Joel Fleury Djoba Siawaya - Academia.edu (original) (raw)

Papers by Joel Fleury Djoba Siawaya

Research paper thumbnail of Prostate malignant tumor and benign prostatic hyperplasia microenvironments in black African men: Limited infiltration of <scp>CD8</scp>+ T lymphocytes, <scp>NK</scp>‐cells, and high frequency of <scp>CD73</scp>+ stromal cells

Cancer reports, Apr 24, 2023

Research paper thumbnail of Phytochemical screening, antioxidant and antimicrobial potential of stem barks of Coula edulis Baill. Pseudospondias longifolia Engl. and Carapa klaineana Pierre. from Gabon

Asian Pacific Journal of Tropical Disease, Jul 1, 2016

Objective To evaluate the phytochemical constituents, antioxidant and antimicrobial potential of ... more Objective To evaluate the phytochemical constituents, antioxidant and antimicrobial potential of water-acetone, water-ethanol and water extracts of Coula edulis (C. edulis), Pseudospondia longifolia (P. longifolia) and Carapa klaineana (C. klaineana).

Research paper thumbnail of Molecular markers of infectious diseases

DOAJ (DOAJ: Directory of Open Access Journals), 2009

Research paper thumbnail of Corrigendum: Microbiology laboratories involved in disease and antimicrobial resistance surveillance: Strengths and challenges of the central African states

African Journal of Laboratory Medicine, May 9, 2023

Research paper thumbnail of Higher IL-8 Response to &lt;i&gt;Mycobacterium tuberculosis&lt;/i&gt; Antigens in Women above 40 Years

Journal of tuberculosis research, 2021

Objective: Circulating levels of sex hormones vary with age. Moreover, there is emerging evidence... more Objective: Circulating levels of sex hormones vary with age. Moreover, there is emerging evidence supporting that sex hormones have an influence on the immune response of women. Here, we investigated age-associated levels of sex hormones and Mycobacterium tuberculosis (Mtb) specific cytokines response in women. Design: Using immunoassay methods, we have measured and compared secretion levels of E2, P4 and Mtb specific secretion of 11 cytokines including Granulocyte-macrophage colony-stimulating factor (GM-CSF), Interferon gamma (IFN-γ), Interleukin 1 beta (IL-1β), IL-10, IL-12 (p70), IL-2, IL-4, IL-5, IL-6, IL-8, and Tumor necrosis factor (TNF-α) in forty-two (42) HIV-negative females. Results: Estradiol (E2) and progesterone (P4) levels were significantly higher in younger women irrespective of their LTB status (p < [0.0001-0.05]). Mtb IL-8 specific response was significantly higher in women above 40 years old than in women under 40 years old. Conclusion: In premenopausal women, there is an increase in the pro-inflammatory cytokine IL-8 secretion in response to Mtb-antigen. This observation suggests an underlying link between the pro-inflammatory cytokine and age associated hormonal changes, which may have implications on the course of tuberculosis infection women.

Research paper thumbnail of Allergen sensitization and polysensitization pattern of adults and children in an urban Sub-Saharan African setting (Libreville, Gabon)

Journal of Allergy and Clinical Immunology: Global

Research paper thumbnail of Microbiology laboratories involved in disease and antimicrobial resistance surveillance: Strengths and challenges of the central African states

African Journal of Laboratory Medicine

Table 1. Country scores for veterinary laboratory capacity in the ECCAS. Attributes of evaluation... more Table 1. Country scores for veterinary laboratory capacity in the ECCAS. Attributes of evaluation of the performance of veterinary services Countries with available PVS evaluation reports, year of evaluation Burundi, 2017 4 Cameroon,

Research paper thumbnail of HIV-exposed uninfected compared with unexposed infants show the presence of leucocytes, lower lactoferrin levels and antimicrobial-resistant micro-organisms in the stool

