Prolonged treatment of dermatophytosis caused by Trichophyton indotinea with terbinafine or itraconazole impacts better outcomes irrespective of mutation in the squalene epoxidase gene.

BACKGROUND: Over the past decades, the increasing incidence of recurrent dermatophytosis associated with terbinafine-resistant Trichophyton has posed a serious challenge in management of dermatophytosis. Independent reports of failure of treatment and high minimum inhibitory concentrations (MIC) of antifungals are available, but data correlating MIC and clinical outcomes is still sparse. Therefore, the present study was conducted to evaluate the outcomes of systemic treatment of dermatophytosis and its correlation with MIC of the etiological agents isolated from such patients. METHODS: Retrospective analysis of 587 consecutive patients with dermatophytosis was done from March 2017 to March 2019. Demographic and clinical details of the patients were noted, along with the results of direct microscopy and fungal culture. The isolates were identified by sequencing the internal transcribed spacer region of rDNA. Antifungal susceptibility testing was performed following the CLSI M38 protocol. Mutation in the squalene epoxidase (SE) gene was detected by DNA sequencing and ARMS-PCR. Based on the culture-positivity and prescribed systemic antifungal, patients were categorised into Group I culture-positive cases treated with systemic terbinafine and Group II culture-positive cases treated with systemic itraconazole, each for a total period of 12 weeks. RESULTS: In the present study, 477 (81.39%) were culture-positive; however, 12 weeks follow-up was available for 294 patients (Group I-157 and Group II-137) who were included for statistical analysis. In both groups [Group I-37/63 (51.4%) and Group II-14/54 (58.3%)], a better cure rate was observed if the initiation of therapy was performed within <6 months of illness. Treatment outcome revealed that if therapy was extended for 8-12 weeks, the odds of cure rate are significantly better (p < .001) with either itraconazole (Odd Ratio-15.5) or terbinafine (Odd Ratio-4.34). Higher MICs for terbinafine were noted in 41 cases (cured-18 and uncured-23) in Group I and 39 cases (cured-16 and uncured-23) in Group II. From cured (Group I-17/18; 94.4% and Group II-14/16; 87.5%) and uncured (Group I-20/23; 86.9% and Group II-21/23; 91.3%) cases had F397L mutation in the SE gene. No significant difference in cure rate was observed in patients with Trichophyton spp. having terbinafine MIC ≥ 1or <1 µg/mL (Group I-p = .712 and Group II-p = .69). CONCLUSION: This study revealed that prolonging terbinafine or itraconazole therapy for beyond 8 weeks rather than the standard 4 weeks significantly increases the cure rate. Moreover, no correlation has been observed between antifungal susceptibility and clinical outcomes. The MIC remains the primary parameter for defining antifungal activity and predicting the potency of antifungal agents against specific fungi. However, predicting therapeutic success based solely on the MIC of a fungal strain is not always reliable, as studies have shown a poor correlation between in vitro data and in vivo outcomes. To address this issue, further correlation of antifungal susceptibility testing (AFST) data with clinical outcomes and therapeutic drug monitoring is needed. It also highlights that initiation of the treatment within <6 months of illness increases cure rates and reduces recurrence. Extensive research is warranted to establish a better treatment regime for dermatophytosis.

A single-centre prospective study comparing efficacy and safety of apremilast with cyclosporine in moderate to severe atopic dermatitis.

