Dr. Atunga Nyachieo, PhD | KU Leuven (original) (raw)

Papers by Dr. Atunga Nyachieo, PhD

Journal of Tropical Pediatrics, 2008

Rotavirus gastroenteritis still remains a major cause of morbidity and mortality among young chil... more Rotavirus gastroenteritis still remains a major cause of morbidity and mortality among young children in developing countries, with »150 000-200 000 deaths occurring annually in sub-Saharan Africa. We reviewed papers published over the last 30 years on the epidemiology of rotavirus diarrhoea among the hospitalized and outpatient children in Kenya. The analysis shows rotavirus prevalence of 6-56% with diarrhoea occurring throughout the year and generally exhibiting distinct peaks during the dry months. Among the common genotype, G1 was the most predominant up to the year 2002 but more recently there has been an emergence of genotype G9 as the most predominant genotype and to a less extent G8. It is important to continue rotavirus surveillance in Kenya to determine accurately the burden of rotavirus disease and the emerging new genotypes. This will assist policy makers in decision making on rotavirus vaccine introduction and determining the impact of the vaccine.

African Journal of Laboratory Medicine

Background: The development of alternative control measures, such as phage therapy or adjunctive ... more Background: The development of alternative control measures, such as phage therapy or adjunctive therapy, is urgently needed to manage the dissemination of carbapenemase-producing Klebsiella pneumoniae.Objective: This study aimed to evaluate the therapeutic potential of formulated phage cocktails and their interaction with select antibiotics in inhibiting the growth of carbapenemase-producing K. pneumoniae clinical isolate in vitro in Kenya.Methods: The study was conducted from February 2021 to October 2021 at the Institute of Primate Research, Nairobi, Kenya. Phage cocktails were formulated based on the morphology and biological properties of precipitated Klebsiella phages. The efficacy of individual bacteriophages and phage cocktails as well as their combination with antibiotics were determined for their inhibitory activity on carbapenemase-producing K. pneumoniae (KP20).Results: The precipitated bacteriophages were members of Myoviridae, Siphoviridae and Podoviridae. Regarding th...

The Journal of Steroid Biochemistry and Molecular Biology

The Women's Review of Books, 1995

Journal of Cytology & Histology, 2013

Objective: The aim of this study is to determine the prevalence of cervical precancerous lesions ... more Objective: The aim of this study is to determine the prevalence of cervical precancerous lesions in Cameroon. Methods: A cross-sectional study for one year period has been conducted in 6 regions of Cameroon by the National Cancer control Committee and the Gynecologic and Pediatric Hospital in Yaoundé from 1/1/2009 to 12/30/2009. Results: Women were diagnosed of precancerous cervical lesions (97/2485), making the national prevalence of 3.9%, with the highest rate located in Centre, Littoral and Far North regions. The age of the affected women was 27-55 years with 67% women between 34 and 49 years old. The majority of these women had at least four pregnancies (32 %). Conclusion: The prevalence of precancerous lesions of the uterine cervix in Cameroon varies among regions depending on the existence of screening activities. Continuing effort in extending these programs in different regions will make a noticeable improvement in preventing cervical cancer.