Paediatrics and International Child Health, 2019

Background: HIV-exposed uninfected (HEU)-infants have been shown to be particularly vulnerable to... more Background: HIV-exposed uninfected (HEU)-infants have been shown to be particularly vulnerable to infections. In this population, disturbance of the gut micro-environment might increase their susceptibility to enteric diseases and even favour the translocation of bacteria in the bloodstream. Methods: The gastro-intestinal micro-environment was explored in 22 HEU infants and 16 HIV-unexposed (HU) infants aged 6-24 weeks. Faecal leucocytes, firmicutes (gram-positive bacteria) and gracilicutes (gram-negative bacteria) were assessed by cytology. Faecal lactoferrin and sIgA were measured by ELISA. The spectrum of microorganisms in infants' stool was analysed by culturing. Results: HEU infants were 14 times more likely to have leucocytes in their stool than HU infants (p < 0.005). The lactoferrin level was significantly lower in HEU infants than in HU infants (p = 0.02). Potentially pathogenic bacteria such as Escherichia coli were more prevalent in HEU than in HU infants (64% vs 23.5%). Also, E. coli strains resistant to key antibiotics including co-trimoxazole, β-lactam (cephalosporins included) and tetraclines were observed in some HEU infants. Conclusion: HEU infants are more likely to present an inflamed digestive tract as highlighted by the presence of leucocytes. In addition, there is a real risk of colonisation of HEU infants' microbiota by resistant microorganisms .

Research paper thumbnail of Genital Mycoplasma infections and their resistance phenotypes in an African setting

European Journal of Clinical Microbiology & Infectious Diseases, 2015

We investigated the antimicrobial susceptibilities of mycoplasmas in Gabonese men and women. A to... more We investigated the antimicrobial susceptibilities of mycoplasmas in Gabonese men and women. A total of 1,332 men and women were included in the study. Sperm, urine, ureteral or vaginal swabs were collected from the subjects. Mycoplasmas identification and antimicrobial susceptibility to azithromycin, clarithromycin, erythromycin, josamycin, pristinamycin, doxycycline, tetracycline, ofloxacin and ciprofloxacin were tested using the Mycoplasma IST 2 kit. 794 subjects were positive for Mycoplasma. Respectively, 1.6 % and 82.24 % of subjects were singly infected with M. hominis and Ureaplasma urealyticum and 15.87 % had a mixed infection. M. hominis isolates were resistant to erythromycin and had an intermediate (I) to resistant (R) profile to azithromycin and clarithromycin. 84.6 % of M. hominis strains were sensitive (S) to josamycin and pristinamycin. 30.8 % and 92.3 % of M. hominis strains were sensitive to tetracycline and doxycycline, respectively. 76.9 and 84.6 % of M. hominis isolates were sensitive to ciprofloxacin and ofloxacin, respectively. The sensitivity rates of U. urealyticum strains were 45.23 %, 47.7 %, 63.84 %, 90.8 % and 92 % for azithromycin, erythromycin, clarithromycin, pristinamycin and josamycin, respectively. U. urealyticum strains showed 62.2 % and 79.7 % sensitivity to tetracycline and doxycycline, respectively. The resistance rates to azithromycin, clarithromycin and erythromycin for samples with mixed infection were 72.8 %, 84.7 % and 85.6 %, respectively. Josamycin and pristinamycin were 81.5 % effective on samples with mixed infection. The sensitivity rates of samples with mixed infection to tetracycline, doxycycline, ciprofloxacin and ofloxacin were 32 %, 69.6 %, 8.9 % and 18.5 %, respectively. Sub-Saharan Africa needs to use antibiotics rationally, as falling to do so would compromise the management of infectious diseases.

Research paper thumbnail of Phytochemical screening and cytotoxicity studies of Chrysophyllum pruniforme Pierre ex Engl. barks

Pharmacognosy Research, 2013

Research paper thumbnail of Use of GeneXpert Remnants for Drug Resistance Profiling and Molecular Epidemiology of Tuberculosis in Libreville, Gabon

Journal of clinical microbiology, Jul 1, 2017

Multidrug-resistant (MDR) and extensively drug resistant (XDR) strains of Mycobacterium tuberculo... more Multidrug-resistant (MDR) and extensively drug resistant (XDR) strains of Mycobacterium tuberculosis pose major problems for global health. The GeneXpert MTB/RIF (Xpert) assay rapidly detects resistance to rifampin (RIF(r)), but for detection of the additional resistance that defines MDR-TB (MDR tuberculosis) and XDR-TB, and for molecular epidemiology, specimen cultures and a biosafe infrastructure are generally required. We sought to determine whether the remnants of sputa prepared for the Xpert assay could be used directly to find mutations associated with drug resistance and to study molecular epidemiology, thus providing precise characterization of MDR-TB cases in countries lacking biosafety level 3 (BSL3) facilities for M. tuberculosis cultures. After sputa were processed and run on the Xpert instrument, the leftovers of the samples prepared for the Xpert assay were used for PCR amplification and sequencing or for a line probe assay to detect mutations associated with resistanc...

