Variety of beta-lactamases produced by amoxicillin-clavulanate-resistant Escherichia coli isolated in the northeastern United States.
This study analyzed the enzymatic basis and molecular epidemiology of amoxicillin-clavulanate-resistant Escherichia coli isolated by the microbiology laboratory of a United States tertiary care hospital. From October 1998 to December 1999, all E. coli isolates were screened for ampicillin-sulbactam resistance. Of 283 isolates that tested resistant to ampicillin-sulbactam, 69 unique patient isolates were also resistant to amoxicillin-clavulanate by disk diffusion testing (zone diameter </= 13 mm). These amoxicillin-clavulanate-resistant E. coli isolates underwent agar dilution testing, pulsed-field gel electrophoresis, PCR analysis, and isoelectric focusing. The mean age of study patients was 52 years; 78% were female. Among the isolates, 12 were nosocomial (rate of amoxicillin-clavulanate resistance = 4.7%) and 57 were community acquired (rate of amoxicillin-clavulanate resistance = 2.8%). No predominant strain was identified. By agar dilution testing, 67 isolates were nonsusceptible (39 resistant and 28 intermediate) to amoxicillin-clavulanate and 37 were piperacillin-tazobactam resistant but only 8 were ceftazidime resistant (ceftazidime MIC >/= 32 micro g/ml). Two isolates were susceptible to amoxicillin-clavulanic acid by agar dilution, although they were resistant by disk diffusion testing. The distribution of beta-lactamases was as follows: the TEM type alone was found in 52 isolates, the AmpC type was found in 4 isolates (2 identified as containing CMY-2), the TEM type and CMY-2 were found in 2 isolates, and the OXA type was found in 1 isolate. Also, there was one isolate with the TEM type and the SHV type and one with the TEM type and a second, unidentified enzyme. Among the isolates with TEM-type enzymes, two extended-spectrum beta-lactamase-producing isolates were identified but two isolates with inhibitor-resistant TEM (IRT) enzymes (one with TEM-34 [IRT-6] and the other with a novel enzyme [tentatively assigned the designation TEM-122]) were more interesting.
Kaye
Keith S
KS
Beth Israel Deaconess Medical Center and Harvard Medical School, Boston, Massachusetts 02215, USA. Kaye0001@mc.duke.edu
Gold
Howard S
HS
Schwaber
Mitchell J
MJ
Venkataraman
Lata
L
Qi
Youlin
Y
De Girolami
Paola C
PC
Samore
Matthew H
MH
Anderson
Greg
G
Rasheed
J Kamile
JK
Tenover
Fred C
FC
D000293:Adolescent; D000368:Aged; D019980:Amoxicillin-Potassium Clavulanate Combination / Q000494:pharmacology*; D003470:Culture Media; D016521:Electrophoresis, Gel, Pulsed-Field; D004926:Escherichia coli / Q000187:drug effects / Q000201:enzymology* / Q000235:genetics; D004927:Escherichia coli Infections / Q000453:epidemiology; D005260:Female; D005798:Genes, Bacterial / Q000235:genetics; D006801:Humans; D007525:Isoelectric Focusing; D008297:Male; D008875:Middle Aged; D017720:Molecular Epidemiology; D009511:New England / Q000453:epidemiology; D010403:Penicillin Resistance; D010641:Phenotype; D020133:Reverse Transcriptase Polymerase Chain Reaction; D001618:beta-Lactamases / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*
D003470:Culture Media; D019980:Amoxicillin-Potassium Clavulanate Combination; D001618:beta-Lactamases