MOLECULR DIVERSITY AMONG Salmonella ISOLATES FROM MAN AND ANIMALS WITH SPECIAL REFERENCE TO NON-HOST SPECIFIC SEROVARS
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Date
2015-07
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Assam Agricultural University, Khanapara, Guwahati
Abstract
Salmonellae are important food-borne pathogens responsible for diseases in animals and man. It is an important zoonotic pathogen and a leading cause of many outbreaks and infections around the globe. It is a major cause of human gastroenteritis worldwide.
The present study was undertaken with a view to isolate Salmonella from various sources including animals, birds and human, to study their virulence gene profiles based on an multiplex PCR assay developed for the purpose and to compare three molecular typing methods, viz. rep-PCR, PFGE and plasmid profiling for their efficacy to discriminate and subtype Salmonella isolates belonging to different serovars.
Out of a total of 332 samples from various sources examined, 10 (3.01%) were found to be positive for Salmonella. The isolates belonged to three different serovars, Salmonella Enteritidis being the most predominant (40%), isolated from cattle, pig and Human. The other serovars recovered were Weltevreden (30%) and Newport (10%), while the remaining isolates were untypable (20%).
A multiplex PCR assay was developed for rapid detection of nine important virulence genes of Salmonella, viz. sipA, sipB, sipC, stn, sefC, spvA, spvB, spvC and sopB. Isolates belonging to different serovars showed variable results in respect of possession of different virulence genes. The virulence genes sipA, sipB, sipC, stn and sopB were detected in all (100%) the Salmonella isolates under the present study, while the sefC gene was present in only 34 (45.94%) of the 74 isolates. The rest three virulence genes spvA, spvB, and spvC were found to be present in 24 (32.43%) isolates. Most of the isolates (17) carrying all the nine genes under the study were recovered from poultry.
On application and analysis of three molecular typing methods, viz. rep-PCR, PFGE, plasmid profiling, it was found that PFGE could clearly differentiate among the strains belonging to different serovars and rep-PCR could differentiate between strains belonging to different serovars as well as between strains within the same serovar, while plasmid profiling had comparatively lower discriminatory power. On the basis of the findings of the present study, it could be suggested that a combination of PFGE and rep-PCR would prove to be more useful and appropriate for molecular typing of Salmonella isolates during epidemiological investigations.
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