Table 1.

Prevalence of resistance ($f_R$) and Kendall’s rank correlation coefficient tau (SI Appendix, Supporting Text 4) for the relationship between serotype mean duration of carriage and resistance

Antibiotic	Dataset	$f_R$	tau (95% CI)	P
Penicillin	Massachusetts	0.39	0.34 (− 0.04, 0.61)	0.045
Penicillin	Malawi	0.21	0.49 (− 0.09, 0.79)	0.035
Penicillin	Maela	0.49	0.46 (0.27, 0.58)	8.6 $\times$ 10-6
Penicillin	Combined	—	—	2.4 $\times$ 10-6
Co-trimoxazole	Malawi	0.46	− 0.14 (− 0.62, 0.41)	0.70
Co-trimoxazole	Maela	0.81	0.22 (0.03, 0.39)	0.012
Co-trimoxazole	Combined	—	—	0.049
Trimethoprim	Massachusetts	0.14	0.38 (0.01, 0.64)	0.027
Erythromycin	Massachusetts	0.19	0.34 (− 0.04, 0.61)	0.045
Ceftriaxone	Massachusetts	0.13	0.35 (− 0.03, 0.62)	0.047

Number of isolates and serotypes for which carriage duration could be calculated: Massachusetts, 180 and 19; Malawi, 300 (Materials and Methods) and 9; and Maela, 2,923 and 51. P values are one-tailed, which is why 95% CIs sometimes overlap zero for P < 0.05. Combined P values were calculated using Fisher’s method for all three datasets for penicillin and Malawi and Maela for co-trimoxazole (we treated trimethoprim and co-trimoxazole as different drugs). Bold P values are below 0.05. Values of tau for antibiotics in the Massachusetts dataset are similar because there is a strong association between resistance to different antibiotics (e.g., odds ratio for penicillin and erythromycin nonsensitivity: 10; 95% CI: 6–21).