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Visual selective attention can be achieved into bottom-up and top-down attention. Different selective attention tasks involve different attention control ways. The pop-out task requires more bottom-up attention, whereas the search task involves more top-down attention. P300, which is the positive potential generated by the brain in the latency of 300 ~ 600 ms after stimulus, reflects the processing of attention. There is no consensus on the P300 source. The aim of present study is to study the source of P300 elicited by different visual selective attention. We collected thirteen participants' P300 elicited by pop-out and search tasks with event-related potentials (ERP). We collected twenty-six participants' activation brain regions in pop-out and search tasks with functional magnetic resonance imaging (fMRI). And we analyzed the sources of P300 using the ERP and fMRI integration with high temporal resolution and high spatial resolution. ERP results indicated that the pop-out task induced larger P300 than the search task. P300 induced by the two tasks distributed at frontal and parietal lobes, with P300 induced by the pop-out task mainly at the parietal lobe and that induced by the search task mainly at the frontal lobe. Further ERP and fMRI integration analysis showed that neural difference sources of P300 were the right precentral gyrus, left superior frontal gyrus (medial orbital), left middle temporal gyrus, left rolandic operculum, right postcentral gyrus, and left angular gyrus. Our study suggests that the frontal and parietal lobes contribute to the P300 component of visual selective attention.

Abattoir workers have been identified as high-risk for livestock-associated Staphylococcus aureus carriage. This study investigated S. aureus carriage in abattoir workers in Western Kenya. Nasal swabs were collected once from participants between February-November 2012. S. aureus was isolated using bacterial culture and antibiotic susceptibility testing performed using the VITEK 2 instrument and disc diffusion methods. Isolates underwent whole genome sequencing and Multi Locus Sequence Types were derived from these data. S. aureus (n = 126) was isolated from 118/737 (16.0%) participants. Carriage was higher in HIV-positive (24/89, 27.0%) than HIV–negative participants (94/648, 14.5%; p = 0.003). There were 23 sequence types (STs) identified, and half of the isolates were ST152 (34.1%) or ST8 (15.1%). Many isolates carried the Panton-Valentine leucocidin toxin gene (42.9%). Only three isolates were methicillin resistant S. aureus (MRSA) (3/126, 2.4%) and the prevalence of MRSA carriage was 0.4% (3/737). All MRSA were ST88. Isolates from HIV-positive participants (37.0%) were more frequently resistant to sulfamethoxazole/trimethoprim compared to isolates from HIV-negative participants (6.1%; p < 0.001). Similarly, trimethoprim resistance genes were more frequently detected in isolates from HIV-positive (81.5%) compared to HIV-negative participants (60.6%; p = 0.044). S. aureus in abattoir workers were representative of major sequence types in Africa, with a high proportion being toxigenic isolates. HIV-positive individuals were more frequently colonized by antimicrobial resistant S. aureus which may be explained by prophylactic antimicrobial use.

Abattoir workers have been identified as high-risk for livestock-associated

Background: Escherichia coli is a normal inhabitant of the mammalian gut, but it also exists in a number of pathogenic forms. Diarrhoeagenic E. coli constitute pathotypes that are responsible for fatal infections in humans. Increasing contact between humans and non-human primates provides an opportunity for the transfer of potential pathogens between host species. This study aimed to characterise diarrhoeagenic E. coli pathotypes isolated from baboon faecal samples. Methods: E. coli were isolated from faecal samples of 124 animals using culture-based methods. Characterisation was achieved by isolating deoxyribonucleic acid from pure isolates and subjecting them to PCR, using specific primers for detection of virulence genes. Results: Four E. coli pathotypes including enterotoxigenic, enteropathogenic, enterohaemorrhagic and enteroinvasive were detected from baboon faecal samples. The most prevalent pathotypes were enterotoxigenic (14.5%) and atypical enteropathogenic (14.5%) in the captive and the free-ranging populations respectively. However, the observed differences in the pathotype detection were not significant (p>0.05). Enteroaggregative and diffusely adherent E. coli were not detected from any of the study samples. Conclusion: Olive baboons harbour diarrhoeagenic E. coli pathotypes; hence, the species could be a potential source of zoonotic transmission.

