Comparative analysis of polymerase chain reaction assay for herpes simplex virus 1 detection in tear

Diagnostic performance of real-time quantitative PCR in tear samples in various subtypes of herpes simplex keratitis

Diagnosis of herpes simplex keratitis (HSK) is mostly based on clinical findings, yet biological confirmation supports management of challenging cases. This study evaluated the place of real-time quantitative PCR (RT-qPCR) on tear samplings in the management of HSK. Clinical records of patients who underwent tear sampling tested by RT-qPCR for herpes simplex virus type 1 for an acute episode of corneal inflammation or defect between January 2013 and December 2021 were retrospectively reviewed, and results were compared to clinical diagnosis (i.e., HSK or not) based on biomicroscopic findings and medical history. Of 465 tested tear samples from 364 patients, a clinical diagnosis of active (ongoing) HSK was recorded in 240 cases, among which 76 were RT-qPCR positive (global sensitivity of 31.6%, specificity of 99.5%). Sensitivity of RT-qPCR was higher in epithelial (97.4%) and stromal keratitis with ulceration (48.7%), compared to other types of HSK (23.5% in keratouveitis, 13.6% in endotheliitis, 11.1% in postherpetic neurotrophic keratopathy, and 8.1% in stromal keratitis without ulceration). The highest viral loads were detected from epithelial and stromal keratitis with ulceration, while in HSK with no epithelial involvement, the viral load detected was 196-fold lower, on average. The proportion of clinically characterized HSK patients with negative tear samples was higher in patients receiving antiviral treatment (P < 0.0001). RT-qPCR, performed on tear samples, can help in confirming diagnosis in case of presumed HSK, including clinical forms with no obvious epithelial involvement. The sensitivity of tear sampling is much higher whenever epithelial keratitis is present.

High prevalence of Babesia microti in small mammals in Beijing

BACKGROUND

Babesiosis is an emerging tick-borne zoonotic infectious disease. Babesia microti is responsible for most cases of human babesiosis globally. It is important to investigate the prevalence of B. microti in the mammalian host population of a specific region in order to elucidate mechanisms of pathogen transmission and to define geographic areas where humans face the greatest risk of exposure. The aim of this study is to understand the prevalence and genotypes of B. microti in the small mammals that are found in Beijing, China.

METHODS

We trapped small mammals from all of the 16 urban, suburban, and outer suburban districts of Beijing during the years 2014, 2017 and 2018. Genomic DNA was extracted from the heart tissues individually and the Babesia 18S rRNA gene was detected by PCR. The genotypes of B. microti were identified based on sequence alignments and phylogenetic analysis. The morphology of the parasites was observed under light microscopy. The risk factors were analyzed statistically based on both univariate analyses and multivariate logistic regression.

RESULTS

A total of 1391 small mammals were collected. Positive infection of B. microti was detected in 12.1% (168/1391) of small mammals from 15 out of the 16 districts. Both Kobe-type and U.S.-type B. microti, accounting for 9.5% and 2.7%, respectively, were identified. Classic diverse morphologic forms of B. microti were observed. Specific types of ecological habitats including shrub areas, broad-leaved forest, and cropland were revealed to be risk factors associated with B. microti infection.

CONCLUSIONS

This study demonstrated the wide prevalence of B. microti infection in eight species of small mammals in Beijing, with Kobe-type more prevalent than U.S.-type. This study provides fundamental information for the development of informed prevention and control measures by public health authorities; the data gathered indicates a need for further monitoring of both clinical diseases in individuals presenting with babesiosis-like symptoms, as well as the infection status of ticks in high risk areas.

A systematic review on advances in diagnostics for herpes simplex keratitis

Herpes simplex keratitis (HSK) is a significant cause of vision impairment worldwide. Currently, there are no set diagnostic criteria, and popular diagnostic methods, including clinical examination of the eye via slit lamp examination, could lead to false-negatives and misdiagnoses. Molecular testing with polymerase chain reaction (PCR) may lack concordance with clinical findings, posing a great challenge to ophthalmologists. We evaluate recent studies on techniques for the diagnosis of HSK. We included a total of 23 studies published between 2010 and 2020 in English on diagnostic techniques, including in vivo confocal microscopy, polymerase PCR testing, protein detection in tear film with enzyme-linked immunosorbent assay, and various other protein assays. Although PCR has been widely used as one of the current diagnostic methods for HSK, most studies evaluated its efficacy after including alterations to its normal protocol. Tear sample analysis was performed using multiple tools, although corneal scrapings demonstrated a higher positive detection rate. Diagnostic tools identified were able to detect HSK with varying accuracy. Newer diagnostic techniques like multiplex dot hybridization assay and immunochromatographic assays may be considered as the point-of-care preliminary diagnostic tools. More reliable results may be generated by developing a standardized diagnostic protocol.

Evaluation of commonly used tear sampling methods and their relevance in subsequent biochemical analysis

The human precorneal tear film is a special body fluid, since it is a complex mixture of proteins, lipids, small bioactive molecules, and their concentrations and relative distribution represent not only the metabolic state of the ocular surface but also the systemic and local homeostasis of the outer eye and the human body. This suggests that biochemical analysis of the precorneal tear film composition may provide a non-invasive tool for diagnosis and monitoring of disease progression or treatment efficacy in human medicine. However, collecting tears is demanding, and obtaining reproducible and unaltered samples is challenging because of the small sample volumes of tears. Several methods are available for tear collection as a preparatory step of precorneal tear film analysis, and the collection method used has to be assessed since it has a critical impact on the effectiveness of the assays and on the quality of the results. Each sampling method has advantages and disadvantages; therefore, it is not easy to choose the appropriate collecting method for tear collection. To overcome these limitations various methods have been recommended by different authors for special aspects of specific tests. The aim of our review was to evaluate tear sampling methods with regard to our ongoing biochemical analysis.