Reactivation of Giardia lamblia cysts after exposure to polychromatic UV light

Aims: In this study, we determined the ability of a promising alternative UV technology – a polychromatic emission from a medium‐pressure UV (MP UV) technology – to inhibit the reactivation of UV‐irradiated Giardia lamblia cysts. Methods and Results: A UV‐collimated beam apparatus was used to expose shallow suspensions of purified G. lamblia cysts in PBS (pH 7·2) or filtered drinking water to a low dose (1 mJ cm^?2) of MP UV irradiation. After UV irradiation, samples were exposed to two repair conditions (light or dark) and two temperature conditions (25°C or 37°C for 2–4 h). The inactivation of G. lamblia cysts by MP UV was very extensive, and c. 3 log₁₀ inactivation was achieved with a dose of 1 mJ cm^?2. Meanwhile, there was no apparent reactivation (neither in vivo nor in vitro) of UV‐irradiated G. lamblia under the conditions tested. Conclusion: The results of this study indicated that, unlike the traditional low‐pressure (LP) UV technology, an alternative UV technology (MP UV) could inhibit the reactivation of UV‐irradiated G. lamblia cysts even when the cysts were exposed to low UV doses. Significance and Impact of the Study: It appears that alternative UV technology has some advantages over the traditional LP UV technology in drinking water disinfection because of their high level of inactivation against G. lamblia cysts and also effective inhibition of reactivation in UV‐irradiated G. lamblia cysts.     

Survival of Giardia lamblia trophozoites after exposure to UV light

The ability of Giardia lamblia trophozoites to reproduce after exposure to different fluences of UV radiation was determined using an in vitro-cultured method. The rate of parasite reproduction following UV exposure was measured by direct enumeration of trophozoites cultured in Diamond's Trypticase Yeast extract-Iron (TYI)-S-33 medium. The results suggested that some G. lamblia trophozoites may survive or are reactivated following exposure to UV fluences up to 10 mJ cm(-2). In addition, trophozoites exposed to a UV fluence of 1 mJ cm(-2) were infectious to Mongolian gerbils. Evidence of survival or reactivation at UV fluences of 20 and 40 mJ cm(-2) was ambiguous and statistically inconclusive, while at 100 mJ cm(-2) there was no evidence of survival or reactivation. This finding may have implications for criteria used by the drinking water and wastewater treatment industry to ensure safe reduction of G. lamblia cysts by UV disinfection processes.     

Interactions between humic matter and bacteria when disinfecting water with UV light

Aims:  To investigate the impact of aquatic humic matter on the inactivation of Escherichia coli and Bacillus subtilis by ultraviolet (UV) light.
Methods and Results:  A bench-scale study investigated the potential for Aldrich^® humic acid (AHA) and Suwannee River natural organic matter (SR-NOM) to coat the surface of E. coli and B. subtilis and offer protection from low-pressure UV light. UV doses of 5 and 14 mJ cm⁻² were applied using a collimated beam at four concentrations of humic matter (0, 10, 50 and 120 mg l⁻¹) in reagent grade water. Both AHA and SR-NOM were found to offer statistically significant protection of both E. coli and B. subtilis at concentrations of 50 and 120 mg l⁻¹ for a UV dose of 14 mJ cm⁻².
Conclusions:  Both E. coli and B. subtilis are susceptible to coating by humic matter which can reduce the sensitivity of the cells to UV light.
Significance and impact of the study:  Micro-organisms in the environment may acquire characteristics through interaction with humic matter that render them more resistant to UV disinfection than would be predicted based on laboratory inactivation studies using clean cells.     

Automated concentration and recovery of micro-organisms from drinking water using dead-end ultrafiltration

Aims:  Concentration of pathogens diluted in large volumes of water is necessary for their detection. An automated concentration system placed online in drinking water distribution systems would facilitate detection and mitigate the risk to public health.
Methods and Results:  A prototype concentrator based on dead-end hollow fibre ultrafiltration was used to concentrate Bacillus atrophaeus spores directly from tap water. Backflush was used to recover accumulated particulates for analysis. In field tests conducted on a water utility distribution system, 3·2 × 10⁴–1·4 × 10⁶ CFU ml⁻¹ (6·1 × 10⁶–3·0 × 10⁸ CFU) were recovered from the filter when 2·9 × 10⁷–1·0 × 10⁹ CFU were spiked into the system. Per cent recovery ranged from 21% to 68% for flow volumes of 15–21 l. Tests using spore influent levels <10 CFU l⁻¹ (spike < 1000 CFU) yielded 23–40% recovery for volumes >100 l.
Conclusions:  B. atrophaeus spores at levels <10 CFU l⁻¹ were concentrated directly from tap water using an automated dead-end hollow-fibre ultrafiltration system.
Significance and Impact of the Study:  The prototype concentrator represents a critical step towards an autonomous system that could be installed in drinking water distribution lines or other critical water lines to facilitate monitoring. Recovered samples can be analysed using standard or rapid biosensor methods.     