BackgroundGraph theory and machine learning have been shown to be effective ways of classifying different stages of Alzheimer’s disease (AD). Most previous studies have only focused on inter-subject classification with single-mode neuroimaging data. However, whether this classification can truly reflect the changes in the structure and function of the brain region in disease progression remains unverified. In the current study, we aimed to evaluate the classification framework, which combines structural Magnetic Resonance Imaging (sMRI) and resting-state functional Magnetic Resonance Imaging (rs-fMRI) metrics, to distinguish mild cognitive impairment non-converters (MCInc)/AD from MCI converters (MCIc) by using graph theory and machine learning.MethodsWith the intra-subject (MCInc vs. MCIc) and inter-subject (MCIc vs. AD) design, we employed cortical thickness features, structural brain network features, and sub-frequency (full-band, slow-4, slow-5) functional brain network features for classification. Three feature selection methods [random subset feature selection algorithm (RSFS), minimal redundancy maximal relevance (mRMR), and sparse linear regression feature selection algorithm based on stationary selection (SS-LR)] were used respectively to select discriminative features in the iterative combinations of MRI and network measures. Then support vector machine (SVM) classifier with nested cross-validation was employed for classification. We also compared the performance of multiple classifiers (Random Forest, K-nearest neighbor, Adaboost, SVM) and verified the reliability of our results by upsampling.ResultsWe found that in the classifications of MCIc vs. MCInc, and MCIc vs. AD, the proposed RSFS algorithm achieved the best accuracies (84.71, 89.80%) than the other algorithms. And the high-sensitivity brain regions found with the two classification groups were inconsistent. Specifically, in MCIc vs. MCInc, the high-sensitivity brain regions associated with both structural and functional features included frontal, temporal, caudate, entorhinal, parahippocampal, and calcarine fissure and surrounding cortex. While in MCIc vs. AD, the high-sensitivity brain regions associated only with functional features included frontal, temporal, thalamus, olfactory, and angular.ConclusionsThese results suggest that our proposed method could effectively predict the conversion of MCI to AD, and the inconsistency of specific brain regions provides a novel insight for clinical AD diagnosis.

The previous neuroimaging functional connectivity analyses have indicated that the association between the inferior frontal gyrus (IFG) and other brain regions results in better emotion regulation in reappraisal tasks. However, no study has explored the relationship between IFG-based resting-state functional connectivity (rsFC) and the dispositional use of reappraisal strategy. Therefore, the present study examined the potential associations between rsFC patterns of both left and right IFG and dispositional reappraisal use. One hundred healthy participants completed the Emotion Regulation Questionnaire (ERQ) and underwent a resting-state functional magnetic resonance imaging (fMRI) acquisition. An approach of the seed-based rsFC analysis was recruited to estimate the functional connectivity maps of bilateral IFG with other brain regions, and the reappraisal scores from the ERQ were then correlated with the functional maps. Our findings showed that IFG-based rsFC was positively correlated with dispositional reappraisal only in the range of 4 to 5.5 points [medium reappraisal group (MRG)]. Specifically, medium dispositional reappraisal was positively correlated with rsFC between left/right IFG and bilateral temporal gyrus. Besides, medium dispositional reappraisal was positively correlated with rsFC between left IFG and bilateral superior parietal lobe (SPL), middle cingulate cortex (MCC), and right insula, as well as between right IFG and dorsomedial prefrontal cortex (DMPFC) and anterior cingulate cortex (ACC). In conclusion, these results indicate that bilateral IFG plays an important role in the medium use of the reappraisal strategy.

