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[Antibiotic sensitivity of Haemophilus influenzae clinically isolated in the Sendai area]
Abstract:
Antibiotic sensitivity of H. influenzae collected from 8 hospital laboratories in the Sendai area during Jan. and Apr., 1984 were determined. One hundred and eighty-seven strains of H. influenzae isolated from different infectious sites were tested for their susceptibility to several representative antibiotics. Twenty-six strains (13.9%) of the isolates were beta-lactamase positive and none of these strains could be serotyped because of a lack of capsules. It was remarkable that beta-lactamase positives strains were rather common in infants under 1 year of age (4 from 23 strains, 17.4%). Minimum inhibitory concentrations (MICs) of antibiotics against H. influenzae revealed that most beta-lactamase negative strains were highly sensitive to both ampicillin and amoxicillin (AMPC), while their MICs to beta-lactamase positive strains were widely distributed from 1.56 (3.13) to more than 100 micrograms/ml. BRL 25000, a formulation of AMPC and clavulanic acid, inhibited the growth of all beta-lactamase positive strains at concentrations of 1.56 micrograms/ml or less. Among cephalosporins, the sensitivity to drugs did not differ between beta-lactamase negative and positive strains. It was also noteworthy that 7 strains (3.8%) of the isolated H. influenzae were resistant to chloramphenicol, and 2 of them were beta-lactamase positive. The most active drug against H. influenzae, therefore, seemed to be the third generation of cephalosporins, especially cefmenoxime which was extremely active to all the strains tested.
Insights
Antibiotic resistance in Haemophilus influenzae is a growing concern, particularly beta-lactamase positive strains. Cefmenoxime demonstrated excellent activity against all tested strains, offering a promising treatment option.
Area of Science:
- Microbiology
- Infectious Diseases
- Pharmacology
Background:
- Haemophilus influenzae is a significant pathogen causing various infections.
- Antibiotic resistance, especially beta-lactamase production, poses a challenge in treating H. influenzae infections.
- Understanding antibiotic susceptibility patterns is crucial for effective treatment strategies.
Purpose of the Study:
- To determine the antibiotic sensitivity of H. influenzae strains isolated from clinical samples in the Sendai area.
- To evaluate the prevalence of beta-lactamase producing strains and their resistance patterns.
- To identify the most effective antibiotics against H. influenzae, including beta-lactamase positive strains.
Main Methods:
- Collected 187 strains of H. influenzae from 8 hospital laboratories.
- Tested susceptibility to representative antibiotics using Minimum Inhibitory Concentration (MIC) assays.
- Identified beta-lactamase positive strains and assessed resistance to ampicillin, amoxicillin, clavulanic acid combinations, cephalosporins, and chloramphenicol.
Main Results:
- 13.9% of H. influenzae isolates were beta-lactamase positive, with higher prevalence in infants under 1 year.
- Beta-lactamase negative strains were sensitive to ampicillin and amoxicillin, while positive strains showed wide-ranging resistance.
- BRL 25000 (amoxicillin/clavulanic acid) effectively inhibited beta-lactamase positive strains.
- 7 strains (3.8%) were resistant to chloramphenicol.
- Third-generation cephalosporins, particularly cefmenoxime, showed high activity against all tested strains.
Conclusions:
- Beta-lactamase production is a significant factor in H. influenzae antibiotic resistance.
- Amoxicillin/clavulanic acid is effective against beta-lactamase positive strains.
- Cefmenoxime is a highly effective antibiotic against a broad spectrum of H. influenzae isolates, including resistant strains.