Purpose: The purpose of this study is to determine Salmonella Newport persistence and resuscitation in soils containing poultry litter (PL)-based or chemical fertilizer amendments.
Methods: Salmonella Newport (rifampicin-resistant) at 4.4 log CFU/pot was inoculated into pots (7.5cm by 5.5cm) containing soil amended with either: i) PL (raw); ii) heat-treated poultry litter pellets (HTPP) or iii) urea (U) (chemical fertilizer) to provide equivalent levels of nitrogen to soil. Inoculated pots were stored in a growth chamber (20°C, 10 h day length). Pots were irrigated weekly (day 0, 7, 13), and three samples of each treatment were taken immediately before and 24 h after irrigation. Bacterial populations were examined over two weeks and enumerated on xylose lysine deoxycholate agar with rifampicin (XLDR). Soil samples were dried to determine moisture content. Recovered populations of Salmonella Newport (log CFU/gdw (gram dry weight)) were analyzed using a one-way ANOVA and student’s T-test in JMP.
Results: Mean Salmonella Newport populations in PL-amended soils were significantly (P<0.05) higher (3.8±0.58 log CFU/gdw) compared to populations in HTPP-amended (1.9±1.8 log CFU/gdw) or U-amended (1.4±1.8 log CFU/gdw) soils. Salmonella Newport populations were present but fell below the limit of detection (<0.62 log CFU/g) in HTPP- and U-amended soils on days 6, 7, and 8. However, populations of Salmonella Newport resuscitated to 3.74 log CFU/gdw in HTPP-amended soils on day 13, and to 2.99 log CFU/gdw in U-amended soils on day 14.
Significance: These data suggest that soils containing PL may support higher populations of Salmonella Newport than HTPP and U-amended soils, but that Salmonella Newport populations are dynamic in both U- and HTPP-amended soils under specific conditions.