Comparison of heterophil phagocytosis for heterophil-adapted Salmonella enteritidis (HASE) and wild-type Salmonella enteritidis (SE)

Serial passage of Salmonella enteritidis (SE) yields heterophil-adapted SE (HASE) strains that have resulted in decreased shedding of SE in feces and reduced egg contamination. Additionally, increasing the number of heterophi l passages further reduced the number and frequency of fecal shedding. To e valuate SE and heterophil interaction, nine SE strains were fluorescein iso thiocyanate-labeled when viable. There were six wild-types: SE TK 474, SE T K 584, SE TK 599, SE TK 600, SE TK 655, and SE TK 657; and three HASE strai ns: TK 499 heterophil adapted five times, TK 598 heterophil adapted six tim es, and TK 605 heterophil adapted 11 times. Trials were repeated seven time s in duplicate with heterophils isolated from seven healthy chickens. Heter ophils were incubated with the bacterial strains at 41 C for 15 min, and 10 ,000 heterophils were analyzed by flow cytometry. Percentage of phagocytosi s and mean channel number of fluorescence were compared. Both parameters we re significantly increased for all HASE-type strains compared with wild-typ e, nonadapted SE strains. Increased phagocytosis of HASE bacterial strains may be significant in processing and elimination of the HASE strains and ma y be related to the protective effect of HASE by decreased shedding of wild -type SE challenge strains.