Target Antibiotic-resistant Bacteria Research Articles

Efficient removal for antibiotic-resistant Escherichia coli and antibiotic resistance genes from aquatic environment by BiOCl supported Ag quantum dots

Due to the abuse and difficult removal of antibiotics, how to remove antibiotic resistant bacteria (ARB) and antibiotic resistant genes (ARGs) in the environment is facing significant challenges. A series of efficient and non-toxic photocatalytic technologies have been proposed to solve the problem of antibiotic resistance (AR) in wastewater. However, there is limited information on changes in cell behavior and characteristics during photocatalytic processing. In this study, the prepared BiOCl loaded with silver quantum dots was used to treat ARB and ARGs in water, and the physiological characteristics of ARB after photocatalytic treatment were discussed. Using tetracycline (Tet)-resistant and ampicillin (Amp)-resistant Escherichia coli (Tet-E. coli, Amp-E. coli) as target antibiotic resistant bacteria, and using Tet-resistant genes (Tet-RGs) and Amp-resistant genes(Amp-RGs) as target resistance genes, the effects of photocatalyst dosage and silver quantum dot content on photocatalytic performance were studied under UV 365 nm irradiation. The results showed that the optimal inactivation effect was achieved by Ag QDs(500)-BiOCl at a concentration of 300 mg/L, which were 6.91 lg (tet-resistant bacteria) and 6.83 lg (amp-resistant bacteria), respectively. The plasmon resonance effect between the supported silver quantum dots and BiOCl results in the generation of free radicals dominated by holes (h+) and superoxide anions (O2•-) in the system. ARB in the system will be attacked by free radicals, and the permeability of cell membrane gradually increases. For the purpose of protection, the oxidative stress system of cells will first increase the activity of intracellular antioxidant enzymes. Due to the increase of free radicals, antioxidant enzymes gradually become inactive, ultimately leading to cell inactivation. At the same time, after photocatalytic treatment, the absolute abundance of the target resistance gene decreased by 2.79 (tetA) and 3.92 (ampC) lg. Correlation analysis found that inactivation of ARB contributes to the removal of ARGs in the system.

Design, synthesis and evaluation of halogenated phenazine antibacterial prodrugs targeting nitroreductase enzymes for activation.

It is of great importance to develop new strategies to combat antibiotic resistance. Our lab has discovered halogenated phenazine (HP) analogues that are highly active against multidrug-resistant bacterial pathogens. Here, we report the design, synthesis, and study of a new series of nitroarene-based HP prodrugs that leverage intracellular nitroreductase (NTR) enzymes for activation and subsequent release of active HP agents. Our goals of developing HP prodrugs are to (1) mitigate off-target metal chelation (potential toxicity), (2) possess motifs to facilitate intracellular, bacterial-specific HP release, (3) improve water solubility, and (4) prevent undesirable metabolism (e.g., glucuronidation of HP's phenol). Following the synthesis of HP-nitroarene prodrugs bearing a sulfonate ester linker, NTR-promoted release experiments demonstrated prodrug HP-1-N released 70.1% of parent HP-1 after 16 hours (with only 6.8% HP-1 release without NTR). In analogous in vitro experiments, no HP release was observed for control sulfonate ester compounds lacking the critical nitro group. When compared to parent HP compounds, nitroarene prodrugs evaluated during these studies demonstrate similar antibacterial activities in MIC and zone of inhibition assays (against lab strains and clinical isolates). In conclusion, HP-nitroarene prodrugs could provide a future avenue to develop potent agents that target antibiotic resistant bacteria.

Management of Chronic Bacterial Prostatitis.

We conducted a review of the literature describing the most up-to-date diagnosis and treatment options of chronic bacterial prostatitis. Recurrence after oral antimicrobial therapy is common, due in part to the rising rates of antimicrobial resistance and inability to completely clear the offending bacteria from the prostate following prostatitis. Recent literature has described various treatment options for chronic bacterial prostatitis refractory to conventional antimicrobial agents, including the use of alternative agents such as fosfomycin, direct antimicrobial injections into the prostate, surgical removal of infected prostatic tissue, chronic oral antibiotic suppression, and an emerging novel therapy utilizing bacteriophages to target antibiotic resistant bacteria. Management of chronic bacterial prostatitis, especially recurrence after oral antimicrobial treatment, remains challenging. This review highlights an urgent need for further evidence assessing the efficacy and safety of treatment modalities for chronic bacterial prostatitis refractory to conventional oral antimicrobials.

