Exploring the Role of Coliform Bacteria in Class 1 Integron Carriage and Biofilm Formation During Drinking Water Treatment

Hospital wastewater as source of human pathogenic bacteria: A phenotypic and genomic analysis of international high-risk clone VIM-2-producing Pseudomonas aeruginosa ST235/O11

Pseudomonas aeruginosa belong to the special pathogen group capable of causing serious infections, with high mortality rates. The aim of this study was to describe the antibiotic resistance and genomic characteristics of Pseudomonas aeruginosa belonging to international high-risk clone ST235 (GPAE0131 isolate), obtained from hospital wastewater. P. aeruginosa GPAE0131 was isolated from ward tertiary hospital in Brazil and the antibiotic resistance profile was determined by the disc-diffusion method. Genomic characteristics related to antibiotic resistance and virulence factors were evaluated by genomic DNA sequencing on the Illumina MiSeq platform and bioinformatic analysis. GPAE0131 isolate showed resistance to piperacillin-tazobactam, cefepime, ceftazidime, imipenem, meropenem, ciprofloxacin, levofloxacin and tobramycin. Resistome comprehend of resistance genes to β-lactams (blaVIM-2, blaOXA-4, blaOXA-488, blaPDC-35), aminoglycosides (aph(3')-IIb, aac(6')-IIc, aac(6')-Ib9, aadA1), fosfomycin (fosA), chloramphenicol (catB7) and sulfonamides (sul1). Genome comparisons evidence insertion of blaVIM-2 and blaOXA-4 genes. GPAE0131 isolate was predicted to be pathogenic to humans and several virulence factors were found, including encoding gene for ExoU and exotoxin A. All of these features into a pathogenic international high-risk clone (ST235), classified as critical priority, stands out as public health concern due to the widespread dispersal of human pathogens through wastewater. It is suggested that mitigating measures be implemented, such as the treatment of hospital sewage and the addition of tertiary treatment, to prevent the escape of pathogens at this level into the environment.

Accessing the In Vivo Efficiency of Clinically Isolated Phages against Uropathogenic and Invasive Biofilm-Forming Escherichia coli Strains for Phage Therapy

Escherichia coli is one of the most common members of the intestinal microbiota. Many of its strains are associated with various inflammatory infections, including urinary or gut infections, especially when displaying antibiotic resistance or in patients with suppressed immune systems. According to recent reports, the biofilm-forming potential of E. coli is a crucial factor for its increased resistance against antibiotics. To overcome the limitations of using antibiotics against resistant E. coli strains, the world is turning once more towards bacteriophage therapy, which is becoming a promising candidate amongst the current personalized approaches to target different bacterial infections. Although matured and persistent biofilms pose a serious challenge to phage therapy, they can still become an effective alternative to antibiotic treatment. Here, we assess the efficiency of clinically isolated phages in phage therapy against representative clinical uropathogenic and invasive biofilm-forming E. coli strains. Our results demonstrate that irrespective of host specificity, bacteriophages producing clear plaques with a high burst size, and exhibiting depolymerizing activity, are good candidates against biofilm-producing E. coli pathogens as verified from our in vitro and in vivo experiments using Galleria mellonella where survival was significantly increased for phage-therapy-treated larvae.

Molecular Typing Reveals Environmental Dispersion of Antibiotic-Resistant Enterococci under Anthropogenic Pressure