BACKGROUND: Apremilast regulates several pro-inflammatory signals involved in atopic dermatitis (AD). METHODS: A randomized, open-labelled study was conducted at a tertiary care centre in India. Fifty patients with AD of >1 year duration were randomly assigned in a 1:1 ratio to receive either apremilast (30 mg twice daily after initial titration) or cyclosporine (5 mg/kg/day) for 24 weeks, followed by a 12-week follow-up period. Primary outcome was mean percentage change in Eczema Area and Severity Index (EASI) from baseline to week 24. Secondary outcome measures were proportion of patients achieving EASI 75, EASI 90, ≥2-point improvement in Investigator's Global Assessment (IGA), SCORing Atopic Dermatitis (SCORAD) 75 at week 24 and percentage of patients experiencing ≥1 adverse effect (AEs). RESULTS: Mean percentage change in EASI (standard deviation) was -67.79% [22.44] in the apremilast treatment group and -83.06% [21.20] in the cyclosporine treatment group (p < 0.05). At week 24, 52.38% of patients in the apremilast group and 78.26% in the cyclosporine group achieved EASI 75 (p < 0.05); 14.29% in the apremilast group and 52.17% in the cyclosporine group achieved EASI 90 (p < 0.05) and 80.95% in the apremilast group and 82.60% patients achieved ≥2 point reduction in IGA (p > 0.05). 57.14% of patients achieved SCORAD 75 in the apremilast group and 69.56% in the cyclosporine group (p > 0.05). Mean time taken to achieve EASI 75 in the apremilast group was 4.50 ± 4.62 weeks, while it was 3.96 ± 3.43 weeks in the cyclosporine group (p > 0.05). Incidence of AEs was 28.57% in the apremilast group and 21.74%) in the cyclosporine group. CONCLUSIONS: Apremilast demonstrated lesser efficacy in comparison to cyclosporine; it has the advantage of a favourable safety profile and requires no laboratory monitoring.

Long-term efficacy and safety analysis of single cycle of biosimilar rituximab in pemphigus: A retrospective study of 76 patients from India.

Pemphigus poses a therapeutic challenge and rituximab is increasingly used in its treatment. Long-term data regarding efficacy and safety of rituximab in pemphigus is limited. This study was a retrospective analysis of 76 pemphigus patients with primary endpoint being the percentage of patients achieving complete remission (CR) on/off therapy. Secondary endpoints were time to relapse, mean cumulative dose of prednisolone after rituximab infusion, mean duration of follow up, and adverse events to rituximab if any. A total of 62 (82.7%) attained complete remission on/off treatment, out of which 42 were off therapy. Mean interval between rituximab administration and complete remission off treatment was 6.9 ± 3.7 months. Complete remission off treatment was sustained for a mean duration of 21.4 ± 17.8 months before relapse. Over a mean follow-up duration of 42.7 ± 24.9 months (median 41, maximum 83 months), 22 of 62 patients (35.5%) who had achieved complete remission after the first cycle of rituximab relapsed. A mean total cumulative dose of 8716.3 ± 10533.8 mg prednisolone was prescribed over a mean duration of 18.05 ± 15.64 months after the first cycle of rituximab. Adverse events were noted in 18 out of 76 patients (23.7%) which included infusion reactions (n = 3), minor infections (n = 7), transitory disease flare (n = 6), and mortality (n = 2). No statistically significant correlation was found between remission/relapse rates and age, gender or pemphigus subtype. This study substantiates the long-term efficacy and safety of single cycle of rituximab in pemphigus.

Characterization and Application of a Robust Glucose Dehydrogenase from Paenibacillus pini for Cofactor Regeneration in Biocatalysis.

Glucose dehydrogenases are important auxiliary enzymes in biocatalysis, employed in the regeneration of reduced nicotinamide cofactors for oxidoreductase catalysed reactions. Here we report the identification and characterization of a novel glucose-1-dehydrogenase (GDH) from Paenibacillus pini that prefers NAD+ as cofactor over NADP+. The purified recombinant P. pini GDH displayed a specific activity of 247.5 U/mg. The enzyme was stable in the pH range 4-8.5 and exhibited excellent thermostability till 50 °C for 24 h, even in the absence of NaCl or glycerol. Paenibacillus pini GDH was also tolerant to organic solvents, demonstrating its potential for recycling cofactors for biotransformation. The potential application of the enzyme was evaluated by coupling with a NAD+-dependent alcohol dehydrogenase for the reduction of acetophenone and ethyl-4-chloro-3-oxo-butanoate. Conversions higher than 95% were achieved within 2 h with low enzyme loading using lyophilized cell lysate, suggesting that P. pini GDH could be highly effective for recycling NADH in redox biocatalysis.

