Surface-decontaminating action of glutaraldehyde in the gas-aerosol phase.

The surface disinfectant effect of glutaraldehyde in the gas-aerosol phase was investigated at different relative humidities and temperatures. At a gas-aerosol concentration of 15 to 20 mg/m3 and a relative humidity of about 80%, glutaraldehyde had a good disinfectant effect against both vegetative bacteria (decimal reduction time, less than 5 min) and bacterial spores (decimal reduction time, less than 45 min). In spite of its low volatility, glutaraldehyde was more effective than formaldehyde when the two substances were compared on an "added amount" basis.     

戊二醛复合消毒剂对猪病病毒杀灭效果的研究

目的　研究戊二醛复合消毒剂对猪病病毒的杀灭效果。方法　将猪细小病毒 (porcinepavrovirusvirus ,PPV)、猪繁殖呼吸综合征病毒 (porcinereproductiveandrespiratorysyndromevirus,PRRSV)和猪伪狂犬病病毒(porcinepseudorabiesvirus,PRV)分别与不同浓度的戊二醛复合消毒剂作用后 ,接种于长满细胞单层的细胞培养板中 ,根据细胞是否产生病变情况 ,确定消毒剂杀灭病毒的最佳浓度 ;同时 ,还将不同浓度的消毒剂与猪瘟病毒 (hogchloeravirus,HCV)作用后 ,对兔进行静脉注射 ,根据兔的体温变化情况 ,判断消毒剂杀灭病毒的最佳浓度。结果　1%浓度的消毒剂 ,可在 2 0min之内有效杀灭PPV、PRRSV和PRV ;0 5 %浓度的消毒剂 ,可在 10min之内有效杀灭HCV。结论　戊二醛复合消毒剂具有高效杀灭病毒的作用 ,适用于养殖场、医疗卫生行业及传染病流行地区的消毒灭菌 ;采用细胞感染法检测和评价消毒剂对病毒的杀灭效果是一种可行的体外试验方法     

A note on the temperature tolerance of Legionella

A strain of Legionella pneumophila serogroup 1 isolated from the environment had a decimal reduction time in water at 50 degrees C (D50) of 111 min, a D54 of 27 min and a D58 of 6 min. There was little loss of viability at 46 degrees C. Other environmental organisms, a Pseudomonas sp., a Micrococcus sp. and a coliform survived less well at these temperatures. A species of Sarcina had a survival time greater than the L. pneumophila at all the temperatures tested. Other strains of legionellas were tested at 50 degrees C and decimal reduction times calculated. These ranged from 80 min for another strain of L. pneumophia serogroup 1 to 216 min for L. bozemannii . Legionella micdadei did not survive well at 50 degrees C.     

Transport capacity, alkaline phosphatase activity and protein content of glutaraldehyde-treated cell forms of Escherichia coli.

Studies on the comparative transport capacity of various cell forms of Escherichia coli suggest that glutaraldehyde acts only in the outer regions of the cell envelope and to such an extent that transport of alpha-aminoisobutyric acid is reduced by 50%. Alkaline phosphatase activity in whole cells was severely impaired in the presence of alkaline glutaraldehyde and in NaCl-washed cells both acid and alkaline glutaraldehyde (0.01%) caused approximately 80-90% reduction in enzyme activity in 10 min. Protein content was reduced by only 10-15% with this concentration of glutaraldehyde, and cell volume decreased by the same extent. These results are discussed in terms of the mode of action of the disinfectant.     

A note on the temperature tolerance of Legionella

D ennis , P.J., G reen , D. & J ones , B.P.C. 1984. A note on the temperature tolerance of Legionella. Journal of Applied Bacteriology 56 , 349–350.
A strain of Legionella pneumophila serogroup 1 isolated from the environment had a decimal reduction time in water at 50C (D₅₀) of 111 min, a D₅₄ of 27 min and a D₅₈ of 6 min. There was little loss of viability at 46C. Other environmental organisms, a Pseudomonas sp., a Micrococcus sp. and a coliform survived less well at these temperatures. A species of Sarcina had a survival time greater than the L. pneumophila at all the temperatures tested. Other strains of legionellas were tested at 50C and decimal reduction times calculated. These ranged from 80 min for another strain of L. pneumophia serogroup 1 to 216 min for L. bozemannii. Legionella micdadei did not survive well at 50C.     

