Affiliation:
1. Area de Bioquímica y Biología Molecular, Universidad de La Rioja, 26006 Logroño, Spain
Abstract
ABSTRACT
TEM-, SHV-, and OXA-type β-lactamases were studied by PCR with 124 ampicillin-resistant (AMP
r
)
Escherichia coli
isolates recovered from foods of animal origin (
n
= 20) and feces of humans (
n
= 49) and healthy animals (
n
= 55). PCR showed that 103 isolates were positive for TEM and negative for SHV and OXA. Three
E. coli
isolates showed a positive reaction for OXA, and one showed a positive reaction for SHV. The remaining 17
E. coli
isolates were negative for the three enzymes by PCR. Fifty-seven of the 103
bla
TEM
amplicons were sequenced. Different molecular variants of
bla
TEM-1
were found in 52 isolates:
bla
TEM-1a
(
n
= 9),
bla
TEM-1b
(
n
= 36),
bla
TEM-1c
(
n
= 6), and
bla
TEM-1f
(
n
= 1). Four inhibitor-resistant TEM (IRT) β-lactamase-encoding genes were also detected:
bla
TEM-30c
(IRT-2),
bla
TEM-34b
(IRT-6),
bla
TEM-40b
(IRT-11), and
bla
TEM-51a
(IRT-15). A new
bla
TEM
gene, named
bla
TEM-95b
, which showed a mutation in amino acid 145 (P→A) was detected. It was found in a food isolate of chicken origin (AMP
r
, amoxicillin-clavulanic acid susceptible). The promoter region in 24
bla
TEM
amplicons was analyzed, and the weak
P3
promoter was found in 23 of them (
bla
TEM-1
in 20 amplicons and
bla
TEM-51a
,
bla
TEM-30c
, and
bla
TEM-95b
in 1 amplicon each). The strong
Pa
/
Pb
promoter was found only in the
bla
TEM-34b
gene. No extended-spectrum β-lactamases were detected. Mutations at position −42 or −32 in the
ampC
gene promoter were demonstrated in 4 of 10
E. coli
isolates for which the cefoxitin MIC was ≥16 μg/ml. Different variants of
bla
TEM-1
and IRT
bla
TEM
genes were found among the AMP
r
E. coli
isolates from foods and the feces of humans and healthy animals, and a new gene,
bla
TEM-95b
(
P3
), was detected.
Publisher
American Society for Microbiology
Subject
Infectious Diseases,Pharmacology (medical),Pharmacology
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