Sul1 Genes Research Articles

Effects of Zn and oxytetracycline on mobile genetic elements, antibiotic resistance genes, and microbial community evolution in soil

Antibiotics and heavy metals added to livestock and poultry feed are excreted in manure, which is added to agricultural soil and causes severe pollution. However, the effects of oxytetracycline (OTC) and zinc (Zn), which are present at relatively high levels in feed additives, on antibiotic resistance genes (ARGs), mobile genetic elements (MGEs), and microbial communities have not been comprehensively studied. This study evaluated the effects of OTC and Zn on environmental factors, microorganisms, MGEs, and ARGs. The expression of MGEs in soil was stimulated by adding Zn at concentrations of 500 and 1000 mg/kg or OTC at concentrations of 30 and 100 mg/kg; however, the addition of their combination hindered the expression of MGEs in soil. The abundance of total MGEs and ARGs tended to decrease with increasing concentrations of Zn and OTC and the number of incubation days. Low and high OTC concentrations strongly inhibited sul and tet resistance genes, respectively. Network analysis showed that changes in the population of Firmicutes and Proteobacteria had the greatest impact on ARG abundance. Redundancy analysis revealed that MGEs, particularly intI2, facilitated the transfer and spread of ARGs and had the greatest impact on changes in ARG abundance. These findings provide reference values for the prevention and resolution of ecological and environmental risks posed by the presence of Zn and OTC in organic manure soil.

Marine bacteria harbor the sulfonamide resistance gene sul4 without mobile genetic elements.

Marine bacteria are possible reservoirs of antibiotic-resistance genes (ARGs) originating not only from clinical and terrestrial hot spots but also from the marine environment. We report here for the first time a higher rate of the sulfonamide-resistance gene sul4 in marine bacterial isolates compared with other sul genes. Among four sulfonamide-resistance genes (sul1, sul2, sul3, and sul4), sul4 was most abundant (45%) in 74 sulfonamide-resistant marine isolates by PCR screening. The order of abundance was sul4 (33 isolates) >sul2 (6 isolates) >sul3 (5 isolates) >sul1 (1 isolate). Whole-genome sequencing of 23 isolates of sul4-expressing α- and γ-proteobacteria and bacilli revealed that sul4 was not accompanied by known mobile genetic elements. This suggests that sul4 in these marine isolates is clonally transferred and not horizontally transferable. Folate metabolism genes formed a cluster with sul4, suggesting that the cluster area plays a role in folate metabolism, at which sul4 functions as a dihydropteroate synthase. Thus, sul4 might be expressed in marine species and function in folate synthesis, but it is not a transferable ARG.

Mining-related multi-resistance genes in sulfate-reducing bacteria treatment of typical karst nonferrous metal(loid) mine tailings in China.

Management of tailings at metal mine smelter sites can reduce the potential hazards associated with exposure to toxic metal(loid)s and residual organic flotation reagents. In addition, microbes in the tailings harboring multi-resistance genes (e.g., tolerance to multiple antimicrobial agents) can cause high rates of morbidity and global economic problems. The potential co-selection mechanisms of antibiotic resistance genes (ARGs) and metal(loid) resistance genes (MRGs) during tailings sulfate-reducing bacteria (SRB) treatment have been poorly investigated. Samples were collected from a nonferrous metal mine tailing site treated with an established SRB protocol and were analyzed for selected geochemical properties and high throughput sequencing of 16S rRNA gene barcoding. Based on the shotgun metagenomic analysis, the bacterial domain was dominant in nonferrous metal(loid)-rich tailings treated with SRB for 12 months. KEGGs related to ARGs and MRGs were detected. Thiobacillus and Sphingomonas were the main genera carrying the bacA and mexEF resistance operons, along with Sulfuricella which were also found as the main genera carrying MRGs. The SRB treatment may mediate the distribution of numerous resistance genes. KOs based on the metagenomic database indicated that ARGs (mexNW, merD, sul, and bla) and MRGs (czcABCR and copRS genes) were found on the same contig. The SRB strains (Desulfosporosinus and Desulfotomaculum), and the acidophilic strain Acidiphilium significantly contributed to the distribution of sul genes. The functional metabolic pathways related to siderophores metabolism were largely from anaerobic genera of Streptomyces and Microbacterium. The presence of arsenate reductase, metal efflux pump, and Fe transport genes indicated that SRB treatment plays a key role in the metal(loid)s transformation. Overall, our findings show that bio-treatment is an effective tool for managing ARGs/MRGs and metals in tailings that contain numerous metal(loid) contaminants.

