Dilution-neutralization Method Research Articles

Efficacy of Three Povidone Iodine Formulations against Cutibacterium acnes Assessed through In Vitro Studies: A Preliminary Study.

Cutibacterium acnes (C. acnes, formerly known as Propionibacterium acnes) is the major causative agent of prosthetic joint infections (PJI). Treatment of PJI with antibiotics is difficult due to antibiotic resistance and adverse side effects on patients’ health. Proper disinfection of the surgical site using a variety of povidone iodine formulations could prevent C. acnes infection. In the current study, the efficacy of the three povidone iodine (PVP-I) formulations, viz: PVP-I 10% dermic solution, PVP-I 5% alcoholic solution and PVP-I 4% scrub, was tested against C. acnes, in vitro, in the presence of interfering substances mimicking soiling conditions. C. acnes strain ATCC 6919 was used to test the bactericidal activity of the povidone iodine formulations according to the modified dilution-neutralization method described in French Norm EN standard 13727. A 3-log reduction in the bacterial cell count in 60 s was considered to be significant. The results showed that under experimental conditions, the three PVP-I formulations displayed bactericidal activity against the micro-organism, Cutibacterium acnes, and that the lowest concentration of povidone-iodine active against C. acnes was 0.4%. These results are encouraging as PVP-I offers a low-cost and efficient method of disinfection.

Resistance of Clostridioides difficile spores (Clostridiales: Peptostreptococcaceae) to sodium dichloroisocyanurate

Clostridioides difficile is a significant cause of diarrhea in hospitals and the community. This bacterial pathogen is transmitted through the ingestion of endospores, which are challenging to eliminate due to intrinsic resistance to a variety of chemical disinfection agents. The well-characterized laboratory strain CD630 displays low virulence, has not caused outbreaks, and is highly susceptible to disinfectants. Nonetheless, a closely related strain termed NAPCR1 caused outbreaks in Costa Rica and later became endemic in many hospitals from this country. This strain causes disease through unusual mechanisms and is genotypically distinct from CD630. Consequently, its epidemic potential could be influenced by as yet unknown spore phenotypes, such as increased resistance to disinfectants. Objective: To determine whether the NAPCR1 strain is more resistant to a conventional and highly effective C. difficile sporicidal agent than strain CD630 and to identify potential explanatory mechanisms at the genomic level. Methods: We used an in vitro dilution-neutralization method to calculate the sporicidal activity of sodium dichloroisocyanurate (DCC) against purified spores from three subtypes of NAPCR1 isolates (LIBA-2945, LIBA-5761, and LIBA-6276), CD630, and a representative of the highly virulent and epidemic NAP1 strain (LIBA-5758). This phenotypic characterization was complemented with a genomics-steered search of polymorphisms in 15 spore- or sporulation-related genes. Results: Whereas DCC at a final concentration of 0.1 % (w/v) eradicated CD630 endospores with high efficacy (log10 reduction factor (LFR) ≥ 5), it only partially inactivated NAPCR1 (average LFR range: = 1.77-3.37) and NAP1 endospores (average LRF = 3.58). As hypothesized, the three NAPCR1 subtypes tested were more resistant to DCC than strain CD630 (ANOVA, P < 0.05), with LIBA-5761 showing the highest level of DCC resistance overall (ANOVA, P < 0.05). All three NAPCR1 isolates showed large deletions in bclA1. Besides, isolates LIBA-5761 and LIBA-6276 had deletions in bclA2. Conclusions: Our in vitro tests revealed a differential resistance of spores from the C. difficile NAPCR1 strain to DCC. They highlight the importance of continuously evaluating the efficacy of deployed disinfection agents against circulating strains and hint to a potential role of structural proteins from the exosporium in resistance to disinfectants in C. difficile.

