The fungicidal efficacy of various commercial disinfectants used in the food industry

The antifungal effects of eight commercial disinfectants namely alcohol, peracetic acid, iodophors, aldehydes, quaternary amine compounds (QAC, a, b and c), and a chlorine-based agent were assessed at different concentrations. The time taken for these disinfectants to kill different microorganisms was used to assess their efficacy. The microorganisms tested were six yeasts,Saccharomyces cerevisiae, Saccharomyces uvarum, Kloeckera apiculata, Candida oleophila, Metschnikowia fructicola, Schizosaccharomyces pombe, and two moulds,Aspergillus niger (5 strains) andPenicillium roqueforti (5 strains). The disinfectants QAC (a) and QAC (c) were the most effective against all the microorganisms tested. The chlorine-based disinfectant worked most efficiently against the moulds at all concentrations used (0.5, 1.0, 1.5 and 2.0%). Peracetic acid and alcohol based disinfectants were most effective against the yeasts than mould. Tested yeasts were more resistant to the aldehyde and iodophors base disinfectants than the others.     

Efficacy of a variety of disinfectants against Listeria spp.

The efficacy of 14 disinfectants against Listeria innocua and two strains of Listeria monocytogenes in the presence of organic matter was studied. Quantitative efficacy tests were used. Many of the disinfectants tested were not as effective on Listeria spp. when the test organisms were dried onto the surface of steel disks (carrier tests) as they were when the organisms were placed in suspension (suspension test). The presence of whole serum and milk (2% fat) further reduced the disinfectant capacities of most of the formulations studied. Only three disinfectants (povidone-iodine, chlorhexidine gluconate, and glutaraldehyde) were effective in the carrier test in the presence of serum; however, all three were ineffective when challenged with milk (2% fat). Only one solution, sodium dichloroisocyanurate, was effective in the presence of milk. All but four formulations (chloramine-T, phosphoric acid, an iodophor, and formaldehyde) were effective in the suspension tests, regardless of the organic load. L. monocytogenes was observed to be slightly more resistant to disinfection than L. innocua was. There was no difference in disinfectant susceptibility between the two strains of L. monocytogenes. These findings emphasize the need for caution in selecting an appropriate disinfectant for use on contaminated surfaces, particularly in the presence of organic material.     

Efficacy of a variety of disinfectants against Listeria spp

The efficacy of 14 disinfectants against Listeria innocua and two strains of Listeria monocytogenes in the presence of organic matter was studied. Quantitative efficacy tests were used. Many of the disinfectants tested were not as effective on Listeria spp. when the test organisms were dried onto the surface of steel disks (carrier tests) as they were when the organisms were placed in suspension (suspension test). The presence of whole serum and milk (2% fat) further reduced the disinfectant capacities of most of the formulations studied. Only three disinfectants (povidone-iodine, chlorhexidine gluconate, and glutaraldehyde) were effective in the carrier test in the presence of serum; however, all three were ineffective when challenged with milk (2% fat). Only one solution, sodium dichloroisocyanurate, was effective in the presence of milk. All but four formulations (chloramine-T, phosphoric acid, an iodophor, and formaldehyde) were effective in the suspension tests, regardless of the organic load. L. monocytogenes was observed to be slightly more resistant to disinfection than L. innocua was. There was no difference in disinfectant susceptibility between the two strains of L. monocytogenes. These findings emphasize the need for caution in selecting an appropriate disinfectant for use on contaminated surfaces, particularly in the presence of organic material.     

Use-Dilution Test and Newcastle Disease Virus

The use-dilution test for evaluating the effectiveness of disinfectants against bacteria was modified to determine the effectiveness of disinfectants against a group of viruses. Modifications were kept to a minimum to retain the general principles of the test and thereby retain the test's familiarity among testing laboratory personnel. Modifications included the use of a standard allantoic fluid suspension of Newcastle disease virus instead of a standard bacterial culture. The only other modification was the inoculation of six embryonated chicken eggs (10 to 12 days old) with 0.1 ml of nutrient broth into which a carrier ring was transferred after a standard period in diluted disinfectant. The death or survival of 60 embryos, then, is the criterion by which a disinfectant can be judged effective at use-dilution. Experiments are described which establish the validity of the modified test procedure. The effectiveness of nine common disinfectants against Newcastle disease virus as judged by this test procedure is reported.     

