SARS-CoV-2 infectiousness is often determined by estimating the RNA viral load from the cycle threshold (Ct) value in the real-time reverse transcription-polymerase chain reaction (real time RT-PCR) assay. However, Ct value comparison among different assay methods is difficult. In addition, since detection of RNA does not always indicate the presence of infectious viruses, it is necessary to clarify the relationship between RNA viral loads and results of virus isolation to estimate the infectiousness of SARS-CoV-2.

In this study, we examined whether RNA quantification by a real time RT-PCR method is sufficient, without the necessity of nucleic acid purification, and compared it with the results obtained using the conventional method that requires nucleic acid purification. The RNA viral loads determined by the current method and the conventional method were compared with the results of virus isolation, and the effect of not performing nucleic acid purification was examined by the presence/absence of symptoms at the time of sample collection, to evaluate the relationship between the RNA viral load and results of virus isolation.

Our results indicated that our quantitative assay without nucleic acid purification exhibited good reproducibility, dilution linearity, and correlation with the result obtained using the conventional assay method, and that the measurement range was the same as that of the conventional method. Our findings suggested that the effect of not performing RNA purification was small. The results of both our current method and the conventional method were similar in relation to the results of virus isolation. There was a high possibility of negative viral isolation at <10⁴copies/mL and positive virus isolation at <10⁶copies/mL, and these values were useful for estimating the infectiousness. In specimens with 10⁴-10⁶copies/mL, infectious virus particles may be presumed to be present in the early infection stage in case the patient is symptomatic, while a high proportion of non-infectious virus particles could be present in asymptomatic cases.

The patient was a 70-year-old woman undergoing treatment for a nontuberculous mycobacterial (NTM) infection caused by Mycobacterium avium. She was diagnosed with adult T-cell leukemia/lymphoma (ATLL) after an abnormal increase in leukocyte count was noted. Micafungin was administered to prevent fungal infection, and allogeneic hematopoietic stem cell transplantation was performed. The patient developed a persistent fever starting on post-transplant Day 9, and Lomentospora prolificans was identified in a blood culture on Day 14. Despite treatment with antifungal agents, including voriconazole and terbinafine, the patient died on post-transplant Day 33. An autopsy was performed.

L. prolificans poses a significant infection risk to severely immunocompromised individuals, including patients with hematologic malignancies, hematopoietic stem cell transplant recipients, and solid organ transplant recipients. Treatment of L. prolificans infections is particularly challenging because of their rarity and the high resistance of L. prolificans to most available antifungal agents.

While a small number of L. prolificans infections associated with NTM have been documented, and the presence of pulmonary cavitary lesions has been suggested as a risk factor for L. prolificans infection, according to our literature review no cases ofL. prolificans infection associated with ATLL had ever been reported.

Clinicians should be alert to the possibility ofL.prolificans infection, especially in patients with an NTM infection who become severely immunocompromised, such as after a hematopoietic stem cell transplantation. Further research is urgently needed to develop and standardize effective treatment protocols for L. prolificans infection.

A 35-year-old man presented to a neighborhood clinic with mild pain in the right buttock in August 20XX. The physician suspected infection and referred the patient to our hospital for further evaluation and treatment. Pelvic Computed Tomography (CT) revealed a large abscess involving the right iliopsoas muscle and periphery of the hip joint, and we performed ultrasound-guided percutaneous drainage. Gram staining of the aspirated specimen revealed gram-negative filamentous rods. We had started the patient on empiric antibiotic therapy with cefazolin; however, based on the finding of Gram staining, the antibiotic regimen was escalated to piperacillin/tazobactam.

Due to challenges in bacterial identification by standard culture techniques, we referred the isolate to the Osaka Metropolitan University Hospital's Infection Control and Prevention Department for further analysis. Matrix-Assisted Laser Desorption Ionization-Time Of Flight Mass Spectrometry (MALDI-TOF MS) and 16S rRNA sequencing at that department identified Aggregatibacter aphrophilus as the causative organism.

The patient gave a history of dental treatment, which was suspected as the potential source of bacteremia leading to the formation of a perihip abscess. Appropriate management of such infections requires timely abscess drainage, accurate identification of the causative organism using susceptibility testing, and targeted antimicrobial therapy.