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ARS Home » Midwest Area » Ames, Iowa » National Animal Disease Center » Food Safety and Enteric Pathogens Research » Research » Publications at this Location » Publication #113808
Title: RELATIVE DISTRIBUTION AND SEMI-CONSERVATION OF GENES ENCODING AMINOGLYCOSIDE-MODIFYING ENZYMES IN SALMONELLA ENTERICA SEROTYPE TYPHIMURIUM PHAGETYPE DT104

Author
item FRANA, T - IOWA STATE UNIVERSITY
item Carlson, Steven
item GRIFFITH, R - IOWA STATE UNIVERSITY

Submitted to: Applied and Environmental Microbiology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 10/5/2000
Publication Date: N/A
Citation: N/A

Interpretive Summary: A genetic test was used to identify genes that provide resistance to aminoglycosides, a specific class of antibiotics, in 422 veterinary isolates of Salmonella. The isolates were collected from 32 states and various animal species in 1998. Identities of genes encoding resistance to streptomycin, gentamicin, kanamycin, and apramycin were evaluated. Gentamicin resistance was seen in 37 (8.7%) isolates and was conferred by the aadB gene. Kanamycin resistance was seen in 122 (29%) isolates and was encoded by the aphA1-Iab gene (111 isolates; 26%) or by the Kn gene (11 isolates; 3%). Apramycin resistance was seen in 24 (5.7%) isolates and was determined by the aacC4 gene. Analysis of gene distribution did not reveal significant differences with regards to animal host species, or region, except for the Kn gene, which was found mostly in nonclinical isolates. Streptomycin resistance was seen in all 422 isolates and was attributed to the aadA2 gene. The data from this study indicate that multiple antibiotic resistant Salmonella do not acquire aminoglycoside resistance genes in a species- or geographic-dependent manner, which supports clonal expansion (i.e., one bacterium spreads and gives rise to many more bacteria) as the method of spread of this organism.

Technical Abstract: PCR was used to identify genes encoding aminoglycoside-modifying enzymes in 422 veterinary isolates of Salmonella enterica serotype Typhimurium. The isolates were represented by various phagetypes (DT104, U302, DT193, DT208, DT120) collected from 32 states and various animal species in 1998. Identities of extra-integron genes encoding resistance to streptomycin, gentamicin, kanamycin, and apramycin were evaluated. Gentamicin resistance was seen in 37 (8.7%) isolates and was conferred by the aadB gene. Kanamycin resistance was seen in 122 (29%) isolates and was encoded by the aphA1-Iab gene (111 isolates; 26%) or by the Kn gene (11 isolates; 3%). Apramycin resistance was seen in 24 (5.7%) isolates and was determined by the aacC4 gene. Analysis of gene distribution did not reveal significant differences with regards to phagetype, host species, or region, except for the Kn gene, which was found mostly in nonclinical isolates. Streptomycin resistance was seen in all 422 isolates and was attributed to the aadA2 gene. This gene is integron-associated in phagetype DT104 and other phagetypes but was not found to be a part of the integron-associated pentaresistant gene cluster in phagetype DT208. The data from this study indicate that pentaresistant DT104 does not acquire extra-integron genes in species- or geographic-related foci, which supports clonal expansion as the method of spread of this organism.