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It’s the Phestival of Phage 2011 on MicrobiologyBytes :-)
Recognized as a global problem, antibiotic resistance increases the morbidity and mortality caused by bacterial infections, as well as the cost of treating infectious diseases. The threat from resistance (particularly multiple resistance in bacterial strains that are widely disseminated) is serious. The key factors contributing to this threat are the pressure of increased antibiotic usage (in both human and animal medicine), greater mobility of the population and industrialization. Many potentially life-threatening infections, generally regarded as diseases from the past due to the success of antibiotics and vaccines, have returned as resistance increasingly hampers successful therapy and prophylaxis.
Several studies have focused on antibiotic resistance codification in plasmids or transposons, and there is also interesting information about the extent of antibiotic resistance genes in a given environment (the so-called “resistome”). However, there is less information on the potential contribution of phages to antibiotic resistance-gene transfer, despite calls for research in this field. Recent reports conclude that the horizontal transfer of genetic information by phages is much more prevalent than previously thought, and that the environment plays a crucial role in the phage-mediated transfer of antibiotic-resistance genes. This paper highlights the potential role of phages in the spread of these genes in the aquatic environment.
Antibiotic Resistance Genes in the Bacteriophage DNA Fraction of Environmental Samples. (2011) PLoS ONE 6(3): e17549. doi:10.1371/journal.pone.0017549
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.