Bacteria which are highly resistant to antibiotics are not resistant hydro-alcoholic products

BackgroundPreventing the emergence of antibiotic-resistant bacteria requires strict adherence to standard precautions, including hand hygiene by hydro-alcoholic friction, a technique now recommended. Our study evaluates the in vitro efficacy of an hydro-alcoholic product on four emerging resistant bacteria. Methods and materialsThe product was tested using the dilution-neutralization method using the NF/EN 13727+A2 standard on Staphylococcus epidermidis which is resistant to methicillin and has a reduced reaction to glycopeptide antibiotics, on Enterococcus faecium which is resistant to glycopeptides, as well as on Klebsiella pneumoniae and Pseudomonas aeruginosa which produce carbapenemases. Each of the steps was performed as a blind test on the test product as on the comparator. The surviving bacteria count was measured after 24 and 48 hours’ incubation and the rate of reduction was calculated. ResultsA reduction which was higher than 5 decimal logarithms was observed 30seconds after contact. The test product had an 80% bactericidal concentration on Pseudomonas aeruginosa and 40% on the three other germs. The bactericidal concentration of the comparator was 80% on the four micro-organisms. DiscussionThe present study confirms the effect of hydro-alcoholic products on emerging resistant bacteria. The results make it possible to answer questions from healthcare professionals who often confuse antibiotics and antiseptics and question whether using hydro-alcoholic hand sanitizer is worth it. Proof of efficacy at 30seconds is reassuring since this time is close to that observed when evaluating practices. The data could be completed by performing in vitro tests using the NF/EN 1500 standard.

Effect citronella oil against bacteria strains: Escherichia coli ATCC 10536, Staphylococcus aureus ATCC 6538 and Salmonella typhimurium ATCC 14028

A bactericidal property of Cymbopogon nardus oil (CNO) has been investigated in the previous study. This study aimed to confirm the bactericidal activity of Cymbopogon nardus against different bacteria strains. CNO with the concentration of 1%, 3% and 8% were injected into 100 mL canned tubes. Each sample was diluted by hard water and added with a bacterial suspension test in the presence of interfering substance. The mixture was maintained at 20 °C for 5 min. Water shall be new distilled water-not demineralized water. At the end of contact time, an aliquot was taken, and bactericidal activity was immediately neutralized by the diluted-neutralization method. Neutralizers used in this study were: peptone 10 gL−1, beef extract 5 gL−1, NaCl 5 gL−1, soy lecithin 1 gL−1 and polysorbate 80 20 gL−1; while the interfering substance was 0.3 gL−1 bovine albumin for clean conditions. The number of cells in the bacterial suspension test per treatment was 1.54 x 108 cfu mL−1. It was verified that there was no toxic active chemical compounds found after the application of neutralizer and dilution-neutralization method. The output of this study was a bactericidal against strains: Escherichia coli (ATCC®10536™), Staphylococcus aureus subsp. Aureus (ATCC®6538™) and Salmonella enterica subsp. enterica serovar Typhimurium (ATCC®14028™).

EVALUATION OF BACTERICIDAL ACTIVITY OF AN ANTISEPTIC GELTHROUGH THE DILUTION-NEUTRALIZATION METHOD

Objective: To evaluate the bactericidal activity of an antiseptic gel for hygiene and disinfection of the hands by rubbing.
 Methods: The dilution-neutralization method was used according to Colombian Technical Standard NTC, 2009, 12, 16 in Instituto Colombiano de Normas Técnicas y Certificación (ICONTEC), 5 strains, over 6 different types and with 6 replicas per time were exposed to the antiseptic gel, using Letheen Broth as a neutralizer substance.
 Results: A 99% of reduction was obtained with Staphylococcus aureus 6538, Enterococos hirae 10541, Pseudomonas aeruginosa 15442 and Klebsiella sp, within the first 30 s of exposure to the gel and within the first 60 s of exposure using the Escherichia coli 19538. All strains used coming from American Type Culture Collection (ATCC).
 Conclusion: It was confirmed that the product is effective. In presence of a neutralizer substance, the microorganisms were not inhibit, so the growing reduction occurs due to the action of the product.

