Susceptibility of Canadian isolates of Haemophilus influenzae, Moraxella catarrhalis and Streptococcus pneumoniae to oral antimicrobial agents

• Published in: International journal of antimicrobial agents 2001-06, Vol.17 (6), p.457-464
• Main Authors: Blondeau, J.M, Vaughan, D, Laskowski, R, Borsos, S
• Format: Article
• Language: English
• Subjects: Administration, Oral; Anti-Bacterial Agents - administration & dosage; Anti-Infective Agents - administration & dosage; Antibacterial agents; Antibiotics. Antiinfectious agents. Antiparasitic agents; Antimicrobial agents; Bacteriology; beta-Lactamases - metabolism; Biological and medical sciences; Canada; Community-Acquired Infections - drug therapy; Community-Acquired Infections - microbiology; Drug Resistance, Microbial; Epidemiology; Fluoroquinolones; Fundamental and applied biological sciences. Psychology; Haemophilus Infections - drug therapy; Haemophilus Infections - microbiology; Haemophilus influenzae; Haemophilus influenzae - drug effects; Haemophilus influenzae - enzymology; Haemophilus influenzae - isolation & purification; Humans; Medical sciences; Microbiology; Moraxella (Branhamella) catarrhalis - drug effects; Moraxella (Branhamella) catarrhalis - enzymology; Moraxella (Branhamella) catarrhalis - isolation & purification; Moraxella catarrhalis; Neisseriaceae Infections - drug therapy; Neisseriaceae Infections - microbiology; Pharmacology. Drug treatments; Pneumococcal Infections - drug therapy; Pneumococcal Infections - microbiology; Respiratory Tract Infections - drug therapy; Respiratory Tract Infections - microbiology; Respiratory tract pathogens; Streptococcus pneumoniae; Streptococcus pneumoniae - drug effects; Streptococcus pneumoniae - enzymology; Streptococcus pneumoniae - isolation & purification
• ISSN: 0924-8579; 1872-7913
• DOI: 10.1016/S0924-8579(01)00334-X

We measured the susceptibility of Canadian isolates of three respiratory tract pathogens ( Haemophilus influenzae, Moraxella catarrhalis and Streptococcus pneumoniae) to several currently approved antimicrobial agents by two different methods. We also measured the susceptibility of isolates to seven fluoroquinolones. Beta-lactamase was produced by 123/566 (21.7%) of H. influenzae isolates compared with 178/200 (89%) of M. catarrhalis isolates. For S. pneumoniae 83/374 (22.2%) isolates were penicillin resistant and of these 2.1% (8/374) showed high level resistance (MIC≥2 mg/l). Regardless of methodology, all fluoroquinolones were highly active against H. influenzae (MIC 90 ≤0.031 mg/l) and M. catarrhalis (MIC 90 ≤0.064 mg/l) isolates. Susceptibility of H. influenzae to cefuroxime and amoxycillin/clavulanic acid was 99–100% whereas 84–85.5% were susceptible to cefaclor and cefprozil. Azithromycin susceptibility ranged from 82.6 to 99.2% depending on the method. M. catarrhalis isolates were uniformly susceptible to all agents tested except amoxycillin. Cross-resistance in S. pneumoniae to all non-quinolone agents was concurrent with increasing penicillin resistance as shown by increasing MIC 90 values. For the fluoroquinolones tested, the rank order of potency based on MIC 90 values was as follows: gemifloxacin (0.031–0.063 mg/l), trovafloxacin (0.125 mg/l), moxifloxacin (0.125–0.25 mg/l), grepafloxacin (0.125–0.25 mg/l), gatifloxacin (0.5 mg/l), levofloxacin (1 mg/l) and ciprofloxacin (2 mg/l). Our study confirms either a high or increasing prevalence of antimicrobial resistant respiratory pathogens in Canada and also compares the new and old fluoroquinolones and their potential role as therapy for community-acquired infections. The prevalence of β-lactamase positive H. influenzae may have decreased from levels reported in previous studies.