The burden of hospital-acquired infections (HAI) in sub-Saharan Africa: a systematic review and meta-analysis.

Background: Hospital-acquired infections (HAI) are a leading cause of morbidity and mortality globally. These infections are diverse, but the majority are lower respiratory tract infection (LRTI), surgical site infection (SSI), bloodstream infection (BSI), and urinary tract infection (UTI). For most sub-Saharan African countries, studies revealing the burden and impact of HAI are scarce, and few systematic reviews and meta-analysis have been attempted. We sought to fill this gap by reporting recent trends in HAI in sub-Saharan Africa (SSA) with attention to key patient populations, geographic variation, and associated mortality. Methods: Following the Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) guidelines, we conducted a literature search of six electronic databases (Web of Science, Pubmed, APA PsycInfo, CINAHL, Embase, and the Cochrane Library) to identify studies assessing the prevalence of HAI in SSA countries. Studies published between 01 January 2014 and 31 December 2023 were included. We applied no language or publication restrictions. Record screening and data extractions were independently conducted by teams of two or more reviewers. Using the R software (version 4.3.1) meta and metafor packages, we calculated the pooled prevalence estimates from random-effect meta-analysis, and further explored sources of heterogeneity through subgroup analyses and meta-regression. This study is registered with PROSPERO, CRD42023433271. Findings: Forty-one relevant studies were identified for analysis, consisting of 15 from West Africa (n = 2107), 12 from Southern Africa (n = 2963), 11 from East Africa (n = 2142), and 3 from Central Africa (n = 124). A total of 59.4% of the patient population were associated with paediatric admissions. The pooled prevalence of HAI was estimated at 12.9% (95% CI: 8.9-17.4; n = 7336; number of included estimates [k] = 41, p < 0.001). By subregions, the pooled current prevalence of HAI in the West Africa, Southern Africa, East Africa and Central Africa were estimated at 15.5% (95% CI: 8.3-24.4; n = 2107; k = 15), 6.5% (95% CI: 3.3-10.7; n = 2963; k = 12), 19.7% (95% CI: 10.8-30.5; n = 2142; k = 11) and 10.3% (95% CI: 1.1-27.0; n = 124; k = 3) of the patient populations respectively. We estimated mortality resulting from HAI in SSA at 22.2% (95% CI: 14.2-31.4; n = 1118; k = 9). Interpretation: Our estimates reveal a high burden of HAI in SSA with significant heterogeneity between regions. Variations in HAI distribution highlight the need for infection prevention and surveillance strategies specifically tailored to enhance prevention and management with special focus on West and East Africa, as part of the broader global control effort. Funding: No funding was received for this study.

The SAPS 3 score as a predictor of hospital mortality in a South African tertiary intensive care unit: A prospective cohort study.

BACKGROUND: No African countries were included in the development of the Simplified Acute Physiology Score 3 (SAPS 3). This study aimed to assess the performance of the SAPS 3 as a predictor of hospital mortality in patients admitted to a multi-disciplinary tertiary intensive care unit (ICU) in South Africa. METHODS: A prospective cohort study was undertaken in a tertiary single-centre closed multidisciplinary ICU with 16 beds over 12 months in 2017. First time admissions 12 years and over were included. Exclusions were patients who died within six hours of admission, incomplete data sets and unknown outcome after ICU discharge. Demographic data, clinical admission data and co-morbidities were recorded. The SAPS 3 score was calculated within the first hour of ICU admission. The highest Sequential Organ Failure Assessment score, vasopressor use, mechanical ventilation requirements and details of acute kidney injury, if present, were recorded. Discrimination of the model was evaluated using an area under the receiver operating characteristic curve (AUROC) and calibration by the Hosmer-Lemeshow (HL) Goodness of Fit Test (C and H statistic). The observed versus the SAPS 3 model predicted mortality ratios were compared and the standardized mortality ratio (SMR) was calculated. RESULTS: A total of 829 admissions with a mean SAPS 3 (SD) of 48.1 (16) were included. Of patients with a known human immunodeficiency virus (HIV) status, 32,4% were positive. The ICU and hospital mortality rates were 13.3% and 21.4% respectively. The SAPS 3 model had a AUROC of 0.796 and HL C and H statistics were 12.1 and 11.8 (p-values 0.15 and 0.16). The SMR for the model was 1.002 (95%CI: 0.91-1.10). The mortality of 41% for the subgroup with sepsis/septic shock was higher than predicted with a SMR of 1.24 (95% CI 1.11-1.37). CONCLUSIONS: The SAPS 3 model showed good calibration and fair discrimination when applied to the cohort. The SAPS 3 model can be used to describe the case mix in this African ICU with a high incidence of HIV. Ongoing efforts should be made to improve outcomes of septic patients.

