A novel characterized multi-drug-resistant Pseudocitrobacter sp. isolated from a patient colonized while admitted to a tertiary teaching hospital

BACKGROUND

Reports of nosocomial infections typically describe recognised microorganisms. Here, a novel bacterial species was isolated, based on rectal swab screening for carbapenemases post-admission, then phenotypically and genetically characterized.

METHODS

Sensititre, Vitek and API kits, MALDI and Illumina MiSeq were employed before profiles and phylogeny were compared with other related species.

FINDINGS

Determined to be a possible Enterobacterales, the isolate was found to have 99.7% 16s rRNA identity to Pseudocitrobacter corydidari; an Asian cockroach-associated species. Given the highly conserved/low variability of 16S rRNA genes in Enterobacterales, average nucleotide identity (ANI) analysis compared the new isolate's genome with those of 18 Enterobacteriaceae species, including confirmed species of Pseudocitrobacter and unnamed Pseudocitrobacter species in the SILVA database. Of these, Pseudocitrobactercorydidari had the highest ANI at 0.9562. The published genome of the only known isolate of P.corydidari does not include Antimicrobial Resistance Genes (ARGs), with exception of potential drug efflux transporters. In contrast, our clinical isolate bears recognised antimicrobial resistance genes, including Klebsiella pneumoniae carbapenemase. The associated genome suggests resistance to carbapenems, β-lactams, sulfonamides, fluoroquinolones, macrolides, aminoglycosides and cephalosporins. Phenotypic antimicrobial resistance was confirmed.

CONCLUSION

Evident variations in ARG profiles, human colonization and origin in a clinically relevant niche that is geographically, physically and chemically disparate lend credibility for divergent evolution or, less likely, parallel evolution with P. corydidari. Genome data for this new species have been submitted to GENBANK using the proposed nomenclature Pseudocitrobacter limerickensis. The patient was colonized, rather than infected, and did not require antimicrobial treatment.

Rosin as a Natural Alternative for the effective disinfection of ESKAPE Pathogens and Clostridioides difficile spores

AIM

Hospital-acquired infections (HAIs) caused by antimicrobial-resistant ESKAPE pathogens are a significant concern for the healthcare industry, with an estimated cost of up to ${\$}$45 billion per year in the US alone. Clostridioides difficile is an additional opportunistic pathogen that also poses a serious threat to immunocompromised patients in hospitals. Infections caused by these pathogens lead to increased hospital stays and repeated readmission, resulting in a significant economic burden. Disinfectants and sporicidals are essential to reduce the risk of these pathogens in hospitals, but commercially available products can have a number of disadvantages including inefficacy, long contact times, short shelf lives, and operator health hazards. In this study we evaluated the effectiveness of Rosin (a natural substance secreted by coniferous trees as a defence mechanism against wounds in tree bark) and its commercial derivative Rosetax-21 as disinfectants and sporicidal against the six ESKAPE pathogens (Enterococcus faecium, Staphylococcus aureus, Klebsiella pneumoniae, Acinetobacter baumannii, Pseudomonas aeruginosa, and Enterobacter species) and spore preparations from Clostridioides difficile.

METHODS AND RESULTS

Both Rosin and Rosetax-21 were tested under simulated clean and dirty conditions (with BSA) against the ESKAPE pathogens, and C. difficile spore preparations. In clean conditions, Rosin (5% weight/volume: w/v) demonstrated significant efficacy against five of the ESKAPE pathogens, with A. baumannii and E. faecium being the most susceptible, and K. pneumoniae the most resistant, showing only a one-log reduction after a 5 min treatment. However, in dirty conditions, all pathogens including K. pneumoniae exhibited at least a 3-log reduction to Rosin within 5 min. Rosetax-21 (5% w/v) was found to be less effective than Rosin in clean conditions, a trend that was exacerbated in the presence of BSA. Additionally, both Rosin and Rosetax-21 at 2.5% (w/v) achieved complete eradication of C. difficile spores when combined with 0.5% glutaraldehyde, though their standalone sporicidal activity was limited.

CONCLUSIONS

The findings from this study highlight the potential of Rosin and Rosetax-21 as both bactericidal and sporicidal disinfectants, with their efficacy varying based on the conditions and the pathogens tested. This presents an avenue for the development of novel healthcare disinfection strategies, especially against HAIs caused by antimicrobial-resistant ESKAPE pathogens and C. difficile.

