A Review of Available Toxicity Data on the Topical Antimicrobial, Chloroxylenol

Mitigating the inhibition of antibacterial agent chloroxylenol on nitrification system-The role of Rhodococcus ruber in a bioaugmentation system

The chloroxylenol (PCMX) degrading strain was successfully isolated from sludge and identified as Rhodococcus ruber (R. ruber). Afterwards, a bioaugmentation system was constructed by seeding R. ruber into nitrifying sludge to fasten degradation efficiency of highly toxic PCMX from wastewater. Results showed that R. ruber presented high PCMX-degrading performance under aerobic conditions, 25 °C, pH 7.0 and inoculum sizes of 4% (v/v). These optimized conditions were used in subsequent bioaugmentation experiment. In bioaugmentation system, R. ruber could detoxify nitrifiers by degrading PCMX, and the content of polysaccharide in extracellular polymeric substances increased. The quantitative polymerase chain reaction results exhibited that the absolute abundance of 16S rRNA gene and ammonia oxidizing bacteria (AOB) slightly elevated in bioaugmentation system. After analyzing the results of high-throughput sequencing, it was found that the loaded R. ruber can colonize successfully and turn into dominant strains in sludge system. Molecular docking simulation showed that PCMX had a weaker suppressed effect on AOB than nitrite oxidizing bacteria, and R. ruber can alleviate the adverse effect. This study could provide a novel strategy for potential application in reinforcement of PCMX removal in wastewater treatment.

Ecological Risk Analysis for Benzalkonium Chloride, Benzethonium Chloride, and Chloroxylenol in US Disinfecting and Sanitizing Products

Use of three topical antiseptic compounds-benzalkonium chloride (BAC), benzethonium chloride (BZT), and chloroxylenol (PCMX)-has recently increased because of the phaseout of other antimicrobial ingredients (such as triclosan) in soaps and other disinfecting and sanitizing products. Further, use of sanitizing products in general increased during the coronavirus (COVID-19) pandemic. We assessed the environmental safety of BAC, BZT, and PCMX based on best available environmental fate and effects data from the scientific literature and privately held sources. The ecological exposure assessment focused on aquatic systems receiving effluent from wastewater-treatment plants (WWTPs) and terrestrial systems receiving land-applied WWTP biosolids. Recent exposure levels were characterized based on environmental monitoring data supplemented by modeling, while future exposures were modeled based on a hypothetical triclosan replacement scenario. Hazard profiles were developed based on acute and chronic studies examining toxicity to aquatic life (fish, invertebrates, algae, vascular plants) and terrestrial endpoints (plants, soil invertebrates, and microbial functions related to soil fertility). Risks to higher trophic levels were not assessed because these compounds are not appreciably bioaccumulative. The risk analysis indicated that neither BZT nor PCMX in any exposure media is likely to cause adverse ecological effects under the exposure scenarios assessed in the present study. Under these scenarios, total BAC exposures are at least three times less than estimated effect thresholds, while margins of safety for freely dissolved BAC are estimated to be greater than an order of magnitude. Because the modeling did not specifically account for COVID-19 pandemic-related usage, further environmental monitoring is anticipated to understand potential changes in environmental exposures as a result of increased antiseptic use. The analysis presented provides a framework to interpret future antiseptic monitoring results, including monitoring parameters and modeling approaches to address bioavailability of the chemicals of interest. Environ Toxicol Chem 2022;41:3095-3115. © 2022 The Authors. Environmental Toxicology and Chemistry published by Wiley Periodicals LLC on behalf of SETAC.

