optochin mechanism of action

Investigators from Spain recently identified a gene responsible for the optochin susceptibility/resistance phenotype [13]. Muñoz et al. Yellow circles amino acid residues identical to those of the E. coli sequence; orange circles residues that are similar in structure; open circles residues unique to S. pneumoniae enzyme. Resistant strains had MICs of optochin 4–30-fold higher than susceptible strains, belonged to different serotypes, and had dissimilar restriction fragment profiles, indicating clonal unrelatedness. α-Hemolytic streptococci resistant to optochin, particularly invasive isolates, should be tested for bile solubility or with an S. pneumoniae DNA probe before identification as viridans streptococci, Streptococcus pneumoniae remains a major cause of human morbidity and mortality, particularly at both extremes of the age spectrum [1]. A commercial DNA probe test is of higher sensitivity and specificity than standard tests [19] but may be too expensive for routine use. Select One: A. Principle of Optochin Sensitivity Test. In optochin-resistant S. pneumoniae amino acid changes within the a- or c-subunits prevent optochin from disrupting the H+ transport path, The origin of optochin resistance in S. pneumoniae is unclear. It furthers the University's objective of excellence in research, scholarship, and education by publishing worldwide, This PDF is available to Subscribers Only. The proton pathway through the membrane is thought to be formed by an opening of the interface between adjacent c-subunits by swiveling of helix 1, thus allowing a hydrogen from the protonated glutamate 52 carboxyl side chain on helix 2 to transfer to the a-subunit on the outer surface of the cylinder [33], Streptococcus pneumoniae/Escherichia coli H+-ATPase subunit model with equivalent amino acids, In our putative model, all amino acid mutations that confer optochin resistance are located within those regions of helices that transverse the membrane. Optochin sensitivity allows for the presumptive identification of alpha-hemolytic streptococci as S. pneumoniae, although some pneumococcal strains are optochin-resistant. For isolates with mixed populations of optochin-susceptible (S) and -resistant (R) colonies, PFGE was performed on both susceptible colonies and resistant variants, We compared the ATPase c-subunit amino acid sequences from optochin-susceptible and -resistant strains to ascertain whether optochin resistance was associated with any amino acid changes [13]. Individual c-subunits consist of 2 transmembrane α-helices joined by a short conserved cytoplasmic loop. Results showed identical optochin MICs between the transformants and the original optochin-resistant donors. By analogy to the E. coli enzyme, the putative S. pneumoniae model for the F0 portion of ATPase consists of a membrane-embedded cylinder made up of 10–12 c-subunits with 1 a-subunit positioned within the membrane matrix on the outer surface of the cylinder. Most clinical microbiology laboratories today depend on the optochin susceptibility test [4], Optochin, a quinine analogue, was introduced early in the twentieth century as a chemotherapeutic agent for the treatment of lobar pneumonia. Three of our isolates also produced a mixed population of optochin-susceptible and -resistant colonies. Site-specific mutagenesis of an optochin-susceptible S. pneumoniae strain at single amino acid residues corresponding to changes in either the a-subunit (Trp206Ser) or the c-subunit (Gly20Ser, Met23Ile, and Ala49Thr) conferred optochin resistance. Both subpopulations had identical antibiograms, serotypes, and restriction fragment profiles. Suspensions were inoculated onto Mueller-Hinton agar containing 3% lysed horse blood and varying concentrations of optochin or selected antimicrobial agents. Although optochin susceptibility was first described for differentiating pneumococci from other α-hemolytic streptococci in 1915 [6], the test was virtually unused by laboratories until the mid-1950s [7–9]. This hypothesis is strongly supported by the findings from the 3 isolates with optochin-resistant variants. Strains displaying a growth inhibitory zone ⩾14 mm in diameter around a 6-mm optochin disk are identified as S. pneumoniae. Opioids have actions at two sites, the presynaptic nerve terminal and