BiVO4 Photoanodes Enhanced with Metal Phosphide Co-Catalysts: Relevant Properties to Boost Photoanode Performance

Achieving highly performant photoanodes for oxygen evolution is key to developing photoelectrochemical devices for solar water splitting. In this work, BiVO4 photoanodes are enhanced with a series of core-shell structured bimetallic nickel-cobalt phosphides (MPs), and key insights into the role of co-catalysts are provided. The best BiVO4 /Ni1.5 Co0.5 P and BiVO4 /Ni0.5 Co1.5 P photoanodes achieve a 3.5-fold increase in photocurrent compared with bare BiVO4 . It is discovered that this enhanced performance arises from a synergy between work function, catalytic activity, and capacitive ability of the MPs. Distribution of relaxation times analysis reveals that the contact between the MPs, BiVO4 , and the electrolyte gives rise to three routes for hole injection into the electrolyte, all of which are significantly improved by the presence of a second metal cation in the co-catalyst. Kinetic studies demonstrate that the significantly improved interfacial charge injection is due to a lower charge-transfer resistance, enhanced oxygen-evolution reaction kinetics, and larger surface hole concentrations, providing deeper insights into the carrier dynamics in these photoanode/co-catalyst systems for their rational design.

Influence of Temperature and Precipitation Anomaly on the Seasonal Emergence of Invasive Bark Beetles in Subtropical South America

Several invasive bark beetle species have caused major economic and ecological losses in South America. Accurate predictions of beetle emergence times will make control efforts more efficient and effective. To determine whether bark beetle emergence can be predicted by season, temperature, or precipitation, we analyzed trapping records for three introduced pest species of bark beetles in Uruguay. We used trigonometric functions as seasonal predictors in generalized linear models to account for purely seasonal effects, while testing for effects of temperature and precipitation. Results show that all three beetle species had strong but unique seasonal emergence patterns and responded differently to temperature and precipitation. Cyrtogenius luteus (Blandford) emerged in summer and increased with precipitation but was not affected by temperature. Hylurgus ligniperda (Fabricius) emerged in winter and increased with temperature but was not affected by precipitation. Orthotomicus erosus (Wollaston) had a primary emergence in spring, and a smaller emergence in early summer, but showed no significant relationship with temperature or precipitation. This study shows that the emergence of these bark beetle species in Uruguay is influenced by seasonality more than by temperature and precipitation fluctuations. It also shows how seasonality can be easily incorporated into models to make more accurate predictions about pest population dynamics.

Dynamic disorder, phonon lifetimes, and the assignment of modes to the vibrational spectra of methylammonium lead halide perovskites

Raman and THz spectra of CH₃NH₃PbX₃ interpreted with a catalogue of computed vibrations and their influence on heat and electrical transport.

A chemometric study of ageing in lead-based paints

The development of non-invasive analytical methods is of widespread interest to the field of conservation science, providing chemical insight into the materials used to create painted works of art, which can, for example, inform decisions about their restoration and preservation, or help discern original works from forgeries. A key undertaking in this area is to develop practical methods for identifying and understanding the chemical processes that occur in paint films under ageing. Furthermore, whereas a number of scientific studies have focussed on model systems in which natural ageing processes are simulated in a short time by irradiation under ultraviolet (UV) light, it remains to be established to what extent natural and accelerated ageing induce similar chemical changes. In this work, we employ FT-Raman spectroscopy, together with a simple spectral-deconvolution algorithm, to study in detail the spectral changes accompanying the natural and UV-accelerated ageing of lead-based paint films. We find that the two processes differ significantly, and that spectroscopic signatures, principally in the fluorescence background, can thus be used to differentiate the two modes of ageing and hence possibly to identify attempted forgeries. Our studies also suggest that paints based on proteinaceous binders are more stable to ageing than lipid-bound ones. Finally, we investigate the possibility of using our chemometric deconvolution technique, in conjunction with multivariate analysis, for the semi-automated characterisation of the degree or extent of ageing in unknown samples.

The genome sequence of Schizosaccharomyces pombe

We have sequenced and annotated the genome of fission yeast (Schizosaccharomyces pombe), which contains the smallest number of protein-coding genes yet recorded for a eukaryote: 4,824. The centromeres are between 35 and 110 kilobases (kb) and contain related repeats including a highly conserved 1.8-kb element. Regions upstream of genes are longer than in budding yeast (Saccharomyces cerevisiae), possibly reflecting more-extended control regions. Some 43% of the genes contain introns, of which there are 4,730. Fifty genes have significant similarity with human disease genes; half of these are cancer related. We identify highly conserved genes important for eukaryotic cell organization including those required for the cytoskeleton, compartmentation, cell-cycle control, proteolysis, protein phosphorylation and RNA splicing. These genes may have originated with the appearance of eukaryotic life. Few similarly conserved genes that are important for multicellular organization were identified, suggesting that the transition from prokaryotes to eukaryotes required more new genes than did the transition from unicellular to multicellular organization.