Inactivation of Mycobacterium avium ssp. paratuberculosis in milk by UV treatment

Aims:  To determine the effect of UV radiation on the viability of two strains of Mycobacterium avium ssp. paratuberculosis (Map) inoculated into milk.
Methods and Results:  Mycobacterium avium ssp. paratuberculosis in a ultra heat treated milk matrix was subjected to increasing doses of UV-C radiation from 0 to 1836 mJ ml⁻¹ using a pilot-scale UV reactor (20 l capacity). Survival of Map was monitored by culture on Herrold's egg yolk medium, Middlebrook 7H10 medium and the FASTPlaque TB™ phage assay. Differences in sensitivity to UV treatment were observed between strains, however, at 1000 mJ ml⁻¹ a Map kill rate of 0·1–0·6 log₁₀ was achieved regardless of strain used or method employed to enumerate Map. Although the inactivation trend was similar on the culture and phage assay, the former gave a consistently higher viable count.
Conclusions:  The use of UV radiation alone does not represent an alternative to current pasteurization regimes for a large reduction in viable Map in milk.
Significance and Impact of the Study:  To the authors' knowledge the work here represents the first pilot-scale UV treatment process used to assess UV efficacy to inactivate Map in milk. The results are similar to those obtained with a laboratory-scale process indicating the difficulties associated with UV treatment of an opaque liquid and the recalcitrance of Map towards inimical treatments.     

Influence of photoreactivating light intensity and incubation temperature on photoreactivation of Escherichia coli following LP and MP UV disinfection

Aims:  To investigate the effects of fluorescent light intensity, sunlight intensity and temperature on photoreactivation of Escherichia coli after low-pressure (LP) and medium-pressure (MP) ultraviolet (UV) disinfection.
Methods and Results:  Two E. coli strains were irradiated with LP and MP UV lamps, and exposed to various fluorescent light (0–23 kLux) and sunlight intensities (1–80 kLux), and temperatures (4–50°C). Escherichia coli concentrations were enumerated at hourly intervals to determine photoreactivation rates and final photoreactivation levels. Higher photoreactivation rates and levels were observed with increasing fluorescent light intensities, while high sunlight intensity (>12 kLux) caused a one-log decrease in E. coli concentrations. When exposed to near-optimum growth temperatures (23–37°C), photoreactivation levels were higher than those with too high (50°C) or too low (4°C) temperatures. Overall, photoreactivation following MP UV disinfection was lower than that following LP UV disinfection.
Conclusions:  Photoreactivation of bacteria following UV disinfection can be a problem in tropical countries where sunlight is abundant and temperatures are high, unless high sunlight intensity is present or if MP UV disinfection is employed.
Significance and Impact of the Study:  With the increased use of UV disinfection, it is imperative that photoreactivation be taken into account in the design of reactors based on site-specific conditions of temperature and light intensity exposure.     

Detection of infectious rotavirus in naturally contaminated source waters for drinking water production

Aims:  To assess chlorine susceptibility of Legionella pneumophila grown from two amoebic hosts, Acanthamoeba castellanii and Hartmannella vermiformis .
Methods and Results:  After being released from amoebae, Leg. pneumophila were chlorinated at 2 and 5 mg l⁻¹ for 5 min–24 h. Bacterial culturability and cytoplasmic membrane deterioration were quantified by culture assay on BCYEα agar and BacLight stains coupled with a fluorescent microscope, respectively. Chlorination reduced the culturability of Leg. pneumophila by 2·93–4·59 log CFU ml⁻¹ and damaged cellular membrane by 53·8–99·2%. Moreover, cells released from H. vermiformis exhibited significantly lower degrees in culturability reduction ( P  = 0·0008) and membrane deterioration ( P  < 0·0001) when compared with those from A. castellanii . The amoebic genus is the most significant parameter affecting cytoplasmic membrane integrity of chlorinated Legionella ( P  < 0·0001), followed by free chlorine concentration ( P  = 0·042).
Conclusions:  Legionella pneumophila replicated from H. vermiformis possess greater chlorine resistance than the cells from A. castellanii .
Significance and Impact of the Study:  This study shows the heterogeneity of amoebae-grown Leg. pneumophila in chlorine susceptibility, which should be considered in the control of legionellae proliferation, particularly in the systems where H. vermiformis is dominant, e.g. hot water plumbing.     

