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Detection of class 1 integrons in Salmonella Weltevreden and silent antibiotic resistance genes in some seafoodâassociated nontyphoidal isolates of Salmonella in southâwest coast of India
- Deekshit, V.K., Kumar, B.K., Rai, P., Srikumar, S., Karunasagar, I., Karunasagar, I.
- Journal of applied microbiology 2012 v.112 no.6 pp. 1113-1122
- Salmonella enterica subsp. enterica serovar Newport, Salmonella enterica subsp. enterica serovar Weltevreden, ammonium compounds, antibiotic resistance, antibiotics, bacteria, coasts, genes, multiple drug resistance, polymerase chain reaction, seafoods, India
- Aims: To study the antibiogram of 40 seafood isolates of Salmonella and use of PCR to detect the presence of integrons and genes coding for antibiotic resistance. Methods and Results: In this study, 40 isolates of Salmonella were used for antibiogram analysis. The multidrugâresistant isolates were analyzed for the presence of integron using integronâspecific primers. Twentyâfive percentage of the isolates were multidrug resistant while 67Â·50% were resistant to at least two antibiotics. Antibiotic resistance genes catA1 and tetA were present in 57Â·52 and 60%, respectively. Although widespread presence of genes was observed, only 26Â·08% of the catA1âcarrying isolates exhibited phenotypic resistance against the respective antibiotic. Integrons present in representative isolates of Salmonella Weltevreden and Salmonella Newport were sequenced. The former contained class 1 integron with a single gene dfrA7 in the integron cassette and an adjacent dihydropteroate synthetase gene along with the usual quaternary ammonium compound resistance gene, while the later contained class 1 integron with dhfrA1, OrfC, in the integron cassette and an adjacent dihydropteroate synthetase gene along with the usual quaternary ammonium compound resistance gene. Conclusions: This study demonstrates the presence of silent antibiotic resistance genes and class I integrons in seafoodâassociated Salmonella strains. The study also demonstrates the first report of class I integron in Salm.Â Weltevreden. Detection of catA1 genes in phenotypically sensitive bacteria suggests that these could be reservoirs in the environment. Significance and Impact of the Study: The manuscript provides novel results describing the existence of a high rate of antibiotic resistance in the Salmonella populations prevailing in environmental sources as well as an absence of correspondence between the presence of antibiotic resistance genes, and the exhibition of a the corresponding phenotypic trait of resistance against the respective antibiotic compound was observed. In addition, the manuscript reports the presence of the class I integron in Salm.Â Weltevreden.