J. Fungi 2024, 10(12), 812; https://doi.org/10.3390/jof10120812 - 22 Nov 2024
Abstract
Pythiosis, a rare and formidable infectious disease caused by Pythium insidiosum, is characterized by profound uncertainties in achieving definitive diagnoses, suboptimal outcomes, and an exceptionally high mortality rate. Here, we present a rare case of human spinal pythiosis in southern China. With
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Pythiosis, a rare and formidable infectious disease caused by Pythium insidiosum, is characterized by profound uncertainties in achieving definitive diagnoses, suboptimal outcomes, and an exceptionally high mortality rate. Here, we present a rare case of human spinal pythiosis in southern China. With advanced metagenomic sequencing technology, Pythium insidiosum was pinpointed as the causative pathogen. We discovered that the inoculation of either tissue fragments or homogenate yielded more successful results and enabled a moderate extension of the culture duration to 5–10 days through an exhaustive comparison of diverse inoculation and culture conditions for general clinical specimens. A pronounced genetic affinity of the isolated strain towards the Pythium insidiosum strain MCC 13 was detected after a comprehensive whole-genome sequencing analysis. Antifungal agents exhibited negligible sensitivity towards Pythium insidiosum in an antimicrobial susceptibility test. Conversely, antibacterial agents such as oxazolidinones, tetracyclines, macrolides, and amphenicols demonstrated varying degrees of sensitivity, albeit with most of their minimum inhibitory concentrations (MICs) substantially surpassing the safe concentration ranges for effective clinical treatment. Notably, tigecycline stood out as a promising candidate, exhibiting favorable therapeutic effects at moderate concentrations, making it a potential drug of choice for the control of pythiosis. A combined susceptibility test suggested that combinations of tetracyclines with macrolides, oxazolidinones, and amphenicols exhibited synergistic antibacterial effects, with the combination of doxycycline and trimethoprim–sulfamethoxazole (TMP-SMX) in particular playing a pivotal role. To our surprise, the MICs of iron chelators, specifically deferiprone and deferoxamine, against the strain were exceedingly low, which led to the speculation that exogenous iron chelators may have competitively inhibited the iron-chelating enzymes of the strain. The research derived from this single, rare case has certain limitations, but considering that there are currently no reports of invasive infections of deep organs in humans caused by Pythium insidiosum, the above findings can offer novel insights into the treatment of invasive pythiosis. Combination therapy based on tetracyclines, especially tigecycline, the use of TMP-SMX, and the adjunctive use of iron chelators, represent promising approaches to tackle the clinical challenges in the treatment of invasive pythiosis. However, further studies, including similar cases of spinal pythiosis and in vivo trials, are still needed to validate them. In addition, while paying attention to the therapeutic potentials of the above plans, we should also closely monitor the risks and side effects that may arise from excessive MICs or the expanded use of related drugs during the treatment process.
Full article
(This article belongs to the Section Fungal Pathogenesis and Disease Control)
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Figure 1
Figure 1
<p>MRI scan of cervical, thoracic, spine, and lumbar spine. (<b>A</b>) Pre-first surgery (November 2022). (<b>B</b>) Pre-second surgery (December 2022). (<b>C</b>) Pre-third surgery (October 2023). (<b>D</b>) Pre-fourth surgery (January 2024). (<b>E</b>) Follow-up imaging (February 2024).</p> Full article ">Figure 2
<p>Flowchart of the diagnosis and treatment.</p> Full article ">Figure 3
<p>Microbiological morphology of <span class="html-italic">Pythium insidiosum</span>. (<b>A</b>) Growth curve of the <span class="html-italic">Pythium insidiosum</span> inoculated onto LB agar plates. (<b>B</b>) Morphology of the strain after 4 days of incubation at 37 °C on a 90 mm LB agar plate. (<b>C</b>) Morphology of the mycelium observed under an optical microscope (400×). (<b>D</b>) A lactophenol cotton blue staining image of the mycelium (400×). (<b>E</b>) A fluorescence staining image of the mycelium (400×). (<b>F</b>) Induced zoospore formation in the mycelium observed under an optical microscope (400×). Arrow indicates that the motile spores transformed into spherical shapes, with the loss of flagella.</p> Full article ">Figure 4
<p>Cultivation of <span class="html-italic">Pythium insidiosum</span> (48–72 h). (<b>A</b>) Visible robust colony growth after mycelial plug inoculation. (<b>B</b>) Apparent colony growth after mycelial suspension inoculation. (<b>C</b>) No colony growth observed after spore suspension inoculation. (<b>D</b>) No colony growth observed after streak plate inoculation. (<b>E</b>) No colony growth observed after spread plate inoculation. (<b>F</b>) No colony growth observed after puncture inoculation.</p> Full article ">Figure 5
<p>The coverage map of the <span class="html-italic">Pythium insidiosum</span> strain MCC 13.</p> Full article ">Figure 6
<p>Phylogenetic trees show the phylogenetic position of the sample in this study within the evolutionary radiation of the genus <span class="html-italic">Pythium</span>. The highlighted red part represents the strain isolated from tissue biopsy, which showed stronger similarity with the <span class="html-italic">Pythium insidiosum</span> strain MCC 13 through blastn sequence alignment analysis.</p> Full article ">
<p>MRI scan of cervical, thoracic, spine, and lumbar spine. (<b>A</b>) Pre-first surgery (November 2022). (<b>B</b>) Pre-second surgery (December 2022). (<b>C</b>) Pre-third surgery (October 2023). (<b>D</b>) Pre-fourth surgery (January 2024). (<b>E</b>) Follow-up imaging (February 2024).</p> Full article ">Figure 2
<p>Flowchart of the diagnosis and treatment.</p> Full article ">Figure 3
<p>Microbiological morphology of <span class="html-italic">Pythium insidiosum</span>. (<b>A</b>) Growth curve of the <span class="html-italic">Pythium insidiosum</span> inoculated onto LB agar plates. (<b>B</b>) Morphology of the strain after 4 days of incubation at 37 °C on a 90 mm LB agar plate. (<b>C</b>) Morphology of the mycelium observed under an optical microscope (400×). (<b>D</b>) A lactophenol cotton blue staining image of the mycelium (400×). (<b>E</b>) A fluorescence staining image of the mycelium (400×). (<b>F</b>) Induced zoospore formation in the mycelium observed under an optical microscope (400×). Arrow indicates that the motile spores transformed into spherical shapes, with the loss of flagella.</p> Full article ">Figure 4
<p>Cultivation of <span class="html-italic">Pythium insidiosum</span> (48–72 h). (<b>A</b>) Visible robust colony growth after mycelial plug inoculation. (<b>B</b>) Apparent colony growth after mycelial suspension inoculation. (<b>C</b>) No colony growth observed after spore suspension inoculation. (<b>D</b>) No colony growth observed after streak plate inoculation. (<b>E</b>) No colony growth observed after spread plate inoculation. (<b>F</b>) No colony growth observed after puncture inoculation.</p> Full article ">Figure 5
<p>The coverage map of the <span class="html-italic">Pythium insidiosum</span> strain MCC 13.</p> Full article ">Figure 6
<p>Phylogenetic trees show the phylogenetic position of the sample in this study within the evolutionary radiation of the genus <span class="html-italic">Pythium</span>. The highlighted red part represents the strain isolated from tissue biopsy, which showed stronger similarity with the <span class="html-italic">Pythium insidiosum</span> strain MCC 13 through blastn sequence alignment analysis.</p> Full article ">
