Resistance to Different Antibiotics
Ampicillin resistance due to plasmid-mediated TEM-1 β-lactamase production was first noted in 1972, and is now widespread, ranging from 3% in Germany to 65% in South Korea in lower respiratory and blood specimens. The prevalence of β-lactamase-producing strains rose in the 1990s, followed by a subsequent decline in the 2000s in the USA, Canada, Japan and Spain.75 In 1981, Rubin et al. reported a novel β-lactamase in H. influenzae, later called ROB-1.76 The recent prevalence of this enzyme varies greatly (from 4% to 30%) and was found with the highest frequency in Mexico and USA.
β-Lactamase-negative, ampicillin-resistant (BLNAR) strains are associated with changes in penicillin-binding proteins, especially PBP 3. This form of ampicillin resistance appears to be globally rare (<0.5%) but was reported locally at much higher rates (10–40%) in recent surveys from Europe and Japan, possibly due to differences in the methods and definitions used.75 Cephalosporins and amoxicillin–clavulanate remain very active (>99% sensitivity), as are fluoroquinolones, tetracyclines, rifampicin and chloramphenicol. Rates of chloramphenicol resistance in excess of 10% were occasionally found in some Latin American and Asian countries. Co-trimoxazole resistance rates vary markedly by region, with the highest rates reported from Latin America, the Middle East and Spain (about 30%), followed by Eastern Europe and North America (10–20%).