Combined effects of microplastics and antibiotic-resistant bacteria on Daphnia magna growth and expression of functional genes

Microplastics could act as vectors for the transport of harmful bacteria, such as pathogens and antibiotic resistance bacteria (ARB), but their combined effects have not been reported yet. Here, ARB Shigella flexneri with sulfonamides resistance and micro-polystyrene (micro-PS) were used to investigate their possible combined effects on the growth and expression of functional genes in Daphnia magna. Results showed that micro-PS colonized with S. flexneri were ingested by D. magna and blocked in their intestine after 24 h exposure. Changes were observed in the life history and morphology of D. magna, as well as the expression of functional genes in all treatments, but with no difference in the survival rate. We also determined the expression of six functional genes involved in energy and metabolism (arginine kinase, AK) and oxidative stress response (thioredoxin reductase, TRxR, catalase, CAT, and glutathione S-transferases, GSTs), as well as in growth, development and reproduction (vitellogenin, Vtg1 and ecdysone receptor, EcR). AK and Vtg1 did not show significant differences, however, EcR was down-regulated and the other three genes (TRxR, CAT, GSTs) were up-regulated in the combined-treated group. Antibiotic resistance gene (ARGs) sul1 was detected when exposed to micro-PS colonized with S. flexneri., suggesting that D. magna could acquire resistance genes through microplastic biofilms. These results indicated that MPs could act as a carrier of ARB to transfer ARGs into D. magna, and affect the life history, morphology, and the expression of related functional genes of D. magna, to adapt to the stress caused by MPs and ARB.

Removal of typical sulfonamide resistance genes by ultraviolet/hydrogen peroxide advanced oxidation process in mariculture wastewater

Antibiotics are extensively used in the mariculture sector, leading to the emergence and dissemination of antibiotic resistance genes (ARGs) and posing a serious threat to public health. Therefore, it is urgent to remove and control of ARGs in the mariculture environment. In this study, in order to assess the efficiency and mechanism of ARGs removal, we employed the ultraviolet/hydrogen peroxide (UV/H2O2) advanced oxidation process (AOP) to treat mariculture wastewater containing prevalent sulfonamide resistance genes, namely sul1, sul2, and intl1. The results demonstrated that UV/H2O2 AOP effectively eliminated ARGs, achieving a significant reduction of 2.51–2.71 log for 16S rRNA, intl1, sul1, and sul2 genes after 10 min of treatment with a UV dose of 570 mJ·cm−2, 0.01 mol·L−1 H2O2, and pH 3. The removal of ARGs was influenced by the concentration of the oxidizing agent. Specifically, as the H2O2 concentration increased, the removal of ARGs initially increased and then decreased. Moreover, UV/H2O2 AOP exhibited different removal efficiencies for intracellular ARGs (iARGs) and extracellular ARGs (eARGs). The absolute abundance of iARGs gradually decreased, the eARGs were less impacted by the UV/H2O2 AOP treatment. Furthermore, the microbial community exhibited distinct sensitivities to UV/H2O2 AOP and UV treatment. Proteobacteria and Campylobacterota consistently appeared as dominant phyla, with Sulfurovum being the dominant genus. These findings shed light on the control of ARGs in mariculture wastewater and confirmed the promising prospects of UV/H2O2 AOP as an effective approach.

Impact of corrosion inhibitors on antibiotic resistance, metal resistance, and microbial communities in drinking water.

