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. 2025 Jun 4:16:1586811.
doi: 10.3389/fmicb.2025.1586811. eCollection 2025.

Uncovering antibiotic resistance: extended-spectrum beta-lactamase-producing Pseudomonas aeruginosa from dipteran flies in residential dumping and livestock environments

Lara de Wet  1 , Itumeleng Matle  2 , Oriel Thekisoe  1 , Kgaugelo E Lekota  1 , Tsepo Ramatla  3
Affiliations

Uncovering antibiotic resistance: extended-spectrum beta-lactamase-producing Pseudomonas aeruginosa from dipteran flies in residential dumping and livestock environments

Lara de Wet et al. Front Microbiol. .

Abstract

Introduction: Pseudomonas aeruginosa poses challenges in clinical and environmental contexts due to its capacity to colonize natural ecosystems and antibiotic resistance. This study characterized P. aeruginosa harboured by Diptera flies collected from illegal residential dumping sites and livestock (cattle, sheep, and goats) kraals in Potchefstroom, South Africa.

Methods: The P. aeruginosa isolates were characterized using classical microbiological tests and species-specific gyrase B gene PCR assay. Antibiotic resistance (AR) was assessed on the isolates using disc diffusion assay (DDA). Additionally, PCR screened six virulence genes (exoS, plcN, plcH, toxA, lasB, and algD) among the isolates. Whole genome sequencing (WGS) was employed to confirm the identity and determine antibiotic resistance genes (ARGs) on selected isolates.

Results: Culture-based and molecular assays showed that P. aeruginosa is prevalent in Diptera flies (Hemipyrellia spp., Synthesiomya spp., Chrysomya spp., Sarchophagidae spp., and Tabanus spp.) from livestock kraals (75%; n = 36/48) and dumping sites (48%; n = 23/48). The most detected virulent gene among the isolates was exoS (96.6%), followed by plcN and algD genes (83.1%), lasB (81.4%), toxA (76.3%), and plcH (47.5%). All P. aeruginosa isolates were resistant to metronidazole, sulphamethoxazole, cefazolin and amoxicillin based on DDA. The sulfonamide resistance sulI gene (88.1%) was the most detected ARG from the P. aeruginosa isolates, followed by acc(3)-IV (80.6%) coding for aminoglycoside. WGS revealed that P. aeruginosa isolates belong to the sequence type (ST3808), which is multidrug-resistant and contains ARGs for fosfomycin (fosA), ampicillin (bla OXA-50), chloramphenicol (catB7), beta-lactamase (bla PAO), and aminoglycoside (aph(3')-IIb).

Discussion: This study isolated ESBL-producing P. aeruginosa from various Diptera fly species collected from livestock kraals and residential dumping sites. This bacterium is important to "One Health" due to its multidrug resistance character and zoonotic nature. As a result, it requires consolidated control and management policies from the environmental, veterinary, and human health sectors.

Keywords: Diptera flies; Pseudomonas aeruginosa; WGS; antibiotic resistance; virulence genes.

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Conflict of interest statement

The authors declare that the research was conducted in the absence of any commercial or financial relationships that could be construed as a potential conflict of interest.

Figures

Figure 1
Figure 1
Map of the North West province in South Africa indicating Ikageng residential dumping site and Matlwang community area.
Figure 2
Figure 2
Phylogenetic clustering of the virulence genes that are present or absence in P. aeruginosa isolates in relation to fly-genera collected from (A) residential dumping site and (B) livestock kraals.
Figure 3
Figure 3
Heatmap analysis of the antibiotic susceptibility using the Kirby-Bauer method for P. aeruginosa isolates from flies collected at (A) residential dumping site and (B) livestock kraals.
Figure 4
Figure 4
Whole genome-based phylogenetic tree using single nucleotide polymorphism inferring the evolutionary relationships among the sequenced Pseudomonas aeruginosa strains with antibiotic-resistant and virulence determinates. (A) Genome Blast Distance Phylogenies (GBDP) identified by TYGS between the sequenced P. aeruginosa strains (indicated by user strain) and related genomes. (B) Virulence genes and (C) antibiotic resistance genes that are shared among the sequenced strain and reference strain PAO1.
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