As a consequence of global demographic challenges, both the artificial and the natural environment are increasingly impacted by contaminants of emerging concern, such as bacterial pathogens and their antibiotic resistance genes (ARGs). The aim of this study was to determine the extent to which anthropogenic contamination contributes to the spread of antibiotic resistant enterococci in aquatic compartments and to explore genetic relationships among Enterococcus strains. Antimicrobial susceptibility testing (ampicillin, imipenem, norfloxacin, gentamycin, vancomycin, erythromycin, tetracycline, trimethoprim-sulfamethoxazole) of 574 isolates showed different rates of phenotypic resistance in bacteria from wastewaters (91.9–94.4%), hospital effluents (73.9%), surface waters (8.2–55.3%) and groundwater (35.1–59.1%). The level of multidrug resistance reached 44.6% in enterococci from hospital effluents. In all samples, except for hospital sewage, the predominant species were E. faecium and E. faecalis. In addition, E. avium, E. durans, E. gallinarum, E. aquimarinus and E. casseliflavus were identified. Enterococcus faecium strains carried the greatest variety of ARGs (bla_TEM-1, aac(6′)-Ie-aph(2″), aac(6′)-Im, vanA, vanB, ermB, mefA, tetB, tetC, tetL, tetM, sul1), while E. avium displayed the highest ARG frequency. Molecular typing using the ERIC2 primer revealed substantial genetic heterogeneity, but also clusters of enterococci from different aquatic compartments. Enterococcal migration under anthropogenic pressure leads to the dispersion of clinically relevant strains into the natural environment and water resources. In conclusion, ERIC-PCR fingerprinting in conjunction with ARG profiling is a useful tool for the molecular typing of clinical and environmental Enterococcus species. These results underline the need of safeguarding water quality as a strategy to limit the expansion and progression of the impending antibiotic-resistance crisis.

Antibiotic Resistance in Pseudomonas spp. Through the Urban Water Cycle

Selection and dissemination of resistant bacteria and antibiotic resistance genes (ARGs) require a deeper understanding since antibiotics are permanently released to the environment. The objective of this paper was to evaluate the phenotypic resistance of 499 isolates of Pseudomonas spp. from urban water sources, and the prevalence of 20 ARGs within those isolates. Resistance to penicillins, cephalosporins, carbapenems, quinolones, macrolides, and tetracyclines was mainly observed in the hospital effluent, municipal wastewater and river water downstream the city. Resistant strains were frequently identified as P. aeruginosa and P. putida. P. aeruginosa isolates were mostly resistant to cefepime, ceftazidime, imipenem, and gentamycin, while P. putida strains were especially resistant to piperacillin-tazobactam. ARGs such as bla_TEM-1, bla_SHV-1, bla_PER-1, bla_AmpC, bla_VIM-1, PstS, qnrA, qnrB, ermB, tetA, tetB and tetC have been detected. The bla_AmpC gene was found in P. aeruginosa, while bla_TEM-1 and bla_PER-1 genes were found in P. putida. Class 1 integron integrase gene was found in 6.81% of the Pseudomonas isolates.

Loss of Function in Escherichia coli Exposed to Environmentally Relevant Concentrations of Benzalkonium Chloride

Assessing the risk of resistance associated with biocide exposure commonly involves exposing microorganisms to biocides at concentrations close to the MIC. With the aim of representing exposure to environmental biocide residues, Escherichia coli MG1655 was grown for 20 passages in the presence or absence of benzalkonium chloride (BAC) at 100 ng/liter and 1,000 ng/liter (0.0002% and 0.002% of the MIC, respectively). BAC susceptibility, planktonic growth rates, motility, and biofilm formation were assessed, and differentially expressed genes were determined via transcriptome sequencing. Planktonic growth rate and biofilm formation were significantly reduced (P < 0.001) following BAC adaptation, while BAC minimum bactericidal concentration increased 2-fold. Transcriptomic analysis identified 289 upregulated and 391 downregulated genes after long-term BAC adaptation compared with the respective control organism passaged in BAC-free medium. When the BAC-adapted bacterium was grown in BAC-free medium, 1,052 genes were upregulated and 753 were downregulated. Repeated passage solely in biocide-free medium resulted in 460 upregulated and 476 downregulated genes compared with unexposed bacteria. Long-term exposure to environmentally relevant BAC concentrations increased the expression of genes associated with efflux and reduced the expression of genes associated with outer-membrane porins, motility, and chemotaxis. This was manifested phenotypically through the loss of function (motility). Repeated passage in a BAC-free environment resulted in the upregulation of multiple respiration-associated genes, which was reflected by increased growth rate. In summary, repeated exposure of E. coli to BAC residues resulted in significant alterations in global gene expression that were associated with minor decreases in biocide susceptibility, reductions in growth rate and biofilm formation, and loss of motility.IMPORTANCE Exposure to very low concentrations of biocides in the environment is a poorly understood risk factor for antimicrobial resistance. Repeated exposure to trace levels of the biocide benzalkonium chloride (BAC) resulted in loss of function (motility) and a general reduction in bacterial fitness but relatively minor decreases in susceptibility. These changes were accompanied by widespread changes in the Escherichia coli transcriptome. These results demonstrate the importance of including phenotypic characterization in studies designed to assess the risks of biocide exposure.