Importance of the PN-EN 16615: 2015 standard in the assessment of bactericidal activity of disinfectants intended for soaking wipes in medical area

Introduction: The PN-EN 16615: 2015 standard is intended to determine the acting parameters of disinfectants used for surfaces disinfection with the wiping technique using wipes. It takes into account the application method of disinfectants on the non porous surfaces to be disinfected. The aim of the study was to assess the compliance of the obtained results of control tests with the limit values set in the PN-EN 16615: 2015 standard and to determine the disinfection parameters of the tested product against Staphylococcus aureus. Method: The disinfectant product tests were carried out using standard wipes described in PN-EN 16615: 2015 standard in four contact times of 1, 5, 10, 15 minutes under clean conditions: 0,3 g / l of bovine albumin solution. Results: Obtained results of control and validation of the dilution-neutralization method met the criteria of limit values of the PN-EN 16615: 2015 standard. The test product was active against Staphylococcus aureus within 15 minutes contact time under clean conditions (reduction > 5,59 lg). Conclusions: PN-EN 16615: 2015 standard ensures proper determination of acting parameters of disinfectants intended for use in the form of wipes, what contributes to effective disinfection of the surfaces, especially high-touch surfaces, and prevents the occurrence of cross-contamination of other surfaces in the medical area.

Bacterial toxicity testing and antibacterial activity of parabens

ABSTRACTParabens are used because of their antimicrobial effects, yet they have multiple adverse effects. The aim of this work was to evaluate the bactericidal activity and bacterial toxicity of the most common parabens: methylparaben, ethylparaben, propylparaben, isopropylparaben, butylparaben, isobutylparaben and phenylparaben. The bactericidal action was evaluated by means of the dilution-neutralization method against Escherichia coli and Staphylococcus aureus, and the biotest of inhibition of growth of E. coli was applied for the bacterial toxicity assay. Bactericidal concentrations were reached only for propylparaben, butylparaben and isobutylparaben. The toxicity study showed methylparaben to be the least toxic, whereas the most toxic one was phenylparaben. It can be concluded that the disinfectant activity of the parabens studied is insignificant against S. aureus and E. coli. Acute toxicity is very low, and the inhibitory effect is weak. Our results provide information about the risk–benefit balance of parabens use.

Phenotypic Resistance to Disinfectants and Antibiotics in Methicillin-Resistant Staphylococcus aureus Strains Isolated from Pigs.

The aim of this research was to study the phenotypic resistances to disinfectants and antibiotics in strains of methicillin-resistant Staphylococcus aureus (MRSA) obtained from Canary black pigs. Analyses were performed on 54 strains of MRSA, isolated in Canary black pigs from the province of Tenerife (Spain); all of them carried the mecA gene. The strains were isolated by means of nasal swab samples of healthy pigs, collected under veterinarian supervision. Bactericidal activity of antiseptics and disinfectants was tested by means of the dilution-neutralization method. Susceptibility to the disinfectants glutaraldehyde, peracetic acid and silver nitrate was assessed, as well as to the antiseptics chlorhexidine, benzalkonium chloride and povidone iodine. Susceptibility to a wide array of antibiotics representing the main groups was determined by means of the disc diffusion method. All the strains demonstrated susceptibility to the disinfectants tested at the recommended concentration, and even to dilutions equal to or lesser than 1/16. The most effective antiseptic and disinfectant were, respectively, chlorhexidine and silver nitrate. With regard to the antibiotics, the strains proved to be multiresistant. All presented phenotypic resistance to the β-lactam antibiotics ampicillin, penicillin and cefoxitin, as well as to numerous aminoglycosides, tetracycline and trimethoprim-sulfamethoxazole. It was also observed that 61.1% of the strains were carriers of plasmids. Our results underline that in the strains such as MRSA, which show multiple resistances to antibiotics, the antiseptics and disinfectants show great efficacy. Moreover, as other authors also suggest, for the treatment and prevention of infections caused by MRSA, the use of β-lactam and aminoglycoside antibiotics may be less effective.

