Lipopolysaccharide structure modulates cationic biocide susceptibility and crystalline biofilm formation in Proteus mirabilis

Chlorhexidine (CHD) is a cationic biocide used ubiquitously in healthcare settings. Proteus mirabilis, an important pathogen of the catheterized urinary tract, and isolates of this species are often described as "resistant" to CHD-containing products used for catheter infection control. To identify the mechanisms underlying reduced CHD susceptibility in P. mirabilis, we subjected the CHD tolerant clinical isolate RS47 to random transposon mutagenesis and screened for mutants with reduced CHD minimum inhibitory concentrations (MICs). One mutant recovered from these screens (designated RS47-2) exhibited ~ 8-fold reduction in CHD MIC. Complete genome sequencing of RS47-2 showed a single mini-Tn5 insert in the waaC gene involved in lipopolysaccharide (LPS) inner core biosynthesis. Phenotypic screening of RS47-2 revealed a significant increase in cell surface hydrophobicity and serum susceptibility compared to the wildtype, and confirmed defects in LPS production congruent with waaC inactivation. Disruption of waaC was also associated with increased susceptibility to a range of other cationic biocides but did not affect susceptibility to antibiotics tested. Complementation studies showed that repression of smvA efflux activity in RS47-2 further increased susceptibility to CHD and other cationic biocides, reducing CHD MICs to values comparable with the most CHD susceptible isolates characterized. The formation of crystalline biofilms and blockage of urethral catheters was also significantly attenuated in RS47-2. Taken together, these data show that aspects of LPS structure and upregulation of the smvA efflux system function in synergy to modulate susceptibility to CHD and other cationic biocides, and that LPS structure is also an important factor in P. mirabilis crystalline biofilm formation.

De-repression of the smvA efflux system arises in clinical isolates of Proteus mirabilis and reduces susceptibility to chlorhexidine and other biocides

Proteus mirabilis is a common pathogen of the catheterised urinary tract and often described as intrinsically resistant to the biocide chlorhexidine (CHD). Here we demonstrate that de-repression of the smvA efflux system has occurred in clinical isolates of P. mirabilis and reduces susceptibility to CHD and other cationic biocides. Compared to other isolates examined, P. mirabilis RS47 exhibited a significantly higher CHD MIC (≥512 μg/ml) and significantly greater expression of smvA. Comparison of the RS47 smvA and cognate smvR repressor with sequences from other isolates, indicated that RS47 encodes an inactivated smvR. Complementation of RS47 with a functional smvR from isolate RS50a (which exhibited the lowest smvA expression and lowest CHD MIC) reduced smvA expression by ∼59-fold, and markedly lowered the MIC of CHD and other cationic biocides. Although complementation of RS47 did not reduce MICs to concentrations observed in isolate RS50a, the significantly lower polymyxin B MIC of RS50a indicated that differences in LPS structure are also a factor in P. mirabilis CHD susceptibility. To determine if exposure to CHD can select for mutations in smvR, clinical isolates with the lowest CHD MICs were adapted to grow at increasing concentrations of CHD up to 512 μg/ml. Analysis of the smvR in adapted populations indicated that mutations predicted to inactivate smvR occurred following CHD exposure in some isolates. Collectively, our data show that smvA de-repression contributes to reduced biocide susceptibility in P. mirabilis, but differences in LPS structure between strains are also likely to be an important factor.

Bacterial biofilm formation on indwelling urethral catheters

Urethral catheters are the most commonly deployed medical devices and used to manage a wide range of conditions in both hospital and community care settings. The use of long-term catheterization, where the catheter remains in place for a period >28 days remains common, and the care of these patients is often undermined by the acquisition of infections and formation of biofilms on catheter surfaces. Particular problems arise from colonization with urease-producing species such as Proteus mirabilis, which form unusual crystalline biofilms that encrust catheter surfaces and block urine flow. Encrustation and blockage often lead to a range of serious clinical complications and emergency hospital referrals in long-term catheterized patients. Here we review current understanding of bacterial biofilm formation on urethral catheters, with a focus on crystalline biofilm formation by P. mirabilis, as well as approaches that may be used to control biofilm formation on these devices. SIGNIFICANCE AND IMPACT OF THE STUDY: Urinary catheters are the most commonly used medical devices in many healthcare systems, but their use predisposes to infection and provide ideal conditions for bacterial biofilm formation. Patients managed by long-term urethral catheterization are particularly vulnerable to biofilm-related infections, with crystalline biofilm formation by urease producing species frequently leading to catheter blockage and other serious clinical complications. This review considers current knowledge regarding biofilm formation on urethral catheters, and possible strategies for their control.