Death and injury of Staphytococcus aureus during thermal treatment of milk

Staphylococcus aureus isolated from milk and grown in milk was heated in milk. The phenomena of death as well as injury was investigated in the range of 50 to 75 degrees C. The D60 value (decimal reduction time on salt-free medium) was 0.87 min, the D'60 value (decimal reduction time in salt-containing medium) was 0.62 min. Cultures were injured as soon as heating started. This initial thermal shock increased with increasing temperature. At 50-60 degrees C injury was more rapid than death. At greater than 60 degrees C death became faster than injury and the two processes coincided at 70 degrees C. The Z value was 9.46 degrees C and the Z' value was 9.93 degrees C.     

Thermal inactivation and injury of Bacillus stearothermophilus spores

Aqueous spore suspensions of Bacillus stearothermophilus ATCC 12980 were heated at different temperatures for various time intervals in a resistometer, spread plated on antibiotic assay medium supplemented with 0.1% soluble starch without (AAMS) or with (AAMS-S) 0.9% NaCl, and incubated at 55 degrees C unless otherwise indicated. Uninjured spores formed colonies on AAMS and AAMS-S; injured spores formed colonies only on AAMS. Values of D, the decimal reduction time (time required at a given temperature for destruction of 90% of the cells), when survivors were recovered on AAMS were 62.04, 18.00, 8.00, 3.33, and 1.05 min at 112.8, 115.6, 118.3, 121.1, and 123.9 degrees C, respectively. Recovery on AAMS-S resulted in reduced decimal reduction time. The computed z value (the temperature change which will alter the D value by a factor of 10) for spores recovered on AAMS was 8.3 degrees C; for spores recovered on AAMS-S, it was 7.6 degrees C. The rates of inactivation and injury were similar. Injury (judged by salt sensitivity) was a linear function of the heating temperature. At a heating temperature of less than or equal to 118.3 degrees C, spore injury was indicated by the curvilinear portion of the survival curve (judged by salt sensitivity), showing that injury occurred early in the thermal treatment as well as during logarithmic inactivation (reduced decimal reduction time). Heat-injured spores showed an increased sensitivity not only to 0.9% NaCl but also to other postprocessing environmental factors such as incubation temperatures, a pH of 6.6 for the medium, and anaerobiosis during incubation.     

Thermal inactivation and injury of Bacillus stearothermophilus spores.

Aqueous spore suspensions of Bacillus stearothermophilus ATCC 12980 were heated at different temperatures for various time intervals in a resistometer, spread plated on antibiotic assay medium supplemented with 0.1% soluble starch without (AAMS) or with (AAMS-S) 0.9% NaCl, and incubated at 55 degrees C unless otherwise indicated. Uninjured spores formed colonies on AAMS and AAMS-S; injured spores formed colonies only on AAMS. Values of D, the decimal reduction time (time required at a given temperature for destruction of 90% of the cells), when survivors were recovered on AAMS were 62.04, 18.00, 8.00, 3.33, and 1.05 min at 112.8, 115.6, 118.3, 121.1, and 123.9 degrees C, respectively. Recovery on AAMS-S resulted in reduced decimal reduction time. The computed z value (the temperature change which will alter the D value by a factor of 10) for spores recovered on AAMS was 8.3 degrees C; for spores recovered on AAMS-S, it was 7.6 degrees C. The rates of inactivation and injury were similar. Injury (judged by salt sensitivity) was a linear function of the heating temperature. At a heating temperature of less than or equal to 118.3 degrees C, spore injury was indicated by the curvilinear portion of the survival curve (judged by salt sensitivity), showing that injury occurred early in the thermal treatment as well as during logarithmic inactivation (reduced decimal reduction time). Heat-injured spores showed an increased sensitivity not only to 0.9% NaCl but also to other postprocessing environmental factors such as incubation temperatures, a pH of 6.6 for the medium, and anaerobiosis during incubation.     

