TABLE 2.
NUMBER AND PERCENTAGEa OF NONTYPHOIDAL SALMONELLA ISOLATES WITH SELECTED RESISTANCE PATTERNS, BY SEROTYPE,b 1996–2009
| Resistance to ceftriaxonec (MIC ≥4μg/mL) (N = 730) | Nonsusceptibility to ciprofloxacind (MIC ≥0.12μg/mL) (N = 482) | Resistance to ≥ 3 antimicrobial classes (N=3247) | |||||||||
|---|---|---|---|---|---|---|---|---|---|---|---|
| Serotype | No. | % R | % Serotype | Serotype | No. | % R or % I | % Serotype | Serotype | No. | % R | % Serotype |
| Newport | 331 | 45 | 14 | Resistant (R): | Typhimurium | 1935 | 60 | 37 | |||
| Typhimurium | 184 | 25 | 3.5 | Senftenberg | 15 | 38 | 13 | Newport | 379 | 12 | 16 |
| Heidelberg | 81 | 11 | 6.2 | Typhimurium | 6 | 15 | 0.1 | Heidelberg | 182 | 5.6 | 14 |
| Agona | 28 | 3.8 | 7.5 | Litchfield | 4 | 10 | 2.9 | Enteritidis | 78 | 2.4 | 1.7 |
| I 4,[5],12:i:- | 16 | 2.2 | 3.1 | Schwarzengrund | 3 | 7.5 | 2.2 | Hadar | 64 | 2.0 | 22 |
| Enteritidis | 10 | 1.4 | 0.2 | Stanley | 52 | 1.6 | 29 | ||||
| Dublin | 8 | 1.1 | 12 | Intermediate (I): | Paratyphi B var. L( + ) tartrate + | 48 | 1.5 | 13 | |||
| Infantis | 8 | 1.1 | 2.0 | Enteritidis | 186 | 42 | 4.0 | Agona | 46 | 1.4 | 12 |
| Saintpaul | 6 | 0.8 | 1.1 | Typhimurium | 57 | 13 | 1.1 | I 4,[5],12:i:- | 41 | 1.3 | 8.0 |
| Concord | 5 | 0.7 | 71 | Virchow | 36 | 8.1 | 43 | Montevideo | 35 | 1.1 | 5.4 |
| Reading | 4 | 0.5 | 9.5 | Hadar | 10 | 2.3 | 3.4 | Derby | 34 | 1.0 | 34 |
| Mbandaka | 3 | 0.4 | 2.0 | Agona | 8 | 1.8 | 2.2 | Saintpaul | 32 | 1.0 | 5.7 |
| Senftenberg | 3 | 0.4 | 2.6 | Blockley | 8 | 1.8 | 20 | Dublin | 28 | 0.9 | 42 |
| Uganda | 3 | 0.4 | 5.9 | Infantis | 8 | 1.8 | 2.0 | Infantis | 19 | 0.6 | 4.8 |
| Newport | 8 | 1.8 | 0.3 | Senftenberg | 17 | 0.5 | 15 | ||||
| Berta | 7 | 1.6 | 4.4 | Berta | 14 | 0.4 | 8.8 | ||||
| Corvallis | 7 | 1.6 | 88 | Virchow | 14 | 0.4 | 17 | ||||
| Heidelberg | 6 | 1.4 | 0.5 | Muenchen | 12 | 0.4 | 2.2 | ||||
| Saintpaul | 6 | 1.4 | 1.1 | Blockley | 10 | 0.3 | 25 | ||||
| laviana | 5 | 1.1 | 0.5 | Choleraesuis | 7 | 0.2 | 58 | ||||
| Stanley | 5 | 1.1 | 2.8 | laviana | 7 | 0.2 | 0.7 | ||||
| I 4,[5],12:i:- | 4 | 0.9 | 0.8 | Schwarzengrund | 7 | 0.2 | 5.0 | ||||
| Montevideo | 4 | 0.9 | 0.6 | Bovismorbificans | 6 | 0.2 | 11 | ||||
| Uganda | 4 | 0.9 | 7.8 | Reading | 6 | 0.2 | 14 | ||||
| Bareilly | 3 | 0.7 | 2.3 | Bredeney | 5 | 0.2 | 14 | ||||
| Choleraesuis | 3 | 0.7 | 25 | Concord | 5 | 0.2 | 71 | ||||
| Concord | 3 | 0.7 | 43 | Kentucky | 5 | 0.2 | 11 | ||||
| Dublin | 3 | 0.7 | 4.5 | Thompson | 5 | 0.2 | 1.3 | ||||
| Mbandaka | 3 | 0.7 | 2.0 | Brandenburg | 4 | 0.1 | 5.0 | ||||
| Schwarzengrund | 3 | 0.7 | 2.2 | Chester | 4 | 0.1 | 17 | ||||
| Thompson | 3 | 0.7 | 0.8 | Litchfield | 4 | 0.1 | 2.9 | ||||
| Mbandaka | 4 | 0.1 | 2.7 | ||||||||
| Muenster | 4 | 0.1 | 6.8 | ||||||||
| Uganda | 4 | 0.1 | 7.8 | ||||||||
| Anatum | 3 | 0.1 | 1.8 | ||||||||
| Corvallis | 3 | 0.1 | 38 | ||||||||
| Mississippi | 3 | 0.1 | 1.0 | ||||||||
| Ohio | 3 | 0.1 | 5.7 | ||||||||
Percentage of total isolates with resistance pattern (% R or % I) and percentage of the serotype with resistance pattern (% serotype).
Data are not shown for additional serotypes with < 3 resistant isolates: 26 serotypes (34 isolates) plus 6 isolates of unknown serotypes were resistant to ceftriaxone, 9 serotypes (11 isolates) plus 1 isolate of unknown serotype were resistant to ciprofloxacin; 33 serotypes (42 isolates) plus 10 isolates of unknown serotypes had intermediate susceptibility to ciprofloxacin, and 47 serotypes (60 isolates) plus 58 isolates of unknown serotypes were resistant to ≥ 3 classes.
The same 14 serotypes with ≥ 3 ceftriaxone-resistant isolates also had ≥ 3 ceftiofur-resistant isolates. Of 741 isolates resistant to ceftriaxone or ceftiofur, 15 were resistant to only 1 of the 2 agents; 11 were resistant to only ceftiofur and 4 to only ceftriaxone. Except for Enteritidis and Senftenberg, > 98% of isolates resistant to 1 agent among these serotypes were resistant to the other agent. Among Enteritidis and Senftenberg, although all ceftriaxone-resistant isolates were resistant to ceftiofur, only 77% (10/13) of ceftiofur-resistant isolates among Enteritidis and 75% (3/4) among Senftenberg were resistant to ceftriaxone.
The 482 isolates include 40 that were resistant (minimum inhibitory concentration [MIC] ≥ 1 μg/mL) and 442 with intermediate susceptibility to ciprofloxacin (MIC= 0.12–0.5 μg/mL). Of the 40 ciprofloxacin-resistant isolates, 33 (83%) were resistant and 7 (17%) were susceptible to nalidixic acid. Of the 442 ciprofloxacin-intermediate isolates, 382 (86%) were resistant and 60 (14%) were susceptible to nalidixic acid. The 67 isolates that were nonsusceptible to ciprofloxacin and susceptible to nalidixic acid were of 25 serotypes; most were Typhimurium (25%), Enteritidis (12%), Corvallis (10%), or Litchfield (7%).