- Volume 73, Issue 12, 2024

Diagnosis of Clostridioides difficile infection (CDI) remains challenging as it involves in the first instance recognition (clinical awareness) of the patients’ symptoms for clinical suspicion of CDI to warrant testing, and secondly, different laboratory tests have been described for CDI. Due to the overwhelming amount of information in the literature on CDI tests and their performance, with separately published guidelines, this review aims to provide a comprehensive but concise summary of the current state of CDI diagnostic testing. Current knowledge and the impact of using different laboratory diagnostic procedures for CDI, including the most recommended approach as a two-step algorithm and the concept of diagnostic stewardship, are being discussed. This review provides an updated overview and valuable take-home messages in the field of CDI laboratory testing and highlights that timely diagnosis is important for the clinical management of CDI and that the recommended testing procedures are increasingly becoming more widely accepted.

Introduction. Diagnosis of uveitis is challenging due to the multitude of possible pathogenies. Identifying infectious and non-infectious uveitis is of great clinical significance. Recently, metagenomic next-generation sequencing (mNGS) was used to detect infectious and non-infectious uveitis, but its efficacy has not been widely evaluated.

Hypothesis. Compared with routine diagnostic tests (RDTs), mNGS is more effective in identifying infectious and non-infectious uveitis.

Aim. To describe the microbiological diagnostic performance of mNGS in detecting infectious and non-infectious uveitis.

Methodology. Patients with suspected infectious uveitis of uncertain pathogenesis were tested by mNGS and RDTs. Infectious and non-infectious uveitis were grouped according to the final diagnosis based on comprehensive analysis of the test results and the effect of therapy. The test results were used to assess the performance of mNGS in actual clinical practice.

Results. Fifty-eight cases were enrolled in this project, including 32 cases of infectious uveitis and 26 cases of non-infectious uveitis. The sensitivity of mNGS was 96.88%, which was much higher than that of RDTs. The detected pathogenic micro-organisms included bacteria, fungi, viruses, Toxoplasma gondii and Bartonella. Consequently, mNGS showed a high negative predictive value (NPV) of 94.74%, indicating that an mNGS negative should be a true negative result most of the time, but a low positive predictive value (PPV) of 79.49%.

Conclusions. mNGS showed extremely high sensitivity but low specificity, which increased the detection rate of infectious uveitis pathogens but might result in false positives. The excellent NPV suggested that the identification of non-infectious uveitis is of considerable clinical importance.

Introduction. Staphylococcus aureus is a bacterium that colonizes various human sites. The pharynx has been considered as a site of little clinical relevance and little studied. Recently, it has been reported that S. aureus can colonize more the pharynx than the nose. In addition, S. aureus can persist in these sites for prolonged periods of time.

Hypothesis. The composition of the pharyngeal and nasal microbiome will differ between persistent, intermittent carriers and non-carriers of S. aureus.

Aim. Determine whether the pharyngeal and nasal microbiome is different between carriers and non-carriers of S. aureus.

Methodology. S. aureus carriers were monitored by means of pharyngeal and nasal exudates of apparently healthy adult university students for 3 months. Samples from individuals of the same carrier type were pooled, and DNA was extracted and the 16S rRNA was sequenced. The sequences were analysed in MOTHUR v.1.48.0 software, by analysing the percentages of relative abundance in the STAMP 2.1.3 program, in addition to the predictive analysis of metabolic pathways in PICRUSt2.

Results. A greater colonization of S. aureus was found in the pharynx than in the nose. The microbiomes of S. aureus carriers and non-carriers do not show significant differences. The main microbiome difference found was between pharyngeal and nasal microbiomes. No significant differences were found in the abundance of the genus Staphylococcus in pharyngeal and nasal S. aureus carriers and non-carriers. The nasal microbiome was found to have more variation compared to the pharyngeal microbiome, which appears to be more stable between individuals and pools. Predictive analysis of metabolic pathways showed a greater presence of Staphylococcus-associated pathways in the nose than in the pharynx.

Conclusion. S. aureus can colonize and persist in the pharynx in equal or greater proportion than in the nose. No statistically significant differences were found in the microbiome of the pharyngeal and nasal carriers and non-carriers of S. aureus, but the pharyngeal and nasal microbiomes are different independent of the type of S. aureus carrier or non-carrier. Therefore, the microbiome apparently does not influence the persistence of S. aureus.

Introduction. Interspecies differences in human, pig and sheep corneal thickness may affect the Pseudomonas aeruginosa colonization. Currently, there is no research investigating the impact of these differences, along with variable storage and culture conditions on infection in ex vivo cornea models. These factors could significantly influence utilizing ex vivo models for drug testing research.

Aim. In this study, we aim to compare the relevance of sheep and pig cornea infection models to human.

Methodology. The corneas were stored in McCarey-Kaufman medium or Eagle’s Minimum Essential Medium or Dulbecco’s Modified Eagle’s Medium/Mixture F-12 Ham medium (incubator) and then infected after varying storage durations. The effect of added foetal bovine serum (FBS) to media and continuous shaking mimicking rinsing with tears on infection was also investigated. The infection outcome was evaluated by comparing c.f.u. between conditions.

Results. The study found that storage conditions, culture media, FBS and continuous rinsing of corneas with media had no significant effect on infection progression in ex vivo keratitis models across selected species.

Conclusions. Pig and sheep models yield results comparable to human corneas. These findings support the interchangeability of ex vivo human, pig and sheep keratitis models for P. aeruginosa infection studies, emphasizing their relevance and reliability in research contexts. This interchangeability is particularly useful for research groups where one particular animal model may not be available. The media in this ex vivo keratitis model can be free of animal components by the removal of FBS, which reduces the reliance on animal-derived products, aligning with ethical considerations and promoting more sustainable and humane scientific practices. This study advances the understanding of ex vivo keratitis models, demonstrating their robustness and potential for broader application in ophthalmic research and drug testing.