Repair and enterotoxin synthesis by Staphylococcus aureus after thermal shock.

To study repair and enterotoxin synthesis, four staphylococcal strains (FRI-100, FRI-137, FRI-472, and S6) were subjected to sublethal heat treatment, transferred to four liquid repair media (1% powdered skim milk in distilled water, complex medium, M9 minimal salt medium, and saline solution), and then incubated at different temperatures. Powdered skim milk proved to be the most efficient medium for promoting the repair of injured cells, particularly at 37 degrees C. Minimal salt medium also gave good results. Salt tolerance also increased at 4 degrees C, although it did not reach normal values. After 6 h of incubation at 37 degrees C in powdered skim milk, strain FRI-100 synthesized detectable amounts of enterotoxin A. After 10 h of incubation in the same medium at the same temperature, enterotoxins were detected in all of the strains.     

Staphylococcus aureus S-6: factors affecting its growth, enterotoxin B production and exoprotein formation

The growth of Staphylococcus aureus S-6, enterotoxin production and exoprotein formation were always higher in NZ-amine A medium compared with brain heart infusion medium. The formation of exoproteins, including enterotoxin B, per bacterial cell in static culture was influenced by the addition of glucose. Lactate and amino acids were used by Staph. aureus S-6 in media without additional glucose. When both media were supplemented with glucose, lactic and acetic acids were produced. Different electrophoretic patterns for exoprotein formation were obtained when the organism was grown in shaken or static culture.     

Staphylococcus aureus S-6: factors affecting its growth, enterotoxin B production and exoprotein formation

The growth of Staphylococcus aureus S-6, enterotoxin production and exoprotein formation were always higher in NZ-amine A medium compared with brain heart infusion medium. The formation of exoproteins, including enterotoxin B, per bacterial cell in static culture was influenced by the addition of glucose.
Lactate and amino acids were used by Staph. aureus S-6 in media without additional glucose. When both media were supplemented with glucose, lactic and acetic acids were produced. Different electrophoretic patterns for exoprotein formation were obtained when the organism was grown in shaken or static culture.     

Effect of sodium chloride and pH on enterotoxin B production

Genigeorgis, Constantin (University of California, Davis), and Walter W. Sadler. Effect of sodium chloride and pH on enterotoxin B production. J. Bacteriol. 92:1383-1387. 1966.-The growth and production of enterotoxin B by Staphylococcus aureus strain S-6 in Brain Heart Infusion broth with 2 to 16% sodium chloride and an initial pH of 5.1 to 6.9 was studied during a 10-day incubation period at 37 C. Growth was good at pH 6.9 and with a 16% concentration of salt, but no cells survived after 10 days of incubation at pH 5.1 and with a 16% concentration of salt. With geldiffusion technique, enterotoxin B was detected in broth with pH 6.9 and up to 10% salt or pH 5.1 and up to 4% salt. Growth and enterotoxin production were better when pH was increased and salt concentration was decreased. The dependence of toxin production on the interaction of these two factors was demonstrated.     

Growth and enterotoxin A production by Staphylococcus aureus S6 in Manchego type cheese

(from cow, goat and sheep) was inoculated with Staphylococcus aureus strain S6, which is generally considered to be a strong enterotoxin B producer and a weak enterotoxin A producer. It was then used to make Manchego type cheese as prepared industrially. Two concentrations of starter culture (1% and 0.1%) were tested. Staphylococcal growth was good in both but better in the more dilute culture. Staphylococcal enterotoxin B was not detected at any stage of the ripening process of any cheese tested. However enterotoxin A was detected in both starter concentrations, reaching as high as 769 ng/100 g of cheese in the 0.1% starter batches.     