Genome Biology and Evolution, 2019

Human skin is morphologically and physiologically different from the skin of other primates. Howe... more Human skin is morphologically and physiologically different from the skin of other primates. However, the genetic causes underlying human-specific skin characteristics remain unclear. Here, we quantitatively demonstrate that the epidermis and dermis of human skin are significantly thicker than those of three Old World monkey species. In addition, we indicate that the topography of the epidermal basement membrane zone shows a rete ridge in humans but is flat in the Old World monkey species examined. Subsequently, we comprehensively compared gene expression levels between human and nonhuman great ape skin using nextgeneration cDNA sequencing (RNA-Seq). We identified four structural protein genes associated with the epidermal basement membrane zone or elastic fibers in the dermis (COL18A1, LAMB2, CD151, and BGN) that were expressed significantly greater in humans than in nonhuman great apes, suggesting that these differences may be related to the rete ridge and rich elastic fibers present in human skin. The rete ridge may enhance the strength of adhesion between the epidermis and dermis in skin. This ridge, along with a thick epidermis and rich elastic fibers might contribute to the physical strength of human skin with a low amount of hair. To estimate transcriptional regulatory regions for COL18A1, LAMB2, CD151, and BGN, we examined conserved noncoding regions with histone modifications that can activate transcription in skin cells. Human-specific substitutions in these regions, especially those located in binding sites of transcription factors which function in skin, may alter the gene expression patterns and give rise to the human-specific adaptive skin characteristics.

African Journal of Laboratory Medicine, 2022

Background: Enterobacter cloacae causes nosocomial infections in 15% of patients in low- and midd... more Background: Enterobacter cloacae causes nosocomial infections in 15% of patients in low- and middle-income countries with emergence of carbapenem resistance. The utilisation of bacteriophages for therapeutic purposes is crucial for eradicating these resistant bacterial strains.
Objective: This study evaluated the efficacy of lytic phages on bacterial isolates of E. cloacae and determined their stability in various physicochemical conditions.
Methods: Twenty-nine lytic phages were isolated from the waste water of six informal settlements in Nairobi County, Kenya, from July 2019 to December 2020 and cross-reacted with 30 anonymised clinical isolates of E. cloacae. Six phages were then selected for physicochemical property studies. Phages were described as potent upon lysing any bacterial strain in the panel.
Results: Selected phages were stable at 4 °C – 50 °C with a 5.1% decrease in titre in four of six phages and a 1.8% increase in titre in two of six phages at 50 °C. The phages were efficient following two weeks incubation at 4 °C with optimal activity at human body temperature (37 °C) and an optimal pH of 7.5. Phages were active at 0.002 M and 0.015 M concentrations of Ca2+ ions. The efficiency of all phages decreased with increased exposure to ultraviolet light. All phages (n = 29) showed cross-reactivity against anonymised clinical isolates of E. cloacae strains (n = 30). The most potent phage lysed 67% of bacterial strains; the least potent phage lysed 27%.
Conclusion: This study reveals the existence of therapeutic phages in Kenya that are potent enough for treatment of multi-drug resistant E. cloacae.

The American Journal of Tropical Medicine and Hygiene, 2005

In vivo tests for susceptibility to antimalarial drugs require molecular methods to distinguish r... more In vivo tests for susceptibility to antimalarial drugs require molecular methods to distinguish recrudescence from new infection. The most commonly used DNA markers (merozoite surface proteins [MSPs]) are under immune selective pressure, which might lead to misclassification. We evaluated immunologically neutral microsatellite markers in blood samples collected during a drug efficacy trial in Rwanda. Fifty percent of the infections classified as recrudescent by MSP were classified as new by microsatellite markers. Reciprocally, 23.3% of infections classified as recrudescent by microsatellite markers were identified as new by MSP. In drug efficacy studies, microsatellite markers should complement MSP genotyping to distinguish a recrudescence from a new infection.

Archives of microbiology, 2021

Typhoid fever is caused by the bacteria Salmonella enterica subspecies enterica serovar Typhi (S.... more Typhoid fever is caused by the bacteria Salmonella enterica subspecies enterica serovar Typhi (S. Typhi) and remains a significant health problem in many developing countries. Lack of adequate diagnostic capabilities has contributed greatly in making typhoid fever endemic in these regions. Reliable and inexpensive diagnostic tests are needed to improve the management of this disease burden. We evaluated the ability of staA, viaB and sopE genes to detect and differentiate between the three most prevalent Salmonella spp. in Kenya (S. Typhi, S. Typhimurium and S. Enteritidis) using conventional polymerase chain reaction (PCR). The staA primers and viaB primers were found to be specific only for the different strains of S. Typhi, producing PCR products of 585 bp and 540 bp, respectively. The sopE primers was demonstrated to be specific for all Salmonella spp. producing a 465 bp PCR product with no amplification with E. coli and S. boydii bacterial strains.