Comparative testing and evaluation of hard-surface disinfectants

Summary The activity of eleven disinfectants againstStaphylococcus aureus, Pseudomonas aeruginosa, andSaccharomyces cerevisiae was determined using a method based on the A.O.A.C. germicidal and detergent sanitizer assay. Based on the activity against the test organisms after 30-and 60-s exposures to each disinfectant, the disinfectant containing chlorine dioxide had the highest biocidal activity in this assay, on a mg/l basis. In addition, a disinfectant containing sodium hypochlorite and a disinfectant containing sodium chlorite performed well, at concentrations below label specifications. The results illustrate the importance of testing disinfectants in the context of their intended use.     

The role of anaerobic bacteria in chronic suppurative otitis media in children: Implications for medical therapy

This review describes the microbiology, diagnosis and medical management of chronic suppurative otitis media (CSOM) in children highlighting the role of anaerobic bacteria. In studies that employed adequate method for recovery of anaerobic bacteria polymicrobial aerobic and anaerobic flora was isolated from over half of the children with CSOM. The predominant aerobic isolates were Staphylococcus aureus and Pseudomonas aeruginosa and the most frequently isolated anaerobic organisms were Peptostreptococcus, Fusobacterium spp. and pigmented Prevotella and Porphyromonas spp. Several studies illustrated the efficacy of anti-infective agents effective against anaerobic bacteria in the treatment of CSOM. The medical therapy of CSOM should be directed at the eradication of the pathogenic aerobic and anaerobic organisms.     

Wide variation in effectiveness of laboratory disinfectants against bacteriophages

Aims: The purpose of this study was to identify an effective disinfectant for the inactivation of the bacteriophages (phages) being used in our laboratory, as published studies on phage inactivation are far from unanimous in their conclusions. Methods and Results: The phages studied were three closely related strains of Myoviridae and three strains of Siphoviridae. Three disinfectants which are used commonly in microbiology laboratories were evaluated: Virkon (1%), ethanol (75%) and sodium hypochlorite (2500 ppm available chlorine). The most effective of these was Virkon, which inactivated all six phages rapidly. Ethanol was effective against the Myoviridae but had little effect on the Siphoviridae. Sodium hypochlorite was the least effective of the disinfectants evaluated. Conclusions: The findings of this study demonstrate a wide diversity in the effectiveness of disinfectants tested for inactivation of phages. Significance and Impact of the Study: Of the disinfectants tested Virkon is the most suitable choice for those unable to carry out disinfection validation studies, or where a broad spectrum disinfectant against phages is required. All of the phages in this study showed resilience to inactivation by sodium hypochlorite, and therefore this disinfectant is an unwise choice for use against phage without first assessing its effectiveness.     

Exploring antifungal activities of acetone extract of selected Indian medicinal plants against human dermal fungal pathogens

A broad spectrum of medicinal plants was used as traditional remedies for various infectious diseases. Fungal infectious diseases have a significant impact on public health. Fungi cause more prevalent infections in immunocompromised individuals mainly patients undergoing transplantation related therapies, and malignant cancer treatments. The present study aimed to investigate the in vitro antifungal effects of the traditional medicinal plants used in India against the fungal pathogens associated with dermal infections. Indian medicinal plants (Acalypha indica, Lawsonia inermis Allium sativum and Citrus limon) extract (acetone/crude) were tested for their antifungal effects against five fungal species isolated from skin scrapings of fungal infected patients were identified as including Alternaria spp., Curvularia spp., Fusarium spp., Trichophyton spp. and Geotrichum spp. using well diffusion test and the broth micro dilution method. All plant extracts have shown to have antifungal efficacy against dermal pathogens. Particularly, Allium sativum extract revealed a strong antifungal effect against all fungal isolates with the minimum fungicidal concentration (MFC) of 50–100 μg/mL. Strong antifungal activity against Curvularia spp., Trichophyton spp., and Geotrichum spp. was also observed for the extracts of Acalypha indica, and Lawsonia inermis with MFCs of 50–800 μg/mL respectively. The extracts of Citrus limon showed an effective antifungal activity against most of the fungal strains tested with the MFCs of 50–800 μg/mL. Our research demonstrated the strong evidence of conventional plants extracts against clinical fungal pathogens with the most promising option of employing natural-drugs for the treatment of skin infections. Furthermore, in-depth analysis of identifying the compounds responsible for the antifungal activity that could offer alternatives way to develop new natural antifungal therapeutics for combating resistant recurrent infections.     

