Fate of non O157 Shiga toxigenic Escherichia coli in composted cattle manure

V.P Gonçalves,J.M Marin

doi:10.1590/s0102-09352007000400001

Abstract

To determine the fate of Shiga toxigenic Escherichia coli (STEC) non-O 157 in composted manure from naturally colonized cattle, fresh manure was obtained from three cows carrying non-O157 STEC strains possessing the stx2 gene. Two composting systems were used: a 0.6m deep cave opened in the soil and an one meter high solid manure heap in a pyramidal architecture. Every day, for the 10 first days, and every five days for a month, one manure sample from three different points in both systems was collected and cultured to determine the presence of E. coli and the presence of the stx 2 gene in the cells. The temperature was verified at each sampling. STEC non-O157 E. coli cells survived for 8, 25 and 30 days at 42, 40 and 38ºC, respectively, in the deep cave and 4, 4 and 7 days at 65, 58 and 52ºC, respectively, in the heap, during the composting manure. Temperature and indigenous microorganisms appear to contribute to pathogen disappearance in the composting system. It is concluded that both composting systems were efficient to eliminate STEC cells. Land application of composted manure should minimize environmental risk associated with the dissemination of the pathogen.

Highlights

Spreading of bovine manure is a common soil fertilization procedure, often used in vegetable production in Brazil (Pereira Neto, 1996)
Bacteria showing the stx 2 gene could be detected in the top layer of the composting heap until the fourth day and in the cave until the thirstiest day; in the middle layer, until the fourth day and twenty-fifth days in heap and cave, respectively; and in the bottom layer, until the seventh and eighth days in the heap and cave, respectively
In the pile the temperature was smaller and reached only a maximum of 33oC during the experimental period (Fig. 2c) and the bacteria carrying the stx 2 gene could be detected for 60 days

Summary

Introduction

Spreading of bovine manure is a common soil fertilization procedure, often used in vegetable production in Brazil (Pereira Neto, 1996). A potential risk arising from the disposal of animal waste of fecal origin is the spreading of enteric pathogens (Peel, 1997). Shiga toxin-producing E. coli (STEC) organisms of different serotypes have been increasingly isolated from diseased humans and from domestic animals (Karmali, 1989; Beutin et al, 1993). Many of these isolates were typical STEC, belonging to serotypes O26, O111 and O157, but most belonged to serotype O157:H7, which can cause severe diseases including hemorrhagic colitis and hemolityc-uremic syndrome in humans (Paton and Paton, 1998). Manure is a potential biohazard capable of transmitting infective agents to both humans and animals (Jones, 1980; Tauxe, 1997)

Methods

Results

Conclusion