Effect of Nisin on the Outgrowth of Clostridium botulinum Spores

Nisin, an antibiotic produced by certain strains of Streptococcus lactis, is effective in preventing the outgrowth of Clostridium botulinum spores. Type A C. botulinum spores were the most resistant to the inhibitory action of nisin requiring 1000-2000 I.U. of nisin/ml for a 50% inhibition of outgrowth on TPYG agar plates. Type E spores were more sensitive requiring only 50-100 I.U./ml for 50% inhibition of outgrowth on TPYG agar plates. Type B spores displayed an intermediate level of sensitivity requiring 500-1000 I.U. of nisin/ml for 50% inhibition of outgrowth on TPYG agar plates. Similar levels of nisin were necessary to prevent spore outgrowth in TPYG broth and BHI broth over a 7-day incubation period. With prolonged incubation periods of up to 65 days in TPYG broth, spore outgrowth was observed sporadically at higher nisin levels with the type A and B spores which may indicate some decomposition of nisin with storage. Nisin levels of 5000 I.U./ml for the type A spores and 2000 I.U./ml for the type B spores and the Minnesota E spores were insufficient to prevent spore outgrowth by C. botulinurn in cooked meat medium. For the Beluga E spores, a nisin level of 2000 I.U./ml was necessary to prevent spore outgrowth in cooked meat medium. The need for higher levels of nisin in cooked medium to prevent spore outgrowth may be due to the binding of the nisin by meat particles.     

Temperature, pH, and Spore Load Effects on the Ability of Nisin to Prevent the Outgrowth of Clostridium botulinum Spores

The effectiveness of nisin in preventing the outgrowth of spores of Clostridium botulinum types A, B, and E in TPYG broth was profoundly affected by pH, temperature of heat-shocking, length of the heat-shocking period, and spore load. Nisin was considerably more effective at pH 6 than at either pH 7 or pH 8 in limiting the outgrowth of all six tested strains. Heat-damaged spores were also more sensitive to nisin. Both higher heat-shocking temperatures in the range 20-30°C higher than the optimal heat-shocking temperatures for the particular strain and longer heat-shocking periods served to lower the levels of nisin required to inhibit spore outgrowth. Nisin was more effective against spore loads of 10²spores/ml. than higher spore loads of 10³ or 10⁴ spores/ml with all of these variables taken into consideration, the order of sensitivity of the spores of the various strains of C. botulinum was strain 56A < strain 69A < strain 113 B = strain 213 B < strain Beluga E < strain Minnesota E     

Inhibitory effects of nisin against Clostridium perfringens food poisoning and nonfood-borne isolates

The enterotoxigenic Clostridium perfringens type A is the causative agent of C. perfringens type A food poisoning (FP) and nonfood-borne (NFB) human gastrointestinal diseases. Due to its ability to form highly resistant endospores, it has become a great concern to the meat industry to produce meat free of C. perfringens. In this study, we evaluated the antimicrobial effect of nisin against C. perfringens FP and NFB isolates. No inhibitory effect of nisin was observed against germination of spores of both FP and NFB isolates in laboratory medium. However, nisin effectively arrested outgrowth of germinated spores of C. perfringens in rich medium. Interestingly, germinated spores of NFB isolates possessed higher resistance to nisin than that of FP isolates. Furthermore, nisin exhibited inhibitory effect against vegetative growth of both FP and NFB isolates in laboratory medium, with vegetative cells of NFB isolates showing higher resistance than that of FP isolates. However, the antimicrobial activity of nisin against C. perfringens was significantly decreased in a meat model system. In conclusion, although nisin showed inhibitory effect against spore outgrowth and vegetative cells of C. perfringens FP and NFB isolates in laboratory conditions, no such effect was observed against C. perfringens spores inoculated into a meat model system.     