Cold atmospheric pressure plasma-antibiotic synergy in Pseudomonas aeruginosa biofilms is mediated via oxidative stress response

Cold atmospheric-pressure plasma (CAP) has emerged as a potential alternative or adjuvant to conventional antibiotics for the treatment of bacterial infections, including those caused by antibiotic-resistant pathogens. The potential of sub-lethal CAP exposures to synergise conventional antimicrobials for the eradication of Pseudomonas aeruginosa biofilms is investigated in this study. The efficacy of antimicrobials following or in the absence of sub-lethal CAP pre-treatment in P. aeruginosa biofilms was assessed. CAP pre-treatment resulted in an increase in both planktonic and biofilm antimicrobial sensitivity for all three strains tested (PAO1, PA14, and PA10548), with both minimum inhibitory concentrations (MICs) and minimum biofilm eradication concentrations (MBECs) of individual antimicrobials, being significantly reduced following CAP pre-treatment of the biofilm (512-fold reduction with ciprofloxacin/gentamicin; and a 256-fold reduction with tobramycin). At all concentrations of antimicrobial used, the combination of sub-lethal CAP exposure and antimicrobials was effective at increasing time-to-peak metabolism, as measured by isothermal microcalorimetry, again indicating enhanced susceptibility. CAP is known to damage bacterial cell membranes and DNA by causing oxidative stress through the in situ generation of reactive oxygen and nitrogen species (RONS). While the exact mechanism is not clear, oxidative stress on outer membrane proteins is thought to damage/perturb cell membranes, confirmed by ATP and LDH leakage, allowing antimicrobials to penetrate the bacterial cell more effectively, thus increasing bacterial susceptibility. Transcriptomic analysis, reveals that cold-plasma mediated oxidative stress caused upregulation of P. aeruginosa superoxide dismutase, cbb3 oxidases, catalases, and peroxidases, and upregulation in denitrification genes, suggesting that P. aeruginosa uses these enzymes to degrade RONS and mitigate the effects of cold plasma mediated oxidative stress. CAP treatment also led to an increased production of the signalling molecule ppGpp in P. aeruginosa, indicative of a stringent response being established. Although we did not directly measure persister cell formation, this stringent response may potentially be associated with the formation of persister cells in biofilm cultures. The production of ppGpp and polyphosphate may be associated with protein synthesis inhibition and increase efflux pump activity, factors which can result in antimicrobial tolerance. The transcriptomic analysis also showed that by 6 h post-treatment, there was downregulation in ribosome modulation factor, which is involved in the formation of persister cells, suggesting that the cells had begun to resuscitate/recover. In addition, CAP treatment at 4 h post-exposure caused downregulation of the virulence factors pyoverdine and pyocyanin; by 6 h post-exposure, virulence factor production was increasing. Transcriptomic analysis provides valuable insights into the mechanisms by which P. aeruginosa biofilms exhibits enhanced susceptibility to antimicrobials. Overall, these findings suggest, for the first time, that short CAP sub-lethal pre-treatment can be an effective strategy for enhancing the susceptibility of P. aeruginosa biofilms to antimicrobials and provides important mechanistic insights into cold plasma-antimicrobial synergy. Transcriptomic analysis of the response to, and recovery from, sub-lethal cold plasma exposures in P. aeruginosa biofilms improves our current understanding of cold plasma biofilm interactions.

Large-scale characterization of hospital wastewater system microbiomes and clinical isolates from infected patients: profiling of multi-drug-resistant microbial species

BACKGROUND

Hospital-acquired infections (HAIs) and infectious agents exhibiting antimicrobial resistance (AMR) are challenges globally. Environmental patient-facing wastewater apparatus including handwashing sinks, showers and toilets are increasingly identified as sources of infectious agents and AMR genes.

AIM

To provide large-scale metagenomics analysis of wastewater systems in a large teaching hospital in the Republic of Ireland experiencing multi-drug-resistant HAI outbreaks.

METHODS

Wastewater pipe sections (N=20) were removed immediately prior to refurbishment of a medical ward where HAIs had been endemic. These comprised toilet U-bends, and sink and shower drains. Following DNA extraction, each pipe section underwent metagenomic analysis.

FINDINGS

Diverse taxonomic and resistome profiles were observed, with members of phyla Proteobacteria and Actinobacteria dominating (38.23 ± 5.68% and 15.78 ± 3.53%, respectively). Genomes of five clinical isolates were analysed. These AMR bacterial isolates were from patients >48 h post-admission to the ward. Genomic analysis determined that the isolates bore a high number of antimicrobial resistance genes (ARGs).

