TABLE 1.
Method considerations and parameters for the isolation and identification of S. Typhi using the Moore swab technique
| Step | Options | Details or examples (references) |
|---|---|---|
| Site/source selection | Untreated effluent | Public sewer network (10, 18, 40, 56, 60, 61, 63); sewage leaving a building, residence, or hospital (55, 62, 64, 92); repurposed wastewater, e.g., for irrigation (69, 76) |
| Treatment plant influent/effluent | Wastewater entering/exiting a treatment plant (134, 135) | |
| Environmental | Surface water, e.g., canals, rivers, streams, and storm drains (55, 57, 58, 76) | |
| Flush toilets | Toilet prior to sewer (45) or septic tank (126) | |
| Parameters | Swab construction | Gauze type (fiber composition, mesh size, absorbency), gauze measurements (by size or by mass), string or wire attachment |
| Sampling schedule | Frequency, duration, replicates | |
| Sample handling and processing | Transport conditions and time | |
| Dilution schema | Direct inoculation, 5- or 10-fold dilution schema | |
| Enrichment | Preenrichment | Universal preenrichment broth, nutrient broth, sterile saline |
| Selective enrichment | Varies by species, e.g., selenite-F broth for Salmonella | |
| Differentiation/selection | Differential solid media | For enteric bacteria, e.g., Salmonella-Shigella agar, deoxycholate-citrate agar, xylose-lysine-deoxycholate agar |
| Highly selective solid media | Varies by species, e.g., Wilson and Blair (bismuth sulfite) agar for S. Typhi | |
| Identification (classical) | Biochemical reactions | Triple sugar iron agar, lysine iron agar, enzyme activity, urea broth, fermentation, commercial kits/panels |
| Serotyping | For Salmonella, agglutination with anti-O, anti-H, and anti-Vi antisera | |
| Identification (modern) | Pulse-field gel electrophoresis | |
| PCR | PCR or quantitative real-time PCR | |
| Genomics | Whole-genome, 16S ribosomal, or shotgun sequencing |