Amino acid requirements of strains of Chlamydia trachomatis and C. psittaci growing in McCoy cells: relationship with clinical syndrome and host origin.

The effects of omission of individual amino acids from growth medium on the multiplication of a range of Chlamydia trachomatis and C. psittaci strains in cycloheximide-treated McCoy cells have been assessed. Differences in requirements were revealed which for C. trachomatis strains correlated with clinical syndrome and for C. psittaci with host origin. All 11 strains of C. trachomatis examined showed a requirement for addition of histidine to the medium; this was not shown by any of four C. psittaci strains. Among the strains of C. trachomatis, three from cases of trachoma, representing serotypes A, B and C, showed a distinctive requirement for the addition of tryptophan to the medium, whilst six strains of oculogenital origin, representing serotypes D-I, exhibited no requirement for tryptophan or methionine; a lymphogranuloma venereum and a 'fast variant' strain both showed a requirement for methionine. Of the four C. psittaci strains from different hosts, three showed distinct patterns of amino acid requirements. All chlamydiae required the addition of valine to medium and the majority required leucine, phenylalanine and also glutamine.