Re-evaluation of antibiotic and mercury resistance in Escherichia coli populations isolated in 1978 from Amazonian rubber tree tappers and Indians

A study was carried out to assess the stability of antimicrobial susceptibi lity of wild isolates upon long-term storage using fifty-three Escherichia coli strains isolated in :1978 from feces of healthy children from the Amaz on region in Brazil, exposed to low levels of antimicrobial agents, and exa mined for resistance to mercury and four antibiotics. All of the strains we re kept in Lignieres medium at room temperature and were transferred to fre sh media four times during this period. Thirty-five out of the 53 strains a nalyzed in 1978 were viable. Upon recovery, antibiotic and mercury resistan ce was estimated. All of the 35 strains maintained their original phenotype in a stable fashion, except for one multiresistant strain which became sus ceptible to kanamycin. Fifty-four percent of the strains exhibited a resist ance phenotype, among which 47% had conjugative plasmids. (C) Elsevier, Par is.