Affiliation:
1. Department of Animal Sciences
2. USDA Agricultural Research Service, Urbana, Illinois 61801
3. Department of Veterinary Pathobiology, University of Illinois at Urbana-Champaign
4. Illinois State Geological Survey, Champaign, Illinois 61820
Abstract
ABSTRACT
Phylogenetic analysis of tetracycline resistance genes, which confer resistance due to the efflux of tetracycline from the cell catalyzed by drug:H
+
antiport and share a common structure with 12 transmembrane segments (12-TMS), suggested the monophyletic origin of these genes. With a high degree of confidence, this
tet
subcluster unifies 11 genes encoding
tet
efflux pumps and includes
tet
(A),
tet
(B),
tet
(C),
tet
(D),
tet
(E),
tet
(G),
tet
(H),
tet
(J),
tet
(Y),
tet
(Z), and
tet
(30). Phylogeny-aided alignments were used to design a set of PCR primers for detection, retrieval, and sequence analysis of the corresponding gene fragments from a variety of bacterial and environmental sources. After rigorous validation with the characterized control
tet
templates, this primer set was used to determine the genotype of the corresponding tetracycline resistance genes in total DNA of swine feed and feces and in the lagoons and groundwater underlying two large swine production facilities known to be impacted by waste seepage. The compounded
tet
fingerprint of animal feed was found to be
tetCDEHZ
, while the corresponding fingerprint of total intestinal microbiota was
tetBCGHYZ
. Interestingly, the
tet
fingerprints in geographically distant waste lagoons were identical (
tetBCEHYZ
) and were similar to the fecal fingerprint at the third location mentioned above. Despite the sporadic detection of chlortetracycline in waste lagoons, no auxiliary diversity of
tet
genes in comparison with the fecal diversity could be detected, suggesting that the
tet
pool is generated mainly in the gut of tetracycline-fed animals, with a negligible contribution from selection imposed by tetracycline that is released into the environment. The
tet
efflux genes were found to be percolating into the underlying groundwater and could be detected as far as 250 m downstream from the lagoons. With yet another family of
tet
genes, this study confirmed our earlier findings that the antibiotic resistance gene pool generated in animal production systems may be mobile and persistent in the environment with the potential to enter the food chain.
Publisher
American Society for Microbiology
Subject
Ecology,Applied Microbiology and Biotechnology,Food Science,Biotechnology