CONCLUSION

Comparison of resistome profiles of isolates and wastewater metagenomes revealed high degrees of similarity, with many identical ARGs shared, suggesting probable acquisition post-admission. The highest numbers of ARGs observed were those encoding resistance to clinically significant and commonly used antibiotic classes. Average nucleotide identity analysis confirmed the presence of highly similar or identical genomes in clinical isolates and wastewater pipes. These unique large-scale analyses reinforce the need for regular cleaning and decontamination of patient-facing hospital wastewater pipes and effective infection control policies to prevent transmission of nosocomial infection and emergence of AMR within potential wastewater reservoirs.

Assessment of Cold Atmospheric Pressure Plasma (CAPP) Treatment for Degradation of Antibiotic Residues in Water

The presence of antibiotic residues in water is linked to the emergence of antibiotic resistance globally and necessitates novel decontamination strategies to minimize antibiotic residue exposure in both the environment and food. A holistic assessment of cold atmospheric pressure plasma technology (CAPP) for β-lactam antibiotic residue removal is described in this study. CAPP operating parameters including plasma jet voltage, gas composition and treatment time were optimized, with highest β-lactam degradation efficiencies obtained for a helium jet operated at 6 kV. Main by-products detected indicate pH-driven peroxidation as a main mechanism of CAPP-induced decomposition of β-lactams. No in vitro hepatocytotoxicity was observed in HepG2 cells following exposure to treated samples, and E. coli exposed to CAPP-degraded β-lactams did not exhibit resistance development. In surface water, over 50% decrease in antibiotic levels was achieved after only 5 min of treatment. However, high dependence of treatment efficiency on residue concentration, pH and presence of polar macromolecules was observed.

Quorum Sensing in Halorubrum saccharovorum Facilitates Cross-Domain Signaling between Archaea and Bacteria

Quorum Sensing (QS) is a well-studied intercellular communication mechanism in bacteria, regulating collective behaviors such as biofilm formation, virulence, and antibiotic resistance. However, cell-cell signaling in haloarchaea remains largely unexplored. The coexistence of bacteria and archaea in various environments, coupled with the known cell-cell signaling mechanisms in both prokaryotic and eukaryotic microorganisms and the presence of cell-cell signaling mechanisms in both prokaryotic and eukaryotic microorganisms, suggests a possibility for haloarchaea to possess analogous cell-cell signaling or QS systems. Recently, N-acylhomoserine lactone (AHL)-like compounds were identified in haloarchaea; yet, their precise role-for example, persister cell formation-remains ambiguous. This study investigated the capacity of crude supernatant extract from the haloarchaeon Halorubrum saccharovorum CSM52 to stimulate bacterial AHL-dependent QS phenotypes using bioreporter strains. Our findings reveal that these crude extracts induced several AHL-dependent bioreporters and modulated pyocyanin and pyoverdine production in Pseudomonas aeruginosa. Importantly, our study suggests cross-domain communication between archaea and bacterial pathogens, providing evidence for archaea potentially influencing bacterial virulence. Using Thin Layer Chromatography overlay assays, lactonolysis, and colorimetric quantification, the bioactive compound was inferred to be a chemically modified AHL-like compound or a diketopiperazine-like molecule, potentially involved in biofilm formation in H. saccharovorum CSM52. This study offers new insights into putative QS mechanisms in haloarchaea and their potential role in interspecies communication and coordination, thereby enriching our understanding of microbial interactions in diverse environments.

Exploring halophilic environments as a source of new antibiotics

Microbial natural products from microbes in extreme environments, including haloarchaea, and halophilic bacteria, possess a huge capacity to produce novel antibiotics. Additionally, enhanced isolation techniques and improved tools for genomic mining have expanded the efficiencies in the antibiotic discovery process. This review article provides a detailed overview of known antimicrobial compounds produced by halophiles from all three domains of life. We summarize that while halophilic bacteria, in particular actinomycetes, contribute the vast majority of these compounds the importance of understudied halophiles from other domains of life requires additional consideration. Finally, we conclude by discussing upcoming technologies- enhanced isolation and metagenomic screening, as tools that will be required to overcome the barriers to antimicrobial drug discovery. This review highlights the potential of these microbes from extreme environments, and their importance to the wider scientific community, with the hope of provoking discussion and collaborations within halophile biodiscovery. Importantly, we emphasize the importance of bioprospecting from communities of lesser-studied halophilic and halotolerant microorganisms as sources of novel therapeutically relevant chemical diversity to combat the high rediscovery rates. The complexity of halophiles will necessitate a multitude of scientific disciplines to unravel their potential and therefore this review reflects these research communities.