汤鸭的柔性杀菌工艺

研究了乳酸链球菌素(Nisin)及山梨酸钾复配在鸭肉熟制品的中的抑菌作用,通过添加Nisin抑制肉制品中的芽孢等耐热性菌体,从而降低杀菌强度。结果表明:当Nisin、山梨酸钾的质量分数分别为0.5g/kg、0.05g/kg时,杀菌条件可降至110℃、25min,产品保质期可以达到6个月。     

Effect of environmental parameters on growth kinetics of Bacillus cereus (ATCC 7004) after mild heat treatment

The influence of temperature (10 to 50 degrees C), initial pH (4.0 to 6.0) and sodium chloride concentration (0.5 to 3.0%) on the growth in nutrient broth and in meat extract of Bacillus cereus after mild heat treatment (90 degrees C--10 min) was determined. B. cereus spores survived after heating and they were able to germinate and grow in both media when post-treatment conditions were favourable. Heated B. cereus did not grow at 10 and 50 degrees C or in a medium with pH 4.0. Decreasing pH values and increasing levels of sodium chloride decreased growth rate and increased the lag phase of B. cereus. pH 4.5 was unable to prevent the growth of heated spores in a meat substrate with 0.5% NaCl at 12 degrees C. The combination of pH /=1.0% and temperatures /=60 degrees C could control heated B. cereus ATCC 7004 growth.     

Inactivation of Nisin by Glutathione in Fresh Meat

Matrix-assisted laser desorption/ionization time-of-flight mass spectrometry (MALDI-TOF MS) was used to determine the fate of nisin in meat products. Nisin in 0.02N HCl was added to fresh and cooked meat and meat juice and samples were stored at 4 °C overnight. Residual nisin solutions and meat juice and meat extract supernatants were analyzed for antimicrobial activity and for nisin. Nisin was recovered from cooked meat extract and cooked meat juice; however, only nisin bound to a food component was detected in fresh meat extract. Mass spectra for raw meat and juice showed a signal 307 Da greater than the mass of nisin. Results indicated that nisin was likely inactivated in raw meat by an enzymatic reaction with glutathione.     

Reduction of Clostridium sporogenes spore outgrowth in natural sausage casings using nisin

Preservation of natural sausage casings using dry salt or saturated brine is regarded as sufficient to inactivate vegetative pathogenic non-spore-forming bacteria present on the casings. Although the outgrowth of bacterial spores is prevented by salt or saturated brine preservation, these spores will remain present and develop into vegetative cells when conditions are more favourable. To prevent subsequent outgrowth additional preservation measures should be implemented. In the experiments described the use of nisin was evaluated to reduce outgrowth of spores in desalinated casings. The bacteriocin nisin was chosen because of its known efficacy against spore-forming bacteria and their spores in various foodstuffs. Clostridium spore suspensions (Clostridium sporogenes, ATCC 3584) were used in two concentrations to inoculate three nisin concentrations (10, 50, 100 μg/mL) in water containing gamma-irradiated casings. Additionally, the binding of nisin to casings, using ¹⁴C-labeled nisin Z and subsequent availability of nisin were evaluated. Results demonstrate that nisin is partly reversibly bound to casings and can reduce the outgrowth of Clostridium spores in the model used by approximately 1 log₁₀ (90%). However, the biological relevance of these results needs to be determined further by conducting industrial trials before any recommendation can be made on the practical implementation of nisin in the preservation of natural sausage casings.     

Thermal resistance of bacterial spores in milk-based beverages supplemented with nisin.

The effect of nisin, added in the form of Nisaplin, on the thermal resistance of bacterial spores and the effects of medium composition, exposure time, and pH on nisin enhancement of heat sensitivity were evaluated. Nisin apparently required specific nutrients to sensitize spores to heat. For example, D130 degrees C values of approximately 10 s were observed in sodium phosphate buffer with and without 6% sucrose with no significant (P> or =0.05) differences detected as a result of increased nisin concentration. In a nutrient-rich chocolate milk model system (CMMS), increasing either the time of exposure to nisin (5, 15, or 24 h) before heating or nisin concentration (0, 2,000, or 4,000 IU/ml) increased the sensitivity of Bacillus stearothermophilus spores to heat. In the CMMS with 10 to 12% fat cocoa powder, increasing nisin concentration (at 5 h of exposure) significantly (P< or =0.05) reduced D130 degrees C values; D130 degrees C values were 21.7, 17.2, and 17.8 s, respectively, for the 0-, 2,000-, and 4,000-IU/ ml nisin treatments. Fifteen and 24 h of exposure further reduced D130 degrees C values in the nisin-containing treatments compared to the control (0 IU of nisin per ml). A lower-fat CMMS (0 to 1% fat cocoa powder) had lower D130 degrees C values (19.3, 15.8, and 14.7 s for the 0-, 2,000-, and 4,000-IU/ml nisin treatments, respectively). Nisin activity was enhanced by lowering pH in the CMMS (10 to 12% fat cocoa powder), with reductions in D130 degrees C values across all pH values (ranging from 18.0% at pH 6.4 to 41.9% at pH 5.0). zD values were 9.6, 9.0, and 8.4 degrees C for the 0-, 2,000-, and 4,000-IU/ml nisin treatments, respectively. Spores of B. licheniformis yielded results similar to those obtained with B. stearothermophilus. For example, decreasing CMMS (10 to 12% fat cocoa powder) pH values from 6.4 to 5.0 produced D100 degrees C values of 3.3, 2.8, and 2.8 min (pH 6.4) and 1.0, 0.8, and 0.8 min (pH 5.0) for the 0-, 2,000-, and 4,000-IU/ml nisin treatments. This study clearly verified that the addition of Nisaplin to dairy-based beverages, such as a chocolate milk drink, or other foods intended to be heated reduces the thermal resistance of selected bacterial spores. Increased spore sensitivity to heat may provide food processors with an opportunity to reduce their thermal processes and expenses while maintaining product quality, functionality, and shelf stability.     

