The vector potential of Demodex folliculorum

Characteristics of bacterial community in eyelashes of patients with Demodex blepharitis

BACKGROUND

Demodex blepharitis (DB) is a common disease of the ocular surface. The characteristics of the bacterial community in eyelash roots after Demodex infestation are still unknown. Knowledge of the characteristics of the bacterial community of eyelash follicles in patients with DB can provide valuable insights for guiding the diagnosis and treatment of DB.

METHODS

Twenty-five patients with DB (DB group) and 21 non-DB volunteers (control group) were enrolled in the study. Eyelashes from the upper eyelid of the right eye were sampled, and 16S ribosomal DNA (rDNA) sequencing was performed to determine the V3-V4 regions of the microbial 16S rDNA gene within 1 month of infestation. The sequencing data of the two groups were analyzed and compared. The effect of the bacterium Burkholderia on the survival of Demodex mites was evaluated using Demodex obtained from 12 patients with DB other that the patients in the DB group.

RESULTS

A total of 31 phyla and 862 genera were identified in the DB and control groups. The five most abundant phyla in the two groups were Proteobacteria, Firmicutes, Actinobacteria, Bacteroidetes and Cyanobacteria. The abundance of Actinomycetes was significantly higher in the DB group than in the control group. At the genus level, the five most abundant genera in the two groups were Pseudomonas, Burkholderia-Caballeronia-Paraburkholderia, Rolstonia and Acinetobacter; Clostridium sensu stricto 1 was abundant in the control group and Corynebacterium_1 was abundant in the DB group. Compared with the control group, the abundance of Burkholderia-Caballeronia-Paraburkholderia was 2.36-fold lower in the DB group. Linear discriminant analysis Effect Size (LEfSe) analysis revealed Burkholderia-Caballeronia-Paraburkholderia, SC_I_84_unclassified, Nonmyxobacteria and Succinvibrio to be the major biomarkers in the control group and Catenibacterium and Lachnospiraceae NK4A136 group to be the major biomarkers in the DB group. To explore the performance of these optimal marker models, receiver operational characteristic curve analysis was performed, and the average area under the curve value of Burkholderia-Caballeronia-Paraburkholderia was 0.7448. Burkholderia cepacia isolated from normal human eyelashes was fermented, and the Demodex mites isolated from patient eyelashes were cultured together with its fermented supernatant. The results showed that the fermentation supernatant could significantly reduce the survival time of the Demodex mites, suggesting the potential therapeutic value of this bacterium against Demodex.

CONCLUSIONS

The composition of the bacterial community in the eyelashes of DB patients differed from that in eyelashes of healthy volunteers, revealing a decrease in bacterial diversity in infested eyelashes. This decrease may be related to the occurrence and development of DB. The supernatant of Burkholderia cepacia culture medium was found to inhibit the growth of Demodex in eyelash hair follicles, providing a new insight with potential applications for the clinical treatment of Demodex infestation.

Role of Blepharoexfoliation in Demodex Blepharitis: A Randomized Comparative Study

PURPOSE

The purpose of this study was to evaluate the safety and efficacy of blepharoexfoliation in the treatment of Demodex blepharitis.

METHODS

Patients with microscopically approved Demodex blepharitis were enrolled. Patients in the treatment group were treated once with in-office blepharoexfoliation (BlephEx LLC; Franklin, TN) using tea tree oil 2% shampoo, followed by eyelid scrubs with tea tree oil 2% shampoo twice a day for 8 weeks. Patients in the control group were treated with the same protocol, except for the in-office sham blepharoexfoliation procedure. As the main outcome measurement, the changes in the severity of symptoms [Ocular Surface Disease Index (OSDI) score] were compared. The changes in Demodex count and meibomian gland dysfunction (MGD) severity were compared as the secondary outcome measurements.

RESULTS

Eighty-one patients (36 male and 45 female) were included. The mean age of the patients was 53.56 ± 8.13 years. The mean baseline OSDI score was 33.30 ± 11.80. The mean baseline Demodex count was 4.84 ± 1.49. The Demodex count at the baseline visit was moderately correlated with the baseline OSDI score (R = 0.526, P = 0.011) and baseline MGD severity ( P = 0.02). At the 8-week visit, the OSDI score was 22.62 ± 8.23 and 27.09 ± 9.11 in the blepharoexfoliation and control groups, respectively ( P = 0.016). At the 8-week visit, the Demodex count was 2.6 ± 1.08 and 3.03 ± 1.27 in the treatment and control groups, respectively ( P = 0.025). MGD improved in both groups ( P = 0.84). In the blepharoexfoliation group, the change in the OSDI score was moderately correlated with the baseline OSDI score (R = 0.611, P = 0.01).

