TABLE 2.
Resistance to individual antibiotics and prevalence of selected resistance genes in German S. Saintpaul isolates (n = 55)a
| Antimicrobialb | No. (%) of resistant isolates | Resistance gene(s) | Isolates containing resistance gene(s) |
|
|---|---|---|---|---|
| No. (%) | Origin (no. of isolates)c | |||
| β-Lactams | ||||
| Ampicillin | 45 (82) | blaPSE-1 | 1 (2) | G2 (1) |
| blaOXA-1-like | 0 | |||
| blaTEM-1-like | 45 (100) | G1 (16), G2 (15), G3 (14) | ||
| blaCTX-M | 0 | |||
| blaSHV | 0 | |||
| Aminoglycosides | ||||
| Streptomycin | 49 (89) | strA | 3 (6) | G3 (3) |
| aadA1-like | 48 (98) | G1 (16), G2 (15), G3 (17) | ||
| aadA2 | 42 (86) | G1 (16), G2 (15), G3 (11) | ||
| Gentamicin | 43 (78)d | aacC2 | 0 | |
| aacC4 | 0 | |||
| aadBe | 42 (98) | G1 (16), G2 (15), G3 (11) | ||
| armA | 0 | |||
| Othersf | 1 (2) | G3 (1) | ||
| Kanamycin | 42 (76)d | aphA1 | 2 (5) | G3 (2) |
| aphA2 | 0 | |||
| aac(6)-1b | 0 | |||
| Phenicols | ||||
| Chloramphenicol | 5 (9) | catA1 | 3 (3/5)g | G3 (3) |
| cmlA1 | 2 (2/5)g | G2 (2) | ||
| floR | 0 | |||
| Folate pathway inhibitors | ||||
| Sulfamethoxazole | 49 (89) | sul1 | 48 (98) | G1 (16), G2 (15), G3 (17) |
| sul2 | 3 (6) | G3 (3) | ||
| sul3 | 2 (4) | G2 (2) | ||
| Trimethoprim | 6 (11) | dfrA1-like | 4 (4/6)g | G3 (4) |
| dfrA7 | 0 | |||
| dfrA12 | 0 | |||
| dfrA14 | 1 (1/6)g | G3 (1) | ||
| dfrA17 | 0 | |||
| Othersf | 1 (1/6)g | G2 (1) | ||
| Tetracyclines | ||||
| Tetracycline | 17 (31) | tet(A) | 5 (29) | G1 (1), G3 (4) |
| tet(B) | 10 (59) | G2 (3), G3 (7) | ||
| tet(G) | 0 | |||
| Othersf | 3 (18) | G1 (2), G3 (1) | ||
| Quinolones and fluoroquinolones | ||||
| Nalidixic acid and ciprofloxacin | 45 (82), 16 (29)h | qnrA | 0 | |
| qnrB | 0 | |||
| qnrC | 0 | |||
| qnrD | 0 | |||
| qnrS | 0 | |||
Five of the 55 isolates selected were susceptible to all of the antimicrobials tested.
The breakpoints used are shown in Table 1. Seven other antimicrobials were also tested: no resistance to florfenicol, ceftiofur, or colistin was detected; 46 (84%) of the isolates were resistant to spectinomycin; 6 (11%) of the isolates were resistant to trimethoprim-sulfamethoxazole; 13 (24%) of the isolates were resistant to amoxicillin-clavulanic acid; and 2 (4%) of the isolates were resistant to neomycin.
G1, turkey baseline study (feces) performed in 2006 and 2007; G2, turkey diagnostic isolates (feces) collected in 2002 and 2003 and in 2005 and 2006; G3, turkey-derived food diagnostic isolates collected in 2000 to 2007.
Intermediate or full resistance.
The aadB gene also confers a low resistance to kanamycin according to Zhao et al. (45).
The resistance mechanisms were not identified in this study.
Because of the low number of resistant isolates (<10), only the absolute number is indicated.
For ciprofloxacin, only isolates with intermediate resistance (MIC, 2 μg/ml) are included. An additional 29 isolates (53%) showed reduced susceptibility (MIC, 1 to 0.25 μg/ml).