Comparison of the Antibiotic Resistance of Escherichia coli Populations from Water and Biofilm in River Environments.

Antibiotic-resistant, facultative pathogenic bacteria are commonly found in surface water; however, the factors influencing the spread and stabilization of antibiotic resistance in this habitat, particularly the role of biofilms, are not fully understood. The extent to which bacterial populations in biofilms or sediments exacerbate the problem for specific antibiotic classes or more broadly remains unanswered. In this study, we investigated the differences between the bacterial populations found in the surface water and sediment/biofilm of the Mur River and the Drava River in Austria. Samples of Escherichia coli were collected from both the water and sediment at two locations per river: upstream and downstream of urban areas that included a sewage treatment plant. The isolates were subjected to antimicrobial susceptibility testing against 21 antibiotics belonging to seven distinct classes. Additionally, isolates exhibiting either extended-spectrum beta-lactamase (ESBL) or carbapenemase phenotypes were further analyzed for specific antimicrobial resistance genes. E. coli isolates collected from all locations exhibited resistance to at least one of the tested antibiotics; on average, isolates from the Mur and Drava rivers showed 25.85% and 23.66% resistance, respectively. The most prevalent resistance observed was to ampicillin, amoxicillin-clavulanic acid, tetracycline, and nalidixic acid. Surprisingly, there was a similar proportion of resistant bacteria observed in both open water and sediment samples. The difference in resistance levels between the samples collected upstream and downstream of the cities was minimal. Out of all 831 isolates examined, 13 were identified as carrying ESBL genes, with 1 of these isolates also containing the gene for the KPC-2 carbapenemase. There were no significant differences between the biofilm (sediment) and open water samples in the occurrence of antibiotic resistance. For the E. coli populations in the examined rivers, the different factors in water and the sediment do not appear to influence the stability of resistance. No significant differences in antimicrobial resistance were observed between the bacterial populations collected from the biofilm (sediment) and open-water samples in either river. The different factors in water and the sediment do not appear to influence the stability of resistance. The minimal differences observed upstream and downstream of the cities could indicate that the river population already exhibits generalized resistance.

Antimicrobial Residues in Food from Animal Origin-A Review of the Literature Focusing on Products Collected in Stores and Markets Worldwide.

The extensive use of antibiotics leads to antibiotic residues in frequently consumed foods. Generally, the main use of antibiotics in animals is to treat and prevent diseases and growth promotion. However, the residues and their breakdown products have several side effects on the human body and, in a broader sense, on the environment. In relation to the human body, the frequency of mutations is increased, the bone marrow is damaged (chloramphenicol), and the reproductive organs of humans are affected. Carcinogenic effects have been found with antibiotics such as sulfamethazine, oxytetracycline, and furazolidone. We summarized data from 73 scientific studies reporting antimicrobial residues in animal products that were freely available for sale. The studies were published in English starting from 1999 till 2021 and identified through the Pubmed search engine. The aims were to find out which antibiotics, legal or illegal, could be found in animal foods worldwide. Which are stable to get into the food chain and exceed the maximum residue limits (MRL) regarding the EU guidelines as a comparison. Reducing antimicrobial residues in food from animal origin and, in addition to this, fighting the tremendous growth and spread of antimicrobial resistance will undoubtedly be one of the most difficult food safety challenges in the coming years.

Molecular basis of the facilitation of the heterooligomeric GIRK1/GIRK4 complex by cAMP dependent protein kinase.

G-protein activated inwardly rectifying K(+) channels (GIRKs) of the heterotetrameric GIRK1/GIRK4 composition mediate I(K+ACh) in atrium and are regulated by cAMP dependent protein kinase (PKA). Phosphorylation of GIRK1/GIRK4 complexes promotes the activation of the channel by the G-protein Gßγ-dimer ("heterologous facilitation"). Previously we reported that 3 serines/threonines (S/Ts) within the GIRK1 subunit are phosphorylated by the catalytic subunit of PKA (PKA-cs) in-vitro and are responsible for the acute functional effects exerted by PKA on the homooligomeric GIRK1(F137S) (GIRK1(⁎)) channel. Here we report that homooligomeric GIRK4(WT) and GIRK4(S143T) (GIRK4(⁎)) channels are clearly regulated by PKA phosphorylation. Heterooligomeric channels of the GIRK1(S385CS401CT407C)/GIRK4(WT) composition, where the GIRK1 subunit is devoid of PKA mediated phosphorylation, exhibited reduced but still significant acute effects (reduction during agonist application was ≈49% compared to GIRK1(WT)/GIRK4(WT)). Site directed mutagenesis of truncated cytosolic regions of GIRK4 revealed four serines/threonines (S/Ts) that were heavily phosphorylated by PKA-cs in vitro. Two of them were found to be responsible for the acute effects exerted by PKA in vivo, since the effect of cAMP injection was reduced by ≈99% in homooligomeric GIRK4(⁎T199CS412C) channels. Coexpression of GIRK1(WT)/GIRK4(T199CS412C) reduced the acute effect by ≈65%. Only channels of the GIRK1(S385CS401CT407C)/GIRK4(T199CS412C) composition were practically devoid of PKA mediated effects (reduction by ≈97%), indicating that both subunits contribute to the heterologous facilitation of I(K+ACh).

The contribution of TRPV4-mediated calcium signaling to calcium homeostasis in endothelial cells.

A large variety of cation transport systems are involved in the regulation of calcium homeostasis in endothelial cells. The focus of the present study is to determine the contribution of nonselective cation channels from the TRP (transient receptor potential) family to cellular calcium homeostasis of porcine aortic endothelial cells (PAEC). One member of the TRPV (vanniloid) subfamily, TRPV4, has previously been shown to be involved in cation transport induced by a large variety of stimulations including osmolarity, temperature, mechanical stress, and phosphorylation. Here, we demonstrate the existence of several TRP proteins, including TRPV4, in PAEC using RT-PCR. To test whether this channel is functional, we performed FURA-2 calcium measurements and whole-cell patch-clamp experiments. We observed the induction of large calcium signals following mechanical stress, altered extracellular temperature, and the selective TRPV4 activator 4-alpha -PDD. These effects were diminished in the presence of the TRPV4 inhibitor miconazole, suggesting the involvement of this channel in mediating endothelial calcium signals. The large amounts of transported calcium and the short signaling ways suggest a potentially important role of this channel in many physiological processes.