Atunga Nyachieo

Dr. Atunga Nyachieo

orcid

Research Focus & Metrics

Academic Career Length

18Years (2009-Present)

(Calculated once Scilit publication data is synced: current year − year of first publication + 1)

Representative Publications

View All Publications
23 January 2020 in Viruses
Verified
Journal Article
Open access
PDF file
JOJoseph Michael Ochieng Oduor
Joseph Michael Ochieng Oduor
EKErmir Kadija
Ermir Kadija
ANAtunga Nyachieo
Atunga Nyachieo
Marianne MureithiMarianne Mureithi
Marianne Mureithi
Mikael SkurnikMikael Skurnik
Mikael Skurnik
Emergence of antibiotic-resistant bacteria is a serious threat to the public health. This is also true for Staphylococcus aureus and other staphylococci. Staphylococcus phages Stab20, Stab21, Stab22, and Stab23, were isolated in Albania. Based on genomic and phylogenetic analysis, they were classified to genus Kayvirus of the subfamily Twortvirinae. In this work, we describe the in-depth characterization of the phages that electron microscopy confirmed to be myoviruses. These phages showed tolerance to pH range of 5.4 to 9.4, to maximum UV radiation energy of 25 µJ/cm2, to temperatures up to 45 °C, and to ethanol concentrations up to 25%, and complete resistance to chloroform. The adsorption rate constants of the phages ranged between 1.0 × 10−9 mL/min and 4.7 × 10−9 mL/min, and the burst size was from 42 to 130 plaque-forming units. The phages Stab20, 21, 22, and 23, originally isolated using Staphylococcus xylosus as a host, demonstrated varied host ranges among different Staphylococcus strains suggesting that they could be included in cocktail formulations for therapeutic or bio-control purpose. Phage particle proteomes, consisting on average of ca 60–70 gene products, revealed, in addition to straight-forward structural proteins, also the presence of enzymes such DNA polymerase, helicases, recombinases, exonucleases, and RNA ligase polymer. They are likely to be injected into the bacteria along with the genomic DNA to take over the host metabolism as soon as possible after infection.

13 January 2017 in Tropical Diseases, Travel Medicine and Vaccines
Verified
Journal Article
Open access
PDF file
DNDiana Nyabundi
Diana Nyabundi
NONyamongo Onkoba
Nyamongo Onkoba
RKRinter Kimathi
Rinter Kimathi
ANAtunga Nyachieo
Atunga Nyachieo
GJGerald Juma
Gerald Juma
JKJoseph Kamau
Joseph Kamau
Salmonella has significant public health implications causing food borne and zoonotic diseases in humans. Treatment of infections due to Salmonella is becoming difficult due to emergence of drug resistant strains. There is therefore need to characterize the circulating non-typhoidal Salmonella (NTS) serovars in domestic animals and animal products in Kenya as well as determine their antibiotic resistance profiles. A total of 740 fecal samples were collected from cows (n = 150), pigs (n = 182), chicken (n = 191) and chicken eggs (n = 217) from various markets and abattoirs in Nairobi. The prevalence of NTS serovars using culture techniques and biochemical tests, antimicrobial sensitivity testing using disc diffusion method of the commonly prescribed antibiotics and phylogenetic relationships using 16S rRNA were determined. The results showed that the overall prevalence of Salmonella was 3.8, 3.6, 5.9 and 2.6% for pigs, chicken, eggs and cows respectively. Two serovars were isolated S. Typhimurium (85%) and S. Enteritidis (15%) and these two serovars formed distinct clades on the phylogenetic tree. Forty percent of the isolates were resistant to one or more antibiotics. The isolation of Salmonella Typhimurium and Salmonella Enteritidis that are resistant to commonly used antibiotics from seemingly healthy animals and animal products poses a significant public health threat. This points to the need for regular surveillance to be carried out and the chain of transmission should be viewed to ascertain sources of contamination.

11 August 2022 in African Journal of Laboratory Medicine
Verified
Journal Article
Open access
PDF file
Ivy J. MutaiIvy J. Mutai
Ivy J. Mutai
AJAngela A. Juma
Angela A. Juma
MIMartin I. Inyimili
Martin I. Inyimili
ANAtunga Nyachieo
Atunga Nyachieo
ANAnthony K. Nyamache
Anthony K. Nyamache
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 67.0% of bacterial strains; the least potent phage lysed 27.0%.Conclusion: This study reveals the existence of therapeutic phages in Kenya that are potent enough for treatment of multi-drug resistant E. cloacae.

