APMIS 112: 815–37, 2004 Copyright C APMIS 2004 Printed in Denmark . All rights reserved ISSN 0903-4641 Genetic methods for detection of antimicrobial resistance ARNFINN SUNDSFJORD, 1, 2, 3 GUNNAR S. SIMONSEN, 2, 3 BJØRG C. HALDORSEN, 2 HÅKON HAAHEIM, 2 STIG-OVE HJELMEVOLL, 2 PIA LITTAUER 2 and KRISTIN H. DAHL 1,2 1 Department of Microbiology and Virology, University of Tromsø, 2 Reference Centre for Detection of Antimicrobial Resistance, Department of Microbiology, University Hospital of Northern-Norway and 3 Division of Infectious Disease Control, Norwegian Institute of Public Health, Oslo, Norway Sundsfjord A, Simonsen GS, Haldorsen BC, Haaheim H, Hjelmevoll SO, Littauer P, Dahl KH. Gen- etic methods for detection of antimicrobial resistance. APMIS 2004;112:815–37. Accurate and rapid diagnostic methods are needed to guide antimicrobial therapy and infection con- trol interventions. Advances in real-time PCR have provided a user-friendly, rapid and reproducible testing platform catalysing an increased use of genetic assays as part of a wider strategy to minimize the development and spread of antimicrobial-resistant bacteria. In this review we outline the principal features of genetic assays in the detection of antimicrobial resistance, their advantages and limitations, and discuss specific applications in the detection of methicillin-resistant Staphylococcus aureus, glyco- peptide-resistant enterococci, aminoglycoside resistance in staphylococci and enterococci, broad-spec- trum resistance to b-lactam antibiotics in gram-negative bacteria, as well as genetic elements involved in the assembly and spread of antimicrobial resistance. Key words: Genetic methods; antimicrobial resistance. Arnfinn Sundsfjord, Department of Microbiology and Virology, Faculty of Medicine, University of Tromsø, N-9037 Tromsø, Norway. e-mail: arnfinn.sundsfjord/fagmed.uit.no THE PROBLEM Antimicrobial susceptibility testing of bacterial pathogens is one of the primary functions of a diagnostic microbiology laboratory. Individual results have important therapeutic implications for the patient. Empiric treatment schemes for infectious diseases are based on accumulated susceptibility testing data gathered at the local, regional, or national level. Finally, careful de- tection of resistant bacteria provides a funda- mental basis for infection control measures and antimicrobial surveillance systems. The global emergence and spread of anti- microbial resistance poses a major risk for hu- man health due to the impact on morbidity, Invited Review. 815 mortality, and health care costs (33, 49, 106, 182). The Nordic countries are considered a low-prevalence area for antimicrobial resistance (40, 47, 116, 153, 160). However, in general the Nordic countries are experiencing a slow in- crease in the prevalence of several types of re- sistance and in particular the MRSA-situation is worrisome (50, 51, 110). Moreover, imported cases of multiresistant pathogens illustrate the dynamic situation with respect to epidemic mul- tiresistant bacterial pathogens or resistance genes that do not require visas when crossing country borders (63). Thus, we need accurate and rapid diagnostic methods to guide anti- microbial therapy and infection control inter- ventions. The objectives of this paper are to examine the rationale for using genetic methods in the detection of antimicrobial resistance, their advantages and limitations, to address some of