The effect of sphingosine-1-phosphate on the endothelial glycocalyx during ischemia-reperfusion injury in the isolated rat heart.

OBJECTIVE: Sphingosine-1-phosphate is a natural metabolite that is cardioprotective, but its effects on endothelial glycocalyx damage during ischemia-reperfusion are unknown. Therefore, we investigated the effect of sphingosine-1-phosphate on the endothelial glycocalyx during ischemia-reperfusion. METHODS: Isolated hearts from Wistar rats were perfused on a Langendorff system with Krebs-Henseleit buffer and pretreated with sphingosine-1-phosphate (10 nmol/L) before ischemia-reperfusion. Infarct size was measured by triphenyl tetrazolium chloride staining (n ≥ 6 per group). Cardiac edema was assessed by calculating total water content (n = 7 per group) and histologically quantifying the interstitial compartment (n ≥ 3 per group). The post-ischemic coronary release of syndecan-1 was quantified using ELISA. Syndecan-1 immunostaining intensity was assessed in perfusion-fixed hearts (n ≥ 3 per group). RESULTS: Pretreatment with sphingosine-1-phosphate decreased infarct size in isolated hearts subjected to ischemia-reperfusion (P = .01 vs ischemia-reperfusion). However, sphingosine-1-phosphate had no effect on syndecan-1 levels in the coronary effluent or on the intensity of the syndecan-1 immunostaining signal in cardiac tissue. Heart total water content was not significantly different between control and ischemic groups but was significantly decreased in hearts treated with sphingosine-1-phosphate alone. CONCLUSION: These results suggest that sphingosine-1-phosphate-induced cardioprotection against ischemia-reperfusion injury is not mediated by the maintenance of syndecan-1 in the endothelial glycocalyx.

Risk factors and outcomes of acute kidney injury in South African critically ill adults: a prospective cohort study.

BACKGROUND: There is a marked paucity of data concerning AKI in Sub-Saharan Africa, where there is a substantial burden of trauma and HIV. METHODS: Prospective data was collected on all patients admitted to a multi-disciplinary ICU in South Africa during 2017. Development of AKI (before or during ICU admission) was recorded and renal recovery 90 days after ICU discharge was determined. RESULTS: Of 849 admissions, the mean age was 42.5 years and mean SAPS 3 score was 48.1. Comorbidities included hypertension (30.5%), HIV (32.6%), diabetes (13.3%), CKD (7.8%) and active tuberculosis (6.2%). The most common reason for admission was trauma (26%). AKI developed in 497 (58.5%). Male gender, illness severity, length of stay, vasopressor drugs and sepsis were independently associated with AKI. AKI was associated with a higher in-hospital mortality rate of 31.8% vs 7.23% in those without AKI. Age, active tuberculosis, higher SAPS 3 score, mechanical ventilation, vasopressor support and sepsis were associated with an increased adjusted odds ratio for death. HIV was not independently associated with AKI or hospital mortality. CKD developed in 14 of 110 (12.7%) patients with stage 3 AKI; none were dialysis-dependent. CONCLUSIONS: In this large prospective multidisciplinary ICU cohort of younger patients, AKI was common, often associated with trauma in addition to traditional risk factors and was associated with good functional renal recovery at 90 days in most survivors. Although the HIV prevalence was high and associated with higher mortality, this was related to the severity of illness and not to HIV status per se.