SBSadie Bergen
Sadie Bergen
DMDoris Murimi
Doris Murimi
CGCaitlin Gruer
Caitlin Gruer
GMGibson Munene
Gibson Munene
ANAtunga Nyachieo
Atunga Nyachieo
MSMarni Sommer
Marni Sommer
Despite the high global prevalence of endometriosis, little is known about the experiences of women living with the disease in low- and middle-income contexts, including in Kenya and other countries across sub-Saharan Africa. This study captures the perspectives and recommendations of Kenyan women living with endometriosis through written narratives about the impact of the disease on their daily lives and their journeys through diagnosis and treatment. Thirty-seven women between the ages of 22 and 48 were recruited from an endometriosis support group in Nairobi and Kiambu, Kenya (February–March of 2022) in partnership with the Endo Sisters East Africa Foundation. Narrative data (written anonymous stories submitted through Qualtrics) were analyzed using a deductive thematic analysis methodology. Their stories revealed three themes related to their shared experiences with endometriosis: (1) stigma and disruption to quality of life, (2) barriers to acceptable healthcare, and (3) reliance on self-efficacy and social support to cope with the disease. These findings demonstrate a clear need for improved social awareness of endometriosis in Kenya and the establishment of clear, effective, and supportive pathways, with trained, geographically and financially accessible health care providers, for endometriosis diagnosis and treatment.

1 February 2016 in African Journal of Laboratory Medicine
Verified
Journal Article
Open access
JOJoseph Michael Ochieng Oduor
Joseph Michael Ochieng Oduor
NONyamongo Onkoba
Nyamongo Onkoba
FMFredrick Maloba
Fredrick Maloba
ANAtunga Nyachieo
Atunga Nyachieo
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 MDRSA or phage (108 CFU/mL) and treated after 72 hours with a single dose of clindamycin (8 mg/kg/bwt) or 108 PFU/mL of phage or a combination therapy (clindamycin and phage). The efficacy of phage, clindamycin or clindamycin with phage combination was determined using resolution of lung pathology and bacterial load in lung homogenates.Results: The viable MDRSA count was 0.5 ± 0.2 log10 CFU/gm in the phage-treated group, 4.4 ± 0.2 log10 CFU/gm in the clindamycin-treated group and 4.0 ± 0.2 log10 CFU/gm in the combination-treated group. The efficacy of phage therapy was significantly different from other therapeutic modes (p = 0 < 0.0001). Histology showed that the mice treated with phage did not develop pneumonia.Conclusion: Phage therapy is effective against haematogenous MDRSA infection. Thus, it can be explored as an alternative treatment method.

30 April 2025 in Proceedings Of The Royal Society B-Biological Sciences
Verified
Journal Article
Open access
AMAkiko Matsumoto-Oda
Akiko Matsumoto-Oda
DUDaisuke Utsumi
Daisuke Utsumi
Kenzo TakahashiKenzo Takahashi
Kenzo Takahashi
SHSatoshi Hirata
Satoshi Hirata
ANAtunga Nyachieo
Atunga Nyachieo
MRMichel Raymond
Michel Raymond
Injuries, which affect survival and biological functioning, are common in the animal kingdom. This study systematically investigated whether the slow wound healing observed in humans is a unique characteristic within the primate order. First, we found no significant difference in wound-healing rates between baboons under experimental conditions and those in their natural environment (0.613 mm d −1 ). Second, comparisons among four non-human primates (velvet monkeys, Sykes’ monkeys, baboons and chimpanzees) revealed no significant differences in wound-healing rates. Furthermore, these rates showed no significant differences compared to those observed in rodents, suggesting a potential commonality in wound-healing rates across diverse animal species. In contrast, human wound-healing rates were found to be markedly slower (0.25 mm d −1 ), approximately three times slower than those observed in non-human primates. This finding indicates that the slow wound healing observed in humans is not a common characteristic among primate order and highlights the possibility of evolutionary adaptations in humans. Understanding these inter-species differences in wound-healing rates may provide valuable insights into the evolutionary implications of wound healing. This study also underscores the need for further research into the biological processes underlying wound healing in various species.