Evidence of temporal postdischarge decontamination of bacteria by gliding electric discharges: application to Hafnia alvei

This study aimed to characterize the bacterium-destroying properties of a gliding arc plasma device during electric discharges and also under temporal postdischarge conditions (i.e., when the discharge was switched off). This phenomenon was reported for the first time in the literature in the case of the plasma destruction of microorganisms. When cells of a model bacterium, Hafnia alvei, were exposed to electric discharges, followed or not followed by temporal postdischarges, the survival curves exhibited a shoulder and then log-linear decay. These destruction kinetics were modeled using GinaFiT, a freeware tool to assess microbial survival curves, and adjustment parameters were determined. The efficiency of postdischarge treatments was clearly affected by the discharge time (t*); both the shoulder length and the inactivation rate k(max) were linearly modified as a function of t*. Nevertheless, all conditions tested (t* ranging from 2 to 5 min) made it possible to achieve an abatement of at least 7 decimal logarithm units. Postdischarge treatment was also efficient against bacteria not subjected to direct discharge, and the disinfecting properties of "plasma-activated water" were dependent on the treatment time for the solution. Water treated with plasma for 2 min achieved a 3.7-decimal-logarithm-unit reduction in 20 min after application to cells, and abatement greater than 7 decimal logarithm units resulted from the same contact time with water activated with plasma for 10 min. These disinfecting properties were maintained during storage of activated water for 30 min. After that, they declined as the storage time increased.     

Thermal Resistance of Salmonellae and Staphylococci in Foods

The heat-resistant Salmonella senftenberg 775W and two strains of Staphylococcus aureus were tested at temperatures up to 68.3 C (71.1 C for S. senftenberg) in four different media. From the survival data, decimal reduction times (D values) were calculated for each set of conditions, and decimal reduction time curves were constructed for each bacterial strain in each medium. Slopes of decimal reduction time curves (Z(D)) ranged from 4.52 to 6.38 C with a single exception. There was no statistical heterogeneity among the remaining values. Results were in close agreement with published results of similar studies conducted at somewhat lower temperatures and support the practice of using a slope value (Z(D)) of 5.56 C for establishing time-temperature relationships for food processing. It is recommended that such a decimal reduction time curve not be extrapolated to temperatures more than 5.56 C higher than those actually tested.     

Dry-heat resistance of bacterial spores recovered from mariner-Mars 1969 spacecraft

The dry-heat resistances of 70 bacterial spore isolates recovered from Mariner-Mars 1969 spacecraft were determined and expressed as D values (decimal reduction times). Fifty per cent of the spore isolates had D values of 60 min or less at 125 C. Of organisms with D values greater than 60 min, four were selected for a study of the effect of sporulation medium and suspension menstruum on dry-heat resistance. Both sporulation medium and suspension menstruum were found to affect significantly the dry-heat resistance of the bacterial spores tested.     

Bacterial Resistance to Ultrasonic Waves under Pressure at Nonlethal (Manosonication) and Lethal (Manothermosonication) Temperatures

The decimal reduction times of Streptococcus faecium, Listeria monocytogenes, Salmonella enteritidis, and Aeromonas hydrophila corresponding to heat treatment at 62°C were 7.1, 0.34, 0.024, and 0.0096 min, and those corresponding to manosonication treatment (40°C, 200 kPa, 117 μm) were 4.0, 1.5, 0.86, and 0.90 min, respectively. The manosonication decimal reduction times of the four species investigated decreased sixfold when the amplitude was increased from 62 to 150 μm and fivefold when the relative pressure was raised from 0 to 400 kPa. In L. monocytogenes, S. enteritidis, and A. hydrophila, the lethal effect of manothermosonication was the result of the addition of the lethal effects of heat and manosonication, whereas in S. faecium it was a synergistic effect.     

Evaluation of a novel commercial quaternary ammonium compound for eradication of Mycobacteria,HCV and HBV in Egypt