Aqueous outflow - A continuum from trabecular meshwork to episcleral veins.

In glaucoma, lowered intraocular pressure (IOP) confers neuroprotection. Elevated IOP characterizes glaucoma and arises from impaired aqueous humor (AH) outflow. Increased resistance in the trabecular meshwork (TM), a filter-like structure essential to regulate AH outflow, may result in the impaired outflow. Flow through the 360° circumference of TM structures may be non-uniform, divided into high and low flow regions, termed as segmental. After flowing through the TM, AH enters Schlemm's canal (SC), which expresses both blood and lymphatic markers; AH then passes into collector channel entrances (CCE) along the SC external well. From the CCE, AH enters a deep scleral plexus (DSP) of vessels that typically run parallel to SC. From the DSP, intrascleral collector vessels run radially to the scleral surface to connect with AH containing vessels called aqueous veins to discharge AH to blood-containing episcleral veins. However, the molecular mechanisms that maintain homeostatic properties of endothelial cells along the pathways are not well understood. How these molecular events change during aging and in glaucoma pathology remain unresolved. In this review, we propose mechanistic possibilities to explain the continuum of AH outflow control, which originates at the TM and extends through collector channels to the episcleral veins.

Wholemount imaging reveals abnormalities of the aqueous outflow pathway and corneal vascularity in Foxc1 and Bmp4 heterozygous mice.

Mutations in the FOXC1/Foxc1 gene in humans and mice and Bmp4 in mice are associated with congenital anterior segment dysgenesis (ASD) and the development of the aqueous outflow structures throughout the limbus. The aim of this study was to advance our understanding of anterior segment abnormalities in mouse models of ASD using a 3-D imaging approach. Holistic imaging information combined with quantitative measurements were carried out on PECAM-1 stained individual components of the aqueous outflow vessels and corneal vasculature of Foxc1(+/-) on the C57BL/6Jx129 and ICR backgrounds, Bmp4(+/-) ICR mice, and wildtype mice from each background. In both wildtype and heterozygotes, singular, bifurcated and plexus forms of Schlemm's canal were noted. Of note, missing portions of the canal were seen in the heterozygous groups but not in wildtype animals. In general, we found the number of collector channels to be reduced in both heterozygotes. Lastly, we found a significant increase in the complexity of the corneal arcades and their penetration into the cornea in heterozygotes as compared with wild types. In conclusion, our 3-D imaging studies have revealed a more complex arrangement of both the aqueous vessels and corneal arcades in Foxc1(+/-) and Bmp4(+/-) heterozygotes, and further advance our understanding of how such abnormalities could impact on IOP and the aetiology of glaucoma.

The distribution of mucous secreting cells in the gastrointestinal tracts of three small rodents from Saudi Arabia: Acomys dimidiatus, Meriones rex and Meriones libycus.

The proportion of mucin phenotypes (which form the protective biofilm of the gastrointestinal tract) differs between intestinal regions. This study examines the distribution of mucin secreting cells in the gastrointestinal tracts of the Eastern spiny mouse (Acomys dimidiatus), King jird (Meriones rex) and Libyan jird (Meriones libycus), which inhabit the dry and hot deserts of Saudi Arabia. Intestinal tract samples were processed to wax and tissue sections stained with Alcian Blue-Periodic Acid Schiff (AB-PAS) and High Iron Diamine-Alcian Blue (HID-AB) in order to determine different mucin phenotypes by quantitative analysis. Mixed mucin secreting cells (combined neutral and acid) was the predominant mucin secreting cell type observed throughout the gastrointestinal tract in all species. Acid mucin secreting goblet cells were mainly located in the colon. A. dimidiatus presented with significantly more total sialo than sulfomucin secreting cells while the opposite was true for both Meriones species. The distribution of mucin secreting cells is therefore similar to previously reported results for small mammals not living under arid conditions.