American Journal of Infectious Diseases and Microbiology, 2018

Papillomaviruses (PVs) are ubiquitous highly diverse group of circular double stranded DNA viruse... more Papillomaviruses (PVs) are ubiquitous highly diverse group of circular double stranded DNA viruses. Nearly all the human papillomavirus (HPVs) that cause cancer are clustered in Alphapapillomavirus (αPV) genera and have a common ancestor. The aim of the study was to isolate and perform molecular characterization of alphapapilloma virus from male olive baboons (Papio anubis) that are maintained in a captive colony at the Institute of Primate Research, Nairobi, Kenya and establish their evolutionary relationship with known strains responsible for various species causing cervical cancer in human. Twenty (n=20) different genital swabs from sexually active male olive baboons were collected. Positive samples for αPV by nested PCR were 9/20 (45%). The nested PCR primers targeted a conserved region of L1 major capsid gene and aided in generating amplicons of 134bp. Only three amplicons with good quality bands (1C, 2C, and 4C) were further sequenced and analysed using MEGA X, Clustal W algor...

Pseudomonas aeruginosa is a pathogen of great clinical importance to both humans and animals. It ... more Pseudomonas aeruginosa is a pathogen of great clinical importance to both humans and animals. It causes pneumonia in cystic fibrosis patients, and it is responsible for the infections of blood and lungs during surgery. Increased antibiotic use has led to the emergence of multidrug-resistant strains of P. aeruginosa. Recently, phage therapy has attracted much attention as a promising alternative against the increasing antimicrobial resistance. This study determined the safety and efficacy of phage therapy against virulent P. aeruginosa in a murine model. Phage PaCIKb2 was isolated from sewage water. Morphological characterization by transmission electron microscope was done. We assessed the phages' antimicrobial effect in vitro and in biofilms, its growth kinetics, host ranges, temperature and pH stability. Therapeutic safety and efficacy were observed 24 hours post-infection with virulent P. aeruginosa in a murine model. Transmission Electron Microscopy revealed phage PaCIKb2 to belong to the family myoviridae. The phage was found to be high temperature tolerant (up to 50°C). It was active between pH ranges (5 and 11), had a latent period of 15 minutes with a burst size of 316 viral particles, and exhibited a narrow host range. After intravenous phage administration dose (2×10 9 PFU/ml) post-infection with virulent P. aeruginosa, the presence of phages in vivo and reduction of bacterial loads in mice was observed. A reduction in mice tissue inflammation suggested the effectiveness of phage PaCIKb2 phage therapy. This research gives data that supports the use of phage therapy against multidrug-resistant P. aeruginosa.

Human rotaviruses have emerged as a leading cause of acute diarrhea in children <5 years of ag... more Human rotaviruses have emerged as a leading cause of acute diarrhea in children <5 years of age worldwide. Although there are previous reports relating to various aspects of rotaviruses, there is limited data on the involvement of rotavirus infection in HIV-infected children. We therefore evaluated the importance of rotavirus infections in HIV-related diarrhea in Kenyan children. Fecal samples were collected from a total of 207 children during the period February 1999 to June 2000 and screened for HRV antigen by enzyme-linked immunosorbent assay (ELISA). Positive samples were analyzed by VP6 subgroup specificity assay, by polyacrylamide gel electrophoresis (PAGE) and reverse transcriptase/ polymerase chain reaction (RT–PCR). Fourteen percent (29/207) of the samples were positive. HIV-seropositive children with diarrhea were more likely than their counterparts without diarrhea to have rotaviruses [23.3 % (10/43) versus 2.9 % (2/70); p 0.0001]. Rotavirus strain G3P[6] was predomina...