Microbial communities of halite deposits and other hypersaline environments

Large regions of Earth's surface are underlain by salt deposits that evaporated from ancient oceans and are populated by extreme halophilic microbes. While the microbiology of ancient evaporites has been well studied, the ecology of halite deposits and more recently formed NaCl "salticle" stalactite structures (speleothems) in a Triassic halite mine are less well characterized. The microbiome of Kilroot Salt Mine was profiled using conventional and enhanced culturing techniques. From this, 89 halophilic archaeal isolates from six known genera, and 55 halophilic or halotolerant bacterial isolates from 18 genera were obtained. Culture-independent metagenomic approaches also revealed that culturing techniques were inadvertently biased toward specific taxa, and the need for optimized isolation procedures are required to enhance cultivation diversity. Speleothems formed from saturated brines are unique structures that have the potential to entomb haloarchaea cells for thousands of years within fluid inclusions. The presence of such fluid inclusions, alongside the high abundance of genes related to glycerol metabolism, biofilm formation, and persister cell formation is highly suggestive of an environmental niche that could promote longevity and survivability. Finally, previous studies reporting the discovery of novel biocatalysts from the Kilroot mine microbiome, suggests that this environment may be an untapped source of chemical diversity with high biodiscovery potential.

Physical activity and the prevention, reduction, and treatment of alcohol and other drug use across the lifespan (The PHASE review): A systematic review

The aim of this review is to systematically describe and quantify the effects of PA interventions on alcohol and other drug use outcomes, and to identify any apparent effect of PA dose and type, possible mechanisms of effect, and any other aspect of intervention delivery (e.g. key behaviour change processes), within a framework to inform the design and evaluation of future interventions. Systematic searches were designed to identify published and grey literature on the role of PA for reducing the risk of progression to alcohol and other drug use (PREVENTION), supporting individuals to reduce alcohol and other drug use for harm reduction (REDUCTION), and promote abstinence and relapse prevention during and after treatment of alcohol and other drug use (TREATMENT). Searches identified 49,518 records, with 49,342 excluded on title and abstract. We screened 176 full text articles from which we included 32 studies in 32 papers with quantitative results of relevance to this review. Meta-analysis of two studies showed a significant effect of PA on prevention of alcohol initiation (risk ratio [RR]: 0.72, 95%CI: 0.61 to 0.85). Meta-analysis of four studies showed no clear evidence for an effect of PA on alcohol consumption (Standardised Mean Difference [SMD]: 0.19, 95%, Confidence Interval -0.57 to 0.18). We were unable to quantitatively examine the effects of PA interventions on other drug use alone, or in combination with alcohol use, for prevention, reduction or treatment. Among the 19 treatment studies with an alcohol and other drug use outcome, there was a trend for promising short-term effect but with limited information about intervention fidelity and exercise dose, there was a moderate to high risk of bias. We identified no studies reporting the cost-effectiveness of interventions. More rigorous and well-designed research is needed. Our novel approach to the review provides a clearer guide to achieve this in future research questions addressed to inform policy and practice for different populations and settings.

Profiling the microbial community of a Triassic halite deposit in Northern Ireland: an environment with significant potential for biodiscovery

Kilroot salt mine, a Triassic halite deposit located in County Antrim, Northern Ireland, is the only permanent hypersaline environment on the island of Ireland. In this study, the microbiome of this unstudied environment was profiled for the first time using conventional and enhanced culturing techniques, and culture independent metagenomic approaches. Using both conventional isolation plates and iChip devices, 89 halophilic archaeal isolates from six known genera, and 55 halophilic or halotolerant bacterial isolates from 18 genera were obtained, based on 16S rRNA gene sequencing. The archaeal isolates were similar to those previously isolated from other ancient halite deposits, and as expected, numerous genera were identified in the metagenome which were not represented among the culturable isolates. Preliminary screening of a selection of isolates from this environment identified antimicrobial activities against a panel of clinically important bacterial pathogens from 15 of the bacterial isolates and one of the archaea. This, alongside previous studies reporting the discovery of novel biocatalysts from the Kilroot mine microbiome, suggests that this environment may be a new, untapped source of of chemical diversity with high biodiscovery potential.

Factors associated with study attrition in a pilot randomised controlled trial to explore the role of exercise-assisted reduction to stop (EARS) smoking in disadvantaged groups

Background

Study attrition has the potential to compromise a trial’s internal and external validity. The aim of the present study was to identify factors associated with participant attrition in a pilot trial of the effectiveness of a novel behavioural support intervention focused on increasing physical activity to reduce smoking, to inform the methods to reduce attrition in a definitive trial.

