The environment is one of the main reservoirs of antibiotic resistance genes (ARGs) but multidrug resistant (MDR) environmental isolates are barely characterised. As suggested by the name, Pedobacter species have been predominantly isolated from soils, but are also recovered from water (including drinking water), chilled food, fish, compost, sludge, glaciers and other extreme environments. The susceptibility phenotype of Pedobacter lusitanus NL19 (isolated from a deactivated uranium mine), its closely related species and the genus type strain were investigated. All strains are MDR bacteria, resistant to β-lactams, colistin, aminoglycosides and ciprofloxacin. Therefore, Pedobacter spp. are likely intrinsically resistant to β-lactams (including ertapenem) and to other three classes of antibiotics. 6%–8% of their total protein-encoding genes encode a diverse collection of putative ARGs, including β-lactamases. These enzymes are highly abundant in all the other Pedobacter strains with sequenced genomes, especially class C, class B3 and class A. LUS-1 and PLN-1 were further characterised in E. coli. LUS-1 is a class A β-lactamase and it conferred an increase in the MIC of cefotaxime, albeit very low. PLN-1 is a class B3 β-lactamase with carbapenemase activity, conferring resistance to ertapenem and a 66x and 16x increase in the MIC of imipenem and meropenem, respectively. PLN-1 also hydrolyses ampicillin, 1st and 3rd generation cephalosporins, and at a lower extent cephamycins and 4th generation cephalosporins. Therefore, Pedobacter spp. encode a large and diverse arsenal of resistance mechanisms that make them environmental superbugs.

Environmental antimicrobial resistance (AMR) has drawn increasing attention due to its great risk to human health. The aim of this study was to investigate AMR and genotyping of Vibrio parahaemolyticus isolates (n = 114) recovered from shrimp mariculture environment in China. The isolates exhibited a high rate of resistance to streptomycin (78.9%), ampicillin (64.9%) and gentamicin (53.5%). Furthermore, multi-drug resistance was highly prevalent (61.4%), in which 95.9% of these ampicillin-resistant isolates were primarily mediated by blaCARB-17. Surprisingly, doxycylcine, florfenicol, and trimethoprim/sulfamethoxazole (TMP/SMZ) resistance genes occurred in susceptible isolates. Moreover, 114 isolates were grouped into unique pulsed field gel electrophoresis patterns. These findings suggest the need for the prudent use of antimicrobial agents on mariculture farms, in order to control the dissemination of antimicrobial resistant V. parahaemolyticus.

Here we present the findings of a study where 598 isolates of Escherichia coli (351 derived from seawater; 247 derived from the Venus clam, Circenita callipyga) were obtained from Kuwait's marine environment. Isolates were screened for their potential resistance to an array of 23 commonly deployed frontline antibiotics. Results demonstrate the resistant was widespread across all sites with high-levels of resistance (seawater: summer 89–64%; winter 90–57% and biota: summer 77%; winter 88%) observed to at least 1 of the 23 antibiotics tested. Resistance to Ampicillin was by far the most widely observed profile in seawater and biota across both summer and winter seasons, with 55.9 to 70.9% isolates displaying resistance to this antibiotic. This study demonstrates the potential of AMR screening to be used in Kuwait to detect issues related to water quality and the consequences it may pose for human health.

The aim of the present study was to verify the antimicrobial susceptibility profile and virulence factors of Vibrio parahaemolyticus isolated from water and bivalve mollusks. A high percentage of V. parahaemolyticus was isolated in natura, processed bivalves tissues, and surrounding water (75%, 20%, and 59%, respectively). The most potential virulence phenotype in V. parahaemolyticus isolates was amylase production (97%) followed by DNase (83%), phospholipase (70%), β-hemolytic activity (57%). The tdh and trh genes were not detected. Besides, a high antimicrobial resistance was observed for ampicillin (97%), minimum inhibitory concentration [MIC] = 400 μg and cephalothin (93%, MIC ≤ 100 μg). The absence of expression of tdh and trh virulence genes excluded the toxigenic potential of V. parahaemolyticus isolates; however, the high prevalence of antimicrobial resistance among the environmental strains is a risk to human health.