Previous studies have shown that visuospatial working memory (VSWM) plays a key role in the encoding and processing of visuospatial information. More importantly, there is evidence suggesting the role of frontal and parietal cortical areas in VSWM and especially, the influence of the frontal cortex in regulating goal-directed behavior. However, the functional role of the right dorsolateral prefrontal cortex (rDLPFC) in visuospatial working memory is still unclear. Here, we noninvasively modulated the rDLPFC activity using continuous theta-burst stimulation (cTBS), with the vertex as the control site. Our study aimed to investigate the effects of cTBS over rDLPFC on working memory task (2- and 4-back) performance. Working memory performance was assessed at the baseline and after stimulation. We observed that the working memory performance as measured by discriminability index was impaired after cTBS over rDLPFC in 2-back task, whereas 4-back task performance was not significantly affected. More so, there was no effect on performance after cTBS over the vertex, suggesting a functional role of rDLPFC in VSWM. Our findings demonstrate the involvement of the rDLPFC in VSWM as well as the load-dependent effect of working memory performance. Taken together, our work constitutes a useful addition to the literature and underscores the effectiveness and efficiency of noninvasive brain stimulation in modulating neuro-cognitive activity.

Emotion regulation (ER) is an essential part of our daily life. To effectively regulate emotions, different types of strategies may be adopted. Although previous neuroimaging studies have shown that the frontoparietal cortex is critical for the regulation of emotions, reports about the specific brain regions involved in each strategy remain inconsistent. Therefore, the present study recruited 32 healthy participants to directly examine three typical ER strategies (distraction, reappraisal, and suppression) with an emotional regulation paradigm using functional magnetic resonance imaging (fMRI). Our results show that the three ER strategies recruited differential activation in the frontoparietal and insular cortex. Specifically, distraction evoked stronger activation in the parietal cortex, while reappraisal triggered stronger activation in most parts of the frontal cortex. Importantly, suppression predominantly recruited the left inferior frontal gyrus (IFG), while reappraisal caused more activation than suppression in bilateral medial superior frontal gyrus and IFG. Besides, functional connectivity analysis found that the connectivity between the right insular and the right IFG was negatively correlated with reappraisal effect, while that between the left insular and the left IFG was negatively correlated with suppression effect. These results suggest that the successful implementation of distraction, reappraisal, and suppression specifically employ different parts of the frontoparietal network. Overall, our findings may have potential implications for clinical practice by providing specific neural targets for clinical intervention.

Background: Invasive Non-typhoidal Salmonella (iNTS) disease continues to be a major public health problem, especially in sub Saharan Africa where incidence rates are 227 cases [range 152-341] per 100,000 population. Populations at risk of iNTS include adults with HIV infection, malnourished children, those with recent malaria or sickle-cell anaemia (SCA). Individuals with SCA are at an increased risk of invasive bacterial infections with the proportion of deaths from infection reported to be as high as 38% in the United States and 29% in Jamaica. 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; mortality rates can be 20-25% unless prompt treatment is administered. Methods Our study was conducted in 3 outpatient sites and 1 inpatient site, the outpatient sites were all located within Mukuru informal settlement, a densely populated slum, 15km East of Nairobi City. Blood and stool samples from children with fever alone and with fever and diarrhea were collected for processing for presence of iNTS using basic microbiology procedures. Dry blood spots were also taken and processed for sickle cell protein markers using High performance liquid chromatography (HPLC). Results A total of 22,246 blood and stool samples were collected from children < 16 years of age with fever/with or without diarrhea, for a period of 6 years and subjected to microbiological culture and detection of bacterial pathogens. Out of these 741 (3.3%) tested positive for Salmonella species. A total of 338/741(41%) NTS were isolated across all the sites; these consisted of 158/741(21%) Salmonella Enteritidis and 180/741 (24%) Salmonella Typhimurium. The most common resistance phenotype was ampicillin, cotrimoxazole and chloramphenicol (35.03%). We had 12/338 (3.6%) isolates (11 of them being Salmonella Typhimurium) that were ESBL producers conferring resistance to 3rd generation cephalosporins (Amp C β-lactamases) while only 0.3% were resistant to ciprofloxacin. A total of 118 (35.03%) isolates were MDR. Out of 2684 dry blood samples subjected to HPLC for investigation of sickle cell disease traits, 1820/2684 (67%) had normal hemoglobin (Hb AA/ Hb AF); (162/2684 (6%) tested positive for Sickle Cell Traits (Hb AS/Hb AFS); while 4/2684 (0.2%) tested positive for Sickle cell disease (Hb FS). Conclusion The high MDR resistance phenotype in iNTS isolates and emerging resistance to third generation cephalosporins is of great concern in management of iNTS in our settings. Sickle cell disease was not a major factor among children with iNTS disease and no significant association with iNTS was observed.

