Antibiotic susceptibility of invasive Haemophilus influenzae strains in Canada

Area of Science:

• Medical Microbiology
• Infectious Diseases
• Antimicrobial Resistance

Background:

• Haemophilus influenzae is a significant cause of invasive bacterial infections.
• Antibiotic resistance in H. influenzae poses a growing public health concern.
• Monitoring antimicrobial susceptibility patterns is crucial for effective treatment.

Purpose of the Study:

• To analyze antibiotic susceptibility trends of invasive Haemophilus influenzae isolates in Canada.
• To identify changes in resistance patterns, particularly to ampicillin, over a 17-year period.

Main Methods:

• Retrospective analysis of Canadian invasive H. influenzae isolates collected from 1990 to 2006.
• Antimicrobial susceptibility testing, including assessment of beta-lactamase production.
• Categorization of resistance and intermediate susceptibility to ampicillin.

Main Results:

• Out of 42 examined strains, 17.8% showed ampicillin resistance due to beta-lactamase production.
• 5.5% of strains were beta-lactamase negative and ampicillin intermediate.
• 2.5% of strains exhibited intermediate susceptibility to a 2-microg ampicillin disk.

Conclusions:

• A notable increase in beta-lactamase-negative ampicillin-intermediate H. influenzae strains was observed.
• These findings highlight evolving resistance mechanisms and the need for ongoing surveillance.
• Updated treatment guidelines may be necessary to address changing susceptibility profiles.