Interaction of Sewage Bacteria with Heavy Metals, Antibiotics and Plants

Environment pollution of toxic heavy metals and antibiotics is widespread due of massive industrialization and overuse of antibiotics. Moreover, metal contamination can function as a selective agent in the spread of antibiotic resistance, affecting both animals and plant species. Isolation, identification and characterization of three heavy metal resistant bacterial strains from sewage pipes of Lahore city was carried out in this study. On the basis of morphology and 16S ribosomal RNA (rRNA) gene sequencing, the isolates were identified as Escherichia coli strain MHR-1, Bacillus subtilis strain MHR-2, Exiguobacterium aurantiacum strain MHR-3. These isolates were resistant to Cadmium (Cd) at (< 100 µg/mL), Chromium (Cr) (< 500 µg/mL), Lead (Pb) (< 400 µg/mL) and Arsenic (As) (< 200 µg/mL). Moreover, the isolates tolerated a combined stress of 50 µg/mL for all the heavy metals tested. Antibiotic susceptibility of the bacteria towards the 9 antibiotics revealed: MHR-1 was resistant to 66%, intermediate to 12% and susceptible to 22%; MHR-2 was resistant 66%, intermediate to 22% and susceptible to 12%; MHR-3 was resistant to 22%, intermediate to 33% and susceptible to 45%. For antibiotic-heavy metal co-stress, about 78% of antibiotics showed synergistic effects while 11% showed antagonistic effects along with a stress of 50 µg/mL of all heavy metals tested. Test of isolates for their ability to affect seed growth with and without heavy metal stress, showed no significant interaction with plants to tolerate the heavy metal stress. This study proposes an effective approach to target antibiotic resistant bacteria with combine stress of heavy metals, and further investigation will lead in to better insight in devising an effective treatment for targeting resistant pathogens. Key Words: , , , , .

Weak acids as an alternative anti-microbial therapy

Weak acids such as acetic acid and N-acetyl cysteine (NAC) at pH less than their pKa can effectively eradicate biofilms due to their ability to penetrate the biofilm matrix and the cell membrane. However, the optimum conditions for their activity against drug resistant strains, and safety, need to be understood for their application to treat infections or to inactivate biofilms on hard surfaces. Here, we investigate the efficacy and optimum conditions at which weak acids can eradicate biofilms. We compared the efficacy of various mono and triprotic weak acids such as N-acetyl cysteine (NAC), acetic acid, formic acid and citric acid, in eradicating biofilms. We found that monoprotic weak acids/acid drugs can kill mucoid P. aeruginosa mucA biofilm bacteria provided the pH is less than their pKa, demonstrating that the extracellular biofilm matrix does not protect the bacteria from the activity of the weak acids. Triprotic acids, such as citric acid, kill biofilm bacteria at pH ​< ​pKa1. However, at a pH between pKa1 and pKa2, citric acid is effective in killing the bacteria at the core of biofilm microcolonies but does not kill the bacteria on the periphery. The efficacy of a monoprotic weak acid (NAC) and triprotic weak acid (citric acid) were tested on biofilms formed by Klebsiella pneumoniae KP1, Pseudomonas putida OUS82, Staphylococcus aureus 15981, P. aeruginosa DK1-NH57388A, a mucoid cystic fibrosis isolate and P. aeruginosa PA_D25, an antibiotic resistant strain. We showed that weak acids have a broad spectrum of activity against a wide range of bacteria, including antibiotic resistant bacteria. Further, we showed that a weak acid drug, NAC, can kill bacteria without being toxic to human cells, if its pH is maintained close to its pKa. Thus weak acids/weak acid drugs target antibiotic resistant bacteria and eradicate the persister cells in biofilms which are tolerant to other conventional methods of biofilm eradication.

Phage steering of antibiotic-resistance evolution in the bacterial pathogen, Pseudomonas aeruginosa.

