Bacillus Stearothermophilus Spores Research Articles

Dose–response effects of raw potato starch on small-intestinal escape, large-bowel fermentation and gut transit time in the rat

This study was designed to quantify starch digestion within the small and large bowels separately when raw potato starch (RPS) was included at 0-240 g/kg in diets fed to growing male Wistar rats. RPS was incorporated in the diets at the expense of maize starch which was expected to be almost completely digested in the small bowel. The digestibility of the maize starch was 0.99 but only 0.28 of the RPS was digested before the terminal ileum so that with increasing intakes of RPS there was a progressive increase in starch supply to the large bowel (LB). Of this starch 0.77, 0.72 and 0.73 was fermented in the large bowel when RPS constituted 80, 160 and 240 g/kg diet respectively. With increasing RPS intake, there was a curvilinear response in molar proportion of butyrate in caecal contents with a maximum value at about 80 g RPS/kg diet. The molar proportion of acetate increased linearly, that of propionate was unchanged, whilst proportions of the minor short-chain fatty acids all declined markedly with increasing RPS intake. The novel marker Bacillus stearothermophilus spores (BSS) was compared with CrEDTA in estimation of whole-gut mean transit time (MTT) when given together in a single test meal. Whilst estimates of MTT for the two markers were strongly correlated within individual rats (r2 0.72), BSS produced estimates that were 13 h longer than those based on CrEDTA. Neither marker detected a change in MTT with increasing RPS intake but, with both, the rate constant (k1) for the 'largest mixing pool' declined significantly (P < 0.001) as dietary RPS concentration was changed from 0-240 g/kg.

Development and Validation of a Mathematical Model for HTST Processing of Foods Containing Large Particles

A mathematical treatment for a heat penetration phenomenon with variable boundary conditions is presented. The system of differential equations for determining the unsteady-state temperature distribution inside a particle was solved by use of spectral methods as a new tool in food process development. A preliminary study was conducted on the use of a mathematical model to predict lethality in a sterilizing process. The model was validated using a calibrated time-temperature integrator (TTI) with immobilized Bacillus stearothermophilus spores, commonly used in TTIs for process validation. A comparison between the experimental data using Bacillus stearothermophilus and the predicted data obtained with the proposed model showed good agreement.

A time temperature integrator for particulated foods: thermal process evaluation

A time temperature integrator (TTI) was developed by immobilizing Bacillus stearothermophilus spores in a cylindrical particle consisting of an alginate-starch-mushroom puree. The particle showed homogeneous spore distribution, and when heated over a temperature range of 121 – 130° C negligible spore leakage was observed after the thermal process. The experimental data on spore survivor levels obtained for each temperature-time combination were compared with theoretical predictions using a mathematical model. The results showed a good correlation between the experimental and theoretical data. All these results provide evidence that this artificial particle could be a very reliable TTI for monitoring the thermal impact on micro-organisms during validating sterilization processes in continuous aseptic systems.

Bacterial Killing Ability of 10% Ethylene Oxide Plus 90% Hydrochlorofluorocarbon Sterilizing Gas

Objectives: To use a serum and salt challenge in narrow-lumen carriers to evaluate a 10% ethylene oxide plus 90% hydrochlorofluorocarbon (EO-HCFC) sterilant mixture in a retrofitted 12/88 sterilizer as an alternative to the banned chlorofluorocarbon-ethylene oxide (EO) sterilant mixture. Design: An EO-HCFC sterilizing gas mixture in a retrofitted 12/88 sterilizer was compared to 100% ethylene oxide (100% EO) sterilizing gas to determine its relative ability to kill seven different bacteria (Escherichia coli, Pseudomonas aeruginosa, Enterococcus faecalis, Bacillus subtilis spores, Bacillus stearothermophilus spores, Bacillus circulans spores, and Mycobacterium chelonei) in the presence or absence of a combined 10% serum and 0.65% salt challenge using both penicylinders (PC) and long narrowlumen (LU) carriers. Results: The EO-HCFC sterilant mixture (96% sterile carriers) was equivalent to the 100% EO sterilant (98% sterile carriers) for killing vegetative organisms, as well as spore suspensions, on the 27 PC and 27 LU carriers in the absence of serum and salt. In the presence of serum and salt, the EO-HCFC sterilant mixture was markedly better than the 100% EO sterilant at reducing the bacterial load on the 63 PC carriers (95% vs 62% sterile PC carriers, respectively), whereas both sterilizers were equivalent for the 63 LU carriers (49% vs 40% sterile LU carriers, respectively). Of the seven test organisms, E faecalis, B subtilis, B stearothermophilus, and B circulans were the most difficult to kill for both PC and LU carriers when serum and salt were present. Conclusions: The data presented in this report indicate that the EO-HCFC sterilant mixture is an effective alternative for gas sterilization. Indeed, the efficiency of bacterial killing for the EO-HCFC sterilant mixture was similar to that achieved by the 12/88 EO-CFC sterilant mixture.

