Microbiological Safety and Quality of Processed Shrimps and Fishes - Aquaculture Microbiology and Biotechnology - page 103

and Lockwood, 1981; Oliver et al., 1986), elastase (Kothary and Kreger,
1985; Oliver et al., 1986; Moreno and Landgraf, 1998), lipase (Desmond
et al., 1984; Oliver et al., 1986; Tison et al., 1982, Moreno and Landgraf,
1998), phospholipase (Desmond et al., 1984; Testa et al., 1984; Tison et al.,
1982), chondroitin sulfatase (Oliver et al ., 1986), hyaluronidase (Oliver
et al, . 1986), DNase (Desmond et al., 1984; Kreger and Lockwood, 1981;
Oliver et al., 1986, Moreno and Landgraf, 1998), mucinase (Oliver et al.,
1986; Moreno and Landgraf, 1998), fi brinolysin (Oliver et al., 1986), and
an alkaline sulfatase (Kitaura et al., 1983; Oliver et al., 1986). A heat-stable
hemolysin is produced that exhibits cytolytic activity against a variety of
mammalian erythrocytes, cytotoxic activity to Chinese hamster ovary cells,
vascular permeability to guinea pig skin, and lethality for mice (Kreger
and Lockwood, 1981) and has been utilized for molecular identifi cation of
the organism. This cytolysin- hemolysin toxin is encoded by the cth gene.
Enrichment and Isolation Media
Alkaline Peptone Salt (APS) Broth
APS Broth is widely used for enrichment cultivation of V. vulnifi cus
and is useful for MPN (Most Probable Number) enumeration followed
by streaking onto one of the selective agar media described below. The
medium consists of 1% peptone plus 3.0% NaCl. The pH is adjusted to 8.5
and therefore imparts some degree of selectivity for alkaline pH tolerant
marine vibrios such as V. vulnifi cus .
Thiosulfate-Citrate-Bile-Salts Sucrose (TCBS) Agar
Most isolation studies from marine sources have involved the use of TCBS
agar ( Table 5.1 ) to select for V. vulnifi cus although it is widely recognized
that signifi cant numbers of non-vibrios are also capable of growth on
this medium (Brayton et al., 1983; Oliver et al., 1983; West et al., 1982).
Because TCBS agar does not distinguish V. vulnifi cus from other sucrose-
negative vibrios, additional selective media have been developed for its
isolation. The identifi cation of lactose fermenting vibrios from seafood
with TCBS is much more diffi cult than from clinical sources. This is due
to the large number of sucrose-negative, lactose-positive vibrios in marine
environments that yield colonies on selective media such as TCBS agar that
are similar or identical in appearance to those produced by V. vulnifi cus
(Oliver et al., 1983).
Vibrio vulnifi cus Medium
Cerdà-Cuéllar et al . (2000) proposed a more selective medium for isolation
of V. vulnifi cus known as Vibrio vulnifi cus medium.This medium ( Table 5.1 )
contains polymyxin B and colistin but in addition has a pH of 8.5.