prevalence and molecular characteristics of vibrio species in pre ...

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2.7.4 Genotypic characteristics of Vibrio
Researchers have investigated the phenotypic and genotypic characterization
of the Vibrio organism using new molecular technology based on the ribotyping and
polymerase chain reaction technique such as amplified fragmented length
polymorphism (AFLP), fluorescence in situ hybridization (FISH) or multi locus
sequence typing (MLST) (Thompson et al., 2004). Identification of toxigenic genes
and serogroups (Dalsgaard et al., 2001, Janssen et al., 1996, Raghunath et al., 2008),
genetic diversity (Jiang et al., 2000, Sawabe et al., 2002, Zo et al., 2002), ecological
interaction and relatedness of clinical and environmental isolates (Zo et al., 2002) of
Vibrio has been carried out with the help of new techniques. Toxigenic Vibrio
cholerae O1 samples from the aquatic environment and human intestines isolated
from Bangladesh were analyzed by enterobacterial repetitive intergenic consensus
sequence-PCR, optimized for profiling by using the fully sequenced V. cholerae E1
Tor N16961 genome. A study found a similar composition of environmental toxigenic
V. cholerae and the V. cholerae that causes the endemic cholera. Authors conclude
that the spatial and temporal fluctuation (seasonal fluctuations in the environment,
introduction of new strain) in the composition of the toxigenic V. cholerae population
in the aquatic environment can cause shifts in the dynamics of this disease (Zo et al.,
2002). An investigation carried out by Jiang et al. (2000) detected V. cholerae isolates
in Chesapeake Bay coastal waters. The genetic diversity analyzed by applying AFLP
fingerprinting revealed the link between the shift of the genotype and environmental
changes such as water temperature.
MLST was developed recently and considered as most reliable molecular tool
for the epidemiology. This method is based on the sequence analysis of housekeeping
(HK) genes of the organism. Higher discriminatory power, accuracy and portability of
the data, ease of performance, and reproducibility are major advantages of this
method (Thompson et al., 2004). Nucleic acid sequences are stored in a public data
base that can be easily accessed via internet (http://www.mlst.net or
http://pubmlst.org) (González-Escalona et al., 2008). Scientist applied this method to
determine the global epidemiology of bacterial pathogens. González-Escalona et al.