Research paper thumbnail of Vitamin D2 versus vitamin D3 as a risk factor in compromised bone health

The Moldovan Medical Journal

Background: Vitamin D plays an important role in the prevention of many diseases. More than 1 bil... more Background: Vitamin D plays an important role in the prevention of many diseases. More than 1 billion people worldwide suffer from vitamin D deficiency. Vitamin D deficiency can contribute to the development of 16 types of cancer (breast, colon, prostate, etc.), cardiovascular diseases, stroke, autoimmune diseases, periodontal pathologies, transplant failure in endo-alveolar surgery, etc. There are several risk factors that would prevent the achievement of treatment objectives. The national protocol for deficiency rickets prevention privileges vitamin D2 versus vitamin D3, which creates a medical risk factor compromising oral health in both children and adults. The article provides sufficient arguments in favour of vitamin D3 vs vitamin D2 prescription for prophylactic and treatment purposes. Conclusions: Considering that vitamin D deficiency is currently a global public health problem, it can be proposed to declare vitamin D deficit/deficiency a priority public health problem at th...

Research paper thumbnail of Emergence of B.1.1.318 SARS-CoV-2 viral lineage and high incidence of alpha B.1.1.7 variant of concern in the Republic of Gabon

International Journal of Infectious Diseases, 2021

Objective: Variants of concern (VOCs) associated with relatively high transmissibility appear to ... more Objective: Variants of concern (VOCs) associated with relatively high transmissibility appear to be rapidly spreading in Gabon. Therefore, it is imperative to understand the distribution of several VOCs in the population, which could have implications for transmissibility and vaccine efficacy. Methods: Between February and May 2021, SARS-CoV-2 genomes were sequenced using the Oxford nanopore MinION method and the respective genome diversity was elucidated. Phylogenetic analysis was performed and genomes were classified using pangolin lineages. Results: The results highlighted an increase (46%) in the alpha VOC (B.1.1.7) in the Gabonese population over the study period. In addition, an increase (31%) in the B.1.1.318 lineage, which is associated with high transmission and impaired vaccine efficacy (D614G + E484K + Y144del), was detected. Conclusion: With the second wave ongoing, these findings highlight the need for surveillance of the SARS-CoV-2 genome in the Republic of Gabon and should provide useful guidance to policymakers in selecting an appropriate vaccine for this population.

Research paper thumbnail of Purifying Selection in Human Immunodeficiency Virus-1 pol Gene in Perinatally Human Immunodeficiency Virus-1-Infected Children Harboring Discordant Immunological Response and Virological Nonresponse to Long-Term Antiretroviral Therapy

Journal of Clinical Medicine Research, 2020

Background: Biological monitoring of antiretroviral treatment (ART) in human immunodeficiency vir... more Background: Biological monitoring of antiretroviral treatment (ART) in human immunodeficiency virus (HIV)-infected pediatric population remains challenging. The aim of the present study was to assess the long-term HIV-1 genetic diversity in pol gene in HIV-1-infected children in virological failure under antiretroviral regimen adapted according to the successive World Health Organization (WHO) guidelines for resource-constrained settings. Methods: HIV-1 diversity in pol gene was assessed in HIV-1-infected children and adolescents born from HIV-infected mothers (median age at follow-up: 13.8 years) in virological failure (VF +) despite longterm regimen recommended by the WHO. The numbers of nonsynonymous substitutions per potential nonsynonymous site (dN) and of synonymous substitutions at potential synonymous sites (dS) in HIV-1 pol gene and the dN/dS ratios were used to estimate the selective pressure on circulating HIV-1. Results: The immunological responses to ART basically corresponded to: 1) Full therapeutic failure with immunological (I-) and virological nonresponses in one-quarter (24.6%) of study children ((I-, VF +) subgroup); 2) Discordant immunovirological responses with paradoxical high CD4 T cell counts (I +) and high HIV-1 RNA load in the remaining cohort patients (75.4%) ((I + , VF +) subgroup). The mean dS was 1.8-fold higher in (I + , VF +) than (I-, VF +) subgroup (25.9 ± 18.4 vs. 14.3 ± 10.8). In the (I + , VF +) subgroup, the mean dS was 1.6-fold higher than the mean dN. Finally, the mean dN/dS ratio was 2.1-fold lower in (I + , VF +) than (I-, VF +) subgroup (0.6 ± 0.3 vs. 1.3 ± 0.7), indicating purifying selection in the immunovirological discordant (I + , VF +) subgroup and positive selection in the immunovirological failure (I-, VF +) subgroup. Conclusions: Children and adolescents in immunovirological therapeutic failure harbor positive selection of HIV-1 strains favoring diversifying in pol-encoded amino acids. In contrast, children with persistent discordant immunovirological responses show accumulation of mutations and purifying selection in pol gene sequences, indicating limited genetic evolution and likely suggesting genetic adaptation of viruses to host functional constraints.