Methods

Disadvantaged smokers who wanted to reduce but not quit were randomised (N = 99), of whom 61 (62 %) completed follow-up assessments at 16 weeks. Univariable logistic regression was conducted to determine the effects of intervention arm, method of recruitment, and participant characteristics (sociodemographic factors, and lifestyle, behavioural and attitudinal characteristics) on attrition, followed by multivariable logistic regression on those factors found to be related to attrition.

Results

Participants with low confidence to quit, and who were undertaking less than 150 mins of moderate and vigorous physical activity per week at baseline were less likely to complete the 16-week follow-up assessment. Exploratory analysis revealed that those who were lost to follow-up early in the trial (i.e., by 4 weeks), compared with those completing the study, were younger, had smoked for fewer years and had lower confidence to quit in the next 6 months. Participants who recorded a higher expired air carbon monoxide reading at baseline were more likely to drop out late in the study, as were those recruited via follow-up telephone calls. Multivariable analyses showed that only completing less than 150 mins of physical activity retained any confidence in predicting attrition in the presence of other variables.

Conclusions

The findings indicate that those who take more effort to be recruited, are younger, are heavier smokers, have less confidence to quit, and are less physically active are more likely to withdraw or be lost to follow-up.

Galleria mellonella as a novel in vivo model for assessment of the toxicity of 1-alkyl-3-methylimidazolium chloride ionic liquids

The larval form of the Greater Wax Moth (Galleria mellonella) was evaluated as a model system for the study of the acute in vivo toxicity of 1-alkyl-3-methylimidazolium chloride ionic liquids. 24-h median lethal dose (LD50) values for nine of these ionic liquids bearing alkyl chain substituents ranging from 2 to 18 carbon atoms were determined. The in vivo toxicity of the ionic liquids was found to correlate directly with the length of the alkyl chain substituent, and the pattern of toxicity observed was in accordance with previous studies of ionic liquid toxicity in other living systems, including a characteristic toxicity 'cut-off' effect. However, G. mellonella appeared to be more susceptible to the toxic effects of the ionic liquids tested, possibly as a result of their high body fat content. The results obtained in this study indicate that G. mellonella represents a sensitive, reliable and robust in vivo model organism for the evaluation of ionic liquid toxicity.

Antibiofilm Activity of the Brown Alga Halidrys siliquosa against Clinically Relevant Human Pathogens

The marine brown alga Halidrys siliquosa is known to produce compounds with antifouling activity against several marine bacteria. The aim of this study was to evaluate the antimicrobial and antibiofilm activity of organic extracts obtained from the marine brown alga H. siliquosa against a focused panel of clinically relevant human pathogens commonly associated with biofilm-related infections. The partially fractionated methanolic extract obtained from H. siliquosa collected along the shores of Co. Donegal; Ireland; displayed antimicrobial activity against bacteria of the genus Staphylococcus; Streptococcus; Enterococcus; Pseudomonas; Stenotrophomonas; and Chromobacterium with MIC and MBC values ranging from 0.0391 to 5 mg/mL. Biofilms of S. aureus MRSA were found to be susceptible to the algal methanolic extract with MBEC values ranging from 1.25 mg/mL to 5 mg/mL respectively. Confocal laser scanning microscopy using LIVE/DEAD staining confirmed the antimicrobial nature of the antibiofilm activity observed using the MBEC assay. A bioassay-guided fractionation method was developed yielding 10 active fractions from which to perform purification and structural elucidation of clinically-relevant antibiofilm compounds.

Primum non nocere: Multimodality management strategies when multiple mass lesions strike a single patient

BACKGROUND

The management of multiple symptomatic intracranial pathological processes in a single patient presents a rare and challenging problem for the neurosurgeon and the patient. Neurosurgeons must utilize a full spectrum of neurosurgical options to achieve the best patient outcome.

CASE DESCRIPTION

We present a unique case of a 63-year-old woman who presented with a large convexity meningioma causing headaches, an acoustic neuroma causing deafness and imbalance and a suprasellar arachnoid cyst compromising the visual fields. Therapeutic intervention was staged based on the primum non nocere concept. First, the patient underwent stereotactic intracavitary cyst irradiation using colloidal 32P. Secondly, microsurgical resection of the convexity meningioma was performed. Finally, Gamma Knife radiosurgery of the acoustic neuroma was performed. One year after multimodality management, the patient was neurologically improved. There was no evidence of meningioma or cyst recurrence and the growth of the acoustic neuroma was arrested.

CONCLUSION

This case demonstrates the value of multi-modality treatment of neurosurgical pathology, utilizing minimally invasive techniques when possible.

