and accurate method of identifying
Streptococcus agalactiae. Since the reliability in this aspect is high (only
about 2-474 of Strept. agalactiae are CAMP negative (Munch-Petersen,
1947)) it was adopted as a routine test as early as 1947 in the New York
State Mastitis Control Programme. The explanation for the phenomenon
still awaits clarification. T h e nature of the so-called haemolysis accentuating factor produced by CAMP positive streptococci is as yet unknown.
Christie and co-workers stated that the agent is an extracellular filtrable
product, quite stable at high temperatures.
Method
A culture of Staphylococcus aureus capable of producing a large zone of
weak p haemolysis is streaked across the centre of a blood agar medium.
A colony of the Listeria under examination is streaked perpendicular to
and within 3 mm of the line of staphylococcus inoculation. The culture is
incubated at 37°C overnight and then checked to see if the haemolysis is
accentuated (cf. Brzin and Seeliger, 1974).
Since it is suspected that in some samples of blood (sheep- or calf-blood)
staphylococcal haemolysin inhibiting substances are present the erythrocytes are first washed.
As positive control a typical Strept. agalactiae strain and a strain of
L. monocytogenes serotype 1/2a or 4b are included.
A positive CAMP reaction is indicated by a semicircular or arrowheadshaped zone of complete lysis of the erythrocytes around the staphylococcal
streak (Fig. 1). The outer line of the accentuated haemolysis is completely
straight (Fraser, 1962).
Performed in the same way with a perpendicular streak, the CAMP test
specimens collected in nature (Weiss and Seeliger, 1975 ; Seeliger, 1975 ;
Seeliger, 1976). These isolates usually are devoid of any animal pathogenicity and belong to a group of serotypes listed in Table VII.
They are, in the writer's opinion, not true L. monocytogenes and may
represent a different, closely related species.
I n case of doubt, the lack of haemolysing properties should always be
demonstrated by the CAMP test as described by Brzin and Seeliger (1974),
if horse blood is not available (see below).
As shown in Fig. 1 L. monocytogenes-classical serotypes show a very
distinct P-haemolysis, which differs from the much stronger haemolytic
action of serotype 5 of Ivanov. The serotypes 4f and 4g as well as related
varieties completely lack haemolysis and belong to a new spacies, Listeria
innocua (Seeliger and Schoofs, 1977).
C. The CAMPphenomenon in Listeria
The CAMP phenomenon is a simple and accurate method of identifying
Streptococcus agalactiae. Since the reliability in this aspect is high (only
about 2-474 of Strept. agalactiae are CAMP negative (Munch-Petersen,
1947)) it was adopted as a routine test as early as 1947 in the New York
State Mastitis Control Programme. The explanation for the phenomenon
still awaits clarification. T h e nature of the so-called haemolysis accentuating factor produced by CAMP positive streptococci is as yet unknown.
Christie and co-workers stated that the agent is an extracellular filtrable
product, quite stable at high temperatures.
Method
A culture of Staphylococcus aureus capable of producing a large zone of
weak p haemolysis is streaked across the centre of a blood agar medium.
A colony of the Listeria under examination is streaked perpendicular to
and within 3 mm of the line of staphylococcus inoculation. The culture is
incubated at 37°C overnight and then checked to see if the haemolysis is
accentuated (cf. Brzin and Seeliger, 1974).
Since it is suspected that in some samples of blood (sheep- or calf-blood)
staphylococcal haemolysin inhibiting substances are present the erythrocytes are first washed.
As positive control a typical Strept. agalactiae strain and a strain of
L. monocytogenes serotype 1/2a or 4b are included.
A positive CAMP reaction is indicated by a semicircular or arrowheadshaped zone of complete lysis of the erythrocytes around the staphylococcal
streak (Fig. 1). The outer line of the accentuated haemolysis is completely
straight (Fraser, 1962).
Performed in the same way with a perpendicular streak, the CAMP test