title: High Diversity of CTX-M Extended-Spectrum β-Lactamases in Municipal Wastewater and Urban Wetlands.
abstract: The CTX-M-type extended-spectrum β-lactamases (ESBLs) present a serious public health threat as they have become nearly ubiquitous among clinical gram-negative pathogens, particularly the enterobacteria. To aid in the understanding and eventual control of the spread of such resistance genes, we sought to determine the diversity of CTX-M ESBLs not among clinical isolates, but in the environment, where weaker and more diverse selective pressures may allow greater enzyme diversification. This was done by examining the CTX-M diversity in municipal wastewater and urban coastal wetlands in southern California, United States, by Sanger sequencing of polymerase chain reaction amplicons. Of the five known CTX-M phylogroups (1, 2, 8, 9, and 25), only genes from groups 1 and 2 were detected in both wastewater treatment plants (WWTPs), and group 1 genes were also detected in one of the two wetlands after a winter rain. The highest relative abundance of blaCTX-M group 1 genes was in the sludge of one WWTP (2.1 × 10(-4) blaCTX-M copies/16S rRNA gene copy). Gene libraries revealed surprisingly high nucleotide sequence diversity, with 157 new variants not found in GenBank, representing 99 novel amino acid sequences. Our results indicate that the resistomes of WWTPs and urban wetlands contain diverse blaCTX-M ESBLs, which may constitute a mobile reservoir of clinically relevant resistance genes.
authors.affiliation: 1 Department of Biology, Point Loma Nazarene University , San Diego, California.
authors.forename: Timothy R
authors.initials: TR
authors.lastname: Borgogna
authors.affiliation: 1 Department of Biology, Point Loma Nazarene University , San Diego, California.
authors.forename: Joanna-Lynn
authors.initials: JL
authors.lastname: Borgogna
authors.affiliation: 1 Department of Biology, Point Loma Nazarene University , San Diego, California.
authors.forename: Jenna A
authors.initials: JA
authors.lastname: Mielke
authors.affiliation: 2 Department of Biological Sciences, Institute for Bioinformatics and Evolutionary Studies (IBEST), University of Idaho , Moscow, Idaho.
authors.forename: Celeste J
authors.initials: CJ
authors.lastname: Brown
authors.affiliation: 2 Department of Biological Sciences, Institute for Bioinformatics and Evolutionary Studies (IBEST), University of Idaho , Moscow, Idaho.
authors.forename: Eva M
authors.initials: EM
authors.lastname: Top
authors.affiliation: 3 Department of Mathematics, Information, and Computer Sciences, Point Loma Nazarene University , San Diego, California.
authors.forename: Ryan T
authors.initials: RT
authors.lastname: Botts
authors.affiliation: 1 Department of Biology, Point Loma Nazarene University , San Diego, California.
authors.forename: David E
authors.initials: DE
authors.lastname: Cummings
mesh_terms: D000900:Anti-Bacterial Agents / Q000494:pharmacology; D015373:Bacterial Typing Techniques; D002140:California; D002947:Cities; D004926:Escherichia coli / Q000145:classification / Q000187:drug effects / Q000235:genetics* / Q000302:isolation & purification; D029968:Escherichia coli Proteins / Q000145:classification / Q000235:genetics*; D015870:Gene Expression; D014644:Genetic Variation; D005838:Genotype; D006801:Humans; D007711:Klebsiella pneumoniae / Q000145:classification / Q000187:drug effects / Q000235:genetics* / Q000302:isolation & purification; D010802:Phylogeny; D010957:Plasmids / Q000737:chemistry / Q000378:metabolism; D017422:Sequence Analysis, DNA; D062065:Wastewater / Q000382:microbiology; D014871:Water Microbiology; D053833:Wetlands; D018440:beta-Lactam Resistance / Q000235:genetics*; D001618:beta-Lactamases / Q000145:classification / Q000235:genetics*; D047090:beta-Lactams / Q000494:pharmacology
chemical_list: D000900:Anti-Bacterial Agents; D029968:Escherichia coli Proteins; D062065:Wastewater; D001618:beta-Lactamases; D047090:beta-Lactams; C000602253:beta-lactamase CTX-M, E coli