Global spread of mobile antimicrobial drug resistance determinants in human and animal Escherichia coli and Salmonella strains causing community-acquired infections.
BACKGROUND
Antimicrobial drugs used in human infection treatment and animal husbandry may select for drug-resistant bacterial pathogens, which are increasingly observed worldwide. We sought to examine the extent to which identical mobile drug resistance elements are shared across common pathogens isolated from human and animal sources.


METHODS
We compared the distribution of one class of mobile elements--integrons and gene cassettes--among uropathogenic Escherichia coli isolates, Salmonella enterica serovar Typhimurium isolates from human diarrhea cases, and E. coli and Salmonella isolates from nonhuman sources in the United States. The sequences of the gene cassettes were also compared with those deposited in GenBank.


RESULTS
Class 1 integrons were detected in 68 (49%) of 139 uropathogenic E. coli isolates, 16 (72%) of 22 human and animal Salmonella isolates, and 120 (28%) of 436 nonhuman E. coli isolates. The most prevalent cassettes were those encoding aminoglycoside adenyltransferase A (aadA) and dihydrofolate reductase A (dfrA). Sequences of aadA1, dfrA12-orfF-aadA2, and dfrA17-aadA5 gene cassettes from 35 urinary tract infection E. coli isolates and of aadA2 and aadA12 gene cassettes from 7 Salmonella isolates were 100% identical to the corresponding cassette sequences from food animal E. coli isolates and those deposited in GenBank from a wide variety of bacteria isolated from animal hosts from distinct regions of the world.


CONCLUSIONS
Common community-acquired human drug-resistant infections are caused by bacterial strains that harbor mobile drug resistance determinants of identical sequences that are found in diverse bacterial species from varied animal sources worldwide.
Ajiboye
Remi M
RM
School of Public Health, School of Public Health, University of California, Berkeley, CA 94720, USA.
Solberg
Owen D
OD
Lee
Bryan M
BM
Raphael
Eva
E
Debroy
Chitrita
C
Riley
Lee W
LW
D000818:Animals; D000900:Anti-Bacterial Agents / Q000494:pharmacology; D002417:Cattle; D002645:Chickens; D017714:Community-Acquired Infections / Q000382:microbiology*; D004269:DNA, Bacterial / Q000737:chemistry / Q000235:genetics; D024881:Drug Resistance, Bacterial; D004926:Escherichia coli / Q000187:drug effects* / Q000235:genetics / Q000302:isolation & purification; D004927:Escherichia coli Infections / Q000382:microbiology / Q000662:veterinary*; D005260:Female; D006801:Humans; D020071:Interspersed Repetitive Sequences; D008969:Molecular Sequence Data; D012480:Salmonella Infections / Q000382:microbiology*; D012481:Salmonella Infections, Animal / Q000382:microbiology*; D012486:Salmonella typhimurium / Q000187:drug effects* / Q000235:genetics / Q000302:isolation & purification; D017422:Sequence Analysis, DNA; D013552:Swine; D014422:Turkeys; D014481:United States
D000900:Anti-Bacterial Agents; D004269:DNA, Bacterial