Occurrence and distribution of antibiotic resistance genes in the sediments of drinking water sources, urban rivers, and coastal areas in Zhuhai, China

Antibiotic resistance genes (ARGs) are regarded as emerging contaminants related with human activities. Aquatic environments of an urban city are apt for the persistence and prevalence of ARGs. In this study, we investigated the occurrence and distribution of ARGs and integrase genes in the sediment samples collected from drinking water sources, urban rivers, and coastal areas of Zhuhai, China, in the dry and wet seasons of 2016. The results show that sulfonamide resistance gene of sulII was present at the highest detection frequency (85.71%); and its average concentrations were also the highest in both dry and wet seasons (3.78 × 10⁷ and 9.04 × 10⁷ copies/g sediment, respectively), followed by tetC, tetO, tetA, ermB, dfrA1, and bla_PSE-1. Temporally, the concentrations of total ARGs in the wet season were likely higher than those in the dry season; and spatially, the concentrations of total ARGs in the drinking water sources were substantially lower than those in the urban rivers and nearby coastal areas, indicating the different degrees of anthropogenic impact and consequent health risks. Positive correlations were found between intI1 and each quantitative ARG in all wet season samples rather than dry season samples, which suggested higher temperature and more rain in summer might have positive influences on ARG dissemination, especially that mediated by intI1 gene and class I integrons.

Biofilm Formation Plays a Role in the Formation of Multidrug-Resistant Escherichia coli Toward Nutrients in Microcosm Experiments

In this study, microcosms were established to determine the effect of nitrogen (N) and phosphorus (P) on the multidrug resistance and biofilm-forming abilities of Escherichia coli. The expression of biofilm-formation-related genes was detected to establish correlations between genotype and phenotype. Different concentrations of N and P were added to make one control group and four treatment groups. The glass tube method was used to determine biofilm-forming capabilities. Real-time PCR was used to detect the mRNA abundance of six biofilm-formation-related genes in E. coli. No resistant strains were isolated from the control group; meanwhile, multidrug resistance rates were high in the treatment groups. Expression of the biofilm-associated genes luxS, flhD, fliA, motA, and fimH was detected in all treatment groups; however, there was no expression of mqsR. The expression of luxS, flhD, fliA, motA, and fimH significantly correlated with the concentration of N and P, as well as with the appearance and duration of multidrug resistance in different groups. Overall, the results of this study suggest that biofilm-forming ability plays a key role in the formation of multidrug resistance in E. coli after the addition of N and P to a microcosm.