Background In Kenya, typhoid fever and invasive non-typhoidal salmonellosis present a huge burden of disease, especially in poor-resource settings where clean water supply and sanitation conditions are inadequate. The epidemiology of both diseases is poorly understood in terms of severity and risk factors. The aim of the study was to determine the disease burden and spatial distribution of salmonellosis, as well as socioeconomic and environmental risk factors for these infections, in a large informal settlement near the city of Nairobi, from 2013 to 2017. Methods Initially, a house-to-house baseline census of 150,000 population in Mukuru informal settlement was carried out and relevant socioeconomic, demographic, and healthcare utilization information was collected using structured questionnaires. Salmonella bacteria were cultured from the blood and faeces of children Salmonella serotypes and risk factors were conducted using Pearson Chi-Square (χ2) test. Results A total of 16,236 children were recruited into the study. The prevalence of bloodstream infections by Non-Typhoidal Salmonella (NTS), consisting of Salmonella Typhimurium/ Enteriditis, was 1.3%; Salmonella Typhi was 1.4%, and this was highest among children Salmonella Typhimurium/ Enteriditis was not significantly associated with rearing any domestic animals. Rearing chicken was significantly associated with high prevalence of S. Typhi (2.1%; p = 0.011). The proportion of children infected with Salmonella Typhimurium/ Enteriditis was significantly higher in households that used water pots as water storage containers compared to using water directly from the tap (0.6%). Use of pit latrines and open defecation were significant risk factors for S. Typhi infection (1.6%; p = 0.048). The proportion of Salmonella Typhimurium/ Enteriditis among children eating street food 4 or more times per week was higher compared to 1 to 2 times/week on average (1.1%; p = 0.032). Conclusion Typhoidal and NTS are important causes of illness in children in Mukuru informal settlement, especially among children less than 16 years of age. Improving Water, Sanitation and Hygiene (WASH) including boiling water, breastfeeding, hand washing practices, and avoiding animal contact in domestic settings could contribute to reducing the risk of transmission of Salmonella disease from contaminated environments.

