The mycobactericidal efficacy of ortho-phthalaldehyde and the comparative resistances of Mycobacterium bovis, Mycobacterium terrae, and Mycobacterium chelonae

Determination of o-phthalaldehyde for dose verification of the clinical disinfectant by fluorescent sequential injection analysis

A new automated, generic analytical approach for determining the clinical disinfectant o-phthalaldehyde (OPA) is reported in this study. The proposed sequential injection analysis (SIA) is based on the online reaction of the OPA with glycine/N-acetylcysteine (NAC) in a neutral medium (pH = 7.0) to form a highly fluorescent isoindole derivative. All critical flow and reaction variables were investigated, while validation was carried out in the linearity detection range (0.0075-0.02%). As a result, excellent linearity (R2 > 0.99) and precision (1.5-2.4% for repeatability and 0.7-2.2% for reproducibility) were achieved for the reference OPA solutions. Furthermore, reasonable concentration verification of OPA disinfection (0.2-0.6%) in healthcare institutes can be achieved using the developed fluorescent SIA due to its good sensitivity (0.111 V/%) and precision (1.0-2.3% for intermediate precision) around the minimum effective concentration (MEC) of 0.3% for Cidex-OPA disinfectant.

An Electrochemical o-Phthalaldehyde Sensor Using a Modified Disposable Screen-Printed Electrode with Polyacrylate Hydrogel for Concentration Verification of Clinical Disinfectant

The study proposes an o-phthalaldehyde (OPA) sensor for rapid and reliable detection of OPA in healthcare disinfection practices, based on a hydrogel-modified screen-printed carbon electrode strip. The hydrogel film, which contains glycine and N-acetylcysteine, reacts with OPA to produce a reductive isoindole derivative. The derivative is then oxidized for OPA determination using cyclic voltammetry. The proposed sensor achieves an optimal detection time of 20-30 s and requires only a small analyte volume of 5 µL. It exhibits good precision (10%) and sensitivity (3.3 μA/cm² mM) in a phosphate-buffered solution (pH 7.6), with excellent linearity (R² > 0.97) and precision (<3%) in the detection range (0.2-0.6%) required for clinical OPA solutions. Moreover, the sensor demonstrates good concentration verification of Cidex-OPA disinfection in healthcare institutes, with high sensitivity (18.28 μA/cm² mM) and precision around the minimum effective concentration (0.3%). Overall, the proposed sensor offers a promising and practical solution for accurate and reliable OPA detection in clinical disinfection practices.

The effect of disinfectants and antiseptics on co- and cross-selection of resistance to antibiotics in aquatic environments and wastewater treatment plants

The outbreak of the SARS-CoV-2 pandemic led to increased use of disinfectants and antiseptics (DAs), resulting in higher concentrations of these compounds in wastewaters, wastewater treatment plant (WWTP) effluents and receiving water bodies. Their constant presence in water bodies may lead to development and acquisition of resistance against the DAs. In addition, they may also promote antibiotic resistance (AR) due to cross- and co-selection of AR among bacteria that are exposed to the DAs, which is a highly important issue with regards to human and environmental health. This review addresses this issue and provides an overview of DAs structure together with their modes of action against microorganisms. Relevant examples of the most effective treatment techniques to increase the DAs removal efficiency from wastewater are discussed. Moreover, insight on the resistance mechanisms to DAs and the mechanism of DAs enhancement of cross- and co-selection of ARs are presented. Furthermore, this review discusses the impact of DAs on resistance against antibiotics, the occurrence of DAs in aquatic systems, and DA removal mechanisms in WWTPs, which in principle serve as the final barrier before releasing these compounds into the receiving environment. By recognition of important research gaps, research needs to determine the impact of the majority of DAs in WWTPs and the consequences of their presence and spread of antibiotic resistance were identified.

