Sul1 Genes Research Articles

Plants inhibit the relative abundance of sulfonamide resistance genes and class 1 integron by influencing bacterial community in rhizosphere of constructed wetlands

Antibiotic resistance genes (ARGs) commonly detected in wastewater can potentially lead to a health crisis. Constructed wetlands (CWs) remove ARGs and sulfonamides (SAs) from wastewater, but the importance of plants in the process is seldom reported. We compared the effect of three wetland plant species (Cyperus alternifolius, Juncus effuses, and Cyperus papyrus), sample distance from the root, and SA presence on the environmental abundance of class 1 integron (intI1) and SA resistance genes (sul) using specially designed CW rhizoboxes. Quantitative polymerase chain reaction revealed that the relative abundance of the target genes in planted CWs, especially in C. alternifolius planted CWs, was significantly lower than that in unplanted CWs (P < 0.05). The substrate in the rhizosphere or near-/moderate-rhizosphere (closest to the root) showed the lowest average relative abundance of the target genes, while the bulk substrate (without the root) showed the highest abundance of these genes, irrespective of the planted species. Further, the influence of plants was more evident after 8 weeks of wastewater treatment. The trend was the same in SA-treated and untreated groups, although the relative abundance of the target genes was significantly higher in the former (P < 0.05). The weaker correlation between the intI1 and sul genes in the rhizosphere and near-/moderate-rhizosphere in comparison to the bulk substrate in the SA group suggested that the risk of horizontal gene transfer was probably higher in the bulk substrate and unplanted CW. A partial least-squares path model revealed that dissolved organic carbon and oxygen content significantly influenced SA concentration, microbial community, and intI1 genes, and then shaping the sul genes together. Finally, redundancy analysis suggested that abundance of sul genes was influenced by bacteria enriched in the bulk substrate and unplanted CWs. The findings provide new insights into the importance for controlling risk of ARGs by wetland plants.

Dynamics of antibiotic resistance genes and microbial community in shortcut nitrification-denitrification process under antibiotic stresses.

In this study, the performance of shortcut nitrification-denitrification (SCND) at different TC and SD stress conditions (0μg/L, 1-97days; 100μg/L, 98-138days; 500μg/L, 139-175days) was investigated. Higher level antibiotic stress (500μg/L) led to the serious deterioration of nitrogen removal, and denitrification was more sensitive to antibiotic stress than nitrification. The dynamics of antibiotic resistance genes (ARGs) and microbial community were revealed by quantitative real-time PCR and 16S rDNA high-throughput sequencing, respectively. Tet-genes (tetA, tetQ, tetW), sul-genes (sulI, sulII), and mobile genetic element (intI1) in activated sludge increased by 1.2 ~ 2.5 logs with long-term exposure of antibiotic stress, and sulI, tetA, tetQ, and tetW were significantly positively correlated with intI1. Long-term antibiotics stress caused the decrease of most denitrifiers, and five genera were identified as the potential host of ARGs. The key impact factors of SCND drove the dynamics of ARGs and microbial community. Except for sulII gene, DO and FA were significantly positively correlated with ARGs, while FNA, NAR, and NO2--N showed opposite effects to ARGs. Overall, maintaining relative lower DO, higher FNA, NAR, and NO2--N conditions are not only benefit to the stable operation of SCND, but may also conducive to the control of ARG dissemination. This study provides theoretical basis on the control of ARGs in the SCND process.

Genetic characterization of clinically relevant class 1 integrons carried by multidrug resistant bacteria (MDRB) isolated from the gut microbiota of highly antibiotic treated Salmo salar

