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Abstract

Background: Wide-spread of β-lactamase-producing (ESBL) Enterobacteriaceae is the contemporary worldwide problem. For
better results in infection prevention and therapy antimicrobial-resistance surveillance is needed.
Aim: To compare results of different β-lactamases phenotypic screening and confirmatory tests (screening disks, combined
disks and gradient strips) used in the clinical microbiology laboratory.
Methods: Altogether, 171 strains of bacteria (78 Escherichia coli; 93 Klebsiella pneumoniae) with decreased sensitivity to third
generation cephalosporines were enrolled the study. Clavulanic acid and cloxacillin gradient strips (Liofilchem) and combined
disks from companies Rosco and MAST were used to determine the mechanisms of resistance.
Results: The most frequent β-lactamase was ESBLA. Outcome of all used three tests showed the matching ESBLA in 70 of 152
any positive cases got from different tests that were 41% of all strains. There were no differences in determining of ESBLA in
comparing MAST and Rosco tests, but the gradient strips showed statistically more ESBLA (p=0.02 and <0.001, respectively)
and ESBLAM strains (p<0.01 and 0.024) in comparing with Rosco and MAST tests. The MAST tests showed more ESBLM
strains in comparing with Rosco (p<0,001). Similar results were only three ESBLM strains by using all three tests and for
ESBLAM strains there were no matching results. With all three tests two strains gave similarly negative results (1%).
Conclusions: Usage of different phenotypic tests gives different results. Due to the price and work load, it would be beneficial
to use the combined discs of MAST. However, until there is no molecular confirmation, we could not give recommendations.

Biography

Ülle Parm is a Lecturer of infectious diseases, epidemiology and hospital infections in Tartu Health Care College (Estonia) and scientist in Institute of Microbiology
in University of Tartu. Several text books about these topics for students have been published in Estonia. Numerous publications and presentations in international
scientific conferences have been done. The mean subject of research work has been associated with development of rectal and nasopharyngeal microbiota in
relation to infection in neonates who needs intensive care. Also, the other branches of study have been in interest: e.g. the prevalence of Lyme borreliosis in
Estonia and problems with laboratory diagnostics; contamination of gowns and devices (including cell-phones) that hospital staff uses and association with hygienic
aspects; the ESBL strains in hospitals etc. She is also the member of Estonian Society for Infection Control (ESIC).