Nisin-curvaticin 13 combinations for avoiding the regrowth of bacteriocin resistant cells of Listeria monocytogenes ATCC 15313

Nisin (25-100 IU/ml) and curvaticin 13 (160 AU/ml), a bacteriocin produced by Lactobacillus curvatus SB13, were shown to have a bactericidal effect against Listeria monocytogenes ATCC 15313 in TSB-YE broth (pH 6.5), but it was only transitory. Regrowth was not due to the loss of bacteriocin activity. Cells surviving nisin or curvaticin 13 were more resistant to the respective bacteriocin than the parental strain. Survivors to curvaticin 13 were resistant to the class IIa bacteriocins (camocin CP5, pediocin AcH) but remained sensitive to nisin. The frequencies of spontaneous nisin resistants decreased with increasing bacteriocin concentration and the presence of salts (NaCl, K2HPO4). The behaviour of nisin (1000 IU/ml) or curvaticin 13 (640 AU/ml) resistant variants (Nis1000, Curv645) was investigated in the presence of nisin (100 IU/ml) or curvaticin 13 (320 AU/ml) at 22 and 37 degrees C, and compared with that of the parental strain. The effectiveness of nisin was the same at both temperatures, whereas curvaticin 13 displayed a faster bactericidal action at 37 degrees C. Nis1000 cells were less sensitive to curvaticin 13 than the parental strain, whereas Curv640 cells were more sensitive to nisin than the parental strain. Simultaneous or sequential additions of nisin (50 IU/ml) and curvaticin 13 (160 AU/ml) were performed at 22 degrees C in broth inoculated with the parental strain. All combinations induced a greater inhibitory effect than the use of a single bacteriocin. Simultaneous addition of bacteriocins at t0 led to the absence of viable cells in the broth after 48 h.     

Sporulation and Heat Resistance of Spores from a Clostridium sp. RKD

A Clostridium sp. RKD isolated from the intestine of decaying fish, showing 99% sequence identity with Clostridium tetani at a 16S rRNA level, produced a neurotoxin that was neutralized by botulinum antitoxin (A+B+E). It also showed an amplification of near‐expected size when polymerase chain reaction (PCR) was performed using group‐ and type‐specific primers for botulinum neurotoxin type B. The isolate exhibited differences with both C. tetani and Clostridium botulinum with respect to phenotypic characteristics and chemotaxo‐nomic markers. Spore production was optimized with respect to media composition and stage of growth. Time‐dependant examination of sporulation revealed 2.6% to 49.0% spores in the late stationary phase culture when grown in different broth media. A simpler method for spore production and isolation from culture grown in tryptose sulfite cycloserine (TSC)/anaerobic agar sandwich resulted in >95% sporulation, which could be purified to near homogeneity by a simple 2‐step procedure. Thermal resistance of spores revealed a biphasic inactivation at lower temperatures with D values for linear inactivation varying from 26.6, 8.0, and 4.3 min at 70 °C, 80 °C, and 90 °C, respectively. The z values of 7.86 °C and 10.47 °C were obtained in the linear and tail regions, respectively. The Weibull parameter b values at 70 °C, 80 °C, and 90 °C were 27.38, 3.55, and 0.99, respectively, with a z’ value of 13.869 °C. The shape parameter n at 70 °C, 80 °C, and 90 °C were 0.63, 0.55, 0.45, respectively. Spores produced on 2 different media (cooked meat medium [CMM] and trypticase peptone yeast‐extract glucose [TPYG] agar) exhibited differences in heat resistance. The addition of lysozyme (50 jj.g/mL) before heat treatment resulted in increased thermal resistance of spores.     