Endoscopes are a common source of outbreaks of healthcare-associated infections. It is therefore important to identify high-level disinfectants capable of eliminating or killing all vegetative bacteria, mycobacteria, and viruses. Aldehydebased disinfectants are most commonly used in clinical practice but resistance has recently been detected and side effects associated with these disinfectants are well documented. In this study, we evaluated Virusolve+® EDS, a novel quaternary ammonium compound formulation supplied by Amity international, against Mycobacterium bovis (ATCC-27289), hepatitis C virus (HCV)-positive serum and hepatitis B surface antigen-positive serum. We also compared its efficacy against Cidex® (glutaraldehyde 2%), an aldehyde-based disinfectant. M. bovis showed no growth after 10 weeks with either Virusolve+® or Cidex®. Virusolve+® achieved a 10⁴- fold reduction in the initial 10⁶ HCV load under clean conditions (without red blood cells) for 20 min, whereas Cidex® achieved this reduction under clean and dirty conditions (without and with red blood cells, respectively) after both 10 and 20 min. Both Virusolve+® and Cidex® were able to eradicate hepatitis B virus (HBV) infectivity under clean conditions after 10 and 20 min, whereas under dirty conditions they were only able to eradicate virus infectivity after 20 min. Virusolve+® EDS when compared with Cidex® showed equal mycobactericidal activity completely eradicating M. bovis. However, both showed comparable virucidal activity against HBV, which was more effective under clean conditions, emphasizing the importance of the cleaning step in endoscope reprocessing. Cidex® was more effective at eradicating HCV under dirty conditions after a short contact time.     

The effect of age on the thermal resistance of arthroconidia from Chrysosporium inops

J. L. KINDERLERER. 1996. Food-borne members of the genus Chrysosporium have been isolated relatively infrequently. The heat resistance of arthroconidia of the xerophilic fungus, Chrysosporium inops Carmichael, was determined in 0.1% peptone at 66C. The survival curve was sigmoid in shape. The initial lag period was due to the chains of arthroconidia. Thermal inactivation occurred when one viable conidium was left per chain. The presence of chains of arthroconidia was confirmed with the cryo scanning electron microscope. The decimal reduction times were obtained from the regression line of the linear death phase for the heat-sensitive spores. The decimal reduction time (D₆₆) increased with increasing spore age. It was 1.67 min for 3-week-old spores, 1.95 min for 4-week-old spores and 5.49 min for 6-week-old spores. The older spores could recover from thermal death if they were given sufficient time. There was a significant increase in D₆₆ value for 6-week-old spores from 3.97 min to 5.49 when the counts were obtained after 14 d incubation (compared to counts after incubation for 10 d). This effect was not seen for the 3- and 4-week-old spores. There was a small population of heat-resistant spores. The initial population of arthroconidia was greater than log 7 cfu ml^-1. After heating for 1 h at 66C approximately log 2.2 cfu ml^-1 survived. These survivors represented approximately 0.001% of the original population.     

A suspension method to determine reuse life of chemical disinfectants during clinical use.

In-use testing of disinfectants is necessary to ensure efficacy over time. The current official procedure for testing disinfectants, the Association of Official Analytical Chemists (AOAC) use-dilution method, cannot be adapted to repeated sampling techniques of use-life testing. It is therefore necessary to use an alternative method when evaluating the activity of a disinfectant under actual use. The Clinical Research Associates (CRA) suspension method was developed to fill this need. It consists of adding 0.5 ml of a standard culture to 5.0 ml of test disinfectant and sampling the mixture after 10 min for surviving bacteria. When this test was compared with the AOAC use-dilution method under a simulated use situation, the two methods were generally equivalent in identifying disinfectant inactivation. In addition, the CRA method was less time consuming, easier to perform, and less variable than the AOAC method. Use of the CRA method in a clinical study demonstrated the need for reuse claims to be based on clinical use studies rather than on laboratory testing only.     

A suspension method to determine reuse life of chemical disinfectants during clinical use

In-use testing of disinfectants is necessary to ensure efficacy over time. The current official procedure for testing disinfectants, the Association of Official Analytical Chemists (AOAC) use-dilution method, cannot be adapted to repeated sampling techniques of use-life testing. It is therefore necessary to use an alternative method when evaluating the activity of a disinfectant under actual use. The Clinical Research Associates (CRA) suspension method was developed to fill this need. It consists of adding 0.5 ml of a standard culture to 5.0 ml of test disinfectant and sampling the mixture after 10 min for surviving bacteria. When this test was compared with the AOAC use-dilution method under a simulated use situation, the two methods were generally equivalent in identifying disinfectant inactivation. In addition, the CRA method was less time consuming, easier to perform, and less variable than the AOAC method. Use of the CRA method in a clinical study demonstrated the need for reuse claims to be based on clinical use studies rather than on laboratory testing only.     