Biodegradation of Chloroxylenol by Cunninghamella elegans IM 1785/21GP and Trametes versicolor IM 373: Insight into Ecotoxicity and Metabolic Pathways

Chloroxylenol (PCMX) is applied as a preservative and disinfectant in personal care products, currently recommended for use to inactivate the SARS-CoV-2 virus. Its intensive application leads to the release of PCMX into the environment, which can have a harmful impact on aquatic and soil biotas. The aim of this study was to assess the mechanism of chloroxylenol biodegradation by the fungal strains Cunninghamella elegans IM 1785/21GP and Trametes versicolor IM 373, and investigate the ecotoxicity of emerging by-products. The residues of PCMX and formed metabolites were analysed using GC-MS. The elimination of PCMX in the cultures of tested microorganisms was above 70%. Five fungal by-products were detected for the first time. Identified intermediates were performed by dechlorination, hydroxylation, and oxidation reactions catalysed by cytochrome P450 enzymes and laccase. A real-time quantitative PCR analysis confirmed an increase in CYP450 genes expression in C. elegans cells. In the case of T. versicolor, spectrophotometric measurement of the oxidation of 2,20-azino-bis (3-ethylbenzthiazoline-6-sulfonic acid) (ABTS) showed a significant rise in laccase activity during PCMX elimination. Furthermore, with the use of bioindicators from different ecosystems (Daphtoxkit F and Phytotoxkit), it was revealed that the biodegradation process of PCMX had a detoxifying nature.

Removal of Chloroxylenol Disinfectant by an Activated Sludge Microbial Community

Chloroxylenol (CHL) is an antimicrobial ingredient that is frequently used in antiseptics/disinfectants for skin (e.g. hand soap) and non-living surfaces. CHL is an alternative to triclosan and triclocarban, the use of which has recently been banned in some countries. Accordingly, the more widespread use of CHL may significantly increase its occurrence and level in aquatic environments in the near future, eventually resulting in potential ecological risks. Wastewater treatment plants (WWTPs) may be a point source of CHL in natural environments due to extensive discharge through urban waste stream disposal. While the satisfactory removal of CHL in WWTPs is critical for maintaining healthy aquatic ecosystems, the extent of CHL removal and whether CHL causes system upset/failure in WWTPs currently remain unknown. In the present study, we conducted bioreactor operation and batch experiments to investigate the fate and effects of CHL and elucidate the mechanisms underlying degradation at various levels from environmentally relevant to high levels (0.5–5 mg L⁻¹). Bioreactors partially removed CHL (44–87%) via a largely biological route. Microbial association networks constructed using 16S rRNA gene sequencing data revealed selective enrichment and a correlation between Sphingobium and CHL, implying its involvement in the biological breakdown of CHL through dehalogenation and ring hydroxylation pathways. The present results provide insights into the behavior and effects of CHL in activated sludge communities and important information for the sustainable management of CHL that may be an emerging issue in the urban water cycle.

Benzalkonium chloride, benzethonium chloride, and chloroxylenol - Three replacement antimicrobials are more toxic than triclosan and triclocarban in two model organisms

With the recent ban of triclosan (TCS) and triclocarban (TCC) from some personal care products, many replacement antimicrobial compounds have been used. Yet the potential health risk and environmental impact of these replacement compounds are largely unknown. Here we investigated the toxicological effects of three commonly used replacement antimicrobials, benzalkonium chloride (BAC), benzethonium chloride (BEC), and chloroxylenol (CX) to two model organisms, the nematode C. elegans and zebrafish (Danio rerio), and compared them to the banned TCS and TCC. We found that these replacement compounds are not any safer than the banned antimicrobials. In the worm, at least one of the three, BAC, showed comparable toxicity to TCS from organismal to molecular levels, with toxic effects occurring at lower hundred μg/L to lower mg/L levels. In the fish, all three compounds at the tested concentration ranges (0.05-5 mg/L) showed toxicity effects to zebrafish embryos, indicated by hatching delay or inhibition, embryonic mortality, morphological malformations, and neurotoxicity. BAC was the most toxic among the three, with acute lethal toxicity occurring at environmentally relevant concentrations (hundreds of μg/L), which is comparable to the banned TCC. However, the toxicity effects of BAC and TCC occurred within different time windows, potentially suggesting different mechanisms of toxicity. CX was the only compound that induced a "body curvature" phenotype among the five compounds examined, suggesting a unique mode of toxic action for this compound. Furthermore, all five compounds except TCS induced neurotoxicity in fish larvae, indicated by alterations in secondary motoneuron axonal projections. Such neurotoxicity has been largely understudied for these antimicrobials in the past years and calls for further investigations in terms of its underlying mechanisms and ecological significance. These findings strongly indicate that scrutiny should be put on these replacement compounds before their introduction into massive use in personal care products.