Antibiotic and Disinfectant Resistance in Tap Water Strains – Insight into the Resistance of Environmental Bacteria

Although antibiotic-resistant bacteria (ARB) have been isolated from tap water worldwide, the knowledge of their resistance patterns is still scarce. Both horizontal and vertical gene transfer has been suggested to contribute to the resistance spread among tap water bacteria. In this study, ARB were isolated from finished water collected at two independent water treatment plants (WTPs) and tap water collected at several point-of-use taps during summer and winter sampling campaigns. A total of 24 strains were identified to genus or species level and subjected to antibiotic and disinfectant susceptibility testing. The investigated tap water ARB belonged to phyla Proteobacteria, Bacteroidetes, Actinobacteria, and Firmicutes. The majority of the isolates proved multidrug resistant and resistant to chemical disinfectant. Neither seasonal nor WTP-dependent variabilities in antibiotic or disinfectant resistance were found. Antibiotics most effective against the investigated isolates included imipenem, tetracyclines, erythromycin, and least effective – aztreonam, cefotaxime, amoxicillin, and ceftazidime. The most resistant strains originate from Afipia sp. and Methylobacterium sp. Comparing resistance patterns of isolated tap water ARB with literature reports concerning the same genera or species confirms intra-genus or even intra-specific variabilities of environmental bacteria. Neither species-specific nor acquired resistance can be excluded.     

Antimicrobial activity of disinfectant agents incorporated into type IV dental stone

doi: 10.1111/j.1741‐2358.2011.00462.x
Antimicrobial activity of disinfectant agents incorporated into type IV dental stone Purpose: This study evaluated the antimicrobial activity of two disinfectant agents, 2% chlorhexidine digluconate solution (CHX) and 98% chlorhexidine hydrochloride powder (HYD), incorporated into type IV dental stone at the time of mixing. Material and methods: Agar diffusion test was used for the following microorganisms: Escherichia coli, Staphylococcus aureus, Bacillus subtilis and Candida albicans. The specimens were grouped in: (1) dental stone mixed with sterile distilled water; (2) paper disc soaked with CHX; (3) dental stone mixed with CHX; and (4) dental stone with incorporation of HYD, in 1% proportion of the dental stone mass and mixed with sterile distilled water. The culture medium was inoculated with microbial suspensions 1 and 24 h after pouring of the dental stone. The antimicrobial activity was evaluated by the average diameter of microbial growth inhibition zones. The data were analysed with a nested anova (p < 0.05) and Tukey test for specific comparisons. Results: The disinfectant agents demonstrated antimicrobial activity against all microorganisms, with the exception of C. albicans, against which the CHX was ineffective in two periods of analysis. Significant differences between disinfectants were found with all microorganisms. Conclusion: The disinfectant agents analysed were effective against most of the microorganisms tested, except C. albicans.     

Fluorescent assay based on resazurin for detection of activity of disinfectants against bacterial biofilm

A new, quick method, using the resazurin dye test as a bacterial respiration indicator, has been developed to assay the antibacterial activity of various substances used as disinfectants against bacterial biofilm growth on clinical devices. Resazurin was used to measure the presence of active biofilm bacteria, after adding disinfectant, in relation to a standard curve generated from inocula in suspension of the same organism used to grow the biofilm. The biofilm was quantified indirectly by measuring the fluorescent, water-soluble resorufin product produced when resazurin is reduced by reactions associated with respiration. Four products used as disinfectants and the biofilm growth of five bacterial species on carriers made of materials commonly found in clinical devices were studied. Under test conditions, chlorhexidine, NaOCl, ethanol, and Perasafe at concentrations of 0.2, 0.01, 350, and 0.16 mg/ml, respectively, all produced 5-log reductions in biofilm cell numbers on the three different carriers. The redox-driven test depends on bacterial catabolism, for which reason resazurin reduction produces an analytic signal of the bacterial activity in whole cells, and therefore could be used for determining disinfectant efficacy in an assay based on the metabolic activity of microorganisms grown as biofilm or in suspension.     

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.     

A rapid method for assessing the suitability of quenching agents for individual biocides as well as combinations

AIMS: To develop a novel, rapid method for testing the ability of quenching agents to neutralize disinfectants. METHODS AND RESULTS: Tests were performed to determine the suitability of different neutralizers for a range of disinfectants, using a new method based on the Bioscreen optical density analyser. Results showed that during disinfection tests, efficacy could be over-estimated due to poor, or no, neutralization of the disinfectant after a specified time of exposure to the bacteria. The failure to distinguish adequately between bacteriostatic and bactericidal effects can lead to false results during disinfectant testing. Experiments also showed that dilution of the disinfectant, following exposure to the bacteria, was not always sufficient to stop the activity of the disinfectant for chemicals with low dilution coefficients. CONCLUSIONS: The quench test proved to be very quick and easy to perform, with results being available within 18 h. Using the Bioscreen, the test is automated and determines whether dilution into a particular neutralizer is able to inactivate a disinfectant within 30 s. SIGNIFICANCE AND IMPACT OF THE STUDY: This new approach allows the efficacy of quenching agents to be determined, prior to undertaking each disinfection study, and can help in the development of more suitable quenching solutions. The test has also been used to find suitable neutralizers for mixtures of disinfectants which might be used during studies on synergistic biocide combinations.     

