Detection of Salmonella Typhi nucleic acid by RT-PCR and anti-HlyE, -CdtB, -PilL, and -Vi IgM by ELISA at sites in Ghana, Madagascar and Ethiopia

Prevalence and Antimicrobial Resistance of Typhoid Fever in Ghana: A Systematic Review and Meta-Analysis

Background/Objectives: Typhoid fever caused by Salmonella enterica serovar Typhi remains an important public health problem in Ghana. Understanding the epidemiology and antimicrobial resistance patterns of S. Typhi is crucial to guide the treatment and control of typhoid fever. This systematic review and meta-analysis aimed to estimate the prevalence of typhoid fever in Ghana and describe the antibiotic susceptibility profiles. Methods: Literature searches were conducted using the PubMed repository and three databases: Scopus, Web of Science, and ScienceDirect. Observational studies reporting typhoid fever prevalence among Ghanaian participants diagnosed by culture or Widal test and published between 1 January 2004 and 16 August 2024 were eligible. Quality was assessed using standardized JBI critical appraisal checklists. Random-effects meta-analysis with a 95% confidence interval was performed to estimate pooled prevalence and conduct subgroup analyses. Results: A total of 22 studies involving 228,107 participants were included in the systematic review. The pooled prevalence of typhoid fever was 4.14% (95% CI: 2.78-5.75). Blood culture detected more cases (3.68%) than stool culture (1.16%). Multidrug resistance was documented in 20-66% of isolates, and ciprofloxacin had the lowest prevalence of resistance (0-17%). Conclusions: This review highlights the substantial typhoid fever burden and evolving antimicrobial resistance in Ghana. Continuous surveillance of the disease is warranted to optimize empiric treatment and control strategies, given the resistance to first-line drugs. Enhanced prevention through water, sanitation, and vaccination programs is imperative.

Fluorescent aptasensor for detection of Salmonella typhimurium using boric acid-functionalized terbium metal-organic framework and magnetic nanoparticles

A fluorescent detection platform was designed using boric acid-functionalized terbium metal-organic framework (BA-Tb-MOF) and carboxyl-modified magnetic nanoparticles (MNPs) to identify Salmonella typhimurium (S. typhimurium) bacteria. Firstly, carboxyl-modified Fe3O4MNPs were coated with specific aptamer (Apt-MNPs) as the capture probe for S. typhimurium. Then, the Apt-MNPs were added to the bacterial suspension to facilitate the targeted binding. Subsequently, the fluorescent probe (BA-Tb-MOF) was introduced into this solution. The BA-Tb-MOF was strongly attached to the bacterial surface through interactions between BA and glycolipids on the bacterial cell walls, forming a stable complex. As the bacterial concentration increased, the fluorescence intensity of the solution progressively decreased due to the binding and removal of bacteria-Apt-MNPs/BA-Tb-MOF complexes through magnetic separation. Under optimum conditions, the concentration of S. typhimurium and the fluorescence intensity showed an inverse linear relationship within the range of 101-109 CFU/mL, and the detection limit was 4 CFU/mL. The developed sensor showed high specificity against several other pathogenic bacteria such as E. coli, S. aureus, and P. aeruginosa. The developed fluorescence platform also successfully detected the S. typhimurium in drinking water and egg samples with satisfactory recoveries (83-98%). This strategy can be investigated further for the detection of S. typhimurium and other pathogens in food and clinical samples.

"Magnet" Based on Activated Silver Nanoparticles Adsorbed Bacteria to Predict Refractory Apical Periodontitis Via Surface-Enhanced Raman Scattering

Refractory apical periodontitis (RAP) is an endodontic apical inflammatory disease caused by Enterococcus faecalis (E. faecalis). Bacterial detection using surface-enhanced Raman scattering (SERS) technology is a hot research topic, but the specific and direct detection of oral bacteria is a challenge, especially in real clinical samples. In this paper, we develop a novel SERS-based green platform for label-free detection of oral bacteria. The platform was built on silver nanoparticles with a two-step enhancement way using NaBH4 and sodium (Na+) to form "hot spots," which resulted in an enhanced SERS fingerprint of E. faecalis with fast, quantitative, lower-limit, reproducibility, and stability. In combination with machine learning, four different oral bacteria (E. faecalis, Porphyromonas gingivalis, Streptococcus mutans, and Escherichia coli) could be intelligently distinguished. The unlabeled detection method emphasized the specificity of E. faecalis in simulated saliva, serum, and even real samples from patients with clinical root periapical disease. In addition, the assay has been shown to be environmentally friendly and without secondary contamination through antimicrobial assays. The proposed label-free, rapid, safe, and green SERS detection strategy for oral bacteria provided an innovative solution for the early diagnosis and prevention of RAP and other perioral diseases.

The Prevalence of Undiagnosed Salmonella enterica Serovar Typhi in Healthy School-Aged Children in Osun State, Nigeria

Typhoid fever remains a significant public health concern due to cases of mis-/overdiagnosis. Asymptomatic carriers play a role in the transmission and persistence of typhoid fever, especially among children, where limited data exist in Nigeria and other endemic countries. We aim to elucidate the burden of typhoid fever among healthy school-aged children using the best surveillance tool(s). In a semi-urban/urban state (Osun), 120 healthy school-aged children under 15 years were enrolled. Whole blood and fecal samples were obtained from consenting children. ELISA targeting the antigen lipopolysaccharide (LPS) and anti-LPS antibodies of Salmonella Typhi, culture, polymerase chain reaction (PCR), and next-generation sequencing (NGS) were used to analyze the samples. At least one of the immunological markers was detected in 65.8% of children, with 40.8%, 37.5%, and 39% of children testing positive for IgM, IgG, and antigen, respectively. Culture, PCR, and NGS assays did not detect the presence of Salmonella Typhi in the isolates. This study demonstrates a high seroprevalence of Salmonella Typhi in these healthy children but no carriage, indicating the inability to sustain transmission. We also demonstrate that using a single technique is insufficient for typhoid fever surveillance in healthy children living in endemic areas.