Neonatal Citrobacter meningitis: pathogenesis of cerebral abscess formation

Second Trimester Fetal Loss Due to Citrobacter koseri Infection: A Rare Cause of Preterm Premature Rupture of Membranes (PPROM)

Citrobacter koseri is a facultative anaerobic, motile, non-spore-forming Gram-negative bacillus, which belongs to the family of Enterobacteriaceae. Severe infections due to Citrobacter spp. have been reported in the urinary tract, respiratory airways, intra-abdominal organs, skin and soft tissue, eye, bone, bloodstream, and central nervous system. In newborns, C. koseri is a well-known cause of meningitis, cerebral abscesses, brain adhesions, encephalitis, and pneumocephalus. Infection can be acquired through vertical maternal transmission or horizontal hospital settings; however, in many cases, the source is unknown. Preterm premature rupture of membranes (PPROM), caused by C. koseri, has rarely been described. Herein, we describe a case of PPROM at 16 weeks and 3 days of gestation, leading to anhydramnios. The parents opted for legal termination of the pregnancy, as the prognosis was very poor. C. koseri was isolated postmortem from a placental subamniotic swab and parenchymal sample, as well as fetal blood and lung. To the best of our knowledge, this is the first case of early second-trimester PPROM in which C. koseri infection was demonstrated.

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.

Neonatal cranial sonography: ultrasound findings in neonatal meningitis-a pictorial review

Neonatal bacterial meningitis is a common manifestation of late onset neonatal sepsis. Cranial sonography (CRS) has a crucial role in assessment of infants with clinical suspicion of bacterial meningitis as well as follows up of its complications. CRS is performed with high frequency transducer through anterior fontanelle in both coronal and sagittal planes. Various sonographic findings range from echogenic and widened sulci, ventriculomegaly, ventriculitis, hydrocephalus, extra-axial fluid collections, cerebritis and brain abscess. Sonography is extremely beneficial in evaluating intraventricular contents, especially debris and intraventricular septations. Linear high frequency probe along with color Doppler interrogation are of utmost importance in evaluating extra-axial fluid collection and helps differentiating it from benign subarachnoid space enlargement. Due to low cost, easy portability, speed of imaging, no need for sedation and above all lack of ionizing radiation make it superior to other cross sectional imaging, like CT and MRI, in evaluation of these sick neonates. Apart from textbooks, there is paucity of recently available literature on cranial sonographic findings in neonatal meningitis. This article is written with an educational intent to review the spectrum of findings in neonatal meningitis, with stress on findings that will be beneficial in the clinical practice.

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.

Citrobacter koseri meningitis: a neurosurgical condition?

A 2-month-old girl developed meningitis, ventriculitis and brain abscess in the course of Citrobacter koseri infection. She was successfully treated with the combined use of antibiotics, intra-cavitary urokinase and surgery, thus avoiding the development of hydrocephalus and of ventricular loculation. C. koseri is a Gram-negative pathogen with a strong predilection for the neonatal brain. Brain abscesses develop in roughly 77% of cases, causing severe neurological sequels in one-half and death in one-third of patients. The authors aim to report the role of neurosurgical treatment for managing the severe complications that may arise in the course of C. koseri brain infection and the use of urokinase for preventing the development of loculated hydrocephalus.

Sonographic findings in bacterial meningitis in neonates and young infants

Cranial sonography plays an important role in the initial evaluation of infants with suspected bacterial meningitis and in monitoring for complications of the disease. Echogenic widening of the brain sulci, meningeal thickening and hyperemia suggest the diagnosis in an at-risk population. Sonography can identify the presence of extra-axial fluid collections, and color Doppler sonography can be very helpful in differentiating benign enlargement of subarachnoid spaces from subdural effusions. Intraventricular debris and stranding, and an irregular and echogenic ependyma are highly suggestive findings associated with ventriculitis. Sonography can play an important role in the detection of postinfectious hydrocephalus, in the determination of the level of obstruction, and in the evaluation of intracranial compliance. Focal or diffuse parenchymal involvement can represent parenchymal involvement by cerebritis, infarction, secondary hemorrhage or early abscess.

Vertically acquired neonatal citrobacter brain abscess - case report and review of the literature

Vertically acquired citrobacter meningitis in the neonate is very rare and carries a very high mortality and morbidity. Overall, approximately 30% of neonates with Citrobacter meningitis die and 50% sustain some damage to the CNS. The authors describe a case of a newborn with Citrobacter koseri meningitis with multiple brain abscesses, with a successful outcome following multiple burr-hole aspirations and prolonged antibiotic therapy. An aggressive surgical approach combined with intravenous antibiotics (including imipenems, to which the organism is very sensitive) for a minimum of 4 weeks appears to improve the outcome of infection with this virulent organism.

