Infrequent finding of metallo-ß-lactamase VIM-2 in carbapenem-resistant Pseudomonas aeruginosa strains from Croatia.

One hundred sixty-nine nonreplicate imipenem-resistant Pseudomonas aeruginosa strains isolated in a large hospital on the coastal region of Croatia were studied. The most active antibiotics were colistin and amikacin. Most of the isolates were multiresistant. The most prevalent serotype was O12, followed by O11. Six strains carried the bla(VIM-2) gene located in a novel class 1 integron composed in its variable part of the bla(VIM-2)-bla(oxa-10)-ΔqacF-aacA4 genes. Metallo-ß-lactamase-producing strains belonged to sequence types ST235 and ST111.

Radioecological risk assessment of low selenium concentrations through genetic fingerprints and metabolic profiling of soil bacterial communities.

In a context of environmental risk assessment of nuclear (79)Se radionuclide, the impact of low Se-selenite concentrations (0.008 and 8 mg kg(-1)) on bacterial communities of two soils, a silty clay loam and a sandy soil, was investigated over a 6-month incubation time. This Se-selenite was partially labelled with (75)Se. The state of the Se-impacted bacterial communities was analyzed through total bacterial counts, DNA fingerprints (ARISA profiles) and metabolic profiling (carbon substrate utilization patterns). Furthermore, the genetic diversity of bacterial populations involved in Se volatilization was evaluated by tpm (thiopurine methyltransferase gene) profiling. Emissions of (75)Se and CaCl(2)-extractable (75)Se were measured by γ-spectrometry and scintillation analysis. Se-selenite inputs changed transiently the substrate utilization patterns of bacterial communities but did not affect the other indicators. Se volatilization was at its highest level just after adding Se-selenite and for about 1 week. This volatilization was proportional to the added Se-selenite concentrations. It was 100-fold higher in silty clay loam, even though Se bioavailability was reduced in this soil. The soils were amended with crushed grass 3 months after the addition of Se-selenite. This organic amendment affected the organization of bacterial communities and increased the Se-volatilizing activities of both soils. Original soil organic carbon and bacterial diversity and activities seemed responsible for the different levels of Se emissions observed in soils. tpm lineages, encoding Se methyltransferases, were detected in both soils, confirming the broad distribution of tpm-harbouring bacteria and their probable role in the emissions of volatile Se. Five distinct groups of tpm were recorded per soil, with tpmI lineage being detected throughout the incubation period. This study demonstrates the ability of bacterial communities at volatilizing Se concentrations inferior to geochemical backgrounds and suggests that a probable transfer of nuclear Se will occur through volatilization after an environmental spill.

Lagooning of wastewaters favors dissemination of clinically relevant Pseudomonas aeruginosa.

The significance of wastewater treatment lagoons (WWTLs) as point sources of clinically relevant Pseudomonas aeruginosa that can disseminate through rural and peri-urban catchments was investigated. A panel of P. aeruginosa strains collected over three years from WWTLs and community-acquired infections was compared by pulsed field gel electrophoresis (PFGE) DNA fingerprinting and multilocus sequence typing (MLST). Forty-four distantly related PFGE profiles and four clonal complexes were found among the WWTL strains analyzed. Some genotypes were repeatedly detected from different parts of WWTLs, including the influent, suggesting an ability to migrate and persist over time. MLST showed all investigated lineages to match sequence types described in other countries and strains from major clinical clones such as PA14 of ST253 and "C" of ST17 were observed. Some of these genotypes matched isolates from community-acquired infections recorded in the WWTL geographic area. Most WWTL strains harbored the main P. aeruginosa virulence genes; 13% harbored exoU-encoded cytoxins, but on at least six different genomic islands, with some of these showing signs of genomic instability. P. aeruginosa appeared to be highly successful opportunistic colonizers of WWTLs. Lagooning of wastewaters was found to favor dissemination of clinically relevant P. aeruginosa among peri-urban watersheds.