Antifungal Activity of Geldanamycin Alone or in Combination with Fluconazole Against Candida species

A standardized broth microdilution method was used to test the antifungal activity of geldanamycin (GA), an inhibitor of heat shock protein 90 (Hsp90), alone or in combination with the antifungal agent fluconazole (FLC) against 32 clinical isolates of Candida spp. In addition, a disk diffusion test was also used to evaluate the antifungal effect of these two drugs against Candida spp. by measuring the inhibition zone diameters. We found that the range of minimal inhibitory concentrations (MICs) for GA alone against Candida spp. was 3.2–12.8 mg/L and the geometric mean of MICs was 6.54 mg/L. In addition, the combination of GA with FLC showed synergistic effects in vitro against 2 FLC-susceptible and 6 FLC-resistant isolates of C. albicans. As for the other isolates, indifference but no antagonism was observed. In the disk diffusion assay, the diameter of inhibition zones for FLC combined with GA against FLC-resistant C. albicans isolates was 30 mm, while no inhibition was observed with FLC alone. These results demonstrate that GA possesses antifungal activity against Candida spp., and the combination of GA with FLC shows in vitro synergistic activity against some C. albicans isolates, especially those resistant to FLC.     

Preliminary characterization of some Streptomyces species isolated from a composting process and their antimicrobial potential

The aim of this study was to screen Streptomycetes isolates with antimicrobial and antiviral activity, in a search for new metabolites. The isolates were obtained from a composting process, and identified based on morphological characteristics and molecular biological methods. The antimicrobial activity was determined using the double-layer agar method against 53 test organisms (bacteria, yeasts, and filamentous fungi). All isolates were grown in submerged culture, in mineral salts-starch-casein (SC) broth and ISP2 media, and the filtrate cultures were used in the assays for antibacterial and antiviral activity. Bovine Herpes virus (BoHV-I) was used for the antiviral activity. The morphological and molecular characteristics confirmed that all 25 isolates belonged to the genus Streptomyces. In the assay for antimicrobial activity, 80% of the Streptomyces isolates were able to inhibit at least one of the test organisms. Of these, 80% were active against bacteria and 45% against fungi. Eight of the isolates showed a broad spectrum of inhibitory activity; of these, the isolate Streptomyces spp. 1S was able to inhibit 46 of the test organisms, and, most importantly, the 16 Gram-negative strains were inhibited. Of the 25 isolates, 44.4% of the isolates were able to grow and produce bioactive metabolites when grown in submerged culture. Four extracts showed a cytopathic effect in 10 CCID₅₀ MDBK cell, even though no viricidal effect was observed. The results obtained with these isolates indicated good biotechnological potential of these Streptomyces strains.     

Assessment of the efficacy of disinfectants on surfaces

The Literature on testing the efficacy of disinfectants covers a century. Most predominant and standardized are the so called suspension tests that allow for the quantitative estimation of the microbicidal activity (log reduction factors) of disinfectants on test organisms suspended in solutions of these products.Since the outcome of suspension tests might be a poor predictor for the efficacy of a disinfectant under practical circumstances, especially with regard to bacteria attached to surfaces, a variety of test procedures have been designed to mimic those conditions. Within the framework of CEN/TC 216 a quantitative surface test has been developed to assess the activity of disinfectants on bacteria or fungi attached to steenless steel surfaces. Preliminary data suggest that covering a dried inoculum with disinfectant without any further mechanical action to improve contact between organisms and disinfectant, will usually result in lower reduction factors than those obtained with suspension tests. Comparative testing further suggests that by applying mechanical action, with the effect of resuspending cells in the liquid on the surface,—similar to mopping, brushing etc.— will result in higher reduction rates. Although not unexpected these findings emphasize the importance of designing test methods based on practical applications of disinfectants.     

