Optochin resistance in Streptococcus pneumoniae: mechanism, significance, and clinical implications.
Traditionally, Streptococcus pneumoniae is identified in the laboratory by demonstrating susceptibility to optochin. Between 1992 and 1998, 4 pneumococcal isolates exhibiting optochin resistance were recovered from patients at Children's National Medical Center. Three of the 4 isolates consisted of mixed populations of optochin-resistant and -susceptible organisms. Both subpopulations had identical antibiograms, serotypes, and restriction fragment profiles. The other isolate was uniformly resistant to optochin. 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. Resistance arose from single point mutations in either the a-subunit (W206S) or the c-subunit (G20S, M23I, and A49T) of H(+)-ATPase. There is speculation of a possible association between exposure to antimalarial drugs and evolution of optochin resistance. alpha-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.
Pikis
A
A
Vaccine and Therapeutic Development Section, Oral Infection and Immunity Branch, National Institute of Dental and Craniofacial Research, National Institutes of Health, Bethesda, Maryland 20892-4350, USA. apikis@dir.nidcr.nih.gov
Campos
J M
JM
Rodriguez
W J
WJ
Keith
J M
JM
D000595:Amino Acid Sequence; D000900:Anti-Bacterial Agents / Q000494:pharmacology; D004352:Drug Resistance, Microbial / Q000235:genetics; D006801:Humans; D008826:Microbial Sensitivity Tests; D008969:Molecular Sequence Data; D011008:Pneumococcal Infections / Q000382:microbiology; D016133:Polymerase Chain Reaction; D006180:Proton-Translocating ATPases / Q000737:chemistry / Q000235:genetics; D011803:Quinine / Q000031:analogs & derivatives / Q000494:pharmacology*; D017422:Sequence Analysis, DNA; D012703:Serotyping; D013296:Streptococcus pneumoniae / Q000145:classification / Q000187:drug effects* / Q000302:isolation & purification
D000900:Anti-Bacterial Agents; C017303:ethylhydrocupreine; D011803:Quinine; D006180:Proton-Translocating ATPases