PMC:3266646 / 30122-33541 JSONTXT

{"project":"2_test","denotations":[{"id":"22303296-15109783-36966614","span":{"begin":103,"end":107},"obj":"15109783"},{"id":"22303296-18565737-36966615","span":{"begin":129,"end":133},"obj":"18565737"},{"id":"22303296-20382816-36966616","span":{"begin":391,"end":395},"obj":"20382816"},{"id":"22303296-21390233-36966617","span":{"begin":658,"end":662},"obj":"21390233"},{"id":"22303296-21822974-36966618","span":{"begin":1216,"end":1220},"obj":"21822974"},{"id":"22303296-19074389-36966619","span":{"begin":1597,"end":1601},"obj":"19074389"},{"id":"22303296-20679504-36966620","span":{"begin":1874,"end":1878},"obj":"20679504"},{"id":"22303296-19719664-36966621","span":{"begin":2196,"end":2200},"obj":"19719664"},{"id":"22303296-19011075-36966622","span":{"begin":2268,"end":2272},"obj":"19011075"},{"id":"22303296-18845826-36966623","span":{"begin":2368,"end":2372},"obj":"18845826"},{"id":"22303296-15109783-36966624","span":{"begin":3105,"end":3109},"obj":"15109783"},{"id":"22303296-18565737-36966625","span":{"begin":3131,"end":3135},"obj":"18565737"}],"text":"Phages\nPhages are major constituents of environmental ecosystems, in particular freshwater (Weinbauer, 2004; Srinivasiah et al., 2008). Their abundance is usually higher than bacterial abundance and, since a significant fraction of the prokaryotic community is infected with phages in aquatic systems, phages are likely to play an important role in horizontal gene transfer. Parsley et al. (2010) have proven the presence of β-lactamases genes in the viral metagenome of an activated sludge, confirming that transduction events may be responsible for the propagation of antibiotic resistance genes in these environments. Interestingly, Colomer-Lluch et al. (2011) demonstrated the presence of blaTEM and blaCTX-M, the most common genes conferring β-lactams resistance in Enterobacteriaceae, and mecA, responsible for methicillin resistance in Staphylococcus aureus, in phage DNA isolated from a waste water treatment plant and the natural water of the receiving river.\nThe presence of mecA in the phage fraction of natural freshwater is of great sanitary concern because of the threat represented by methicillin resistant Staphylococcus aureus (MRSA) infections, both in hospitals and communities (Campanile et al., 2011). This finding is also of interest for the understanding of the propagation of this gene. mecA codes for a protein with a low affinity to penicillin (PBP2a), conferring methicillin resistance. This gene is located on a mobile genomic element, the staphylococcal cassette chromosome (SCCmec), and has been reported only from the Staphylococcus genus from clinics. Baba et al. (2009) have characterized a methicillin resistance gene complex, mecIRAm, which could be the progenitor of SCCmec observed in clinical MRSA, from a strain of Macrococcus caseolyticus (closely related to S. aureus), isolated from animal meat. Interestingly, Tsubakishita et al. (2010) found a mecA gene in S. fleurettii chromosomally located and not associated to the SCCmec element. Thus, the authors advanced the hypothesis that S. fleurettii, an animal related species, is the progenitor of this resistance mechanism. The mecA gene has been reported rarely from natural water, but Schwartz et al. (2003) detected mecA in hospital waste waters. Later, Bockelmann et al. (2009) have reported the sporadic presence of mecA in a ground water recharge system. Kassem et al. (2008) described the presence of the mecA gene in 18 Proteus vulgaris, four M. morganii, and three Enterococcus faecalis isolated from surface water. A ca. 250 bp-sequence of mecA from one representative isolate of P. vulgaris, M. morganii, and E. faecalis was found to exhibit 100% similarity with the S. aureus mecA gene. However, this result, which is the first report of MecA in non-staphylococcal organisms, has never been confirmed by other studies or investigated further. Acquisition by transduction of heterologous genes, particularly of antibiotic resistance genes, might represent an important mechanism of horizontal gene transfer in water bodies. Considering the high concentration of phages in such environments (Weinbauer, 2004; Srinivasiah et al., 2008), transduction constitutes probably one of the main gene transfer mechanisms and of genome evolution for bacteria in water habitats. More studies are needed to understand the impact of phage communities on bacterial evolution and antibiotic resistance spread within the water bodies."}