Invasive Non-typhoidal Salmonella (iNTS) disease is a major public health challenge, especially in Sub-Saharan Africa (SSA). In Kenya, mortality rates are high (20–25%) unless prompt treatment is instituted. The most common serotypes are Salmonella enterica serotype Typhimurium (S. Typhimurium) and Salmonella enterica serotype Enteritidis (S. Enteritidis). In a 5 year case-control study in children residing in the Mukuru informal settlement in Nairobi, Kenya, a total of 4201 blood cultures from suspected iNTS cases and 6326 fecal samples from age-matched controls were studied. From the laboratory cultures we obtained a total of 133 S. Typhimurium isolates of which 83(62.4%) came from cases (53 blood and 30 fecal) and 50(37.6%) from controls (fecal). A total of 120 S. Enteritidis consisted of 70(58.3%) from cases (43 blood and 27 fecal) and 50(41.7%) from controls (fecal). The S. Typhimurium population fell into two distinct ST19 lineages constituting 36.1%, as well as ST313 lineage I (27.8%) and ST313 lineage II (36.1%) isolates. The S. Enteritidis isolates fell into the global epidemic lineage (46.6%), the Central/Eastern African lineage (30.5%), a novel Kenyan-specific lineage (12.2%) and a phylogenetically outlier lineage (10.7%). Detailed phylogenetic analysis revealed a high level of relatedness between NTS from blood and stool originating from cases and controls, indicating a common source pool. Multidrug resistance was common throughout, with 8.5% of such isolates resistant to extended spectrum beta lactams. The high rate of asymptomatic carriage in the population is a concern for transmission to vulnerable individuals and this group could be targeted for vaccination if an iNTS vaccine becomes available., Author summary Blood-stream infections in young children in Sub-Saharan Africa cause high levels of morbidity and mortality. Non-typhoidal Salmonella (NTS) serovars Typhimurium and Enteritidis are especially important in causing blood-stream infections in Kenya. In this case-control study we examined a total of 4201 children with potential blood-stream infections and compared their NTS genotypes with those found in fecal samples of 6326 asymptomatic age-matched controls. From a phylogenetic analysis, we observed a high rate of carriage in cases and controls of multidrug resistant Salmonella genotypes with similarity to those causing invasive disease. We hypothesize that the high carriage rates in asymptomatic population may be contributing to maintenance and transmission of NTS disease among vulnerable population of children.

Theta burst stimulation is increasingly growing in popularity as a non-invasive method of moderating corticospinal networks. Theta burst stimulation uses gamma frequency trains applied at the rhythm of theta, thus, mimicking theta–gamma coupling involved in cognitive processes. The dorsolateral prefrontal cortex has been found to play a crucial role in numerous cognitive processes. Here, we include 25 studies for review to determine the cognitive effects of continuous theta burst stimulation over the dorsolateral prefrontal cortex; 20 of these studies are healthy participant and five are patient (pharmacotherapy-resistant depression) studies. Due to the heterogeneous nature of the included studies, only a descriptive approach is used and meta-analytics ruled out. The cognitive effect is measured on various cognitive domains: attention, working memory, planning, language, decision making, executive function, and inhibitory and cognitive control. We conclude that continuous theta burst stimulation over the dorsolateral prefrontal cortex mainly inhibits cognitive performance. However, in some instances, it can lead to improved performance by inhibiting the effect of distractors or other competing irrelevant cognitive processes. To be precise, continuous theta burst stimulation over the right dorsolateral prefrontal cortex impaired attention, inhibitory control, planning, and goal-directed behavior in decision making but also improved decision making by reducing impulsivity. Conversely, continuous theta burst stimulation over the left dorsolateral prefrontal cortex impaired executive function, working, auditory feedback regulation, and cognitive control but accelerated the planning, decision-making process. These findings constitute a useful contribution to the literature on the cognitive effects of continuous theta burst stimulation over the dorsolateral prefrontal cortex.

Background: Good Clinical Laboratory Practice (GCLP) is a standard that helps ensure the quality and reliability of research data through principles of Good Laboratory Practice (GLP) and Good Clinical Practice (GCP). The implementation of GCLP includes careful documentation of procedures, competencies and safety measures. Implementation of GCLP is influenced by existing resources and quality systems, thus laboratories in low- and middle-income countries may face additional challenges. Methods: This paper describes implementation of Good Clinical Laboratory Practice (GCLP) at the Kenya Medical Research Institute-Center for Microbiology Research (KEMRI-CMR) as part of a quality system to support medical research. This study employed assessment, twinning (institutional mentorship) model, conducting relevant training workshops and Kaizen 5S approaches to implement an effective quality management system using GCLP standard. This was achieved through a collaboration between the KEMRI/Wellcome Trust Research Programme (KWTRP) and KEMRI-CMR. The aim was compliance and continuous monitoring to meet international GCLP standards in a way that could be replicated in other research organizations. Results: Following a baseline assessment in March 2017, training, mentorship and a cycle of quality audit and corrective action using a Kaizen 5S approach (sorting, setting in order, shining, standardizing and sustaining) was established. Laboratory personnel were trained in writing standard operating procedures and analytical plans, microbiological techniques, and good documentation practice. Mid-term and exit assessments demonstrated significant declines in non-conformances across all GCLP elements. KEMRI-CMR achieved GCLP accreditation in May 2018 by Qualogy Ltd (UK). Conclusions: Involving all the laboratory personnel in implementation of quality management system processes is critical to success. An institutional mentorship (twinning) approach shows potential for future collaborations between accredited and non-accredited organizations to accelerate the implementation of high-quality management systems and continuous improvement.