CONCLUSIONS

One session of blepharoexfoliation, followed by manual eyelid scrubs was more effective than eyelid scrubs alone in reducing patients' symptoms and Demodex count.

Evaluation of the ocular surface characteristics and Demodex infestation in paediatric and adult blepharokeratoconjunctivitis

BACKGROUND

To evaluate the ocular surface characteristics and the infestation of Demodex in Chinese paediatric and adult blepharokeratoconjunctivitis (BKC).

METHODS

Fifty consecutive patients with BKC and 50 age- and sex-matched healthy subjects were enrolled. Lid margin characteristics and corneal disorders were evaluated under slit-lamp illumination. Four eyelashes were collected from each eye to examine Demodex infestation by light microscopy.

RESULTS

Corneal neovascularization (P = 0.001) and scarring (P = 0.040) were significantly worse in children than in adults with BKC, whereas meibum quality was worse in adults (P = 0.008). Diagnosis delay was longer in children with BKC than in adults (2.2 vs 1.2 years, P = 0.022). Demodex infestation was more frequent in subjects with BKC than in healthy subjects (56% vs 26%, P = 0.002). The lid margin inflammation and meibomian gland dysfunction were worse in Demodex-positive subjects than in Demodex-negative subjects with BKC.

CONCLUSIONS

Children with BKC had severer corneal disorders compared with adult BKC patients, which may be caused by a long-delayed diagnosis. Ocular demodicosis was more common in subjects with BKC. Ocular Demodex infestation was associated with worse lid margin inflammation and meibomian gland dysfunction.

Therapeutic Effect of Intense Pulsed Light on Ocular Demodicosis

PURPOSE

To evaluate the clinical efficacy of Lumenis® M22^TM intense pulsed light (IPL) in reduction of ocular Demodex infestation in eyelashes in a prospective study.

METHODS

Forty patients with ocular demodicosis were recruited. Then half were randomly picked to receive the IPL treatment, while the other half got 5% tea tree oil (as the control group). Demodex counts, the ocular surface disease index (OSDI) score, lid margin abnormalities, conjunctival congestion, tear break-up time (TBUT), corneal staining with fluorescein, meibomian gland (MG) expressibility, meibum quality, modified Schirmer I test with anaesthetic (SIT), were assessed on the day before treatment and after treatment of 30 and 90 days, respectively. Changes in the parameters were compared between the IPL group and the control group on the days after treatment of 30 and 90 days.

RESULTS

No differences were observed in Demodex counts, lid margin abnormalities, conjunctival congestion, corneal staining with fluorescein, MG expressibility, SIT in the two groups on the days after treatment of 30 and 90 days (p > 0.05), whereas there was a statistically significant difference in the OSDI score, TBUT, meibum quality (p < 0.05). The Demodex eradication rate was more thorough in the IPL group (100%) than in the control group (75%).

CONCLUSIONS

IPL shows the preferably therapeutic potential for ocular Demodicosis.

A Study on the Nature of Association between Demodex Mites and Bacteria Involved in Skin and Meibomian Gland Lesions of Demodectic Mange in Cattle

The nature of association between Demodex mites and bacteria involved in bovine demodectic mange lesions and the normal flora inhabiting the skin of noninfected animals was investigated. Demodex bovis and D. ghanensis mites were isolated from the infected purulent material extracted from skin and meibomian gland lesions, respectively. The mites could not be demonstrated in skin brushings or impression smears from the eyes of noninfected cattle. Pathogenic bacteria (Staphylococcus aureus and Streptococcus pyogenes (Group A)) and opportunistic organisms (Proteus vulgaris, Pseudomonas aeruginosa, Staphylococcus epidermidis, and Trueperella pyogenes) were isolated from skin lesions of demodectic mange, and Moraxella bovis and Staphylococcus aureus were isolated from meibomian gland lesions. Bacillus subtilis, Escherichia coli, Proteus vulgaris, Staphylococcus aureus, Staphylococcus epidermidis, and Streptococcus pyogenes (Group A) were isolated from skin brushings from noninfected cattle. The nature of association between Demodex mites and bacteria in demodectic mange lesions is synergistic and of equal significance. Pathogenic and opportunistic bacteria facilitated the establishment of Demodex mites in the lesions produced and provided an excellent microclimate for the mites to propagate and reproduce, resulting in severe and progressive disease. The “high-turnover” granulomatous reaction which characterized the histopathological changes proved that Demodex mites and associated bacteria were persistent and immunogenic.