The three-dimensional organisation of the post-trabecular aqueous outflow pathway and limbal vasculature in the mouse.

The mouse eye has been used as a model for studies on the microanatomy of the outflow pathways but most of what is known comes from histological sections. These studies have focused mainly on the morphological features of the trabecular meshwork, Schlemm's canal and aqueous channels that link to the superficial episcleral vasculature. However, the anatomical architecture of the aqueous outflow vessels and their relationship to each other and to the general vascular circulation is not well understood. The aim of this study was to provide a detailed description of the microarchitecture of the aqueous outflow vessels and their relationship to the superficial limbal/episcleral vasculature throughout the entire limbus. The aqueous outflow vessels and blood and lymphatic vessels were imaged in PECAM-1 and LYVE-1 immunostained whole anterior segments of adult mice and three-dimensional (3-D) reconstructions of the optical sections were generated to reveal the aqueous, blood and lymphatic architecture. The arterial supply, venous drainage, organisation of perilimbal vasculature, collector channels/aqueous veins and the morphology of Schlemm's canal were revealed in their entirety and the relationships between these structures is described. Schlemm's canal was PECAM-1 positive but there was no affinity for the lymphatic marker LYVE-1. We show that Schlemm's canal is a continuous circular structure and more often seen as a single, broad, varicose vessel with short regions appearing as a plexus. Aqueous veins link Schlemm's canal to the superficial vasculature and there were no direct links seen between the canal and the lymphatic vessels.

Comparative gastrointestinal morphology of three small mammalian insectivores: Acomys spinosissimus (Rodentia), Crocidura cyanea (Eulipotyphla), and Amblysomus hottentotus (Afrosoricida).

The gastrointestinal morphology was investigated in three mammalian insectivorous species, namely Acomys spinosissimus, Crocidura cyanea, and Amblysomus hottentotus. The aim of the study was to provide a comprehensive morphological comparison between the different species and to explore whether anatomical gastrointestinal adaptations are associated with the insectivorous diet of these species. The shape, proportional length, and proportional surface areas of the different gastrointestinal regions were recorded and compared in the three insectivores. Hematoxylin and Eosin (H&E) and Alcian Blue/Periodic Acid Schiff (AB/PAS) were used for morphological assessment. In all three species, the stomach was simple and uncompartmentalized. The internal aspect of the stomach in A. spinosissimus was hemi-glandular, containing stratified squamous epithelium in the fundus, with glandular epithelium in the body and pyloric region. However, C. cyanea and A. hottentotus had wholly glandular stomachs. Paneth cells were not observed in the intestinal tracts of C. cyanea and A. hottentotus. Acomys spinosissimus was the only species studied that had a cecum. The proximal colonic region of A. spinosissimus had V-shaped mucosal folds. Histologically, C. cyanea had villi throughout the entire gastrointestinal tract (GIT), whereas for A. hottentotus villi were not present in the most distal gastrointestinal regions. In both C. cyanea and A. hottentotus, longitudinal mucosal folds were present in the distal part of the colon. The GITs of C. cyanea and A. hottentotus showed little morphological differentiation namely, a simple, glandular stomach and the lack of a cecum.

A comparative histochemical study of the distribution of mucins in the gastrointestinal tracts of three insectivorous mammals.

