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In-Depth Information
hemolysis on a special blood agar known as Wagatsuma blood agar
(Wagatsuma, 1968) ( Table 5.3 ) . Epidemiological studies have indicated
that specifi c clones of certain serotypes, notably 03 : K6 having enhanced
virulence have become endemically established in certain global locals.
Table 5.3 Composition of Wagatsuma's medium
(Wagatsuma, 1968) a
Yeast extract 5.0g
Peptone 10.0
Mannitol 5.0
K 2 HPO 4 5.0
NaCl 70.0
Agar 15.0
dH 2 O 1.0L
a Final pH is 7.5. 5% defi brinated and washed
rabbit or human red blood cells are added after
sterilization of medium.
Ecology of V. parahaemolyticus
V. parahaemolyticus is widespread along marine coastal waters globally.
The organism is considered a common inhabitant of estuaries and is
infrequently found in freshwater or full-strength seawater (Joseph et al.,
1982). The organism is cold sensitive and appears to be limited to inshore
coastal and estuarine areas. Counts of V. parahaemolyticus have been found
to be as high as 1,300/g in oysters (Felsenfeld and Cabirac, 1977) which is
of considerable public health importance keeping in mind the widespread
practice of consuming shellfi sh raw or undercooked.
Antigenic Properties
Three principle categories of outer antigens are produced by strains
of V. parahaemolyticus : thermostable somatic O antigens, thermolabile
K antigens, and fl agellar antigens. The complete antigenic scheme for
V. parahaemolyticus encompassing both O and K antigens is given by Twedt
Direct Acting Hemolysins
Hemolysis on Wagatsuma's blood agar ( Table 5.3 ) is referred to as the
Kanagawa phenomenon (KP) and has been found to correlate well
with human pathogenicity. The KP phenomenon is characterized by the
appearance on “Wagatsuma Agar” of a sizeable clear halo of hemolysis after
18 to 24 h of incubation at 37°C. The presence of 7% NaCl in Wagatsuma agar
( Table 5.3 ) is thought to stress the cells resulting in enhanced production of
hemolysin. The use of serological detection of the hemolysin has resulted
in some KP - strains being designated weak KP + (Ohashi et al., 1977).
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