TABLE 1.
Frequency of resistance per variable (specimen, year of isolation, and whether the isolates were chosen for whole-genome sequence typing of Salmonella serovar Typhi in Zambian patients)
| Variable | Total no. of isolates | No. (%) of isolates resistant to various antimicrobial agents and CLSI clinical breakpoint values (mg/liter) |
|||||||
|---|---|---|---|---|---|---|---|---|---|
| AMC (≥32) | AMP (≥32) | CHL (≥32) | CIP (>0,064) | NAL (≥32) | STR (>16) | SMX (≥512) | TMP (≥16) | ||
| Isolate type | |||||||||
| Blood | 86 (91.5) | 1 (1.2) | 85 (98.8) | 73 (84.9) | 4 (4.7) | 3 (3.5) | 85 (98.8) | 85 (98.8) | 85 (98.8) |
| Stool | 8 (8.5) | 0 | 8 (100.0) | 5 (62.5) | 0 | 0 | 8 (100.0) | 8 (100.0) | 8 (100.0) |
| Yr of isolation | |||||||||
| 2010 | 35 (37.2) | 0 | 35 (100.0) | 29 (82.9) | 2 (5.7) | 2 (5.7) | 35 (100.0) | 35 (100.0) | 35 (100.0) |
| 2011 | 33 (35.1) | 1 (3.0) | 33 (100.0) | 28 (84.8) | 2 (6.1) | 1 (3.0) | 33 (100.0) | 33 (100.0) | 33 (100.0) |
| 2012 | 26 (27.7) | 0 | 25 (96.2) | 21 (80.8) | 0 | 0 | 25 (96.2) | 25 (96.2) | 25 (96.2) |
| WGST performed | 33 (35.1) | 0 | 32 (97.0) | 27 (81.8) | 2 (6.1) | 2 (6.1) | 32 (97.0) | 32 (97.0) | 32 (97.0) |
| WGST not performed | 61 (64.9) | 1 (1.6) | 61 (100.0) | 51 (83.6) | 2 (3.3) | 1 (1.6) | 61 (100.0) | 61 (100.0) | 61 (100.0) |
| Total | 94 (100.0) | 1 (1.1) | 93 (99.0) | 78 (83.0) | 4 (4.3) | 3 (3.2) | 93 (99.0) | 93 (99.0) | 93 (99.0) |
Abbreviations: AMC, amoxicillin plus clavulanic acid; AMP, ampicillin; CHL, chloramphenicol; CIP, ciprofloxacin; NAL, nalidixic acid; SPT, spectinomycin; STR, streptomycin; SMX, sulfamethoxazole; TMP, trimethoprim; WGST, whole-genome sequence typing. STR, azithromycin, ceftiofur, colistin, florfenicol, neomycin, and spectinomycin results were interpreted according to EUCAST guidelines on the basis of epidemiological cutoff values. Apramycin results were interpreted according to research results from DTU-Food. Ciprofloxacin results were also interpreted according to EUCAST guidelines on the basis of epidemiological cutoff values to detect decreased susceptibility. No resistance was observed for apramycin (MIC = >32 mg/liter), azithromycin (>32 mg/liter), cefotaxime (≥4 mg/liter), ceftiofur (>2 mg/liter), ciprofloxacin (high-level resistance [≥1 mg/liter]), colistin (>2 mg/liter), florfenicol (>16 mg/liter), gentamicin (≥16 mg/liter), neomycin (>4 mg/liter), spectinomycin (>64 mg/liter), and tetracycline (≥16 mg/liter).