[Primary investigation on variable but nonculturable-state of enterotoxigenic Escherichia coli in vitro].

Objective: 7 variable but nonculturable-state strains of Enterotoxigenic Escherichia coli (ETEC) during the routine bacterial subculture were found in our lab and their morphology and antigen studied. Biological features, antigens and pathogenicity of the revertants were also tested and compared to that of the initial strains in order to detect their variations.

Methods: Biological variations between the variable but nonculturable-state and the revertant of every strain were detected, using the routine gram-staining, reverting the isolates in animal intestinal, reverting their pathogenicity, serological agglutination, biochemical identifications and antibiotic resistance tests.

Results: For the 7 variable but nonculturable-state strains of ETEC,other than the trains that had changed into sphero vegetale cells, there were no other obvious variations found. However, high pathogenicity of these strains still remained.

Conclusion: The presence of variable but nonculturable-state strains suggested that the routine method of bacteria storage should be changed and more attention should be paid to realize the existence of this kind of bacteria during the routine surveillance of the communicable diseases.