Survival of Enterohemorrhagic Escherichia coli O157:H7 in Water

Abstract

Several recent Escherichia coli O157:H7 outbreaks associated with both drinking and recreational water raise concerns about waterborne illness caused by this pathogen. The survival characteristics of a mixture of five nalidixic acid-resistant E. coli O157:H7 strains (10(3) CFU/ml) in filtered and autoclaved municipal water, in reservoir water, and in water from two recreational lakes were determined for a period of 91 days at 8, 15 or 25 degrees C. Greatest survival was in filtered autoclaved municipal water and least in lake water. Regardless of the water source, survival was greatest at 8 degrees C and least at 25 degrees C. E. coli O157:H7 populations decreased by 1 to 2 log10 by 91 days at 8 degrees C, whereas the pathogen was not detectable (> or 3 = log10 decrease) within 49 to 84 days at 25 degrees C in three of the four water sources. SDS-PAGE of surface antigens of surviving cells revealed that there was no major alteration in lipopolysaccharide pattern, but outer membrane protein composition did change. These studies indicate that E. coli O157:H7 is a hardy pathogen that can survive for long periods of time in water, especially at cold temperatures. However, direct viable counts of E. coli O157:H7 determined by acridine orange staining remained essentially the same for 12 weeks at 25 degrees C, whereas viable counts on tryptic soy agar plates decreased to undetectable levels within 12 weeks. Results suggest that E. coli O157:H7 can enter a viable but nonculturable (VBNC) state in water.

State transitions of Vibrio parahaemolyticus VBNC cells evaluated by flow cytometry

“…Some authors (12) report that the SDS-page of surface antigens of surviving E. coli cells revealed that there was no major alteration in the LPS pattern, however OMPs composition did change. The expression of surface antigenic determinants may be considered an adaptive phenomenon related to host or environmental conditions.…”

“…Changes in surface components, such as outer membrane protein (OMP) and lipopolysaccharide (LPS), representing surface antigens or structures involved in the adherence to host cells, have been reported by some authors (12) in Gram-negative bacteria during the phases of a survival strategy. FCM in combination with specific antibodies has previously been used to investigate the variation in antigenic components of microbial cells (25,26) and to study the distribution of antigens on the cell surface (27,28).…”

“…In this state, although still expressing various degrees of metabolic activity and possibly being able to cause infection (6,8,9), the bacterial cells cannot be cultured on conventional laboratory media that normally support their growth. During entry into the VBNC state, bacteria acquire a coccal morphology, become smaller in size (10,11), and show changes in their protein (12,13) and fatty acid profiles (14). The nucleic acid content, in particular RNA, can vary when bacteria enter the VBNC state, justifying the reduced RNA levels which result from nutritional downshifts in bacteria (15).…”

A Cluster of Escherichia coli O157: Nonmotile Infections Associated with Recreational Exposure to Lake Water

“…Wang and Doyle found that E. coli O157:H7 can enter a viable, but nonculturable state in water, and demonstrated that the organism can survive in lake water for at least seven weeks at 25°C, and longer at cooler temperatures. 12 The elevated lake coliform counts two weeks before the outbreak exceeded recommended levels for recre- Figure 1. Schematic of the lake and river, and approximate location of the cattle seen upstream of the lake ational use.…”

Antimicrobial Resistance Arising from Food-Animal Productions and Its Mitigation

“…Some studies have been carried out to determine the survival of manure bacteria after land application. Data from human pathogens, such as Salmonella and Campylobacter, Yersinia enterocolitica and Escherichia coli O157:H7, showed that their survival in water, soil and manure slurry varies dramatically, ranging from one day to longer than one year (Buswell et al, 1998;Guo et al, 2002;Santo Domingo et al, 2000;Tauxe, 1997;Wang & Doyle, 1998). Although the survival of these manure bacteria remains to be determined, likely depending on the physiological and ecological features of the resistant bacteria, the resistance genes can be transferred to indigenous soil bacteria.…”