Evolution of TEM-Type Extended-Spectrum β-Lactamases in Clinical Enterobacteriaceae Strains in Poland

Abstract

ABSTRACT Seventeen extended-spectrum β-lactamase (ESBL)-producing isolates of the family Enterobacteriaceae recovered from 1998 to 2000 in hospitals of five different cities in Poland were analyzed. They expressed several TEM-type ESBLs, TEM-4, TEM-29, TEM-85, TEM-86, TEM-93, and TEM-94. TEM-85 (L21F, R164S, E240K, T265M), TEM-86 (L21F, R164S, A237T, E240K, T265M), TEM-93 (M182T, G238S, E240K), and TEM-94 (L21F, E104K, M182T, G238S, T265M) were identified for the first time. Including the enzymes described earlier, TEM-47, TEM-48, TEM-49, and TEM-68, the group of known ESBLs of the TEM family produced by enterobacteria in Polish hospitals has increased to 10 variants. Comparative sequence analysis of the genes coding for all these β-lactamases revealed a view of their possible evolution, which, apart from the gradual acquisition of various mutations, could also have involved recombination events. Two different bla TEM-1 gene alleles were precursors of the ESBL genes: bla TEM-1A , which was the ancestor of bla TEM-93 , and bla TEM-1F , from which all the remaining genes originated. The evolution of the bla TEM-1F -related genes most probably consisted of three major separate lineages, one of which, including bla TEM-4 , bla TEM-47 , bla TEM-48 , bla TEM-49 , bla TEM-68 , and bla TEM-94 , was highly structured itself and could have been initiated by the bla TEM-25 gene, identified exclusively in France so far. Plasmid fingerprinting analysis revealed a high degree of diversity of plasmids carrying related bla TEM genes, which suggested either the intense diversification or transposition of bla TEM genes between different plasmids or some contribution of convergent evolution. The results of this study clearly demonstrate that the environment of Polish hospitals has been highly favorable for the rapid evolution of ESBLs.