Prototype Development of the Intelligent Hydrogel Wound Dressing and Its Efficacy in the Detection of Model Pathogenic Wound Biofilms

The early detection of wound infection in situ can dramatically improve patient care pathways and clinical outcomes. There is increasing evidence that within an infected wound the main bacterial mode of living is a biofilm: a confluent community of adherent bacteria encased in an extracellular polymeric matrix. Here we have reported the development of a prototype wound dressing, which switches on a fluorescent color when in contact with pathogenic wound biofilms. The dressing is made of a hydrated agarose film in which the fluorescent dye containing vesicles were mixed with agarose and dispersed within the hydrogel matrix. The static and dynamic models of wound biofilms, from clinical strains of Escherichia coli, Pseudomonas aeruginosa, Staphylococcus aureus, and Enterococcus faecalis, were established on nanoporous polycarbonate membrane for 24, 48, and 72 h, and the dressing response to the biofilms on the prototype dressing evaluated. The dressing indicated a clear fluorescent/color response within 4 h, only observed when in contact with biofilms produced by a pathogenic strain. The sensitivity of the dressing to biofilms was dependent on the species and strain types of the bacterial pathogens involved, but a relatively higher response was observed in strains considered good biofilm formers. There was a clear difference in the levels of dressing response, when dressings were tested on bacteria grown in biofilm or in planktonic cultures, suggesting that the level of expression of virulence factors is different depending of the growth mode. Colorimetric detection on wound biofilms of prevalent pathogens (S. aureus, P. aeruginosa, and E. faecalis) is also demonstrated using an ex vivo porcine skin model of burn wound infection.

Increased Prevalence of Developmental Venous Anomalies in Children with Intracranial Neoplasms

BACKGROUND AND PURPOSE

Developmental venous anomalies are considered variants of venous development that, in and of themselves, are of little clinical import. A possible association between intrinsic brain tumors and developmental venous anomalies has been suggested, but a rigorous investigation has not been performed. The aim of this study was to assess any association between developmental venous anomalies and intrinsic brain neoplasms.

MATERIALS AND METHODS

A radiology report text search of terms used to describe developmental venous anomalies was performed on a study population of 580 patients with primary intracranial neoplasms and on a control population of 580 patients without neoplasms from the same time period. All positive results were reviewed to confirm that the report was describing a developmental venous anomaly, and the imaging examination was reviewed to confirm the diagnosis.

RESULTS

Fifty-nine of the 580 subjects with brain tumors (10.17%) had a developmental venous anomaly identified by report and confirmed on review of the imaging. Thirty-one of the 580 controls (5.34%) had a developmental venous anomaly identified by report and confirmed on review of the imaging (P = .003). No statistically significant difference was noted in the prevalence of developmental venous anomalies among tumor types. No developmental venous anomaly drained the vascular territory of the tumor, and there was no correlation between the location of the developmental venous anomaly and the location of the neoplasm.

CONCLUSIONS

The prevalence of developmental venous anomalies in this pediatric population with intracranial primary neoplasms is significantly greater than in those without neoplasms, suggesting an association that may be related to shared causative factors or susceptibilities to the development of these 2 separate entities.

Brain parenchymal signal abnormalities associated with developmental venous anomalies in children and young adults

BACKGROUND AND PURPOSE

Abnormal signal in the drainage territory of developmental venous anomalies has been well described in adults but has been incompletely investigated in children. This study was performed to evaluate the prevalence of brain parenchymal abnormalities subjacent to developmental venous anomalies in children and young adults, correlating with subject age and developmental venous anomaly morphology and location.

MATERIALS AND METHODS

Two hundred eighty-five patients with developmental venous anomalies identified on brain MR imaging with contrast, performed from November 2008 through November 2012, composed the study group. Data were collected for the following explanatory variables: subject demographics, developmental venous anomaly location, morphology, and associated parenchymal abnormalities. Associations between these variables and the presence of parenchymal signal abnormalities (response variable) were then determined.

RESULTS

Of the 285 subjects identified, 172 met inclusion criteria, and among these subjects, 193 developmental venous anomalies were identified. Twenty-six (13.5%) of the 193 developmental venous anomalies had associated signal-intensity abnormalities in their drainage territory. After excluding developmental venous anomalies with coexisting cavernous malformations, we obtained an adjusted prevalence of 21/181 (11.6%) for associated signal-intensity abnormalities in developmental venous anomalies. Signal-intensity abnormalities were independently associated with younger subject age, cavernous malformations, parenchymal atrophy, and deep venous drainage of developmental venous anomalies.

CONCLUSIONS

Signal-intensity abnormalities detectable by standard clinical MR images were identified in 11.6% of consecutively identified developmental venous anomalies. Signal abnormalities are more common in developmental venous anomalies with deep venous drainage, associated cavernous malformation and parenchymal atrophy, and younger subject age. The pathophysiology of these signal-intensity abnormalities remains unclear but may represent effects of delayed myelination and/or alterations in venous flow within the developmental venous anomaly drainage territory.

White matter microstructural abnormality in children with hydrocephalus detected by probabilistic diffusion tractography

BACKGROUND AND PURPOSE

Hydrocephalus is a severe pathologic condition in which WM damage is a major factor associated with poor outcomes. The goal of the study was to investigate tract-based WM connectivity and DTI measurements in children with hydrocephalus by using the probabilistic diffusion tractography method.

