Spinosad: in pediculosis capitis

Structural and computational insights into the regioselectivity of SpnK involved in rhamnose methylation of spinosyn

Rhamnose methylation of spinosyn critical for insecticidal activity is orchestrated by substrate specificity of three S-adenosyl-L-methionine (SAM) dependent methyltransferases (MTs). Previous in vitro enzymatic assays indicate that 3'-O-MT SpnK accepts the rhamnosylated aglycone (RAGL) and 2'-O-methylated RAGL as substrates, but does not tolerate the presence of a methoxy moiety at the O-4' position of the rhamnose unit. Here we solved the crystal structures of apo and ligand-bound SpnK, and used molecular dynamic (MD) simulations to decipher the molecular basis of substrate specificity. SpnK assembles into a tetramer, with each set of three monomers forming an integrated substrate binding pocket. The MD simulations of SpnK complexed with RAGL or 2'-O-methylated RAGL revealed that the 4'-hydroxyl of the rhamnose unit formed a hydrogen bond with a conserved Asp299 of the catalytic center, which is disrupted in structures of SpnK complexed with 4'-O-methylated RAGL or 2',4'-di-O-methylated RAGL. Comparison with SpnI methylating the C2'-hydroxyl of RAGL reveals a correlation between a DLQT/DLWT motif and the selectivity of rhamnose O-MTs. Together, our structural and computational results revealed the structural basis of substrate specificity of rhamnose O-MTs and would potentially help the engineering of spinosyn derivatives.

Treatment Modalities of Pediculosis Capitis: A Narrative Review

The review has been done to find out the best-suited treatment modality for pediculosis capitis. Pediatric patients frequently experience pediculosis capitis, a head louse infestation brought on by the Pediculus humanus var. capitis. The primary sign of head lice infestation is a scratchy scalp, and the presence of living nits confirms this diagnosis. When a doctor diagnoses pediculosis as a primary bacterial infection, a bacterial impetignization and secondary infection, and cervical and occipital lymphadenopathy might make the clinical diagnosis more difficult. A proper therapy of pediculosis requires screening and treatment of all close contacts. The careful use of topical pediculicidal treatments, especially permethrin lotion and wet combing with a fine tooth comb, is required for the medical treatment of a head louse infestation. We've tried to outline the key points of treating head lice infestations. There are several treatment alternatives suggested, including over-the-counter permethrin and pyrethrin as well as prescription medications including malathion, lindane, benzyl alcohol, and spinosad.

Spinosad topical suspension (0.9%): a new topical treatment for scabies

INTRODUCTION

Scabies is a highly contagious skin disease caused by the parasitic mite Sarcoptes scabiei. There is no vaccine and for the past 30 years, the first line treatments have been topical permethrin and oral ivermectin. These drugs target mainly the parasite nervous system, killing only the motile stages. As they lack ovicidal activities, repeat treatments are required to achieve complete cure. Incompliance to repeat treatments causing prolonged drug usage, has contributed to emerging drug resistances. In addition, they are not appropriate for all patient categories, specifically for infants and young children or pregnant and breast feeding women. Consequently, new single dose scabicides are urgently needed.

AREAS COVERED

In 2021, spinosad, a drug previously used to treat head lice, was approved by the US FDA as a topical scabies treatment. Here the pharmacology, clinical efficacy and tolerability of this drug are discussed.

EXPERT OPINION

As the first single dose scabicide the formulated 0.9% topical Spinosad solution shows significant efficacy, little systemic absorption and no serious adverse reactions, making it a promising treatment for classical scabies in patients older than four years.

Comparative efficacy and safety of interventions for treating head lice: a protocol for systematic review and network meta-analysis

Background

Head lice infestation is a major public health problem around the globe. Its treatment is challenging due to product failures resulting from rapidly emerging resistance to existing treatments, incorrect treatment applications and misdiagnosis. Various head lice treatments with different mechanism of action have been developed and explored over the years, with limited report on systematic assessments of their efficacy and safety. This work aims to present a robust evidence summarising the interventions used in head lice.

