Abstract
ABSTRACT Emergence of multidrug-resistant (MDR) Salmonella enterica serovar Indiana (S. Indiana), a dominant Salmonella serovar in China, has raised global awareness because the MDR S. Indiana also was rapidly emerged in other countries recently. To improve our understanding of underlying MDR mechanism and evolution of this emerging zoonotic pathogen, here we examined the standard ATCC51959 strain together with 19 diverse and representative Chinese S. Indiana strains by performing comprehensive microbiological, molecular, and comparative genomics analyses. The findings from S1-PFGE, plasmid origin analysis and Southern blotting suggested the MDR phenotype in the majority of isolates was associated with large integron-carrying plasmids. Interestingly, further in-depth analyses of two recently isolated, plasmid-free MDR S. Indiana revealed a long chromosomal class I integron (7.8 kb) that is not linked to the Salmonella Genome Island 1 (SGI1), which is rare. This unique chromosomal integron shares extremely high similarity to that identified in a MDR E. coli plasmid pLM6771 with respect to both genomic organization and sequence identity. Taken together, both plasmid and chromosomal integron I exist in the examined MDR S. Indiana strains. This timely study represents a significant step toward the understanding of molecular basis of the emerging MDR S. Indiana.
Highlights
Antimicrobial resistant bacteria pose a significant threat for livestock production, food safety and public health [1]
There are over 2600 recognized Salmonella serovars
Some uncommon serovars can arise as prevalent serovars in specific geographic locations [19]
Summary
Antimicrobial resistant bacteria pose a significant threat for livestock production, food safety and public health [1]. The frequent reports of Gram-negative superbugs, those resistant to extended-spectrum cephalosporins, carbapenem, and colistin, have aroused global concern [2]. Salmonella spp. are important foodborne pathogens, to which the elderly, children and immunocompromised people were more susceptible. Antibiotics are still the priority choice for prevention and treatment of salmonellosis because Salmonella spp. usually show a lower resistance rate than other Gramnegative bacteria, such as Escherichia coli and Klebsiella spp [3]. The recent emergence of multidrug-resistant (MDR) Salmonella enterica serovar Indiana Indiana) in China has raised global awareness [4]
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