The main objective of this study was the genetic characterization of clinically relevant class 1 integrons carried by multidrug resistant bacteria isolated from the intestinal microbiota of aquaculture salmon treated with high concentrations of antibiotics. In 82 multidrug resistant bacterial isolates, the prevalence of both the conserved elements of the integrons, qacEΔ1 and sul1 genes, and the variable region (VR) was determined. Further, whole genome sequencing and complete genetic analysis was performed in VR-positive isolates. Despite the fact that 100% of the bacterial isolates presented the intI1 gene, only 12.3% carried the qacEΔ1 and sul1 genes and only two (2.4%) presented a VR with gene cassettes. In the Pseudomonas baetica 25P2F9 isolate, a VR carrying aac(6')31, qacH, and blaOXA-2 gene cassettes was described, whereas the VR of Aeromonas salmonicida 30PB8 isolate showed a dfrA14 gene cassette. The array of gene cassettes found in the Pseudomonas isolate appears with high frequency in clinically relevant pathogens such as Pseudomonas aeruginosa or Escherichia coli. Additionally, it was possible to determine that these integrons are contained in plasmids and coul be easily transferred. Resistome analysis demonstrated that both isolates carried a great diversity of antibiotic resistance genes, including many β-lactamases. Even in the Aeromonas isolate a new oxacillin-hydrolyzing beta-lactamase gene was described (blaOXA-956). The presence of multidrug resistant bacteria and clinically relevant genetic elements in the salmon intestinal microbiota make the aquaculture a hotspot in the phenomenon of antibiotic resistance; therefore, the control of antibiotics used in this activity is a key point to avoid its escalation.

Tracking antibiotic resistance through the environment near a biosolid spreading ground: Resistome changes, distribution, and metal(loid) co-selection

The application of urban wastewater treatment plants (WWTPs) products to agricultural lands has contributed to the rising level of antibiotic resistance and drawn a critical public health concern. It has not been thoroughly investigated at which spatial scales a biosolid applied area as a potentially predominant source affects surrounding soil resistomes. This study investigated distribution and impact of WWTP biosolids treated with anaerobic digestion on an agricultural area. Heterotrophic plate counts (HPCs) and quantitative polymerase chain reaction (qPCR) were performed for detection of selected antibiotic-resistant bacteria (ARB), selected antibiotic resistance genes (ARGs), intI1 genes, and 16S rRNA genes. Biosolid samples contained significantly higher levels of selected ARGs than the raw agricultural soils (p < 0.05). The average relative abundances of intI1, sul1, blaSHV, and ermB genes were significantly higher in biosolid-amended soils than nearby agricultural soils (p < 0.05). Spatial interpolation analysis of relative gene abundances of intI1, sul1, sul2, and tetW across the studied area further indicated directional trends towards the northwest and southeast directions, highlighting possible airborne spread. Concentrations of Co, Cu, Ni, and Fe were found to be significantly and positively correlated with relative abundances of intI1, sul1, and tetW genes (p < 0.05). The resistance ratios of culturable antibiotic-resistant bacteria in agricultural soils with biosolid amendments were generally identical to those without biosolid amendments. This study will advance the understanding of the antibiotic resistome in agricultural soils impacted by long-term waste reuse and inform the evaluation strategies for future biosolids application and management.

Accumulation of antibiotic resistance genes in pakchoi (Brassica chinensis L.) grown in chicken manure-fertilized soil amended with fresh and aged biochars.

Biochar has been used to alleviate the contamination of antibiotic resistance genes (ARGs) in soil and to inhibit ARGs transfer from soil to plants. However, the effect of aged biochar on ARGs abundance in soil and ARGs enrichment in plants are scarcely investigated. In this study, a pot experiment was conducted to compare the effects of fresh and aged biochars on the accumulation of five typical ARGs including tetX, tetW, sul2, ermB, and intI1 in a chicken manure-fertilized soil and in pakchoi (Brassica chinensis L.). Results showed that both biochars significantly decreased the abundance of tetW, sul2, and ermB and increased the abundance of tetX and intI1 in soil. However, the accumulation of all tested ARGs in pakchoi were significantly decreased by both biochars. At the lower addition rate (1%), the fresh biochar was superior to the aged biochar in decreasing the accumulation of some genes (tetW, tetX, and sul2) in pakchoi, whereas an opposite tendency was observed for other genes (ermB and intI1). As the addition rate increased to 2%, the difference between the two biochars diminished, and a similar capacity of decreasing ARGs transfer was observed. The reduction in ARGs accumulation in pakchoi was highly related to the type of ARGs, the biochar addition level, and the aging of biochar. Our results provide insights into the naturally aged biochar on the fate of ARGs in a soil-plant system.