Lactic acid production by Lactobacillus delbrueckii in a dual reactor system using packed bed biofilm reactor

Aims:  An integrated dual reactor system for continuous production of lactic acid by Lactobacillus delbrueckii using biofilms developed on reticulated polyurethane foam (PUF) is demonstrated.
Methods and Results:  Lactobacillus delbrueckii was immobilized on PUF, packed in a bioreactor and used in lactic acid fermentation. The rate of lactic acid production was significantly high with a volumetric productivity of 5 g l⁻¹ h⁻¹ over extended period of time. When coupled to a bioreactor, the system could be operated as dual reactor for over 1000 h continuously without augmentation of inoculum and no compromise on productivity.
Conclusions:  Polyurethane foams offer an excellent support for biofilm formation.
Significance and Impact of the Study:  The system was very robust and could be operated for prolonged period at a volumetric productivity of 4–6 g l⁻¹ h⁻¹.     

The occurrence of aerolysin-positive Aeromonas spp. and their cytotoxicity in Norwegian water sources

Aims:  The aim of the study was to investigate the occurrence of Aeromonas spp. and their aerolysin status in Norwegian natural water sources.
Methods and Results:  Seventy-one samples from 33 Norwegian water sources were examined for the presence of Aeromonas spp. From most of the sample sites, the strains were isolated on blood-ampicillin-agar and Difco Aeromonas agar simultaneously. The majority of the samples (73/77) contained Aeromonas spp., with an average of 35–100 cfu 100 ml^–1. The highest counts were found in faecally-contaminated water. Using PCR, 445 isolates were screened for the presence of aerolysin, and 79% of them were found to be carriers of the aerolysin gene. A selection of the isolated strains was tested on Vero cell cultures and 83% of them showed cytotoxicity.
Conclusions:  There is widespread occurrence of aerolysin-positive cytotoxic Aeromonas spp. in many different Norwegian natural waters, including drinking water sources.
Significance and Impact of the Study:  The widespread occurrence of potentially-pathogenic Aeromonas spp. in the environment demands that these bacteria should not be ignored in drinking water supplies and in the food industry.     

Multidrug resistance gene deficient (mdr1a–/–) mice have an altered caecal microbiota that precedes the onset of intestinal inflammation

Aim:  To compare caecal microbiota from mdr1a ^–/– and wild type (FVB) mice to identify differences in the bacterial community that could influence the intestinal inflammation.
Methods and Results:  Caecal microbiota of mdr1a ^–/– and FVB mice were evaluated at 12 and 25 weeks of age using denaturing gradient gel electrophoresis (DGGE) and quantitative real-time PCR. DGGE fingerprints of FVB and mdr1a ^–/– mice (with no intestinal inflammation) at 12 weeks revealed differences in the presence of DNA fragments identified as Bacteroides fragilis , B. thetaiotaomicron , B. vulgatus and an uncultured alphaproteobacterium. Escherichia coli and Acinetobacter sp. were only identified in DGGE profiles of mdr1a ^–/– mice at 25 weeks (with severe intestinal inflammation), which also had a lower number of total bacteria in the caecum compared with FVB mice at same age.
Conclusions:  Differences found in the caecal microbiota of FVB and mdr1a ^–/– mice (12 weeks) suggest that the lack of Abcb1 transporters in intestinal cells due to the disruption of the mdr1a gene might lead to changes in the caecal microbiota. The altered microbiota along with the genetic defect could contribute to the development of intestinal inflammation in mdr1a ^–/– mice.
Significance and Impact of the Study:  Differences in caecal microbiota of mdr1a ^–/– and FVB mice (12 weeks) suggest genotype specific colonization. The results provide evidence that Abcb1 transporters may regulate host interactions with commensal bacteria. Future work is needed to identify the mechanisms involved in this possible cross-talk between the host intestinal cells and microbiota.     

