Rapid Detection of Salmonellosis Due to Salmonella enterica Serovar Typhimurium in Peruvian Commercially Bred Cavies, Using Indigenous Wild Bacteriophages

Introduction: The salmonelloses are among the commonest, most widespread human zoonotic infections. They have generated international networks to attempt their control, since they cause a spectrum of ailments, ranging from inapparent carrier states to full-blown, severe, sometimes deadly diarrheal and systemic disease. Rapid diagnosis is needed for a number of reasons. The aim of this study was to standardize and validate a phage amplification test for the identification of salmonellosis to be applied to infections of Cavia porcellus. Methods: Native bacteriophages were isolated from infected cavies and environmental residues from commercial cavy-breeding facilities. Salmonella enterica serovar Typhimurium ATCC 14028 was used to detect, isolate and propagate the bacteriophages, and to standardize a phage amplification assay to detect S. Typhimurium from rectal swabs of cavies. The phage amplification assay was tested using 2 antiviral agents, MgSO₄·7H₂O (MAS) and pomegranate rind extract (PRE) plus ferrous sulfate (PRE–FeSO₄). Results: The final assay format chosen used PRE–FeSO₄ and allowed detection of S. Typhimurium in 90 min from culture, 5 h from clinical samples, with a limit of detection at 10³ pfu; sensitivity was 98.2%, specificity 98%, negative predictive value (NPV) 96.1%, and positive predictive value (PPV) 99.1%. Conclusion: Bacteriophage amplification is therefore an appropriate, fast procedure for detection of this pathogen in clinical samples.