Research paper thumbnail of Distinct serum biosignatures are associated with different tuberculosis treatment outcomes

Tuberculosis, 2019

Distinct serum biosignatures are associated with different tuberculosis treatment outcomes. Tuber... more Distinct serum biosignatures are associated with different tuberculosis treatment outcomes. Tuberculosis, 118.

Research paper thumbnail of Changes of C-reactive protein and Procalcitonin after four weeks of treatment in patients with pulmonary TB

Journal of Clinical Tuberculosis and Other Mycobacterial Diseases

Research paper thumbnail of Creatine kinase-(MB) and hepcidin as candidate biomarkers for early diagnosis of pulmonary tuberculosis: a proof-of-concept study in Lambaréné, Gabon

Infection, 2022

Background The present study aimed to evaluate the diagnostic utility of creatine kinase-MB (CK-M... more Background The present study aimed to evaluate the diagnostic utility of creatine kinase-MB (CK-MB), hepcidin (HEPC), phospholipase A2 group IIA (PLa2G2A), and myosin-binding protein C (MYBPC1) for tuberculosis (TB). These four biomarkers are differentially regulated between quiescent Mycobacterium tuberculosis (Mtb) infected individuals (non-progressors to TB disease) and Mtb-infected TB disease progressors 6 months before the onset of symptoms. Methods We enrolled samples from patients experiencing moderate-to-severe pulmonary infections diseases including 23 TB cases confirmed by smear microscopy and culture, and 34 TB-negative cases. For each participant, the serum levels of the four biomarkers were measured using ELISA. Results The levels of CK-MB and HEPC were significantly reduced in patients with active TB disease. CK-MB median level was 2045 pg/ml (1455–4000 pg/ml) in active TB cases and 3245 pg/ml (1645–4000 pg/ml) in non-TB pulmonary diseases. Using the receiver operating...

Research paper thumbnail of Outcomes of severe malaria and its clinical features in Gabonese children

Frontiers in Tropical Diseases

BackgroundMalaria remains one of the deadliest diseases in the tropic. Its severe form represents... more BackgroundMalaria remains one of the deadliest diseases in the tropic. Its severe form represents a major public health concern in sub-Saharan Africa. The study aimed to describe and analyze clinical features and outcomes of severe malaria in children from Libreville.MethodsMedical records (March 2018- to December 2019) from the emergency ward of the “Mother and Child University Hospital” were analyzed. Children hospitalized for malaria who met one or more criteria of the severe form rating according to the WHO guideline were included in the study.ResultsOne hundred thirty-four children (134) children were included in the study. All children were anemic with 44% of children showing severe anemia. Thirty-three percent (33%) of admitted children were comatose or agonizing. The most frequent form of severe malaria was cerebral malaria with 101 cases (75.4%). The death rate was 18.6% (25/134). Twenty-one (21) children (84% of the deceased) died within the first 48 hours of hospitalizati...

Research paper thumbnail of Malaria beyond its predominant endemic regions: Emerging threat or sporadic events?

Research paper thumbnail of The evolving SARS-CoV-2 epidemic in Africa: Insights from rapidly expanding genomic surveillance

Investment in Africa over the past year with regards to SARS-CoV-2 genotyping has led to a massiv... more Investment in Africa over the past year with regards to SARS-CoV-2 genotyping has led to a massive increase in the number of sequences, exceeding 100,000 genomes generated to track the pandemic on the continent. Our results show an increase in the number of African countries able to sequence within their own borders, coupled with a decrease in sequencing turnaround time. Findings from this genomic surveillance underscores the heterogeneous nature of the pandemic but we observe repeated dissemination of SARS-CoV-2 variants within the continent. Sustained investment for genomic surveillance in Africa is needed as the virus continues to evolve, particularly in the low vaccination landscape. These investments are very crucial for preparedness and response for future pathogen outbreaks.One-Sentence SummaryExpanding Africa SARS-CoV-2 sequencing capacity in a fast evolving pandemic.