MATERIALS AND METHODS

Twelve children with hydrocephalus and 16 age-matched controls were included in the study. Probabilistic diffusion tractography was conducted to generate tract-based connectivity distribution and DTI measures for the genu of the corpus callosum and the connectivity index. Tract-based summary measurements, including the connectivity index and DTI measures (fractional anisotropy, mean diffusivity, axial diffusivity, and radial diffusivity), were calculated and compared between the 2 study groups.

RESULTS

Tract-based summary measurement showed a higher percentage of voxels with lower normalized connectivity index values in the WM tracts in children with hydrocephalus. In the genu of the corpus callosum, the left midsegment of the corticospinal tract, and the right midsegment of the corticospinal tract, the normalized connectivity index value in children with hydrocephalus was found to be significantly lower (P < .05, corrected). The tract-based DTI measures showed that the children with hydrocephalus had significantly higher mean diffusivity, axial diffusivity, and radial diffusivity in the genu of the corpus callosum, left midsegment of the corticospinal tract, and right midsegment of corticospinal tract and lower fractional anisotropy in the genu of the corpus callosum (P < .05, corrected).

CONCLUSIONS

The analysis of WM connectivity showed that the probabilistic diffusion tractography method is a sensitive tool to detect the decreased continuity in WM tracts that are under the direct influence of mechanical distortion and increased intracranial pressure in hydrocephalus. This voxel-based connectivity method can provide quantitative information complementary to the standard DTI summary measures.

Diffusion tensor imaging properties and neurobehavioral outcomes in children with hydrocephalus

BACKGROUND AND PURPOSE

White matter structural alterations and the correlation with neuropsychological deficits in children with hydrocephalus have not been well investigated. In this prospective study, the objectives were the following: 1) to apply DTI to detect in vivo white matter alterations based on diffusion properties in children with acute hydrocephalus, 2) to quantify early neuropsychological deficits, and 3) to explore the correlation between potential neuropsychological deficits and abnormalities in functionally related white matter.

MATERIALS AND METHODS

A total of 44 children, 24 with hydrocephalus and 20 controls, were enrolled in the study. DTI indices, FA, MD, AD, and RD, were evaluated in the gCC, sCC, PLIC, and ALIC. The ABAS-II was used as a broad screener of development, including conceptual, social, practical, and motor skills. The correlation between the Motor Scale and DTI indices in the PLIC was analyzed.

RESULTS

DTI analyses showed that the gCC and sCC in children with hydrocephalus had lower FA and higher MD, driven by the increased RD with statistical significance (P < .05) or trend-level significance (P = .06). The PLIC and ALIC had significantly higher AD in children with hydrocephalus (P < .05). On the ABAS-II, parent ratings of general adaptive skills, conceptual skills, and motor skills were significantly lower in children with hydrocephalus (all at P < .05). The MD and RD values in the PLIC were found to have trend-level or significant correlation with the Motor Scale (P = .057, .041, respectively).

CONCLUSIONS

DTI reveals alterations in the white matter structure in children with hydrocephalus with preliminary findings suggesting correlation with clinical motor deficits.

DTI values in key white matter tracts from infancy through adolescence

BACKGROUND AND PURPOSE

DTI is an advanced neuroimaging technique that allows in vivo quantification of water diffusion properties as surrogate markers of the integrity of WM microstructure. In our study, we investigated normative data from a large number of pediatric and adolescent participants to examine the developmental trends in DTI during this conspicuous WM maturation period.

MATERIALS AND METHODS

DTI data in 202 healthy pediatric and adolescent participants were analyzed retrospectively. Fractional anisotropy and mean diffusivity values in the corpus callosum and internal capsule were fitted to an exponential regression model to delineate age-dependent maturational changes across the WM structures.

RESULTS

The DTI metrics demonstrated characteristic exponential patterns of progression during development and conspicuous age-dependent changes in the first 36 months, with rostral WM tracts experiencing the highest slope of the exponential function. In contrast, the highest final FA and lowest MD values were detected in the splenium of the corpus callosum and the posterior limb of the internal capsule.

CONCLUSIONS

Our analysis shows that the more caudal portions of the corpus callosum and internal capsule begin the maturation process earlier than the rostral regions, but the rostral regions develop at a more accelerated pace, which may suggest that rostral regions rely on development of more caudal brain regions to instigate their development. Our normative DTI can be used as a reference to study normal spatiotemporal developmental profiles in the WM and help identify abnormal WM structures in patient populations.

Trainee misinterpretations on pediatric neuroimaging studies: classification, imaging analysis, and outcome assessment

BACKGROUND AND PURPOSE

The scope of trainee misinterpretations on pediatric neuroimaging studies has been incompletely assessed. Our aim was to evaluate the frequency of trainee misinterpretations on neuroimaging exams in children, describe a useful classification system, and assess related patient management or outcome changes.

MATERIALS AND METHODS

Pediatric neuroimaging examinations with trainee-dictated reports performed without initial attending radiologist assessment were evaluated for discrepant trainee interpretations by using a search of the RIS. The frequency of discrepant trainee interpretations was calculated and classified on the basis of the type of examination on which the error occurred, the specific type and severity of the discrepancy, and the effect on patient management and outcome. Differences relating to examination type and level of training were also assessed.

