Relationship between sulfadiazine resistance and the failure to ferment maltose in Neisseria meningitidis.

The genetic marker for sulfadiazine resistance was transferred by means of purified deoxyribonucleic acid from sulfadiazine-resistant Neisseria meningitidis and N. perflava to a sulfadiazine-sensitive strain of N. meningitidis. Over 80% of the isolates from these experiments, selected on the basis of sulfadiazine resistance, failed to produce acid from maltose. The same proportion of naturally occurring isolates that are sulfadiazine-resistant failed to ferment maltose. The enzymatic block in 17 isolates tested was the loss of maltose permease activity; in two cases, maltose phosphorylase activity was lost also. The permease was present in these cells, however, and could be activated by the addition of sulfadiazine. The results obtained support the hypothesis that these organisms, in becoming resistant to sulfadiazine, have undergone a single mutation.