Guidelines for diagnostic flexible bronchoscopy in adults: Joint Indian Chest Society/National College of chest physicians (I)/Indian association for bronchology recommendations

Flexible bronchoscopy (FB) is commonly performed by respiratory physicians for diagnostic as well as therapeutic purposes. However, bronchoscopy practices vary widely across India and worldwide. The three major respiratory organizations of the country supported a national-level expert group that formulated a comprehensive guideline document for FB based on a detailed appraisal of available evidence. These guidelines are an attempt to provide the bronchoscopist with the most scientifically sound as well as practical approach of bronchoscopy. It involved framing appropriate questions, review and critical appraisal of the relevant literature and reaching a recommendation by the expert groups. The guidelines cover major areas in basic bronchoscopy including (but not limited to), indications for procedure, patient preparation, various sampling procedures, bronchoscopy in the ICU setting, equipment care, and training issues. The target audience is respiratory physicians working in India and well as other parts of the world. It is hoped that this document would serve as a complete reference guide for all pulmonary physicians performing or desiring to learn the technique of flexible bronchoscopy.

Synergistic sporicidal effect of ethanol on a combination of orthophthalaldehyde and didecyldimethylammonium chloride

The objective of this study was to evaluate the potential synergistic effect of ethanol on a combination of orthophthalaldehyde (OPA) and didecyldimethylammonium chloride (DDAC) against the spores of Bacillus subtilis var. Niger. The quantitative carrier test for sporicidal testing of high-level disinfectants according to the guideline of China (Technical Standard for Disinfection 2002) was used as method. Considerable synergistic effect was observed after a 30-min treatment at 20°C. There was an augment in mean log reduction as the concentration of DDAC was increased ranging from 0·2 to 3 g l(-1) in combination with 6 g l(-1) OPA. Ten and 20% ethanol in combination with 6 g l(-1) OPA and 2 g l(-1) DDAC caused more than a 3-log reduction while either 6 g l(-1) OPA, 2 g l(-1) DDAC and 20% ethanol alone or a combination of two of the three agents produced less than a 1-log reduction. Further, 40-min exposure time of combination of OPA, DDAC and 20% ethanol led to greater than a 5-log reduction in spores, and no spore growth was observed following 60- and 90-min exposures.

SIGNIFICANCE AND IMPACT OF THE STUDY

Orthophthalaldehyde (OPA) is very effective at concentrations far lower than its recommended in-use concentration of 0·5% (w/v) and is equally effective against both the gram-negative and gram-positive bacteria. However, it shows lower activity against spores. The synergistic sporicidal effect exhibited by ethanol on a combination of OPA and DDAC can be considered to enhance sporicidal activity for using in situations of sterilization, to reduce in-use concentration of OPA used alone, which may minimize its side effect. OPA may be a more satisfactory and the first-choice agent to replace glutaraldehyde (GTA) as a high-level disinfectant for medical devices.

Transmission of infection by flexible gastrointestinal endoscopy and bronchoscopy

Flexible endoscopy is a widely used diagnostic and therapeutic procedure. Contaminated endoscopes are the medical devices frequently associated with outbreaks of health care-associated infections. Accurate reprocessing of flexible endoscopes involves cleaning and high-level disinfection followed by rinsing and drying before storage. Most contemporary flexible endoscopes cannot be heat sterilized and are designed with multiple channels, which are difficult to clean and disinfect. The ability of bacteria to form biofilms on the inner channel surfaces can contribute to failure of the decontamination process. Implementation of microbiological surveillance of endoscope reprocessing is appropriate to detect early colonization and biofilm formation in the endoscope and to prevent contamination and infection in patients after endoscopic procedures. This review presents an overview of the infections and cross-contaminations related to flexible gastrointestinal endoscopy and bronchoscopy and illustrates the impact of biofilm on endoscope reprocessing and postendoscopic infection.

A review of current disinfectants for gastrointestinal endoscopic reprocessing

Gastrointestinal endoscopy is gaining popularity for diagnostic and therapeutic purposes. However, concerns over endoscope-related nosocomial infections are increasing, together with interest by the general public in safe and efficient endoscopy. For this reason, reprocessing the gastrointestinal endoscope is an important step for effective performance of endoscopy. Disinfectants are essential to the endoscope reprocessing procedure. Before selecting an appropriate disinfectant, their characteristics, limitations and means of use must be fully understood. Herein, we review the characteristics of several currently available disinfectants, including their uses, potency, advantages, and disadvantages. Most disinfectants can be used to reprocess gastrointestinal endoscopes if the manufacturer's guidelines are followed. The selection and use of a suitable disinfectant depends on the individual circumstances of each endoscopy suite.