Occurrence and susceptibilities to disinfectants of Cryptococcus neoformans in fecal droppings from pigeons in Bangkok, Thailand.

Cryptococcus neoformans is an opportunistic pathogenic yeast that causes meningoencephalitis and deep skin dermatitis in humans and animals. A hygienic strategy using disinfectants on environmental samples can reduce the risk to the public. The objectives were to survey the distribution of C. neoformans in pigeon fecal droppings collected in 11 districts in Bangkok during 2011–2012 and to evaluate the efficacy of three commercial disinfectant products (based on potassium monopersulfate, sodium hypochlorite and quaternary ammonium compounds, respectively). These were evaluated against pure C. neoformans and yeasts resuspended in sterile pigeon feces using the dilution-neutralization method [Europäische NORM (EN) 1656]. In total, 18 of 164 (11%) samples were positive for C. neoformans. These came from only three of the 11 districts, with a prevalence of between 13–56%. Using multiplex PCR, serotype A was the sole group found. For all disinfectants, C. neoformans mixed in feces was tolerated at a higher dose and time exposure than pure isolates. The most effective disinfectant in this study was a 0.12% quaternary ammonium compound that could rapidly eradicate the yeasts mixed in feces. This finding highlights the occurrence and distribution of C. neoformans in the capital city of Thailand and the need to prolong the duration of exposure to disinfectants with pigeon feces.

기포 발생형 타정제의 살균세정 효과

By using effective sanitizers, early block for transmission of pathogens is the effective way to prevent epidermic outbreaks. Here we developed a chlorine oxide bubbling type of sanitizing tablets and evaluated the disinfectant and sanitization effects. The sanitizers showed 99.999% of sanitization effect for Escherichia coli ATCC 10536 and Staphylococcus aureus ATCC 6538 strains for 5 min±10 sec on 20±1℃ in clean condition by dilution-neutralization method. It reduced more than 5 log10 cfu/ml of a legal permission standard of colony reduction. When a few used socks and underwear soaked for one hour in the 0.1% of the sanitizing tablets, no microorganisms were grown on CHROMagar plates. However, on CHROMagar plates of the no sanitizing tablets treated control, about 6.5×104 cfu/ml of Staphylococcus sp., Klebsiella sp. and Enterococus sp. were grown. Furthermore, the sanitizing tablets killed approximately 1.5x108 cfu/ml of E. coli BL21 in 5 minutes. Therefore, we concluded that the chlorine based bubbling type of sanitizing tablets satisfied the legal standard for the regulation of food and drug safety for disinfectants and sanitizers to pathogens and daily supplies.

