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Potential impacts of aquatic pollutants: sub-clinical antibiotic concentrations induce genome changes and promote antibiotic resistance.

Chow L, Waldron L, Gillings MR - Front Microbiol (2015)

Bottom Line: These changes were observed in as few as five passages, despite the fact that the protocols used sample less than 0.3% of the genome, in turn suggesting much more widespread alterations to sequence and genome architecture.Experimental lines also displayed variant colony morphologies.The final MICs were significantly higher in some experimental lineages of P. protegens, suggesting that 1/10 the MIC induces de-novo mutation events that generate resistance phenotypes.

View Article: PubMed Central - PubMed

Affiliation: Emma Veritas Laboratory, Department of Biological Sciences, Macquarie University Sydney, NSW, Australia.

ABSTRACT
Antibiotics are disseminated into aquatic environments via human waste streams and agricultural run-off. Here they can persist at low, but biologically relevant, concentrations. Antibiotic pollution establishes a selection gradient for resistance and may also raise the frequency of events that generate resistance: point mutations; recombination; and lateral gene transfer. This study examined the response of bacteria to sub-inhibitory levels of antibiotics. Pseudomonas aeruginosa and Pseudomonas protegens were exposed kanamycin, tetracycline or ciprofloxacin at 1/10 the minimal inhibitory concentration (MIC) in a serial streaking experiment over 40 passages. Significant changes in rep-PCR fingerprints were noted in both species when exposed to sub-inhibitory antibiotic concentrations. These changes were observed in as few as five passages, despite the fact that the protocols used sample less than 0.3% of the genome, in turn suggesting much more widespread alterations to sequence and genome architecture. Experimental lines also displayed variant colony morphologies. The final MICs were significantly higher in some experimental lineages of P. protegens, suggesting that 1/10 the MIC induces de-novo mutation events that generate resistance phenotypes. The implications of these results are clear: exposure of the environmental microbiome to antibiotic pollution will induce similar changes, including generating newly resistant species that may be of significant concern for human health.

No MeSH data available.


Related in: MedlinePlus

Representative graphs displaying the MIC of selected antibiotics for the experimental and control lines. MIC tests for Ps. protegens strains are shown for PF5/ciprofloxacin (A), PF5/kanamycin (B), and PF5A/kanamycin (C). For more examples see Supplementary Material (Figures S7–S9).
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Figure 4: Representative graphs displaying the MIC of selected antibiotics for the experimental and control lines. MIC tests for Ps. protegens strains are shown for PF5/ciprofloxacin (A), PF5/kanamycin (B), and PF5A/kanamycin (C). For more examples see Supplementary Material (Figures S7–S9).

Mentions: The MIC of each line was determined at passage 40 in order to detect any significant differences in MICs from the control line and from the starting MIC. There were no significant differences in the MIC of P. aeruginosa PA14 for any of the treatment lines. In contrast, there were some significant differences in the MIC of P. protegens PF-5 and P. protegens PF-5A. A representative sample of MIC graphs are displayed in Figure 4. Figure 4A shows the MIC for ciprofloxacin for all control and experimental lines of P. protegens PF5. One line of P. protegens PF5 that had been exposed to 1/10 the MIC of ciprofloxacin over the serial plating experiment exhibited a 10-fold increase in MIC for ciprofloxacin (DF = 11, F = 11.94, P < 0.0001). A similar phenomenon was seen in P. protegens PF5 (Figure 4B) and P. protegens PF5A (Figure 4C) when tested on kanamycin. All six lines that had been exposed to kanamycin over the serial plating experiment had four to eight fold increases in their MIC for kanamycin (DF = 11, F = 1.96, P > 0.05 and DF = 11, F = 46.04, P < 0.0001 respectively). Similar tests conducted on a subset of the kanamycin treated lines at passage 20 did not detect any elevation in MIC.


Potential impacts of aquatic pollutants: sub-clinical antibiotic concentrations induce genome changes and promote antibiotic resistance.

Chow L, Waldron L, Gillings MR - Front Microbiol (2015)

Representative graphs displaying the MIC of selected antibiotics for the experimental and control lines. MIC tests for Ps. protegens strains are shown for PF5/ciprofloxacin (A), PF5/kanamycin (B), and PF5A/kanamycin (C). For more examples see Supplementary Material (Figures S7–S9).
© Copyright Policy
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC4525061&req=5

Figure 4: Representative graphs displaying the MIC of selected antibiotics for the experimental and control lines. MIC tests for Ps. protegens strains are shown for PF5/ciprofloxacin (A), PF5/kanamycin (B), and PF5A/kanamycin (C). For more examples see Supplementary Material (Figures S7–S9).
Mentions: The MIC of each line was determined at passage 40 in order to detect any significant differences in MICs from the control line and from the starting MIC. There were no significant differences in the MIC of P. aeruginosa PA14 for any of the treatment lines. In contrast, there were some significant differences in the MIC of P. protegens PF-5 and P. protegens PF-5A. A representative sample of MIC graphs are displayed in Figure 4. Figure 4A shows the MIC for ciprofloxacin for all control and experimental lines of P. protegens PF5. One line of P. protegens PF5 that had been exposed to 1/10 the MIC of ciprofloxacin over the serial plating experiment exhibited a 10-fold increase in MIC for ciprofloxacin (DF = 11, F = 11.94, P < 0.0001). A similar phenomenon was seen in P. protegens PF5 (Figure 4B) and P. protegens PF5A (Figure 4C) when tested on kanamycin. All six lines that had been exposed to kanamycin over the serial plating experiment had four to eight fold increases in their MIC for kanamycin (DF = 11, F = 1.96, P > 0.05 and DF = 11, F = 46.04, P < 0.0001 respectively). Similar tests conducted on a subset of the kanamycin treated lines at passage 20 did not detect any elevation in MIC.

Bottom Line: These changes were observed in as few as five passages, despite the fact that the protocols used sample less than 0.3% of the genome, in turn suggesting much more widespread alterations to sequence and genome architecture.Experimental lines also displayed variant colony morphologies.The final MICs were significantly higher in some experimental lineages of P. protegens, suggesting that 1/10 the MIC induces de-novo mutation events that generate resistance phenotypes.

View Article: PubMed Central - PubMed

Affiliation: Emma Veritas Laboratory, Department of Biological Sciences, Macquarie University Sydney, NSW, Australia.

ABSTRACT
Antibiotics are disseminated into aquatic environments via human waste streams and agricultural run-off. Here they can persist at low, but biologically relevant, concentrations. Antibiotic pollution establishes a selection gradient for resistance and may also raise the frequency of events that generate resistance: point mutations; recombination; and lateral gene transfer. This study examined the response of bacteria to sub-inhibitory levels of antibiotics. Pseudomonas aeruginosa and Pseudomonas protegens were exposed kanamycin, tetracycline or ciprofloxacin at 1/10 the minimal inhibitory concentration (MIC) in a serial streaking experiment over 40 passages. Significant changes in rep-PCR fingerprints were noted in both species when exposed to sub-inhibitory antibiotic concentrations. These changes were observed in as few as five passages, despite the fact that the protocols used sample less than 0.3% of the genome, in turn suggesting much more widespread alterations to sequence and genome architecture. Experimental lines also displayed variant colony morphologies. The final MICs were significantly higher in some experimental lineages of P. protegens, suggesting that 1/10 the MIC induces de-novo mutation events that generate resistance phenotypes. The implications of these results are clear: exposure of the environmental microbiome to antibiotic pollution will induce similar changes, including generating newly resistant species that may be of significant concern for human health.

No MeSH data available.


Related in: MedlinePlus