A new mitochondrial pool of cyclin E, regulated by Drp1, is linked to cell-density-dependent cell proliferation.

The regulation and function of the crucial cell cycle regulator cyclin E (CycE) remains elusive. Unlike other cyclins, CycE can be uniquely controlled by mitochondrial energetics, the exact mechanism being unclear. Using mammalian cells (in vitro) and Drosophila (in vivo) model systems in parallel, we show that CycE can be directly regulated by mitochondria through its recruitment to the organelle. Active mitochondrial bioenergetics maintains a distinct mitochondrial pool of CycE (mtCycE) lacking a key phosphorylation required for its degradation. Loss of the mitochondrial fission protein dynamin-related protein 1 (Drp1, SwissProt O00429 in humans) augments mitochondrial respiration and elevates the mtCycE pool allowing CycE deregulation, cell cycle alterations and enrichment of stem cell markers. Such CycE deregulation after Drp1 loss attenuates cell proliferation in low-cell-density environments. However, in high-cell-density environments, elevated MEK-ERK signaling in the absence of Drp1 releases mtCycE to support escape of contact inhibition and maintain aberrant cell proliferation. Such Drp1-driven regulation of CycE recruitment to mitochondria might be a mechanism to modulate CycE degradation during normal developmental processes as well as in tumorigenic events.

Comparative assessment of genetic diversity among Indian bamboo genotypes using RAPD and ISSR markers.

Bamboo is one of the important plant for pulp, paper and charcoal industries. After China, India is the second largest bamboo reserve in Asia. Around the globe, wide genetic diversity of bamboo is present which serves as the base for selection and improvement. DNA based molecular markers appears to be a striking substitute for systematic assessment of the genetic diversity in conservation and genetic improvement of plants. DNA based molecular markers such as RAPD and ISSR were used to assess the genetic diversity in 13 bamboo genotypes. Total 120 RAPD and 63 ISSR primers were tested, of which only 42 polymorphic primers (30 RAPD and 12 ISSR), gave reproducible amplification profile and were used in this study. 30 RAPD primers yielded total 645 amplified fragments, of which 623 were polymorphic, and 20.76 polymorphic bands per primer were observed across 13 genotypes. 12 ISSR primers produced 246 amplified fragments, of which 241 were polymorphic, and 20.08 polymorphic bands per primer was observed across 13 different genotypes. The Jaccard's coefficient of RAPD, ISSR and pooled RAPD and ISSR dendrograms ranged from 0.26 to 0.83, 0.23 to 0.86 and 0.26 to 0.84 respectively. The present study found the large genetic diversity present between different elite genotypes of bamboo. Such investigation can deliver a well understanding of the available genotypes, which might be further exploited for the paper industry.

Management of pain in the inpatient and non-surgical outpatient dermatology settings: A narrative review.

Pain is frequently encountered in dermatology practice, which impairs the activities of daily living, adds to psychological morbidity, and therefore compromises the quality of life. It ranges from mild to severe in intensity across various dermatoses and requires prompt addressal and treatment. Diseases such as extensive pemphigus vulgaris and Stevens-Johnson syndrome are especially painful and require a multidisciplinary approach with the involvement of a pain specialist in their management. The main pathogenic types of pain include visceral nociceptive, somatic nociceptive, and neuropathic types, the latter two being most relevant in dermatological disorders. Somatic nociceptive pain is often seen in patients of Stevens-Johnson syndrome/ Toxic epidermal necrolysis, epidermolysis bullosa, pemphigus vulgaris, erythema nodosum, and hidradenitis suppurativa, while neuropathic pain is part of the disease process in dermatoses like leprosy, herpes zoster, and dysesthesia syndromes. Therapeutic approaches to pain management include the use of non-opioids (acetaminophen, non-steroidal anti-inflammatory agents), opioids, and non-pharmacological therapies, along with appropriate management of the underlying dermatosis. World Health Organisation (WHO) analgesic ladder remains the most commonly employed guideline for the management of pain, although treatment needs individualisation depending on the nature and severity of pain (acute/chronic), type of dermatosis, and patient factors. There is a paucity of literature pertaining to pain management in dermatology and this topic is often neglected due to a lack of awareness and knowledge of the topic. The present review aims to discuss the pain pathway, various painful conditions in the setting of medical dermatology practice, and their management along with relevant pharmacology of the commonly used analgesics.