INDIVIDUAL AND COMBINED LISTERICIDAL EFFECTS OF SODIUM LACTATE, POTASSIUM SORBATE, NISIN AND CURING SALTS AT REFRIGERATION TEMPERATURE

The individual and combined antilisterial activity of the preservatives sodium lactate (4%), potassium sorbate (0.3%) and nisin (400 IU/ml), in either the presence or absence of the curing salts nitrite (125 ppm) and polyphosphate (0.5%), was assessed in buffered BHI broth (pH 5.5) during incubation at 4C. A cocktail of the strain Listeria monocytogenes NCTC 7973 and two food derived strains was used as the inoculum in challenge studies. In the absence of the preservatives , L. monocytogenes grew in the presence of polyphosphate but not in the presence of nitrite or a combination of nitrite and polyphosphate. The antilisterial action of nitrite was predominantly bacteriostatic in nature. Lactate acting alone, or in the presence of curing salts, produced a bacteriostatic effect. Sorbate acting alone had a bacteriostatic effect. Sorbate acting in the presence of nitrite or nitrite and polyphosphate produced a marked listericidal effect, reducing the population by 6.7 logs and 5.4 logs, respectively. Nisin acting alone produced an almost immediate 90% listericidal response (1 log population decrease), but initial numbers were restored within 14 days by regrowth. Regrowth was eliminated when nisin was used in combination with lactate, nitrite or nitrite and polyphosphate. The combination of lactate and sorbate offered no advantage over the use of sorbate alone. Sorbate and nisin acting in combination produced an enhanced listericidal effect, which was also seen in the presence of curing salts, but was delayed. No listericidal advantage over sorbate-nisin combination was achieved through the use of the lactate-sorbate-nisin combination. The combined use of sorbate and nisin offers promise as a means of eliminating L. monocytogenes from low pH cured meat products. The efficacy of this preservative combination remains to be evaluated in a meat system before its practical application can be considered .     

Inhibition of Alicyclobacillus acidoterrestris spores by natural compounds

The aim of this study was to evaluate the antimicrobial effectiveness of some natural compounds (cinnamaldehyde, eugenol, limonene) and sodium benzoate against two strains of Alicyclobacillus acidoterrestris (c8 and γ4). The antimicrobial compounds (10–500 ppm) were solved in malt extract broth, inoculated separately with 10³ spores mL⁻¹ of each strain; the samples were incubated at 44 °C and the outgrowth of spores was evaluated every day by measuring the absorbance of the medium at 420 nm; inoculated samples without active compounds were used as controls. The results pointed out that limonene was not effective in inhibiting the outgrowth of A. acidoterrestris spores; 100 ppm of cinnamaldehyde or sodium benzoate slowed the spore germination, whereas 500 ppm of eugenol inhibited the growth of microbial targets for 13 days. Strain c8 was more resistant than isolate γ4 and cinnamaldehyde was the most effective compound in inhibiting the germination of A. acidoterrestris spores.     

Nisin in milk sensitizes Bacillus spores to heat and prevents recovery of survivors.

Decimal reduction times (D values) were determined for Bacillus cereus T spores and B. stearothermophilus ATCC 12980 spores in skim milk supplemented with various concentrations (0, 2,000, and 4,000 IU/ml) of the bacteriocin nisin by using an immersed, sealed capillary tube procedure. For both organisms, the addition of nisin lowered the apparent D values. For B. cereus, the addition of 2,000 IU of nisin per ml to skim milk before heating significantly (P< or =0.05) lowered the apparent D value compared to the control treatment. The D values at 97 degrees C were 7.0, 4.8, and 4.7 min for the control and 2,000- and 4,000-IU/ml nisin treatments, respectively. At 103 degrees C, the D values were 1.5, 0.85, and 0.88 min for the control and 2,000-and 4,000-IU/ml nisin treatments. When calculated across both nisin treatments, the mean reductions in apparent D values at 97, 100, and 103 degrees C due to addition of nisin in comparison to the controls were 32, 20, and 42%, respectively. The zD values for B. cereus ranged from 8.0 to 8.9 degrees C. With B. stearothermophilus, the apparent D values at 130 degrees C were reduced by 13 and 21% respectively, because of the presence of 2,000 or 4,000 IU of nisin per ml. The D values were 16.0, 13.8, and 12.5 s for the control and 2,000- and 4,000-IU/ml nisin treatments, respectively. There was a significant (P< or =0.05) decrease in the apparent D value between the control and 4,000-IU/ml treatment. Overall, log populations of survivors for B. stearothermophilus compared to the control were lower at any given sampling time due to the presence of nisin. The results of these studies suggest that spore control is likely due to enhanced sensitivity of spores to heat and the presence of residual nisin in the recovery medium that could prevent outgrowth of survivors.     