Occurrence of veterinary drugs and resistance genes during anaerobic digestion of poultry and cattle manures

In the present paper, the mesophilic (35 °C) and thermophilic (55 °C) biomethanization of poultry and cattle manures were investigated using biochemical methane potential (BMP) tests. Specific methane production (SMP), 24 pharmaceutical compounds (PhACs), and five antibiotic resistance genes (ARGs) (blaKPC, ermB, qnrS, sul1 and tetW) together with the microbial community were analyzed. Mesophilic BMP tests resulted in the highest SMP when poultry manure was used (285.5 mL CH4/g VSS with poultry vs 239.6 mL CH4/g VSS with cattle manure) while thermophilic temperatures led to the highest SMP with cattle manure (231.2 mL CH4/g VSS with poultry vs 238.0 mL CH4/g VSS with cattle manure). Higher removals of veterinary pharmaceuticals were detected at 55 °C with both manures indicating that thermophilic digestion is better suited for the removal of these compounds. Tylosin, tilmicosin, chlortetracycline, and sulfamethoxazole presented removals higher than 50%, being the first two completely removed under mesophilic and thermophilic conditions. When comparing the relative abundance of ARGs at the end of each treatment, the most significant removal was found for qnrS which was not detected after the anaerobic treatment. The remaining ARGs did not suffer significant changes. Finally, microbial composition analysis showed that temperature affected the final microbial population more than the microorganisms present in the substrate or inoculum.

Comparison of Reference-Based Assembly and De Novo Assembly for Bacterial Plasmid Reconstruction and AMR Gene Localization in Salmonella enterica Serovar Schwarzengrund Isolates.

It is well established that plasmids carrying multiple antimicrobial resistance (AMR) genes can be easily transferred among bacterial isolates by horizontal gene transfer. Previous studies have shown that a combination of short- and long-read approaches is effective in reconstructing accurate plasmids. However, high-quality Illumina short reads mapped onto the long reads in the context of an AMR hybrid monitoring strategy have not yet been explored. Hence, this study aimed to improve the reconstruction of plasmids, including the localization of AMR genes, using the above-described parameters on whole-genome sequencing (WGS) results. To the best of our knowledge, this study is the first to use S1 nuclease pulsed-field gel electrophoresis (S1-PFGE) to confirm the number and sizes of plasmids detected by in silico-based predictions in Salmonella strains. Our results showed that de novo assembly did not detect the number of bacterial plasmids more accurately than reference-based assembly did. As this new hybrid mapping strategy surpassed de novo assembly in bacterial reconstruction, it was further used to identify the presence and genomic location of AMR genes among three Salmonella enterica serovar Schwarzengrund isolates. The AMR genes identified in the bacterial chromosome among the three Salmonella enterica serovar Schwarzengrund isolates included: AAC(3)-IV, AAC(6′)-Iy, aadA2, APH(4)-Ia, cmlA1, golS, mdsA, mdsB, mdsC, mdtK, qacH, sdiA, sul2, sul3, and TEM-1 genes. Moreover, the presence of TEM-1, AAC(3)-IV, aadA2, APH(4)-Ia, cmlA1, dfrA12, floR, sul1, sul3, and tet(A) genes found within three IncFIB plasmids and one IncX1 plasmid highlight their possible transmission into the environment, which is a public health risk. In conclusion, the generated data using this new hybrid mapping strategy will contribute to the improvement of AMR monitoring and support the risk assessment of AMR dissemination.

Variation in the microbial community in bioelectrochemical systems treating sulfamethoxazole wastewater — Identifying key operating parameters and revealing sul gene-harboring host bacteria

