Table 1. Isolation rate of Escherichia coli strains resistant to ceftaxime, mcr-1 bearing strains, bla NDM bearing strains and strains harbouring both mcr-1 and bla NDM genes, Shenzhen, 2015–2017 (n = 2,137).
| Year | Number of food samples | Cefotaxime-resistant E. coli isolates | mcr-1-bearing E. coli | bla NDM-bearing E. coli, with or without mcr-1 | |||||||||||||
|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|
| Total | Isolation rate (%)a | Pork | Beef | Chicken | Shrimp | Total | mcr-1 positivity rate (%)a | Total | bla NDM positivity rate (%)a | Number of mcr-1-positive strains | bla NDM/mcr-1 positivity rate (%) | ||||||
| n | % | n | % | n | % | n | % | ||||||||||
| 2015 | 747 | 385 | 52 (A) | 248 | 57 | 33 | 46 | 97 | 75 | 7 | 6 | 98 | 25 (B) | 1 | 0.3 (E) | 0 | 0 |
| 2016 | 1,019 | 570 | 56 (A) | 319 | 52 | 61 | 53 | 168 | 86 | 22 | 12 | 207 | 36 (C) | 5 | 1 (E) | 0 | 0.2 |
| 2017 | 371 | 211 | 57 (A) | 143 | 65 | 13 | 30 | 50 | 88 | 5 | 10 | 97 | 46 (D) | 36 | 17 (F) | 5 | 2 |
| Total | 2,137 | 1,166 | 55 | 710 | 60 | 107 | 47 | 315 | 82 | 34 | 10 | 402 | 34 | 42 | 4 | 5 | 0.4 |
a Percentage was calculated by dividing the number of E. coli isolates carrying the indicated resistance genes by the total number of cefotaxime-resistant E. coli isolates obtained in each year; percentages labelled with the same letter in brackets indicated that no significant difference was observed between two variants; percentages labelled with different letters indicated that a significant difference was observed between two variants (p < 0.05); (B) vs (C): p = 0.000; (C) vs (D): p = 0.014; (B) vs (D): p = 0.000; (B) vs (C) vs (D): p = 0.000; (E) vs (F): p = 0.000.