Corrosion inhibitors, including zinc orthophosphate, sodium orthophosphate, and sodium silicate, are commonly used to prevent the corrosion of drinking water infrastructure. Metals such as zinc are known stressors for antibiotic resistance selection, and phosphates can increase microbial growth in drinking water distribution systems (DWDS). Yet, the influence of corrosion inhibitor type on antimicrobial resistance in DWDS is unknown. Here, we show that sodium silicates can decrease antibiotic resistant bacteria (ARB) and antibiotic-resistance genes (ARGs), while zinc orthophosphate increases ARB and ARGs in source water microbial communities. Based on controlled bench-scale studies, zinc orthophosphate addition significantly increased the abundance of ARB resistant to ciprofloxacin, sulfonamides, trimethoprim, and vancomycin, as well as the genes sul1, qacEΔ1, an indication of resistance to quaternary ammonium compounds, and the integron-integrase gene intI1. In contrast, sodium silicate dosage at 10 mg/L resulted in decreased bacterial growth and antibiotic resistance selection compared to the other corrosion inhibitor additions. Source water collected from the drinking water treatment plant intake pipe resulted in less significant changes in ARB and ARG abundance due to corrosion inhibitor addition compared to source water collected from the pier at the recreational beach. In tandem with the antibiotic resistance shifts, significant microbial community composition changes also occurred. Overall, the corrosion inhibitor sodium silicate resulted in the least selection for antibiotic resistance, which suggests it is the preferred corrosion inhibitor option for minimizing antibiotic resistance proliferation in DWDS. However, the selection of an appropriate corrosion inhibitor must also be appropriate for the water chemistry of the system (e.g., pH, alkalinity) to minimize metal leaching first and foremost and to adhere to the lead and copper rule. IMPORTANCE Antibiotic resistance is a growing public health concern across the globe and was recently labeled the silent pandemic. Scientists aim to identify the source of antibiotic resistance and control points to mitigate the spread of antibiotic resistance. Drinking water is a direct exposure route to humans and contains antibiotic-resistant bacteria and associated resistance genes. Corrosion inhibitors are added to prevent metallic pipes in distribution systems from corroding, and the type of corrosion inhibitor selected could also have implications on antibiotic resistance. Indeed, we found that sodium silicate can minimize selection of antibiotic resistance while phosphate-based corrosion inhibitors can promote antibiotic resistance. These findings indicate that sodium silicate is a preferred corrosion inhibitor choice for mitigation of antibiotic resistance.

Phenotypic and genotypic antimicrobial resistance correlation and plasmid characterization in Salmonella spp. isolates from Italy reveal high heterogeneity among serovars.

The spread of antimicrobial resistance among zoonotic pathogens such as Salmonella is a serious health threat, and mobile genetic elements (MGEs) carrying antimicrobial resistance genes favor this phenomenon. In this work, phenotypic antimicrobial resistance to commonly used antimicrobials was studied, and the antimicrobial resistance genes (ARGs) and plasmid replicons associated with the resistances were determined. Eighty-eight Italian Salmonella enterica strains (n = 88), from human, animal and food sources, isolated between 2009 and 2019, were selected to represent serovars with different frequency of isolation in human cases of salmonellosis. The presence of plasmid replicons was also investigated. Resistances to sulphonamides (23.9%), ciprofloxacin (27.3%), ampicillin (29.5%), and tetracycline (32.9%) were the most found phenotypes. ARGs identified in the genomes correlated with the phenotypical results, with blaTEM-1B, sul1, sul2, tetA and tetB genes being frequently identified. Point mutations in gyrA and parC genes were also detected, in addition to many different aminoglycoside-modifying genes, which, however, did not cause phenotypic resistance to aminoglycosides. Many genomes presented plasmid replicons, however, only a limited number of ARGs were predicted to be located on the contigs carrying these replicons. As an expectation of this, multiple ARGs were identified on contigs with IncQ1 plasmid replicon in strains belonging to the monophasic variant of Salmonella Typhimurium. In general, high variability in ARGs and plasmid replicons content was observed among isolates, highlighting a high level of heterogeneity in Salmonella enterica. Irrespective of the serovar., many of the ARGs, especially those associated with critically and highly important antimicrobials for human medicine were located together with plasmid replicons, thus favoring their successful dissemination.

Regulation Transcriptional of Antibiotic Resistance Genes (ARGs) in Bacteria Isolated from WWTP

The incidence of antibiotics and transcriptional regulation of ARGs in isolated bacteria from wastewater needs to be explored. By HPLC, in samples of untreated wastewater, ampicillin (49.74 ± 5.70 µg/mL), chloramphenicol (0.60 ± 0.03 µg/mL), tylosin (72.95 ± 2.03 µg/mL), and oxytetracycline (0.22 ± 0.01 µg/mL) was determined. Through metagenomic analysis identified 58 bacterial species belonging to 9 phyla and at least 14 species have shown resistance to a variety of antibiotics. Twenty-two bacterial isolates were proved to be resistant to fifteen antibiotics of new generation and used in medical research to combat infectious diseases. Fourteen strains were shown to harbor plasmids in size ranges of 2–5 Kb, 6–10 Kb and plasmids with size greater than 10 Kb. By quantitative PCR it was possible to identify genes sul, qnr, cat1, aadA1, and sat-1 gene were shown to be present in gDNA samples from treated and untreated samples of wastewater and by relative expression analysis, differential expression of cat1, ermB, act, and tetA genes was demonstrated in strains that showed identity with Escherichia coli, Bacteroides fragilis, and Salmonella thyphi, and that were stressed with different concentrations of antibiotics. The presence of ARGs in untreated water samples, as well as in bacterial isolates, was indicative that in these habitats there are microorganisms that can resist β-lactams, aminoglycosides, tetracyclines, sulfonamides, and quinolones.