African Journal of Laboratory Medicine, 2016

Background: Community-acquired haematogenous Staphylococcus aureus pneumonia is a rare infection,... more Background: Community-acquired haematogenous Staphylococcus aureus pneumonia is a rare infection, though it can be acquired nosocomially. Currently, antibiotics used against S. aureus pneumonia have shown reduced efficacy. Thus, there is need for an alternative therapy against multidrug-resistant S. aureus (MDRSA) strains in the community.Objective: We sought to determine the efficacy of environmentally-obtained S. aureus lytic phage against haematogenous MDRSA pneumonia in mice.Methods: Phages and MDRSA were isolated from sewage samples collected within Nairobi County, Kenya. Isolated S. aureus bacteria were screened for resistance against ceftazidime, oxacillin, vancomycin, netilmicin, gentamicin, erythromycin, trimethroprim-sulfamethoxazole and cefuroxime. Thirty BALB/c mice aged six to eight weeks were randomly assigned into three groups: the MDRSA-infection group (n = 20), the phage-infection group (n = 5) and the non-infection group (n = 5). Mice were infected with either MDRS...

The Pediatric Infectious Disease Journal, 2014

Background: The World Health Organization has recommended that rotavirus (RV) vaccines be include... more Background: The World Health Organization has recommended that rotavirus (RV) vaccines be included in all national immunization programs as part of a strategy to control RV-associated diarrheal diseases. Hospitalbased surveillance of RV infection is therefore crucial in monitoring the impact pre-and post-vaccine introduction and also to document changes in genotype distribution. This study sought to determine the RV genotypes circulating in the eastern region of Kenya before introduction of the RV vaccine. Methods: During September 2009 to August 2011, 500 stool samples were collected from children <5 years of age admitted for acute diarrhea in hospitals in the eastern region of Kenya and analyzed for the presence of group A RV using an enzyme immunoassay. G and P genotypes were determined using hemi-nested reverse transcriptase polymerase chain reaction. Results: One hundred and eighty nine out of 500 (38%) samples analyzed were positive for rotavirus. The following G types were detected: G9 (50.9%), G1 (26.8%), G8 (12.1%), G12 (3.1%), G2 (0.6%), mixed G (1.3%) and 5.1% were G nontypeable. P types detected included: P[8] (63.7%), P[4] (12.1%), P[6] (4.5%), mixed P (7.6%) and 12.1% were P nontypeable. The most dominant strain was G9P[8] (35%), followed by G1P[8] (26.8%), G8P[4] (9.6%), G12P[6] (2.5%), G9P[6] (1.9%), G9P[4] (1.3%), G8P[8] (1.3%), and G2P[4] (0.6%). Conclusions: The present study demonstrates the recurring changing genotypes of RV circulating in Kenya, with genotypes G9, G1 and G8 being the dominant strains circulating in the eastern region of Kenya between 2009 and 2011. Additionally, G12 genotype was detected for the first time in Kenya.

Gynecologic and Obstetric Investigation, 2013

The biological effects of khat (Catha edulis) on reproduction and fertility are inadequately inve... more The biological effects of khat (Catha edulis) on reproduction and fertility are inadequately investigated and controversial, hence we determined the effects of oral administration of high-dose khat on sperm parameters and male hormonal levels in olive baboons. In this study, 6 male baboons received a high dose of khat (500 g/week) during 1 month. Electroejaculation for sperm studies (concentration, motility and chromatin integrity) and plasma collection for hormonal analysis (testosterone, prolactin and cortisol) were done weekly during 1 month before and 1 month during khat administration as well as 2 weeks after the last dose of khat administration. Administration of khat extract induced a significant reduction in sperm motility (p = 0.008), sperm count (p = 0.041), sperm chromatin integrity (p = 0.0003), testosterone levels (p = 0.035) and prolactin levels (p = 0.0115), but not in cortisol levels and sperm volume (p &amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;gt; 0.05). The results suggest that high-dose khat decreases sperm quality and testosterone and hence may contribute to male infertility.

