Occurrence of extended-spectrum β-lactamases among Escherichia coli isolates from hospitalized and healthy children.

The prevalence of extended-spectrum β-lactamases (ESBL) was determined among isolates of Escherichia coli ( n=63) isolated from hospitalized (43) and healthy (20) children. Ten isolates (21 %) were ESBL-positive for two screening tests, the double disk-synergy test and the Oxoid Combination Disk method. One ESBL-positive isolate came from a healthy child. The transfer frequency of oxyimino-β-lactam resistance from ESBL-producing isolates to E. coli K12 C600 recipient strain ranged from 10⁻⁸ to 10⁻⁵ per donor cell. Donor strains and transconjugants displayed susceptibility patterns typical of ESBL producers. They were resistant to oxyimino-β-lactams but susceptible to clavulanic acid and carbapenems. Seven out of the 10 ESBL-positive isolates were found to produce MR/MS fimbria, which may play an important role in the colonization of the human intestinal mucosa. [ABSTRACT FROM AUTHOR]