The aim of the study was to determine the antimicrobial resistance profile and the occurrence of extended-spectrum beta-lactamase genes and to analyze the genetic diversity of Escherichia coli strains isolated from the environment of horse riding centers. The study was conducted using E. coli strains isolated from the air, manure, and horse nostril swabs in three horse riding centers differing in the system of horse keeping—stable (OJK Pegaz and KJK Szary) and free-range (SKH Nielepice). Resistance to antibiotics was determined using the disk-diffusion method, and the PCR technique was employed to detect the extended-spectrum β-lactamase (ESBL) genes, while the genetic diversity of strains was assessed by rep-PCR. A total of 200 strains were collected during the 2-year study, with the majority isolated from KJK Szary, while the smallest number was obtained from SKH Nielepice. The strains were mostly resistant to ampicillin, aztreonam, and ticarcillin. The tested strains were most frequently resistant to one or two antibiotics, with a maximum of ten antimicrobials at the same time. Two multidrug-resistant (MDR) strains were detected in OJK Pegaz while in KJK Szary there were two MDR and one extensively drug-resistant (XDR) strain. The ESBL mechanism was most frequently observed in OJK Pegaz (20.31% of strains) followed by KJK Szary (15.53% of strains) and SKH Nielepice (15.15% of strains). Among the ESBL-determining genes, only blaTEM and blaCTXM-9 were detected—blaTEM was mostly found in KJK Szary (53.40% of strains), while the second detected gene—blaCTXM-9—was most frequent in SKH Nielepice (6.06% of strains). The rep-PCR genotyping showed high variation among the analyzed strains, whereas its degree differed between the studied facilities, indicating that the type of horse keeping (stable vs. free-range) affects the genetic diversity of the E. coli strains. Having regard to the fact that the tested strains of E. coli were derived from non-hospitalized horses that were not treated pharmacologically, we can assume that the observed antimicrobial resistance may be of both—natural origin, i.e., not the result of the selection pressure, and acquired, the source of which could be people present in the horse riding facilities, the remaining horses which were not included in the study, and air, as well as water, fodder, and litter of the animals. Therefore, it can be concluded that the studied horses are the source of resistant E. coli and it is reasonable to continue monitoring the changes in antimicrobial resistance in those bacteria.

Bacterial biofilm production is recognized as a strategy that helps aquatic bacteria in resisting to the presence of several kinds of pollutants, including antibiotics, in the bulk environment. The Pasvik River, located between Norway, Russia and Finland, is a sub-Arctic site polluted by wastes from metallurgic and mining activities. In order to study whether and to what extent bacteria are able to produce biofilms, and to assess whether this physiological characteristic influences their resistance to antibiotics, an investigation was performed on bacteria isolated from water and sediment collected along the Pasvik River course during two surveys (May and July). Bacterial strains were screened for their biofilm production and profiles of susceptibility to antibiotics. Results showed that biofilm formation was a widespread characteristic of the isolates. Most of them were also resistant to several antibiotics, such as ampicillin (100% of the isolates) as well as cefazolin, cefoxitin, ceftriaxone, mezlocillin, nitrofurantoin and sisomicin (90% of the total strains). This study shows a significant association between biofilm formation and antibiotic resistance at inner stations both in water and in sediments in May only. This suggests that in Pasvik River colder temperature may stimulate bacterial aggregation into biofilm and simultaneously decrease bacterial susceptibility to antibiotics; since the occurrence of antibiotic resistance has frequently been linked to the presence of pollutants, this result could represent a strategy of bacterial survival under altered environmental conditions.

