Table 5 Detection of Salmonella enterica in inoculated portions of powdered infant formula (100 g).

From: Accurate and sensitive detection of Salmonella in foods by engineered bacteriophages

Serovar

Inoculum

RLU

PhageDx

Culture

Heidelberg

None

339

Negative

Negative

None

354

Negative

Negative

None

376

Negative

Negative

Low

285

Negative

Negative

Low

288

Negative

Negative

Low

333

Negative

Negative

Low

343

Negative

Negative

Low

395

Negative

Negative

Low

432

Negative

Negative

Low

461

Negative

Negative

Low

259,893,152

Positive

Positive

Low

461,765,216

Positive

Positive

Low

501,775,552

Positive

Positive

High

498,655,520

Positive

Positive

High

1,031,197,312

Positive

Positive

Reading

None

271

Negative

Negative

None

305

Negative

Negative

Low

302

Negative

Negative

Low

334

Negative

Negative

Low

2820

Positive

Positive

Low

10,667

Positive

Positive

Low

16,944

Positive

Positive

Low

43,975

Positive

Positive

Low

162,731

Positive

Positive

Low

167,912

Positive

Positive

Low

458,206

Positive

Positive

Low

481,718

Positive

Positive

High

170,377

Positive

Positive

High

340,074

Positive

Positive

High

365,167

Positive

Positive

  1. Salmonella enterica subsp. enterica serovars were diluted from stationary phase cultures, dried down, and inoculated into pre-screened portions of PIF. Strain SL476 (FDA) and 52317.1 (USDA) were used as serovar Heidelberg and Reading, respectively. Equilibrated samples were enriched for 16 h, diluted ten-fold, and infected with a cocktail of SEA1.NL and TSP1.NL for 2 h before being assessed for luciferase production. Inoculum consisted of either no CFU “None”, 1 CFU per 100 g “Low”, or 5 CFU per 100 g “High”. A detection threshold of 750 RLU was used to determine positive samples. Samples were confirmed by a culture-based method involving plating on CHROMagar Salmonella.