Growth and enterotoxin A production by Staphylococcus aureus S6 in Manchego type cheese

Milk (from cow, goat and sheep) was inoculated with Staphylococcus aureus strain S6, which is generally considered to be a strong enterotoxin B producer and a weak enterotoxin A producer. It was then used to make Manchego type cheese as prepared industrially. Two concentrations of starter culture (1% and 0.1%) were tested. Staphylococcal growth was good in both but better in the more dilute culture. Staphylococcal enterotoxin B was not detected at any stage of the ripening process of any cheese tested. However enterotoxin A was detected in both starter concentrations, reaching as high as 769 ng/100 g of cheese in the 0.1% starter batches.     

The effect of the olive phenolic compound, oleuropein, on growth and enterotoxin B production by Staphylococcus aureus

The presence of low concentrations (0.1% w/v) of oleuropein, a phenolic compound extracted from olives, delayed the growth of Staphylococcus aureus in NZ amine A and brain heart infusion media modified by the addition of growth factors and glucose (NZA + and BHI +), as indicated by changes in conductance, whilst higher concentrations (0.4–0.6% w/v) inhibited growth completely. Intermediate concentrations of oleuropein (0.2%) prevented growth in BHI + but allowed growth to occur in NZA + despite an extended lag phase (30 h). Concentrations of oleuropein > 0.2% inhibited growth and production of enterotoxin B in both types of media. Lower levels (0.1%) did not affect the final viable count and production of toxin in BHI + but decreased the number of viable organisms and reduced the toxin production in NZA + by eightfold. An increase in the concentration of oleuropein resulted in a decrease in the amount of glucose assimilated and consequently the amount of lactate produced. In addition, oleuropein prevented the secretion of a number of exoproteins. Addition of oleuropein during the exponential phase appeared to have no effect on the growth of Staph. aureus in NZA +.     

Absence or presence of glucose in growth medium and its effect on heat injury inStaphylococcus aureus

Summary Staphylococcus aureus 196E, when grown in a glucose (0.25% wt./vol.)-containing medium, produced cells that would undergo injury when subjected to sublethal heat conditions (45 min at 50°C); however, if glucose was omitted from the growth medium, the extent of injury was greatly reduced. Media containing glucose sterilized by filtration or by separate autoclaving produced cells equal in injury susceptibility to medium in which glucose was autoclaved as part of the medium components. Injury also occurred when other sugars such as fructose, mannose, maltose, or lactose were substituted for glucose. Sugar-containing media that producedStaphylococcus aureus of maximal susceptibility to heat injury reached a pH of approximately 6 or lower during growth of the cells. Incubation of staphylococci in growth medium acidified with acetic or lactic acids or HCl did not lead to cells that would undergo injury under the stated conditions. The stimulatory effect of glucose on injury appears to be related to the metabolism of the sugar byStaphylococcus aureus.Agricultural Research Service, U.S. Department of Agriculture. Reference to brand or firm name does not constitute endorsement by the U.S. Department of Agriculture over others of a similar nature not mentioned.     

Conditions affecting growth and enterotoxin production by Staphylococcus aureus on temperature-abused chicken meat

Growth of Staphylococcus aureus at 15°C, with and without addition of representative spoilage bacteria, was studied in cooked, whole chicken meat and chicken broth. In the absence of competitors, the organism grew better in broth culture than on whole meat, but multiplied more slowly in broth when other organisms were present, even from twice the previous level of inoculum. The presence of competitors had no marked effect on the growth of Staph. aureus on whole meat. Enterotoxin A was not produced at 15°C on either whole meat or in broth, and occurred at 20°C only in pure culture. At 30° and 37°C, toxin was produced whether or not competitors were present. Toxin production by Staph. aureus appeared to be influenced more by growth temperature than by bacterial competition.     

Recovery, growth, and production of heat-stable enterotoxin by Escherichia coli after copper-induced injury

Exposure of enterotoxigenic Escherichia coli strains to a sublethal concentration (0.75 mg/liter) of copper for 3 days at 4 degrees C induced sensitivity to deoxycholate (0.1%). When placed in a complex (brain heart infusion) or a defined amino acid salt medium, the copper-injured cells recovered their tolerance to deoxycholate in 3 and 6 h, respectively, and commenced active growth. Growth and heat-stable enterotoxin production of uninjured and copper-injured cells were studied in brain heart infusion medium. A slightly altered growth curve and an initial slow rate of toxin production were observed in injured cells when compared with those corresponding uninjured controls. However, maximum heat-stable enterotoxin levels in injured cultures were comparable to those produced by uninjured cells, suggesting that the enterotoxigenic potential of copper-injured cells was fully retained.     