The effect of sulfadiazine in manure on accumulation of sulfonamide resistance genes in freshly consumable plants

BackgroundAntibiotic resistance genes will spread via soil fertilized with animal manure to food products. Especially plants whose harvested products can be consumed freshly are of concern. The aim of this study was to assess the impact of sulfadiazine (SDZ)-manured soil on the occurrence of sulfonamide (SA) resistance genes in freshly consumable plants.MethodsSulfadiazine-containing manure was administered via soil to lettuce and leek plants. At harvest, the rhizosphere soil, roots and leaves were investigated on the presence of SDZ-resistant bacteria and sul1 and sul2 genes via qPCR. Further, the impact of SDZ in manure on bacterial community and antibiotic resistance gene composition via amplicon sequencing and shotgun metagenomics was investigated in rhizosphere soils.ResultsAmendment of SDZ to manure resulted in an increase in sul2 genes in manure. However, abundances of sul genes in rhizosphere soils was strongly determined by plant growth and not by soil treatments with SDZ-manure, which was also the case for the bacterial community composition. Effects of SDZ at low or undetectable levels in leek rhizosphere soil became evident by bacterial association network and resistome analyses, and also in roots and leaves by SDZ-selective bacterial cultivation.ConclusionsAntibiotic residues present in animal manure can lead to an increase in antibiotic resistances in food products. Plants play an important role in selection of antibiotic resistance genes present in manured soil. Transmission of antibiotic resistances via manure to the soil–plant ecosystem must be placed into the context of soils as vast reservoirs of ARGs.

Antibiotic resistance indicator genes in biofilm and planktonic microbial communities after wastewater discharge.

The spread of bacteria with antibiotic resistance genes (ARGs) in aquatic ecosystems is of growing concern as this can pose a risk of transmission to humans and animals. While the impact of wastewater treatment plant (WWTP) effluent on ARG abundance in surface waters has been studied extensively, less is known about the fate of ARGs in biofilms. The proximity and dense growth of microorganisms in combination with the accumulation of higher antibiotic concentrations in biofilms might render biofilms a reservoir for ARGs. Seasonal parameters such as water temperature, precipitation, and antibiotic concentrations should be considered as well, as they may further influence the fate of ARGs in aquatic ecosystems. Here we investigated the effect of WWTP effluent on the abundance of the sulfonamide resistance genes sul1 and sul2, and the integrase gene intI1 in biofilm and surface water compartments of a river in Germany with a gradient of anthropogenic impact using quantitative PCR. Furthermore, we analyzed the bacterial community structure in both compartments via 16S rRNA gene amplicon sequencing, following the river downstream. Additionally, conventional water parameters and sulfonamide concentrations were measured, and seasonal aspects were considered by comparing the fate of ARGs and bacterial community diversity in the surface water compartment between the summer and winter season. Our results show that biofilm compartments near the WWTP had a higher relative abundance of ARGs (up to 4.7%) than surface waters (<2.8%). Sulfonamide resistance genes were more persistent further downstream (>10 km) of the WWTP in the hot and dry summer season than in winter. This finding is likely a consequence of the higher proportion of wastewater and thus wastewater-derived microorganisms in the river during summer periods. We observed distinct bacterial communities and ARG abundance between the biofilm and surface water compartment, but even greater variations when considering seasonal and spatiotemporal parameters. This underscores the need to consider seasonal aspects when studying the fate of ARGs in aquatic ecosystems.

The response of microbial compositions and functions to chronic single and multiple antibiotic exposure by batch experiment

Understanding the response of the microbial community to external disturbances such as micropollutants is vital for ecological risk evaluation. In this study, the effect of chronic antibiotic exposure on community compositions and functions was investigated by two batch experiments. The first experiment investigated the effect of chronic sulfamethoxazole (SMX) exposure, while the second investigated the combined effect of dissolved organic matter (DOM) sources and multi-antibiotic exposure. The results showed that the community responses to chronic antibiotic exposure depended on the dynamic balance among community resistance, adaptation, recovery, and selection, leading to nonlinear composition diversity variations. The disturbance strength of chronic SMX exposure increased with concentration (0.5–50 μg/L). However, complex sources and structures of coexisting organic matter might delay the disturbance by elevating metabolic activity and generating functional redundancy. Especially, when nutrient was a limiting factor, the disturbance strength by DOM source was greater than that by chronic antibiotic exposure. The resistance of abundant taxa to external distributions resulted in a low explanation of community diversity, while rare taxa played key roles in response to community variation and thereby affected community assembly. Long-term SMX exposure reduced the number of key species and favored the deterministic assembly process by 21%. However, elevated community adaptability might weaken the influence of antibiotic selection. Chronic SMX exposure elevated the relative abundance of sulfonamide resistance genes (sul1, sul2) by a factor of 1.2–4.3, while that of nitrogen-fixing genes (nifH, nifK) and the metabolic pathways related to the toluene, ethylbenzene, and dioxin degradation decreased. However, the combined influence of DOM sources and multi-antibiotic exposure barely caused the difference in the genes linking to element metabolism and drug resistance of microbial communities between blank and exposed groups. This study suggested that more concern should be given to the chronic environmental effect of organic micropollutants.