The distribution of mucous secreting goblet cells was examined in the gastrointestinal tracts of three insectivores namely: Acomys spinosissimus (Southern African spiny mouse), Crocidura cyanea (Reddish gray musk shrew) and Amblysomus hottentotus (Hottentot golden mole) in order to improve our understanding of the quality and composition of the protective intestinal biofilm. Intestinal tracts were fixed and processed to wax for histology. Serial transverse sections were stained using alcian blue-periodic acid Schiff, alcian blue-aldehyde fuchsin and alcian blue-high iron diamine techniques. Photomicrographs of the stained sections were analyzed by quantifying the number of goblet cells containing mucins per mm(2) in the surface epithelial or crypt areas. Neutral mucins predominated in the gastric epithelium of all three insectivores, while sialomucins were absent in the stomach of C. cyanea. In all three species, goblet cells producing a mixture of neutral and acid mucins were most abundant throughout the intestinal tract as were cells secreting a mixture of sulfomucins and sialomucins. However, differences between the insectivore species were observed in the qualitative expression and distribution of mucins throughout the intestinal tract. Similarities between the insectivores of this study and other distantly related species suggest that mixed mucin goblet cells are essential for the formation of the biofilm, irrespective of their diet or taxonomy.

The comparative anatomy of the abdominal gastrointestinal tract of six species of African mole-rats (Rodentia, Bathyergidae).

The gastrointestinal tracts (GITs) of six species of African mole-rats (Bathyergidae) were compared. The aim was to provide a comprehensive anatomical comparison between the different species. The relative shape, length, and surface areas were taken into account to determine whether the GITs are phylogenetically constrained or exhibit anatomical adaptations in response to diets. In all six species the stomach was simple and glandular. With the exception of Heterocephalus glaber, the caecum was coiled in a flat spiral, the ascending colon was arranged in a loop of varying lengths, and a mucosal colonic papillary-lined groove was present in the ascending colon in all species. By contrast, the caecum in H. glaber was uncoiled, the ascending colon was not looped, and the groove was not papillated. A caeco-appendix was observed only in Bathyergus suillus and Georychus capensis. Hierarchical multivariate cluster analysis on the presence/absence of nine anatomical structures associated with the GIT of mole-rats revealed that H. glaber was anatomically the least similar of the six species (77.6% similarity) with respect to the nine GIT variables included. All Cryptomys species were the same (100% similarity), and two species B. suillus and G. capensis grouped together and were more similar to the Cryptomys genus (95% similarity) than they were to H. glaber. These findings support previous phylogenetic classifications. The voluminous caeco-colon in B. suillus may be explained by its ingestion of grasses in addition to below-ground storage organs of plants. We conclude that phylogeny and diet affect the GIT anatomy of the African mole rats studied here.

Rapid three-dimensional quantification of VEGF-induced scaffold neovascularisation by microcomputed tomography.

Microcomputed tomography (micro-CT) is increasingly being used to analyze the three-dimensional structure and architecture of microvascular networks. Therefore we have evaluated a micro-CT analysis of VEGF-induced vessel ingrowth into a porous polyurethane scaffold through comparison with analyses by CD31 immunohistochemistry, vascular perfusion by intravital Lycopersicon esculentum lectin perfusion and vascular corrosion casting. Micro-CT scanning found a similar level of vascularisation within the VEGF treated scaffolds to that determined by the other analytical methods. However, although the relative increase in vascularisation (17 fold above PBS controls p<0.05) induced by VEGF determined by micro-CT was similar to the perfusion based analyses (20.1 and 10.4 fold for lectin perfusion and vascular corrosion respectively p<0.05), it differed substantially from that determined by CD31 immunohistochemistry (3.2 fold p<0.05). This difference was due to a large proportion of unperfused vessels in the PBS control that were not present in the VEGF group. The increase in perfusion probably resulted in part from an increase in average vessel diameter. Though this increase was detected by micro-CT, the actual diameters were overestimated by 60-90% most likely as a consequence of a merging effect for juxtaposed vessels. Thus whilst micro-CT gives an accurate three-dimensional quantification of the VEGF-induced increase in perfused vessels, resolution needs to be maximized for accurate sizing of a microvascular network's components.

Homologous substitution of ACE C-domain regions with N-domain sequences: effect on processing, shedding, and catalytic properties.