A biofilm electrode system (BES), which is the combination of a constructed wetland-microbial fuel cell (MFC-CW) with a biofilm electrode reactor (BER), was used to treat wastewater that contained sulfamethoxazole for three months. The variation in the microbial community, including the microbial diversity, was explored. Furthermore, the key operating factors were identified, and the sul genes-harboring host bacteria were revealed. The results demonstrated that the species richness in the BER was greater than in the MFC-CW, but the Shannon index was susceptible to the run time. The Beta diversity showed that the species composition similarity was primarily clustered according to the position of the BES and then according to the run time. In addition, the principal axis analysis showed that the species composition similarity of the MFC-CW was closer to that of the control sample. Both the BER and MFC-CW were significantly correlated with the voltage and SMX concentration (p < 0.01) at the same correlation level (0.25–0.5). There were 39 phyla during the entire operational period, and the top 9 were Proteobacteria, Bacteroidetes, Chloroflexi, Chlorobi, Acidobacteria, Firmicutes, Actinobacteria, Nitrospirae and Planctomysete. The potential host bacteria of the sul genes, such as Lentisphaerae, Firmicutes, Proteobacteria, and Fusobacteria in the BER and Chlorobi, Caldiserica, Nitrospirae, Actinobacteria, and Planctomycetes in the MFC-CW, were obtained using a Procrustes analysis.

Electrochemical flow-through disinfection reduces antibiotic resistance genes and horizontal transfer risk across bacterial species

Antibiotic resistant bacteria (ARB) and antibiotic resistance genes (ARGs), as emerging pollutants, are released into environment, increasing the risk of horizontal gene transfer (HGT). However, a limited number of studies quantified the effects of ARB disinfection on the HGT risk. This study investigated the inactivation of E. coli 10667 (sul) and the release and removal of ARGs using an electrochemical flow-through reactor (EFTR). Furthermore, the transfer frequencies and potential mechanisms of HGT after disinfection were explored using non-resistant E. coli GMCC 13373 as the recipient and E. coli DH5α carrying plasmid RP4 as the donor. A threshold of current density (0.25mA/cm2) was observed to destroy cells and release intracellular ARGs (iARGs) to increase extracellular ARGs (eARGs) concentration. The further increase in the current density to 1mA/cm2 resulted in the decline of eARGs concentration due to the higher degradation rate of eARGs than the release rate of iARGs. The performance of ARGs degradation and HGT frequency by EFTR were compared with those of conventional disinfection processes, including chlorination and ultraviolet radiation (UV). A higher ARGs degradation (83.46%) was observed by EFTR compared with that under chlorination (10.23%) and UV (27.07%). Accordingly, EFTR reduced the HGT frequency (0.69) of released ARGs into the recipient (Forward transfer), and the value was lower than that by chlorination (2.69) and UV (1.73). Meanwhile, the surviving injured E. coli 10667 (sul) with increased cell permeability was transferred by plasmid RP4 from the donor (Reverse transfer) with a higher frequency of 0.33 by EFTR compared with that under chlorination (0.26) and UV (0.16). In addition, the sul3 gene was the least resistant to EFTR than sul1 and sul2 gene. These findings provide important insights into the mechanism of HGT between the injured E. coli 10667 (sul) and environmental bacteria. EFTR is a promising disinfection technology for preventing the spread of antibiotic resistance.

Antimicrobial Susceptibility Profiles among Pseudomonas aeruginosa Isolated from Professional SCUBA Divers with Otitis Externa, Swimming Pools and the Ocean at a Diving Operation in South Africa.

SCUBA divers are predisposed to otitis externa caused by Pseudomonas aeruginosa, which is becoming increasingly multi-drug resistant (MDR). The present work assessed the antibiotic resistance profiles of P. aeruginosa obtained from SCUBA divers and their environment in Sodwana Bay, South Africa. Bacterial isolates from a total of 137 random water and ear swab samples were identified using biochemical and molecular methods. P. aeruginosa strains were further evaluated for antibiotic susceptibility using the Kirby–Bauer assay. Double disk synergy test (DDST) to confirm metallo-β-lactamase (MBL) production and PCR amplification of specific antibiotic resistance genes was performed. All (100%) 22 P. aeruginosa isolates recovered were resistant to 6 of the β-lactams tested including imipenem but exhibited susceptibility to trimethoprim–sulfamethoxazole. MBL production was observed in 77% of isolates while the most prevalent extended-spectrum β-lactamase (ESBL) genes present included blaAmpC (86.9%) followed by blaTEM (82.6%). Sulfonamide resistance was largely encoded by sul1 (63.6%) and sul2 (77.3%) genes with a high abundance of class 1 integrons (77.3%) of which 18.2% carried both Intl1 and Intl2. P. aeruginosa found in Sodwana Bay exhibits multi-drug resistance (MDRce) to several pharmaceutically important drugs with the potential to transfer antibiotic resistance to other bacteria if the judicious use of antibiotics for their treatment is not practiced.