Clinico- Therapeutic Study of Stevens Johnson Syndrome-Toxic Epidermal Necrolysis and Prognostic Significance of SCORTEN in Indian Patients.

Background: Stevens-Johnson syndrome (SJS) and Toxic Epidermal Necrolysis (TEN) are life-threatening dermatological emergencies. SCORTEN (SCORe of toxic epidermal necrolysis) is a validated score to predict mortality; however, there is a paucity of data to determine its usefulness in the Indian population. Objective: To evaluate the accuracy of SCORTEN as a prognostic marker in SJS-TEN. Methods: A prospective observational study was conducted at a tertiary care hospital for two years. SCORTEN was calculated on days one and three of admission. The actual death rates were compared to the predicted rates as estimated by the SCORTEN by standardised mortality ratio analysis (SMR). Results: Of 40 cases included in the study, the mean age was 36.2 ± 14 years (range 11-65) with the male: female ratio being 1.67:1. Antibiotics (37.5%) were the most common group followed by anticonvulsants (22.5%). Comorbidities were observed in 60% of cases, with epilepsy (17.5%) and HIV (human immunodeficiency virus) infection (12.5%) being common. On univariate analysis, heart rate > 120/min, epidermal detachment > 10% BSA, and Se HCO3 (bicarbonate) <20 mmol/L were associated significantly with the death of the subjects (P < 0.05). The observed mortalities were 4.34%, 0, 0 and 80% for SCORTEN 0-1 (3.2%), 2 (12.1%), 3 (35.8%) and 4 (58.3%) respectively when compared to expected mortality. SMR of SJS was 0.69 and of TEN was 1.49. Conclusion: SCORTEN gave an overestimation of mortality in patients with lower scores and an underestimation of mortality in patients with higher scores in our study. Minor refinements based on the study population may increase the predictive accuracy of the original scale.

Presentation of Hansen's disease as Lucio phenomenon in an Indian male.

Lucio phenomenon is a reactional state described in patients with Lucio leprosy and in a few cases of lepromatous leprosy; it is rarely seen outside Mexico and Central America. We report a case of 35-year old labourer who presented with clinical features classical of Lucio phenomenon without any pre-existing cutaneous nodules or infiltrative lesions of either Lucio or lepromatous leprosy. This case report demonstrates the need to consider Lucio phenomenon in patients presenting with clinical features of medium vessel vasculitis even in areas not endemic for Lucio leprosy.

Emerging Role of Baricitinib in Dermatology Practice: All We Need to Know!

Baricitinib is a competitive inhibitor of the Janus Kinase family of non-receptor protein kinases, predominantly acting against JAK-1 and JAK-2 subtypes. By downregulating transcription of various pro-inflammatory cytokines, this drug has shown efficacy across various dermatoses. Approved for severe cases of alopecia areata and moderate-severe atopic dermatitis in adults, baricitinib is being increasingly tried across many other indications with promising results. It is prudent that dermatologists remain aware of boxed warnings and precautions with the use of this much-discussed molecule, including its infectious, thrombotic, cardiovascular, and malignant ramifications. Long-term data on the use of baricitinib in dermatological conditions are lacking and further research is warranted since most data on safety profile is extrapolated from its use in rheumatology. The present review aims to highlight the immunopathogenic mechanisms of JAK-1/2 blockade, approved and off-label uses in dermatology, along with a concise review of laboratory monitoring and the side-effect profile of baricitinib.

Acquired dermal macular hyperpigmentation: an overview of the recent updates.