RESULTS

There were 143 discrepancies on 3496 trainee-read examinations for a discrepancy rate of 4.1%. Most occurred on CT examinations (131; 92%). Most discrepancies (75) were minor but were related to the clinical presentation. Six were major and potentially life-threatening. Thirty-seven were overcalls. Most had no effect on clinical management (97, 68%) or resulted simply in clinical reassessment or imaging follow-up (43, 30%). There was no permanent morbidity or mortality related to the misinterpretations. The most common misinterpretations were related to fractures (28) and ICH (23). CT examinations of the face, orbits, and neck had the highest discrepancy rate (9.4%). Third- and fourth-year residents had a larger discrepancy rate than fellows.

CONCLUSIONS

Trainee misinterpretations occur in 4.1% of pediatric neuroimaging examinations with only a small number being life-threatening (0.17%). Detailed analysis of the types of misinterpretations can be used to inform proactive trainee education.

Anisotropic diffusion properties in infants with hydrocephalus: a diffusion tensor imaging study

BACKGROUND AND PURPOSE

Diffusion tensor imaging (DTI) can noninvasively detect in vivo white matter (WM) abnormalities on the basis of anisotropic diffusion properties. We analyzed DTI data retrospectively to quantify the abnormalities in different WM regions in children with hydrocephalus during early infancy.

MATERIALS AND METHODS

Seventeen infants diagnosed with hydrocephalus (age range, 0.13-16.14 months) were evaluated with DTI and compared with 17 closely age-matched healthy children (age range, 0.20-16.11 months). Fractional anisotropy (FA), mean diffusivity (MD), axial diffusivity, and radial diffusivity values in 5 regions of interest (ROIs) in the corpus callosum and internal capsule were measured and compared. The correlation between FA and age was also studied and compared by ROI between the 2 study groups.

RESULTS

Infants with hydrocephalus had significantly lower FA, higher MD, and higher radial diffusivity values for all 3 ROIs in the corpus callosum, but not for the 2 ROIs in the internal capsule. In infants with hydrocephalus, the increase of FA with age during normal development was absent in the corpus callosum but was still preserved in the internal capsule. There was also a significant difference in the frequency of occurrence of abnormal FA values in the corpus callosum and internal capsule.

CONCLUSIONS

This retrospective DTI study demonstrated significant WM abnormalities in infants with hydrocephalus in both the corpus callosum and internal capsule. The results also showed evidence that the impact of hydrocephalus on WM was different in the corpus callosum and internal capsule.

De novo cerebral arteriovenous malformation: case report and literature review

We describe a rare case of a de novo cerebral arteriovenous malformation (AVM) in a 9-year-old girl. MR imaging at 6 years of age demonstrated band heterotopia. Follow-up MR imaging 3 years later demonstrated a new 3.5-cm AVM in the left parietol-occipital region, confirmed by conventional angiography. This report, along with limited previous reports, suggests that AVMs can be acquired lesions and that AVM development is a dynamic process extending into the postnatal period.

Antigenic differentiation of strains of turkey rhinotracheitis virus using monoclonal antibodies

Monoclonal antibodies (mAbs) were prepared against one UK isolate of turkey rhinotracheitis virus (TRTV). Those which were virus-neutralizing were selected and used, together with polyclonal antisera raised to each isolate in turkeys, in cross-neutralization tests against TRTV strains isolated in the UK and elsewhere. Whilst the polyclonal antisera showed that there was some diversity between them, all strains examined belonged to one serotype. The TRTV strains isolated in the UK could clearly be differentiated from those isolated elsewhere by some of the mAbs. Isolates of TRTV made in South Africa in 1978 and UK in 1985 were more closely related than were isolates made in UK and France within a few months. TRTV strains isolated from turkeys and chickens could not be differentiated. Some mAbs were found to be group-specific in that they neutralized all TRTV strains examined. All mAbs were of either the IgGl or IgG2a isotype and recognized the surface G glycoprotein.

Large arachnoid granulations involving the dorsal superior sagittal sinus: findings on MR imaging and MR venography

BACKGROUND AND PURPOSE

Large arachnoid granulations (AG) within the dorsal superior sagittal sinus (SSS) have been incompletely characterized and can be confused with pathology. This report reviews the characteristics of these anatomic structures to establish common imaging features that allow differentiation from pathology.

MATERIALS AND METHODS

Twelve cases of large AG in the dorsal SSS are presented, identified by MR imaging. Signal intensity characteristics, size, location, venographic appearance, and association with adjacent venous and osseous structures were documented.

RESULTS

A defect in the dura of the SSS was seen in all of the cases communicating with the subjacent subarachnoid space. The average size of the AG was 8.1 x 9.4 x 10.0 mm (range, 4-19 mm). Ten produced calvarial remodeling, and 11 were in the direct vicinity of the lambda. On T2-weighted images, all were hyperintense to the brain. On T1-weighted images, 8 were hypointense and 4 were hypointense with mixed areas of isointense signal intensity. All of the AGs were associated with cortical venous structures entering the sinus. On MR venography, AGs appeared as focal protrusions into the sinus, displacing, distorting, and narrowing the sinus lumen. Seven patients had headache without other visible cause on MR imaging, and 4 were initially interpreted as thrombosis or tumor.