Antimicrobial resistance is a growing global concern and has spurred increasing efforts to find alternative therapeutics. Bacteriophage therapy has seen near constant use in Eastern Europe since its discovery over a century ago. One promising approach is to use phages that not only reduce bacterial pathogen loads but also select for phage resistance mechanisms that trade-off with antibiotic resistance-so called 'phage steering'. Recent work has shown that the phage OMKO1 can interact with efflux pumps and in so doing select for both phage resistance and antibiotic sensitivity of the pathogenic bacterium Pseudomonas aeruginosa. We tested the robustness of this approach to three different antibiotics in vitro (tetracycline, erythromycin and ciprofloxacin) and one in vivo (erythromycin). We show that in vitro OMKO1 can reduce antibiotic resistance of P. aeruginosa (Washington PAO1) even in the presence of antibiotics, an effect still detectable after ca.70 bacterial generations in continuous culture with phage. Our in vivo experiment showed that phage both increased the survival times of wax moth larvae (Galleria mellonella) and increased bacterial sensitivity to erythromycin. This increased antibiotic sensitivity occurred both in lines with and without the antibiotic. Our study supports a trade-off between antibiotic resistance and phage sensitivity. This trade-off was maintained over co-evolutionary time scales even under combined phage and antibiotic pressure. Similarly, OMKO1 maintained this trade-off in vivo, again under dual phage/antibiotic pressure. Our findings have implications for the future clinical use of steering in phage therapies. Lay Summary: Given the rise of antibiotic-resistant bacterial infection, new approaches to treatment are urgently needed. Bacteriophages (phages) are bacterial viruses. The use of such viruses to treat infections has been in near-continuous use in several countries since the early 1900s. Recent developments have shown that these viruses are not only effective against routine infections but can also target antibiotic resistant bacteria in a novel, unexpected way. Similar to other lytic phages, these so-called 'steering phages' kill the majority of bacteria directly. However, steering phages also leave behind bacterial variants that resist the phages, but are now sensitive to antibiotics. Treatment combinations of these phages and antibiotics can now be used to greater effect than either one independently. We evaluated the impact of steering using phage OMKO1 and a panel of three antibiotics on Pseudomonas aeruginosa, an important pathogen in hospital settings and in people with cystic fibrosis. Our findings indicate that OMKO1, either alone or in combination with antibiotics, maintains antibiotic sensitivity both in vitro and in vivo, giving hope that phage steering will be an effective treatment option against antibiotic-resistant bacteria.

Targeting antibiotic resistant bacteria with phage reduces bacterial density in an insect host

Phage therapy is attracting growing interest among clinicians as antibiotic resistance continues becoming harder to control. However, clinical trials and animal model studies on bacteriophage treatment are still scarce and results on the efficacy vary. Recent research suggests that using traditional antimicrobials in concert with phage could have desirable synergistic effects that hinder the evolution of resistance. Here, we present a novel insect gut model to study phage-antibiotic interaction in a system where antibiotic resistance initially exists in very low frequency and phage specifically targets the resistance bearing cells. We demonstrate that while phage therapy could not reduce the frequency of target bacteria in the population during positive selection by antibiotics, it alleviated the antibiotic induced blooming by lowering the overall load of resistant cells. The highly structured gut environment had pharmacokinetic effects on both phage and antibiotic dynamics compared with in vitro: antibiotics did not reduce the overall amount of bacteria, demonstrating a simple turnover of gut microbiota from non-resistant to resistant population with little cost. The results imply moderate potential for using phage as an aid to target antibiotic resistant gut infections, and question the usefulness of in vitro inferences.

Removal of antibiotic residues, antibiotic resistant bacteria and antibiotic resistance genes in municipal wastewater by membrane bioreactor systems