Enterobacter sakazakii: a coliform of increased concern to infant health

The first cases of neonatal meningitis believed to have been caused by Enterobacter sakazakii were reported in 1961. Prompted by several subsequent outbreaks of E. sakazakii infections in neonates and an increasing number of neonates in intensive care units being fed rehydrated powdered infant formula, considered to be a source of the pathogen, public health authorities and researchers are exploring ways to eliminate the bacterium or control its growth in dry infant formula, processing environments and formula preparation areas in hospitals. Reviewed here are advances in taxonomy and classification of E. sakazakii, methods of detecting, isolating and typing the bacterium, antibiotic resistance, clinical etiology and pathogenicity. Outbreaks of E. sakazakii infections in neonates and adults are summarized. Reports on the presence of E. sakazakii in clinical settings, the environment and foods and food processing facilities are reviewed. Tolerance of the pathogen to environmental stresses, its behavior in powdered and rehydrated infant formulae and hazard analysis and risk management are discussed. Research needs are presented.

[The use of magnetic resonance and MR angiography in the detection of cerebral infarction--a complication of pediatric bacterial meningitis]

BACKGROUND

Association of both cerebral infarction and acute bacterial meningitis is more common in younger patients than in the elderly. The rate of mortality and the frequency of sequela are very high inspite of the use of modern antibiotic therapy. In more than 30% of the cases of childhood bacterial meningitis, both arterial and venous infarctions can occur. The aim of this study was to present the role of the use of magnetic resonance (MRI), and MR angiography (MRA) in the detection of bacterial meningitis in children complicated with cerebral infarctions.

METHOD

In the Centre for MR, the Clinical Centre of Serbia, 25 patients with the diagnosis of bacterial meningitis, of which 9 children with cerebral infarction whose clinical condition deteriorated acutely, despite the antibiotic therapy, underwent MRI and MR angiography examination on a 1T scanner. Examination included the conventional spin-echo techniques with T1-weighted saggital and coronal, and T2- weighted axial and coronal images. Coronal fluid attenuated inversion recovery (FLAIR) and the postcontrast T1-weighted images in three orthogonal planes were also used. The use MR angiography was accomplished by the three-dimensional time-of-flight (3D TOF) technique.

RESULTS

The findings included: multiple hemorrhagic infarction in 4 patients, multiple infarctions in 3 patients, focal infarction in 1 patient and diffuse infarction (1 patient). Common sites of involvement were: the frontal lobes, temporal lobes and basal ganglia. The majority of infarctions were bilateral. In 3 of the patients empyema was found, and in 1 patient bitemporal abscess was detected. In 8 of the patients MR angiography confirmed inflammatory vasculitis.

CONCLUSION

Infarction is the most common sequela of severe meningitis in children. Since the complication of cerebral infarction influences the prognosis of meningitis, repetitive MRI examinations are very significant for the evaluation of the time course of vascular involvement. The use of MRI, especially FLAIR imaging, confirmed its value in the detection and determination of the site and the extent of cerebral infarction. Non-invasive technique of examination, 3D TOF MR angiography clearly shoud show the presence of inflammatory vasculitis.

Pneumocephalus in neonatal meningitis: diffuse, necrotizing meningo-encephalitis in Citrobacter meningitis presenting with pneumatosis oculi and pneumocephalus

OBJECTIVE/PATIENT: Gas-containing encephalitis is rarely associated with neonatal meningitis. We report a case of a 19-day-old baby who presented with a rapid onset of septic shock complicated by progressively increasing gas accumulation within the brain and anterior chamber of the eye. We describe the evolution of the clinical picture and the management.

INTERVENTIONS

Ventilatory support, fluid resuscitation, and continuous venovenous hemofiltration were provided in view of multiple system failure. Despite effective antibiotic therapy and supportive management, the patient died with worsening accumulation of gas within the brain, resulting in brainstem death.

RESULTS

Computed tomographic images were characteristic of diffuse necrotizing meningo-encephalitis. Postmortem examination showed friable brain tissue with venous infarction and extensive gas accumulation. Citrobacter koseri was identified from the blood and cerebrospinal fluid cultures.

