Heavy metal resistance genes and plasmid-mediated quinolone resistance genes in Arthrobacter sp. isolated from Brazilian soils.

Arthrobacter sp. are Gram-positive bacilli commonly obtained from soil and in the hospital environment. These species have been reported to cause several types of infection. Heavy metals are a threat to the ecological system due to their high-levels of toxicity and the fluoroquinolones are antimicrobials widely used for the treatment of different bacterial infections. The aim of this study was to investigate the resistance to fluoroquinolone and heavy metals, the presence of plasmid-mediated resistance (PMQR) genes and heavy metals resistance (HMR) genes and the presence of plasmids in Arthrobacter sp. obtained from Brazilian soils. Bacterial isolation was performed using soil samples from different Brazilian regions. The bacterial identification was performed by 16S rRNA gene sequencing. The resistance profile for fluoroquinolones and heavy metals was determined by MIC. Several PMQR and HMR genes and plasmid families were investigated by PCR. Eight isolates were obtained from soil samples from different cultivations and regions of Brazil. All isolates were resistant to all fluoroquinolones, cadmium, cobalt and zinc and the majority to copper. Among the PMQR genes, the qepA (4) was the most prevalent, followed by qnrS (3), qnrB (3), oqxB (2) and oqxA (1). Among the HMR genes, the copA was detected in all isolates and the czcA in two isolates. The replication origin of the ColE-like plasmid was detected in all isolates; however, no plasmid was detected by extraction. The association of resistance to heavy metals and antimicrobials is a threat to the environmental balance and to human health. There are no studies reporting the association of PMQR and HMR genes in bacteria belonging to the genus Arthrobacter. To the best of our knowledge, this is the first report of qnrB, qepA, oqxA and oqxB in Arthrobacter species.

Characterization of Acquired Antimicrobial Resistance Genes in Environmental Stenotrophomonas maltophilia Isolates from Brazil.

Stenotrophomonas maltophilia is an opportunist pathogen that has intrinsic resistance to the majority of antibiotics and has a high ability to adapt in different environments; however, there are few reports of acquired resistance genes in S. maltophilia. The aim of this study was to investigate the antimicrobial resistance profile, the presence of mutations in the quinolone-resistance determining region, the presence of acquired resistance genes, and the different plasmid families in S. maltophilia isolated from Brazilian soils. A total of 16 isolates were obtained from a variety of agricultural soils with different cultures of Brazil and they were nonsusceptible to most of the antibiotics tested. No mutations were detected in the gyrA gene and only one (Ser-80-Ile) was detected in the parC gene. A diversity of acquired resistance genes was found, including the qnrA, qnrB, qnrS, oqxA, oqxB, blaSHV, blaCTX-M-Gp1, blaPER, blaOXA-1-like, blaOXA-48-like, and sul1. All isolates presented ColE-like plasmids and only one presented IncL/M. These results show, for the first time, the presence of qnrA and oqxAB genes and the presence of qnrB and qnrS genes for the second time in the world in S. maltophilia.

Replicon typing of plasmids in environmental Achromobacter sp. producing quinolone-resistant determinants.

This study aimed to investigate the antimicrobial resistance profile to quinolones, the presence of quinolone-resistant determinants and the plasmid replicon typing in environmental Achromobacter sp. isolated from Brazil. Soil and water samples were used for bacterial isolation. The antimicrobial susceptibility testing was performed by minimum inhibitory concentration method. The detection of mutations in the quinolone resistance-determining regions (QRDR) genes, the presence of plasmid-mediated quinolone resistance (PMQR) genes, and plasmid replicons were performed by PCR. A total of 16 isolates was obtained from different cultures, cities, and states of Brazil. All isolates were non-susceptible to ciprofloxacin, norfloxacin, and levofloxacin. Some mutations in QRDR genes were found, including Gln-83-Leu and Asp-87-Asn in the gyrA and Gln-80-Ile and Asp-84-Ala in the parC. Different PMQR genes were detected, such as qnrA, qnrB, qnrS, oqxA, and oqxB. Three different plasmid families were detected, being most presented the ColE-like, followed by IncFIB and IncA/C. The presence of different PMQR genes and plasmids in the isolates of the present study shows that environmental bacteria can act as reservoir of important genes of resistance to fluoroquinolones, which is of great concern, due to the potential of horizontal dissemination of these genes. Besides that, there are no studies reporting these results in Achromobacter sp. isolates.

Detection of different ß-lactamases encoding genes, including blaNDM, and plasmid-mediated quinolone resistance genes in different water sources from Brazil.

Bacterial resistance occurs by spontaneous mutations or horizontal gene transfer mediated by mobile genetic elements, which represents a great concern. Resistance to ß-lactam antibiotics is mainly due to the production of ß-lactamases, and an important mechanism of fluoroquinolone resistance is the acquisition plasmid determinants. The aim of this study was to verify the presence of ß-lactamase-encoding genes and plasmid-mediated quinolone resistance genes in different water samples obtained from São Paulo state, Brazil. A high level of these resistance genes was detected, being the blaSHV, blaGES, and qnr the most prevalent. Besides that, the blaNDM gene, which codify an important and hazardous metallo-ß-lactamase, was detected.

Presence of ß-Lactamase Encoding Genes in Burkholderia cepacia Complex Isolated from Soil.

Burkholderia cepacia complex has emerged as an important opportunistic bacteria group for immunocompromised patients, and it has a high level of intrinsic resistance for different antibiotic classes. Hydrolysis of ß-lactam antibiotics by ß-lactamases is the most common resistance mechanism in Gram-negative bacteria, and the presence of such enzymes complicates the selection of appropriate therapy. This study aimed at investigating the antimicrobial resistance profile and the presence of ß-lactamase encoding genes in B. cepacia complex isolated from Brazilian soils. High-level ceftazidime resistance and several ß-lactamase encoding genes were found, including the first report of blaKPC genes in bacteria isolated from soil.

The Drosophila melanogaster Eip74EF-PA transcription factor directly binds the sciarid BhC4-1 promoter.

The DNA puff BhC4-1 gene of Bradysia hygida (Diptera, Sciaridae) is amplified and expressed in the salivary glands at the end of the last larval instar. Even though there are no BhC4-1 orthologs in Drosophila melanogaster, the mechanisms that regulate BhC4-1 gene expression in B. hygida are for the most part conserved in D. melanogaster. The BhC4-1 promoter contains a 129bp (-186/-58) cis-regulatory module (CRM) that drives developmentally regulated expression in transgenic salivary glands at the onset of metamorphosis. Both in the sciarid and in transgenic D. melanogaster, BhC4-1 gene expression is induced by the increase in ecdysone titers that triggers metamorphosis. Genetic interaction experiments revealed that in the absence of the Eip74EF-PA early gene isoform BhC4-1-lacZ levels of expression in the salivary gland are severely reduced. Here we show that the overexpression of the Eip74EF-PA transcription factor is sufficient to anticipate BhC4-1-lacZ expression in transgenic D. melanogaster. Through yeast one-hybrid assays we confirm that the Eip74EF-PA transcription factor directly binds to the 129 bp sciarid CRM. Together, these results contribute to the characterization of an insect CRM and indicate that the ecdysone gene regulatory network that promotes metamorphosis is conserved between D. melanogaster and the sciarid B. hygida.