Examination of Quaternary Ammonium Compound Resistance in Proteus mirabilis Isolated from Cooked Meat Products in China

The aim of this study was to examine the presence of genes responsible for resistance to quaternary ammonium compounds (QACs) and the association of qac genes with class 1 integrons in Proteus mirabilis isolated from cooked meat products. A total of 52 P. mirabilis isolates (29.2%) were detected from 178 samples, and their minimum inhibitory concentrations (MICs) of benzalkonium chloride (BC) ranged from 4 to >32 μg/mL. The isolates with BC MICs of 24 μg/mL were observed most frequently. PCR assays indicated that mdfA, ydgE/ydgF, qacE, qacEΔ1, emrE, sugE(c), and sugE(p) were commonly present (32.7%-100%) in these isolates, but qacH was less prevalent (3.8%). Five groups of resistance gene cassettes were identified in 10 intI1-positive isolates. An unusual gene cassette array dfrA32-ereA-aadA2 was found in one foodborne isolate of P. mirabilis. Two isolates harbored qacH- and sul3- associated non-classic integrons: aadA2-cmlA1-aadA1-qacH-IS440-sul3 and a new arrangement dfrA32-ereA1-aadA2-cmlA1-aadA1-qacH-IS440-sul3, which is first reported in P. mirabilis. Non-classic class 1 integrons were located on conjugative plasmids of 100 kb in two tested isolates. Our data showed that the QAC resistance genes were commonly present among P. mirabilis isolates from cooked meats and qacH was associated with non-classic class 1 integrons. The creation of transconjugants demonstrated that qacH-associated non-classic class 1 integrons were located on conjugative plasmids and therefore could facilitate the co-dissemination of disinfectant and antimicrobial resistance genes among bacteria, an increasing area of concern.

Microbiological Impact of the Use of Reclaimed Wastewater in Recreational Parks

Reclaimed wastewater for irrigation is an opportunity for recovery of this natural resource. In this study, microbial risk from the use of treated wastewater for irrigation of recreational parks in the city of Chihuahua, evaluating the effect of distribution distance, season, and presence of storage tanks, was analyzed. Escherichia coli, Salmonella, and multidrug-resistant bacteria were recovered from samples of reclaimed water and soils at recreational parks in Chihuahua by the membrane filtration method, using selected agars for microbial growth. Samples were taken at three different seasons. No correlation in the presence of microbial indicators and multidrug-resistant bacteria (p > 0.05) was found between the distance from the wastewater treatment plant to the point of use. Presence of storage tanks in parks showed a significant effect (p < 0.05) with a higher level of E. coli. The highest count in wastewater occurred in summer. We isolated 392 multidrug-resistant bacteria from water and soil; cluster analysis showed that the microorganisms at each location were of different origins. Irrigation with reclaimed wastewater did not have a negative effect on the presence of microbial indicators of the quality of soils in the parks. However, the prevalence of multidrug-resistant bacteria still represents a potential risk factor for human health.

Characterization and horizontal transfer of qacH-associated class 1 integrons in Escherichia coli isolated from retail meats

The aim of this study was to examine the presence of genes responsible for resistance to quaternary ammonium compounds (QACs) and the association of qac genes with class 1 integrons in Escherichia coli isolated from retail meats. Among the 179 E. coli isolates tested, the minimum inhibitory concentrations (MICs) of benzalkonium chloride (BC) ranged from 4 to 64μg/mL. PCR assays indicated that QAC-resistance genes sugE(c), ydgE/ydgF, mdfA, emrE and qacEΔ1 were commonly present (40.2%-88.3%) in these isolates, but qacE, qacF, qacH and sugE(p) were less prevalent (2.2%-28.5%). Seven different gene cassette arrangements were identified in 31 intI1-positive isolates. Three types of qacH-sul3-associated non-classic integrons were observed in four isolates: dfrA12-orfF-aadA2-cmlA1-aadA1-qacH-IS440-sul3, aadA2-cmlA1-aadA1-qacH-IS440-sul3 and dfrA1-aadA1-qacH-IS440-sul3. Non-classic class 1 integrons were located on plasmids of 100-150kb in these four isolates. Our results demonstrated that the qacH-associated integrons located on 100 kb plasmids in two isolates could be transferred to an E. coli recipient, indicating the co-existence and co-dissemination of disinfectant and antimicrobial resistance genes among bacterial species.