CONCLUSION

Large AGs can occur in the dorsal SSS. They are well-defined projections of the subarachnoid space into the sinus, can cause luminal narrowing and calvarial remodeling, and have typical signal intensity characteristics, position, and morphology differentiating them from other pathology. Association with patient symptoms is uncertain.

Using skimmed milk agar to functionally screen a gut metagenomic library for proteases may lead to false positives

AIMS

Functional screens using skimmed-milk agar to obtain protease activity is a common approach. The aim of this study was to determine the efficacy of this screen to obtain protease activity from a metagenomic library.

METHODS AND RESULTS

A distal gut metagenomic library was functionally screened using a skimmed-milk agar. The functional screen provided 231 clones generating the characteristic clear halo indicative of protease production. Clone analysis revealed that they were not protease-positive, but expressed glycosidic hydrolases and produced acid, which was responsible for the clear halos.

CONCLUSIONS

The current skimmed-milk agar method to obtain proteases is not sufficiently robust to provide a definitive screen. Other- non-protease activities will also give the same clear halo and these would be interpreted as protease positive clones without further analysis. Hence a more robust buffered medium or a specific protein should be used.

SIGNIFICANCE AND IMPACT OF THE STUDY

Functional screens are a powerful approach to obtaining enzymes from large metagenomic libraries and proteases are a particularly interesting target. The skimmed-milk agar is not sufficiently robust to ensure that only proteases are isolated and in order to save time and money this study has shown that better designed media can aid in the process.

Diffusion tensor MR imaging reveals persistent white matter alteration after traumatic brain injury experienced during early childhood

BACKGROUND AND PURPOSE

Diffusion tensor imaging (DTI) can noninvasively quantify white matter (WM) integrity. Although its application in adult traumatic brain injury (TBI) is common, few studies in children have been reported. The purposes of this study were to examine the alteration of fractional anisotropy (FA) in children with TBI experienced during early childhood and to quantify the association between FA and injury severity.

MATERIALS AND METHODS

FA was assessed in 9 children with TBI (age = 7.89 +/- 1.00 years; Glasgow Coma Scale [GCS] = 10.11 +/- 4.68) and a control group of 12 children with orthopedic injuries without central nervous system involvement (age = 7.51 +/- 0.95 years). All of the subjects were at minimum 12 months after injury. We examined group differences in a series of predetermined WM regions of interest with t test analysis. We subsequently conducted a voxel-wise comparison with Spearman partial correlation analysis. Correlations between FA and injury severity were also calculated on a voxel-wise basis.

RESULTS

FA values were significantly reduced in the TBI group in genu of corpus callosum (CC), posterior limb of internal capsule (PLIC), superior longitudinal fasciculus (SLF), superior fronto-occipital fasciculus (SFO), and centrum semiovale (CS). GCS scores were positively correlated with FA in several WM areas including CC, PLIC, SLF, CS, SFO, and inferior fronto-occipital fasciculus (IFO).

CONCLUSION

This DTI study provides evidence that WM integrity remains abnormal in children with moderate-to-severe TBI experienced during early childhood and that injury severity correlated strongly with FA.

Magnetic resonance spectroscopy of the pediatric brain

Proton magnetic resonance (MR) spectroscopy is a complementary method to MR imaging for understanding disease processes in the pediatric brain. By demonstrating the presence of various metabolites in the sampled tissue, MR spectroscopy helps in the understanding of abnormalities detected by MR imaging or clinical examination. This capability is especially pertinent in the pediatric brain, where the manifestation of pathology is superimposed upon a background of normal or abnormal brain development. In this article, we review the major metabolites demonstrated by MR spectroscopy and present examples of MR spectra obtained in various pathological processes encountered in children.

Identification of an arteriovenous fistula in a child. Case report and review of the literature

BACKGROUND

A 6-year-old girl sustained a subarachnoid hemorrhage after a mild head injury and was discovered to have an arteriovenous fistula (AVF).

INVESTIGATIONS AND TREATMENT

The etiology of subarachnoid hemorrhage was not evident on the initial brain CT. Brain CT with CT angiography identified the lesion. The AVF was further imaged with brain MRI followed by cerebral angiography and successfully embolized.

OUTCOME

The child did not suffer any neurological sequelae.

CT, MRI and MRS of Epstein-Barr virus infection: case report

We report MRI and proton MR spectroscopy (MRS) findings in a 12-month-old girl with Epstein-Barr virus encephalitis. CT and MRI showed focal lesions in the basal ganglia. MRS of the lesions showed decreased N-acetyl aspartate and elevation of some amino acids, indicating an infectious rather than ischemic etiology. This case illustrates the use of MRS to narrow differential diagnosis.