Effect of moderately acidic pH on heat resistance of Clostridium sporogenes spores in phosphate buffer and in buffered pea puree.

The effect of pH in the range 5.0 to 7.0 on the thermal destruction of spores of Clostridium sporogenes putrefactive anaerobe 3679 was examined by three methods: a capillary tube method in which spores were suspended in phosphate buffers, a thermoresistometer method in which spores were suspended in buffered pea puree adjusted to the same set of pH values, and a thermal death time can method in which spores were again suspended in buffered pea puree. The results indicated that increasing acidity is, in general, accompanied by decreasing heat resistance, although the pH effect was more pronounced at the higher than at the lower processing temperatures. Certain pH values appear to be critical, as they produced, in all three sets of experiments, effects which would not be predicted by the overall relationship between acidity and spore heat resistance. Differences between heat resistance in phosphate buffer as compared with that in pea puree adjusted to the same pH were also noted. D-values in buffer were found to be lower than those in pea puree, except at the highest temperatures coupled with the lowest pH values. The differences between buffer D-value and pea puree D-value were found to increase with increasing pH and with decreasing temperature. On the other hand, at all pH values examined, z-values determined in buffer were somewhat higher than those determined in pea puree adjusted to the same pH.     

Effect of Cd2+ on phosphate uptake by cadmium-resistant and cadmium-sensitive Staphylococcus aureus.

The effect of Cd2+ on phosphate (Pi) uptake was investigated in the growing cells of Cd(2+)-resistant Staphylococcus aureus 1781OR and Cd(2+)-sensitive S. aureus 17810S. Inhibitor and ionophore studies showed that 32Pi uptake in the two strains occurred via the Pi porter down pH gradient (delta pH) generated by the respiratory chain. Cd2+ inhibited 32Pi uptake in the cadmium-sensitive strain 1781OS at all concentrations used (10 microM-1 mM). In strain 1781OR, possessing the plasmid-coded Cd2+ efflux system, 10-100 microM Cd2+ did not inhibit 32Pi uptake. Even at 1 mM Cd2+, inhibition of 32Pi uptake in strain 1781OR was reversed when the external Cd2+ was chelated with cysteine and activity of Cd2+ efflux system was restored. Cd2+ efflux induced by cysteine was energized either by membrane potential (delta psi) or by delta pH, which indicated that electrochemical gradient of protons (delta mu H+) was required for this efflux.     

Influences of sigmaB and agr on expression of staphylococcal enterotoxin B (seb) in Staphylococcus aureus

In Staphylococcus aureus, enterotoxin B (SEB) is a superantigen that activates host interleukins and induces adverse responses, ranging from food poisoning to toxic shock. The alternate sigma factor, sigmaB (SigmaB), and agr are two known regulators of S. aureus. Northern blots of strain COL, a sigB-positive strain, showed an inverse correlation between sigmaB expression and seb message. seb expression was also measured as a function of a seb promoter linked to green fluorescent protein (GFP) expression in RN6390, COL, and Newman. In sigB mutants of RN6390, SH1000, COL, and Newman, seb promoter activities, as measured by GFP expression, increased relative to the respective parental types but at differing levels, suggesting alternate strain-specific regulation. In agr mutants of RN6390 and Newman, seb promoter activities were intermediate between the high level seen for the sigB mutant and the low level in the sigB active strains. A sigB agr double mutant of RN6390 displayed lower GFP expression than the agr mutant. These results suggest that while sigmaB and agr regulate seb expression in a divergent manner, other activator(s) of seb that depend on sigB expression may be present in S. aureus.