Radiosurgery for childhood intracranial arteriovenous malformations

OBJECTIVE

The optimal management of intracranial arteriovenous malformations (AVMs) in children remains controversial. Children with intracranial AVMs present a special challenge in therapeutic decision-making because of the early recognition of their future life-long risks of hemorrhage if they are treated conservatively. The goals of radiosurgery are to achieve complete AVM obliteration and to preserve neurological function. We present long-term outcomes for a series of children treated using radiosurgery.

METHODS

The findings for 53 consecutive children who underwent at least 36 months of imaging follow-up monitoring after radiosurgery were reviewed. The median age at the time of treatment was 12 years (range, 2-17 yr). Thirty-one children (58%) presented after their first intracranial hemorrhaging episodes, two (4%) after their second hemorrhaging episodes, and one (2%) after five hemorrhaging episodes. Nineteen children (36%) presented with unruptured AVMs, and a total of 25 children (47%) exhibited neurological deficits. AVMs were graded as Spetzler-Martin Grade I (2%), Grade II (23%), Grade III (36%), Grade IV (9%), or Grade VI (30%). The median AVM volume was 1.7 ml (range, 0.11-10.2 ml). The median marginal dose was 20 Gy (range, 15-25 Gy).

RESULTS

Results were stratified according to AVM volumes (Group 1, < or =3 ml; Group 2, >3 ml to < or =10 ml; Group 3, >10 ml). Twenty-eight patients (80%) in Group 1 and 11 (64.7%) in Group 2 achieved complete obliteration. The only patient in Group 3 did not achieve obliteration. Complications included brainstem edema (n = 1) and transient pulmonary edema (n = 1). Four patients experienced hemorrhaging episodes, 30, 40, 84, and 96 months after radiosurgery. Multivariate logistic regression analysis demonstrated that only volume was significantly correlated with obliteration rates (P = 0.0109).

CONCLUSION

Radiosurgery is safe and efficacious for selected children with AVMs. The obliteration rates and the attendant low morbidity rates suggest a primary role for stereotactic radiosurgery for pediatric AVMs.

Distinguishing recurrent tumor and radiation necrosis with positron emission tomography versus stereotactic biopsy

With the recent approval of reimbursement for positron emission tomography (PET), it has become important to clarify the utility of this diagnostic study. We evaluated the utility of PET to distinguish radiation necrosis from recurrent tumor in a retrospective review of patients with primary glial neoplasms. Fifteen patients had preoperative contrast-enhanced MRI and PET images followed by stereotactic biopsy or craniotomy and histological confirmation. The sensitivity of PET was 43% (6/14) and the specificity was 100% (1/1). We examined the sensitivity of PET as a function of volumetric contrast enhancement on MRI. Eighty percent of true-positive PET studies occurred with volume enhancement greater than 10 cm(3). Seventy-five percent of false negatives occurred with volume enhancement less than 6 cm(3). Given the clinical significance of distinguishing tumor progression from radiation necrosis, we believe that PET is insufficient to resolve radiation necrosis versus tumor progression.

Brain metastases in patients with no known primary tumor

BACKGROUND

The care of patients with a brain metastasis from unknown primary site is controversial. The authors reviewed the results of stereotactic radiosurgery in this group of patients to better define clinical expectations.

METHODS

During an 11-year interval, radiosurgery was performed in 421 patients with brain metastases at the University of Pittsburgh. Fifteen patients had solitary or multiple (< or = 5) brain metastases without a detectable primary site at the time of initial presentation. In five patients, a histologic diagnosis of cancer was obtained from extracranial metastatic sites. In 10 patients, a diagnosis was obtained from the brain. A total of 31 tumors with a mean volume of 4.3 mL (range, 0. 05-18.6 mL) underwent radiosurgery with a mean marginal dose of 16.2 Gray (Gy) (range, 12-20 Gy). Fourteen patients (93.3%) also received whole brain fractionated radiation therapy.

RESULTS

The median survival was 15 months after radiosurgery (range, 1-48 months) and 27 months after their initial diagnosis of cancer. In 4 patients (26. 7%), the primary tumor was discovered later (lung in 3 patients and liver in 1). Three of these four patients died due to progression of their primary tumor. Of the remaining 11 patients, 4 died of progression of extracranial metastases, 2 died of other systemic diseases, and 3 patients died because of progression of brain metastasis. Three patients (20%) were still living between 21-48 months after radiosurgery. The presence of active systemic disease and brain stem location both were associated with a poor outcome (P = 0.004 and 0.04). The actuarial imaging-defined local tumor control rate was 91.3 +/- 5.9% at 4 years.