Antimicrobial agents, triclosan, chloroxylenol, methylisothiazolinone and borax, used in cleaning had genotoxic and histopathologic effects on rainbow trout

Triclosan (TRC), chloroxylenol (PCMX) and methylisothiazolinone (MIT) have been commonly used as an antimicrobial in soaps while borax (BRX) is used in household cleaning. After using these chemicals, they are washed down drains and getting into the aquatic ecosystem in which they may affect aquatic living organisms. In the present study, the chronic effects of TRC, PCMX, MIT and BRX on genotoxicity, gene expression and histopathology of rainbow trout (Oncorhynchus mykiss) were evaluated for 40 days under semi static condition. The comet assay results indicated that MIT, TRC and PCMX caused significant DNA damage to erythrocytes of the fish. Transcription of SOD, GPX1, GPX2, GSTA, HSP90BB, HSP90BA, CAT, and HSC70A genes were significantly regulated as a result of TRC, PCMX, MIT, and BRX exposure except PCMX exposed GSTA gene. Histological lesions were detected in gills, spleen liver, and trunk kidney of the fish. Lamellar fusion, hyperplasia and epithelial necrosis in gills, melanomacrophage centers and splenic necrosis in spleen, pyknotic nucleus, fat vacuoles, necrotic hepatocytes in liver, cloudy swelling in the tubules, renal tubule epithelial cells degeneration, glomerular capillaries dilation and glomerulus degeneration in kidney, were observed. Our study demonstrates the chronic toxic effect of TRC, PCMX, MIT, and BRX is high in rainbow trout. Therefore, we should be more careful when using these chemicals for cleaning in order to protect aquatic environment.

Salvage therapy of open, infected surgical wounds: a retrospective review using Techni-Care

OBJECTIVE

To determine outcome of infected surgical wounds treated with 3% para-chloro-meta-xylenol + 3% phospholipid PTC [PCMX-PL] (Techni-Care).

DESIGN

Retrospective review of patient records.

SETTING

University hospital.

PATIENTS

Thirty consecutively treated patients (sixteen male, fourteen female) who had developed open infected wounds (twenty-one abdominal [seventy percent], nine extremity [thirty percent]). Mean patient age was 50.1 years. All wounds were treated with commonly practiced wound care techniques (e.g., debridement, frequent dressing changes using saline or topical antibiotics, and, in most cases, parenteral antibiotics) for an extended period of time prior to intervention (mean = 35 days).

INTERVENTIONS

PCMX-PL, a topical microbicide, was used as adjunctive therapy. Eight outcome parameters were analyzed: (1) patient morbidity and mortality; (2) wound healing; (3) number of debridements; (4) wound culture results; (5) leukocytosis (peripheral white blood cell count > 10,000 cells/microl); (6) number of febrile days (temperature > 101 degrees F); (7) length of hospital stay; and (8) number of days of intensive care.

RESULTS

No treatment failures or adverse reactions to PCMX-PL were seen. Twenty (sixty-seven percent) wounds were healed or had been successfully closed while ten (thirty-three percent) were granulating well at sixty-day follow-up. The number of debridements, positive wound cultures, white-blood-cells, and febrile days decreased after PCMX-PL treatment began.

CONCLUSIONS

Despite severe underlying diseases, all patients were discharged from the hospital with closed or healing wounds. We recommend treatment with PCMX-PL as an adjunctive therapy for infected wounds particularly when standard care measures have failed.