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Abstract
Differences in pathogenesis and niches have made Salmonella Newport and S. Kentucky interesting subjects for the study of genetic variability. S. Kentucky is one of the most common serotypes isolated from chickens; however it is not often associated with human infections. S. Newport is not only a common serotype isolated from dairy cattle but is also associated with human infections and has developed resistance to multiple antibiotics. In this study a diverse set of Salmonella isolates (n=34) were selected from the National Antimicrobial Resistance Monitoring System (NARMS). DNA was extracted from these Salmonella isolates and subjected to comparative genomic hybridizations (CGH) to a Salmonella whole genome array containing genes from 5 different Salmonella serotypes(Typhimurium LT2, Typhi strain CT18, Typhi Ty2, Paratyphi A, and Enteritidis SPT4). Absence versus presence results of the 5,660 genes on the array were analyzed by Bionumerics (V 6.0, Applied Maths Austin, TX, USA). Data from CGH studies and published genomes of S. Newport and Kentucky (NCBI database) were compared to the Salmonella used as probes for CGH using MAUVE (The University ofWisconsin-Madison, Madison, WI, USA). CGH of S. Newport revealed high genomic similarity within MDR strains of Newport which is consistent with previous findings. S. Newport contained most of the phages found in S. Typhimurium while these phages were absent in S. Kentucky. Also, S. Newport contained several Salmonella pathogenicity virulence genes. Genetic variability was measured using MAUVE; 100 unique genes were found in S. Newport and 162 unique genes were found in S. Kentucky. Although these organisms have very similar genomes enough genetic variability exists to allow them to survive in different niches or environments. This may also include the ability of S. Newport to invade and colonize the gastrointestinal tracts of humans more efficiently than S. Kentucky.