Acquired dermal macular hyperpigmentation (ADMH), previously known as macular pigmentation of uncertain etiology (MPUE), is an umbrella concept that unifies the distinct but overlapping acquired dermal pigmentary disorders like lichen planus pigmentosus, ashy dermatosis, erythema dyschromicum perstans, Riehl's melanosis and pigmented contact dermatitis. All of these disorders usually lack a clinically apparent inflammatory phase, are characterised by dermal pigmentation clinically and histologically, and have a variable protracted disease course. Recently, a proposal has been made to classify these disorders into those with and without contact sensitisation. Dermoscopy is essentially similar across the spectrum of these disorders, and is useful for diagnosis and therapeutic response monitoring. Scoring system has been validated for the same. The treatment of ADMH remains challenging, with multiple topicals, oral therapies including mycophenolate mofetil, and lasers tried. Need of the hour is randomised controlled trials to enhance the therapeutic armamentarium.

A Clinical-Mycological Study of Dermatophytosis in Western India with Focus on Antifungal Drug Resistance as a Factor in Recalcitrance.

Background: Dermatophytosis have assumed epidemic proportions in India. Antifungal drug resistance solely cannot explain disease magnitude and changing epidemiology. Objectives: Aim of this study was to analyse clinical-mycological aspects of dermatophytosis, and estimate contribution of drug resistance in clinical recalcitrance. Methods: This single-centre observational, cross-sectional, descriptive study was done in tertiary centre of western India after ethical approval, enrolling dermatophytosis patients of all ages and sex. After history and examination, KOH mount and culture in modified SDA medium was done. Culture positive isolates were subjected to E-strip antifungal susceptibility method to test MIC for Terbinafine, Itraconazole, Fluconazole and Griseofulvin. Results: Total 300 patients were included, with mean age of 33.83±27.5 years and male-to-female ratio of 1.22:1; tinea corporis et cruris being commonest, 39.33% (n=118). Only 11.67% (n=35) were treatment naïve, having classical annular morphology. History of topical steroid abuse was found in 81.67% (n=245), with pseudoimbricate lesions in 70.61% (n=173). 86.67% (n=260) had KOH positivity while 83.33% (n=250) had culture positivity: Trichophyton mentagrophytes 45.6% (n=114), followed by Trichophyton rubrum in 34.4% (n=86). A total of 265 patients fit into definition of recalcitrance, from which 12.45%, i.e., 33 isolates showed in-vitro fluconazole resistance. 14.33% (n=43) cases were chronic, 37% (n=111) persistent, 46% (n=138) recurrent while 17% (n=51) had relapse in their disease course. Steroid abuse was the commonest denominator. Conclusion: Role of antifungal resistance in recalcitrant dermatophytosis remains debatable. Stopping steroid abuse, which is often the commonest culprit, with adherence to standard antifungal therapy remains the paradigm in management.

A Comparative Study on Therapeutic Efficacy of Autologous Platelet-rich Plasma, Autologous Platelet-rich Fibrin Matrix, Recombinant Human Epidermal Growth Factor, and Collagen Particles in Nonhealing Leg Ulcers.

