Introduction Freshwater ecosystems provide propitious conditions for the acquisition and spread of antibiotic resistance genes (ARGs), and integrons play an important role in this process. Material and methods In the present study, the diversity of putative environmental integron-cassettes, as well as their potential bacterial hosts in the Velhas River (Brazil), was explored through intI-attC and 16S rRNA amplicons deep sequencing. Results and discussion ORFs related to different biological processes were observed, from DNA integration to oxidationreduction. ARGs-cassettes were mainly associated with class 1 mobile integrons carried by pathogenic Gammaproteobacteria, and possibly sedentary chromosomal integrons hosted by Proteobacteria and Actinobacteria. Two putative novel ARG-cassettes homologs to fosB3 and novA were detected. Regarding 16SrRNA gene analysis, taxonomic and functional profiles unveiled Proteobacteria, Bacteroidetes, Firmicutes, and Actinobacteria as dominant phyla. Betaproteobacteria, Alphaproteobacteria, and Actinobacteria classes were the main contributors for KEGG orthologs associated with resistance. Conclusions Overall, these results provide new information about environmental integrons as a source of resistance determinants outside clinical settings and the bacterial community in the Velhas River.

No abstract

Wastewater treatment plants (WWTPs) represent an important reservoir of antibiotic resistance determinants. Although many studies have been conducted to evaluate resistance profiles in Enterobacteriaceae isolates from this setting, the dynamics of this phenomenon are poorly known to the bacterium Pseudomonas aeruginosa. Here we aimed to evaluate the resistance profiles and the production of AmpC β-lactamase in P. aeruginosa isolates from a domestic full-scale WWTP. Samples of the raw sewage and effluent were collected and the bacterium P. aeruginosa was isolated on cetrimide agar. Susceptibility to β-lactams, fluoroquinolones and aminoglycosides was evaluated by the disc diffusion method, and the presence of AmpC β-lactamase was investigated phenotypically and by molecular method. We recovered 27 isolates of P. aeruginosa. Of these, 81.5% were susceptible to all antimicrobials tested. However, a considerable rate of resistance to carbapenems (11%) was found among the isolates. Twenty-two isolates were positive in the phenotypic test for inducible AmpC β-lactamase but the bla gene was only identified in four isolates, suggesting the presence of other independent resistance mechanisms besides this β-lactamase. In summary, we have shown that P. aeruginosa isolates from a domestic WWTP represents a potential reservoir of bla genes and other resistance determinants, including those that result in low susceptibility to carbapenems and aminoglycosides.

Although Lactobacillus species are recognized as normal inhabitants of porcine gastric mucosa, the association of these bacteria with health status or gastric ulcer disease has never been considered. We investigated the bacterial load of Lactobacillus isolated from the antrum, corpus, and pars esophagea of stomachs with (n = 13) and without (n = 10) ulcer of the pars esophagea of slaughtered pigs. We also evaluated in vitro antagonistic properties against typical pathogens of strains isolated from stomachs without ulcer. To quantify Lactobacillus, gastric mucosa samples obtained with 5 mm biopsy punches were smeared on MRS agar and colonies were counted after 48 h of incubation under anaerobic conditions. The score of Lactobacillus was significantly greater in the antrum and corpus of stomachs without ulcer (P < 0.001 for both) when compared with stomachs with ulcer. Fingerprint profiles, obtained by repetitive sequence-based PCR using (GTG) primers, showed that the isolates were highly diverse. The reduction of Lactobacillus load in porcine stomachs may be a contributing factor for gastric ulcer. Strains isolated from healthy stomachs, which showed a wide spectrum of antagonistic activity against pathogens, may be viewed as an untapped source of bacteria with potential beneficial properties that deserve to be further investigated.

Ammonia-oxidizing archaea (AOA) and ammonia-oxidizing bacteria (AOB) are a diverse and functionally important group in the nitrogen cycle. Nevertheless, AOA and AOB communities driving this process remain uncharacterized in tropical freshwater sediment. Here, the effect of human settlement on the AOA and AOB diversity and abundance have been assessed by phylogenetic and quantitative PCR analyses, using archaeal and bacterial amoA and 16S rRNA genes. Overall, each environment contained specific clades of amoA and 16S rRNA genes sequences, suggesting that selective pressures lead to AOA and AOB inhabiting distinct ecological niches. Human settlement activities, as derived from increased metal and mineral nitrogen contents, appear to cause a response among the AOB community, with Nitrosomonas taking advantage over Nitrosospira in impacted environments. We also observed a dominance of AOB over AOA in mining-impacted sediments, suggesting that AOB might be the primary drivers of ammonia oxidation in these sediments. In addition, ammonia concentrations demonstrated to be the driver for the abundance of AOA, with an inversely proportional correlation between them. Our findings also revealed the presence of novel ecotypes of Thaumarchaeota, such as those related to the obligate acidophilic Nitrosotalea devanaterra at ammonia-rich places of circumneutral pH. These data add significant new information regarding AOA and AOB from tropical freshwater sediments, albeit future studies would be required to provide additional insights into the niche differentiation among these microorganisms.

The establishment of invading organisms in natural ecosystems is one of the most serious environmental issues. In Brazil, the invasive species Limnoperna fortunei (Dunker, 1857), the golden mussel, is a mollusk capable of causing major changes in water systems, generating social and economic impacts, given its biofouling capacity. Limnoperna fortunei can easily block pipes and heat exchangers in the water systems of hydroelectric power plants due to its ability to strongly adhere to the substrate using its byssus -a bundle of filaments secreted by these animals. Therefore, the early detection of this invader is essential for management actions to be immediate, in order to control population growth rate at the beginning of the invasive process, preventing this environment from serving as a source for new infestations. The implantation of a method that integrates the active monitoring of prioritized areas, laboratory techniques, including molecular biology methods, and the sharing of hydrographic data between basin managers and users for early detection of the presence of species in Brazilian waters appears as an efficient option to prevent and control invasions.

No abstract

Among invasive species known to occur in South America, the bivalve mollusc Limnoperna fortunei, which the presence is linked to several environmental and economic problems. Early detection and mitigation actions are needed to limit its impact in the remaining L. fortunei-free areas. PCR-based molecular methods have become the gold standard methodology for L. fortunei detection. However, PCR-based methods require complex logistics from field sampling to laboratory processing. Thus, the use of methods that can be directly applied in the field can speed up the detection process. This work aimed to establish, for the first time, the loop-mediated isothermal amplification (LAMP) method for the detection of L. fortunei, with perspectives for in situ application. A set of primers designed for LAMP was tested for amplification of DNA from L. fortunei adult tissues and environmental samples containing bivalve larvae. The test showed a limit of detection as low as 0.01 ng of DNA obtained from adult tissue samples and a minimum reaction time of 60 min. The set of primers used seems to be specific for L. fortunei, since there was no cross-amplification with other bivalve or invasive molluscs that co-occur with the golden mussel in the same environment. The LAMP technique also proved to be efficient in amplifying DNA derived from L. fortunei larvae, demonstrating it to be a robust method regarding potential environmental reaction inhibitors. Although the results obtained here were acquired under controlled laboratory conditions, the LAMP method is a promising tool to integrate L. fortunei invasion monitoring protocols.