Effect of Hydrogen Peroxide and Sodium Chloride on Enumeration of Thermally Stressed Cells of Staphylococcus aureus

Abstract

Evidence is presented suggesting that the decreased enumeration of heat-stressed Staphylococcus aureus cells on selective media is the result of accumulation of metabolic H2O2. It accumulates due to the decreased activity of catalase caused by the synergistic effects of heat and NaCl. Heated cells enumerated anaerobically on tryptic soy agar (TSA) containing 6.5% NaCl (TSAS 6.5) exhibited a 200-fold increase compared to cells enumerated aerobically on the same medium. The anaerobic counts on TSAS 6.5 were similar to the aerobic counts on TSA. Increases in both death and injury occurred when S. aureus was propagated in tryptic soy broth (TSB) plus 10% NaCl (TSBS) instead of TSB before thermal injury. Addition of catalase to TSA and TSA containing 7.5% NaCl (TSAS) increased the count to approximately the same levels on TSA and TSAS as that found following thermal injury after propagation in TSB. Catalase activity was 12-fold higher in stationary phase cells propagated in TSB than in TSBS. Indirect evidence indicates that toxic levels of H2O2 accumulated rapidly, causing one to two log decreases in enumeration after 30 to 60 min incubation on TSAS.

Variations in growth of Staphylococcus aureus 234 after heat stress in milk

“…Sodium chloride when ionized could exert lethal activity through osmotic effects, sodium ion toxicity or chlo-ride ion toxicity. The salt sensitivity of heat injured S aureus has also been attributed to hydrogen peroxide sensitivity and impairment of catalase production during repair of the injured cells (Bucker et al, 1979;Bucker and Martin, 1981). The presence of tellurite in the growth medium also resulted in an extension of the lag phase in the case of stressed cells of S aureus 234, as has been indicated in figure 3.…”

Superoxide dismutase activity in thermally stressed Staphylococcus aureus

“…DISCUSSION The superoxide radical and H202 are produced during the univalent reduction of molecular oxygen. The partial inactivation of catalase due to the synergistic effect of heat and NaCl has been well documented (1,2,4,6,13). This inactivation probably results in the accumulation of H202, subsequently leading to the death of the cell.…”

“…Martin et al (13) observed that the addition of catalase (EC 1.11.1.6) to high-NaCl-containing selective media, such as tryptic soy agar (TSA) plus 7% NaCl (TSAS), increased the enumeration of thermally stressed cells of Staphylococcus aureus up to 15,000-fold. The synergistic effects of heat, NaCl, and H202 on the decreased enumeration of thermally stressed cells of S. aureus have been further examined (1)(2)(3)(4)6). It appears that the combined effects of heat and NaCl result in the decreased activity of catalase, the enzyme responsible for the degradation of hydrogen peroxide (H202) in S. aureus.…”

Effect of free-radical scavengers on enumeration of thermally stressed cells of Staphylococcus aureus MF-31

“…The SOD from both Bacteroides distasonis and Bacteroides fragilis is also rapidly inactivated by exposure to 5 mM H202. Hydrogen peroxide can accumulate within the cell, owing to the partial inactivation of catalase caused by the synergistic effects of heat and NaCl (1,8,12,20). To determine whether the resulting accumulation of H202 might adversely affect staphylococcal SOD, H202 (5 or 10 mM) was added to cell lysates, and the SOD activity was determined after various time intervals (Fig.…”

“…Recently, the accumulation of hydrogen peroxide (H202) has been implicated as a major factor in the decreased enumeration of thermally stressed cells of Staphylococcus aureus on high-NaCl-containing selective media (1,8,12,20). The synergistic interaction of heat and NaCl results in the decreased activity of catalase, which in turn results in accumulation of H202 and, ultimately, cell death.…”