Research paper thumbnail of Prostate malignant tumor and benign prostatic hyperplasia microenvironments in black African men: Limited infiltration of <scp>CD8</scp>+ T lymphocytes, <scp>NK</scp>‐cells, and high frequency of <scp>CD73</scp>+ stromal cells

Cancer reports, Apr 24, 2023

Research paper thumbnail of Phytochemical screening, antioxidant and antimicrobial potential of stem barks of Coula edulis Baill. Pseudospondias longifolia Engl. and Carapa klaineana Pierre. from Gabon

Asian Pacific Journal of Tropical Disease, Jul 1, 2016

Objective To evaluate the phytochemical constituents, antioxidant and antimicrobial potential of ... more Objective To evaluate the phytochemical constituents, antioxidant and antimicrobial potential of water-acetone, water-ethanol and water extracts of Coula edulis (C. edulis), Pseudospondia longifolia (P. longifolia) and Carapa klaineana (C. klaineana).

Research paper thumbnail of Molecular markers of infectious diseases

DOAJ (DOAJ: Directory of Open Access Journals), 2009

Research paper thumbnail of Corrigendum: Microbiology laboratories involved in disease and antimicrobial resistance surveillance: Strengths and challenges of the central African states

African Journal of Laboratory Medicine, May 9, 2023

Research paper thumbnail of Higher IL-8 Response to &lt;i&gt;Mycobacterium tuberculosis&lt;/i&gt; Antigens in Women above 40 Years

Journal of tuberculosis research, 2021

Objective: Circulating levels of sex hormones vary with age. Moreover, there is emerging evidence... more Objective: Circulating levels of sex hormones vary with age. Moreover, there is emerging evidence supporting that sex hormones have an influence on the immune response of women. Here, we investigated age-associated levels of sex hormones and Mycobacterium tuberculosis (Mtb) specific cytokines response in women. Design: Using immunoassay methods, we have measured and compared secretion levels of E2, P4 and Mtb specific secretion of 11 cytokines including Granulocyte-macrophage colony-stimulating factor (GM-CSF), Interferon gamma (IFN-γ), Interleukin 1 beta (IL-1β), IL-10, IL-12 (p70), IL-2, IL-4, IL-5, IL-6, IL-8, and Tumor necrosis factor (TNF-α) in forty-two (42) HIV-negative females. Results: Estradiol (E2) and progesterone (P4) levels were significantly higher in younger women irrespective of their LTB status (p < [0.0001-0.05]). Mtb IL-8 specific response was significantly higher in women above 40 years old than in women under 40 years old. Conclusion: In premenopausal women, there is an increase in the pro-inflammatory cytokine IL-8 secretion in response to Mtb-antigen. This observation suggests an underlying link between the pro-inflammatory cytokine and age associated hormonal changes, which may have implications on the course of tuberculosis infection women.

Research paper thumbnail of Allergen sensitization and polysensitization pattern of adults and children in an urban Sub-Saharan African setting (Libreville, Gabon)

Journal of Allergy and Clinical Immunology: Global

Research paper thumbnail of Microbiology laboratories involved in disease and antimicrobial resistance surveillance: Strengths and challenges of the central African states

African Journal of Laboratory Medicine

Table 1. Country scores for veterinary laboratory capacity in the ECCAS. Attributes of evaluation... more Table 1. Country scores for veterinary laboratory capacity in the ECCAS. Attributes of evaluation of the performance of veterinary services Countries with available PVS evaluation reports, year of evaluation Burundi, 2017 4 Cameroon,

Research paper thumbnail of HIV-exposed uninfected compared with unexposed infants show the presence of leucocytes, lower lactoferrin levels and antimicrobial-resistant micro-organisms in the stool