CONCLUSION

This case re-emphasises the importance of C. koseri as both a community-acquired and nosocomial neonatal pathogen. Radiologic evidence suggestive of diffuse necrotizing meningo-encephalitis in combination with pneumocephalus and pneumatosis oculi in Citrobacter infections has never been described before. Diagnostic imaging with computed tomographic scanning of the brain and initiation of broad-spectrum antibiotics with good penetration into cerebrospinal fluid are indicated as soon as infection with Citrobacter species is suspected clinically, with appearance of pneumatosis oculi as a rare, late finding.

Diffusion-weighted imaging in acute bacterial meningitis in infancy

Bacterial meningitis is frequently fatal or leads to severe neurological impairment. Complications such as vasculitis, resulting in infarcts, should be anticipated and dealt with promptly. Our aim was to demonstrate the complications of meningitis by diffusion weighted imaging (DWI) in patients who deteriorated despite therapy. We studied 13 infants between the ages of 1 day and 32 months who presented with symptoms ranging from fever and vomiting to seizures, encephalopathy and coma due to bacterial meningitis, performing MRI, including DWI, 2-5 days after presentation. Multiple infarcts were found on DWI in 12 of the 13, most commonly in the frontal lobes (in 10). Global involvement was seen in four children, three of whom died; the fourth had a very poor outcome. In one case abnormalities on DWI were due to subdural empyemas. We diagnosed vasculitis in three of five patients studied with MRA. We think DWI an important part of an MRI study in infants with meningitis. Small cortical or deep white-matter infarcts due to septic vasculitis can lead to tissue damage not easily recognized on routine imaging and DWI can be used to confirm that extra-axial collections represent empyemas.

Meningitis in the Neonate

Group B beta-hemolytic streptococci and Escherichia coli strains account for approximately two thirds of all cases of neonatal meningitis, while bacteria that typically account for meningitis in older age groups (Haemophilus influenzae type B, Neisseria meningitidis, and Streptococcus pneumoniae) are infrequent causes of meningitis in the neonatal population. As with other medical problems in neonates, signs and symptoms of bacterial infection of the central nervous system are generally few in number and nonspecific in nature. Manifestations that can suggest meningitis, as well as other serious illnesses, include temperature instability, lethargy, respiratory distress, poor feeding, vomiting, and diarrhea. Signs suggestive of meningeal irritation, including stiff neck, bulging fontanelle, convulsions, and opisthotonus, occur only in a minority of neonates with bacterial meningitis and cannot be relied on solely to identify such patients. Ampicillin and either gentamicin or cefotaxime are recommended for initial empiric therapy of neonatal meningitis. When the results of the cerebrospinal fluid (CSF) culture and susceptibilities are known, therapy can be narrowed to cover the specific pathogen identified. In general, penicillin G or ampicillin is preferred for group B streptococcal meningitis, ampicillin for Listeria monocytogenes meningitis, and ampicillin plus either an aminoglycoside or cefotaxime for gram-negative meningitis. For the very low birth weight neonate who has been in the nursery for a prolonged period of time, organisms such as enterococci and gentamicin-resistant gram-negative enteric bacilli must also be considered. In patients with long-term vascular catheters, Staphylococcus aureus or coagulase-negative staphylococci must also be considered. Empiric combinations of antibiotics for such patients would include ampicillin or vancomycin, plus amikacin or cefotaxime. All neonates should undergo repeat CSF examination and culture at 48 to 72 hours after initiation of therapy. If organisms are observed on gram stain, modification of the therapeutic regimen should be considered, and neuroimaging should be performed. In general, therapy should be continued for 14 to 21 days for neonatal meningitis caused by group B streptococci or L. monocytogenes, and for at least 21 days for disease caused by gram-negative enteric bacilli. All patients with neonatal meningitis should have hearing and development monitored serially. The first audiologic evaluation should occur 4 to 6 weeks after resolution of the meningitis.

Epidemiology of perinatal stroke

Perinatal stroke has become increasingly recognized, but the incidence is probably underestimated because of variation in the presentation, evaluation, and diagnosis. Based on estimates from population-based studies of infants with seizures, perinatal stroke occurs in approximately 1 in 4000 term births. Most perinatal strokes involve the middle cerebral artery and are caused by thromboembolism from an intracranial or extracranial vessel, the heart, or the placenta. Cardiac disorders, coagulation abnormalities, and infection are risk factors for stroke in the perinatal period. This article discusses the epidemiology of ischemic stroke occurring in the perinatal and neonatal period, including cerebrovascular events that are diagnosed during the perinatal period and those diagnosed retrospectively, when evidence of hemiparesis or postneonatal seizures leads to later evaluation and neuroimaging.