Phenotypic and genotypic study of antibiotic-resistant Escherichia coli isolates from a wastewater treatment plant in Zulia state, Venezuela.

Antibiotic-resistance in bacteria is a global health problem, and wastewater treatment plants can play a role in their dissemination. In this work, we used PCR and plasmid transformation to characterize antibiotic-resistance and the phylogenetic groups of Escherichia coli isolated from a treatment plant in Zulia, a state in western Venezuela. Thirty-six bacteria isolates were analyzed, of which 27 resulted resistant by disc diffusion primarily to tetracycline and sulfisoxazole but also to trimethoprim, chloramphenicol, ampicillin, and cip-rofloxacin. The tetA, sul2, floR, and blaTEM resistance genes were frequently present and, in most cases, transferable. dfrA12, tetB, sul3, sul1, and aadA2genes also were detected. The integrase gene intI1 was common in multidrug-resistant isolates. These results suggest that E. coli from the treatment plant is a reservoir of antibiotic-resistance genes, which signify a potential health threat. Additionally, the phylogroup C was predominant, which is unusual and may represent an adaptation of this group to environmental conditions or per-haps the most frequent phylogroup entering from the influent.

Ultrasensitive rapid detection of antibiotic resistance genes by electrochemical ratiometric genosensor based on 2D monolayer Ti3C2@AuNPs

As an important emerging pollutant, antibiotic resistance genes (ARGs) monitoring is crucial to protect the ecological environment and public health, but its rapid and accurate detection is still a major challenge. In this study, a new single-labeled dual-signal output ratiometric electrochemical genosensor (E-DNA) was developed for the rapid and highly sensitive detection of ARGs using a synergistic signal amplification strategy of T3C2@Au nanoparticles (T3C2@AuNPs) and isothermal strand displacement polymerase reaction (ISDPR). Specially, two-dimensional monolayer T3C2 nanosheets loaded with uniformly gold nanoparticles were prepared and used as the sensing platform of the E-DNA sensor. Benefiting from excellent conductivity and large specific surface area of Ti3C2@AuNPs, the probe immobilization capacity of the E-DNA sensor is doubled, and electrochemical response signals of the E-DNA sensor were significantly improved. The proposed single-labeled dual-signal output ratiometric sensing strategy exhibits three to six times higher sensitivity for the sul2 gene than the single-signal sensing strategy, which significantly reduces cost meanwhile retaining the advantages of high sensitivity and reliability offered by conventional dual-labeled ratiometric sensors. Coupled with ISDPR amplification technology, the E-DNA sensor has a wider linear range from 10 fM to 10 nM and a limit of detection as low as 2.04 fM (S/N=3). More importantly, the E-DNA sensor demonstrates excellent specificity, good stability and reproducibility for target ARGs detection in real water samples. The proposed new sensing strategy provides a highly sensitive and versatile tool for the rapid and accurate quantitative analysis of various ARGs in environmental water samples.

Removal of oxytetracycline and sulfamethoxazole in vertical down-up flow constructed wetlands: Efficiency, removal pathways, and occurrence of antibiotic resistance genes

The extensive use of antibiotics leads to their frequent detection in the environment, posing potential threats to public health. Constructed wetlands (CWs) have been widely applied in wastewater treatment and can efficiently remove antibiotics. However, the removal of antibiotics in the CWs is still in a “black box”, and the information about the potential risks of antibiotic resistance genes (ARGs) occurrence in CWs is limited. In the present study, the removal of oxytetracycline (OTC) and sulfamethoxazole (SMZ), as well ARGs occurrence in vertical down-up flow constructed wetlands (VDUF-CWs) were assessed. The results indicated that VDUF-CWs exhibited great removal efficiency for OTC (84.3 ± 3.5 %) and SMZ (77.7 ± 3.9 %). Based on conservation of mass, the contributions of different removal pathways (i.e., microbial degradation, plant absorption, photodegradation, and substrate adsorption) to antibiotic removal were calculated. Of which, microbial degradation was found to be the dominant route in removing OTC and SMZ with the contribution of 58.52 ± 2.34 % and 65.13 ± 3.72 % respectively, followed by photodegradation (18.47 ± 3.04 % and 8.22 ± 3.94 %), plant absorption (9.01 ± 1.28 % and 7.75 ± 4.07 %) and substrate adsorption (2.08 ± 0.03 % and 1.73 ± 0.02 %). Notably, tetA, tetC, tetW, sulI, and sulII genes were detected in layer samples, and the relative abundances of the sul and tet genes were boosted with the extension of operation days, indicating that VDUF-CWs allow a risk of ARGs spread and threatening public health. The present study provided a deeper insight into the mechanism of antibiotic removal in CWs, but further explorations are required to develop the effective control strategies for eliminating ARGs from CWs.