Relationship between water quality, heavy metals and antibiotic resistance genes among three freshwater lakes.

Urban recreational lakes are impacted by consistent anthropogenic activities and are significant sources of heavy metals and antibiotic resistance genes (ARGs). In this study, three urban lakes of varying size and anthropogenic impact in Nanjing, China, were investigated for the abundance of ten ARGs, six physicochemical factors and four heavy metals. Correlations between heavy metals and physicochemical parameters against ARGs were performed to investigate the presence of ARGs in the lakes. The water quality data indicated that the lakes were on par with levels 3 and 4 of the Chinese surface water environmental standards, signifying disturbing pollution levels in the lakes. The lakes were dominant with high amounts of sul1, sul2 and strA genes, and the sum of these three genes appropriated over 38.9-84.4% in all three lakes, while the sum of tetM, tetQ and ermB genes occupied a minor proportion (0.1-1.4%). High levels of vancomycin resistance genes were found in the three lakes. Spearman analysis indicated that Chlα, cadmium, lead and copper had a significant positive correlation with sul2 and strB. The results of redundancy analysis displayed that Chlα and co-selection with certain heavy metals were the major factors driving the propagation of specific genes in three lakes. We believe our study contributes by adding further knowledge to existing antibiotic resistance gene abundance studies in recreational urban lakes with significant anthropogenic impacts.

Genomic Characterization of Carbapenem-Non-susceptible Pseudomonas aeruginosa Clinical Isolates From Saudi Arabia Revealed a Global Dissemination of GES-5-Producing ST235 and VIM-2-Producing ST233 Sub-Lineages.

Carbapenem-resistant P. aeruginosa has become a major clinical problem due to limited treatment options. However, studies assessing the trends in the molecular epidemiology and mechanisms of antibiotic resistance in this pathogen are lacking in Saudi Arabia. Here, we reported the genome characterization in a global context of carbapenem non-susceptible clinical isolates from a nationally representative survey. The antibiotic resistance profiles of the isolates (n = 635) collected over 14 months between March 2018 and April 2019 from different geographical regions of Saudi Arabia showed resistance rates to relevant β-lactams, aminoglycosides and quinolones ranging between 6.93 and 27.56%. Overall, 22.52% (143/635) of the isolates exhibited resistance to both imipenem and meropenem that were mainly explained by porin loss and efflux overexpression. However, 18.18% of resistant isolates harbored genes encoding GES (69.23%), VIM (23.07%), NDM (3.85%) or OXA-48-like (3.85%) carbapenemases. Most common GES-positive isolates produced GESs −5, −15 or −1 and all belonged to ST235 whereas the VIM-positive isolates produced mainly VIM-2 and belonged to ST233 or ST257. GES and VIM producers were detected at different sampling periods and in different surveyed regions. Interestingly, a genome-wide comparison revealed that the GES-positive ST235 and VIM-2-positive ST233 genomes sequenced in this study and those available through public databases from various locations worldwide, constituted each a phylogenetically closely related sub-lineage. Profiles of virulence determinants, antimicrobial resistance genes and associated mobile elements confirmed relatedness within each of these two different sub-lineages. Sequence analysis located the blaGES gene in nearly all studied genomes (95.4%) in the same integrative conjugative element that also harbored the acc(6′)-Ib, aph(3′)-XV, aadA6, sul1, tet(G), and catB resistance genes while blaVIM–2 in most (98.89%) ST233-positive genomes was co-located with aac(6′)-I1, dfrB-5, and aac(3′)-Id in the same class I integron. The study findings revealed the global spread of GES-5 ST235 and VIM-2 ST233 sub-lineages and highlighted the importance of routine detection of rare β-lactamases.