The interactive effects of binary antibiotic mixtures of spiramycin (SP) and ampicillin (AMP) on Microcystis aeruginosa (MA) in terms of growth as well as microcystin production and extracellular release were investigated through the response surface methodology (RSM). SP with higher 50 and 5% effective concentrations in MA growth was more toxic to MA than AMP. RSM model for toxic unit approach suggested that the combined toxicity of SP and AMP varied from synergism to antagonism with SP/AMP mixture ratio decreasing from reversed equitoxic ratio (5:1) to equitoxic ratio (1:5). Deviations from the prediction of concentration addition (CA) and independent action (IA) model further indicated that combined toxicity of target antibiotics mixed in equivalent ratio (1:1) varied from synergism to antagonism with increasing total dose of SP and AMP. With the increase of SP/AMP mixture ratio, combined effect of mixed antibiotics on MA growth changed from stimulation to inhibition due to the variation of the combined toxicity and the increasing proportion of higher toxic component (SP) in the mixture. The mixture of target antibiotics at their environmentally relevant concentrations with increased total dose and SP/AMP mixture ratio stimulated intracellular microcystin synthesis and facilitated MA cell lysis, thus leading to the increase of microcystin productivity and extracellular release.

The rapid increase in the number and volume of chemical substances being used in modern society has been accompanied by a large number of potentially hazardous chemicals being found in environmental samples. In Vietnam, the monitoring of chemical substances is mainly limited to a small number of known pollutants in spite of rapid economic growth and urbanization, and there is an urgent need to examine a large number of chemicals to prevent impacts from expanding environmental pollution. However, it is difficult to analyze a large number of chemicals using existing methods, because they are time consuming and expensive. In the present study, we determined 1153 substances to grasp a pollution picture of microcontaminants in the aquatic environment. To achieve this objective, we have used two comprehensive analytical methods: (1) solid-phase extraction (SPE) and LC-TOF-MS analysis, and (2) SPE and GC-MS analysis. We collected 42 samples from northern (the Red River and Hanoi), central (Hue and Danang), and southern (Ho Chi Minh City and Saigon-Dongnai River) Vietnam. One hundred and sixty-five compounds were detected at least once. The compounds detected most frequently (>40 % samples) at μg/L concentrations were sterols (cholesterol, beta-sitosterol, stigmasterol, coprostanol), phthalates (bis(2-ethylhexyl) phthalate and di-n-butyl phthalate), and pharmaceutical and personal care products (caffeine, metformin). These contaminants were detected at almost the same detection frequency as in developed countries. The results reveal that surface waters in Vietnam, particularly in the center of large cities, are polluted by a large number of organic micropollutants, with households and business activities as the major sources. In addition, risk quotients (MEC/PNEC values) for nonylphenol, sulfamethoxazole, ampicillin, acetaminophen, erythromycin and clarithromycin were higher than 1, which indicates a possibility of adverse effects on aquatic ecosystems.

Cu(II)-catalyzed hydrolysis of β-lactam antibiotics has been well-identified and recognized as the key mechanism of antibiotic degradation. However, the overlooked Cu(II) oxidation susceptibly also plays an important role comparably with hydrolysis. This study evaluated the roles of hydrolysis and oxidation in Cu(II)-catalyzed degraded ampicillin (AMP), as a typical β-lactam antibiotic, under relevant environmental conditions (pH 5.0, 7.0, and 9.0; oxygen 0.2 and 6.2 mg/L). Under AMP and Cu(II) molar ratio of 1:1, AMP degradation was the fastest at pH 9.0, followed by pH 5.0 and pH 7.0. The facilitation of oxygen on AMP degradation was notable at pH 5.0 and 7.0 rather than pH 9.0. AMP degradation rate increased from 21.8% in 0.2 mg/L O₂ solution to 85.9% in 6.2 mg/L O₂ solution at pH 7.0 after 4-h reaction. AMP oxidation was attributed to both oxygen-derived Cu(I)/Cu(II) cycle and intermediate reactive oxygen species (HO. and O₂.⁻). Several intermediate and final products in AMP degradation were firstly identified by LC-quadrupole time-of-flight-MS analysis. Phenylglycine primary amine on the AMP structure was the essential complexation site to proceed with the oxidation reaction. The oxidation of AMP preferentially occurred on the β-lactam structure. The inherent mechanisms related to pH and oxygen conditions were firstly investigated, which could enhance the understanding of both oxidation and hydrolysis mechanisms in AMP degradation. This study not only has an important implication in predicting β-lactam antibiotic transformation and fate in natural environment but also benefits the developing of strategies of antibiotic control to reduce the environmental risk.