Bacterial killing ability of 10% ethylene oxide plus 90% hydrochlorofluorocarbon sterilizing gas.

To use a serum and salt challenge in narrow-lumen carriers to evaluate a 10% ethylene oxide plus 90% hydrochlorofluorocarbon (EO-HCFC) sterilant mixture in a retrofitted 12/88 sterilizer as an alternative to the banned chlorofluorocarbon-ethylene oxide (EO) sterilant mixture. An EO-HCFC sterilizing gas mixture in a retrofitted 12/88 sterilizer was compared to 100% ethylene oxide (100% EO) sterilizing gas to determine its relative ability to kill seven different bacteria (Escherichia coli, Pseudomonas aeruginosa, Enterococcus faecalis, Bacillus subtilis spores, Bacillus stearothermophilus spores, Bacillus circulans spores, and Mycobacterium chelonei) in the presence or absence of a combined 10% serum and 0.65% salt challenge using both penicylinders (PC) and long narrow-lumen (LU) carriers. The EO-HCFC sterilant mixture (96% sterile carriers) was equivalent to the 100% EO sterilant (98% sterile carriers) for killing vegetative organisms, as well as spore suspensions, on the 27 PC and 27 LU carriers in the absence of serum and salt. In the presence of serum and salt, the EO-HCFC sterilant mixture was markedly better than the 100% EO sterilant at reducing the bacterial load on the 63 PC carriers (95% vs 62% sterile PC carriers, respectively), whereas both sterilizers were equivalent for the 63 LU carriers (49% vs 40% sterile LU carriers, respectively). Of the seven test organisms, E faecalis, B subtilis, B stearothermophilus, and B circulans were the most difficult to kill for both PC and LU carriers when serum and salt were present. The data presented in this report indicate that the EO-HCFC sterilant mixture is an effective alternative for gas sterilization. Indeed, the efficiency of bacterial killing for the EO-HCFC sterilant mixture was similar to that achieved by the 12/88 EO-CFC sterilant mixture.

Use of Bacillus stearothermophilus spores as a marker for estimating digesta passage rate from the rumen in cattle

Abstract Chromium-mordanted NDF, Co-EDTA and a Bacillus stearothermophilus spore (BSS) suspension were administered through rumen cannulae to three steers and six mature heifers with an average weight of 659 ± 6 kg in a completely randomized design experiment. Cattle were fed bromegrass hay (13.6% CP) at maintenance level (11.70 kg DM d−1). Rumen contents were collected at intervals up to 120 h following administration of markers. Aliquots of rumen digesta solids and liquids were analyzed for Cr and Co concentration and Bacillus stearothermophilus colony-forming units (CFU) after overnight incubation on nutrient agar plates at 65 °C. Rates of passage were calculated as the regression coefficient of the natural logarithm of Cr, Co concentration or Bacillus stearothermophilus CFU in either solid or liquid fractions versus time. Data showed that liquid rate of passage from the rumen estimated by BSS (7.38% h−1) was lower (P

Bacillus stearothermophilus spores on strips. Calibration of thermoresistance kinetics to prior biological validation

Bacillus stearothermophilus spores on strips. Calibration of thermoresistance kinetics to prior biological validation

Bacillus stearothermophilus spores on strips. Calibration of thermoresistance kinetics to prior biological validation

Filter-paper strips saturated with Bacillus stearothermophilus spores were prepared and then stored for up to 1470 days. The strips were used to measures spore activation time and death kinetics in two systems: a serum bottle/oil bath combination, and glassine packages in a gravity autoclave. The data collected were analyzed primarily by analysis of variance and the interaction of spore storage time, processing temperature, inertial time and exposure time was determined.