콘택트렌즈 관리용품의 살균력 효능 검사법 비교

목적: 콘택트렌즈 관리용품의 살균력 효능 검사법 기준 개발을 위하여 막여과법(Membrane filtration method)과 희석중화법(Dilution-neutralization method)의 살균력 검사 결과를 비교하고 시판되고 있는 콘택트렌즈 관리용품의 살균력을 제시하고자 하였다. 방법: 포도상구균(Staphylococcus aureus), 녹농균(Pseudomonas aeruginosa), 세라티아균(Serratia marces cens), 칸디다균(Candida albicans)을 대상으로 하여 FDA(Food and Drug Administration)기준인 막여과법과 식품의약품안전처에서 새롭게 가이드라인으로 제시할 희석중화법의 살균력 효능 결과를 비교하였으며 총 20종 다목적 용액의 살균력을 측정하였다. 결과: 살균효과가 강한 살균 성분 및 관리용품의 효능은 막여과법과 희석중화법 모두 동일한 결과를 나타냈다. 살균효과가 약한 관리용품의 경우는 막여과법 검사시에는 균이 뭉쳐있어 정확한 균 수 측정이 불가능하였으나 희석중화법 검사시는 정확한 균 수 측정이 가능해짐을 확인하였다. 또한 시판되고 있는 관리용품 중에는 살균력 기준을 통과하지 못한 제품이 존재하였으며 특히 세라티아균과 칸디다균에 대한 살균력이 약한 경우가 많았다. 결론: 막여과법에 비해 희석중화법이 소량의 샘플로 더 정확하게 균수를 측정하는 것이 가능하며 결과 확인이 빨라 살균력 효능 검사시 유용하게 사용될 수 있음을 알 수 있었다. Purpose: The present study was aimed to compare the results of disinfection efficacy tested by membrane filtration method with dilution-neutralization method to develop the standard methods for evaluating disinfection efficacy of contact lens care products and to provide the result of disinfection efficacy of commercially available contact lens care products in domestic market. Methods: The results of disinfection efficacy against Staphylococcus aureus, Pseudomonas aeruginosa, Serratia marcescens, Candida albicans evaluated by membrane filtration method as a FDA standard and dilution-neutralization method as newly being a KFDA standard were compared and the disinfection efficacy of 16 multi-purpose solutions was further evaluated. Results: The disinfectants and contact lens care products having strong disinfection efficacy showed same results in both membrane filtration method and dilution-neutralization method. In case of contact lens care products having weak disinfection efficacy, the number of micro-organisms was not able to count since the colony was aggregated when evaluated by membrane filtration method. However, the number of micro-organisms was able to exactly count when evaluated by dilution-neutralization method. In addition, some commercially available contact lens care products did not meet disinfection standard and especially, their disinfection effect was often weak against Serratia marcescen and Candida albicans. Conclusions: It is concluded that dilution-neutralization method will be useful to evaluate disinfection efficacy since it is possible to count micro-organisms more precisely even with small amount of sample and check the results faster compared with membrane filtration method.

Specificity of the neutralizers as the cause of errors in evaluating disinfectant efficacy: an assessment of triclosan

One of the most commonly used methods for assessing disinfectants in vitro is the dilution-neutralization test. Although it is known that using an effective neutralizer is essential for obtaining reliable results, in the case of disinfectants like triclosan, whose neutralization is more complicated, an adequate neutralizer is not always used. Here, we compare the efficacy of different neutralizers described previously, and others that have been modified, against several antiseptic formulations of triclosan. The strains of reference used were Pseudomonas aeruginosa, Enterococcus faecium, Staphylococcus aureus and Escherichia coli. The solutions of antiseptic were triclosan 2% aqueous solution, and three alcoholic solutions containing 2, 0·068 and 0·5% triclosan, respectively. In the dilution-neutralization test, six neutralizers with different degrees of complexity were assayed. Our results show that the antiseptic solutions studied are effective against the strains of reference, with the exception of triclosan 2% aqueous solution against Ps.aeruginosa. Most neutralizers proved ineffective, depending on the antiseptic solution and the bacterial species, particularly in the case of Staph.aureus. These findings confirm a need to test every neutralizer specifically for each disinfectant, at the maximum concentration used, and for every specific bacterial strain. The choice of an adequate neutralizing agent is essential for obtaining precise results in the evaluation of disinfectants using the dilution-neutralization method. In this study, we show that the neutralization of triclosan and some of its commercial solutions is not a simple task, requiring complex neutralizers. Moreover, the action of the neutralizer is shown to depend on the micro-organism tested. Specificity in view of the disinfectant and the micro-organism calls for performing the neutralizing assay in each particular case of application of the dilution-neutralization method. We also demonstrate that some of the neutralizers described for triclosan in previous studies are not sufficiently effective.

Evaluación del método dilución neutralización aplicado a un desinfectante según la Norma Técnica Colombiana 5473 de 2007

