TABLE 3.

Nucleotide differences identified in rifampin- and spectinomycin-resistant isolates of C. psittaci 6BC and C. trachomatis L2

Mutant strainNo. of independent mutations analyzedCharacteristic of mutant alleleaMIC
TotalDistributionDesignationNucleotide changeRepresentative chlamydial mutantAllele distribution in drug-resistant organisms
C. trachomatis L2 Rifr11rpoB1GAU→GGU (Asp516→Gly)L2R1Mycobacterium tuberculosis, Helicobacter pylori800 ng/ml
C. psittaci 6BC Rifr11rpoB2AUG→AUC (Met515→Ile)BCR1M. tuberculosis300 ng/ml
C. psittaci 6BC Spcr595216S1C1192UBC0E1E. coli, Neisseria sp., Nicotiana tabacum chloroplasts>10 mg/mlb
516S2A1191GBC0A2Chlamydomonas reinhardtii chloroplasts>10 mg/mlb
116S3C1192GBCS18E. coli>10 mg/mlb
116S4G1193CBCS34Not previously reported5 mg/ml
  • a Each distinct mutation identified was given an allele name (designation), which represents a specific change (E. coli numbering) at the indicated nucleotide in the rpoB or 16S rRNA sequence.

  • b Spc concentrations above 10 mg/ml were cytotoxic to mouse fibroblast cells in the monolayer.