Caspase-3 mediates hippocampal apoptosis in pneumococcal meningitis

Bacterial meningitis causes neuronal apoptosis in the hippocampal dentate gyrus, which is associated with learning and memory impairments after cured disease. The execution of the apoptotic program involves pathways that converge on activation of caspase-3, which is required for morphological changes associated with apoptosis. Here, the time course and the role of caspase-3 in neuronal apoptosis was assessed in an infant rat model of pneumococcal meningitis. During clinically asymptotic meningitis (0-12 h after infection), only minor apoptotic damage to the dentate gyrus was observed, while the acute phase (18-24 h) was characterized by a massive increase of apoptotic cells, which peaked at 36 h. In the subacute phase of the disease (36-72 h), the number of apoptotic cells decreased to control levels. Enzymatic caspase-3 activity was significantly increased in hippocampal tissue of infected animals compared to controls at 22 h. The activated enzyme was localized to immature cells of the dentate gyrus, and in vivo activity was evidenced by cleavage of the amyloid-beta precursor protein. Intracisternal administration of the caspase-3-specific inhibitor Ac-DEVD-CHO significantly reduced apoptosis in the hippocampal dentate gyrus. In contrast to a study where the decrease of hippocampal apoptosis after administration of a pan-caspase inhibitor was due to downmodulation of the inflammatory response, our data demonstrate that specific inhibition of caspase-3 did not affect inflammation assessed by TNF-alpha and IL-1beta concentrations in the cerebrospinal fluid space. Taken together, the present results identify caspase-3 as a key effector of neuronal apoptosis in pneumococcal meningitis.

[Septic arthritis due to Streptococcus pneumoniae]

INTRODUCTION

There are few reports of Streptococcus pneumoniae as a cause of septic arthritis. The aim of this study was to describe our experience with five documented cases of pneumococcal arthritis over 14 years.

METHODS

The medical histories of infectious septic arthritis in our center between January 1986 and December 2000 were retrospectively reviewed. Cases of pneumococcal etiology were analyzed while those occurring in the neonatal and immediate postoperative periods were excluded.

RESULTS

Among the 39 documented cases of septic arthritis, 5 (12.8 %) were caused by Streptococcus pneumoniae. Four of the patients were younger than 15 months old. Fever without localizing signs as an antecedent was present in four patients; of these, one patient had concurrent otitis media. The most common localization was the hip (four patients) and the knee (one patient). In three patients simple radiology showed no abnormalities while in four ultrasonography showed abnormalities. Etiologic diagnosis was established by isolation of S. pneumoniae from blood culture and synovial fluid (one patient), from blood culture (one patient), from synovial fluid (two patients), and by detection of pneumococcal antigen in urine (one patient). Of the germs isolated, two showed reduced susceptibility to penicillin (CMI 0.125-1 mg/l) and all were susceptible to cefotaxime. Open drainage was performed in all patients with hip involvement. None of the patients presented sequelae.

CONCLUSIONS

In our experience, S. pneumoniae should be taken into account as a cause of septic arthritis that mainly affects children younger than 15 months. The hip was the most frequently involved joint. Joint fluid culture was the method providing the best diagnostic yield. A high proportion of strains are not susceptible to penicillin. Early diagnosis and management lead to a good prognosis.

[A comparative experimental study between recombinant active gene 1-deficient mice and C57BL/6 mice model of acute bacterial rhinosinusitis]

OBJECTIVE

To explore the infective course of acute bacterial rhinosinusitis in recombinent active gene 1 (Rag 1)-defecient mice (Rag1) and C57BL/6 mice (C57) and the difference between them after intranasal streptococcus pneumoniae inoculation.

METHODS

Ten mice of each strain (Rag1 and C57) received Streptococcus pneumoniae strain T59, ATCC 49,619 suspended in trypticase soy broth, and controls (two mice for each strain) received trypticase soy broth alone. After 2, 5, 10 and 14 days, nasal lavage cultures were obtained and then the mice were killed. The heads were embedded with paraffin and serial sections were made for histological analysis. The percentage of sinus cavity occupied by neutrophil cluster (% cluster) and the number of polymorphonuclear leukocytes per square millimeter of sinus mucosa (PMN/mm2) were calculated by the use of a computer-aided microscope in conjunction with a reconstruction and image analysis system.

RESULTS

% Cluster and PMN/mm2 in infected mice both of Rag1 and C57 appeared to peak on five and ten days separately, which were significantly heavier than those in controls(P < 0.05). The infection in C57 decreased by two weeks. But in contrast to C57, the infection in Rag1 had not been controlled and Streptococcus pneumoniae were still seen in the nasal lavage culture by two weeks. This difference between infected Rag1 and infected C57 was significant at P < 0.05.

CONCLUSION

Acute bacterial rhinosinusitis in Rag1 and C57 mice were successfully induced by intranasal inoculation of streptococcus pneunoniae. This bacterial infection in C57 could be controlled completely and rapidly. In contrast, Rag1 failed to control rhinosinusitis and had a tendency to chronic inflammation, suggesting that T- and B-cell-dependent immunity was important for clearance of bacteria from rhinosinus and gene knockout mice was a convenient tool for investigation of the pathogenesis of experimental rhinosinusitis.

Acute severe spinal cord dysfunction in bacterial meningitis in adults: MRI findings suggest extensive myelitis

BACKGROUND

Bacterial meningitis is rarely complicated by acute spinal cord involvement (eg, myelitis, ischemic infarction, spinal abscess, or epidural hemorrhage). In spinal cord dysfunction, magnetic resonance imaging (MRI) is the imaging modality of choice. Still, MRI findings of myelitis due to bacterial meningitis in adults have not been reported.