<strong>Objective</strong>. Evaluate the dilution-neutralization method proposed in the Colombian Technical Norm 5473/07, by using a gel, alcoholbased disinfectant. <strong>Materials and methods</strong>. This study was done using Pseudomonas aeruginosa ATCC 15442, Staphylococcus aureus ATCC 6538, and Enterococcus hirae ATCC 10541 as the assay microorganisms. The study was carried out at 20±1°C as obligatory temperature and additionally at 36±1°C. Four contact times between microorganisms and the disinfectant were evaluated (0, 2, 5 and 10 minutes). The assay was done both under clean conditions (0.3 g/L of bovine serum albumin), and unclean conditions (3 g/L of bovine serum albumin and 3g/L of sheep erythrocytes). <strong>Results</strong>. The implementation of this method produced precise results in all of the six<br />repetitions used during the assay. The obtained results demonstrated a logarithmic reduction higher than five, demonstrating the bactericidal activity exerted by the disinfectant on the control microorganisms. The established experimental conditions and methodology did not affect negatively the growth of any of the strains of microorganisms. Similarly, the neutralizing used did not inhibit the development of the microorganisms of the assay.<strong> Conclusions</strong>. The method was verified by means of the fulfillment of the limits set by the rule. Our results suggest that the method evaluated by means of the implementation of the protocol established in the Colombian Technical Norm 5473/07, allows evaluating the effectiveness of a disinfectant under selected and controlled experimental conditions.<br /><br /><strong>Key words</strong>: disinfection, clean conditions, unclean conditions, dilution-neutralization method, logarithmic reduction.

Prolonged environmental persistence requires efficient disinfection procedures to control Devriesea agamarum-associated disease in lizards

Devriesea agamarum infection causes chronic proliferative dermatitis, especially in desert dwelling lizards. The present study was concerned with evaluating persistency of D. agamarum in the environment and the evaluation of the efficacy of various disinfection procedures. First, the survival of D. agamarum was assessed both in dermal crusts obtained from clinically and naturally infected lizards, and during periods of prolonged nutrient starvation on dry surface, in moist sand and in distilled water. Secondly, a modified European Suspension Test was performed to determine the efficacy of eight procedures for the disinfection of equipment, environmental surfaces and the topical treatment of D. agamarum-associated dermal lesions. The bacterium proved to persist and remain viable for up to 57 days in dermal crusts and for more than 5months in moist sand and distilled water. In contrast, survival on dry surfaces was limited. The results of the described dilution-neutralization method demonstrated that most of the tested disinfection procedures were sufficient in achieving a 5-decimal logarithmic reduction in the number of D. agamarum colony-forming units. The use of relatively low concentrations of hydrogen peroxide and a boric and peracetic acid solution on the other hand resulted in insufficient reduction in viable counts. Devriesea agamarum can persist for long periods of time in the environment, especially under moist conditions, making the use of suitable disinfection procedures necessary. This study demonstrates the need for a dry environment for most desert lizards and the use of effective disinfection procedures next to antimicrobial treatment to eliminate D. agamarum-associated disease from captive saurian collections.

Indicadores de calidad sanitaria y fenotipificación de Salmonella enterica aislada de pollo crudo comercializado en el área urbana de Mérida, Venezuela

ObjectivesEvaluate the sanitary quality of raw chicken sold in the urban area of the State of Merida, Venezuela and characterize the phenotype of isolated Samonella enterica strains. Materials and methodsA total of 45 raw chicken samples were studied; 15 of them were without seasoning, 15 were with seasoning, and 15 were industrially processed. The following sanitary quality indicators were assessed: Mesophiles Aerobic Bacteria (MAB), total coliforms, E. coli and S. aureus, and the Venezuelan Commission of Industrial Norms methodology was used for that purpose. Microbiological and serological identification of Salmonella was carried out using conventional techniques. Antimicrobial susceptibility was determined by minimal inhibitory concentration (MIC) and the detection of extended-spectrum β- lactamases (ESBLs) was carried out by using the double disc synergy test. Susceptibility to disinfectants was determined by the dilution-neutralization method. Results. Regardless of the (not industrial) samples’ characteristics and/or the commercial establishment, it was determined that the ranges for MAB, total coliform, E. coli and S. aureus counts significantly exceeded limits of acceptability. Strains of Salmonella enterica were isolated in 20% of the samples, whose distribution showed that serovars Heidelberg (55.6%) and Enteritidis (22.2%) were the most frequent. These serovars showed multi-resistance to antibiotics and ESBLs production but were susceptible to the tested disinfectants. Conclusion. This study showed that raw chickens, with and without seasoning, processed in the surveyed commercial establishments do not meet the required microbiological quality standards suitable for human consumption. Therefore, these are short-term perishable products and a haven for important pathogens that threaten consumer health.

