Influence of Acid Adaptation on the Tolerance of Escherichia coli O157:H7 to Some Subsequent Stresses

Abstract

Three stains of Escherichia coli O157:H7, including ATCC 43889, ATCC 43895, and 933, were first subjected to acid adaptation at a pH of 5.0 for 4 h. Thermal tolerance at 52 degrees C and survival of the acid-adapted as well as the nonadapted cells of E. coli O157:H7 in the presence of 10% sodium chloride, 0.85% bile salt, or 15.0% ethanol were investigated. Results showed that the effect of acid adaptation on the survival of E. coli O157:H7 varied with the strains and types of subsequent stress. Acid adaptation caused an increase in the thermal tolerance of E. coli O157:H7 ATCC 43889 and ATCC 43895, but no significant difference in the thermal tolerance was noted between acid-adapted and nonadapted cells of E. coli O157:H7 933. Although the magnitude of increase varied with strains of test organisms, acid adaptation generally led to an increase in the tolerance of E. coli O157:H7 to sodium chloride. On the other hand, the susceptibility of acid-adapted cells of the three strains of E. coli O157:H7 tested did not show a significant difference from that of their nonadapted counterparts when stressed with bile salt. The acid-adapted cells of E. coli O157:H7 ATCC 43889 and ATCC 43895 were less tolerant than the nonadapted cells to ethanol, whereas the tolerance of adapted and nonadapted cells of E. coli O157:H7 933 showed no significant differences.

Pulsed electric field inactivation of E. coli O157:H7 and non-pathogenic surrogate E. coli in strawberry juice as influenced by sodium benzoate, potassium sorbate, and citric acid

“…This difference may, again, be attributed to the protective effects of the increasing electrical conductivity induced by the addition of the sodium and potassium salts. The addition of preservatives þ 2.7% citric acid effected greater injury (100%) in E. coli 35218 than occurred in the acid-resistant enterohemorrhagic E. coli (96%), which may be attributed to the acid-resistant nature of E. coli O157:H7 (Cheng et al, 2002;Duffy et al, 1999;Marshall et al, 2005Yu et al, 2001. …”

“…E. coli O157:H7 in juice with antimicrobials and 2.7% citric acid (pH 2.7) treated with PEF was reduced by 2.60, 4.32 and 6.95 log CFU/ml at 45, 50 and 55 C while the surrogate E. coli decreased by 3.54, 5.69, and 7.13 log, under the same conditions. The acid-resistant nature inherent to many strains of E. coli O157:H7, including our strain, ATCC 34895 may have contributed to its greater survivability in strawberry juice þ 2.7% citric acid (pH 2.71, Table 1) when treated by PEF at 45 and 50 C (Cheng et al, 2002;Yu et al, 2001).…”

Phytic Acid and Sodium Chloride Show Marked Synergistic Bactericidal Effects against Nonadapted and Acid-Adapted Escherichia coli O157:H7 Strains

“…In the United States, the bacterium causes an estimated 73,000 cases of infection per year, with up to 61 deaths (32), and several large outbreaks have occurred worldwide (33,34). E. coli O157:H7 is a highly virulent pathogen because it carries genes for Shiga toxin production and has an adaptive acid tolerance response system that results in strong acid resistance (35)(36)(37). Therefore, we selected E. coli O157:H7 as the target pathogen for study of the bactericidal effects of natural acidic compounds.…”

Correlation between biliary bacteriology and types of gallstones in uncomplicated symptomatic cholelithiasis

“…Moreover, it is suggested that the recovery of bacteria in bile cultures is affected by toxicity of bile salts. Thus, traditional culturing methods of bile might miss a large number of underlying bacterial infections that could lead to acute or chronic cholecystitis (Grill et al, 2000;Cheng et al, 2002;De Boever and Verstraete, 1999;Kurtin et al, 2000;Manolis et al, 2008). Culture of bile from the gallbladder of patients with uncomplicated cholelithiasis during cholecystectomy has shown principally E. coli.…”