Potential biological indicators for glutaraldehyde and formaldehyde sterilization processes

The present study aimed to isolate, select, and evaluate bacterial isolates with potential for use as biological indicators for sterilization with glutaraldehyde and/or formaldehyde. A total of 340 local Bacillus isolates were screened for glutaraldehyde and/or formaldehyde resistance by determination of minimum inhibitory concentrations (MICs), minimum bactericidal concentrations (MBCs), and extinction time and were compared with B. subtilis (var. niger) ATCC 9372, the biological indicator for ethylene oxide sterilization, as reference. Of these, 85 isolates had glutaraldehyde MICs of 0.5% or higher, while 29 had formaldehyde MICs of 0.04% or higher. Of the 29 resistant isolates, 15 had MBCs of 0.05% or more. Extinction times were used to evaluate the bactericidal/sporicidal activity of glutaraldehyde. Eight had inactivation times of more than 5 h in 2% glutaraldehyde (pH 8), whereas 12 had inactivation times of more than 3 h in l% formaldehyde, with one isolate in common. These 19 isolates were selected and evaluated as potential biological indicators for aldehydes by determination of the decimal reduction times (D values), compared with the reference strain. Eight glutaraldehyde-resistant isolates exhibited D values 2.0- to 3.5-fold higher than the reference strain (30 min.). Only five of 12 formaldehyde resistant isolates had D values higher than that of the reference strain. Using six resistant isolates, temperature coefficient values between 2.11 and 3.02 were obtained for 2% formaldehyde. Finally, 14 isolates were tested for potential pathogenicity and were identified to species level. All of the eight glutaraldehyde-resistant isolates, including the isolate with dual resistance, and three formaldehyde-resistant isolates were B. licheniformis, while two other formaldehyde-resistant isolates were B. cereus. Six of the selected B. licheniformis isolates are potential biological indicators for sterilization processes using aldehydes. Three can be suggested for glutaraldehyde only and three for both aldehydes. Electronic Publication     

Bactericidal activity of alkaline glutaraldehyde solution against a number of atypical mycobacterial species

The mycobactericidal activity of 2% alkaline glutaraldehyde solution was determined using standardized suspensions of 10 species of atypical mycobacteria and compared with that for virulent Mycobacterium tuberculosis. Suspensions of M. avium, M. intracellulare and M. gordonae were more resistant to disinfection by the glutaraldehyde than were virulent tubercle bacilli while M. kansasii, M. scrofulaceum and M. szulgae were somewhat more susceptible. Mycobacterium marinum, M. smegmatis and M. fortuitum were highly sensitive to the disinfectant action of the alkaline glutaraldehyde solution. This variation in sensitivity shown by apparently closely related strains of mycobacteria to this disinfectant has important practical implications.     

Moist-heat disinfection of pathogenic Acanthamoeba cysts

The effect of moist-heat in the disinfection of pathogenic Acanthamoeba cysts was investigated. Temperatures of 56°C or 60°C were not effective in killing cysts of A. polyphaga even after a contact time of 60 min, A 4 log reduction in viability was achieved within 15 min at 65°C and 2 min at 70°C giving decimal reduction rates (D-values) of 3·75 min and 30 s respectively. The ability of a commercial moist-heat contact lens disinfection unit to kill 1 times 10⁵ cysts of Acanthamoeba isolated from contact lens storage cases was also shown. Holding temperatures inside the cases of 65°C for 5·5 min and 70°C (the maximum temperature obtained) for 1 min were recorded during the disinfection cycle.     

Bactericidal activity of alkaline glutaraldehyde solution against a number of atypical mycobacterial species

The mycobactericidal activity of 2% alkaline glutaraldehyde solution was determined using standardized suspensions of 10 species of atypical mycobacteria and compared with that for virulent Mycobacterium tuberculosis. Suspensions of M. avium, M. intracellulare and M. gordonae were more resistant to disinfection by the glutaraldehyde than were virulent tubercle bacilli while M. kansasii, M. scrofulaceum and M. szulgae were somewhat more susceptible. Mycobacterium marinum, M. smegmatis and M. fortuitum were highly sensitive to the disinfectant action of the alkaline glutaraldehyde solution. This variation in sensitivity shown by apparently closely related strains of mycobacteria to this disinfectant has important practical implications.