Antibiotic resistance genes in the bacteriophage DNA fraction of environmental samples - PubMed (original) (raw)

Antibiotic resistance genes in the bacteriophage DNA fraction of environmental samples

Marta Colomer-Lluch et al. PLoS One. 2011.

Abstract

Antibiotic resistance is an increasing global problem resulting from the pressure of antibiotic usage, greater mobility of the population, and industrialization. Many antibiotic resistance genes are believed to have originated in microorganisms in the environment, and to have been transferred to other bacteria through mobile genetic elements. Among others, β-lactam antibiotics show clinical efficacy and low toxicity, and they are thus widely used as antimicrobials. Resistance to β-lactam antibiotics is conferred by β-lactamase genes and penicillin-binding proteins, which are chromosomal- or plasmid-encoded, although there is little information available on the contribution of other mobile genetic elements, such as phages. This study is focused on three genes that confer resistance to β-lactam antibiotics, namely two β-lactamase genes (blaTEM and blaCTX-M9) and one encoding a penicillin-binding protein (mecA) in bacteriophage DNA isolated from environmental water samples. The three genes were quantified in the DNA isolated from bacteriophages collected from 30 urban sewage and river water samples, using quantitative PCR amplification. All three genes were detected in the DNA of phages from all the samples tested, in some cases reaching 104 gene copies (GC) of blaTEM or 102 GC of blaCTX-M and mecA. These values are consistent with the amount of fecal pollution in the sample, except for mecA, which showed a higher number of copies in river water samples than in urban sewage. The bla genes from phage DNA were transferred by electroporation to sensitive host bacteria, which became resistant to ampicillin. blaTEM and blaCTX were detected in the DNA of the resistant clones after transfection. This study indicates that phages are reservoirs of resistance genes in the environment.

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Conflict of interest statement

Competing Interests: The authors have declared that no competing interests exist.

Figures

Figure 1

Figure 1. Electron micrographs of bacteriophages present in sewage and river water.

A–B. Group of phages with Myoviridae and Siphoviridae morphology from sewage. C. Myoviridae phages from river water. D: group of Siphoviridae phages from sewage. E–F. Myoviridae phages from sewage. G: Podoviridae phage from sewage. H–I. Siphoviridae phages from sewage and river water respectively. Bar 200 nm.

Figure 2

Figure 2. Number of copies of bla TEM genes (GC/ml) in urban sewage and river water samples in phage and bacterial DNA.

On the left side of the figure, bar chart of the gene copies detected for each sample, dark grey for phage DNA and light grey for bacterial DNA. On the right side of the figure, the box plot chart shows the averaged values obtained from all samples from the same origin. Within the box plot chart, the cross-pieces of each box plot represent (from top to bottom) maximum, upper-quartile, median (black bar), lower-quartile, and minimum values. Black diamond shows the mean value. The grey boxes in the box plot chart include samples showing values within the 75th percentile and white boxes samples showing values within the within the 25th percentile.

Figure 3

Figure 3. Primers and TaqMan assay probe resulting from the alignment of bla CTX-M genes from Cluster 1.

Conserved nucleotides are marked in bold, non-conserved nucleotides in white. Sequence reverse and complementary is shown for lower primer. Right column indicate the GenBank accession number of each gene.

Figure 4

Figure 4. Number of copies of bla CTX-M genes (GC/ml) in urban sewage and river water samples in phage and bacterial DNA and box plot of averaged values.

Figure 5

Figure 5. Number of copies of _mec_A (GC/ml) in urban sewage and river water samples in phage and bacterial DNA and box plot of averaged values.

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References

    1. World Health Organization. Geneva, Switzerland.: 1996. The world health report.
    1. American Academy of Microbiology. ASM. Washington; 2009. Antibiotic Resistance: An Ecological Perspective on an Old Problem.
    1. Hawkey PM, Jones AM. The changing epidemiology of resistance. J Antimicrob Chemother. 2009;64S1:i3–10. - PubMed
    1. Jansen WTM, Van Der Bruggen JT, Verhoef J, Fluit AC. Bacterial resistance: a sensitive issue. Complexity of the challenge and containment strategy in Europe. Drug Res Updates. 2006;9:123–133. - PMC - PubMed
    1. Canton R. Antibiotic resistance genes from the environment: a perspective through newly identified antibiotic resistance mechanisms in the clinical setting. Clin Microbiol Infect. 2009;1:20–25. - PubMed

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