The differential susceptibility of spores from virulent and attenuated Bacillus anthracis strains to aldehyde- and hypochlorite-based disinfectants

This study compared the sensitivity of spores from virulent and attenuated Bacillus anthracis strains in suspension to inactivation by various chemical disinfectants. Spore suspensions from two virulent strains (A0256 and A0372) and two attenuated strains (Sterne and A0141) of B. anthracis were tested against two aldehyde-based disinfectants and one hypochlorite-based disinfectant. A novel statistical model was used to estimate 4-log₁₀ reduction times for each disinfectant/strain combination. Reduction times were compared statistically using approximate Z and χ² tests. Although there was no consistent correlation between virulence and increased sporicidal resistance across all three disinfectants, spores from the two virulent and two attenuated strains did display significantly different susceptibilities to different disinfectants. Significant disinfectant–strain interactions were observed for two of the three disinfectants evaluated. The comparative results suggest that the use of surrogate organisms to model the inactivation kinetics of virulent B. anthracis spores may be misleading. The accuracy of such extrapolations is disinfectant dependent and must be used with caution.

Disinfection and sterilization in health care facilities: what clinicians need to know

All invasive procedures involve contact between a medical device or surgical instrument and a patient's sterile tissue or mucous membranes. A major risk of all such procedures is the introduction of pathogenic microbes that could lead to infection. Failure to properly disinfect or sterilize reusable medical equipment carries a risk associated with breach of the host barriers. The level of disinfection or sterilization is dependent on the intended use of the object: critical items (such as surgical instruments, which contact sterile tissue), semicritical items (such as endoscopes, which contact mucous membranes), and noncritical items (such as stethoscopes, which contact only intact skin) require sterilization, high-level disinfection, and low-level disinfection, respectively. Cleaning must always precede high-level disinfection and sterilization. Users must consider the advantages and disadvantages of specific methods when choosing a disinfection or sterilization process. Adherence to these recommendations should improve disinfection and sterilization practices in health care facilities, thereby reducing infections associated with contaminated patient-care items.

Reprocessing endoscopes: United States perspective

Endoscopes are used frequently for the diagnosis and therapy of medical disorders. For example, greater than 10000000 gastrointestinal endoscopic procedures are performed each year in the United States. Failure to employ appropriate cleaning and disinfection/sterilization of endoscopes has been responsible for multiple nosocomial outbreaks and serious, sometimes life-threatening, infections. Flexible endoscopes, by virtue of the site of use, have a high bioburden of microorganisms after use. The bioburden found on flexible gastrointestinal endoscopes following use has ranged from 10(5) to 10(10)CFU/ml, with the highest levels being found in the suction channels. Cleaning dramatically reduces the bioburden on endoscopes. Several investigators have shown a mean log(10) reduction factor of 4 (99.99%) in the microbial contaminants with cleaning alone. Cleaning should be done promptly following each use of an endoscope to prevent drying of secretions, allow removal of organic material, and decrease the number of microbial pathogens. Because the endoscope comes into intimate contact with mucous membranes, high-level disinfection is the reprocessing standard after each patient use. High-level disinfection refers to the use of a disinfectant (e.g., FDA-cleared chemical sterilant or high-level disinfectant) that inactivates all microorganisms (i.e., bacteria, viruses, fungi, mycobacteria) but not high levels of bacterial spores. The disinfection process requires immersion of the endoscope in the high-level disinfectant and ensuring all channels are perfused for the approved contact time (e.g., for ortho-phthaladehyde this is 12 min in the US). Following disinfection, the endoscope and channels are rinsed with sterile water, filtered water, or tapwater. The channels are then flushed with alcohol and dried using forced air. The endoscope should be stored in a manner that prevents recontamination. A protocol that describes the meticulous manual cleaning process, the appropriate training and evaluation of the reprocessing personnel, and a quality assurance program for endoscopes should be adopted and enforced by each unit performing endoscopic reprocessing.

