**2.5 Therapeutic implements**

*Human Microbiome*

**Table 4.**

Different factors that may affect microbiome study

**Findings By**

*Actinobacteria* Decreased Scher et al. [23], Masallat et al. [24] *Bacteroides* Lower Codoner et al. [25], Masallat et al. [24]

factors that affect the microbial community.

Alpha diversity Decreased Scher et al. [23]

*Feacalibacterium* Increased Codoner et al. [25]

*Summary of gut microbiota findings in psoriasis.*

specific niches, as described previously [21].

• Host factors: Not many studies accounted the interpersonal and intrapersonal

• Samples collected from different body sites cannot be compared due to site-

• Sampling method: Several studies showed that different skin layers contain different bacterial communities [48]. Most of the published research on cutaneous microbiota has been based on skin swabs, which represent the surface of the skin. Prast-Nielsen et al. [49] found differences in both diversity and taxonomic composition of the microbiome obtained from swabs and biopsies of the same individual, while an investigation by Stehlikova et al. showed that various sampling approaches (swab, scraping, and biopsy) in affected and unaffected skin of psoriatic patients and in healthy control skin results in similar bacterial diversity despite the different genera abundance that is observed [11]. Grice et al. used three different sampling strategies in the antecubital fossa of five patients: swabs, skin scrapes, and punch biopsies, and concluded that similar microbial populations were captured by each technique and that the dominant species was present in the noninvasive swabs [50]. Recent studies have also reported that the tape stripping method may capture more viable bacteria than the swabbing

Sequencing methods, analysis procedures, and techniques for studying the

• Langan et al. demonstrated that the changes in the microbiome during treatment that were detected by 16S rRNA were not detected by culture data. This suggested that changes in bacterial populations may have been too subtle to be detected by culture, or that changes are predominantly in nonculturable

• Studies using the most often used 16S rRNA have shown that the accuracy of molecular signatures depends on DNA sequencing and downstream analysis protocols. Therefore numerous combinations of primer pairs have been previously tested to select the most appropriate one for skin microbiome surveys;

○ Several studies suggested that primers for V1V3 and V3V4 hypervariable regions were described to sufficiently cover the skin bacterial diversity [20].

however, standardized methodology is still lacking [52].

**76**

method [51].

species [10].

microbiome:

Several studies reveal that psoriasis treatment changes the gut and skin microbiome, such as the correlation between psoriasis systemic treatment and the *Actinobacteria*-to-*Firmicutes* ratio. Biological therapies demonstrated the largest impact [10] during ustekinumab treatment; the composition of microbiota diverged further between lesional and non-lesional skin, across body sites, which could be due to the regression of lesions that returns the skin to more normal environments and increases the body site-specific niches [12]. Secukinumab (anti-IL17) therapy is associated with distinct and more profound gut microbiome shifts than ustekinumab therapy (anti-IL 12/23), in patients with psoriasis by increasing the relative abundance of *Proteobacteria* and decreases in *Bacteroidetes* and *Firmicutes* [55]. Burns et al. demonstrates that UVR has profound qualitative and quantitative influences on the composition of the skin microbiome by an increase in the phylum Cyanobacteria and a decrease in the family Lactobacillaceae and Pseudomonadaceae [56]. This suggests that skin microbiome alterations after UVB treatment could be related to treatment and treatment responses [13]. Thus, it may be implied that the modulation of the gut and skin microbiota can improve disease condition.

Therapeutic modalities that target the shifting microbiota:

The use of orally administered antibiotics, prebiotics, probiotics, and most recently, fecal transplantation [57] also appears to improve the disease condition and may be a practical prospect as a therapeutic avenue.


that the colonization of probiotic bacteria in the gut is mostly transient as they are only detectable for less than 2 weeks after cessation of intake [64]. However, a study by Maldonado-Gómez et al. demonstrated that a certain *Bifidobacterium longum* (*B. longum*) strain was able to persist for over 6 months in a subset of subjects where it was originally absent [65]. A recent, randomized, double-blind, placebo-controlled trial evaluated the effect of a probiotic mixture as co-adjutant treatment together with topical steroids in 90 patients with plaque psoriasis. The results showed a large reduction in the score of severity indexes in the probiotic group, compared with the placebo group. Gut microbiota analysis demonstrated the efficacy of the probiotic in modulation of the composition of the microbiota. After the end of the probiotic or placebo intake, patients were followed up for 6 months. The results showed a lower risk of relapse in patients in the probiotic group [66].

