Discrepancies in Antimicrobial Susceptibility between the JP2 and the Non-JP2 Genotype of Aggregatibacter actinomycetemcomitans.

Margareta Granlund,Rolf Claesson,Carola Höglund Åberg,Anders Johansson

doi:10.3390/antibiotics11030317

Abstract

The Aggregatibacter actinomycetemcomitans JP2 genotype is associated with high leukotoxin production and severe (aggressive) periodontitis. The aim of this study was to compare the antimicrobial susceptibility of JP2 and non-JP2 genotype strains. Minimal inhibitory concentrations (MICs) of 11 antimicrobials were determined for 160 A. actinomycetemcomitans of serotype a, b, or c, mostly isolated in Sweden or Ghana. MIC distributions for benzylpenicillin and fusidic acid revealed a more susceptible subpopulation for 38 serotype b strains, including the 32 of the JP2 genotype, with a benzylpenicillin MIC range of 0.125–0.5 mg/L. In contrast, benzylpenicillin MIC ≤ 16 mg/L was the estimated 99.5% epidemiological cutoff (ECOFF) of all strains. Beta-lactamase production was not detected. The fusidic acid MIC distribution of 11 strains of Aggregatibacter aphrophilus agreed with that found in non-JP2 strains. Cefotaxime, meropenem, levofloxacin, and trimethoprim–sulfamethoxazole MICs were all ≤0.25 mg/L, while MIC90 values for amoxicillin, azithromycin and tetracycline were 1 mg/L. Metronidazole MICs varied between 0.5 and >256 mg/L. The discrepant findings indicate that A. actinomycetemcomitans may be divided into two separate wild types, with a suggested intrinsic reduced susceptibility for benzylpenicillin in the majority of non-JP2 genotype strains. Possible implications for the treatment of A. actinomycetemcomitans infections are discussed.

Highlights

Aggregatibacter actinomycetemcomitans is a member of the HACEK group, which encompasses Haemophilus species, Aggregatibacter species, Cardiobacterium hominis, Eikenella corrodens, and Kingella species [1]
In a Danish study of bacteremia, Haemophilus species other than H. influenzae were the most common bacteria found within the HACEK group, followed by Aggregatibacter spp
We elucidated the antimicrobial susceptibility of strains of the JP2 and the non-JP2 genotype of A. actinomycetemcomitans

Summary

Introduction

Aggregatibacter actinomycetemcomitans is a member of the HACEK group, which encompasses Haemophilus species, Aggregatibacter species, Cardiobacterium hominis, Eikenella corrodens, and Kingella species [1]. These fastidious Gram-negative bacteria are normal inhabitants of the upper respiratory tract in humans but can cause invasive infections such as infective endocarditis (IE) and abscesses [1–3]. In a Danish study of bacteremia, Haemophilus species other than H. influenzae were the most common bacteria found within the HACEK group, followed by Aggregatibacter spp. In the new classification system based on the staging and grading of periodontitis, the most severe forms of periodontitis are scored stage III–IV [10]

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