scholarly journals Phenotypic Characterization of Two Ancylostoma caninum Isolates with Different Susceptibilities to the Anthelmintic Pyrantel

2008 ◽  
Vol 52 (11) ◽  
pp. 3980-3986 ◽  
Author(s):  
Steven R. Kopp ◽  
Glen T. Coleman ◽  
James S. McCarthy ◽  
Andrew C. Kotze
Keyword(s):  
Nicotinic Acetylcholine Receptors ◽  
Acetylcholine Receptors ◽  
Resistance Mechanism ◽  
Fold Increase ◽  
Phenotypic Characterization ◽  
Gastrointestinal Helminths ◽  
Ancylostoma Caninum ◽  
High Level ◽  
Level Resistance

ABSTRACT The anthelmintic pyrantel plays an important role in the control of gastrointestinal helminths of humans and domestic animals. Despite the demonstration of pyrantel resistance in several helminth species over the last 20 years, the resistance mechanism remains unclear. It has been hypothesized that resistance may arise as a consequence of changes to the relative proportions of subpopulations of nicotinic acetylcholine receptors (nAchRs). To test this hypothesis, we examined the responses of two isolates of the canine hookworm Ancylostoma caninum with low-level resistance (isolate NT) and high-level resistance (isolate PR) to pyrantel to nicotinic agonist drugs reported to be selective for three nAchR subtypes. We used larval motility and conformation assays and force transduction experiments with adult worms. Pyrantel and levamisole were less potent against larvae of isolate PR than larvae of isolate NT (up to an 18-fold increase in the 50% inhibitory concentration); on the other hand, bephenium was more potent against larvae of isolate PR than larvae of isolate NT (twofold) and nicotine had the same potency against larvae of both isolates. In adults, pyrantel, levamisole, and nicotine were less potent against isolate PR than isolate NT (two- to threefold), but the potency of bephenium against the two isolates was equivalent. Our data indicate a complex pattern of nAchRs in this species and suggest that the two isolates differ in their relative sensitivities to agonists targeting different nAchRs.

scholarly journals Phenotypic characterization of R-factor tetracycline resistance determinants

1974 ◽  
Vol 24 (3) ◽  
pp. 333-343 ◽  
Author(s):  
T. J. Foster ◽  
Áine Walsh
Keyword(s):  
Tetracycline Resistance ◽  
Phenotypic Characterization ◽  
Resistance Determinants ◽  
R Factor ◽  
Moderate Resistance ◽  
High Level ◽  
R Factors ◽  
Phenotypic Groups ◽  
Level Resistance

SUMMARYThe tetracycline-resistance determinants of R-factors from different compatibility groups have been tested inEscherichia coliK12 and phenotypically classified into two major classes. Class I determinants confer high-level resistance to tetracycline (> 100 μg/ml) and moderate resistance to minocycline (5–25 μg/ml) while those of Class II gave moderate resistance to tetracycline (50–70 μg/ml) and low resistance to minocycline. Each class was subdivided because of variation in resistance profiles and in the abilities of tetracycline and minocycline to induce increased resistance. Strains carrying two compatible TetrR-factors of the same or different phenotypic groups did not show increased tetracycline resistance.

scholarly journals Characterization of an Enterococcus gallinarum Isolate Carrying a DualvanAandvanBCassette

2015 ◽  
Vol 53 (7) ◽  
pp. 2225-2229 ◽  
Author(s):  
Alireza Eshaghi ◽  
Dea Shahinas ◽  
Aimin Li ◽  
Ruwandi Kariyawasam ◽  
Philip Banh ◽  
...  
Keyword(s):  
Clinical Isolate ◽  
Resistance Mechanism ◽  
Vancomycin Resistance ◽  
Content Type ◽  
Enterococcal Species ◽  
Enterococcus Gallinarum ◽  
High Level ◽  
Identification And Characterization ◽  
Level Resistance

The ability of vancomycin resistance determinants to be horizontally transferred within enterococci species is a concern. Identification and characterization of vancomycin-resistant enterococci (VRE) in a clinical isolate have a significant impact on infection control practices. In this study, we describe a clinical isolate ofEnterococcus gallinarumexhibiting high-level resistance to vancomycin and teicoplanin. The genetic characterization of this isolate showed the presence ofvanAandvanBgenes in addition to the naturally carriedvanCgene.vanAwas identified on pA6981, a 35,608-bp circular plasmid with significant homology to plasmid pS177. ThevanBoperon was integrated into the bacterial chromosome and showed a high level of homology to previously reported Tn1549and Tn5382. To the best of our knowledge, this is the first report ofE. gallinarumcarrying bothvanAandvanBoperons, indicating the importance of identifying the vancomycin resistance mechanism in non-E. faeciumand non-E. faecalisenterococcal species.