Magnetic resonance imaging of the pediatric head and neck

Although the bulk of pediatric head and neck lesions are adequately evaluated by computed tomography (CT) alone, magnetic resonance imaging (MRI) provides valuable additional information in those lesions that are difficult to resolve on CT, and it is almost essential for assessment of possible intracranial extension of disease. The ability of MRI to show intrinsic characteristics of mass lesions can help direct therapeutic decisions. It should be utilized early in the imaging evaluation of most vascular lesions, including juvenile nasal angiofibroma and vascular malformations, in suspected neurogenic tumors, and as an adjunct in those cases where CT does not adequately demonstrate the extent or true nature of a lesion.

Basilar artery dissection in a young woman: a case report

The case of a young woman with basilar artery dissection, possibly precipitated by trauma, is presented, and the literature is reviewed.

Optic nerve enlargement in Krabbe's disease

We report imaging and gross pathologic findings from two cases of Krabbe disease in which there was marked enlargement of the intracranial optic nerves. Numerous globoid cells were observed in the optic nerves at autopsy in one case. Krabbe disease should be included in the differential diagnosis of children with enlargement of the optic nerves.

Spinal dural arteriovenous fistulas: recognizing the spectrum of magnetic resonance imaging findings

Spinal dural arteriovenous fistulas are the most common type of vascular malformation to involve the spinal cord. In this report, we describe and analyze the various magnetic resonance imaging (MRI) findings of spinal dural arteriovenous fistulas in order to increase awareness and prompt timely diagnosis. We reviewed 14 patients evaluated and treated for spinal dural arteriovenous fistulas over a seven year period, with special attention to findings on MRI. All patients had regions of increased cord signal on T2-weighted MRI, with corresponding hypointense signal on T1-weighted images in 11 patients (79 percent). Thirteen (93 percent) of 14 patients had focal increased cord caliber and eight (57 percent) had prominent intradural vessels. Cord enhancement was observed in all seven patients who were administered contrast and two patients had enhancement of intradural vessels. These imaging findings are relatively nonspecific, but should lead to further investigation with myelography or arteriography in the appropriate clinical setting.

Hypertensive encephalopathy in children

We present five cases of hypertensive encephalopathy in children, three with MR imaging findings and two with CT findings alone. One of the five patients had MR perfusion imaging, which showed perfusion abnormalities that support the concept of vasodilation as the major contributor to the syndrome. Hypertensive encephalopathy is rarely reported in children, and its true prevalence may be underestimated. Characteristic lesions in the severely hypertensive child should be recognized as manifestations of hypertensive encephalopathy, and subsequent clinical management should focus on treatment of the hypertension and/or its underlying causes.

Normal appearance of arachnoid granulations on contrast-enhanced CT and MR of the brain: differentiation from dural sinus disease

PURPOSE

To determine the imaging appearance and frequency with which arachnoid granulations are seen on contrast-enhanced CT and MR studies of the brain.

METHODS

We retrospectively reviewed 573 contrast-enhanced CT scans and 100 contrast-enhanced MR studies of the brain for the presence of discrete filling defects within the venous sinuses. An anatomic study of the dural sinuses of 29 cadavers was performed, and the location, appearance, and histologic findings of focal protrusions into the dural sinus lumen (arachnoid granulations) were assessed and compared with the imaging findings.

RESULTS

Discrete filling defects within the dural sinuses were found on 138 (24%) of the contrast-enhanced CT examinations. A total of 168 defects were found, the majority (92%) within the transverse sinuses. One third were isodense and two thirds were hypodense relative to brain parenchyma. Patients with filling defects were older than patients without filling defects (mean age, 46 years versus 40 years). Discrete intrasinus signal foci were noted on 13 (13%) of the contrast-enhanced MR studies. The foci followed the same distribution as the filling defects seen on CT scans and were isointense to hypointense on T1-weighted images, variable in signal on balanced images, and hyperintense on T2-weighted images. Transverse sinus arachnoid granulations were noted adjacent to venous entrance sites in 62% and 85% of the CT and MR examinations, respectively. Arachnoid granulations were found in 19 (66%) of the cadaveric specimens, in a similar distribution as that seen on the imaging studies.

CONCLUSION

Discrete filling defects, consistent with arachnoid granulations, may be seen in the dural sinuses on 24% of contrast-enhanced CT scans and on 13% of MR studies. They are focal, well-defined, and typically located within the lateral transverse sinuses adjacent to venous entrance sites. They should not be mistaken for sinus thrombosis or intrasinus tumor, but recognized as normal structures.

Identification of a molecule uniquely expressed on a gamma/delta TCR+ subset within bovine intestinal intraepithelial lymphocytes

An antigen has been identified, recognized by a novel monoclonal antibody CC45, which is expressed by a subpopulation of bovine gamma/delta T-cell receptor-positive (gamma/delta TCR+) T cells restricted in their distribution to the intestinal epithelium. This subset of intestinal intraepithelial lymphocytes (iIEL) which represented 8-29% of gamma/delta TCR+ T cells in the gut epithelium expressed CD45, CD3 and L-selectin; most of these cells were CD2- and CD8-. Electron microscopic studies of CC45+ cells revealed that they were large mononuclear leucocytes containing numerous mitochondria and smooth vesicles; a proportion of these contained membrane-bound dense granules. Immunoprecipitation of 125I-labelled iIEL analysed by sodium dodecyl sulphate-polyacrylamide gel electrophoresis under reducing and non-reducing conditions revealed polypeptides of 60,000 and 200,000 molecular weights, respectively indicating that the antigen, which appears distinct from molecules described in other species, is expressed on the cell surface as a complex.