Antibiotic resistance and virulence genes profiling of Vibrio cholerae and Vibrio mimicus isolates from some seafood collected at the aquatic environment and wet markets in Eastern Cape Province, South Africa.

The current study determines the density of Vibrio spp. and isolates V. cholerae and Vibrio mimicus from fish-anatomical-sites, prawn, crab and mussel samples recovered from fish markets, freshwater and brackish water. Virulence and antibiotic resistance profiling of isolates were carried out using standard molecular and microbiology techniques. Vibrio spp. was detected in more than 90% of samples [134/144] and its density was significantly more in fish than in other samples. Vibrio. cholerae and V. mimicus were isolated in at least one sample of each sample type with higher isolation frequency in fish samples. All the V. cholerae isolates belong to non-O1/non-O139 serogroup. One or more V. cholerae isolates exhibited intermediate or resistance against each of the eighteen panels of antibiotics used but 100% of the V. mimicus were susceptible to amikacin, gentamycin and chloramphenicol. Vibrio cholerae exhibited relatively high resistance against polymyxin, ampicillin and amoxicillin/clavulanate while V. mimicus isolates exhibited relatively high resistance against nitrofurantoin, ampicillin and polymixin. The multiple-antibiotic-resistance-index [MARI] for isolates ranges between 0 and 0.67 and 48% of the isolates have MARI that is >0.2 while 55% of the isolates exhibit MultiDrug Resistance Phenotypes. The percentage detection of acc, ant, drf18, sul1, mcr-1, blasvh, blaoxa, blatem, blaoxa48, gyrA, gyrB and parC resistance-associated genes were 2%, 9%, 14%, 7%, 2%, 25%, 7%, 2%, 2%, 32%, 25% and 27% respectively while that for virulence-associated genes in increasing other was ace [2%], tcp [11%], vpi [16%], ompU [34%], toxR [43%], rtxC [70%], rtxA [73%] and hyla [77%]. The study confirmed the potential of environmental non-O1/non-O139 V. cholerae and V. mimicus to cause cholera-like infection and other vibriosis which could be difficult to manage with commonly recommended antibiotics. Thus, regular monitoring of the environment to create necessary awareness for this kind of pathogens is important in the interest of public health.

Stability and genetic insights of the co-existence of blaCTX-M-65, blaOXA-1, and mcr-1.1 harboring conjugative IncI2 plasmid isolated from a clinical extensively-drug resistant Escherichia coli ST744 in Shanghai.

Co-existence of colistin, β-lactam and carbapenem in multidrug-resistant Enterobacteriaceae isolates poses a serious threat to public health. In this study, we investigated and characterized the co-occurrence of blaCTX-M-65, blaOXA-1, and mcr-1.1 strain isolated from a clinical extensively-drug-resistant Escherichia coli ST744 in Shanghai. Antimicrobial susceptibility test was carried out by agar dilution methods. Whole genome sequencing was conducted, and resistance genes, and sequence types of colistin in E. coli isolates were analyzed. Plasmid stability and amino acid mutations were assessed in E. coli isolates. A colistin resistant E. coli ST744, named ECPX221, was identified out of 145 fecal samples collected. The strain carries a 60,168 IncI2 plasmid with the mcr-1.1 gene. The strain also has blaCTX-M-65, blaOXA-1, dfrA14, qnrS1, cmlA5, arr2, ampC, aph(4)-Ia, sul1, and aadA5 resistance genes. The plasmid pECPX221 was capable of conjugation with an efficiency of 2.6 × 10-2. Notably, 45% of the transconjugants were determined as mcr-1.1-harboring in the colistin-free environment after 60 generation of passage. No mutations occurred in pmrB, mgrB, and phoPQ gene in the mcr-1.1-harboring transconjugants. Bioinformatic analysis indicated pECPX221 shared highly similar backbone with the previously reported mcr-1.1-harboring pAH62-1, pMFDS1339.1, pSCZE4, and p2018-10-2CC. Furthermore, sequencing and phylogenetic analyses revealed a similarity between other MCR-1-homolog proteins, indicating that ECPX221 was colistin resistant. The stable transferable mcr-1.1-harboring plasmid found in the E. coli ST744 strain indicated the high risk to disseminate the extensively-drug-resistance phenotype among Enterobacteriaceae.