University of Kentucky community-based field experience: program description

Community-based field experiences (CBFE) provide students with exemplary experiential learning opportunities. The purposes of this paper are to describe the University of Kentucky College of Dentistry (UKCD) CBFE and report the results of a two-year, self-report survey that assessed the primary course goal, students' perceptions of change in knowledge and skills related to nineteen areas of patient care (n = 90, 100% return rate), and their overall rating of the program. Knowledge and skill data were analyzed using the non-parametric binomial test for comparing proportions. A significant (.05 level) majority of students reported increases in knowledge in all areas to which they were exposed. Descriptive frequencies summarizing the results of the total CBFE experience indicate that the majority of students felt it was a positive experience. The CBFE continues to be a meaningful element in the UKCD curriculum as it provides students with a relevant, authentic educational experience.

Complete genome sequence of a multiple drug resistant Salmonella enterica serovar Typhi CT18

Salmonella enterica serovar Typhi (S. typhi) is the aetiological agent of typhoid fever, a serious invasive bacterial disease of humans with an annual global burden of approximately 16 million cases, leading to 600,000 fatalities. Many S. enterica serovars actively invade the mucosal surface of the intestine but are normally contained in healthy individuals by the local immune defence mechanisms. However, S. typhi has evolved the ability to spread to the deeper tissues of humans, including liver, spleen and bone marrow. Here we have sequenced the 4,809,037-base pair (bp) genome of a S. typhi (CT18) that is resistant to multiple drugs, revealing the presence of hundreds of insertions and deletions compared with the Escherichia coli genome, ranging in size from single genes to large islands. Notably, the genome sequence identifies over two hundred pseudogenes, several corresponding to genes that are known to contribute to virulence in Salmonella typhimurium. This genetic degradation may contribute to the human-restricted host range for S. typhi. CT18 harbours a 218,150-bp multiple-drug-resistance incH1 plasmid (pHCM1), and a 106,516-bp cryptic plasmid (pHCM2), which shows recent common ancestry with a virulence plasmid of Yersinia pestis.

Genome sequence of Yersinia pestis, the causative agent of plague

The Gram-negative bacterium Yersinia pestis is the causative agent of the systemic invasive infectious disease classically referred to as plague, and has been responsible for three human pandemics: the Justinian plague (sixth to eighth centuries), the Black Death (fourteenth to nineteenth centuries) and modern plague (nineteenth century to the present day). The recent identification of strains resistant to multiple drugs and the potential use of Y. pestis as an agent of biological warfare mean that plague still poses a threat to human health. Here we report the complete genome sequence of Y. pestis strain CO92, consisting of a 4.65-megabase (Mb) chromosome and three plasmids of 96.2 kilobases (kb), 70.3 kb and 9.6 kb. The genome is unusually rich in insertion sequences and displays anomalies in GC base-composition bias, indicating frequent intragenomic recombination. Many genes seem to have been acquired from other bacteria and viruses (including adhesins, secretion systems and insecticidal toxins). The genome contains around 150 pseudogenes, many of which are remnants of a redundant enteropathogenic lifestyle. The evidence of ongoing genome fluidity, expansion and decay suggests Y. pestis is a pathogen that has undergone large-scale genetic flux and provides a unique insight into the ways in which new and highly virulent pathogens evolve.

Community voices: views on the training of future doctors in Birmingham, UK

The United Kingdom (UK) population is diverse with nearly 6% minority ethnic communities. Both patients and doctors experience difficulties when dealing with someone from a different ethnic group. Medical education has failed to keep pace with the changing needs of the diverse population. We report a project in which 12 established (religious/cultural and specific interest) community groups expressed their views on what future doctors should learn about serving diverse populations. Data were obtained by group discussion and through the media using a structured format. Fifteen themes emerged which were grouped under three broad themes: firstly, the identification by group members of their perception of the 'differences' in social and cultural beliefs and behaviours of their individual community; secondly, the identification of characteristics of a culturally sensitive doctor; and lastly, recommendations for changes in medical training. New teaching has been introduced to the medical curriculum that incorporates the themes raised by the communities and which reflects consciousness raising and communication issues.