Clinical treatment of ocular Demodex folliculorum by systemic ivermectin

PURPOSE

To report clinical outcomes of the treatment of ocular Demodex folliculorum with oral ivermectin.

DESIGN

Noncomparative, interventional case series.

METHODS

Setting. Institutional. Study Population. Twenty-four eyes of 12 patients (3 male and 9 female; mean age ± standard deviation, 50.4 ± 21.0 years) with refractory posterior blepharitis with the presence of D. folliculorum in lash samples were enrolled in this study. Intervention. Patients were instructed to take 1 dose of oral ivermectin (200 μg/kg). All patients were instructed to repeat the treatment after 7 days. Main outcome measures. Tear meniscus height, Schirmer I test results, noninvasive tear film break-up time (BUT), quantification of the absolute number of D. folliculorum found in the lashes, and corneal fluorescein and rose bengal staining scores were obtained from all patients 1 day before and 28 days after treatment.

RESULTS

Statistical improvement was observed in the absolute number of D. folliculorum found in the lashes after the treatment with oral ivermectin. Average values of Schirmer I test results and tear film break-up time improved statistically after the treatment of oral ivermectin. No statistical improvement was observed in average lacrimal meniscus height or value of corneal fluorescein and rose bengal staining after treatment with oral ivermectin.

CONCLUSIONS

Ivermectin successfully reduced the number of D. folliculorum found in the lashes of patients with refractory blepharitis. Oral ivermectin may be very useful as a complement in the treatment of D. folliculorum infestation with ocular manifestation, especially in cases of unsuccessful treatment related to patient compliance.

Ocular demodicosis as a potential cause of pediatric blepharoconjunctivitis

PURPOSE

To report Demodex infestation in pediatric blepharoconjunctivitis.

METHODS

A retrospective review of 12 patients, with ages from 2.5-11 years, with chronic blepharoconjunctivitis who failed to respond to conventional treatments. Demodex was detected by lash sampling and microscopic examination. Patients were treated with 50% tea tree oil (TTO) eyelid scrubs or 5% TTO ointment eyelid massages for 4-6 weeks.

RESULTS

Demodex mites were found in all, but 1 case had cylindrical dandruff in the lashes. After 1 week of TTO treatment, all patients showed dramatic resolution of ocular irritation and inflammation while Demodex counts dropped. All corneal signs resolved within 2 weeks except for a residual anterior stromal scar in 1 eye. During a follow-up period of 8.3 ± 4.6 months, 1 patient showed recurrent inflammation, which was successfully managed by a second round of TTO treatment.

CONCLUSIONS

Demodicosis should be considered as a potential cause of pediatric refractory blepharoconjunctivitis. Eyelid scrubs or massage with TTO could be an effective treatment regimen in these cases.

Clinical treatment of ocular demodecosis by lid scrub with tea tree oil

PURPOSE

To report clinical outcome of treating ocular demodecosis by lid scrub with tea tree oil (TTO).

METHODS

Retrospective review of clinical results in 11 patients with ocular Demodex who received weekly lid scrub with 50% TTO combined with daily lid hygiene with tea tree shampoo.

RESULTS

These 11 patients also had meibomian gland dysfunction (n = 7) manifesting abnormal lipid film with slow lipid film spread, intermittent trichiasis (n = 5), and subjective lash loss (n = 4), suggesting damage to the meibomian glands and lash follicles. In addition, conjunctival inflammation (n = 8) was associated with conjunctivitis (n = 5), conjunctivochalasis (n = 3), findings suspicious for pemphigoid (n = 2), and recurrent pterygium (n = 2). After TTO lid scrub, the Demodex count dropped to 0 for 2 consecutive visits in less than 4 weeks in 8 of 11 patients. Ten of the 11 patients showed different degrees of symptomatic relief and notable reduction of inflammatory signs. Significant visual improvement in 6 of 22 eyes was associated with a stable lipid tear film caused by significant reduction of lipid spread time. Lid scrub with 50% TTO caused notable irritation in 3 patients.

