Multiplex Polymerase Chain Reactions (PCR)
for Clostridiumperfringens (alpha, beta, epsilon,
iota and entero toxins) Genotyping
This new test is available at ADDL Bacteriology Lab. The
cost is $15 per isolate. Each isolate will be tested against
four typing toxins: type A Clostridium perfringens
contains only alpha toxin, type B, alpha, beta and epsilon
toxins, type C, alpha and beta toxins, type D, alpha and
epsilon and type E, alpha and iota toxins. In addition to
the detection of typing toxins, each isolate will be tested
for the presence of enterotoxin. Thus, the results can be
"Type A" or "Type Aenterotoxigenic,"
or "Type B," or "Type B enterotoxigenic,"
etc.
Clostridium perfringens, a common inhabitant of
the gastrointestinal track of warm blooded animals, as well
as terrestrial, marine and aquatic environments may be the
most widely occurring bacterial pathogen. It causes several
forms of enteric disease, including fetal enterotoxemias
in domestic animals and human. The virulence of the organism
is associated with the production of as many as 17 exotoxins
and four of these (alpha, beta, epsilon and iota), the so-called
typing toxins, form the basis for division of species into
5 toxigenic types.
Detection of the major toxins in clinical specimens has
been one item of key evidence in the diagnosis of clostridial
enteritis. Enterotoxin is considered by many to be a virulence
attribute in animal strains of C. perfringens and
it may be produced by any of the 5 typing strains. Dependence
on in vivo methods for toxin detection has become
a limiting factor in routine diagnosis. In vitro
tests using molecular approaches to identify toxin genes
and/or immunological assays to detect toxins have been established
in a few labs in the United
States. The key question
is can the genotyping be correlated with the phenotyping?
Based on the report of Dr. Glen Songer at the Annual AAVLD
meeting, genotyping determined by the multiplex PCR is 99-100%
correlated with the phenotyping. Actually, one of the phenotypedstrain
was found to be incorrect based on the genotyping. Dr. Songer
and co-workers also found that 95% (N=344) of C. perfringens
isolated from domestic animal and human are type A, and
12.8% of these contains enterotoxin. The remaining 5% of
isolates he studied were types B, C, D or E. However, the
report didn't address the correlation of toxin levels in
the gut or feces of infected animal to the genotypes of
the isolates. This may be due to the lack of accurate and
cost effective test for clostridial toxin detection. (However,
please consult the lab if you need to test for toxins.)
In January, a total of 34 cases have been genotyped by ADDL.
Twenty seven were found to be type A(~80%), three type E,
two type C and one type A enterotoxigenic. There was one
untypable culture.
- prepared by ChingChingWu, DVM,PhD
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