Background: Nonhealing leg ulcers are challenging to manage and cause significant patient morbidity. To promote healing, newer techniques focus on delivering/enhancing dermal matrix components. Aim: The aim of this study was to compare the therapeutic efficacy of autologous platelet-rich plasma (PRP), autologous platelet-rich fibrin matrix (PRFM), recombinant human epidermal growth factor (rhEGF), and collagen particles in treating nonhealing leg ulcers. Materials and Methods: Open, randomized prospective study was conducted in a single tertiary center over 2 years where after fulfilling the criteria, randomization was done into four groups. Group A: Autologous PRP (double spin, manual method, weekly); Group B: Autologous PRFM (weekly); Group C: rhEGF (daily application); and Group D: Collagen particles (weekly) along with cleansing, debris removal, and wound dressing. Treatment endpoints were complete healing/6 months of treatment, whichever was earlier. Follow-up was done two weekly by clinical assessment, photographs, and measurement of the ulcer area. Epi info 7 software was used for statistical analysis. Results: A total of 48 patients completed the study, 12 in each group, with mean age: 42.37 ± 4.56 years and male-to-female ratio 2.6:1. Underlying etiology was varicosities (43.75%), traumatic (25%), diabetes (22.91%), and leprosy (8.34%). At baseline, all groups were comparable in terms of patient and ulcer characteristics. Complete healing was seen in 79.17% at the end of 12 weeks: 91.67% of patients from Groups A and B each, and 66.67% from Groups C and D each. The mean time to complete healing was 6.9 ± 2.5 weeks, the least in Group B (4.73 ± 2.3 weeks). Differences between excellent (≥75%) ulcer healing across all groups were statistically significant at the end of 8 weeks where Group B showed maximum improvement. No major adverse events were seen. Conclusion: PRFM resulted in relatively faster ulcer healing compared with other modalities.

Clinical, Laboratory, Histopathological and Therapeutic Profile of Livedoid Vasculopathy: A Case Series of 17 Patients.

Livedoid vasculopathy is a rare disorder clinically presenting with triad of livedo reticularis, leg ulcerations, and atrophie blanche. We present a case series of 17 patients with clinical and/or histopathologically confirmed livedoid vasculopathy from a single tertiary centre in India with female-to-male ratio of 1.5:1 and mean age of 36.12 ± 12.02 years. Presentation with burning pain around ankles was seen in 83.33% of patients, while 100% had atrophie blanche/scarring and 76.47% had retiform ulcers. Hypercholesterolemia was seen in four patients, while systemic lupus erythematosus (SLE), anti-phospholipid antibody with SLE, dermatomyositis and hyper-homocysteinemia were seen in one patient each. The most common histopathology finding was hyaline thrombi within dermal vessels in 94.11%. On treatment with dual anti-platelet therapy, 70.58% of patients could achieve significant improvement in their Visual Analog Scale, Dermatology Life Quality Index and reduction in ulcer scores without serious adverse events. Out of 17 patients, 11 experienced flare in their disease course over one year period of follow-up. This cohort aims to contribute to Indian literature of this underreported entity.

A Comparative, Three-Arm, Randomized Clinical Trial to Evaluate the Effectiveness and Tolerability of Bilastine vs Fexofenadine vs Levocetirizine at the Standard Dose and Bilastine vs Fexofenadine at Higher Than the Standard Dose (Up-Dosing) vs Levocetirizine and Hydroxyzine (in Combination) in Patients with Chronic Spontaneous Urticaria.

INTRODUCTION: Though second-generation antihistamines (SGAH) are first-line drugs in chronic spontaneous urticaria (CSU), 50% of patients do not respond to them. In such patients, guidelines recommend either up-dosing of SGAH or combination of different antihistamines. However, the studies comparing these treatment regimens are limited. METHODS: In this comparative, three-arm study, CSU patients were randomized to receive standard dose of either bilastine, fexofenadine, or levocetirizine for 2 weeks. After 2 weeks of treatment, non-responders received double dose of either bilastine or fexofenadine, while hydroxyzine 25 mg once daily was added in the levocetirizine group. Patients were primarily evaluated for improvement in CSU, quality of life, and somnolence. RESULTS: A total of 110 patients with CSU were recruited. At the end of 4 weeks, 33/39, 26/35, and 22/36 patients in the bilastine, fexofenadine, and levocetirizine groups showed improvement in urticaria symptoms. At week 2, there was no statistical difference in urticaria activity score (UAS7) improvement between any of the groups; however, at week 4, there was a statistical difference between the bilastine and levocetirizine groups (p<0.05). Somnolence was significantly lower in the bilastine group (p<0.05). Bilastine was statistically significant (p<0.05) in the improvement of quality of life as compared to both groups. No major adverse events were reported during study period; however, bilastine was associated with significantly lower levels of AEs compared to levocetirizine (p<0.05). CONCLUSION: Two-fold up-dosing of bilastine improves CSU symptoms without compromising safety as compared to two-fold up-dosing of fexofenadine and combination of first- and second-generation antihistamines.

