Elizabethkingia miricola Causes Intracranial Infection: A Case Study

Immune Activation and Inflammatory Response Mediated by the NOD/Toll-like Receptor Signaling Pathway-The Potential Mechanism of Bullfrog (Lithobates catesbeiana) Meningitis Caused by Elizabethkingia miricola

Elizabethkingia miricola is an emerging opportunistic pathogen that is highly pathogenic in both immunocompromised humans and animals. Once the disease occurs, treatment can be very difficult. Therefore, a deep understanding of the pathological mechanism of Elizabethkingia miricola is the key to the prevention and control of the disease. In this study, we isolated the pathogenic bacteria from bullfrogs with dark skin color, weak limbs, wryneck, and cataracts. Via subsequent morphological observations and a 16S rRNA gene sequence analysis, the pathogen was identified as Elizabethkingia miricola. The histopathological and transmission electron microscopy analysis revealed that the brain was the main target organ. Therefore, brain samples from diseased and healthy bullfrogs were used for the RNA-Seq analysis. The comparative transcriptome analysis revealed that the diseased bullfrog brain was characterized by the immune activation and inflammatory response, which were mediated by the "NOD-like receptor signaling pathway" and the "Toll-like receptor signaling pathway". We also performed qRT-PCR to examine the expression profile of inflammation-related genes, which further verified the reliability of our transcriptome data. Based on the above results, it was concluded that the NOD/Toll-like receptor-related networks that dominate the immune activation and inflammatory response were activated in the brain of Elizabethkingia miricola-infected bullfrogs. This study contributes to the search for therapeutic targets for bullfrog meningitis and provides basic information for establishing effective measures to prevent and control bullfrog meningitis.

Natural occurrences and characterization of Elizabethkingia miricola infection in cultured bullfrogs (Rana catesbeiana)

Introduction

The bacterium Elizabethkingia miricola is a multispecies pathogen associated with meningitis-like disease that has been isolated from several amphibian species, including the bullfrog, but this is the first isolation in Guangxi. In the present study, the dominant bacteria were isolated from the brains of five bullfrogs with meningitis-like disease on a South China farm in Guangxi.

Methods

The NFEM01 isolate was identified by Gram staining; morphological observations; 16S rRNA, rpoB, and mutT-based phylogenetic tree analysis; and physiochemical characterization and was subjected to drug sensitivity and artificial infection testing.

Results and discussion

As a result of identification, the NFEM01 strain was found to be E. miricola. An artificial infection experiment revealed that NFEM01 infected bullfrogs and could cause symptoms of typical meningitis-like disease. As a result of the bacterial drug sensitivity test, NFEM01 is highly sensitive to mequindox, rifampicin, enrofloxacin, nitrofural, and oxytetracycline and there was strong resistance to gentamicin, florfenicol, neomycin, penicillin, amoxicillin, doxycycline, and sulfamonomethoxine. This study provides a reference to further study the pathogenesis mechanism of E. miricola-induced bullfrog meningitislike disease and its prevention and treatment.

Bullfrogs (Lithobates catesbeianus) as a Potential Source of Foodborne Disease

In Mexico, bullfrogs (Lithobates catesbeianus) are produced as gourmet food. However, bullfrogs can be carriers of pathogens because the frogs' preferred living conditions occur in stagnant water. The present study aimed to identify bacteria that cause foodborne diseases or are associated with human diseases. For molecular identification, based on the sequential analysis by 16S rRNA or rpoD was conducted on all isolates obtained from bullfrog. A total of 91 bacterial isolates were obtained from bullfrogs; 14 genera and 23 species were identified, including Acinetobacter johnsonii 16.5%; Aeromonas media 14.3%; Aeromonas veronii 13.2%; Providencia rettgeri 7.7%; Citrobacter freundii 6.6%; Aeromonas caviae 4.4%; Aeromonas hydrophila and Elizabethkingia ursingii 3.3%; Pseudomonas stutzeri, Raoultella ornithinolytica, and Shewanella putrefaciens 2.2%; Acinetobacter guillouiae, Acinetobacter pseudolwoffii, Citrobacter portucalensis, Citrobacter werkmanii, Edwardsiella anguillarum, Klebsiella michiganensis, Kluyvera intermedia, Kocuria rosea, Myroides odoratimimus, Myroides odoratus, Proteus sp., and Proteus hauseri 1.1%. In this study, 49.4% of the isolates obtained cause foodborne disease, 19.8% are bacteria that play an important role in the spoilage of food, 5.5% of isolates have nosocomial significance, 13.2% of bacteria are considered to be pollutants of the ecosystem, and in the case of A. salmonicida and Edwardsiella anguillarum (12.1%) to have a negative impact on aquaculture. Acinetobacter pseudolwoffii and Citrobacter portucalensis have not been reported to cause disease. Lastly of these isolates, 97.8% (89/91) can cause disease by food consumption or by direct contact for immunocompromised persons. The presence of these bacteria in bullfrogs represents a significant problem for human health. There is evidence that these microorganisms are pathogenic and frogs may also be reservoirs.

Septicemia caused by an emerging pathogen, Elizabethkingia miricola, in a laboratory colony of African dwarf frogs (Hymenochirus curtipes)

An outbreak of morbidity and mortality in an African dwarf frog (Hymenochirus curtipes) colony was reported following arrival at an animal research facility. Animals were found dead on arrival or became moribund shortly thereafter, and additional animals showed clinical signs of lethargy, weight loss, and anorexia over the following 3 weeks. Externally, some affected animals presented with multifocal areas of hyperemia in the inguinal and axillary areas and on the limbs, and mottled tan discoloration along the ventral abdomen. Histologically, lesions were consistent with generalized septicemia, characterized by granulomatous meningitis, otitis media, peritonitis (coelomitis), myocarditis and pericarditis, nephritis, pneumonia, and arthritis. Gram staining identified gram-negative rod-shaped bacteria free within tissues and within macrophages. Culture results of coelomic swabs identified moderate to numerous Elizabethkingia miricola. Testing of water from tanks housing affected animals showed elevated levels of nitrites and ammonia, and the presence of Citrobacter, Aeromonas, Pseudomonas, and Staphylococcus spp. cultured from several tank biofilters. E miricola is a newly recognized and rapidly emerging opportunistic pathogen in anurans and has been reported as a cause of septicemia in humans. This report documents the first occurrence of E. miricola septicemia in African dwarf frogs and illustrates the importance of this potential pathogen in the laboratory setting for amphibian research colonies, as well as those individuals directly working with them.

Acute bacterial encephalitis complicated with recurrent nasopharyngeal carcinoma associated with Elizabethkingia miricola infection: A case report

Elizabethkingia miricola (E. miricola) is an extremely rare pathogenic bacterium, which causes serious infections in patients with primary immunodeficiency or tumors, and it is often misdiagnosed. E. miricola has rarely been known to cause a neurologic infection. We describe the first case of acute bacterial encephalitis associated with E. miricola infection in a man with recurrent nasopharyngeal carcinoma, which was successfully cured by antibiotics. The patient initially presented with recurrent episodes of fever and later showed impaired consciousness but these symptoms were alleviated with antibiotic therapy including cefoperazone/sulbactam. This study highlights that rapid and accurate pathogen detection via metagenomic next-generation sequencing and early use of appropriate antibiotics can improve the prognosis of patients with suspected neurologic E. miricola infection. Early treatment for underlying primary diseases can also significantly improve the outcomes of patients.