Sulfonamides repress cell division in the root apical meristem by inhibiting folates synthesis

Sulfonamides, as broad-spectrum antibiotics, are widely used to protect against bacterial infections in livestock production. A large number of sulfa antibiotics are discharged into soil and water system, which poses a great threat to the safety of organisms. The antibacterial mechanism of sulfonamides is to prevent folate biosynthesis by competitively inhibiting bacterial dihydropteroate synthetase (DHPS). The inhibitory effect of sulfanilamide on root growth has been reported, but the mechanism has not been determined. Here, we used high performance liquid chromatography with ultraviolet detector (HPLC-UV) and transgenic technology to study the effect of sulfonamides on folate synthesis in plants. The results showed that the application of sulfonamide sharply reduced the content of folic acid in plants, resulting in strong inhibition of cell division in the root apical meristem. The inhibition of sulfonamide on cell division can be relieved by supplementing synthetic folic acid and folinic calcium salt hydrate. The transgenic plants expressing the bacterial antibiotic resistance genes (ARGs) Sul1 or Sul2 showed obvious antibiotic resistance. Taking these results together, we suggest that sulfonamides repress cell proliferation in the root apical meristem by competitively inhibiting the biosynthesis of folic acid in plants.

Escherichia coli ST471 Producing VIM-4 Metallo-β-Lactamase in Colombia.

An Escherichia coli isolate sequence-type 471 (ST471) producing Verona integron-encoded metallo-β-lactamases (VIM)-4 was recovered from a rectal swab in a patient without travel records with osteomyelitis in Colombia. The isolate carried a class 1 integron-borne blaVIM-4 gene with a 170-bp duplication in the 3′ end of the gene, preceded by an aac(6′)-Ib gene. The genetic environment of blaVIM-4, blaCMY-2, and sul2 genes showed similarities to the backbone of pKKp4, an IncA/C-type plasmid from a Klebsiella pneumoniae strain carrying blaVIM-4 recovered in Kuwait. This is the first report of blaVIM-4 in Enterobacterales in South America. Our results suggest that blaVIM-4 gene was found on an IncA/C-type plasmid that could play a role in the spread of VIM-4 carbapenemase in Colombia.

Occurrence and distribution of antibiotics and antibiotic resistance genes in the guts of shrimp from different coastal areas of China

With the continuous increase in shrimp (Litopenaeus vannamei) aquaculture production, the widespread use of antibiotics as a means of preventing and treating diseases has adversely affected the environment, animal health and symbiotic microorganisms in gut environments. At the same time, antibiotic resistance genes (ARGs) are widespread in aquaculture and pose a great threat to aquatic organisms and humans. Therefore, in the present study, the occurrence and distribution of 17 antibiotics, ARGs and mobile genetic elements (MGEs) were detected in the guts of shrimp collected from 12 coastal regions of China. The results showed that sulfadiazine, ciprofloxacin and norfloxacin were detectable in the guts of L. vannamei at all sampling sites. Sul1, sul2, floR and intI-1 were also detected in the guts of L. vannamei at all sampling sites. The total relative abundances of ARGs and MGEs were significantly positively correlated according to Pearson correlation analysis. Sulfonamide resistance genes (sul1 and sul2) were significantly positively correlated with intI-1. These results indicated that MGEs could increase the risk of horizontal gene transfer of ARGs in a gut environment. MGEs are the most important factors promoting the spread of ARGs. Correlation analysis showed that sulfadiazine was significantly positively correlated with sul1 and sul2 and that fluoroquinolone antibiotics were significantly positively correlated with floR, indicating that antibiotics could induce the production of ARGs. Network analysis indicated that Iamia and Alkaliphilus species may harbor the most antibiotic resistance genes, and these bacteria were closely related to the proliferation and spread of ARGs in a gut environment. Antibiotic use and the spread of ARGs in mariculture systems may have negative effects on shrimp and human health. The use of antibiotics should be strictly regulated to control contaminants in mariculture systems, including pathogens and ARGs, thereby reducing potential risks to human health.