Influence of Bovine Serum Albumin on the Antibacterial Activity of Endodontic Irrigants against Enterococcus Faecalis.

It has been demonstrated that organic content of the root canals can influence the antimicrobial capability of chemical irrigants. The aim of this study was to evaluate the effect of bovine serum albumin (BSA), as an organic material, on the antimicrobial activity of several intracanal irrigants. Bactericidal activity of Ethylenediaminetetraacetic acid (EDTA) 17%, citric acid 10%, Sodium hypochlorite (NaOCl) 5.25%, Chlorhexidine 0.2% (CHX), Smear Clear and Cetrimide 0.5% were tested by means of dilution-neutralization method. Contact times were 10 and 30 seconds, 5, 10, 30, 60 minutes and 24 hours. First 950 λ of the medicament was mixed with 50 λ of the bacterial suspension in an Eppendorf test tube. The suspensions were thoroughly mixed. Sterile water served as negative controls. After each contact time, 100 λ of samples was transferred to the Eppendorf test tubes which contained neutralizers. After 5 minutes, 50 λ of serial dilutions were cultured on brain heart infusion agar and incubated in aerobic conditions. Then colonies were counted and reported as cfu/mL. In half of the samples, medicaments were suspended in BSA 0.5% 30 minutes before examination to assess its possible inhibitory effect on the antibacterial activity. NaOCl 5.25%, Cetrimide 0.5% and Smear Clear showed bactericidal activity within seconds after the incubation. BSA had no inhibitory effect on bactericidal activity of these three medicaments. CHX took 5 and10 minutes to kill all bacterial cells in the absence and presence of BSA, respectively. Citric acid and EDTA showed the least antibacterial activity. In this study, NaOCl 5.25%, Cetrimide 0.5% and Smear Clear were significantly more effective against E. faecalis than EDTA 17% and citric acid 10% in the presence and absence of BSA. Also, in the presence of BSA, bactericidal activity of CHX 0.2% against E. faecalis was significantly more than EDTA after 10 and 30 minutes of contact time. EDTA and citric acid showed the least bactericidal activity. [Iranian Endodontic Journal 2009;4(4):139-43].

Activity of three disinfectants and acidified nitrite against Clostridium difficile spores.

To identify environmentally safe, rapidly acting agents for killing spores of Clostridium difficile in the hospital environment. Three classic disinfectants (2% glutaraldehyde, 1.6% peracetyl ions, and 70% isopropanol) and acidified nitrite were compared for activity against C. difficile spores. Four strains of C. difficile belonging to different serogroups were tested using a dilution-neutralization method according to preliminary European Standard prEN 14347. For peracetyl ions and acidified nitrite, the subjective cleaning effect and the sporicidal activity was also tested in the presence of organic load. Peracetyl ions were highly sporicidal and yielded a minimum 4 log10 reduction of germinating spores already at short exposure times, independent of organic load conditions. Isopropanol 70% showed low or no inactivation at all exposure times, whereas glutaraldehyde and acidified nitrite each resulted in an increasing inactivation factor (IF) over time, from an IF greater than 1.4 at 5 minutes of exposure time to greater than 4.1 at 30 minutes. Soiling conditions did not influence the effect of acidified nitrite. There was no difference in the IF among the 4 strains tested for any of the investigated agents. Acidified nitrite demonstrated a good subjective cleaning effect and peracetyl ions demonstrated a satisfactory effect. Cidal activity was shown against C. difficile spores by glutaraldehyde, peracetyl ions, and acidified nitrite. As acidified nitrite and peracetyl ions are considered to be environmentally safe chemicals, these agents seem well suited for the disinfection of C. difficile spores in the hospital environment.