Antibiotic residues, antibiotic resistant bacteria (ARB) and antibiotic resistance genes (ARGs) are considered new classes of water contaminants due to their potential adverse effects on aquatic ecosystems and human health. This paper provides comprehensive data on the occurrences of 19 antibiotics, bacteria resistant to 10 antibiotics, and 15 ARGs in raw influent and different treatment stages of conventional activated sludge (CAS) and membrane bioreactor (MBR) systems. Seventeen out of the 19 target antibiotics were detected in raw influent with concentrations of up to ten micrograms per liter. Concentrations of antibiotics measured in the secondary effluent were much lower compared to those in the raw influent. Among the antibiotics, amoxicillin, azithromycin, ciprofloxacin, chloramphenicol, meropenem, minocycline, oxytetracycline, sulfamethazine and vancomycin had highest removal by CAS or MBR systems with median removal efficiency (RE) > 70%, while trimethoprim and lincomycin were recalcitrant in the CAS system with median RE <50%. Similarly, the target ARB and ARGs were omnipresent in the raw influent samples with average concentrations as high as 2.6 × 106 CFU/mL and 2.0 × 107 gene copies/mL, respectively. The concentrations of ARB in secondary effluent of the CAS system declined relative to the raw influent (i.e. lower than raw influent by 2–3 orders of magnitude) and no ARB were detected in the MF permeate of the MBR system. For ARGs, their concentrations in secondary effluent/MF permeate ranged from below method quantification limit (<MQL) to 104 gene copies/mL. It is noteworthy that several ARGs, i.e. blaKPC, blaNDM, blaSHV, ermB, intI1, sul1 and tetO, were still found in the MF permeate of the MBR system at average concentrations up to 103 copies/mL. In conclusion, MBR outperformed CAS in the elimination of ARB, ARGs and most target antibiotics.

Mannoside and 1,2-mannobioside β-cyclodextrin-scaffolded NO-photodonors for targeting antibiotic resistant bacteria

Two β-cyclodextrin derivatives randomly appended on the primary face with both the nitric oxide (NO) photodonor 4-nitro-3-(trifluoromethyl)aniline and a mannose or α(1→2)mannobioside residue are reported to construct targeted NO photoreleasing nanocarriers. 2D ROESY and PGSE NMR suggested supramolecular homodimerization in water by inclusion of the nitroaniline group into the facing macrocycle cavities. Isothermal titration calorimetry on their concanavalin A lectin binding showed an exothermic binding event to the lectin and an endothermic process during the dilution of the conjugates. Both α(1→2)mannobioside and the nitroaniline moieties significantly enhanced the binding to the lectin. These effects might arise from a better fit within the carbohydrate-recognition site in the former case and a multivalent effect caused by homodimerization in the latter. Direct detection of NO by amperometric technique shows that both β-cyclodextrin derivatives release this radical upon excitation with visible light with higher efficiency than the unfunctionalized NO photodonor.

Microbial approaches for targeting antibiotic-resistant bacteria.

SummaryAntibiotic resistant bacterial infections are a global public health challenge that has been increasing in severity and scope for the last few decades. Without creative solutions to this problem, treatment of injuries and infections will become progressively more challenging. A better understanding of the human microbiome has led to a new appreciation for the role commensal microbes play in protecting us from pathogens, especially in the gut. Antibiotics lead to disruption of the gut microbial ecosystem, enabling colonization by antibiotic resistant bacterial pathogens. Many different lines of research have identified specific bacterial taxa and mechanisms that play a role in colonization resistance, and these lines of research may one day lead to microbial therapeutics targeting antibiotic resistant bacteria. Here, we discuss a few of these strategies and the challenges they will need to overcome in order to become an effective therapeutic.

Inactivation and regrowth of multidrug resistant bacteria in urban wastewater after disinfection by solar-driven and chlorination processes

Solar disinfection and solar-driven advanced oxidation processes (AOPs) (namely H2O2/sunlight, TiO2/sunlight, H2O2/TiO2/sunlight, solar photo-Fenton) were evaluated in the inactivation of indigenous antibiotic-resistant bacteria (ARB) in real urban wastewater. A multidrug resistant (MDR) Escherichia coli strain isolated from the effluent of the biological process of an urban wastewater treatment plant was the target ARB. The higher inactivation rates (residual density under detection limit, 2CFUmL−1) were achieved with H2O2/TiO2/sunlight (cumulative energy per unit of volume (QUV) in the range 3–5kJL−1, depending on H2O2/TiO2 ratio) and H2O2/sunlight (QUV of 8kJL−1) processes. All investigated processes did not affect antibiotic resistance of survived colonies. Moreover, H2O2/sunlight was compared with conventional chlorination process to evaluate bacterial regrowth potential and particularly the proportion of indigenous MDR E. coli with respect to total indigenous E. coli population. Chlorination (1.0mg Cl2L−1) was more effective than H2O2/sunlight (50mg H2O2L−1) to achieve total inactivation of MDR E. coli (15min Vs 90min) but less effective in controlling their regrowth (24h Vs 48h). Interestingly, the percentage of MDR E. coli in H2O2/sunlight treated samples decreased as incubation time increased; the opposite was observed for chlorinated samples.