Prevalence and antibiotic resistance profiles of Salmonella spp. in chicken meat

This study aimed to determine the Salmonella spp. presence in 100 chicken meat samples (25 breasts and 25 drumsticks with skin and 25 breasts and 25 drumsticks without skin) that were collected between February and April, 2021, in Van, Türkiye and investigate the antibiotic resistance profiles of the isolates. The results of the cultivation and PCR analysis revealed that a total of 17 samples comprising four drumstick with skin (16%), five drumstick without skin and breast without skin (20%), and three breast with skin (12%) samples were positive for Salmonella spp. The analysis of 17 chicken meat samples yielded a total of 33 Salmonella spp. isolates. S. Enteritidis and S. Typhimurium were not detected in the serotyping of Salmonella isolates using PCR. According to the disc diffusion test, the isolates were resistant to amoxicillin/clavulanic acid and streptomycin (33.33%), ampicillin (36.36%), gentamicin and ceftriaxone (24.24%), chloramphenicol (42.42%), cefotaxime (12.12%), tetracycline (30.30%), and trimethoprim-sulfamethoxazole (81.82%). The isolates were intermediately resistant to streptomycin (18.18%) and tetracycline (9.09%). PCR analysis for the detection of resistance genes revealed that 77.78% and 62.96% of the trimethoprim-sulfamethoxazole-resistant isolates harbored sul1 and sul2 genes, respectively. The pse-1 gene was detected in 66.67% of the ampicillin-resistant isolates while the tetA and tetB genes were detected in 20% and 10% of the tetracycline-resistant isolates, respectively. The ant(3")-la gene was detected in all (100%) gentamicin-resistant isolates. In conclusion, the absence of S. Typhimurium and S. Enteritidis in the Salmonella spp. isolates from the chicken meats that were obtained from the Van market indicated the compliance of the products with the Turkish Food Codex while the presence of Salmonella spp. indicated the poor hygienic quality of the meats. The high antimicrobial resistance of the isolates and the presence of the resistance genes can result in the transmission of resistant species to humans, which may require complicated treatments and cause the emergence of a serious public health issue.

Emergence of extensively drug-resistant Aeromonas hydrophila complex isolated from wild Mugil cephalus (striped mullet) and Mediterranean seawater.

Background and Aim:Antibiotic resistance has been a progressively documented problem, resulting in treatment failure in humans and animals. This study aimed to investigate the antimicrobial susceptibility and virulence of extensively drug-resistant (XDR) Aeromonas spp. in wild Mugil cephalus and its surrounding seawater along the coastal road of Port Said, Egypt.Materials and Methods:Specimens were examined bacteriologically, confirmed biochemically, and tested for their sensitivity against 11 antimicrobial agents. Molecular confirmation of the obtained isolates by 16S rRNA was performed, followed by the detection of antimicrobial resistance and virulence genes.Results:Aeromonas spp. was recovered from fish (44%) and water samples (36%). A. hydrophila was the most prevalent identified strain, followed by Aeromonas sobria, Aeromonas caviae, and Aeromonas schubertii. Moreover, 90% of the tested isolates were multidrug-resistant (MDR), while 26.67% were XDR. Tested isolates were resistant to b-lactams and sulfonamides (100%), oxytetracycline (90%), and streptomycin (62.22%) but completely susceptible to cefotaxime. XDR isolates successfully amplified resistance genes (blaTEM , sul1, and tetA(A)) but not the (aadA1) gene, although there was phenotypic resistance to streptomycin on plates. All XDR isolates carry the cytotoxic enterotoxin gene (act), but alt gene was detected in only one isolate (12.5%).Conclusion:Data in this study provide a recent update and highlight the role of wild mullet and seawater as reservoirs for MDR and XDR Aeromonas spp. that may pose a risk to humans as food-borne infection or following direct contact.