Expression of mel gene improves the UV resistance of Bacillus thuringiensis

Aims:  To improve ultraviolet (UV) resistance of Bacillus thuringiensis for increasing the duration of the Bt product applied in the field, a genetically engineered strain Bt TD841 that produced both melanin and Cry1A protein was constructed, and its UV resistance was evaluated in the laboratory.
Methods and Results:  Melanin quantitative analysis revealed that the recombinant strain Bt TD841 could synthesize 0.15 mg melanin ml⁻¹ sporulated culture. Atomic force microscopy confirmed the production of diamond crystal and SDS-PAGE results showed the expression of the 130 kDa Cry1A protein. Bioassay results demonstrated that the LC₅₀ value of Bt TD841 was 3.69 μl ml⁻¹ against Helicoverpa armigera and the UV resistance of this recombinant was enhanced 9.7-fold compared to its parental strain Bt HC42 after 4-h UV irradiation.
Conclusion:  Expression of the mel gene can significantly increase UV resistance of B. thuringiensis.
Significance and Impact of the Study:  This is the first report on genetically engineered Bt strain with co-expression of melanin and the insecticidal crystal proteins gene, and the results may offer a practical solution for improving the photoprotection of Bt products in field application.     

Denitrification in river sediments: relationship between process rate and properties of water and sediment

1. A survey was made of denitrification and nitrous oxide (N₂O) production in river sediments at fifty sites in north‐east England during one season in order to investigate the relationship between rates and environmental factors likely to influence these processes. The sites were chosen to represent a wide range of physical and chemical conditions. Denitrification rate and N₂O production were measured within 5 h of sampling using the slurry acetylene blockage technique.
2. Denitrification rate ranged from less than 0.005–260 nmol N g^–1 DW h^–1, tending to increase in a downstream direction. N₂O production ranged from negative values (net consumption) to 13 nmol N₂O‐N g^–1 DW h^–1 and accounted for 0–115% of the N gases produced.
3. Denitrification rate and N₂O concentration in the sediment were correlated positively with nitrate concentration in the water column, water content of the sediment and percentage of fine (< 100 μm) particles in the sediment.
4. The variation in denitrification rate was satisfactorily explained (64% total variance) by a model employing measurements of water nitrate and water content of sediments. No simple or multiple relationship was found for N₂O production.     

Spatio-temporal variation in macroinvertebrate assemblages of glacial streams in the Swiss Alps

1. Changes in water chemistry, benthic organic matter (BOM), and macroinvertebrates were examined in four different glacial streams over an annual cycle. The streams experienced strong seasonal changes in water chemistry that reflected temporal changes in the influence from the source glacier, especially in water turbidity, particulate phosphorus and conductivity.
2. Nitrogen concentrations were high (nitrate-N values were 130–274 μg L^–1), especially during spring snowmelt runoff. Benthic organic matter attained >600 g m^–2 dry mass at certain times, peaks being associated with seasonal blooms of the alga Hydrurus foetidus .
3. Macroinvertebrate taxon richness was two to three times higher (also numbers and biomass) in winter than summer suggesting winter may be a more favourable period for these animals. Benthic densities averaged 1140–3820 ind. m^–2, although peaking as high as 9000 ind. m^–2. Average annual biomass ranged from 102 to 721 mg m^–2, and reached >2000 mg m^–2 at one site in autumn.
4. Taxa common to all sites included the dipterans Diamesa spp. and Rhypholophus sp., the plecopterans Leuctra spp. and Rhabdiopteryx alpina , and the ephemeropterans Baetis alpinus and Rhithrogena spp. Principal components analysis clearly separated winter assemblages from those found in summer.     

Control of Aspergillus section Flavi growth and aflatoxin accumulation by plant essential oils

Aims:  The antifungal effect of Pimpinella anisum (anise), Pëumus boldus (boldus), Mentha piperita (peppermint), Origanum vulgare (oregano) and Minthosthachys verticillata (peperina) essential oils against Aspergillus section Flavi (two isolates of Aspergillus parasiticus and two isolates of Aspergillus flavus ) was evaluated in maize meal extract agar at 0·982 and 0·955 water activities, at 25°C.
Methods and Results:  The percentage of germination, germ-tube elongation rate, growth rate and aflatoxin B₁ (AFB₁) accumulation at different essential oils concentrations were evaluated. Anise and boldus essential oils were the most inhibitory at 500 mg kg⁻¹ to all growth parameters of the fungus. These essential oils inhibited the percentage of germination, germ-tube elongation rate and fungal growth. AFB₁ accumulation was completely inhibited by anise, boldus and oregano essential oils. Peperina and peppermint essential oils inhibited AFB₁ production by 85–90% in all concentrations assayed.
Conclusions:  Anise and boldus essential oils could be considered as effective fungitoxicans for Aspergillus section flavi .
Significance and Impact of the Study:  Our results suggest that these phytochemical compounds could be used alone or in conjunction with other substances to control the presence of aflatoxigenic fungi in stored maize.     

