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Determination of the antimicrobial activity of 29 clinically important compounds tested against fastidious HACEK
K C Kugler1, D J Biedenbach, R N Jones
1Department of Pathology, University of Iowa College of Medicine, Iowa City 52242, USA.
Insights
The Etest method effectively determined antimicrobial susceptibility for fastidious HACEK organisms, identifying potent agents like beta-lactamase inhibitor combinations for treating serious infections such as endocarditis.
Area of Science:
- Clinical Microbiology
- Infectious Diseases
- Antimicrobial Susceptibility Testing
Background:
- HACEK (Haemophilus spp., Actinobacillus actinomycetemcomitans, Cardiobacterium hominus, Eikenella corrodens, Kingella spp.) are fastidious bacteria causing severe invasive infections, notably endocarditis.
- Limited data on antimicrobial susceptibility for HACEK organisms complicates treatment choices, especially with newer agents.
- Challenges in susceptibility testing methods for these rare isolates hinder therapeutic decision-making.
Purpose of the Study:
- To evaluate the Etest method for antimicrobial susceptibility testing of HACEK group organisms.
- To identify effective antimicrobial agents against HACEK strains for potential endocarditis treatment.
- To assess the utility of various antimicrobial classes against these fastidious pathogens.
Main Methods:
- Forty-two HACEK strains were tested using the Etest method.
- Susceptibility was assessed against 29 different antimicrobial agents.
- The Etest method was employed for its suitability with fastidious bacteria.
Main Results:
- Most tested antimicrobial agents showed activity against HACEK organisms.
- Highest potency was observed with beta-lactamase inhibitor combinations, advanced cephems (third/fourth-generation), meropenem, fluoroquinolones, and rifampin.
- The Etest method proved effective for determining susceptibility in these fastidious species.
Conclusions:
- The Etest method is a reliable tool for HACEK organism susceptibility testing.
- Multiple therapeutic options, including parenteral and oral step-down therapies, are feasible.
- Accurate susceptibility testing is crucial for guiding HACEK infection treatment.
Abstract:
HACEK group organisms are very fastidious organisms (Haemophilus spp., Actinobacillus actinomycetemcomitans, Cardiobacterium hominus, Eikenella corrodens, Kingella spp.) that can produce serious invasive infections such as endocarditis. Problems with susceptibility testing methods and their rarity of isolation limit available information of therapeutic choices, particularly among newer antimicrobial agents. Forty-two HACEK strains were tested by the Etest (AB BIODISK, Solna, Sweden) method against 29 antimicrobial agents. Nearly all compounds exhibited activity with best potency observed among the tested beta-lactamase inhibitor combinations, "third- or fourth-generation" cephems, meropenem, fluoroquinolones, and rifampin. Numerous therapeutic options appear possible for initial parenteral treatment followed by oral "step-down" or switch therapy. Each case of HACEK infection therapy should be guided by accurate susceptibility tests, for which the Etest seems preferred for these fastidious species.