scholarly journals WGS of Commensal Neisseria Reveals Acquisition of a New Ribosomal Protection Protein (MsrD) as a Possible Explanation for High Level Azithromycin Resistance in Belgium

Pathogens ◽  
2021 ◽  
Vol 10 (3) ◽  
pp. 384
Author(s):  
Tessa de Block ◽  
Jolein Gyonne Elise Laumen ◽  
Christophe Van Dijck ◽  
Said Abdellati ◽  
Irith De Baetselier ◽  
...  
Keyword(s):  
Integration Site ◽  
Bacterial Species ◽  
Resistance Mechanism ◽  
Health Concern ◽  
Sex With Men ◽  
High Level ◽  
Ribosomal Protection Protein ◽  
Commensal Neisseria ◽  
Level Resistance ◽  
Ribosomal Protection

In this study, we characterized all oropharyngeal and anorectal isolates of Neisseria spp. in a cohort of men who have sex with men. This resulted in a panel of pathogenic Neisseria (N. gonorrhoeae [n = 5] and N. meningitidis [n = 5]) and nonpathogenic Neisseria (N. subflava [n = 11], N. mucosa [n = 3] and N. oralis [n = 2]). A high proportion of strains in this panel were resistant to azithromycin (18/26) and ceftriaxone (3/26). Whole genome sequencing (WGS) of these strains identified numerous mutations that are known to confer reduced susceptibility to azithromycin and ceftriaxone in N. gonorrhoeae. The presence or absence of these known mutations did not explain the high level resistance to azithromycin (>256 mg/L) in the nonpathogenic isolates (8/16). After screening for antimicrobial resistance (AMR) genes, we found a ribosomal protection protein, Msr(D), in these highly azithromycin resistant nonpathogenic strains. The complete integration site originated from Streptococcus pneumoniae and is associated with high level resistance to azithromycin in many other bacterial species. This novel AMR resistance mechanism to azithromycin in nonpathogenic Neisseria could be a public health concern if it were to be transmitted to pathogenic Neisseria. This study demonstrates the utility of WGS-based surveillance of nonpathogenic Neisseria.

Biophysical and pharmacological characterization of α6-containing nicotinic acetylcholine receptors expressed in HEK293 cells

2014 ◽  
Vol 1542 ◽  
pp. 1-11 ◽  
Author(s):  
Andreas H. Rasmussen ◽  
Dorte Strøbæk ◽  
Tino Dyhring ◽  
Marianne L. Jensen ◽  
Dan Peters ◽  
...  
Keyword(s):  
Nicotinic Acetylcholine Receptors ◽  
Acetylcholine Receptors ◽  
Hek293 Cells ◽  
Pharmacological Characterization ◽  
Nicotinic Acetylcholine

Molecular characterization of the specificity of interactions of various neurotoxins on two distinct nicotinic acetylcholine receptors

2000 ◽  
Vol 393 (1-3) ◽  
pp. 197-204 ◽  
Author(s):  
Denis Servent ◽  
Stéphanie Antil-Delbeke ◽  
Carole Gaillard ◽  
Pierre-Jean Corringer ◽  
Jean Pierre Changeux ◽  
...  
Keyword(s):  
Molecular Characterization ◽  
Nicotinic Acetylcholine Receptors ◽  
Acetylcholine Receptors ◽  
Nicotinic Acetylcholine

scholarly journals αM-Conotoxin MIIIJ Blocks Nicotinic Acetylcholine Receptors at Neuromuscular Junctions of Frog and Fish

Toxins ◽  
2020 ◽  
Vol 12 (3) ◽  
pp. 197
Author(s):  
Matthew J. Rybin ◽  
Henrik O’Brien ◽  
Iris Bea L. Ramiro ◽  
Layla Azam ◽  
J. Michael McIntosh ◽  
...  
Keyword(s):  
Nicotinic Acetylcholine Receptors ◽  
Acetylcholine Receptors ◽  
Neuromuscular Junctions ◽  
Functional Characterization ◽  
Cone Snail ◽  
Nicotinic Acetylcholine ◽  
New Class ◽  
Goldfish Carassius Auratus ◽  
Snake Neurotoxin