Intervention of antimicrobial peptide usage on antimicrobial resistance in aquaculture

Antibiotic resistance genes (ARGs) widely exist in diverse matrices to pose potential risks and attract global attention. This study performed tilapia-cultivation experiment to discuss the intervention of antimicrobial peptide usage on antimicrobial resistance in aquaculture by analyzing 29 target ARGs in water, residue, and fish muscle samples. The sul1 gene was the dominant ARG in most of samples while absolute abundances of total ARGs were in the range of 1.5 × 102-2.3 × 107 copies/mL in water samples and 2.1 × 108-3.9 × 109 copies/g in the residue and fish muscle samples. Compared with antibiotic treatment, the cecropin treatment could significantly reduce the absolute abundance of ARGs and intI1 in all samples. Proteobacteria were the dominant phylum for most of samples while Aeromonas/Cetobacterium served as the dominant genus for samples with antibiotic/cecropin treatment. Network analysis showed that cecropin treatment could significantly reduce occurrence of multi-drug resistant bacteria and the correlation between genera and ARGs. Results of partial least squares structural equation modeling which was used to discuss the influential factors of ARGs exhibited that antibiotics could increase ARGs, further proving that cecropin peptide could effectively reduce ARGs in aquaculture. This study will provide important information on controlling ARGs in aquaculture in terms of antimicrobial peptide application.

Robustness of the partial nitrification-anammox system exposing to triclosan wastewater: Stress relieved by extracellular polymeric substances and resistance genes

The partial nitrification-anammox (PN/A) process is a promising method for the treatment of municipal wastewater. It is necessary to clarify the responses of PN/A system to antimicrobial agent triclosan (TCS) widely existed in the influent of wastewater treatment plants. In this study, it was found that PN/A system was robust to cope with 0.5 mg/L TCS. Specifically, the control reactor reached 80% total nitrogen removal efficiency (TNRE) on day 107, while the reactor feeding with 0.5 mg/L TCS reached the same TNRE on day 84. The results of the activity test, high-throughput sequencing and DNA-based stable isotope probing showed that 0.5 mg/L TCS did not impede the performance of ammonia oxidizing archaea, ammonia oxidizing bacteria (Nitrosomonas) and anammox bacteria (Candidatus Brocadia and Ca. Kuenenia), but significant inhibited the nitrite oxidizing bacteria (Nitrospira and Ca. Nitrotoga) and denitrifying bacteria. The influent TCS led to the increase of EPS content and enrichment of four resistance genes (RGs) (intI1, sul1, mexB, and tnpA), which might be two principal mechanisms by which PN/A can resist TCS. In addition, functional bacteria carrying multiple RGs also contributed to the maintenance of PN/A system function. These findings improved the understandings of antimicrobial effects on the PN/A system.

Migratory wild birds carrying multidrug-resistant Escherichia coli as potential transmitters of antimicrobial resistance in China.

Migratory birds play an important role in the spread of multidrug-resistant (MDR) bacteria. To investigate the prevalence of MDR Escherichia coli in migratory birds in China and potential relationships with the environment, a total of 1387 samples (fecal samples, cloacal swabs, or throat swabs) were collected from migratory birds from three different river basins in China. The collected samples were processed and subjected to bacteriological examinations. Antimicrobial susceptibility testing of the recovered isolates was performed using the E-test for the detection of minimum inhibitory concentrations (MICs). Some antibiotic resistance genes were detected and the PCR products were confirmed by sequencing. In total, 478 (34.7%) E. coli isolates were recovered. The results showed that the drug-resistant E. coli isolates were highly resistant to β-lactams (43.7%) and tetracycline (22.6%), and 73 (15.3%) were MDR, including eight that were extended spectrum β-lactamase-positive. The retrieved strains harbored the blaCTX-M, blaTEM-1, tet(A), tet(B), tet(M), sul1, sul2, sul3, cmlA, floR, and intI1 genes with a prevalence of 5.9%, 36.4%, 80.5%, 11.9%, 6.8%, 6.8%, 47.5%, 12.7%, 50.8%, 37.3%, and 61.0%, respectively. The drug resistance rate of the isolates from southern China was higher than those from northern China. The E. coli samples collected for migratory birds in the Pearl River Basin had the highest proportion (46.7%) MDR isolates. Furthermore, MDR bacteria carried by migratory birds were closely related to the antibiotic content in the basin, which confirms that MDR bacteria carried by migratory birds are likely acquired from the environment. This study also confirmed that migratory birds are potential transmitters of MDR bacteria, demonstrating the need to reduce the use and emission of antibiotics and further in-depth studies on the mechanisms underlying drug resistance of bacteria.