Enterobacter sakazakii infections among neonates, infants, children, and adults. Case reports and a review of the literature

Enterobacter sakazakii can cause serious infections especially among the very young and the elderly. It continues to be more common among neonates and infants than adults. Its tropism for the central nervous system in neonates and infants remains a mystery. Among neonates and infants, E. sakazakii has a propensity to cause meningitis resulting in ventriculitis, brain abscess or cyst formation, and development of hydrocephalus requiring ventricular-peritoneal shunt. Computed tomography of the head is therefore useful in following patients with E. sakazakii meningitis. Mortality and morbidity of E. sakazakii meningitis is high, and virtually all patients recovering from the central nervous system infection suffered mental and physical developmental delays. The case-fatality rate decreased among patients with meningitis treated with the third-generation cephalosporins. Most adults with E. sakazakii infection had serious underlying diseases and 50% of the adults with the infection had malignancies. However there has never been a known case of meningitis. Increasing antibiotic resistance among Enterobacter species should lead one to consider using the carbapenems or the newer cephalosporins in combination with a second agent such as an aminoglycoside. Limited data suggest that trimethoprim-sulfamethoxazole may be a useful agent in the treatment of infections caused by the Enterobacter species, especially in view of the production of extended-spectrum beta-lactamases capable of inactivating the cephalosporins and extended-spectrum penicillin.

Neuroimaging of postnatal pediatric central nervous system infections

Pediatric neuroimaging plays an important role in the timely diagnosis of postnatal central nervous system (CNS) infections, and in some patients the imaging findings are sufficiently specific to suggest a cause. The sequela of CNS infection, including hydrocephalus, subdural collections, ischemia/infarction, cerebral abscess, demyelination, and vascular thrombosis, can be accurately depicted and serially followed with current imaging techniques. The purpose of this review is to describe the spectrum of pediatric postnatal CNS infections, emphasizing key pathological and neuroimaging features, and to outline the strengths, weaknesses, and applications of current neuroimaging technology. The prenatal and perinatal infections falling under the designation of TORCH (toxoplasmosis, other [e.g., syphilis, HIV], rubella, cytomegalovirus, and herpes simplex II) are not covered.

Citrobacter meningitis in adults

Citrobacter meningitis is an uncommon infection of neonates and young children. It is rarely seen in adults. We describe a 46-year-old man with a mixed bacterial meningitis caused by C. diversus and Klebsiella oxytoca and a 64-year-old woman with C. freundii meningitis. Review of the English-language literature revealed only 2 adult patients with C. diversus meningitis and another 2, with C. freundii meningitis. The ages of these 6 aforementioned patients ranged from 31 to 84 years. Multiple facial fractures, neurosurgical procedures, alcoholism and diabetes mellitus were predisposing conditions. Among the 5 patients whose outcome was known, antibiotic therapy was successful in 4 but failed in 1. This study emphasizes that almost any of the gram-negative bacilli can cause serious infection of the central nervous system in adults in the proper setting.

Citrobacter diversus ventriculitis and brain abscesses in an adult

A case of Citrobacter diversus brain abscesses following urinary infection in an adult is described. The patient was treated with surgical drainage, netilmicin and cefotaxime. Citrobacter species CNS infection is discussed.

Pathophysiology of Citrobacter diversus neonatal meningitis: comparative studies in an infant mouse model

Citrobacter diversus is a cause of devastating neonatal meningitis, with illness characterized by formation of multiple brain abscesses. We developed an infant mouse intracranial inoculation model to evaluate the pathophysiology of C. diversus neonatal infections. Eighteen of 26 strains inoculated intracranially at a dose of ca. 3.3 x 10(3) CFU caused greater than 50% mortality in 2-day-old mice. No correlation was seen between the epidemiologic characteristics of a strain and its rate of mortality. When seven C. diversus isolates (four isolates from patients with meningitis, three from non-central nervous system [CNS] sites) were further evaluated, mortality was significantly correlated with bacteremia. The initial lesion in the CNS was a suppurative ventriculitis beginning 1 to 2 days postinoculation. Subsequent ventriculomegaly was associated with ventriculitis and periventricular abscessation. Brain lesions were seen with all strains, although strains of low virulence (as measured by having no bacteremia and low mortality) caused less-severe damage. An age-related susceptibility to C. diversus brain lesions was demonstrated, with 5-day-old mice showing a significant reduction in, and 8-day-old mice being apparently resistant to, infection and CNS damage. Our data indicate that C. diversus has a propensity to cause abscess formation in the neonatal mouse brain, with characteristic pathologic findings; however, the factors that determine whether a strain will cause meningitis in a human infant remain to be identified.