An evaluation of Cidex OPA (0.55% ortho-phthalaldehyde) as an alternative to 2% glutaraldehyde for high-level disinfection of endoscopes

Cidex OPA (0.55% ortho-phthalaldehyde) is marketed as a safer alternative to 2% glutaraldehyde for endoscope decontamination. As clinical experience is limited, an evaluation was undertaken in a busy endoscopy unit. Cidex OPA cycle dilution was monitored by manufacturer's test strips and high-pressure liquid chromatography (HPLC). Eight endoscopy staff completed daily occupational health questionnaires before and after its introduction. Patient throughput times were assessed in view of Cidex OPAs reduced disinfection time. HPLC confirmed that Cidex OPA levels are maintained above 0.3% for at least 50 cycles. Indicator strips proved generally reliable when tested by pharmacy staff. However, busy endoscopy staff found the indicator strips difficult to interpret, with 28 out of 223 (12.5%) test results being inappropriately recorded as 'fails'. Two hundred and two questionnaires were completed and no short-term health problems were noted. Apart from bronchoscopy lists, patient turnaround times were not improved. The increased cost of changing to Cidex OPA was estimated as pound 7691 per annum. Staining of washer-disinfectors was of concern as it proved very difficult to remove.

Studies on the mechanisms of the sporicidal action of ortho-phthalaldehyde

AIMS

To determine the mechanism of killing of spores of Bacillus subtilis by ortho-phthalaldehyde (OPA), an aromatic dialdehyde currently in use as an antimicrobial agent.

METHODS AND RESULTS

OPA is sporicidal, although spores are much more OPA resistant than are vegetative cells. Bacillus subtilis mutants deficient in DNA repair, spore DNA protection and spore coat assembly have been used to show that (i) the coat appears to be a major component of spore OPA resistance, which is acquired late in sporulation of B. subtilis at the time of spore coat maturation, and (ii) B. subtilis spores are not killed by OPA through DNA damage but by elimination of spore germination. Furthermore, OPA-treated spores that cannot germinate are not recovered by artificial germinants or by treatment with NaOH or lysozyme.

CONCLUSIONS

OPA appears to kill spores by blocking the spore germination process.

SIGNIFICANCE AND IMPACT OF THE STUDY

This work provides information on the mechanism of spore resistance to, and spore killing by, the disinfectant, OPA.

Endoscopic decontamination: an audit and practical review

A comprehensive audit of endoscopic decontamination practices throughout a 1200-bedded teaching hospital trust was undertaken, prior to a review of the current policy and consideration of alternative disinfectants. Pharmacy records of glutaraldehyde usage, occupational health staff survey data of glutaraldehyde exposure, discussions with all departments where endoscopy might be conducted and information from all companies supplying endoscopes and allied equipment were reviewed. In total, 56 endoscopes were found to be in use in 16 areas of the Trust. In the main designated endoscopy units, compliance with the established policy was generally good, but in other areas, equipment which could tolerate autoclaving was being disinfected with chemical sterilants; some units were still using endoscopes which were not fully immersible and there was widespread use of disinfectant troughs, rather than automated washer-disinfectors. In most cases, this was because staff were concerned about endoscopy equipment passing to a central processing department with potential delays and losses. An updated Trust-wide endoscopy policy, using glutaraldehyde and incorporating the current British Thoracic Society, British Gastroenterological Society and British Urological Society guidelines, has now been implemented. The issues around this and alternative disinfectants are discussed.

Comparison of the mycobactericidal activity of ortho- phthalaldehyde, glutaraldehyde and other dialdehydes by a quantitative suspension test

