[11]. No relationship between resistance to optochin and other antimicrobial agents tested was detected. Even though bile-insoluble pneumococcal isolates have been reported [21], the addition of this latter test should minimize the possibility of misidentification. [13], we designed primers 663 (5′-TCGAAAAGTGGATCAACAACTATCC-3′) and 1016 (5′-TGGGAAAGAAGAAGTAACAAACTCG-3′) to amplify the DNA fragment encoding the ATPase c-subunit from the pneumococcal strains examined in this study. The postsynaptic actions of opioids are usually inhibitory. What is the mechanism of action for optochin? in sequence. All the Spanish mutations (from clinical isolates or laboratory-generated mutants after selection on plates containing optochin) had mutations corresponding to the α-helix 2 domain of the ATPase c-subunit [13]. For isolates exhibiting optochin-resistant variants, sequence analyses were performed on both susceptible and resistant colonies. Even though none of our patients with optochin-resistant S. pneumoniae was treated for malaria or had a travel history to a malaria-endemic area, possible acquisition of these unique pneumococcal strains from persons who did seems plausible and cannot be ruled out. A commercial DNA probe test is of higher sensitivity and specificity than standard tests [19] but may be too expensive for routine use. For full access to this pdf, sign in to an existing account, or purchase an annual subscription. [24], Fillingame et al. Other alpha-hemolytic streptococcal species are optochin-resistant. Cultures were incubated at 35°C for 20–24 h in a 5% CO2 atmosphere. These results confirm that the single amino acid change observed in our clinical isolates is responsible for optochin resistance. When there is no inhibitory zone around the optochin disk, laboratories routinely identify isolates as viridans streptococci and do not perform bile solubility testing [21], Although S. pneumoniae was considered universally susceptible to optochin for almost 30 years after the optochin susceptibility test was introduced, a number of isolates have been reported as optochin resistant in recent years. [23], Hatch et al. Moreover, this is the first report of a mutation affecting the ATPase a-subunit. Select One: A. 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. Lipases of Endophytic Fungi Stemphylium lycopersici and Sordaria sp. Opioids have actions at two sites, the presynaptic nerve terminal and the postsynaptic neuron. Andreas Pikis, Joseph M. Campos, William J. Rodriguez, Jerry M. Keith, Optochin Resistance in Streptococcus pneumoniae: Mechanism, Significance, and Clinical Implications, The Journal of Infectious Diseases, Volume 184, Issue 5, 1 September 2001, Pages 582–590, https://doi.org/10.1086/322803, Traditionally, Streptococcus pneumoniae is identified in the laboratory by demonstrating susceptibility to optochin. Amino acid mutations that are responsible for optochin resistance are marked with red and show residue no., followed by amino acid mutation that confers resistance (G14S, G20S, M23I, V48F, A49T, and F50L in c-subunit and W206S in a-subunit). Structural and genetic analyses show that certain amino acid residues in the transmembrane domains of the model are essential for H+ translocation across the plasma membrane [22], To understand the structural relationship between a single amino acid mutation and the mechanism of optochin resistance in S. pneumoniae we compared the sequences of the a- and c-subunits of our strains with the corresponding E. coli sequences. Reprints or correspondence: Dr. Andreas Pikis, National Institute of Dental and Craniofacial Research, National Institutes of Health, Bldg. However, in isolates with optochin-resistant variants, comparison of PFGE of optochin-susceptible and -resistant colonies revealed identical profiles (figure 2), Pulsed-field gel electrophoresis (PFGE) of SmaI-digested chromosomal DNA from optochin-resistant isolates. The amino acid sequences in the 3 remaining optochin-resistant strains differed from the susceptible strains by only 1 amino acid. B. Our findings indicate that optochin resistance in S. pneumoniae is a result of point mutations in either the ATPase a- or c-subunit. Isolates with optochin-resistant variants formed distinct colonies within the 14-mm diameter inhibitory zone that differentiates optochin susceptibility from resistance. These quinine-resistant mutants, which also exhibited cross-resistance to optochin, were obtained by spreading R6 cells on plates containing quinine. Comparison of these sequences revealed that a serine residue replaced tryptophan at position 206 in the ATPase a-subunit of the resistant variant (figure 4), Comparison of ATPase a-subunit amino acid sequences between optochin-susceptible strain HV109/S and its optochin-resistant variant HV109/R.