[Molecular characterization of resistance mechanisms to chloramphenicol in Shigella flexneri strains isolated from Chilean children with acute diarrhea].

BACKGROUND

Chloramphenicol is one of the therapeutic options for shigellosis, but resistance to this antimicrobial is increasing.

AIM

To characterize molecular mechanisms conferring resistance to chloramphenicol (Cm) in Shigella flexneri strains isolated from Chilean children with acute diarrhea.

MATERIAL AND METHODS

Thirty one Shigella filexneri strains, including 22 with the Cm phenotype were analyzed. Strains were tested for antimicrobial susceptibility by plate dilution and for the presence of an internal fragment of the cat gene encoding for chloramphenicol o-acetyl-transferase, by polymerase chain reaction and Southern blot analysis.

RESULTS

All Cm strains had a minimal inhibitory concentration over 64 micrograms/ml and amplified the internal fragment of the cat gene. Southern blot analyses indicated that this gene was located in the bacterial chromosome.

CONCLUSIONS

Resistance to chloramphenicol in this group of Shigella flexneri strains was mediated by a chromosomally located cat gene.