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Recently, the visible light communication (VLC) based on LEDs has attracted much attention. In this paper, in order to realize multi-user wireless communication for VLC-based indoor hybrid networks, a network selection method based on Multi Attribute Decision Making (MADM) is proposed, which effectively combines the subjective preference of the user with the objective performance of each network. And then, a VH-based (virtual handover) multi-user access scheme is proposed, which considers different MAC and channel information. Wherein, a concept of backoff lock is presented to control the access request of the user to different channels; a concept of VH is also put forward to reduce access delay, and improve access success ratio. When VH is triggered, the user can use the backoff lock to lock the current access request and send access request to other networks. The expressions of collision probability, access delay, and access success ratio are given. Analytical and simulation results show that the proposed network selection method can effectively meet the users' requirement, and the evaluation value obtained by our method is also in accordance with the objective network performance, and that the VH-based multi-user access scheme can reduce the collision probability and the access delay, and increase the access success ratio for VLC-based hybrid networks.
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Background: Rickettsia felis is a kind of zoonotic pathogen. Rickettsia felis infections of the central nervous system are rare with only a few cases reported worldwide. The early diagnosis of R. felis is difficult due to its nonspecific clinical features and laboratory tests. Here, we report two meningitis cases caused by R. felis using metagenomic next-generation sequencing (mNGS). Methods: The clinical data of patients with meningitis who were diagnosed to have R. felis through cerebrospinal fluid culture, nuclear magnetic imaging, mNGS detection from January 2019 to December 2019 in The First Clinical Hospital of Shanxi Medical University, were retrospectively analyzed, and their clinical characteristics and disease regression findings were summarized. Case Presentation: The first case was a female patient aged 23 years who was admitted to our hospital presenting with symptoms of headache, fever, and weakness in both lower limbs. Upon examination of spinal imaging, myelitis was diagnosed. However, routine examination and culture of cerebrospinal fluid did not identify the pathogen responsible. Subsequently, metagenomic second-generation sequencing (mNGS) revealed that the infection was caused by R. felis. The patient responded well to standard treatment and showed signs of recovery. The second case was a male patient aged 29 years who was admitted to our hospital with a headache and fever that had persisted for 4 days within a month. Routine examination and culture of the cerebrospinal fluid did not reveal any identifiable pathogens. However, metagenomic second-generation sequencing (mNGS) determined that the patient had a Rickettsial infection likely transmitted by a cat. The patient showed significant improvement after 14 days of doxycycline treatment. Tests for herpes simplex virus, cytomegalovirus, Epstein-Barr virus and tubercle bacillus nucleic acid in the CSF and blood were negative.Therefore mNGS of the cerebrospinal fluid was used, which identified the pathogen as R. felis. One case was diagnosed as subacute meningitis with immune-associated myelitis and the other as subacute meningitis. Conclusion: mNGS of cerebrospinal fluid can be used as a fast and effective method to identify intracranial R. felis infections.
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BACKGROUND: Intracranial Listeria infections are common in newborns and immunocompromised individuals, but brainstem abscesses are rare. CASE SUMMARY: We report a rare case of brainstem abscesses caused by Listeria monocytogenes in a previously healthy adult patient. The patient's magnetic resonance imaging examination showed multiple brain abscesses, and his second cerebrospinal fluid culture test indicated the presence of Listeria monocytogenes. Despite early empirical therapy, the patient's condition progressively deteriorated. Because the patient's abscesses were located in the brainstem and multiple lobes, surgery was not possible. The patient died 40 d after admission. CONCLUSION: This case highlights the importance of rational clinical use of drugs to avoid potentially serious infectious complications.