Identification of new bacteria harboring qnrS and aac(6′)-Ib/cr and mutations possibly involved in fluoroquinolone resistance in raw sewage and activated sludge samples from a full-scale WWTP

Wastewater treatment plants (WWTPs) harbor bacteria and antimicrobial resistance genes, favoring gene exchange events and resistance dissemination. Here, a culture-based and metagenomic survey of qnrA, qnrB, qnrS, and aac(6′)-Ib genes from raw sewage (RS) and activated sludge (AS) of a full-scale mu...

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Bibliographic Details
Published in:Water research (Oxford) 2017-03, Vol.110, p.27-37
Main Authors: Paiva, Magna C., Reis, Mariana P., Costa, Patrícia S., Dias, Marcela F., Bleicher, Lucas, Scholte, Larissa L.S., Nardi, Regina M.D., Nascimento, Andréa M.A.
Format: Article
Language:English
Subjects:
aac(6′)Ib
aac(6′)Ib-cr
Activated sludge
Anti-Bacterial Agents - pharmacology
Bacteria
Drug Resistance, Bacterial - genetics
Escherichia coli - isolation & purification
Fluoroquinolones
Microbial Sensitivity Tests
Mutation
Plasmids - drug effects
qnrS
Quinolone
Quinolones
Raw sewage
Sewage
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Summary:Wastewater treatment plants (WWTPs) harbor bacteria and antimicrobial resistance genes, favoring gene exchange events and resistance dissemination. Here, a culture-based and metagenomic survey of qnrA, qnrB, qnrS, and aac(6′)-Ib genes from raw sewage (RS) and activated sludge (AS) of a full-scale municipal WWTP was performed. A total of 96 bacterial isolates were recovered from nalidixic acid-enrichment cultures. Bacteria harboring the aac(6′)-Ib gene predominated in RS, whereas qnrS-positive isolates were specific to AS. Novel qnrS- and aac(6′)-Ib-cr positive species were identified: Morganella morganii, Providencia rettgeri, and Pseudomonas guangdongensis (qnrS), and Alcaligenes faecalis and P. rettgeri (aac(6′)-Ib-cr). Analysis of qnrS and aac(6′)-Ib sequences from isolates and clone libraries suggested that the diversity of qnrS is wider than that of aac(6′)-Ib. A large number of amino acid mutations were observed in the QnrS and AAC(6′)-Ib proteins at previously undetected positions, whose structural implications are not clear. An accumulation of mutations at the C72, Q73, L74, A75 and M76 positions of QnrS, and D181 of AAC(6′)-Ib might be important for resistance. These findings add significant information on bacteria harboring qnrS and aac(6′)-Ib genes, and the presence of novel mutations that may eventually emerge in clinical isolates. •Bacteria harboring the aac(6′)-Ib gene predominated in raw sewage.•qnrS-positive bacteria were specific to activated sludge.•First report of the qnrS gene in Providencia rettgeri and Pseudomonas guangdongensis.•aac(6′)-Ib-cr: first report in Alcaligenes faecalis and Providencia rettgeri.•QnrS and AAC(6′)Ib exhibited many amino acids alterations previously undetected.
ISSN:0043-1354
1879-2448
DOI:10.1016/j.watres.2016.11.056