CONCLUSIONS

Radiosurgery was an effective strategy for patients with brain metastases from an unknown primary site. Disease progression outside of the brain was the usual cause for patient death.

Radiosurgery for hemangiomas of the cavernous sinus and orbit: technical case report

OBJECTIVE AND IMPORTANCE

Hemangiomas of neurosurgical interest are histologically benign vascular tumors that most often occur in the orbit or cavernous sinus. Hemangiomas can be diagnosed by their characteristic radiographic and angiographic appearance and their tendency to bleed excessively during attempted removal. Intracranial or intraorbital hemangiomas require treatment when they become symptomatic.

CLINICAL PRESENTATION

We report four hemangioma patients who presented with ocular symptoms or signs, such as orbital pain, ophthalmoplegia, proptosis, or impaired visual acuity. Before our evaluation, two patients had each had incomplete resections aborted because of excessive blood loss, one patient had undergone a nondiagnostic transsphenoidal biopsy, and one patient had had an unsuccessful embolization.

INTERVENTION

All four patients were treated with gamma knife radiosurgery. Tumors received a minimal tumor dose that ranged from 14 to 19 Gy. Follow-up evaluations were performed 6 to 24 months after radiosurgery and revealed a reduction in tumor volume in three patients and no tumor progression in the fourth. All patients had symptomatic improvement, but one had persistent diplopia.

CONCLUSION

In this early experience, stereotactic radiosurgery proved to be an effective management strategy that avoided the potentially serious complications associated with surgery or embolization of cavernous sinus hemangiomas.

Successful management of sellar and suprasellar arachnoid cysts with stereotactic intracavitary irradiation: an expanded report of four cases

OBJECTIVE

Sellar and suprasellar arachnoid cysts may be asymptomatic or may cause headache, optic nerve compression, endocrine dysfunction, or hydrocephalus. We propose a minimally invasive treatment strategy when intervention is indicated.

METHODS

Four patients with sellar and suprasellar arachnoid cysts presented with headache, visual compromise, and endocrine dysfunction. Two of the four patients previously had undergone unsuccessful surgical intervention. The imaging studies of two patients were diagnostic of an arachnoid cyst.

RESULTS

All four patients underwent stereotactic intracavitary radiation with cyst regression and symptomatic improvement. In each patient, the optic chiasm was decompressed successfully. There were no complications from the procedure.

CONCLUSION

Stereotactic intracavitary irradiation of arachnoid cysts proved to be safe and effective. The procedure obviated the need for open cyst fenestration or shunting.

Thalamic stimulation for choreiform movement disorders in children. Report of two cases

Surgery for movement disorders is most commonly performed in patients with dyskinesia and tremor associated with Parkinson's disease or in those with essential tremor. The role of ablative surgery or deep brain stimulation in patients with choreiform movements is poorly defined. The authors placed thalamic stimulation systems in two children with disabling choreiform disorders due to intracerebral hemorrhage or cerebral palsy. Each patient displayed choreiform movements in the upper extremities both at rest and with intention, which interfered with daily activities and socialization. Both children obtained significant improvement in their choreiform movements, and their upper extremity function improved with no incidence of morbidity. Thalamic stimulation appears to be a promising and nonablative approach for children with choreiform movement disorders.

Iatrogenic pneumocephalus secondary to intravenous catheterization. Case report

The presence of pneumocephalus in a patient without a history of undergoing intracranial or intrathecal procedures is a significant radiographic finding that portends a violation of the dural barrier or the presence of infection. The authors report a case of iatrogenic pneumocephalus that confounded the evaluation of a patient with unrelated neurological disorders, resulting in unnecessary transfer of the patient and utilization of medical resources. A review of 100 sequential computerized tomography scans obtained in patients for any indication in the emergency department revealed a 6% incidence of iatrogenic intravenous pneumocephalus. Computerized tomography scans revealing pneumocephalus had been obtained for altered mental status, focal motor deficit, seizure, and trauma. More careful intravenous catheterization and recognition of the condition on imaging may avoid similar problems.

Restorative neurosurgery: opportunities for restoration of function in acquired, degenerative, and idiopathic neurological diseases

Historically, neurosurgery has improved the environment of the nervous system to promote maximal spontaneous recovery of function. The population of patients whom we treat at present is a small portion of those who suffer from disabling neurological illnesses. Based on a combination of new technology, and advances in neuroscience, restorative neurosurgery is advancing the frontiers of our specialty, and providing the potential to restore lost function. Significant advancements in gene therapy, the discovery and delivery of neurotrophic factors, and cell transplantation now require neurosurgeons to broaden the scope of our practice so that it includes the restoration of function in an enormous number of patients with acquired, degenerative and idiopathic neurological diseases. In order to meet the present challenge, neurosurgeons must broaden our vision, our role, and our future educational goals. In this review, we summarize the landmark advances in the basic and clinical neurosciences and the results of clinical trials that are driving our evolution from passive reaction to disease to active attempts to restore lost central nervous system function.

