Characterization of β-Lactam-resistant Bacteroides fragilis Isolates by Use of PCR Fingerprinting

Abstract PCR fingerprinting was used for characterization of 35 β-lactam-resistant Bacteroides fragilis strains isolated in Sweden and Hungary. Ten B. fragilis strains showed unique PCR fingerprints by use of the M13 core primer. Their main product was a DNA fragment with a length of 2000-bp which was absent in the other 25 strains and the reference strain B. fragilis ATCC 25285. The 2000-bp fragment from four imipenem-resistant strains gave rise to positive reactions in a specific PCR for detection of ccrA . Printed by the T3B primer, five B. fragilis strains, including the imipenem-resistant strains showed unique PCR fingerprints. The investigated imipenem-resistant strains produced carbapenem-hydrolysing metallo-β-lactamases. The study indicates that the unique PCR fingerprinting profiles shown in highly β-lactam resistant B. fragilis strains are correlated to antimicrobial resistance. The PCR fingerprinting technique is a useful tool for differentiation of Bacteroides fragilis strains with high-level β-lactam resistance.