Potential of Bacillus sp. to produce polyhydroxybutyrate from biowaste

Aim:  To test the Bacillus strains for their abilities to produce polyhydroxybutyrate (PHB) from different sugars and biowaste (Pea-shells).
Methods and Results:  Six Bacillus strains were checked for their ability to produce PHB from GM2 medium supplemented with different sugars at the rate of 1% (w/v) and from biowaste and GM2 (BW : M) combinations (3 : 7, 1 : 1, 7 : 3). Glucose supplemented GM2 medium resulted in maximum PHB production of 435 mg l⁻¹ constituting 31–62% w/w of the total cell dry mass. Substituting GM2 medium to the extent of 50% with biowaste (pea-shell slurry) resulted in 945–1205 mg l⁻¹ PHB (55–65% w/w). Optimization for additional nitrogen supplementation, inoculum size resulted in a final PHB production of 3010–3370 mg l⁻¹ equivalent to 300 g kg⁻¹ biowaste (dry wt).
Conclusion:  The Bacillus strains were able to produce PHB from biowaste (Pea-shells) as cheap source of substrate.
Significance and Impact of the Study:  This is the first report on usage of pea-shells as feed for PHB production, opening new possibilities for its use for production of PHB and Bacillus as potential candidate for the purpose.     

Anti-Helicobacter pylori activity of Lactobacillus delbrueckii subsp. bulgaricus strains: preliminary report

Aims:  To evaluate the activities of six Lactobacillus delbrueckii subsp. bulgaricus (LB) strains against 30 Helicobacter pylori strains by agar-well diffusion method.
Methods and Results:  LB cultures [4 × 10⁸–4 × 10⁹ CFU ml⁻¹) either were prepared in milk at their native pH, 3·8–5·0, or were adjusted to pH 6·4–7·7. At low and neutralized pH, LB strains inhibited the growth by 40–86·7% and 16·7–66·7% of H. pylori strains, respectively. LB activity was strain-dependent. At low and neutralized pH, one and five H. pylori strains, respectively, were not inhibited by any LB strain. LB2 and LB3, taken together, were active against most metronidazole and clarithromycin resistant strains.
Conclusions:  All LB strains inhibited a number of H. pylori strains, including also antibiotic resistant strains. LB activity was strain-dependent and better at low pH. At low pH values, the most active LB strains were LB1, LB2 and LB3, inhibiting 86·7% of H. pylori strains, while at neutralized pH values, the most active LB strains were LB2 and LB3, inhibiting 53·3 and 66·7% of H. pylori strains, respectively.
Significance and Impact of the Study:  LB could be utilized in the treatment or prophylaxis of H. pylori infection and warrants clinical investigations.     

Novel approach to control Salmonella enterica by modern biophotonic technology: photosensitization

Aims:  Salmonellosis is one of the most common foodborne diseases in the world. The aim of this study was to evaluate the antibacterial efficiency of 5-aminolevulinic acid (ALA) based photosensitization against one of food pathogens Salmonella enterica .
Methods and Results:  Salmonella enterica was incubated with ALA (7·5 mmol l⁻¹) for 1–4 h and afterwards illuminated with visible light. The light source used for illumination of S. enterica emitted light λ  = 400 nm with energy density 20 mW cm⁻². The illumination time varied from 0 to 20 min and subsequently a total energy dose reached 0–24 J cm⁻². The data obtained indicate that S. enterica is able to produce endogenous photosensitizer PpIX when incubated with ALA. Remarkable inactivation of micro-organisms can be achieved (6 log) after photosensitization. It is obvious that photosensitization-based inactivation of S. enterica depends on illumination as well as incubation with ALA time.
Conclusion:  ALA-based photosensitization can be an effective tool against multi-drug resistant Gram-negative bacteria S. enterica serovar Typhimurium.
Significance and Impact of the Study:  Experimental data and mathematical evaluations support the idea that ALA-based photosensitization can be a useful tool for the development of nonthermal food preservation technology in future.     