Proteolytic Clostridium botulinum growth at 12–48°C simulating the cooling of cooked meat: development of a predictive model

The objective of this study was to develop a model to predict the germination, outgrowth and lag (GOL), and exponential growth rates of Clostridium botulinum from spores at temperatures (12–48°C) applicable to the cooling of cooked meat products. The growth medium, Reinforced Clostridial medium (RCM) supplemented with oxyrase enzyme to create suitable anaerobic conditions, was inoculated with approximately 4 log₁₀spores ml⁻¹. Clostridium botulinum populations were determined at appropriate intervals by plating onto RCM. Clostridium botulinum growth from spores was not observed at temperatures <12°C or >48°C for up to 3 weeks. Growth curves were determined by fitting Gompertz functions to the data. From the parameters of the Gompertz function the growth characteristics, GOL times and exponential growth rates were calculated. These growth characteristics were subsequently described by Ratkowsky functions using temperature as the independent variable. Closed form equations were developed that allow for predicting relative growth for a general cooling scenario. By applying multivariate statistical procedures, the standard errors and confidence intervals were computed on the predictions of the amount of relative growth for a cooling scenario. The predictive model is capable of predicting spore outgrowth and multiplication for general cooling scenarios, for suitable but un-verified mathematical assumptions, and should aid in evaluating the safety of cooked products after cooling.     

Use of nisin for inhibition of Alicyclobacillus acidoterrestris in acidic drinks

The inhibitory effects of nisin on the growth of the thermoacidophilic spoilage bacteriumAlicyclobacillus acidoterrestris were investigated for the purpose of preventing flat-sour-type spoilage in acidic drinks. Minimum inhibitory concentration values of nisin against the spores were from less than 0·78 to 12·5 IU ml⁻¹and from 25 to 100 IU ml⁻¹on mYPGA plates at pH 3·4 and 4·2, respectively. The levels of nisin inhibition against the vegetative cells were, however, higher than those of the spores. In determining the effects of nisin on the thermal resistance of A. acidoterrestris spores, the addition of nisin contributed to the reduction of the thermal resistance of A. acidoterrestris spores in acidic drinks. Furthermore, the outgrowth of A. acidoterrestris spores was inhibited by the addition of 25–50 IU ml⁻¹nisin in both orange and fruit-mixed drinks, but was not inhibited by the higher level (600 IU ml⁻¹) addition in a clear-apple drink. From these findings, we conclude that it would be useful to add nisin for preventing the spoilage caused by A. acidoterrestris in all but clear-apple acidic drinks.     

The effect of nisin on growth kinetics from activated Bacillus cereus spores in cooked rice and in milk

The growth kinetics of germinated cells from activated spores of Bacillus cereus in cooked white rice and in milk were evaluated at different temperatures for control samples and for samples with 25 microg of nisin per ml added. Nisin was applied in the form of Nisaplin (10(6) IU/g), which contained 25,000 microg of nisin per g. The length of the lag phase for cooked white rice controls was 120 h at 10 degrees C, 8 h at 25 degrees C, and 2.5 h at 33 degrees C. The generation times for cooked rice were 327.7 min at 10 degrees C, 59.0 min at 25 degrees C, and 42.3 min at 33 degrees C; those for milk without nisin were 297.0 min at 20 degrees C, 31.2 min at 30 degrees C, 28.6 min at 35 degrees C, and 33.7 min at 40 degrees C; and those for milk with nisin added were 277.2 min at 20 degrees C, 66.9 min at 30 degrees C, and 66.4 min at 35 degrees C. No development of B. cereus was observed for milk with nisin added at 40 degrees C for 12 h, in which germinated cells decreased by a decimal reduction time (D) of 4.7 h. A temperature of 45 degrees C was shown to be harmful to B. cereus, decreasing the germinated cells in both formulations with D-values of 4.3 to 4.6 h. Similar inhibition of cell growth at 40 degrees C was not observed with lower nisin concentrations.     

