Comparison of UroQuick and KirbyBauer methods to detect ESBLproducing strains' S' Cagnacci, S' Rovet

1
Comparison of Uro-Quick and Kirby-Bauer methods
to detect ESBL-producing strains. S. Cagnacci,
S. Roveta, F. Cavallini, D. L. Rocca, A.
Marchese, E.A.Debbia. Institute of Microbiology,
University of Genoa, Italy.
15th ECCMID, Copenhagen, April 2-5, 2005.
Paper 1885
Methods The Uro-Quick System is an automated
rapid method, introduced by Alifax (Padua,
Italy), for bacteriuria screening which uses
laser-nephelometry (light scattering) to monitor
the growth of bacteria in vials containing broth
(Figure 2). The inoculated vials are incubated at
37C and magnetic stirred bars keep the samples
in suspension and well aerated to promote
bacterial growth. After an opportune time of
incubation the instrument printed the results no
growth and a growth curve like the control are
representative of a susceptible and resistant
strain respectively (Figure 3). A total of 200
strains collected from nosocomial patients were
tested for antibiotic susceptibility by the
Uro-Quick system. About 106 cell/ml were used to
seed 2.5 ml of broth in vials containing
ceftazidime (20 mg/l) and ceftazidime (20 mg/l)
plus clavulanic acid (10 mg/l). After incubation
the results were plotted as groth curves. All
results were confirmed by Kirby-Bauer method.
Control strains included E. coli ATCC 25922, and
a TEM-4 producer.
Results Using an inoculum of 106 cell/ml the
instrument was capable to print out the result
after 5 hours of incubation. Among the pathogens
studied, 46 strains resulted resistant to
ceftazidime (presence of growth). These results
were then compared with those obtained with the
Kirby-Bauer method, and it was found that among
these 46 ceftazidime-resistant clones all were
ESBL-producers, even if 12 showed an
intermediate, and 12 a susceptible antibiotic
phenotype by Kirby-Bauer metod.
Abstract Comparison of Uro-Quick and Kirby-Bauer
methods to detect ESBL-producing strains.S.
Cagnacci, S. Roveta, F. Cavallini, D. Rocca, A.
Marchese, E.A.Debbia. Objectives To evaluate
the Uro-Quick system for detection of
extended-spectrum beta-lactamase (ESBL) in
nosocomial strains that exhibit ceftazidime
resistance phenotype, and/or in isolates
requiring confirmatory tests for the
identification of strains producing these
enzymes. Methods A total of 200 strains
collected from nosocomial patients were tested
for antibiotic susceptibility by the Uro-Quick
system. About 106 cell/ml were used to seed 2.5
ml of broth in vials containing ceftazidime (20
mg/l) and ceftazidime (20 mg/l) plus clavulanic
acid (10 mg/l). After incubation the results were
plotted as growth curves. All results were
confirmed by Kirby-Bauer method. Control strains
included E. coli ATCC 25922, and a TEM-4
producer. Results Using an inoculum of 106
cell/ml the instrument was capable to print out
the result after 5 hours of incubation. Among the
pathogens studied, 46 strains resulted resistant
to ceftazidime (presence of growth). These
results were then compared with those obtained
with the Kirby-Bauer method, and it was found
that among these 46 ceftazidime-resistant clones
all were ESBL-producers, even if 12 showed an
intermediate, and 12 a susceptible antibiotic
phenotype by Kirby-Bauer metod. Conclusion
Present findings suggest that Uro-Quick
represents a useful technology to detect
ESBL-producing strains especially those that
required further confirmatory tests for their
identification. The period of time needed to
achieve the results, in some cases less than 5
hours, is a sure advantageous over the usual
methodologies.
Conclusion Present findings suggest that
Uro-Quick represents a useful technology to
detect ESBL-producing strains especially those
that required further confirmatory tests for
their identification. The period of time needed
to achieve the results, in some cases less than 5
hours, is a sure advantageous over the usual
methodologies.
Introduction and Purpose The Uro-Quick (Figure
1), an automatic instrument used for the
screening and determination of bacteriuria in 3-5
hours, was recently employed to detect antibiotic
resistance in well characterized bacterial
strains and in uropathogens (Roveta et al., 2004)
. In this study Uro-Quick system has been
employed to detect extended-spectrum
beta-lactamase (ESBL) in nosocomial strains that
exhibit ceftazidime resistance phenotype, and/or
in isolates requiring confirmatory tests for the
identification of strains producing these
enzymes.
Figure 2 Light scattering
Figure 1 Uro-Quick
Author for correspondence Eugenio A.
Debbia Institute of Microbiology, University of
Genoa. Largo R. Benzi 10 -16132 Genoa,
Italy. Tel [phone], Fax
39-010-3537698 eugenio.debbia_at_unige.it
Figure 3 Susceptible and resistant strains