Table 7.
MGIT-DST of PZA R-Mtb with Exo-MS alone and in combination with PZA
| Mtb Isolate | Exo-MS (mg/mL) | Exo-MS (mg/mL) + PZA 100 μg/mL | Ferric citrate + Exo-MS (mg/mL) | ||||
|---|---|---|---|---|---|---|---|
| 0.125 | 0.25 | 0.5 | 0.125 | 0.25 | 0.5 | 0.5 | |
| PZA R isolate 1 | 0 | 0 | 0 | 0 | 0 | 0 | 400 |
| PZA R isolate 2 | 0 | 0 | 0 | 0 | 0 | 0 | 400 |
| MDR + PZA R isolate 3 | 400 | 0 | 0 | 400 | 0 | 0 | 400 |
| MDR + PZA R isolate 4 | 400 | 400 | 400 | 400 | 400 | 400 | 400 |
| MDR + PZA R isolate 5 | 400 | 25 | 0 | 400 | 0 | 0 | 400 |
| MDR + PZA R isolate 6 | 400 | 317 | 0 | 400 | 237 | 0 | 400 |
| MDR + PZA R isolate 7 | 400 | 400 | 400 | 400 | 386 | 253 | 400 |
| INFERENCE | S n = 2 | S n = 4 | S n = 5 | S n = 2 | S n = 4 | S n = 5 | R |
GU value of GC for all seven isolates was 400. GU value in PZA-containing medium for all isolates was also 400. R resistant, S susceptible. If the GU value of the drug-containing tube is ≥100, the interpretation is Resistant by the MGIT instrument. If the GU value of the drug tube is <100, the interpretation is Susceptible (n = no. of isolates susceptible)
Inhibitory effect of Exo-MS and Exo-MS + PZA on seven PZA R isolates: The medium used was Middlebrook 7H9 broth, pH = 5.9 incubated at 37 °C for14 days in the MGIT instrument