Paediatrics and International Child Health, 2019

Background: HIV-exposed uninfected (HEU)-infants have been shown to be particularly vulnerable to... more Background: HIV-exposed uninfected (HEU)-infants have been shown to be particularly vulnerable to infections. In this population, disturbance of the gut micro-environment might increase their susceptibility to enteric diseases and even favour the translocation of bacteria in the bloodstream. Methods: The gastro-intestinal micro-environment was explored in 22 HEU infants and 16 HIV-unexposed (HU) infants aged 6-24 weeks. Faecal leucocytes, firmicutes (gram-positive bacteria) and gracilicutes (gram-negative bacteria) were assessed by cytology. Faecal lactoferrin and sIgA were measured by ELISA. The spectrum of microorganisms in infants' stool was analysed by culturing. Results: HEU infants were 14 times more likely to have leucocytes in their stool than HU infants (p < 0.005). The lactoferrin level was significantly lower in HEU infants than in HU infants (p = 0.02). Potentially pathogenic bacteria such as Escherichia coli were more prevalent in HEU than in HU infants (64% vs 23.5%). Also, E. coli strains resistant to key antibiotics including co-trimoxazole, β-lactam (cephalosporins included) and tetraclines were observed in some HEU infants. Conclusion: HEU infants are more likely to present an inflamed digestive tract as highlighted by the presence of leucocytes. In addition, there is a real risk of colonisation of HEU infants' microbiota by resistant microorganisms .

Research paper thumbnail of Genital Mycoplasma infections and their resistance phenotypes in an African setting

European Journal of Clinical Microbiology & Infectious Diseases, 2015

We investigated the antimicrobial susceptibilities of mycoplasmas in Gabonese men and women. A to... more We investigated the antimicrobial susceptibilities of mycoplasmas in Gabonese men and women. A total of 1,332 men and women were included in the study. Sperm, urine, ureteral or vaginal swabs were collected from the subjects. Mycoplasmas identification and antimicrobial susceptibility to azithromycin, clarithromycin, erythromycin, josamycin, pristinamycin, doxycycline, tetracycline, ofloxacin and ciprofloxacin were tested using the Mycoplasma IST 2 kit. 794 subjects were positive for Mycoplasma. Respectively, 1.6 % and 82.24 % of subjects were singly infected with M. hominis and Ureaplasma urealyticum and 15.87 % had a mixed infection. M. hominis isolates were resistant to erythromycin and had an intermediate (I) to resistant (R) profile to azithromycin and clarithromycin. 84.6 % of M. hominis strains were sensitive (S) to josamycin and pristinamycin. 30.8 % and 92.3 % of M. hominis strains were sensitive to tetracycline and doxycycline, respectively. 76.9 and 84.6 % of M. hominis isolates were sensitive to ciprofloxacin and ofloxacin, respectively. The sensitivity rates of U. urealyticum strains were 45.23 %, 47.7 %, 63.84 %, 90.8 % and 92 % for azithromycin, erythromycin, clarithromycin, pristinamycin and josamycin, respectively. U. urealyticum strains showed 62.2 % and 79.7 % sensitivity to tetracycline and doxycycline, respectively. The resistance rates to azithromycin, clarithromycin and erythromycin for samples with mixed infection were 72.8 %, 84.7 % and 85.6 %, respectively. Josamycin and pristinamycin were 81.5 % effective on samples with mixed infection. The sensitivity rates of samples with mixed infection to tetracycline, doxycycline, ciprofloxacin and ofloxacin were 32 %, 69.6 %, 8.9 % and 18.5 %, respectively. Sub-Saharan Africa needs to use antibiotics rationally, as falling to do so would compromise the management of infectious diseases.

Research paper thumbnail of Phytochemical screening and cytotoxicity studies of Chrysophyllum pruniforme Pierre ex Engl. barks

Pharmacognosy Research, 2013

Research paper thumbnail of Use of GeneXpert Remnants for Drug Resistance Profiling and Molecular Epidemiology of Tuberculosis in Libreville, Gabon

Journal of clinical microbiology, Jul 1, 2017

Multidrug-resistant (MDR) and extensively drug resistant (XDR) strains of Mycobacterium tuberculo... more Multidrug-resistant (MDR) and extensively drug resistant (XDR) strains of Mycobacterium tuberculosis pose major problems for global health. The GeneXpert MTB/RIF (Xpert) assay rapidly detects resistance to rifampin (RIF(r)), but for detection of the additional resistance that defines MDR-TB (MDR tuberculosis) and XDR-TB, and for molecular epidemiology, specimen cultures and a biosafe infrastructure are generally required. We sought to determine whether the remnants of sputa prepared for the Xpert assay could be used directly to find mutations associated with drug resistance and to study molecular epidemiology, thus providing precise characterization of MDR-TB cases in countries lacking biosafety level 3 (BSL3) facilities for M. tuberculosis cultures. After sputa were processed and run on the Xpert instrument, the leftovers of the samples prepared for the Xpert assay were used for PCR amplification and sequencing or for a line probe assay to detect mutations associated with resistanc...

