Trabelsi, S. | bioRxiv Science

bioRxiv2024

Whole Genome Sequencing Analysis of a Recent Multi-Drug Resistant Shigella sonnei Outbreak Among Tunisian Children

BackgroundShigella sonnei, a leading cause of shigellosis, is a global health concern, particularly affecting children under five. The emergence of multidrug-resistant (MDR) strains, including resistance to key antibiotics like ciprofloxacin and third-generation cephalosporins, exacerbates treatment challenges. This study investigates the genetic and antimicrobial resistance profiles of S. sonnei isolates from Tunisia, focusing on an outbreak of extended-spectrum beta-lactamase (ESBL)-producing strains. MethodsWe analysed nine S. sonnei isolates collected between September 2022 and January 2023 from Tunisian hospitals, using whole genome sequencing (WGS). Standard bacterial identification and serotyping methods were employed alongside antimicrobial susceptibility testing. We examined the genetic relatedness of the isolates, identified resistance genes, and characterised virulence factors. ResultsAll the isolates were confirmed as S. sonnei H6, biotype a, and belonged to lineage 3, clade 6 and sub-lineage 3. All harboured blaCTX-M-15, conferring resistance to third-generation cephalosporins. These were chromosomally integrated, suggesting stable resistance. Five isolates exhibited fluoroquinolone resistance associated with the qnrS1 gene, and all isolates had a single quinolone resistance-determining region mutation (GyrA-D87Y). Additionally, the plasmid-borne mphA gene, conferring resistance to macrolides, was prevalent. Single-linkage hierarchical clustering analysis indicated close genetic relationships with S. sonnei strains from Europe, particularly France and the UK (0 to 31 core genome MLST allele differences), indicating recent international dissemination. ConclusionThis study provides the first comprehensive molecular characterisation of MDR S. sonnei in Tunisia, highlighting a significant public health threat. The findings underscore the importance of continuous genomic surveillance to track the spread of resistant strains and inform public health interventions.

genomics↗

bioRxiv2018

Comparison between three concentration techniques for diagnosing intestinal parasites

BackgroundIntestinal parasitoses still are a noticeable threat to public health. The direct diagnosis of such parasites requires the use of concentration techniques, whose sensitivities for protozoan cysts and helminth eggs are far from equal.\n\nAimTo compare the Willis, Ritchie and Bailenger concentration techniques in terms of parasite recovery, cost, time, and biosafety.\n\nMethodsThis prospective study analysed 236 stool specimens for intestinal parasites using the direct wet smear and the above-mentioned concentration techniques applied separately.\n\nResultsBiphasic techniques identified significantly more positive specimens for intestinal parasites than the Willis technique, the latter leading to less concentrated and more altered parasitic elements on microscopy. No statistically significant difference emerged from comparing Ritchies and Bailengers methods. The Willis technique was the safest, yet the costliest and the most time-consuming of the studied methods.\n\nConclusionsEven though the hazardous reagents employed may raise legitimate concerns over their health implications, biphasic techniques prove to be uncostly, quick to perform, and highly sensitive for detecting faecal parasites, therefore ensuring a safe diagnosis for routine stool examinations.

microbiology↗