METHODS

Spinal MRIs were obtained during the acute stage of meningitis and on follow-up in 3 adults with bacterial meningitis that was complicated by paraparesis or tetraparesis and bowel and bladder incontinence. The causative pathogens were Streptococcus pneumoniae and Neisseria meningitidis; in 1 patient, the pathogen was not identified.

RESULTS

In all cases, spinal MRI ruled out a compression of the cord by an extramedullary mass but demonstrated hyperintensities on T2-weighted images that predominantly involved the gray matter and extended from the cervical to the lumbar cord. Leptomeningeal and discrete nodular intramedullary enhancement on T1-weighted images was detected only in 1 patient. Follow-up examinations revealed that hyperintensities resolved completely in 1 patient, while a central cavitation developed in the cervical spinal cord of another, and the MRI findings were progressive during the first 4 weeks in the third patient. In all cases, severe paresis and bowel and bladder incontinence persisted.

CONCLUSION

We demonstrate for the first time the MRI findings of adults with acute spinal cord involvement during bacterial meningitis. Magnetic resonance imaging showed central intramedullary hyperintensities on T2-weighted images that extended from the cervical to the lumbar cord, indicating myelitis. Clinical follow-up examinations suggest that myelitis during bacterial meningitis has an unfavorable prognosis.

Factor H and the pathogenesis of renal diseases

Complement factor H is a potent inhibitor of alternative pathway complement activation. The factor H gene, a member of the regulators of complement activation (RCA) gene cluster, encodes two plasma proteins, one 150 kilodaltons (kDa) and one 43 kDa. Homozygous deficiency of factor H results in low plasma levels of complement factor B and C3 and depletion of the terminal complement proteins C5-C9; heterozygotes may have reduced or normal levels of factor B, C3, and C5-C9. Although factor H deficiency is infrequently reported, it has been associated with a number of types of renal disease, the most common being atypical membranoproliferative glomerulonephritis and idiopathic (non-diarrhea-associated) hemolytic uremic syndrome (HUS). The molecular defects responsible for factor H deficiency have been described in only two cases; clearly more research is needed in this area. The possible role of factor H deficiency or dysfunction in the pathogenesis of HUS is discussed.

Unusual manifestations of invasive pneumococcal infection

Unusual pneumococcal infections occurred frequently in the preantibiotic age but rapidly declined with the advent of the antibiotic era. Unfortunately, the morbidity and mortality associated with invasive pneumococcal disease remain high despite antibiotic therapy and monumental advances in medical technology. The incidence of invasive pneumococcal disease has increased recently because of the onset of the human immunodeficiency virus (HIV) epidemic and the emergence of antibiotic-resistant pneumococcus. Robert Austrian described the clinical triad of pneumococcal pneumonia, meningitis, and endocarditis, a syndrome that now bears his name. Although seen infrequently today, unusual manifestations of pneumococcal infection such as those Austrian reported still occur. A review of these cases is warranted because, as drug-resistant organisms continue to emerge worldwide, more unusual pneumococcal infections will be seen. Streptococcus pneumoniae is responsible for a remarkable array of disease processes; our literature review uncovered 95 different types of unusual pneumococcal infections representing 2,064 cases. Examples of these infections included pancreatic and liver abscesses, aortitis, gingival lesions, phlegmonous gastritis, inguinal adenitis, testicular and tubo-ovarian abscesses, and necrotizing fasciitis. We also reviewed predisposing underlying illnesses and conditions. Alcoholism, HIV infection, splenectomy, connective tissue disease, steroid use, diabetes mellitus, and intravenous drug use remain common risk factors for invasive pneumococcal infections. Currently, multidrug-resistant S. pneumoniae remains susceptible to vancomycin and several new third-generation fluoroquinolones. As what some fear will be a possible postantibiotic era approaches, clinicians must be able to recognize and manage unusual pneumococcal infections.

[Austrian's syndrome (endocarditis, meningitis and pneumonia caused by Streptococcus pneumoniae). Apropos of a rare case]

We report a case of a mitral endocarditis caused by Streptococcus pneumoniae in a 48 year old man diagnosed with moderate mitral stenosis and liver cirrhosis. The clinical features were fever with penicillin-sensitive pneumococcal bacteremia, meningitis and pneumonia. Only transesophageal echocardiography could confirm the presence of vegetations. In spite of vancomycin therapy, the patient required mitral valve replacement, with good results. Some clinical aspects of this uncommon cause of infective endocarditis are discussed.

Pneumococci stimulate the production of the inducible nitric oxide synthase and nitric oxide by murine macrophages

The role of nitric oxide (NO) in the pathophysiology of gram-positive sepsis is uncertain. In inflammatory conditions, high-output NO production is catalyzed by the enzyme inducible nitric oxide synthase (iNOS). The ability of 2 strains of pneumococci, pneumococcal cell wall preparations, and purified pneumococcal capsule (Pnu-Imune 23) to trigger the production of iNOS protein and NO in RAW 264.7 murine macrophages was tested. Live pneumococci, oxacillin-killed pneumococci, and pneumococcal cell wall preparations stimulated the production of iNOS and NO by RAW 264.7 cells in the presence, but not the absence, of low concentrations of recombinant murine interferon-gamma. In contrast, purified pneumococcal capsule induced little or no iNOS or NO production by these cells. Thus, pneumococci stimulate high-output NO production by murine macrophages. The potential role of NO in the pathogenesis of pneumococcal sepsis deserves further study.