Comparison of ion plasma, vaporized hydrogen peroxide, and 100% ethylene oxide sterilizers to the 12/88 ethylene oxide gas sterilizer.

The performance of a standard gas sterilizer, which uses a mixture of 12% ethylene oxide (EtO) and 88% chlorofluorocarbon as the sterilizing gas (12/88), was compared to selected gas, ion plasma, and vaporized hydrogen peroxide (H2O2) sterilizers that do not use chlorofluorocarbons. The effect of serum and salt on sterilizer performance was evaluated. Test carriers (porcelain and stainless steel penicylinders, or 125-cm lengths of plastic tubing [internal diameter of 3.2 mm]) were inoculated with Escherichia coli, Enterococcus faecalis, Pseudomonas aeruginosa, Mycobacterium chelonei, Bacillus stearothermophilus spores, Bacillus subtilis spores, and Bacillus circulans spores and then subjected to sterilization using 12/88, 100% EtO, ion plasma, or vaporized H2O2. The bacterial inoculum was prepared with and without 10% serum and 0.65% salt, and the residual bacterial load after sterilization as determined using viable counts. All of the sterilizers tested effected a six-log10 reduction of the bacterial inoculum on penicylinders, unless 10% serum and 0.65% salt were present, in which case the 100% EtO, vaporized H2O2, and ion plasma sterilizers were not as effective as the 12/88 sterilizer. None of the sterilizers could eradicate 10(6) CFU of all of the bacteria in 10% serum and 0.65% salt when inoculated inside a narrow lumen. The margin of safety for the 100% EtO, vaporized H2O2, and ion plasma sterilizers is less than that of the 12/88 sterilizer. The inability of all sterilizers, including the 12/88, to kill organisms in narrow lumens reliably when serum and salt were present raises concern about the current practice of gas sterilization of flexible endoscopes.

Influence of acidification and type of acidulant of the recovery medium on Bacillus stearothermophilus spore counts

Unheated and heated (1 min at 121°C) Bacillus stearothermophilus spores were grown in non-acidified (pH 7) and acidified recovery medium at different pH levels (6.7, 6.5, 6.2 and 5.9) using citric acid or glucono-δ-lactone (GDL) as acidulants. It was observed that the lower the pH, the lower the proportion of micro-organisms which recovered. The level of recovery was not the same for both acidulants, meaning that at the same pH level citric acid showed a greater inhibitory effect that glucono-δ-lactone. Heat treatment sensitized spores to pH effect. A linear relationship of the behaviour of spores with each acidulant is proposed.

Comparison of TDT and Arrhenius models for rate constant inactivation predictions of Bacillus stearothermophilus heated in mushroom-alginate substrate

Bacillus stearothermophilus spores were heated in a mixture of mushroom puree with alginate, in the temperature range 110–130°C. Both Arrhenius and the traditional Bigelow models were used to describe the dependence of the constant inactivation rate (K) or (D) with the temperature. Results showed that both are very good linear regression models, but a discrepancy between 20 and 45% was found in the constant inactivation rate predicted by both models at high temperatures (125–140°C). Despite this discrepancy, the Arrhenius model was a better predictor of the inactivation rate constants at temperatures of 125 and 130°C for B. stearothermophilus spores heated in an alginate-mushroom mixture.