Angiotensin-converting enzyme (ACE) exists as two isoforms: somatic ACE (sACE), comprised of two homologous N and C domains, and testis ACE (tACE), comprised of the C domain only. The N and C domains are both active, but show differences in substrate and inhibitor specificity. While both isoforms are shed from the cell surface via a sheddase-mediated cleavage, tACE is shed much more efficiently than sACE. To delineate the regions of tACE that are important in catalytic activity, intracellular processing, and regulated ectodomain shedding, regions of the tACE sequence were replaced with the corresponding N-domain sequence. The resultant chimeras C1-163Ndom-ACE, C417-579Ndom-ACE, and C583-623Ndom-ACE were processed to the cell surface of transfected Chinese hamster ovary (CHO) cells, and were cleaved at the identical site as that of tACE. They also showed acquisition of N-domain-like catalytic properties. Homology modelling of the chimeric proteins revealed structural changes in regions required for tACE-specific catalytic activity. In contrast, C164-416Ndom-ACE and C191-214Ndom-ACE demonstrated defective intracellular processing and were neither enzymatically active nor shed. Therefore, critical elements within region D164-V416 and more specifically I191-T214 are required for the processing, cell-surface targeting, and enzyme activity of tACE, and cannot be substituted for by the homologous N-domain sequence.

Ceramide attenuates hypoxic cell death via reactive oxygen species signaling.

We have previously demonstrated that tumor necrosis factor alpha (TNFalpha), a cytokine known to be induced by ischemia, independently promotes preconditioning in part via ceramide generation. As reactive oxygen species (ROS) signaling is evoked by ischemic preconditioning, by TNFalpha and by ceramide we reasoned that ceramide-induced preconditioning is ROS-mediated. Fibroblastic L-cells were subjected to 8 hours simulated ischemia and were preconditioned by pretreatment with cell permeable c2 ceramide (1 microM) with or without the antioxidant N-mercaptopropionyl glycine (MPG; 1 mM). Pretreatment with ceramide reduced lactate dehydrogenase release at the end of the simulated ischemia but this cytoprotective effect was lost in the presence of MPG. Concurrent temporal ROS generation was measured using confocal microscopy on cells stained with dichlorofluorescein diacetate (DCF-DA). Ceramide increased ROS production after 30 minutes and this induction was decreased by MPG. Incubation of ceramide with cyclooxygenase-2 inhibitor, NS 398 (10 microM), or with a mitochondrial respiratory chain inhibitor, rotenone (10 microM) reduced the cytoprotective effect of ceramide in parallel with a partial diminution in ROS generation. In contrast, inhibition of other ROS-producing systems including nitric oxide synthase, xanthine oxidase, or NADPH oxidase failed to modulate ceramide-induced cytoprotection. Collectively, these data demonstrate that ceramide induces a cell survival program through ROS signaling activated, in part, via cyclooxygenase and the mitochondrial respiratory chain.

Deletion of the cytoplasmic domain increases basal shedding of angiotensin-converting enzyme.

Ectodomain shedding generates soluble isoforms of cell-surface proteins, including angiotensin-converting enzyme (ACE). Increasing evidence suggests that the juxtamembrane stalk of ACE, where proteolytic cleavage-release occurs, is not the major site of sheddase recognition. The role of the cytoplasmic domain has not been completely defined. We deleted the cytoplasmic domain of human testis ACE and found that this truncation mutant (ACE-DeltaCYT) was shed constitutively from the surface of transfected CHO-K1 cells. Phorbol ester treatment produced only a slight increase in shedding of ACE-DeltaCYT, unlike the marked stimulation seen with wild-type ACE. However, for both wild-type ACE and ACE-DeltaCYT, shedding was inhibited by the peptide hydroxamate TAPI and the major cleavage site was identical, indicating the involvement of similar or identical sheddases. Cytochalasin D markedly increased the basal shedding of wild-type ACE but had little effect on the shedding of ACE-DeltaCYT. These data suggest that the cytoplasmic domain of ACE interacts with the actin cytoskeleton and that this interaction is a negative regulator of ectodomain shedding.