Synergistic bactericidal effect of carvacrol, cinnamaldehyde or thymol and refrigeration to inhibit Bacillus cereus in carrot broth

Possible use of three different essential oil components as natural food preservatives was studied by examining their influence in the kinetics of growth from activated spores of four Bacillus cereus strains in tyndallized carrot broth over the temperature range 5-16 degrees C. Selected low concentrations of carvacrol, cinnamaldehyde, or thymol showed a clear antibacterial activity against B. cereus in the vegetable substrate. The addition of 2 microl cinnamaldehyde or 20 mg thymol to 100 ml of broth in combination with refrigeration temperatures (相似文献   

The influence of nisin on the thermal resistance of Bacillus cereus

Decimal reduction times (D-values) at cooking and autoclaving temperatures (80 to 120 degrees C) of spores of Bacillus cereus ATCC 1479-8 in rice and milk (13% wt/vol) supplemented with nisin (25 microg/ml) were evaluated. The mean D-values at 97.8 degrees C in cooked white rice, phosphate buffer (pH 7.0), and rice water (pH 6.7) were 3.62, 1,99, and 1.34 min, respectively. From 80 to 100 degrees C, the mean reduction in D-values due to the addition of nisin to milk was 40%. The D-value at 110 degrees C was approximately 0.86 min for milk (control) and milk with nisin. The z-values ranged from 7.32 degrees C (phosphate buffer) to 10.37 degrees C (milk control).     

Effect of post-slaughter processing and freezing on the functionality of hot-boned meat from young bull

The effects of variation in the times of mincing post mortem (2, 4, or 6 h), pre-rigor salting (1.5% wt wt ) and freezing rate [fast (10 min, liquid nitrogen); medium (4-6 h at -40 °C and 0.8 m s(-1) air velocity); or slow (36-38 h at -10 °C and 0.1 m s(-1) air velocity followed by 12 h at -20 °C and 0.1 m s(-1) air velocity)] on the functionality of young bull meat were examined using hot-boned forequarters. At 52 h post packaging, the meat was thawed (72 h at 4 °C), its pH measured, and it was used to make finely comminuted batters. Cook yield and stress and strain of the cooked batters were measured. Time of mincing had no effect on meat pH, cook yield or stress and strain. There was a significant interaction (P < 0.05) between pre-rigor salting and freezing rate for pH. Freezing rate did not affect the pH of pre-rigor salted meat whereas the pH of unsalted pre-rigor meat was highest at the fastest freezing rate. Meat salted pre-rigor had a significantly (P < 0.05) higher pH than the post-rigor chilled control. Pre-rigor salting decreased the stress values of cooked batter whereas the slowest freezing rate increased stress. Stress and strain values for cooked batters from thawed meat were not significantly different from the values for batters made from the unfrozen control. Cook yields of batters made from pre-rigor frozen meat were higher than that of the postrigor control but not significantly so. The results indicate that suppliers can use pre-rigor salted and frozen meat when manufacturing comminuted products without major detrimental effects on the cook yield and texture of the finished product.     

Impact of intestinal microbiota and gastrointestinal conditions on the in vitro survival and growth of Bacillus cereus

Ingestion of B. cereus can result in diarrhea, if these bacteria survive gastrointestinal passage and achieve growth and enterotoxin production in the small intestine. The gastrointestinal survival of vegetative cells and spores of the diarrheal food poisoning strain B. cereus NVH 1230-88 was investigated during in vitro batch experiments simulating the stomach, duodenum and ileum using simulation media and competing intestinal microbiota. All spores and approx. 30% of the vegetative B. cereus cells survived the 2 h incubation in gastric medium with pH 4.0. Sterile intestinal medium induced germination of spores and enabled outgrowth of vegetative cells to approx. 7 log CFU/mL. The behavior of B. cereus in the intestinal environment with competing intestinal bacteria was determined by their relative concentrations. Besides the numbers of intestinal bacteria, the nutrition and composition of the intestinal community were also very important for the growth inhibition of B. cereus.