Propionibacterium [correction of Proprionibacterium] acnes infections of cerebrospinal fluid shunts

Ventricular cerebrospinal fluid shunt infections with Propionibacterium acnes are generally low-grade, indolent infections. Typical presentations include gradual shunt malfunction, nausea, headache, malaise, and infrequently, fever. In all, 489 shunt procedures performed between January 1992 and December 1995, and in 15 of these cases P. acnes was subsequently cultured from reservoir taps or an intraoperative culture which was obtained when the existing shunt components were revised. Six of these, representing 14.6% of shunt infections, were considered to be true P. acnes shunt infections, as they were associated with either CSF leukocytosis or the identification of gram-positive rods by gram stain. The others were considered to be probable contaminants. Detailed analysis of all 15 of these cases revealed that no patient had positive CSF cultures after removal of the infected shunt and the initiation of antibiotics. Given the benign characteristics of P. acnes shunt infections, the broad sensitivity to antibiotics, and the rapid sterilization of the cerebrospinal fluid, it may be possible to treat such cases with short-term perioperative antibiotics and replacement of the shunt components, in place of prolonged external ventricular drainage and antibiotics. This would have eliminated 8 operative procedures and reduced the estimated length of stay by 77 patient-days in these 15 children.

Retinal pigment epithelium abnormalities in mice with adenomatous polyposis coli gene disruption

OBJECTIVE

To examine eyes from mice with targeted adenomatous polyposis coli (APC) gene disruption to determine if retinal pigment epithelium (RPE) abnormalities replicate the human counterpart.

METHODS

Thirty-two eyes from 16 mice heterozygous for APC gene disruption (chain-termination mutation in codon 1638 of exon 15) and 12 control eyes were examined by light microscopy.

RESULTS

Fifteen of 32 eyes from 12 of 16 APC-disrupted mice demonstrated abnormalities of the RPE and retina. The RPE abnormalities included RPE coloboma, unifocal and multifocal RPE hypertrophy, RPE hyperplasia, and RPE duplication with invasion in the areas of outer and inner segments. Retinal abnormalities included outer nuclear layer duplication and outer nuclear layer atrophy. There were no RPE and retinal abnormalities seen in the control eyes.

CONCLUSIONS

This study is consistent with the hypothesis that the APC gene is critical in the regulation of RPE proliferation and development. These findings also demonstrate that mutation of the APC gene in codon 1638, a location beyond the previously described critical region for human RPE abnormalities, leads to perturbation in the mouse RPE and retina. Further study of this murine model and the APC/RPE relationship may provide insight into regulatory mechanisms for RPE proliferation.

Atrophy and degeneration of ganglion cells in central retina following loss of postsynaptic target neurons in the dorsal lateral geniculate nucleus of the adult cat

Selective degeneration of neurons in the dorsal lateral geniculate nucleus (dLGN) of the adult cat was produced by in situ injection of kainic acid. This rapid degeneration mimics the loss of lateral geniculate neurons seen after neonatal visual cortex ablation. Following survivals of 2, 4, or 6 months, the geniculate was injected with horseradish peroxidase (HRP) and the retinas were examined for the presence of retrogradely labeled, as well as unlabeled, cells. Total ganglion cell density in central nasal retina was not different from that of controls at 2 or 4 months, but by 6 months had decreased to 68% of control values. The proportion of cells labeled with HRP did not change at 2 months, but decreased from 84% in controls to less than 1% by 4 months, and none were labeled at 6 months. Surviving ganglion cells in central retina showed atrophy of the cell body, a finding not apparent in data from the retinal periphery. Shrinkage occurred in the few cells labeled with HRP surviving at 4 months, as well as among the unlabeled cells surviving at 4 and 6 months. These results show that the survival of central retinal ganglion cells in the cat continues to depend on intact target neurons beyond the period of development. Mature ganglion cells in central retina respond to loss of appropriate targets first by axon terminal retraction and then by atrophy and cell death. However, when compared to the response of cells located in far peripheral retina following dLGN neuron loss, central ganglion cells take longer to undergo axonal retraction and a greater proportion of the central ganglion cells, although atrophied, survive after 6 months.