Biofilm Formation and Antibiotic Resistance Phenotype of Helicobacter pylori Clinical Isolates

Abstract: We evaluated biofilm formation of clinical Helicobacter pylori isolates from Indonesia and
its relation to antibiotic resistance. We determined the minimum inhibition concentration (MIC) of
amoxicillin, clarithromycin, levofloxacin, metronidazole and tetracycline by the Etest to measure the
planktonic susceptibility of 101 H. pylori strains. Biofilms were quantified by the crystal violet method.
The minimum biofilm eradication concentration (MBEC) was obtained by measuring the survival
of bacteria in a biofilm after exposure to antibiotics. The majority of the strains formed a biofilm
(93.1% (94/101)), including weak (75.5%) and strong (24.5%) biofilm-formers. Planktonic resistant and
sensitive strains produced relatively equal amounts of biofilms. The resistance proportion, shown by
theMBECmeasurement,washigherinthestrongbiofilmgroupforallantibioticscomparedtotheweak
biofilm group, especially for clarithromycin (p = 0.002). Several cases showed sensitivity by the MIC
measurement, but resistance according to the MBEC measurements (amoxicillin, 47.6%; tetracycline,
57.1%; clarithromycin, 19.0%; levofloxacin, 38.1%; and metronidazole 38.1%). Thus, biofilm formation
may increase the survival of H. pylori and its resistance to antibiotics. Biofilm-related antibiotic
resistance should be evaluated with antibiotic susceptibility.