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. The knowledge of hotspots in endemic settings can help to prioritize management and control measures in Kenya and the region. Methods Using blood cultures, we investigated children presenting with fever of unknown origin for Salmonella infections. We performed antimicrobial susceptibility testing and whole genome sequencing to further characterize Salmonella isolates. Using Global Positioning System technologies, we mapped Salmonella isolates to households of patients in the study site and determined risk factors associated with high concentration of cases in particular sites. Results A total of 281 Salmonella species (149 from blood and 132 from fecal samples) from febrile children

Tungiasis or jigger infestation is a parasitic disease caused by the female sand flea Tunga penetrans. Secondary infection of the lesions caused by this flea is common in endemic communities. This study sought to shed light on the bacterial pathogens causing secondary infections in tungiasis lesions and their susceptibility profiles to commonly prescribed antibiotics. Participants were recruited with the help of Community Health Workers. Swabs were taken from lesions which showed signs of secondary infection. Identification of suspected bacteria colonies was done by colony morphology, Gram staining, and biochemical tests. The Kirby Bauer disc diffusion test was used to determine the drug susceptibility profiles. Out of 37 participants, from whom swabs were collected, specimen were positive in 29 and 8 had no growth. From these, 10 different strains of bacteria were isolated. Two were Gram positive bacteria and they were, Staphylococcus epidermidis (38.3%) and Staphylococcus aureus (21.3%). Eight were Gram negative namely Enterobacter cloacae (8.5%), Proteus species (8.5%), Klebsiellla species (6.4%), Aeromonas sobria (4.3%), Citrobacter species (4.3%), Proteus mirabillis(4.3%), Enterobacter amnigenus (2.1%) and Klebsiella pneumoniae (2.1%). The methicillin resistant S. aureus (MRSA) isolated were also resistant to clindamycin, kanamycin, erythromycin, nalidixic acid, trimethorprim sulfamethoxazole and tetracycline. All the Gram negative and Gram positive bacteria isolates were sensitive to gentamicin and norfloxacin drugs. Results from this study confirms the presence of resistant bacteria in tungiasis lesions hence highlighting the significance of secondary infection of the lesions in endemic communties. This therefore suggests that antimicrobial susceptibility testing may be considered to guide in identification of appropriate antibiotics and treatment therapy among tungiasis patients., Author summary Secondary bacterial infection of tungiaisis lesions is a threat to jigger infested patients. Once the flea penetrates the skin, it leaves an opening on the skin through which it lays eggs, defecates and breathes throughout it’s life cycle on the host. At the same time, it feeds on the host’s blood hence a direct connection of the environment to the blood stream is established. Chances of bacteria getting into the blood stream is therefore greatly enhanced. Once bacteria gets into the blood, it can lead to life threatening conditions like septicemia, meningitis, pneumonia and toxic shock syndrome. Affected communities are oblivious to this danger and they neither seek nor get treated for this parasitosis. The health officials and scientific community also continue to ignore this disease hence it’s extremely neglected. Consequently, not much is understood concerning the disease dynamics, distribution and pathogenesis. This study therefore is a deliberate effort to bring attention to one aspect of the disease dynamics of this menace.