Corneal bacterial microbiome in patients with keratoconus using next-generation sequencing-based 16S rRNA gene analysis

PURPOSE

To investigate the corneal bacterial microbiome in patients with keratoconus using next-generation sequencing and develop a new perspective on the pathogenesis of the disease.

METHODS

This prospective observational study included 10 patients with keratoconus who underwent corneal crosslinking procedure and 10 healthy controls who underwent photorefractive keratectomy. Patients included in the study were aged 18 years or older. The demographic and clinical characteristics of participants were recorded. Corneal epithelial samples were collected between March 2021 and June 2021. Isolated bacterial DNA from corneal epithelial samples was analyzed using 16 S ribosomal RNA gene analysis. The relative abundance rates at the phylum and genus levels were calculated. Alpha diversity parameters were assessed.

RESULTS

Eleven phyla and 521 genera of bacteria were identified in all participants. At the phylum level, Proteobacteria, Firmicutes, Actinobacteria, and Bacteroidetes were most abundant in both groups. There were no statistical differences between the two groups except Bacteriodetes (p < 0.05). At the genus level, the relative abundance rates of twenty bacteria were significantly different between keratoconus and healthy corneas (p < 0.05). Aquabacterium was the most abundant genus in patients with keratoconus, while Shigella was the most abundant genus in healthy controls. Alpha diversity parameters were lower in patients with keratoconus, although the difference did not reach statistical significance (p > 0.05).

CONCLUSIONS

Our preliminary study revealed that there are similarities and differences in the corneal microbiome between keratoconus and healthy individuals. Further research is required on the relationship between the abnormal corneal microbiome composition and the pathogenesis of keratoconus.

[In Vitro Efficacy of the Venome of Black Scorpion (Androctonus crassicauda) on Leishmania tropica Promastigotes]

Scorpion venom is a substance that shows strong neurotoxic effects with its complex protein content and thus plays an important role for the scorpion in catching and digesting the hunt. Human body stung by a scorpion can show life-threatening systemic effects in a short time, ranging from erythema, pain, edema and local fever to abdominal pain, nausea and vomiting, diplopia and even coma. Scorpion venome is known to possess antimicrobial activity, and some of its compounds have potent antibacterial and antifungal activities. Leishmaniasis is a common vector-borne parasitic infection caused by Leishmania sp. protozoa and can lead skin, mucosa and fatal internal organs involvement in patients . There is a need for new drugs in the treatment of leishmaniasis, because it has been documented lately that there is a growing resistance against antimonial compounds which have been used in its treatment for decades. Leishmania species are known to be susceptible to antimicrobial peptides that act as ion-channel inhibitors, which are known to be present in scorpion venome. In this study, it was aimed to investigate the anti-leishmanial activity of scorpion venome extract obtained from Androctonus crassicauda species in our country. In this context, Leishmania tropica promastigotes which were thawed from liquid nitrogen in our laboratory and first grown in NNN and then RPMI-1640 media, were exposed to different dilutions of the extract containing A.crassicauda venom and meglumine antimonate used in the standard treatment of leishmaniasis and the efficacies on the promastigotes were compared and measured in vitro. This was followed by XTT cell viability test, which assessed whether anti-leishmanial dose of the extract was lethal for human cells or not. Trials showed that the half maximal inhibitory concentration (IC50) values of the venome extract and meglumine antimoniate were 18.12 µg/ml (17.33-18.94) and 8.411 µg/ml (7.922- 8.927), respectively. This preliminary study showed that scorpion venome can be lethal on L.tropica promastigotes in vitro, on relatively higher doses compared to meglumine antimonate. Next step will be to determine the anti-leishmanial proteins in the extract and thus to identify new drug candidates with more specific studies.

Characterisation of the Leishmania donovani/L. infantum Hybrid Isolated from an Autochothonous Kala-Azar Patient: Preliminary Results of an In Vivo Model

OBJECTIVE

In the present study, preliminary outcomes of the in vivo assessment of a Leishmania donovani/L. infantum hybrid isolated from a hospitalised patient with visceral leishmaniasis in Manisa and identified through analysis of the Leishmania-specific ITS-1, hsp70 and cpb gene regions are presented in comparison with reference strains of L. donovani and L. infantum.

METHODS

Three different study groups [(SG); n=16 mice each] and a control group (n=8 mice) were established with female Balb/C mice weighing 25-30 g. Reference L. donovani (MHOM/IN/1980/DD8), reference L. infantum (MHOM/TN/1980/IP1) and a L. donovani/L. infantum hybrid (MHOM/TR/2014/CBVL-LI/ LD), stored in liquid nitrogen, were thawed, cultured and incubated at 25 °C. A 15-μL dose of 1x10⁸/mL promastigotes of three strains was applied to the tail veins of mice in the SG. After the mice were sacrificed, the liver and spleen tissues were removed and stored for immunological, immunohistochemical and pathological analyses.

RESULTS

The presence of infection in the liver and spleen tissues of mice was detected both by a specific enzyme-linked immunosorbent assay test and from the recovery of Leishmania promastigotes from liver and spleen tissues in NNN medium. However, Leishmania amastigotes were not observed in the touch biopsy smears of livers or spleens in either of the SGs. In addition, no evidence of tissue damage was identified in the SGs after immunohistochemical staining (with antibodies against IL-9, CD-117, MBP, CD163, CD4, CD8 and CD31).

CONCLUSION

The obtained results show that hybrid Leishmania and reference L. donovani and L. infantum strains reached the liver and spleens of Balb/C mice in SGs but were of no pathological consequence. Yet, these three Leishmania isolates caused skin lesions when applied subcutaneously in Balb/C mice in another study. The findings presented in this study will be reassessed upon completion of the project, once the final results are obtained.

Efficacy of two plant extracts against acne vulgaris: Initial results of microbiological tests and cell culture studies

BACKGROUND

Acne vulgaris is a common skin disease characterized by increased sebum production, inflammation, and colonization of Propionibacterium acnes (P. acnes) on pilosebaceous follicles.

AIMS

To determine the efficacy of two different plant extracts against P. acnes and to analyze the gene expression levels of IL-1α, SRD5A1, and TNFα in HaCaT cells treated with these plant extracts.

METHODS

Anti-acne extract 1 (AE1) consisted of Juglans regia (walnut husk), Myrtus communis (myrtle leaves), Matricaria chamomilla (chamomilla flowers), Urtica dioica (stinging nettle leaves), and Rosa damascena (rose flowers). Anti-acne extract 2 (AE2) contained Brassica oleracea var. botrytis (broccoli) and B. oleracea var. italica (cauliflower). The antimicrobial activities of the extracts were tested on two different P. acnes strains: the reference strain of P. acnes (ATCC 51277) and the clinical isolate from a patient. The minimum inhibitory concentration (MIC) of the extracts was determined using the broth dilution method. Human keratinocyte cells were used for in vitro tests. Gene expression analyses were performed with RT-qPCR.

RESULTS

The MIC values of the extracts were below 1/2048 µg/mL. In the gene expression analysis, AE1 increased the expression level of TNFα (1.1719, P < 0.0001), suppressed the expression level of IL-1α, SRD5A1 (0.0588, P = 0.0231; 0.3081, P = 0.0351), respectively. AE2 suppressed gene expression level of IL-1α, SRD5A1, TNFα (0.3815, P = 0.0254; 0.3418, P = 0.0271; 0.1997, P = 0.0623).

CONCLUSIONS

Both herbal extracts demonstrated strong antibacterial and anti-inflammatory activity in this preliminary trial. In conclusion, the topical application of these botanical extracts can be good candidates for local acne treatment.