Question 8

What are the resistance rates for the most common ABECB pathogens and is this changing? If so, what trends in resistance patterns have been noted, and what global differences have been noted in resistance patterns?

Drug resistance has increased sharply among community-acquired respiratory pathogens in the United States, with β-lactamase production detected in 40% of H. influenzae and more than 95% of M. catarrhalis isolates (8). In addition, 10% of pneumococci are highly resistant to both penicillin and macrolide antibiotics. Reduced susceptibility to penicillin as high as 40% has been reported from U.S. surveillance studies (9). In Europe, reported rates of penicillin resistance for S. pneumoniae range from 7.4% in Austria to more than 40% in France and Spain. Macrolide-resistance in this organism varied from approximately 5% in Austria to 41% in France (10). Countries with high rates of penicillin resistance (Spain and France) also demonstrated high levels of cross-resistance to azithromycin (57.7% and 36.9%) and co-trimoxazole (57.7% and 36.9%). As reported in both countries, penicillin-resistant S. pneumoniae (PRSP) isolates exhibit decreased susceptibility to other non-β-lactam antibiotic classes. Worldwide, 85-100% of M. catarrhalis isolates are β-lactamase positive and, hence, ampicillin- and amoxicillin-resistant; similar patterns of β-lactamase production and antimicrobial resistance have been observed among H. influenzae and S. pneumoniae isolates worldwide. In recent years, emergence of fluoroquinolone resistance and therapeutic failures has been reported, particularly with the older agents of this class. Studies in the United States report an increase from 2.6 to 3.8% in the prevalence of ofloxacin-resistant S. pneumoniae. Surveys from Hong Kong have reported 5.5% of the isolates resistant to levofloxacin and 12.1% resistant to ciprofloxacin (11). In Canada, a 2.9% prevalence rate of fluoroquinolone-resistant streptococci has been reported among adults (12).