Anne B Jensen1,2, Dorte Haubek1, Rolf Claesson3, Anders Johansson4, Niels Nørskov-Lauritsen2. 1. Department of Dentistry and Oral Health, Aarhus University, Aarhus, Denmark. 2. Department of Clinical Microbiology, Aarhus University Hospital, Aarhus, Denmark. 3. Division of Oral Microbiology, Department of Odontology, Faculty of Medicine and Odontology, Umeå University, Umeå, Sweden. 4. Division of Periodontology, Department of Odontology, Faculty of Medicine and Odontology, Umeå University, Umeå, Sweden.
Abstract
AIM: The present study aims to determine the susceptibility of Aggregatibacter actinomycetemcomitans to amoxicillin by investigating a large collection of oral strains of diverse geographical origin. METHODS: Two hundred and fifty-seven A. actinomycetemcomitans strains were serotyped using a multiplex polymerase chain reaction, and minimal inhibitory concentration (MIC) values of amoxicillin were determined using the agar dilution method (range 0.25-8.0 mg/L). The plates were spot-wise inoculated with approximately 104 colony-forming units, incubated in 5% CO2 at 37 C°, and visually inspected after 24 and 48 hr. A MIC ≤ 2.00 mg/L was categorised as susceptible using EUCAST interpretative criteria for Haemophilus species. RESULTS: Amoxicillin MIC values varied from 0.25 mg/L to 2.00 mg/L, and all tested strains, including strains previously reported as resistant, were susceptible to amoxicillin. The MIC50 was 1.00 mg/L and the MIC90 was 2.00 mg/L. CONCLUSION: Meticulous investigation of strains including isolates previously reported as resistant could not confirm the emergence of resistance to β-lactams in A. actinomycetemcomitans. Based on the present in vitro results, amoxicillin can be considered a key oral antimicrobial agent for treatment of A. actinomycetemcomitans.
AIM: The present study aims to determine the susceptibility of Aggregatibacter actinomycetemcomitans to amoxicillin by investigating a large collection of oral strains of diverse geographical origin. METHODS: Two hundred and fifty-seven A. actinomycetemcomitans strains were serotyped using a multiplex polymerase chain reaction, and minimal inhibitory concentration (MIC) values of amoxicillin were determined using the agar dilution method (range 0.25-8.0 mg/L). The plates were spot-wise inoculated with approximately 104 colony-forming units, incubated in 5% CO2 at 37 C°, and visually inspected after 24 and 48 hr. A MIC ≤ 2.00 mg/L was categorised as susceptible using EUCAST interpretative criteria for Haemophilus species. RESULTS:Amoxicillin MIC values varied from 0.25 mg/L to 2.00 mg/L, and all tested strains, including strains previously reported as resistant, were susceptible to amoxicillin. The MIC50 was 1.00 mg/L and the MIC90 was 2.00 mg/L. CONCLUSION: Meticulous investigation of strains including isolates previously reported as resistant could not confirm the emergence of resistance to β-lactams in A. actinomycetemcomitans. Based on the present in vitro results, amoxicillin can be considered a key oral antimicrobial agent for treatment of A. actinomycetemcomitans.