Diagnosis of posttraumatic pericardial tamponade by plain film and computed tomography and control of bleeding by embolotherapy of the left inferior phrenic artery

A 21-year-old male developed pericardial tamponade in a delayed fashion after blunt chest trauma. Tamponade was not suspected clinically and was first seen on computed tomography of the abdomen. Plain films of the chest revealed distortion of the path of a Swan-Ganz catheter due to the ventricular compression. After drainage, left inferior phrenic artery embolization was performed to treat the persistent hemothorax.

Gastric syphilis: radiologic findings

Syphilis, a venereal infection caused by the spirochetal bacterium Treponema pallidum, has long been considered a primary public health concern in the United States. With the onset of the antibiotic era, the prevalence of the disease dramatically plummeted, as did interest in its radiologic manifestations. Rolfs and Nakashima [1] have shown that the prevalence of primary and secondary syphilis increased 34% from 1981 to 1989, to its highest level since 1949. Given this dramatic increase, classic manifestations of syphilis may warrant renewed attention. In its secondary and tertiary stages, syphilis can cause a wide range of gastric lesions that can mimic many other entities, from gastritis or benign ulcer disease to gastric carcinoma. Indeed, the acute gastritis of early secondary syphilis produces the earliest radiologically detectable signs of the disease. Cases of gastric syphilis submitted to the Armed Forces Institute of Pathology and cases drawn from the University of Cincinnati teaching file are used to illustrate the varied findings in this disease.

Distinction of naive and memory BoCD4 lymphocytes in calves with a monoclonal antibody, CC76, to a restricted determinant of the bovine leukocyte-common antigen, CD45

A murine IgG1 monoclonal antibody (mAb), CC76, has been produced that, based on findings of the relative molecular mass of polypeptides that it recognized, staining of leukocytes in blood and tissues, and the biological properties of the T lymphocyte subpopulations with which it reacts, is considered to identify an isoform of the leukocyte common antigen (LCA) family of molecules in cattle. The mAb is more similar to human CD45R which detect products requiring the presence of the B exon within the LCA gene and to the anti-rat mAb MRC-OX22, than to CD45RA or CD45R0. mAb CC76 reacts with an antigen expressed by subpopulations of cells in bovine blood that express BoCD2 and either the BoCD4 or BoCD8 antigens. T cells that express the gamma/delta T cell receptor identified with mAb to BoWC1 antigen did not react with CC76. The molecule detected is expressed on B cells but not on monocytes or granulocytes. Only 2% of cells in thymic suspensions stained with mAb CC76. Immature cortical thymocytes that were BoCD1+ did not react with CC76 and 90% of the cells in thymic suspensions that were CC76+ had the phenotype of mature thymocytes. These cells were primarily in the medulla. The LCA isoform detected thus appears to be acquired by mature cells shortly before emigration from the thymic medulla into the periphery. Expression of the molecule detected by mAb CC76 on cells from lymph nodes was similar to that in blood, but expression on cells from the gut mucosa was quite different. Almost all, 95% and 93% respectively, of the BoCD4+ cells in the gut mucosa or discrete Peyer's patches were CC76-. A greater proportion of BoCD8+ cells from these sites, 35% and 26%, expressed the antigen. Lymphocytes from animals that had been immunized with Trypanosoma brucei were sorted into BoCD4+, CC76+ and BoCD4+, CC76- populations and cultured in vitro with the variable surface glycoprotein antigen from the parasite. Lymphocyte transformation responses were entirely within the CC76- population indicating that the mAb distinguished naive from memory BoCD4+ T cells in cattle. Major histocompatibility complex (MHC) class I-restricted cytotoxic precursor cells that expressed the BoCD8 antigen sorted from cattle that were immune to Theileria parva were both CC76+ and CC76- indicating that different isoforms of the LCA may be expressed on MHC class I- and class II-restricted memory cells and that BoCD8 memory cells are heterogeneous with respect to the LCA isoform that they express.

Production of bovine immunoregulatory molecules by xenogeneic hybrids

The study of bovine cytokines and lymphocyte surface markers has been restricted by the lack of stable, long-lived, easily maintained cell lines. To address this problem, bovine mononuclear leucocytes were fused with the mouse thymoma cell line BW5147 to produce interspecies hybrid cell lines and clones. Hybridomas were produced which contained more than 40 chromosomes and expressed one or more bovine leucocyte surface markers, they grew well and were cloned without the use of exogenous factors. Fusion rates were improved when exogenous factors, including recombinant human interleukin-2 (rhIL-2), were added. Some hybrids secreted immunoregulatory factors able to maintain the growth of either an IL-2-dependent bovine T-cell line (C625) and/or preactivated normal bovine B cells. Anti-human IL-2 partially blocked the T-cell growth factor (TCGF) activity produced by these hybrids. The release of growth factors by the hybrid clones 5/AA6/16 and 5/AA6/19 was augmented by concanavalin A stimulation.

