Improved culture methods for isolation of Salmonella organisms from swine feces

Objective-To compare 3 alternative culture techniques for the detection of Salmonella organisms in swine feces with a modification of the internationa l Standard Organization (ISO) 6579 standard protocol. Sample Population-Fecal samples from swine herds suspected of having Salmon ella infections. Procedure-4 experiments were performed to evaluate the following: 1) diagno stic sensitivity of the selective preenrichment and rapid isolation novel t echnology (SPRINT) protocol, compared with that of the modified ISO protoco l; 2) detection limit of the SPRINT protocol for Salmonella organisms; 3) u se of tetrathionate-novobiocin (TTN) broth, compared with selenite cysteine (SC) broth for selective enrichment; and 4) use of universal preenrichment (UPE) broth, compared with buffered peptone water (BPW) for preenrichment of samples prior to the use of modified semisolid Rappaport-Vassiliadis (MS RV) plates. Results-Comparing the Salmonella culture results of 183 swine fecal samples , the diagnostic sensitivity of the SPRINT protocol (0.86) was not signific antly different than the diagnostic sensitivity of the modified ISO protoco l (0.80), although it was 24 hours faster. The SPRINT protocol could detect 5 of the 6 investigated Salmonella serotypes at inoculation concentrations of < 10 colony-forming units (CFU)/25 g of uncontaminated feces. The TTN b roth performed significantly better than the SC broth for selective enrichm ent of Salmonella organisms. There was no significant difference in results of preenrichment of samples between the use of UPE broth or BPW. Conclusions and Clinical Relevance-The SPRINT protocol may provide a faster alternative for isolation of Salmonella organisms from swine fecal samples . Furthermore, the use of TTN broth instead of SC broth may increase the se nsitivity of the modified ISO 6579 protocol.