Publications by authors named "Robert Onsare"

Background: Invasive non-typhoidal (iNTS) disease continues to be a major public health problem, especially in sub-Saharan Africa (SSA), where incidence rates are 227 cases [range 152-341] per 100,000 populations. Populations at risk of iNTS include adults with human immunodeficiency virus (HIV) infection, malnourished children, and those with recent malaria or sickle-cell anaemia (SCA). In Kenya, iNTS disease is particularly a major challenge in poor informal settlements, with infants and young children less than 5 years of age being the most affected.

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Antimicrobial resistance (AMR) is a global threat and is thought to be acute in low-and middle-income country (LMIC) settings, including in Kenya, but there is limited unbiased surveillance that can provide reliable estimates of its burden. Current efforts to build capacity for microbiology testing in Kenya are unlikely to result in systematic routine microbiological testing in the near term. Therefore, there is little prospect for microbiological support to inform clinical diagnoses nor for indicating the burden of AMR and for guiding empirical choice of antibiotics.

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Blood and bone marrow cultures are considered the gold standard for the diagnosis of typhoid, but these methods require infrastructure and skilled staff that are not always available in low- and middle-income countries where typhoid is endemic. The objective of the study is to evaluate the sensitivity and specificity of nine commercially available Salmonella Typhi rapid diagnostic tests (RDTs) using blood culture as a reference standard in a multicenter study. This was a prospective and retrospective multicenter diagnostic accuracy study conducted in two geographically distant areas where typhoid is endemic (Pakistan and Kenya; NCT04801602).

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Introduction: Although antimicrobials have traditionally been used to treat infections and improve health outcomes, resistance to commonly used antimicrobials has posed a major challenge. An estimated 700,000 deaths occur globally every year as a result of infections caused by antimicrobial-resistant pathogens. Antimicrobial resistance (AMR) also contributes directly to the decline in the global economy.

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Article Synopsis
  • Understanding the dynamics of typhoid infection and carriage is essential for developing effective prevention strategies in endemic areas like Nairobi, Kenya.
  • A study involving 4,670 cases and 8,549 controls identified a carriage frequency of 1% among children under 16, with most cases linked to multidrug-resistant strains of Salmonella Typhi.
  • The results suggest that asymptomatic carriers significantly contribute to the spread of typhoid in the community, highlighting the need for targeted interventions.
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  • - Invasive Non-typhoidal Salmonella (iNTS) disease poses a significant health risk in Sub-Saharan Africa, with high mortality rates in Kenya due to delayed treatment, primarily caused by two common serotypes: S. Typhimurium and S. Enteritidis.
  • - A study in Nairobi's Mukuru informal settlement analyzed blood and fecal samples, revealing 133 S. Typhimurium and 120 S. Enteritidis isolates, highlighting distinct lineages and a common source of infection among cases and controls.
  • - The finding of high multidrug resistance, including resistance to critical antibiotics, coupled with a concerning rate of asymptomatic carriers, underscores the need for preventive measures, like vaccination, especially
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Article Synopsis
  • The study focuses on the high rates of typhoid fever and non-typhoidal salmonellosis in a poor-resource area in Nairobi, Kenya, from 2013 to 2017, aiming to assess the disease burden and identify risk factors.
  • A census of 150,000 in the Mukuru informal settlement collected data on socioeconomic and healthcare access, while also sampling children under 16 for Salmonella infections.
  • Results showed 1.3% of children had infections from Non-Typhoidal Salmonella and 1.4% had Salmonella Typhi, with significant links to domestic animal rearing, water storage practices, and sanitation methods.
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Bacteriophages are a sustainable alternative to control pathogenic bacteria in the post-antibiotic era. Despite promising reports, there are still obstacles to phage use, notably titer stability and transport-associated expenses for applications in food and agriculture. In this study, we have developed a lyophilization approach to maintain phage titers, ensure efficacy and reduce transport costs of bacteriophages.

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Background: Salmonella infections cause a disproportionately high number of deaths in Africa, especially among poor urban populations. The increasing level of multidrug-resistant (MDR) infections is a major cause of concern in these settings where alternative effective treatment is unavailable. Other options for management of these infections must be sought.

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Background: The burden of typhoid in sub-Saharan African (SSA) countries has been difficult to estimate, in part, due to suboptimal laboratory diagnostics. However, surveillance blood cultures at two sites in Nigeria have identified typhoid associated with Salmonella enterica serovar Typhi (S. Typhi) as an important cause of bacteremia in children.

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An epidemiological paradox surrounds Salmonella enterica serovar Enteritidis. In high-income settings, it has been responsible for an epidemic of poultry-associated, self-limiting enterocolitis, whereas in sub-Saharan Africa it is a major cause of invasive nontyphoidal Salmonella disease, associated with high case fatality. By whole-genome sequence analysis of 675 isolates of S.

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Article Synopsis
  • Invasive nontyphoidal Salmonella (iNTS) disease is a serious health issue in Kenya, particularly affecting adults with HIV and young children with coexisting conditions like malaria or severe malnutrition, with incidence rates among children ranging from 166 to 568 cases per 100,000 annually.
  • A study analyzed 192 NTS isolates (mostly Salmonella Typhimurium and Enteritidis) from pediatric patients over several years, revealing high rates of multidrug resistance, especially in the ST313 strain linked to severe illness.
  • The emergence of ceftriaxone-resistant strains complicates treatment, as iNTS symptoms often mimic other febrile illnesses, highlighting the challenge of effective management in areas where
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Article Synopsis
  • Multidrug-resistant (MDR) typhoid, caused by a specific lineage of Salmonella called H58, has spread rapidly across Asia and Africa over the past 30 years, posing a significant global health threat.
  • The research reveals that H58 is displacing antibiotic-sensitive strains and is linked to numerous transmissions, including ongoing MDR epidemics within Africa.
  • The study highlights the genetic characteristics of the H58 lineage, providing insights that can help manage MDR typhoid and similar antibiotic-resistant bacteria globally.
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Background: Nontyphoidal Salmonellae (NTS) cause a large burden of invasive and gastrointestinal disease among young children in sub-Saharan Africa. No vaccine is currently available. Previous reports indicate the importance of the O-antigen of Salmonella lipopolysaccharide for virulence and resistance to antibody-mediated killing.

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