We report the discovery and functional characterization of αM-Conotoxin MIIIJ, a peptide from the venom of the fish-hunting cone snail Conus magus. Injections of αM-MIIIJ induced paralysis in goldfish (Carassius auratus) but not mice. Intracellular recording from skeletal muscles of fish (C. auratus) and frog (Xenopus laevis) revealed that αM-MIIIJ inhibited postsynaptic nicotinic acetylcholine receptors (nAChRs) with an IC50 of ~0.1 μM. With comparable potency, αM-MIIIJ reversibly blocked ACh-gated currents (IACh) of voltage-clamped X. laevis oocytes exogenously expressing nAChRs cloned from zebrafish (Danio rerio) muscle. αM-MIIIJ also protected against slowly-reversible block of IACh by α-bungarotoxin (α-BgTX, a snake neurotoxin) and α-conotoxin EI (α-EI, from Conus ermineus another fish hunter) that competitively block nAChRs at the ACh binding site. Furthermore, assessment by fluorescence microscopy showed that αM-MIIIJ inhibited the binding of fluorescently-tagged α-BgTX at neuromuscular junctions of X. laevis, C. auratus, and D. rerio. (Note, we observed that αM-MIIIJ can block adult mouse and human muscle nAChRs exogenously expressed in X. laevis oocytes, but with IC50s ~100-times higher than those of zebrafish nAChRs.) Taken together, these results indicate that αM-MIIIJ inhibits muscle nAChRs and furthermore apparently does so by interfering with the binding of ACh to its receptor. Comparative alignments with homologous sequences identified in other fish hunters revealed that αM-MIIIJ defines a new class of muscle nAChR inhibitors from cone snails.

scholarly journals Identification of Crucial Residues in α-Conotoxin EI Inhibiting Muscle Nicotinic Acetylcholine Receptor

Toxins ◽  
2019 ◽  
Vol 11 (10) ◽  
pp. 603 ◽  
Author(s):  
Jiong Ning ◽  
Jie Ren ◽  
Yang Xiong ◽  
Yong Wu ◽  
Manqi Zhangsun ◽  
...  
Keyword(s):  
Nicotinic Acetylcholine Receptors ◽  
Acetylcholine Receptors ◽  
Fold Increase ◽  
Cd Spectroscopy ◽  
Xenopus Laevis Oocytes ◽  
Muscle Type ◽  
Nicotinic Acetylcholine ◽  
Activity Loss ◽  
Spectroscopy Studies ◽  
Key Residues

α-Conotoxins (α-CTxs) are small disulfide-rich peptides from venom of Conus species that target nicotinic acetylcholine receptors (nAChRs). The muscle-type nAChRs have been recognized as a potential target for several diseases, such as myogenic disorders, muscle dystrophies, and myasthenia gravis. EI, an α4/7-CTx, mainly blocks α1β1δε nAChRs and has an extra N-terminal extension of three amino acids. In this study, the alanine scanning (Ala-scan) mutagenesis was applied in order to identify key residues of EI for binding with mouse α1β1δε nAChR. The Ala-substituted analogues were tested for their abilities of modulating muscle and neuronal nAChRs in Xenopus laevis oocytes using two-electrode voltage clamp (TEVC) recordings. Electrophysiological results indicated that the vital residues for functional activity of EI were His-7, Pro-8, Met-12, and Pro-15. These changes exhibited a significant decrease in potency of EI against mouse α1β1δε nAChR. Interestingly, replacing the critical serine (Ser) at position 13 with an alanine (Ala) residue resulted in a 2-fold increase in potency at the α1β1δε nAChR, and showed loss of activity on α3β2 and α3β4 nAChRs. Selectivity and potency of [S13A] EI was improved compared with wild-type EI (WT EI). In addition, the structure–activity relationship (SAR) of EI revealed that the “Arg1–Asn2–Hyp3” residues at the N-terminus conferred potency at the muscle-type nAChRs, and the deletion analogue △1–3 EI caused a total loss of activity at the α1β1δε nAChR. Circular dichroism (CD) spectroscopy studies demonstrated that activity loss of truncated analogue △1–3 EI for α1β1δε nAChR is attributed to disturbance of the secondary structure. In this report, an Ala-scan mutagenesis strategy is presented to identify crucial residues that are significantly affecting potency of E1 for mouse α1β1δε nAChR. It may also be important in remodeling of some novel ligands for inhibiting muscle-type nAChRs.

Characterization of AN317, a novel selective agonist of α6β2-containing nicotinic acetylcholine receptors

2020 ◽  
Vol 174 ◽  
pp. 113786 ◽  
Author(s):  
Karin Sandager-Nielsen ◽  
Philip K. Ahring ◽  
Jessica Klein ◽  
Marloes van Hout ◽  
Siganya Thaneshwaran ◽  
...  
Keyword(s):  
Nicotinic Acetylcholine Receptors ◽  
Acetylcholine Receptors ◽  
Nicotinic Acetylcholine ◽  
Selective Agonist
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