Antibiotic | Organism | Annual rate of susceptibility change | ||
IRR† 95% CIs | Likelihood ratio test p value | No. of observations | ||
Ampicillin/amoxacillin*Adjusted for age group and sex | All organisms | 0.98 (0.98 to 0.99) | <0.0001§ | 55 176 |
Tetracyclines*Adjusted for source and sex | H influenzae | 1.00 (1.00 to 1.00) | ||
S aureus | 1.00 (0.99 to 1.00) | <0.0001 | 69 913 | |
S pneumoniae | 0.99 (0.98 to 1.00) | |||
Co-amoxiclav*Adjusted for age group and sex | H influenzae | 1.00 (1.00 to 1.00) | ||
S aureus† | 1.09 (1.06 to 1.12) | <0.0001 | 57 895 | |
S pneumoniae | 1.00 (0.99 to 1.00) | |||
Ciprofloxacin*Adjusted for age group, source and sex | H influenzae | 1.00 (1.00 to 1.00) | <0.0001 | 34 799 |
S aureus | 1.09 (1.07 to 1.11) | |||
S pneumoniae | – | |||
Macrolides‡*Adjusted for age group and source | H influenzae | 0.90 (0.87 to 0.92) | ||
S aureus | 1.01 (1.00 to 1.02) | <0.0001 | 53 934 | |
S pneumoniae | 1.00 (0.99 to 1.00) |
↵* IRRs estimated using Poisson regression models with robust standard error. All models were adjusted for seasonal variation (calendar quarter) and laboratory region as well as age group, sex and isolate source where indicated.
↵† Benzyl-penicillin used as a proxy for co-amoxiclav.
↵‡ Combined susceptibility results for azithromycin, erythromycin and clarithromycin.
↵§ Likelihood ratio test p value refers to the significant trend across all organisms rather than for the interaction. All the other p values outlined in the table refer to the interaction between organism and year.