Feasibility of a combined carrier test for disinfectants: studies with a mixture of five types of microorganisms

Background: There is mounting concern regarding the efficacy of many germicides on the market because officially recognized germicidal tests for various classes of microorganisms vary widely and often lack reproducibility and proper quantitation. We report here a carrier method for simultaneously and quantitatively assessing the efficacy of liquid chemical germicides against a mixture of microorganisms of varying degrees of resistance. Methods: In the test, each small glass cup (10 mm wide × 14 mm long) was contaminated with 10 μl of a standardized mixture of Staphylococcus aureus, Mycobacterium bovis bacille Calmette-Guérin, Trichophyton mentagrophytes spores, Sabin poliovirus type 1, and Bacillus stearothermophilus spores in 5% fetal bovine serum. The inoculum was dried for 60 minutes under ambient conditions and covered with 60 μl of the disinfectant under test or a balanced salt solution control for the desired contact time. The carrier was then placed in 2940 μl of an eluent and the eluates assayed separately for the five microorganisms. Tap water was used to dilute the test product as needed. Results: Of the 11 products tested, 2% alkaline glutaraldehyde, 0.6% sodium hypochlorite (about 5000 ppm free chlorine), and a 0.4% quarternary ammonium compound containing 23% hydrochloric acid were effective against all five challenge organisms. A hard-surface spray containing 0.1% o-phenylphenol with 79% ethanol was effective against all but bacterial spores; 70% (volume/volume) ethanol alone and povidone-iodine (1% available iodine) were effective against S. aureus, the mycobacterium, and the fungus; a 3% solution of peroxygen compounds was effective only against S. aureus and the poliovirus; 1.5% chlorhexidine gluconate, 0.06% quaternary ammonia compound, and 0.03% o-phenylphenol + 0.03% p-tertiary amylphenol could inactivate nothing but S. aureus; and 3% hydrogen peroxide was ineffective in all tests. Conclusions: This method shows promise for use with various classes of microorganisms, individually or as mixtures. Its application should enable the classification of germicides according to spectrum of activity.

Effects of steam sterilization on the contents of sharps containers

Background: One form of medical waste known to be capable of transmitting disease is the contaminated sharp. Safe handling and disposal of sharps is an essential element of any infection control program. Many areas allow the on-site treatment of sharps containers. However, little information currently exists as to the most effective sterilization procedures and container designs. Methods: This study was intended to evaluate the effect treatment with various autoclaves had on bacterial endospores present on strips or needled syringes. Strips contained 1.7 × 10 5 Bacillus stearothermophilus spores; syringes were soiled with equal numbers of spores or with spores plus blood. Syringes were tested capped and uncapped. A gravity-displacement autoclave and a high-vacuum autoclave were used. Strips and syringes were placed within sharps containers three quarters filled with representative materials. Six types of containers were tested. Containers were processed sitting up or on their sides. Processed strips and needles were aerobically cultured at 56° C for 7 days. If sterilization was not accomplished initially, additional exposure time was added. Results: (1) Soiled syringes were more difficult to sterilize than strips. (2) Capping or the presence of blood did not affect sterilization efficiency. (3) Container positioning was important only for the gravity-displacement autoclave. (4) Additional exposure time was required in the gravity displacement autoclave when sterilizing soiled syringes but not strips. (5) High-vacuum autoclaving killed all spore challenges within the normal processing interval. Conclusions: The data indicate that processing of sharps containers within a gravity-displacement autoclave appears to require extended exposure intervals to achieve sterilization.

Development and Evaluation of a Method to Determine Indicator Microorganisms in Air Emissions and Residue from Medical Waste Incinerators

To allow testing of microbial destruction in medical waste incinerators, methods were developed to determine indicator microorganisms (Bacillus Stearothermophilus spores) in incinerator air emissions and residue. The emission trapping train consisted of a water cooled glass probe and impingers containing a neutral phosphate buffer. In field tests, spores were injected directly into the probe, and results showed that approximately 60 percent of the spores were recovered. Spores were analyzed with adequate precision using a microbial membrane filter unit. Lab experiments indicated that spores were stable in neutral pH phosphate buffer for up to 20 days, and heat shocking samples (heating to 80 degrees C for 20 minutes) reduced spore numbers in acidic or basic buffer. Laboratory tests also showed that 60 to 70 percent of spores initially added to ash were recovered up to 22 days after addition of the spores. In addition, lab tests showed that spores can be effectively recovered from residue test pipes spiked with indicator spores.

