AIM
This cross-sectional study characterized virulence factors, disinfectant resistance genes, and antimicrobial resistance determinants in multidrug-resistant Escherichia coli and Klebsiella pneumoniae from four urban wastewater treatment plants (WWTPs) in Windhoek, Namibia.
MATERIALS AND METHODS
Twenty-three isolates were identified using biochemical tests and MALDI-TOF, followed by antimicrobial susceptibility testing (AST) and whole-genome sequencing (WGS). Bioinformatic analyses assessed antimicrobial resistance genes (ARGs), virulence factors (VFs), disinfectant resistance genes (DRGs), sequence types, phylogenetic relationships, and co-occurrence with plasmid-associated sequences.
RESULTS
High phenotypic resistance was observed to ampicillin (70%) and amoxicillin and cefuroxime (≥50%). WGS identified clinically important lineages, including E. coli ST410 and K. pneumoniae ST70, ST20, and ST219. Isolates harbored extended-spectrum β-lactamase genes, notably blaCTX-M-15, plasmid-mediated quinolone resistance determinants, and virulence genes associated with iron acquisition (yersiniabactin), adhesion, and capsule biosynthesis. Disinfectant resistance genes, including qacE, were also detected, with several resistance and virulence determinants co-occurring with plasmid-associated sequences. Phylogenetic analysis revealed close genetic relatedness among isolates from treated effluent, indicating persistence of clinically relevant lineages within wastewater systems.
CONCLUSION
Wastewater-based genomic surveillance provides an effective approach for characterizing AMR, virulence, and disinfectant resistance, supporting genome-informed surveillance and wastewater management in water-scarce settings.
Smthokozele Sikabongo, Graça K. Kandanda, Uvatera Maurihungirire et al.· Future Microbiology· 0 citations
Wastewater treatment plants (WWTPs) are increasingly recognized as environmental reservoirs for antimicrobial resistance (AMR), yet genome-level data on non-clinical Gram-negative bacteria in wastewater remain scarce in many low- and middle-income settings. This study characterized the resistome, plasmid content, and genetic diversity of environmentally associated Gram-negative bacteria recovered from wastewater systems to elucidate their contribution to environmental AMR persistence. Influent and effluent samples (n = 30) were collected from three wastewater treatment plants. Sixteen Gram-negative isolates were recovered and identified using the VITEK system and matrix-assisted laser desorption/ionization time-of-flight mass spectrometry. Antimicrobial susceptibility testing was performed phenotypically, followed by whole-genome sequencing and bioinformatic analyses to identify antimicrobial resistance genes (ARGs), plasmid replicons, virulence-associated genes, and sequence types.The isolates comprised of
Enterobacter cloacae
(n = 5),
Raoultella planticola
(n = 3),
Raoultella ornithinolytica
(n = 3),
Citrobacter freundii
(n = 3), and
Aeromonas spp
. (n = 2). Multidrug resistance was observed phenotypically across influent and effluent samples. Genomic analysis identified clinically relevant ARGs, including
bla
ACT
,
bla
CTX-M-15
,
bla
CMY
,
qnr
variants,
fosA
,
aadA
,
sul1
, and
tet
genes, frequently associated with IncF, IncQ, IncL/M, and Col-type plasmids and virulent determinants including
yersiniabactin
and
enterobactin
. Resistance and plasmid profiles persisted in effluent-derived isolates, suggesting environmental persistence and potential transmission.This study provides genome-level baseline evidence that wastewater-associated, non-clinical Gram-negative bacteria in Namibia harbor clinically relevant AMR determinants, reinforcing the value of wastewater-based genomic surveillance for understanding environmental AMR dissemination, and emphasizing the public health implications of wastewater reuse.
Graça K. Kandanda, L. M. Mwapagha· PLOS Water· 0 citations
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