Cerebral abscess complicating Proteus mirabilis meningitis in a newborn infant

Could the Urease of the Gut Bacterium Proteus mirabilis Play a Role in the Altered Gut-Brain Talk Associated with Parkinson's Disease?

Intestinal dysbiosis seems to play a role in neurodegenerative pathologies. Parkinson's disease (PD) patients have an altered gut microbiota. Moreover, mice treated orally with the gut microbe Proteus mirabilis developed Parkinson's-like symptoms. Here, the possible involvement of P. mirabilis urease (PMU) and its B subunit (PmUreβ) in the pathogenesis of PD was assessed. Purified proteins were given to mice intraperitoneally (20 μg/animal/day) for one week. Behavioral tests were conducted, and brain homogenates of the treated animals were subjected to immunoassays. After treatment with PMU, the levels of TNF-α and IL-1β were measured in Caco2 cells and cellular permeability was assayed in Hek 293. The proteins were incubated in vitro with α-synuclein and examined via transmission electron microscopy. Our results showed that PMU treatment induced depressive-like behavior in mice. No motor deficits were observed. The brain homogenates had an increased content of caspase-9, while the levels of α-synuclein and tyrosine hydroxylase decreased. PMU increased the pro-inflammatory cytokines and altered the cellular permeability in cultured cells. The urease, but not the PmUreβ, altered the morphology of α-synuclein aggregates in vitro, forming fragmented aggregates. We concluded that PMU promotes pro-inflammatory effects in cultured cells. In vivo, PMU induces neuroinflammation and a depressive-like phenotype compatible with the first stages of PD development.

BACTERIAL IDENTIFICATION AND ANTIBIOTIC SENSITIVITY FROM THE ABSCESSES OF CAPTIVE TORTOISES-CLINICAL ANTIBIOTIC RECOMMENDATIONS

Bacterial abscesses are commonly seen in tortoises. The morbidity and the resultant mortality are high. Multifactorial problems, antibiotics misapplication. and antibiotic-resistant bacteria make abscess treatment complicated and ineffective. This study identifies the etiological bacterial species and determines the best antibiotics for abscess treatment in captive tortoises. Sterile swab specimens from 40 tortoises with abscesses were analyzed using the Analytical Profile Index (API) system. Sixty-five bacteria species were identified covering facultative anaerobic gram-negative (n = 30, 46.2%), facultative anaerobic gram-positive (n = 19, 29.2%), and aerobic gram-negative bacteria (n = 16, 24.6%). The antibiotic sensitivity of these bacteria to 30 antibiotics was assessed using the Kirby-Bauer disk-diffusion method. Greater than 80% anaerobic gram-negative bacterial species showed sensitivity to amikacin and ceftazidime. Greater than 80% anaerobic gram-positive bacterial species were sensitive to amoxicillin, ampicillin, carbenicillin, and penicillin. In addition, more than 80% aerobic gram-negative bacterial species were sensitive to ceftazidime, colistin sulphate, amikacin, gentamicin, kanamycin, polymyxin B, and tobramycin. This study provides clinicians significant information for initial antibiotic options, which could elevate the abscess therapy success rate and improve the life quality of tortoises.

Proteus mirabilis Urease: Unsuspected Non-Enzymatic Properties Relevant to Pathogenicity

Infection by Proteus mirabilis causes urinary stones and catheter incrustation due to ammonia formed by urease (PMU), one of its virulence factors. Non-enzymatic properties, such as pro-inflammatory and neurotoxic activities, were previously reported for distinct ureases, including that of the gastric pathogen Helicobacter pylori. Here, PMU was assayed on isolated cells to evaluate its non-enzymatic properties. Purified PMU (nanomolar range) was tested in human (platelets, HEK293 and SH-SY5Y) cells, and in murine microglia (BV-2). PMU promoted platelet aggregation. It did not affect cellular viability and no ammonia was detected in the cultures’ supernatants. PMU-treated HEK293 cells acquired a pro-inflammatory phenotype, producing reactive oxygen species (ROS) and cytokines IL-1β and TNF-α. SH-SY5Y cells stimulated with PMU showed high levels of intracellular Ca²⁺ and ROS production, but unlike BV-2 cells, SH-SY5Y did not synthesize TNF-α and IL-1β. Texas Red-labeled PMU was found in the cytoplasm and in the nucleus of all cell types. Bioinformatic analysis revealed two bipartite nuclear localization sequences in PMU. We have shown that PMU, besides urinary stone formation, can potentially contribute in other ways to pathogenesis. Our data suggest that PMU triggers pro-inflammatory effects and may affect cells beyond the renal system, indicating a possible role in extra-urinary diseases.

Ring-enhancing lesions in neonatal meningitis: an analysis of neuroradiology pitfalls through exemplificative cases and a review of the literature

Very often the clinical course of neonatal meningitis (NM) is characterized by sudden worsening, at times associated with cerebrovascular complications and strokes or the formation of cerebral abscesses. The immediate recognition of these pathological patterns is pivotal in providing clinicians with useful information to differentiate between those different pathological entities, which may both present as ring-enhancing lesions on neuroradiology investigations. Understanding their natural history and diagnostic features is of paramount importance to timely adopt the most appropriate medical and surgical management.