Brain abscess in childhood--long-term experiences

A retrospective evaluation was performed on 28 cases of paediatric brain abscess (male: female ratio 2.5:1; mean age 9.4 years; range 2.8-16 years) diagnosed between 1967 and 1987. In 46%, congenital cyanotic heart disease was identified as a predisposing factor, likewise sinusitis, otitis media or mastoiditis in 29% and immunodeficiency in 11%. Pathogenesis remained unclear in 14%. Initial symptoms and signs were predominantly nonspecific; loss of consciousness occurred in 32% of cases, neurological deficit and seizures each in 25%. Since the availability of CT, both diagnostic delay after hospital admission and mortality were substantially reduced: mean delay from 8.4 to 3.0 days, and mortality from 23% to 0%. Seventeen patients (61%) had follow up examinations 9.6 years (mean) after the acute illness (range 1-21 years). Neurological sequelae were diagnosed in 35% of cases, epilepsy in 29%, epileptic potentials during EEG in 12%, and CNS scars in 50%. Psychological testing revealed no statistically significant differences compared to normal populations. CNS scars, and epilepsy and/or epileptic potentials were more common after excision (7 patients) when compared to patients treated by aspiration and/or antibiotics alone (21 patients). It is concluded that excision of brain abscess should be avoided whenever possible. Therapy of choice consists of the administration of adequate antibiotics with or without CT-guided needle aspirations.

Cerebral infarctions due to CNS infection with Enterobacter sakazakii

Recent reports have implicated Enterobacter sakazakii, a gram-negative enteric bacillus, in neonatal sepsis and meningitis. Cases of severe central nervous system involvement, including ventriculitis, brain abscess, infarction, and cyst formation, have been described. We present serial head CT findings in a case of neonatal E. sakazakii meningitis complicated by a ring enhancing cerebral infarction which mimicked abscess formation. In meningitis secondary to this agent, a recognized pattern of cerebral hypodensity with or without cystic degeneration late in the course of the infection is likely to represent cerebral infarction rather than an abscess especially if there is a lack of culture evidence of a bacterial infection.

Brain abscesses in neonates. A study of 30 cases

Since the introduction of ultrasonography and computerized tomography (CT) scanning, brain abscesses are found more frequently in cases of neonatal meningitis and septicemia, particularly when the offending pathogen is Proteus. Thirty cases of brain abscess in neonates are reported, 27 of which were caused by Proteus species infections. Twenty infants had meningitis and 13 had septicemia. Most of the abscesses were enormous, and multiple abscesses were observed in 17 cases. The frontal region was involved in 22 cases (12 unilaterally and 10 bilaterally). The ventricles were enlarged on the first CT scan in 13 cases. The abscesses were treated by aspiration and antibiotics in 25 cases, and by antibiotics alone in five. A shunt for hydrocephalus was necessary in 14 infants. Four infants died, three from the initial illness and one from a shunt complication. Sixteen children have seizures. Subsequent intelligence quotient (IQ) testing was performed in 22 children: eight (36%) have an IQ at or above 80 and eight have an IQ of less than 60. In the 17 children followed for more than 2 years, the proportion with an IQ at or above 80 fell to 24% (four cases). The absence of initial seizures, sterile cerebrospinal fluid, normal ventricles on CT scans, and early aspiration of the abscess seem to be factors portending a better prognosis in terms of epilepsy and mental sequelae.

Update on bacterial meningitis

Recently, advances in identifying the etiologic agent, improving antibiotic therapy, and understanding the pathogenesis of complications of bacterial meningitis have been made. The acute and long-term sequelae and their courses have been documented. Acridine orange staining of the cerebrospinal fluid may identify bacteria in children with partially treated meningitis when gram-staining is not helpful. Monoclonal antibodies for meningococcus group B antigen have been developed and may prove useful for testing cerebrospinal fluid. Several newer cephalosporins have been shown to have excellent in vitro activity against the bacteria commonly associated with meningitis. They are indicated in the treatment of infants between 4 and 8 weeks of age, children in septic shock, children with liver disease, and children with infection with gram-negative enteric agents or bacteria resistant to ampicillin and chloramphenicol. Vasculitis and cerebral infarction may result in some of the complications, such as seizures and hemiparesis, noted in children, and their consequences can be documented by various neuroimaging procedures. The prognosis for ataxia is good, while that for sensorineural deafness is poor. The majority of children will have neither intellectual deficits nor difficulty with academic achievement. An effective vaccine against Haemophilus influenzae type b has been developed and is recommended for children between 18 and 60 months of age.