Investigation of bovine gut associated lymphoid tissue (GALT) using monoclonal antibodies against bovine lymphocytes

Gut associated lymphoid tissue of the small and large intestine of calves and cows has been compared morphologically and quantitatively using monoclonal antibodies to bovine lymphocytes. B cells were significantly decreased in the ileum of the cow compared to the calf. Significantly increased numbers of T cells were present in cell suspensions of all lymphoid areas of the cow compared to the calf. T lymphocyte subsets were quantified into cryostat sections of lymphoid tissues expressing BoT4, and BoT8 antigens demonstrated increased numbers in follicular and dome areas of the discrete Peyer's patches of the small and large intestine of the cow. BoT4+, BoT8+, and the non-BoT4/BoT8+ T cell subsets were increased in the mucosa of the cow as compared to the calf. Similarities in structure and lymphocyte composition of the discrete Peyer's patches of the small intestine, cecum and colon and isolated single follicles in the large intestine suggest similar functional properties.

Production and characterization of bovine monoclonal antibodies to respiratory syncytial virus

Six interspecific hybridomas (heterohybridomas) secreting bovine monoclonal antibodies (MAbs) against respiratory syncytial (RS) virus were produced. Four of the heterohybridomas were formed using the mouse myeloma cell line NS1 as the fusion partner, one using NS0, and the remaining heterohybridoma was formed using a bovine X murine hybridoma as the fusion partner. Five heterohybridomas secreted bovine IgG1 and one secreted IgG2. All six MAbs recognized human subtype A and B viruses as well as bovine RS virus. They were specific for the fusion glycoprotein and reacted with a 140K dimer and a 70K monomer in a Western blot of native antigen; three also bound to the 46K F1 component and its 22K cleavage product in a blot of reduced antigen. Two of these MAbs neutralized RS virus infectivity, inhibited virus-induced fusion, lysed RS virus-infected cells in the presence of complement and protected mice against RS virus challenge.

Two monoclonal antibodies (CC17, CC29) recognizing an antigen (Bo5) on bovine T lymphocytes, analogous to human CD5

Two new monoclonal antibodies (CC17 and CC29) raised against bovine thymocytes are described. The antibodies, both of which were IgG1, recognize a molecule of approximately 67,000 molecular weight on bovine T cells. They react T cells in peripheral blood, the lymph node paracortex and the periateriolar lymphoid sheath in the spleen. Both the cortex and medulla of the thymus are stained but the medulla reacts more intensely. They do not stain B cells in peripheral blood, the ileal Peyer's patch, the cortex or the primary follicles in lymph nodes. No activity was found on cells outside the lymphoid system, i.e. monocytes, alveolar macrophages or endothelial and epithelial tissue. The antigen recognized is considered to be the bovine homologue of CD5 (T1) in humans and Lyt1 in mice. The mAbs appear to be particularly useful for detecting cells in the peripheral blood of young calves which are of the T cell lineage but do not express BoT2 or the mature pan T cell antigen recognized by mAb IL-A27 and may thus allow identification of a population of bovine lymphocytes previously described as null cells.

Clinico-chemical changes in goats given carbon tetrachloride

Six healthy castrated male goats were each given 1.0, 1.25 or 1.5 ml of carbon tetrachloride per 10 kg BW by stomach tube (2 animals at each dose level). Definite signs of dose dependant liver damage were seen, starting about 4 hours after administration of the drug. The clinico-chemical changes included increased total and conjugated plasma bilirubin, decreased blood clotting activity, and increased activities of P-ASAT and P-GT. Further experiments are needed in animals afflicted with liverflukes to establish the lowest possible anthelmintic dose of carbon tetrachloride.

Myositis ossificans in the biceps femoris muscles causing sciatic nerve palsy. A case report

A case of bilateral myositis ossificans in the biceps femoris muscles causing a sciatic nerve palsy on the left side is described. Complete recovery of the sciatic nerve followed excision of the mass of ectopic bone. It is postulated that the patient's hobby of weight-lifting caused the ossification.

Pyocin inhibition of Neisseria gonorrhoeae: mechanism of action

Purified R-type pyocins (611 131) from Pseudomonas aeruginosa PA103 exhibited bactericidal activity against Neisseria gonorrhoeae. Killing of gonococci was a single-hit process requiring as few as 1 pyocin per colony-forming unit. Deoxyriboinucleic acid, ribonucleic acid, protein, and lipid syntheses were rapidly and completely inhibited. Oxygen uptake was also inhibited, but occurred after the inhibition of macromolecular synthesis. The cell lysis which occurred after pyocin inhibition of gonococcal growth was the result of endogenous gonococcal autolysin activity.

Infections in hospital

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