Journal of Medical Primatology, 2010

East African Medical …, 2006

Journal of Microbiology and Infectious Diseases, 2021

Objectives: Escherichia coli and some Salmonella enterica serovars are zoonotic pathogens affecti... more Objectives: Escherichia coli and some Salmonella enterica serovars are zoonotic pathogens affecting livestock and humans. These pathogens cause significant loss of productivity in livestock, severe morbidity and mortality in humans, and have high antibiotic resistance profiles. Therefore, the exploitation of lytic phages for therapeutic purposes is important for eliminating these resistant bacterial strains. Methods: Thirty-four bacterial stock isolates comprised of 23 E. coli and 11 Salmonella spp. strains were evaluated for antimicrobial susceptibility to seven antibiotics using the Kirby-Bauer disk diffusion test. The antibiotics included Ciprofloxacin, Trimethoprim-Sulphamethoxazole, Gentamycin, Imipenem, Ceftriaxone, Cefotaxime, and Ofloxacin. Twelve (12/23) E. coli and (2/11) Salmonella spp. exhibited antimicrobial resistance. Selected six (6/12) drug-resistant E. coli strains were subjected to three different phages (PA5, EHEC005, C11S1A) for efficacy and host range assay. Similarly, two (2/2) resistant Salmonella strains were exposed to one Salmonella phage A23 for efficacy and host range assay. The E. coli (C11S1A) phage, which infected most bacterial hosts, was evaluated for optimal efficiency at various pH and temperatures. Results: E. coli isolates had the highest resistance 12/23 (52%) compared to Salmonella spp. 2/11(18%) (p<0.05). Most resistance was against Trimethoprim-Sulphamethoxazole (44%) and (9%) for E. coli and Salmonella spp., respectively. Furthermore, E. coli (C11S1A) phages killed all the Escherichia coli strains, while Salmonella phage A23 only lysed the host bacteria. The E. coli (C11S1A) phages were highly efficacious at 37 0 C and pH 7.4. Conclusion: The successful isolation of novel lytic E. coli (C11S1A) phages, which killed all the E. coli strains tested, demonstrates the potential for therapeutic purposes for humans and livestock.

Human …, 2010

background: Techniques for uterus transplantation (UTx) have been developed in rodent/domestic an... more background: Techniques for uterus transplantation (UTx) have been developed in rodent/domestic animals towards future clinical introduction of UTx to treat uterine factor infertility. The aim of this study was to extend the UTx research into a non-human primate species by developing surgical techniques for uterus retrieval and transplantation in the baboon. methods: Female baboons (n ¼ 15) underwent surgery, with the initial five animals used for studies of pelvic vascular anatomy. Retrieval surgery included isolation of the ovarian veins and the uterine arteries together with the anterior branches of the internal iliacs. The uterotubal-ovarian specimen was removed, flushed and kept ex vivo for 2 h when the two arterial ends and two venous ends were anastomosed side-to-side to construct one arterial and one venous end. These were, at auto-transplantation, anastomosed end-to-side to the external iliacs and the animals (n ¼ 10) were evaluated concerning cyclicity and later by laparoscopy/laparotomy. results: The total duration of organ retrieval, backtable preparation and transplantation was around 6 h with an overall ischaemic time of the specimen of about 3 h. One animal died due to cardiomyopathy. Five out of the nine surviving animals resumed cyclicity, as a sign of reestablished ovarian function. Only two out of these five animals exhibited resumed menstruation, indicating re-established ovarian and uterine function. Laparoscopy confirmed normal-sized uteri in these two animals. conclusions: This study demonstrates the feasibility of UTx by vascular anastomosis in a non-human primate species. The low success rate demonstrates the complexity involved in UTx surgery and the need for further methodological developments.