Evaluation of efficacy of disinfectants against Salmonella from the feed industry

Aims:  To evaluate disinfectants against Salmonella under conditions relevant for the feed industry.
Materials and Results:  A survey on the use of disinfectants in feed industry showed that a range of different types was used. Nine disinfectants, reflecting the most commonly used active ingredients, were tested for bactericidal activity on Salmonella isolated from the feed industry. All disinfectants were efficient against Salmonella in suspension. The bactericidal effect varied considerably between different types of active compounds on bacteria dried on surfaces or grown as biofilm. Tenside-based disinfectants and hypochlorite were found to have low bactericidal activity and the efficiency was significantly reduced when the ratio of amount disinfectant per cell decreased. It was shown that concentrations of 70–80% ethanol were effective against Salmonella. Among the disinfectants tested a product containing 70% ethanol was most efficient followed by Virkon S.
Conclusions:  Many disinfectants had low bactericidal activity against Salmonella at surfaces while Virkon S and a product containing 70% ethanol were most effective. Another advantage of ethanol-based disinfectants is evaporation of ethanol, resulting in low residual water after use.
Significance and Impact of the Study:  Use of the disinfectants found to be efficient against surface associated Salmonella , may assist the industry in combating Salmonella .     

Evaluation of Disinfectants for Hospital Housekeeping Use

A use-dilution procedure and screening method are proposed to aid the hospital bacteriologist in selecting the most effective disinfectants. Sixteen disinfectants were tested with and without organic material on six different organisms. Sporadic results usually obtained with quaternaries tested by the procedure of the Association of Official Agricultural Chemists (AOAC) were eliminated by the methods of this study. The use-dilution procedure employs the material upon which the disinfectant is to be used, rather than stainless steel, as in the AOAC use-dilution test. The importance of testing each disinfectant against several organisms and in the presence of organic material is discussed.     

Effect of Different Heat Treatments and Disinfectants on the Survival of <Emphasis Type="Italic">Prototheca zopfii</Emphasis>

Bovine mastitis caused by the yeast-like alga Prototheca zopfii represents a serious veterinary problem and may result in heavy economic losses to particular dairy farms. The purpose of this study was to evaluate the survival of 50 isolates of P. zopfii in milk subjected to different heat treatments and the survival of further 106 P. zopfii isolates after exposure to three classes of teat disinfectants: iodine (Dipal), quaternary ammonium compounds (Teat), and dodecylbenzenesulphonic acid (Blu-gard). Of the 50 isolates tested for thermal tolerance, 29 (58%) survived heat treatment at 62°C for 30 s and 13 (26% of all isolates) of those survived after heat treatment at 72°C for 15 s. None of the 106 isolates were able to withstand the in-use concentrations of the three disinfectants tested. The highest disinfectant concentrations that permitted survival of at least one isolate were dilutions: 1:1,000 for Dipal (survival rate of 52.8–57.5%), 1:100 for Teat (88.7–90.6%), and 1:10 for Blu-gard (100%). No differences in the survival rates of P. zopfii were observed with respect to the duration of exposure to disinfectant. The results of this study support the previous findings that P. zopfii may resist high-temperature treatments, including that applied in the high-temperature, short-time (HTST) pasteurization process. The obtained data also demonstrate the efficacy of the three classes of teat disinfectants against P. zopfii, with the efficacy of iodine being most pronounced. The study emphasizes the necessity of using higher temperatures in the pasteurization of raw milk to kill the Prototheca algae, as well as the particular suitability of the iodine for the control procedures of protothecal mastitis.     

Disinfection in Food Processing – Efficacy Testing of Disinfectants

The key to effective cleaning and disinfection of food plants is the understanding of the type of the soil to be removed from the surfaces. An efficient cleaning and disinfection procedure consists of a sequence of rinses using good quality water with application of detergents and disinfectants. Disinfection is required in food plant operations, where wet surfaces provide favourable conditions for the growth of microbes. The efficacy of disinfectants is usually determined in suspensions, which do not mimic the growth conditions on surfaces where the agents are required to inactivate the microbes. Therefore, the suspension tests do not give adequate information and reliable carrier tests, which mimic surface growth, are needed. In developing a proposal for the testing of disinfectants on surfaces to an analytical standard, it is important to identify the major sources of variation in the procedure. In response to the need for a relatively realistic, simple and reliable test for disinfectant efficacy a method for culturing laboratory model biofilms has developed. The use of artificial biofilms i.e. biofilm-constructs inoculated with process contaminants in disinfectant testing can also be used for screening the activity of various disinfectants on biofilm cells. Both biofilm carrier tests showed clearly that the biofilm protects the microbes against the disinfectants. The chemical cleanliness is also essential in food plants. The total cleanliness of the process lines is mainly based on measuring the microbial load using culturing techniques. These results can give an incorrect picture of the total cleanliness, because the viable microbes do not grow when disinfectants are left on the surface. The luminescent bacteria light inhibition method offers a useful alternative for testing chemical residue left on surfaces after cleaning and disinfection operations.