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Updated: Mar 11, 2026
High-throughput Detection Method for Influenza Virus
Published on: February 4, 2012
Rise in Haemophilus influenzae With Reduced Quinolone Susceptibility and Development of a Simple Screening Method
Shoji Seyama1, Takeaki Wajima, Yuki Yanagisawa
1From the *Department of Microbiology, School of Pharmacy, Tokyo University of Pharmacy and Life Sciences; †Department of Pediatrics, and ‡Department of Infectious Diseases, Hachioji Medical Center, Tokyo Medical University, Tokyo, Japan.
Background:
β-Lactamase-nonproducing ampicillin-resistant Haemophilus influenzae are prevalent in Japan. Resistance has increased as a consequence of the expanded use of antimicrobial agents, raising concerns about the rise of multidrug (macrolide and fluoroquinolone)-resistant H. influenzae.
Methods:
In this study, we investigated susceptibility to fluoroquinolones in H. influenzae clinical isolates from 2013 to 2014 and identified the amino acid substitutions in quinolone resistance-determining regions of gyrA and parC.
Results:
All isolates (n = 145) were susceptible to fluoroquinolones; however, some showed reduced susceptibility. The minimum inhibitory concentration of levofloxacin for these strains was 0.063-0.5 µg/mL, and the strains harbored the amino acid substitution S84L in GyrA. Such strains have seen a significant increase. Importantly, all mutants from 2014 were isolated from pediatric patients. In addition, we developed a simple polymerase chain reaction-based screening method for detecting isolates with reduced fluoroquinolone susceptibility.
Conclusions:
The mutation in GyrA is important as a first step in the development of fluoroquinolone resistance. Hence, detection of reduced susceptible strains may influence the choice of antimicrobial treatment.
Insights
Ampicillin-resistant Haemophilus influenzae in Japan show increasing resistance to fluoroquinolones. A key GyrA mutation (S84L) indicates reduced susceptibility, necessitating early detection for effective antimicrobial treatment.
Area of Science:
- Microbiology
- Infectious Diseases
- Antimicrobial Resistance
Background:
- Prevalence of β-lactamase-nonproducing ampicillin-resistant Haemophilus influenzae in Japan.
- Increasing antimicrobial resistance due to expanded use of antibiotics.
- Concerns regarding the emergence of multidrug-resistant H. influenzae strains.
Purpose of the Study:
- Investigate fluoroquinolone susceptibility in H. influenzae clinical isolates.
- Identify amino acid substitutions in gyrA and parC associated with resistance.
- Develop a screening method for reduced fluoroquinolone susceptibility.
Main Methods:
- Analysis of 145 H. influenzae clinical isolates from 2013-2014.
- Susceptibility testing for fluoroquinolones.
- Identification of amino acid substitutions in quinolone resistance-determining regions (GyrA and ParC) using molecular methods.
- Development of a PCR-based screening assay.
Main Results:
- All isolates remained susceptible to fluoroquinolones, but some exhibited reduced susceptibility.
- The S84L substitution in GyrA was identified in strains with reduced levofloxacin susceptibility (MIC 0.063-0.5 µg/mL).
- A significant increase in strains with the S84L mutation was observed, particularly in pediatric isolates from 2014.
- A simple PCR-based screening method for detecting reduced fluoroquinolone susceptibility was developed.
Conclusions:
- The GyrA S84L mutation represents an early step in the development of fluoroquinolone resistance in H. influenzae.
- Early detection of reduced susceptibility is crucial for guiding antimicrobial treatment choices.
- Monitoring these mutations is important for public health surveillance of antimicrobial resistance.