the postsynaptic neuron. The recent emergence of pneumococci resistant to penicillin, third-generation cephalosporins, and other antimicrobial agents has raised concerns about treatment of patients with serious pneumococcal infections [2]. E. coli transformants were selected on LB agar containing 50 μg/mL kanamycin, DNA sequence analysisSequencing was done with the dideoxynucleotide chain-termination method by using modified T7 DNA polymerase and [α-35S]deoxyadenosine triphosphate for labeling. The ATPase from E. coli is one of the best-studied models of a membrane-bound enzyme complex. Optochin resistance is frequently due to point mutations in the atpC gene, which encodes a subunit of the membrane-spanning ATPase. [23], Hatch et al. In 1987, Kontiainen and Sivonen [10] were the first to report pneumococci that exhibited an optochin-resistant subpopulation. Three of the 4 isolates consisted of mixed populations of optochin-resistant and -susceptible organisms. : Application in the synthesis of solketal derived Monoacylglycerols. In vitro, a minimum inhibitory concentration (MIC) of 1:10,000,000 will inhibit the growth of pneumococci, and 1:500,000 is bactericidal. Three (0.5%) isolates were either uniformly resistant to optochin (strain 310) or consisted of mixed populations of optochin-susceptible and -resistant colonies (strains 606α and 654; figure 1). Board Certified or Board Eligible AP/CP Full-Time or Part-Time Pathologist, Chief of ID, VA Ann Arbor Healthcare System, Copyright © 2020 Infectious Diseases Society of America. Our other 2 optochin-resistant isolates had mutations (Gly20Ser and Met23Ile) within the α-helix 1 transmembrane domain of the ATPase c-subunit (figure 5). [11]. The F0 sector of the complex comprises membrane-embedded protein subunits that translocate hydrogen ions, while the F1 component of the complex contains the catalytic subunit for ATP hydrolysis and synthesis [22], We compared sequences of ATPase a- and c-subunits from various optochin-resistant and -susceptible pneumococcal strains and found that several single amino acid mutations segregate with optochin resistance (figures 3 and 4). Optochin (or ethylhydrocupreine hydrochloride) is a derivative of hydroquinine introduced in 1911 by Morgenroth and Levy with the intention to treat pneumococci infection. Complete clearing of the suspension in the deoxycholate tube was indicative of S. pneumoniae, SerotypingSerotyping was done with the Quellung (Neufeld) reaction (capsular swelling) test, Genomic DNA analysisPreparation of agarose plugs containing genomic DNA and analysis by pulsed-field gel electrophoresis (PFGE) after digestion with SmaI were done as described elsewhere [16], Polymerase chain reaction (PCR)Based on the sequence reported by Fenoll et al. The presence of antibacterials in a given environment provides selective pressure that results in the enrichment of resistant strains. Although the molecular mechanism of exactly how optochin interacts with the F0 portion of ATPase is still unresolved, we believe that in the presence of optochin the proton-translocating subunits of ATPase are perturbed in such a way that the H+ pump fails and the cell dies. in sequence. [3], InChI=1S/C21H28N2O2/c1-3-14-13-23-10-8-15(14)11-20(23)21(24)17-7-9-22-19-6-5-16(25-4-2)12-18(17)19/h5-7,9,12,14-15,20-21,24H,3-4,8,10-11,13H2,1-2H3/t14-,15-,20-,21+/m0/s1, InChI=1/C21H28N2O2/c1-3-14-13-23-10-8-15(14)11-20(23)21(24)17-7-9-22-19-6-5-16(25-4-2)12-18(17)19/h5-7,9,12,14-15,20-21,24H,3-4,8,10-11,13H2,1-2H3/t14-,15-,20-,21+/m0/s1, CC[C@H]1CN2CC[C@H]1C[C@H]2[C@@H](c3ccnc4c3cc(cc4)OCC)O, Except where otherwise noted, data are given for materials in their, "The Action of Ethylhydrocuprein (Optochin) on Type Strains of Pneumococci in Vitro and in Vivo, and on Some Other Microorganisms in Vitro", http://chestofbooks.com/health/materia-medica-drugs/Pharmacology-Therapeutics-Prescription-Writing/Ethylhydrocupreine.html, https://en.wikipedia.org/w/index.php?title=Optochin&oldid=985927795, Articles with changed ChemSpider identifier, Pages using collapsible list with both background and text-align in titlestyle, Articles containing unverified chemical infoboxes, Creative Commons Attribution-ShareAlike License, This page was last edited on 28 October 2020, at 19:46.

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