Research paper thumbnail of Vitamin D2 versus vitamin D3 as a risk factor in compromised bone health

The Moldovan Medical Journal

Background: Vitamin D plays an important role in the prevention of many diseases. More than 1 bil... more Background: Vitamin D plays an important role in the prevention of many diseases. More than 1 billion people worldwide suffer from vitamin D deficiency. Vitamin D deficiency can contribute to the development of 16 types of cancer (breast, colon, prostate, etc.), cardiovascular diseases, stroke, autoimmune diseases, periodontal pathologies, transplant failure in endo-alveolar surgery, etc. There are several risk factors that would prevent the achievement of treatment objectives. The national protocol for deficiency rickets prevention privileges vitamin D2 versus vitamin D3, which creates a medical risk factor compromising oral health in both children and adults. The article provides sufficient arguments in favour of vitamin D3 vs vitamin D2 prescription for prophylactic and treatment purposes. Conclusions: Considering that vitamin D deficiency is currently a global public health problem, it can be proposed to declare vitamin D deficit/deficiency a priority public health problem at th...

Research paper thumbnail of Emergence of B.1.1.318 SARS-CoV-2 viral lineage and high incidence of alpha B.1.1.7 variant of concern in the Republic of Gabon

International Journal of Infectious Diseases, 2021

Objective: Variants of concern (VOCs) associated with relatively high transmissibility appear to ... more Objective: Variants of concern (VOCs) associated with relatively high transmissibility appear to be rapidly spreading in Gabon. Therefore, it is imperative to understand the distribution of several VOCs in the population, which could have implications for transmissibility and vaccine efficacy. Methods: Between February and May 2021, SARS-CoV-2 genomes were sequenced using the Oxford nanopore MinION method and the respective genome diversity was elucidated. Phylogenetic analysis was performed and genomes were classified using pangolin lineages. Results: The results highlighted an increase (46%) in the alpha VOC (B.1.1.7) in the Gabonese population over the study period. In addition, an increase (31%) in the B.1.1.318 lineage, which is associated with high transmission and impaired vaccine efficacy (D614G + E484K + Y144del), was detected. Conclusion: With the second wave ongoing, these findings highlight the need for surveillance of the SARS-CoV-2 genome in the Republic of Gabon and should provide useful guidance to policymakers in selecting an appropriate vaccine for this population.

Research paper thumbnail of Purifying Selection in Human Immunodeficiency Virus-1 pol Gene in Perinatally Human Immunodeficiency Virus-1-Infected Children Harboring Discordant Immunological Response and Virological Nonresponse to Long-Term Antiretroviral Therapy

Journal of Clinical Medicine Research, 2020

Background: Biological monitoring of antiretroviral treatment (ART) in human immunodeficiency vir... more Background: Biological monitoring of antiretroviral treatment (ART) in human immunodeficiency virus (HIV)-infected pediatric population remains challenging. The aim of the present study was to assess the long-term HIV-1 genetic diversity in pol gene in HIV-1-infected children in virological failure under antiretroviral regimen adapted according to the successive World Health Organization (WHO) guidelines for resource-constrained settings. Methods: HIV-1 diversity in pol gene was assessed in HIV-1-infected children and adolescents born from HIV-infected mothers (median age at follow-up: 13.8 years) in virological failure (VF +) despite longterm regimen recommended by the WHO. The numbers of nonsynonymous substitutions per potential nonsynonymous site (dN) and of synonymous substitutions at potential synonymous sites (dS) in HIV-1 pol gene and the dN/dS ratios were used to estimate the selective pressure on circulating HIV-1. Results: The immunological responses to ART basically corresponded to: 1) Full therapeutic failure with immunological (I-) and virological nonresponses in one-quarter (24.6%) of study children ((I-, VF +) subgroup); 2) Discordant immunovirological responses with paradoxical high CD4 T cell counts (I +) and high HIV-1 RNA load in the remaining cohort patients (75.4%) ((I + , VF +) subgroup). The mean dS was 1.8-fold higher in (I + , VF +) than (I-, VF +) subgroup (25.9 ± 18.4 vs. 14.3 ± 10.8). In the (I + , VF +) subgroup, the mean dS was 1.6-fold higher than the mean dN. Finally, the mean dN/dS ratio was 2.1-fold lower in (I + , VF +) than (I-, VF +) subgroup (0.6 ± 0.3 vs. 1.3 ± 0.7), indicating purifying selection in the immunovirological discordant (I + , VF +) subgroup and positive selection in the immunovirological failure (I-, VF +) subgroup. Conclusions: Children and adolescents in immunovirological therapeutic failure harbor positive selection of HIV-1 strains favoring diversifying in pol-encoded amino acids. In contrast, children with persistent discordant immunovirological responses show accumulation of mutations and purifying selection in pol gene sequences, indicating limited genetic evolution and likely suggesting genetic adaptation of viruses to host functional constraints.