CONCLUSION

Demodex potentially causes ocular surface inflammation, meibomian gland dysfunction, and lash abnormalities. Lid scrub with TTO can effectively eradicate ocular Demodex and result in subjective and objective improvements. This preliminary positive result warrants future prospective investigation of Demodex pathogenicity.

Klassifikation der Erkrankungen der Augenoberfl�che

The ocular surface consists of the lid margin, conjunctiva and cornea which together with the tear system represent a functional entity. The diagnosis of ocular surface disease can be very difficult due to the similarity of various disease entities. The classification should be made on the pathological and pathophysiological characteristics of ocular surface disease. The first part of the classification comprises diseases of the lid margin, the tear system as well as diseases of the conjunctiva. Both the clinical presentation as well as the underlying pathophysiological and pathological characteristics of the most important ocular surface diseases are reviewed.

The Demodex mite population in rosacea

BACKGROUND

The cause of rosacea is unknown; among other factors a causative role has been postulated for the hair follicle mites Demodex folliculorum and Demodex brevis.

OBJECTIVE

Our purpose was to compare the population density of Demodex mites in facial skin of defined categories of patients with rosacea with control subjects. We also assessed the impact of tetracycline therapy on the mite population.

METHODS

The population density and distribution of Demodex mites were studied in the facial skin of 42 patients with rosacea and 42 age- and sex-matched control subjects. Mites were counted in measured skin surface biopsy specimens obtained from six standard facial sites with cyanoacrylate glue.

RESULTS

The mean mite count was 49.8 (range 2 to 158) in patients with rosacea and 10.8 (range up to 97) in control subjects (p < 0.001); the highest density of mites was found on the cheeks. A statistically significant increase in mites was found in all subgroups of rosacea, being most marked in those with steroid-induced rosacea. Mite counts in patients with rosacea before and after a 1-month course of oral tetracycline showed no significant difference.

CONCLUSION

Increased mites may play a part in the pathogenesis of rosacea by provoking inflammatory or allergic reactions, by mechanical blockage of follicles, or by acting as vectors for microorganisms.

The presence of the parasite Demodex folliculorum on the skin surface of the eyelid

It is well established that Demodectic mites can infest the meibomian glands, eyelash and hair follicles of the eyelid. In this study, scanning electron microscopy revealed Demodex folliculorum occurring freely on the skin surface of the eyelid. This indicates some mobility and implies further vector potential. Exoskeletons from these parasites also occur on the eyelid.

Demodicosis of ophthalmic concern

Hair-follicle mites are the only metazoan organism commonly found in the pilosebaceous components of the eyelid of man. Our study showed that Demodex folliculorum in all stages is found in the small hair follicles and the eyelash hair follicles. This species, in adult and immature forms, consumes epithelial cells, produces follicular distension and hyperplasia, and increases keratinization leading, in eyelashes, to cuffing consisting of keratin and lipid moieties. Demodex brevis (in all stages) is present in the eyelash sebaceous glands, small hair sebaceous glands, and in the lobules of the meibomian glands. Adults and immature forms consume the gland cells in all of these loci and, when infestations are heavy, can affect the formation of the superficial lipid layer of the tear film coacervate. Comparative studies of demodicids from man and other mammals suggest that keratinization, hyperplasia, distension, and melanocyte aggregation may be even more extensive if large populations of D. folliculorum build up in the follicles of the eyelid. Large populations of D. brevis may destroy the glandular cells, produce granuloma in the eyelid, and plug the ducts of the meibomian or sebaceous glands. Further studies may incriminate either or both species, in conjunction with microorganisms, as transfer agents or synergists, or both, in producing ocular disease in man. Prevention and control of these mites must await experimental studies with infested laboratory animals (such as the squirrel monkey, Saimiri sciureus). These mites are probably most vulnerable during transfer stages, when they leave their glandular or follicular habitats.