Ureases as multifunctional toxic proteins: A review

Ureases are metalloenzymes that hydrolyze urea into ammonia and carbon dioxide. They were the first enzymes to be crystallized and, with them, the notion that enzymes are proteins became accepted. Novel toxic properties of ureases that are independent of their enzyme activity have been discovered in the last three decades. Since our first description of the neurotoxic properties of canatoxin, an isoform of the jack bean urease, which appeared in Toxicon in 1981, about one hundred articles have been published on "new" properties of plant and microbial ureases. Here we review the present knowledge on the non-enzymatic properties of ureases. Plant ureases and microbial ureases are fungitoxic to filamentous fungi and yeasts by a mechanism involving fungal membrane permeabilization. Plant and at least some bacterial ureases have potent insecticidal effects. This entomotoxicity relies partly on an internal peptide released upon proteolysis of ingested urease by insect digestive enzymes. The intact protein and its derived peptide(s) are neurotoxic to insects and affect a number of other physiological functions, such as diuresis, muscle contraction and immunity. In mammal models some ureases are acutely neurotoxic upon injection, at least partially by enzyme-independent effects. For a long time bacterial ureases have been recognized as important virulence factors of diseases by urease-producing microorganisms. Ureases activate exocytosis in different mammalian cells recruiting eicosanoids and Ca(2+)-dependent pathways, even when their ureolytic activity is blocked by an irreversible inhibitor. Ureases are chemotactic factors recognized by neutrophils (and some bacteria), activating them and also platelets into a pro-inflammatory "status". Secretion-induction by ureases may play a role in fungal and bacterial diseases in humans and other animals. The now recognized "moonlighting" properties of these proteins have renewed interest in ureases for their biotechnological potential to improve plant defense against pests and as potential targets to ameliorate diseases due to pathogenic urease-producing microorganisms.

Brain abscesses in children: results of 24 children from a reference center in Central Anatolia, Turkey

Childhood brain abscesses are a rare and potentially life-threatening condition requiring urgent diagnosis and treatment. This retrospective study analyzed the clinical and radiologic findings of 24 (7 girl, 17 boys) cases with brain abscess. Mean age was 92.98 ± 68.04 months. The most common presenting symptoms were nausea-vomiting (45.8%) and headache (41.7%). Brain abscess was most commonly located in the frontal region. Diffusion restriction was determined in 78.4% of lesions. The mean apparent diffusion coefficient value in these lesions was 0.511 ± 0.23 × 10(-3) mm(2)/s. Cultures were sterile in 40% of cases. Antimicrobial therapy was given to only 16.7% of cases. Predisposing factors were identified in 91.6% of cases (congenital heart disease in 20.8% and immunosuppression in 20.8%). Mortality level was 12.5%. In conclusion, immunocompromised states, and congenital heart disease have become an important predisposing factor for brain abscesses. Effective and prompt management should ensure better outcome in childhood.

Neonatal deep white matter venous infarction and liquefaction: a pseudo-abscess lesion

BACKGROUND

Deep white matter hemorrhagic venous infarction with subsequent cavitation due to necrosis and liquefaction has been described in neonates and may be associated with infection and meningitis. In our experience, the MRI pattern of these lesions is confused with the pattern seen with cerebral abscesses.

OBJECTIVE

The purpose of our study was to characterize the MRI findings of post infarction necrosis and liquefaction after hemorrhagic deep white matter venous infarction in infants and to distinguish these lesions from cerebral abscesses.

MATERIALS AND METHODS

An institutional review board approved a retrospective review of imaging records to identify all patients with cerebral venous infarction at a children's hospital during a 10-year period. Nine infants had deep white matter hemorrhagic venous infarction with white matter fluid signal cavitary lesions. A diagnosis of cerebral abscess was considered in all. The imaging and laboratory findings in these patients are reviewed and compared to descriptions of abscesses found in the literature.

RESULTS

There were six female and three male infants. The mean age at presentation was 20 days (range: 0-90 days), while the corrected age at presentation was less than 30 days for all patients. Seven patients presented with seizures and signs of infection; one infant presented with lethargy and later proved to have protein C deficiency. MRI was performed 0-12 days from presentation in these eight patients. Another patient with known protein C deficiency underwent MRI at 30 days for follow-up of screening US abnormalities. There were a total of 38 deep cerebral white matter fluid signal cavitary lesions: 25 frontal, 9 parietal, 2 temporal, 2 occipital. Larger lesions had dependent debris. All lesions had associated hemorrhage and many lesions had evidence of adjacent small vessel venous thrombosis. Lesions imaged after gadolinium showed peripheral enhancement. Three lesions increased in size on follow-up imaging. Three patients, two with meningitis confirmed via microbiology and one with presumed meningitis by CSF counts, underwent surgical aspiration of a total of six lesions. All specimens were sent for pathology and culture and were negative for microorganisms.

CONCLUSION

Recognizing the MR appearance of cavitary necrosis and liquefaction after deep white matter cerebral venous infarction in neonates can distinguish this entity from cerebral abscess and potentially avoid an unnecessary neurosurgical aspiration procedure.

An autopsy case of otogenic intracranial abscess and meningitis with Bezold's abscess: evaluation of inflammatory bone destruction by postmortem cone-beam CT

The deceased was an unidentified young male found unconscious on a walkway. On autopsy, outer and inner fistulae of the left temporal bone, subcutaneous abscess in the left side of the neck and head, and an intracranial abscess were noted. A portion of the left temporal bone was removed and scanned by cone-beam computed tomography (CT) (normally used for dentistry applications) to evaluate the lesion. The cone-beam CT image revealed roughening of the bone wall and hypolucency of the mastoid air cells, consistent with an inflammatory bone lesion. According to autopsy and imaging findings, the cause of death was diagnosed as intracranial abscess with Bezold's abscess secondary to left mastoiditis as a complication of otitis media. Although determining the histopathology of bone specimens is time-consuming and costly work, we believe that use of cone-beam CT for hard tissue specimens can be useful in forensic practice.