Survival ofEscherichia coliO157:H7 andSalmonella entericaserovar Typhimurium in manure and manure-amended soil under tropical climatic conditions in Sub-Saharan Africa

Abstract

Aims: To establish the fate of Escherichia coli O157:H7 and Salmonella Typhimurium in manure and manure‐amended agricultural soils under tropical conditions in Sub‐Saharan Africa. Methods and Results: Survival of nonvirulent E. coli O157:H7 and Salm. Typhimurium at 4 and 7 log CFU g−1 in manure and manure‐amended soil maintained at ≥80% r.h. or exposed to exclusive field or screen house conditions was determined in the Central Agro‐Ecological Zone of Uganda. Maintaining the matrices at high moisture level promoted the persistence of high‐density inocula and enhanced the decline of low‐density inocula in the screen house, but moisture condition did not affect survival in the field. The large majority of the survival kinetics displayed complex patterns corresponding to the Double Weibull model. The two enteric bacteria survived longer in manure‐amended soil than in manure. The 7 log CFU g−1E. coli O157:H7 and Salm. Typhimurium survived for 49–84 and 63–98 days, while at 4 log CFU g−1, persistence was 21–28 and 35–42 days, respectively. Conclusions: Under tropical conditions, E. coli O157:H7 and Salm. Typhimurium persisted for 4 and 6 weeks at low inoculum density and for 12 and 14 weeks at high inoculum density, respectively. Significance and Impact of the Study: Persistence in the tropics was (i) mostly shorter than previously observed in temperate regions thus suggesting that biophysical conditions in the tropics might be more detrimental to enteric bacteria than in temperate environments; (ii) inconsistent with published data isothermally determined previously hence indicating the irrelevance of single point isothermal data to estimate survival under dynamic temperature conditions.

Survival of Escherichia coli O157:H7 in Soils from Jiangsu Province, China

“…However, in the neutral soils, E. coli O157:H7 declined much slowly than in the acidic soils and survived for up to 38 days. There have been previous reports which linked E. coli O157:H7 survival times ( t d ) with soil pH [9], [12], [32], [35], However, our data showed an exceptionally highly statistically significant correlation between these two parameters. It therefore appears that the different physical, chemical and biological properties of acidic and neutral soils resulted in the remarkable differences in E. coli O157:H7 survival.…”

Persistence of Pathogenic and Non-Pathogenic Escherichia coli Strains in Various Tropical Agricultural Soils of India

“…We followed the survival of E . coli strains in the soil in a similar way as performed in previous studies [ 18 , 50 , 51 ].…”

“…The survival of O157:H7 in soil and manure was assessed using marker strains of O157:H7 in past. Some authors used spontaneous mutants of O157:H7, devoid of stx genes showing rifampicin or nalidixic acid resistance for assessing the survival in soil [ 18 , 52 – 54 ]. Oliveira et al [ 19 ] used non-pathogenic strain of O157:H7 unable to produce virotoxins (Stx1 and Stx2), used for soil incubation studies and counted using O157 specific medium (Sorbitol MacConkey agar supplemented with cefixime and tellurite).…”

“…It was expected that the soils from temperate climatic condition would be different from tropical climate because of unique differences in soil properties, moisture condition, temperature regime and cropping pattern. The tropical soils had much shorter survival times (35–75 days: [ 18 ]; 21–28 days: [ 24 , 60 ]; 103 days: [ 50 ]) than those from temperate climate (21 months: [ 61 ]; 120 days: [ 62 ]; 154–231 days: [ 63 ]; 300 days: [ 64 ]). In the present study, the survival time reported (40–60 days in all soil types) is well-fitted to the tropical soils.…”

Effect of Organic and Inorganic Fertilizers on the Yield and Quality of Jalapeño Pepper Fruit (Capsicum annuum L.)

“…The gained benefits after the incorporation of organic fertilizers are numerous; nevertheless, the microbiological safety of fresh products could imply a food quality risk due to the incorporation of non-composted animal manure. This is because in agricultural soils, animal manure is a known source of enteric pathogens such as Salmonella enterica serotype typhimurium [13]. In facing these concerns, alternatives to reduce the risk of contamination of crops by pathogens are being analyzed, such as by proposing the solarization of manure [14].…”