Research paper thumbnail of Distinct serum biosignatures are associated with different tuberculosis treatment outcomes

Tuberculosis, 2019

Distinct serum biosignatures are associated with different tuberculosis treatment outcomes. Tuber... more Distinct serum biosignatures are associated with different tuberculosis treatment outcomes. Tuberculosis, 118.

Research paper thumbnail of Changes of C-reactive protein and Procalcitonin after four weeks of treatment in patients with pulmonary TB

Journal of Clinical Tuberculosis and Other Mycobacterial Diseases

Research paper thumbnail of Creatine kinase-(MB) and hepcidin as candidate biomarkers for early diagnosis of pulmonary tuberculosis: a proof-of-concept study in Lambaréné, Gabon

Infection, 2022

Background The present study aimed to evaluate the diagnostic utility of creatine kinase-MB (CK-M... more Background The present study aimed to evaluate the diagnostic utility of creatine kinase-MB (CK-MB), hepcidin (HEPC), phospholipase A2 group IIA (PLa2G2A), and myosin-binding protein C (MYBPC1) for tuberculosis (TB). These four biomarkers are differentially regulated between quiescent Mycobacterium tuberculosis (Mtb) infected individuals (non-progressors to TB disease) and Mtb-infected TB disease progressors 6 months before the onset of symptoms. Methods We enrolled samples from patients experiencing moderate-to-severe pulmonary infections diseases including 23 TB cases confirmed by smear microscopy and culture, and 34 TB-negative cases. For each participant, the serum levels of the four biomarkers were measured using ELISA. Results The levels of CK-MB and HEPC were significantly reduced in patients with active TB disease. CK-MB median level was 2045 pg/ml (1455–4000 pg/ml) in active TB cases and 3245 pg/ml (1645–4000 pg/ml) in non-TB pulmonary diseases. Using the receiver operating...

Research paper thumbnail of Outcomes of severe malaria and its clinical features in Gabonese children

Frontiers in Tropical Diseases

BackgroundMalaria remains one of the deadliest diseases in the tropic. Its severe form represents... more BackgroundMalaria remains one of the deadliest diseases in the tropic. Its severe form represents a major public health concern in sub-Saharan Africa. The study aimed to describe and analyze clinical features and outcomes of severe malaria in children from Libreville.MethodsMedical records (March 2018- to December 2019) from the emergency ward of the “Mother and Child University Hospital” were analyzed. Children hospitalized for malaria who met one or more criteria of the severe form rating according to the WHO guideline were included in the study.ResultsOne hundred thirty-four children (134) children were included in the study. All children were anemic with 44% of children showing severe anemia. Thirty-three percent (33%) of admitted children were comatose or agonizing. The most frequent form of severe malaria was cerebral malaria with 101 cases (75.4%). The death rate was 18.6% (25/134). Twenty-one (21) children (84% of the deceased) died within the first 48 hours of hospitalizati...

Research paper thumbnail of Malaria beyond its predominant endemic regions: Emerging threat or sporadic events?

Research paper thumbnail of The evolving SARS-CoV-2 epidemic in Africa: Insights from rapidly expanding genomic surveillance

Investment in Africa over the past year with regards to SARS-CoV-2 genotyping has led to a massiv... more Investment in Africa over the past year with regards to SARS-CoV-2 genotyping has led to a massive increase in the number of sequences, exceeding 100,000 genomes generated to track the pandemic on the continent. Our results show an increase in the number of African countries able to sequence within their own borders, coupled with a decrease in sequencing turnaround time. Findings from this genomic surveillance underscores the heterogeneous nature of the pandemic but we observe repeated dissemination of SARS-CoV-2 variants within the continent. Sustained investment for genomic surveillance in Africa is needed as the virus continues to evolve, particularly in the low vaccination landscape. These investments are very crucial for preparedness and response for future pathogen outbreaks.One-Sentence SummaryExpanding Africa SARS-CoV-2 sequencing capacity in a fast evolving pandemic.