Real-world Efficacy and Safety of Apremilast Monotherapy in the Management of Moderate-to-severe Psoriasis.

INTRODUCTION: Apremilast is the new oral drug in the management of moderate-to-severe plaque psoriasis with well-established effectiveness and safety in long-term clinical trials and a few real-world studies. However, its effectiveness and safety in Indian setup have not been reported yet. MATERIALS AND METHODS: This was retrospective, single-center, longitudinal, observational cohort study where the total study period was 24 weeks. Effectiveness parameters were the proportion of patients achieving psoriasis area and severity index (PASI) 50, 75, 90, and 100 response at week 16 and 24. Safety was measured as the proportion of patients reporting ≥1 adverse event (AE) during the study period. RESULTS: Data of a total of 70 patients were included in our study. At week 16, 76.92%, 41.53%, 15.38%, and 6.15% patients achieved PASI 50, 75, 90, and 100, respectively. At week 24, 81.53%, 58.46%, 29.23%, and 10.76% patients achieved PASI 50, 75, 90, and 100, respectively. Mean percentage reduction in PASI was 67% at week 24 and DLQI score was reduced significantly to 3.4 from mean baseline DLQI score of 10.8 (P < 0.001). 40% of patients reported ≥1 AE during the study period. 5 out of 70 patients discontinued apremilast due to AE. Nausea was most common AE reported by 21.4% patients followed by diarrhea (18.57%), headache (17.4%), vomiting (8%), weight loss (7.69%), myalgia (6.15%), and gastritis (6.15%). Most of the AEs were of mild-to-moderate severity. CONCLUSION: The results of this study support the long-term use of apremilast monotherapy as an efficacious and safe treatment option for the management of moderate-to-severe plaque psoriasis.

Metabolic engineering of a fast-growing cyanobacterium Synechococcus elongatus PCC 11801 for photoautotrophic production of succinic acid.

BACKGROUND: Cyanobacteria, a group of photosynthetic prokaryotes, are being increasingly explored for direct conversion of carbon dioxide to useful chemicals. However, efforts to engineer these photoautotrophs have resulted in low product titers. This may be ascribed to the bottlenecks in metabolic pathways, which need to be identified for rational engineering. We engineered the recently reported, fast-growing and robust cyanobacterium, Synechococcus elongatus PCC 11801 to produce succinate, an important platform chemical. Previously, engineering of the model cyanobacterium S. elongatus PCC 7942 has resulted in succinate titer of 0.43 g l-1 in 8 days. RESULTS: Building on the previous report, expression of α-ketoglutarate decarboxylase, succinate semialdehyde dehydrogenase and phosphoenolpyruvate carboxylase yielded a succinate titer of 0.6 g l-1 in 5 days suggesting that PCC 11801 is better suited as host for production. Profiling of the engineered strains for 57 intermediate metabolites, a number of enzymes and qualitative analysis of key transcripts revealed potential flux control points. Based on this, we evaluated the effects of overexpression of sedoheptulose-1,7-bisphosphatase, citrate synthase and succinate transporters and knockout of succinate dehydrogenase and glycogen synthase A. The final construct with seven genes overexpressed and two genes knocked out resulted in photoautotrophic production of 0.93 g l-1 succinate in 5 days. CONCLUSION: While the fast-growing strain PCC 11801 yielded a much higher titer than the model strain, the efficient photoautotrophy of this novel isolate needs to be harnessed further for the production of desired chemicals. Engineered strains of S. elongatus PCC 11801 showed dramatic alterations in the levels of several metabolites suggesting far reaching effects of pathway engineering. Attempts to overexpress enzymes deemed to be flux controlling led to the emergence of other potential rate-limiting steps. Thus, this process of debottlenecking of the pathway needs to be repeated several times to obtain a significantly superior succinate titer.