Relationship between antibiotic resistance with class 1 integron and SmeDEF efflux pump encoding genes in clinical isolates of Stenotrophomonas maltophilia.

Stenotrophomonas maltophilia is an emerging multidrug-resistant organism with an increasing frequency of hospital-acquired infections predominantly in developing countries. The purpose of this study was to determine the antibiotic resistance and frequency of the smeD, class 1 integron, and sul1 genes in clinical isolates of S. maltophilia in two Iranian provinces. From January 2020 to September 2021, 38 clinical isolates of S. maltophilia were collected from patients in hospitals in Tabriz and Sanandaj provinces of Iran. S. maltophilia isolates were confirmed by standard bacteriological tests and 16S rRNA gene PCR. Disk diffusion and the MIC test strip methods were used to determine the antibiotic resistance patterns. PCR was performed to investigate the presence of smeD, class 1 integron, and sul1 genes. The antimicrobial test for the isolated S. maltophilia showed a high level of sensitivity against most of the antibiotics used. Maximum sensitivity was recorded for ciprofloxacin (100% (38/38)) and levofloxacin 100% (38/38), followed by ceftazidime (97.36% (37/38)), trimethoprim-sulfamethoxazole (81.57% (31/38)), ticarcillin-clavulanate (60.52% (23/38)), and piperacillin-tazobactam (55.26% (21/38)). We observed a high prevalence of smeD (100% (38/38)) and class 1 integron (94.73% (36/38)) genes in the isolates, and none of the isolates carried the sul1 gene. The findings from this study indicate that resistance to trimethoprim-sulfamethoxazole was not observed, and still, trimethoprim-sulfamethoxazole is the best drug with desirable antimicrobial effect in the treatment of nosocomial infections caused by S. maltophilia strains. Despite the observation of a high number of class 1 integron, the sul1 gene was not observed, which indicates the role of this gene in high-level trimethoprim-sulfamethoxazole resistance and not having a role in low-level resistance. Based on our results, clinical microbiology laboratories need continuous surveillance of resistance rates to trimethoprim-sulfamethoxazole, because of the possibility of S. maltophilia acquiring trimethoprim-sulfamethoxazole-resistance by mobile gen elements.

Serotypes, Pathotypes, Shiga Toxin Variants and Antimicrobial Resistance in Diarrheagenic Escherichia coli Isolated from Rectal Swabs and Sheep Carcasses in an Abattoir in Mexico

Sheep represent one of the main reservoirs of diarrheagenic Escherichia coli; this microorganism is an etiological agent of food-borne diseases; therefore, this work aimed to identify and characterize the principal pathotypes of diarrheagenic E. coli (DEC) obtained through rectal swabs and carcasses samples from sheep slaughtered in an abattoir at the central region of Mexico. The isolates were subjected to bacteriological identification, serotyping; phylogenetic classification; detection for virulence factors, and antimicrobial sensibility. A total of 90 E. coli isolates were obtained. It was observed through 49 E. coli isolates (54%), 8 of them from carcasses, and 43 from feces was DEC. DEC serotypes with health public relevance were found: O76:H19 (n = 5), O146:H21 (n = 3), O91:H10 (n = 1), O6:NM (n = 1), and O8:NM (n = 1). Regarding the presence of Shiga toxin-producing E.coli (STEC), 43/90 (47.7%) isolates have the stx1 w/o stx2 genes, and therefore were assigned as STEC non-O157; only one isolate expressed stx1 and eae genes and was classified as t-STEC (typical STEC). Additionally, 3/90 (3.3%) harbored only the eae gene and were classified as enteropathogenic E. coli (EPEC), the stp gene was found in 2/90 isolates (2.2%) and were classified as enterotoxigenic E. coli (ETEC); 1/90 (1.1%) isolates harboring the ipaH were classified as enteroinvasive E. coli EIEC. Regarding stx1 genes subtypes, stx1c only was found in 60.5% (26/43), followed by stx1a-stx1c 20.9% (9/43) and stx1a-stx1d 2.3% (1/43). The presence of both, stx1 and stx2 genes was found in 7/43 isolates (16.3%) from rectal swabs; the combination stx1c-stx2g was detected in 3/43 isolates (6.9%), while 4 (9.4%) isolates showed different patterns (stx1a-stx1c-stx2g; stx1c-stx2b-stx2g; stx1c-stx2b and stx1a-stx1c-stx2b-stx2g). STEC isolates showed the major diversity of phylogenetic groups, although phylogroup B1 was predominant in 90.6% (39/43) while there was only one isolate (2.3%) in each remaining phylogroup (A, B2, C, and F). All EPEC, ETEC, and EIEC isolates were clustered in phylogroup B1. We observed that 27.9% (12/43) of STEC isolates carried at least one antibiotic resistance: nine isolates expressed the tetB gene, one isolate the tetA gene, two isolates the sul2 gene, one isolate the sul1 and one isolate the sul1-tetB genes. These results highlight the importance of diarrheagenic E. coli as a potential risk for public health during the slaughtering process.