Bacillus stearothermophilus Spore Recovery Altered by Media Concentration and Formulation

ABSTRACT Bacillus stearothermophilus spores, subjected to a range of heating times and temperatures, were recovered using dextrose tryptone agar and soybean casein digest agar, with and without additives, at normal and reduced concentrations. For very mild heat treatments, for all media tested, there was essentially no difference in number of spores recovered. For severely heat‐stressed B. stearothermophilus spores, reduction in the media manufacturer's recommended concentration to one‐tenth significantly increased recovery; the 0.1 concentration media produced a 2‐ to 60‐fold increase in numbers recovered. Recovery of heat‐stressed spores using the 0.1 concentration media increased with increasing heating time and temperature.

Effect of simultaneous application of heat and pressure on the survival of bacterial spores

The effect of simultaneous application of moderate hydrostatic pressure (10-300 atm) and heat on the survival of the Bacillus stearothermophilus spores in a flow-through system was investigated. A high heterogeneity of the sensitization of spores to heat by pressure was found. A higher degree of reduction of heat resistance was observed at the low than at the high temperatures tested. The simultaneous application of moderate pressure and heat can not be applied for the preservation of liquid foods due to the extreme heterogeneity of spore sensitization to heat by pressure.

Inhibition of Germination of Bacillus stearothermophilus Spores by Sucrose Monoalkylates and Other Surfactants.

In order to get additional information on antimicrobial action of sucrose monoalkylates, which are approved as food additives, we studied the effects of the esters on growth of heat-resistant Bacillus stearothermophilus spores, by comparison with those of a variety of surfactants differing in the chemical structure. Sucrose monoalkylates and several other surfactants inhibited the growth from spores, by preventing spore germination. The inhibitory effectiveness of surfactants is closely related to hydrophobicity of surfactants rather than their intrinsic chemical characteristics. Surfactants acted on spores in a bacteriostatic manner.

The evaluation of the recovery capacity of media for heat-treated Bacillus stearothermophilus spore strips

Six media were assessed for their capacity to recover spores of Bacillus stearothermophilus from three commercially available types of spore strip heated for up to 5 min at 121°C in steam. All media recovered similar numbers of spores from unheated strips; however, there was considerable difference in survivor counts when the media were used to recover heated spores. Media containing starch consistently recovered the highest number of spores. The greatest difference in recovery capacity between the media was observed when spore strips were heated for 5 min at 121°C.

Assessment of the Cleanability of Air-Actuated Butterfly Valves

Six common and commercially available 5.1-cm (2 in.) air-operated butterfly valves were fitted to a type 304 stainless steal manifold and circulation system. The system was microprocessor-controlled to simulate 3, 6 and 12 months of wear during typical processing and CIP procedures in a dairy-type application. Raw milk with added Bacillus stearothermophilus spores was diluted with water and was used as the circulation liquid. After a trial period, valves were carefully disassembled and tested microbiologically. Based on results a determination of cleanability was made. None of the valves proved to be totally cleanable without maintenance within 1 year of simulated operation. In fact, all but one valve failed within 6 months.

Influence of environmental storage relative humidity on biological indicator resistance, viability, and moisture content.

The effect of environmental storage relative humidity (RH) on the moisture content, viability, and moist heat and gaseous ethylene oxide (EO) resistance of biological indicators (BIs) was evaluated. No statistically significant difference was observed between the initial Bacillus stearothermophilus spore population and the spore population of BIs stored at 20 degrees C and 0, 20, 44, of 55% RH or under ambient, 4 degrees C, or -20 degrees C conditions after 12 months. A statistically significant decrease in moist heat resistance from initial starting levels was found for BIs stored at 20 degrees C and either 0 or 20% RH. There was a statistically significant decrease in the B. subtilis BI spore population, compared with initial levels, when the BIs were stored at 20 degrees C and 0% RH concomitant with a significant increase in their EO resistance. BI storage at 20 degrees C and 20 or 44% RH, or under ambient, 4 degrees C, or -20 degrees C conditions, had no significant effect on EO resistance. BIs stored at 20 degrees C and 66% RH demonstrated a significantly lower EO resistance compared with starting levels.