Method

This is a systematic review and network meta-analysis which will be reported in accordance with the Preferred Reporting Items for Systematic Reviews and Meta-analyses statement for network meta-analyses. Selected databases, including PubMed, Embase, MEDLINE, Web of Science, CINAHL and Cochrane Central Register of Controlled Trials will be systematically searched for randomised controlled trials exploring head lice treatments. Searches will be limited to trials published in English from database inception till 2021. Grey literature will be identified through Open Grey, AHRQ, Grey Literature Report, Grey Matters, ClinicalTrials.gov, WHO International Clinical Trials Registry and International Standard Randomised Controlled Trials Number registry. Additional studies will be sought from reference lists of included studies. Study screening, selection, data extraction and assessment of methodological quality will be undertaken by two independent reviewers, with disagreements resolved via a third reviewer. The primary outcome measure is the relative risk of cure at 7 and 14 days postinitial treatment. Secondary outcome measures may include adverse drug events, ovicidal activity, treatment compliance and acceptability, and reinfestation. Information from direct and indirect evidence will be used to generate the effect sizes (relative risk) to compare the efficacy and safety of individual head lice treatments against a common comparator (placebo and/or permethrin). Risk of bias assessment will be undertaken by two independent reviewers using the Cochrane Risk of Bias tool and the certainty of evidence assessed using the Grading of Recommendations, Assessment, Development and Evaluations guideline for network meta-analysis. All quantitative analyses will be conducted using STATA V.16.

Discussion

The evidence generated from this systematic review and meta-analysis is intended for use in evidence-driven treatment of head lice infestations and will be instrumental in informing health professionals, public health practitioners and policy-makers.

PROSPERO registration number

CRD42017073375.

Update on parasitic dermatoses

These are cutaneous diseases caused by insects, worms, protozoa, or coelenterates which may or may not have a parasitic life. In this review the main ethological agents, clinical aspects, laboratory exams, and treatments of these dermatological diseases will be studied.

Case report: a new method for treatment of permethrin - resistant head lice

Head lice (Pediculus humanus capitis) infestation is an important disease worldwide, especially in children under 11 years old. Permethrin is the most common insecticide for treatment of human pediculosis, but nowadays resistance to permethrin and other pyrethroids has caused many treatment failures. The second treatment of choice is malathion.

A Lousy Reason for Surgery Cancellations

Cancellation of surgery has significant adverse impact on patients, health care providers, and their associated facilities. Although head lice infestation has not been shown to be associated with adverse surgical outcomes, it often prompts case cancellation by surgical and anesthesia personnel. The purpose of our study was to evaluate the extent and impact of surgery cancellations due to head lice infestation. In our study, a total of 9 patients were cancelled over a 3-year period. Although there is no direct evidence to show that head lice infestation poses a risk to surgical outcomes, the possibility of underlying secondary bacterial infection at the skin excoriation site is often the concern in these patients. This study offers the first investigation into the impact of head lice infections on operating room cancellations, which may prove to be a potential source of intervention to prevent cancellations.

Spinosad: An effective and safe pediculicide

Although head lice are not a major health hazard, they have been a source of irritation and disgust for thousands of years. Despite the use of over-the-counter (OTC) treatments, it has high prevalence, and epidemics occur regularly. Permethrin 1% is currently recommended as a drug of choice, but many areas have shown resistance to this insecticide. A 0.9% suspension of spinosad, a naturally occurring pest control product, has recently been approved by the USFDA for treatment of pediculosis capitis. It acts by enhancing the action of nicotinic acetylcholine, resulting in paralysis of the parasite. Clinical trials show that spinosad is more effective and safe than current drugs of treatment. Additionally, it does not require nit combing. Spinosad appears as a powerful recruit in the battle against head lice.

Advancements in the treatment of head lice in pediatrics

Head lice infestations occur commonly each year in children of all socioeconomic statuses. However, head lice have become more of a nuisance as resistance to first-line agents, such as permethrin 1% and pyrethrins, has increased. Newer topical products provide unique mechanisms of action without current signs of resistance. As with older agents, proper application of products must be emphasized to ensure that treatment is effective. In addition, nonpharmacologic measures should be taken to avoid reinfestation in the patient and to prevent the spread of lice to close personal contacts.