Insights into the genetic contexts of sulfonamide resistance among early clinical isolates of Acinetobacter baumannii.

Since the late 1930s, resistance to sulfonamides has been accumulating across bacterial species including Acinetobacter baumannii, an opportunistic pathogen increasingly implicated the spread of antimicrobial resistance worldwide. Our study aimed to explore events involved in the acquisition of sulfonamide resistance genes, particularly sul2, among the earliest available isolates of A. baumannii. The study utilized the genomic data of 19 strains of A. baumannii isolated before 1985. The whole genomes of 5 clinical isolates obtained from the Culture Collection University of Göteborg (CCUG), Sweden, were sequenced using the Illumina MiSeq system. Acquired resistance genes, insertion sequence elements and plasmids were detected using ResFinder, ISfinder and Plasmidseeker, respectively, while sequence types (STs) were assigned using the PubMLST Pasteur scheme. BLASTn was used to verify the occurrence of sul genes and to map their genetic surroundings. The sul1 and sul2 genes were detected in 4 and 9 isolates, respectively. Interestingly, sul2 appeared thirty years earlier than sul1. The sul2 gene was first located in the genomic island GIsul2 located on a plasmid, hereafter called NCTC7364p. With the emergence of international clone 1, the genetic context of sul2 evolved toward transposon Tn6172, which was also plasmid-mediated. Sulfonamide resistance in A. baumannii was efficiently acquired and transferred vertically, e.g., among the ST52 and ST1 isolates, as well as horizontally among non-related strains by means of a few efficient transposons and plasmids. Timely acquisition of the sul genes has probably contributed to the survival skill of A. baumannii under the high antimicrobial stress of hospital settings.

Characterization of Multiple Resistance Genes of Escherichia coli Strains Isolated from Food and Clinical Samples.

Multi-drug resistance (MDR), which is formed by the development of antimicrobial resistance, which is one of the defense mechanisms in bacteria, has pushed human beings to constantly seek new antimicrobial agents in the fight against these microorganisms. Speed and precision are very important in identifying resistance in strains with MDR that reach humans in an open system through the consumption of contaminated food or water. The main aim of this study was the molecular characterization of ESBL gene variants (blaTEM, blaOXA, blaSHV, and blaCTX-M), integron genes (int1, int2, and int3), and sulphonamide (sul1, sul2, and sul3) resistance genes by PCR from E. coli isolates originated from food and clinical samples. A total of 17 sets of primers were used for phylogenetic identification, molecular detection, and resistance and integron gene characterization of phenotypically identified E. coli isolates. The 45 red meat samples were collected from local markets, which are located in four (Adıyaman, Gaziantep, Kahramanmaraş, and Hatay) different provinces, clinical isolates were obtained from urine samples of patients with UTI from Şanlıurfa Mehmet Akif İnan Training and Research Hospital. Three gene groups were screened with 3 multiplex PCR applications in 63 food and 33 clinical isolates found to be E. coli by molecular identification. In terms of the 3 gene groups screened in food samples, the highest rates were found in the blaSHV gene at 44.44%, the sul1 gene at 69.84% and the int2 gene at 73.02%; in clinical samples, it is listed as blaCTX-M gene at 15.15%, sul2 gene at 81.82% and int1 gene at 54.55%. In terms of 3 gene groups scanned, the presence of 3 or more genes, including at least one gene from each gene group, was detected in 31 isolates from food samples and 2 isolates from clinical samples. Overall, it can be said that the high frequency of MDR genes isolated from E. coli-contaminated red meat samples and clinical samples gives a clue about the overuse of antibiotics in Türkiye.