Long-term effects of successive Ca(OH)2 and CaCO3 treatments on the water quality of two eutrophic hardwater lakes

1. Whole-lake experiments were conducted in two hardwater lakes (Halfmoon and Figure Eight) in Alberta, Canada, to investigate the effectiveness of repeated lime (slaked lime: Ca(OH)₂ and/or calcite: CaCO₃) treatments (5–78 mg L^–1) for up to 7 years.
2. Randomized intervention analysis of intersystem differences between the experimental and three reference lakes demonstrated a decline in euphotic total phosphorus and chlorophyll a concentrations in the experimental lakes after repeated lime treatments.
3. After the second lime application to Halfmoon Lake, mean winter total phosphorus release rates (TPRR) decreased to < 1 mg m^–2 day^–1 compared with 3.6 mg m^–2 day^–1 during the winter after initial treatment. In the final year of lime application, mean summer TPRR decreased to 4.5 mg m^–2 day^–1 compared with 7.6 mg m^–2 day^–1 in the pre-treatment year.
4. Mean macrophyte biomass declined and species composition was altered at 1 and 2 m depths in Figure Eight Lake during lime application. Over the first 6 years of treatment, macrophyte biomass at 2 m declined by 95% compared with concentrations recorded during the initial treatment year. In the last year of the study, macrophyte biomass at 2 m reached initial treatment concentrations, which coincided with the greatest water transparency. Over the treatment period, macrophyte species shifted from floating to rooted plants.
5. Multiple lime applications can improve water quality in eutrophic hardwater lakes for periods of up to 7 years.     

Combination of ARAD microfibre filtration and LAMP methodology for simple, rapid and cost-effective detection of human pathogenic Giardia duodenalis and Cryptosporidium spp. in drinking water

Aims:  In this study, we report a new, simple methodology for the monitoring of Cryptosporidium oocysts and Giardia cysts in drinking water samples, ranging from 10- to 1000-l, which combines a new ARAD microfibre filtration of the (oo)cysts from drinking water and loop-mediated isothermal amplification (LAMP) of a human pathogenic Cryptosporidium parvum , Cryptosporidium hominis , Cryptosporidium meleagridis and Giardia duodenalis Assemblage A and B specific DNA sequence.
Methods and Results:  During the evaluation of the new concentration and detection technique, spiked reagent and matrix water samples plus blank samples were filtered and tested. In total, 27 samples have been investigated. The results clearly demonstrate that the methodology of using a new ARAD filter, which passed through 1000 l of drinking water with high turbidity (2 NTU), and followed by the LAMP assay was able to detect at least one (oo)cyst in 10 l of drinking water based on a 1000-l sample, taken over a 24-h period.
Conclusions:  The described protozoa detection methodology is sensitive, rapid and cost-effective.
Significance and Impact of the Study:  This effective procedure will be useful for small waterworks to achieve continuous monitoring and is also of value for screening catchments to identify those that require further treatment and more detailed microscopic counts.     

Protective effect of salicylates against hydrogen peroxide stress in yeast

Aims:  To investigate the effects of salicylates in Saccharomyces cerevisiae exposed to oxidative stress induced by hydrogen peroxide (H₂O₂).
Methods and Results:  Saccharomyces cerevisiae was cultured through to the postlogarithmic phase of growth. Stress was induced by the addition of 1·5 mmol l⁻¹ H₂O₂ for 1 h, while N-acetyl-l-cysteine (NAC) and glutathione (GSSG) were used as control agents that affect the redox balance. Sodium salicylate, at 0·01–10 mmol l⁻¹or acetylsalicylic acid, at 0·02–2·5 mmol l⁻¹ was administered at various times before hydrogen peroxide stress. Both agents conferred resistance to a subsequent hydrogen peroxide stress, similarly to the induction of the adaptive response observed upon pretreatment with NAC and GSSG. Sodium salicylate was more potent as a short-term, but not as a long-term pretreatment agent, compared to acetylsalicylic acid.
Conclusions:  Pharmacological pretreatment with salicylates resulted in dose related increases in cell survival, indicating the induction of the protective response in yeast.
Significance and Impact of the study:  The possible role of salicylates in the modulation of the hydrogen peroxide stress response in eukaryotic cells address questions on the effects of these commonly used therapeutic agents in a number of disorders exhibiting an oxidative stress component.