Variations in the prevalence of strains expressing an extended-spectrum
beta-lactamase phenotype and characterization of isolates from Europe,
the Americas and the Western Pacific region
To evaluate the prevalence of extended-spectrum beta -lactamase
(ESBL)-producing strains among species of Enterobacteriaceae, a
microdilution susceptibility test was performed with strains of
Klebsiella pneumoniae, Escherichia coli, Proteus mirabilis, and
Salmonella species that were isolated as part of the SENTRY project. The
highest percentage of ESBL phenotype (defined as a minimum inhibitory
concentration [MIC] greater than or equal to2 mug/mL for ceftazidime,
ceftriaxone, or aztreonam) was detected among K. pneumoniae strains from
Latin America (45%), followed by those from the Western Pacific region
(25%), Europe (23%), the United States (8%), and Canada (5%). P.
mirabilis and E. coli strains for which MICs of extended-spectrum
cephalosporins or monobactams were elevated also were more prominent in
Latin America. Testing with ceftazidime revealed more isolates with
elevated MICs than did testing with ceftriaxone or aztreonam. ESBL
strains showed high levels of co-resistance to aminoglycosides,
tetracycline, trimethoprim-sulfamethoxazole, and ciprofloxacin. Imipenem
remains highly effective against ESBL strains. Organisms expressing an
ESBL are widely distributed worldwide, although prevalence rates are
significantly higher in certain geographic regions