High diversity of extended-spectrum beta-lactamases among clinical isolates of Enterobacteriaceae from Portugal.
OBJECTIVE
To investigate the occurrence and the diversity of Ambler class A ESBLs among Enterobacteriaceae from different Portuguese clinical settings over a 2 year period (2002-04).


METHODS
One hundred and nine extended-spectrum beta-lactamase (ESBL)-producing Enterobacteriaceae isolates from five geographically distant health institutions in Portugal were studied. ESBLs were characterized by isoelectric focussing, PCR and further sequencing. Antibiotic susceptibility testing, transfer of resistance genes and clonal diversity were determined by standard procedures. Plasmid relatedness was established by comparison of random amplified polymorphic DNA (RAPD) patterns.


RESULTS
ESBLs were identified as TEM (46%), SHV (30%), CTX-M (22%) and GES (2%) types; TEM-24, TEM-52, SHV-12 and CTX-M-15 enzymes being the most frequently found. Inter-hospital dissemination of epidemic strains harbouring the most prevalent ESBLs was detected, including the TEM-24-producing Enterobacter aerogenes European epidemic clone. Conjugative transfer of ESBLs was achieved for 67% of isolates and epidemic plasmids containing specific bla genes were detected (bla(CTX-M-15) and bla(TEM-24)). We describe two new ESBLs, SHV-90 (A187T, G238S and E240K) and SHV-91 (P20S and E240K), and a new TEM-type enzyme conferring a phenotype resembling that of a complex mutant TEM beta-lactamase, designated as TEM-154 (M69L and R164S). The broad-spectrum beta-lactamases SHV-26, SHV-36 and TEM-110 were first observed in our country.


CONCLUSIONS
We describe a complex ESBL epidemiology in Portugal, including widespread dissemination of known strains and plasmids coding for TEM-24 and CTX-M-15 enzymes as observed in other European countries.
Machado
Elisabete
E
REQUIMTE, Faculdade de Farmácia, Universidade do Porto, Porto, Portugal.
Coque
Teresa M
TM
Cantón
Rafael
R
Novais
Angela
A
Sousa
João Carlos
JC
Baquero
Fernando
F
Peixe
Luísa
L
D000900:Anti-Bacterial Agents / Q000494:pharmacology; D001426:Bacterial Proteins / Q000235:genetics; D003227:Conjugation, Genetic; D024881:Drug Resistance, Bacterial; D004755:Enterobacteriaceae / Q000187:drug effects / Q000201:enzymology* / Q000302:isolation & purification; D004756:Enterobacteriaceae Infections / Q000453:epidemiology* / Q000382:microbiology*; D022761:Gene Transfer, Horizontal; D006801:Humans; D007525:Isoelectric Focusing; D008826:Microbial Sensitivity Tests; D010957:Plasmids; D016133:Polymerase Chain Reaction / Q000379:methods; D011174:Portugal / Q000453:epidemiology; D001618:beta-Lactamases / Q000145:classification* / Q000235:genetics*
D000900:Anti-Bacterial Agents; D001426:Bacterial Proteins; C473109:beta-lactamase CTX-M-15; D001618:beta-Lactamases