Mechanisms of resistance to expanded-spectrum cephalosporins in Escherichia coli isolates recovered in a Spanish hospital.
OBJECTIVE
To characterize the beta-lactamase genes of the expanded-spectrum cephalosporin-resistant Escherichia coli isolates recovered in a Spanish hospital during the March 2002-March 2003 period.


METHODS
Thirty-four of the 1700 E. coli isolates recovered from unrelated patients in a Spanish hospital showed expanded-spectrum cephalosporin resistance. The presence of genes encoding TEM, SHV, CTX-M, CMY-2-type or FOX beta-lactamases as well as the existence of mutations in the regulatory region of the chromosomal ampC gene were studied by PCR and sequencing in these 34 E. coli isolates.


RESULTS
The following extended-spectrum beta-lactamases (ESBLs) or plasmidic class C beta-lactamase genes were detected (number of isolates): bla(CTX-M-14) (14), bla(CTX-M-9) (4), bla(CTX-M-32) (1), bla(TEM-52) (2), bla(SHV-12) (3) and bla(CMY-2) (2). The remaining eight isolates showed a mutation in the promoter/attenuator region of the ampC chromosomal gene at position -42, in combination with mutations at positions -18, -1 and +58. The bla(TEM-1) gene was also detected in 12 of the ESBL-producing isolates, in both CMY-2-producing isolates and in four of the eight isolates that showed a mutation at position -42 of the ampC promoter. Other mutations in the promoter/attenuator region were detected in association with ESBL or CMY-2 genes, such as the combination -18, -1 and +58, -28 and +58, or +22, +26, +27 and +32. No clonal relationship was found among the CTX-M-producing E. coli isolates by PFGE with XbaI enzyme.


CONCLUSIONS
Approximately 1.5% of the E. coli isolates of our hospital harboured ESBL genes, those of the CTX-M-9 group being the most common ones.
Briñas
Laura
L
Area de Bioquímica y Biología Molecular, Universidad de La Rioja, Madre de Dios, 51, 26006 Logroño, Spain.
Lantero
Marta
M
de Diego
Isabel
I
Alvarez
María
M
Zarazaga
Myriam
M
Torres
Carmen
C
D000900:Anti-Bacterial Agents / Q000494:pharmacology*; D002511:Cephalosporins / Q000494:pharmacology*; D002876:Chromosomes, Bacterial / Q000378:metabolism; D016172:DNA Fingerprinting; D004269:DNA, Bacterial / Q000235:genetics; D015252:Deoxyribonucleases, Type II Site-Specific / Q000378:metabolism; D024881:Drug Resistance, Bacterial / Q000235:genetics*; D016521:Electrophoresis, Gel, Pulsed-Field; D004926:Escherichia coli / Q000187:drug effects* / Q000235:genetics / Q000302:isolation & purification; D004927:Escherichia coli Infections / Q000382:microbiology*; D029968:Escherichia coli Proteins / Q000235:genetics; D005798:Genes, Bacterial; D006761:Hospitals; D006801:Humans; D017720:Molecular Epidemiology; D009154:Mutation; D016133:Polymerase Chain Reaction; D012150:Polymorphism, Restriction Fragment Length; D011401:Promoter Regions, Genetic; D017422:Sequence Analysis, DNA; D013030:Spain; D001618:beta-Lactamases / Q000235:genetics*
D000900:Anti-Bacterial Agents; D002511:Cephalosporins; D004269:DNA, Bacterial; D029968:Escherichia coli Proteins; C025580:endodeoxyribonuclease XBAI; D015252:Deoxyribonucleases, Type II Site-Specific; D001618:beta-Lactamases