The mycobactericidal activity of various dialdehydes has been assessed by a quantitative suspension test in both 'clean' and 'dirty' conditions. Test organisms consisted of glutaraldehyde (GTA)-sensitive strains of Mycobacterium chelonae NCTC 946, M. abscessus NCTC 10882, two GTA-resistant M. chelonae strains and M. terrae NCTC 10856 (a proposed M. tuberculosis surrogate). The aldehydes tested were a new high-level disinfectant, ortho-phthalaldehyde (OPA) at 0.5% (v/v) unadjusted pH 6.5 and pH 8, GTA at 0.5% (v/v) pH 8, glyoxal at 0.5% (v/v) pH 8 and 10% (v/v) unadjusted pH 2.8, malonaldehyde sodium salt (NaMDA) at 0.5% (w/v) pH 8 and 10% (w/v) unadjusted pH 7.5 and succinaldehyde at 0.5% (v/v) pH 8. Results showed that 0.5% acidic and alkaline OPA were rapidly mycobactericidal, under both 'clean' and 'dirty' conditions, and more importantly were active against GTA-resistant strains. The washer disinfector isolates of M. chelonae were, as expected, extremely resistant to 0.5% GTA which was slowly mycobactericidal against the other strains. Glyoxal, NaMDA and succinaldehyde were ineffective against all the strains investigated. However, a high concentration of glyoxal exhibited a slow mycobactericidal activity except with M. terrae NCTC 10856, but this was not observed with NaMDA. This evaluation, using a quantitative suspension test based on a European standard, supported the claim that OPA is an effective choice as a high-level disinfectant for medical devices.

Efficacy of high-level disinfectants for reprocessing GI endoscopes in simulated-use testing

BACKGROUND

There has been recent public concern regarding the adequacy of current practices for flexible endoscope reprocessing. High-level disinfection is defined by the Food and Drug Administration (FDA) as a minimum of 6-log reduction of mycobacteria under a worst-case scenario. Several agents are currently approved by the FDA, but published data on their relative efficacies against mycobacteria are lacking. The objective of this study was to determine the efficacy of these agents for high-level disinfection.

METHODS

In simulated-use testing, video endoscopes (5 colonoscopes and 5 duodenoscopes) were each inoculated with 9.0 x 10(7) colony-forming units of Mycobacterium chelonae. Cleaning was performed by using a standardized protocol. Each endoscope was then subjected to chemical disinfection with Cidex (2.0% glutaraldehyde) at 20 degrees C for 20 minutes, Sporox (7.5% hydrogen peroxide) at 20 degrees for 30 minutes, and Steris 20 (0.2% peracetic acid) at 50 degrees C to 56 degrees C for 12 minutes using the Steris System 1 processor. Although not FDA-approved, tests were also conducted by using 70% isopropyl alcohol at 20 degrees C for 20 minutes. These results were compared with disinfection with ethylene oxide gas. All channels were sampled for M chelonae before and after manual cleaning and after disinfection.

RESULTS

Cleaning alone resulted in an average log reduction of 3. Cidex, Sporox, Steris 20, ethylene oxide gas, and isopropyl alcohol, in combination with manual cleaning, each achieved a 6-log or greater reduction of the mycobacterial inoculum. No organisms were recovered from any channel after reprocessing with ethylene oxide and Steris 20.

CONCLUSIONS

Commercially available high-level disinfectants are equally efficacious for reprocessing flexible GI endoscopes when used in conjunction with cleaning and in accordance with recommended guidelines.

New disinfection and sterilization methods

New disinfection methods include a persistent antimicrobial coating that can be applied to inanimate and animate objects (Surfacine), a high-level disinfectant with reduced exposure time (ortho-phthalaldehyde), and an antimicrobial agent that can be applied to animate and inanimate objects (superoxidized water). New sterilization methods include a chemical sterilization process for endoscopes that integrates cleaning (Endoclens), a rapid (4-hour) readout biological indicator for ethylene oxide sterilization (Attest), and a hydrogen peroxide plasma sterilizer that has a shorter cycle time and improved efficacy (Sterrad 50).

Guideline for the use of high-level disinfectants and sterilants for reprocessing of flexible gastrointestinal endoscopes

Glutaraldehyde, 0.2% peracetic acid, 7.5% hydrogen peroxide, 0.08% peracetic acid/1% hydrogen peroxide, and 0.55% ortho-phthalaldehyde are cleared by the FDA for reprocessing flexible gastrointestinal endoscopes. Each product has advantages and disadvantages. All require adherence to published reprocessing protocols in order to maintain the integrity of equipment while providing the public with endoscopic instruments that are safe and effective. All chemicals must be handled with respect. Selection of a product must be weighed against the needs of a particular setting, taking into consideration factors such as compatibility, toxicity, environmental controls and cost.