Volume 23, Number 9—September 2017
Research Letter
Antimicrobial Drug–Resistant Shiga Toxin–Producing Escherichia coli Infections, Michigan, USA
Table
Antimicrobial drug resistance in 353 clinical Shiga toxin–producing Escherichia coli isolates, by serotype, Michigan, USA, 2010–2014*
Serotype | No. isolates | No. (%) isolates |
|||
---|---|---|---|---|---|
Any resistance | Ampicillin resistance | Ciprofloxacin resistance | SXT resistance | ||
O157 |
146 |
8 (5.5) |
7 (4.8) |
0 (0) |
5 (3.4) |
Non-O157 |
207 |
23 (11.1) |
19 (9.2) |
1 (0.5) |
9 (4.3) |
O26 |
53 |
4 (7.6) |
4 (7.6) |
0 (0) |
1 (1.9) |
O45 |
50 |
6 (12.0) |
5 (10.0) |
0 (0) |
2 (4.0) |
O103 |
75 |
6 (8.0) |
5 (6.7) |
1 (1.3) |
4 (5.3) |
O111 | 29 | 7 (24.1) | 5 (17.2) | 0 (0) | 2 (6.9) |
*We tested 358 isolates by disk diffusion for resistance to ampicillin (10 μg in disk), SXT (25 μg in disk), and ciprofloxacin (5 μg in disk). MICs were determined by using Etest. Strains were classified as resistant or susceptible according to Clinical Laboratory Standards Institute guidelines; E. coli ATCC 25922 was used as a control. Five isolates had unknown serotypes and were excluded from analysis. Isolate numbers for individual antibiotics do not always add up to the total number of isolates with any resistance because some isolates were resistant to >1 drug. SXT, trimethoprim/
sulfamethoxazole.