Analysis of 41 kb of the DNA sequence from the right arm of chromosome II of Schizosaccharomyces pombe

We report the complete sequence of cosmid c18A7 (41 046 bp insert), located on the right arm of chromosome II of the Schizosaccharomyces pombe genome. The sequence, which partially overlaps with cosmids SPBC4F6 and SPBC336, contains 16 open reading frames (ORFs) capable of coding for proteins of at least 100 amino acid residues in length (one partial) and one small nucleolar RNA (snoRNA). Four known genes were found: swi10 (encoding a mating-type switching protein also involved in nucleotide excision repair); dim1 (encoding a dimethyladenosine transferase); arf1 (encoding ADP-ribosylation factor 1); and pol3 (cdc6) the partial fragment, encoding the 125 kDa catalytic subunit of the DNA polymerase type B. Six ORFs similar to known proteins were found. They include a transporter of the major facilitator superfamily class, a vacuolar sorting protein, an asparagine synthase, a nuclear protein, a reticulum oxidoreductin and a heat shock protein. Each protein product of the other six ORFs has conserved domains and can be assigned a molecular, but not a biological, function. The sequence has been submitted to the EMBL database under Accession No. AL080287.

Massive gene decay in the leprosy bacillus

Leprosy, a chronic human neurological disease, results from infection with the obligate intracellular pathogen Mycobacterium leprae, a close relative of the tubercle bacillus. Mycobacterium leprae has the longest doubling time of all known bacteria and has thwarted every effort at culture in the laboratory. Comparing the 3.27-megabase (Mb) genome sequence of an armadillo-derived Indian isolate of the leprosy bacillus with that of Mycobacterium tuberculosis (4.41 Mb) provides clear explanations for these properties and reveals an extreme case of reductive evolution. Less than half of the genome contains functional genes but pseudogenes, with intact counterparts in M. tuberculosis, abound. Genome downsizing and the current mosaic arrangement appear to have resulted from extensive recombination events between dispersed repetitive sequences. Gene deletion and decay have eliminated many important metabolic activities including siderophore production, part of the oxidative and most of the microaerophilic and anaerobic respiratory chains, and numerous catabolic systems and their regulatory circuits.

Analysis of 114 kb of DNA sequence from fission yeast chromosome 2 immediately centromere-distal to his5

One hundred and fourteen kilobase pairs (kb) of contiguous genomic sequence have been determined immediately distal to the his5 genetic marker located about 0.9 Mb from the centromere on the long arm of Schizosaccharomyces pombe chromosome 2. The sequence is contained in overlapping cosmid clones c16H5, c12D12, c24C6 and c19G7, of which 20 kb are identical to previously reported sequence from clone c21H7. The remaining 93 781 bp of sequence contains 10 known genes (cdc14, cdm1, cps1, gpa1, msh2, pck2, rip1, rps30-2, sad1 and ubl1), 32 open reading frames (ORFs) capable of coding for proteins of at least 100 amino acid residues in length, one 5S rRNA gene, one tRNA(Pro) gene, one lone Tf1-type long terminal repeat (LTR) and one lone Tf2-type LTR. There is a density of one protein-coding gene per 2.2 kb and 22 of the 42 ORFs (52%) incorporate one or more introns. Twenty-one of the novel ORFs show sequence similarities which suggest functions of their products, including a cyclin C, a MADS box transcription factor, mad2-like protein, telomere binding protein, topoisomerase II-associated protein, ATP-dependent DEAH box RNA helicase, G10 protein, ubiquitin-activating e1-like enzyme, nucleoporin, prolyl-tRNA synthetase, peptidylprolyl isomerase, delta-1-pyrroline-5-carboxylate dehydrogenase, protein transport protein, coatomer epsilon, TCP-1 chaperonin, beta-subunit of 6-phosphofructokinase, aminodeoxychorismate lyase, a phosphate transport protein and a thioredoxin.

Complete DNA sequence of a serogroup A strain of Neisseria meningitidis Z2491

Neisseria meningitidis causes bacterial meningitis and is therefore responsible for considerable morbidity and mortality in both the developed and the developing world. Meningococci are opportunistic pathogens that colonize the nasopharynges and oropharynges of asymptomatic carriers. For reasons that are still mostly unknown, they occasionally gain access to the blood, and subsequently to the cerebrospinal fluid, to cause septicaemia and meningitis. N. meningitidis strains are divided into a number of serogroups on the basis of the immunochemistry of their capsular polysaccharides; serogroup A strains are responsible for major epidemics and pandemics of meningococcal disease, and therefore most of the morbidity and mortality associated with this disease. Here we have determined the complete genome sequence of a serogroup A strain of Neisseria meningitidis, Z2491. The sequence is 2,184,406 base pairs in length, with an overall G+C content of 51.8%, and contains 2,121 predicted coding sequences. The most notable feature of the genome is the presence of many hundreds of repetitive elements, ranging from short repeats, positioned either singly or in large multiple arrays, to insertion sequences and gene duplications of one kilobase or more. Many of these repeats appear to be involved in genome fluidity and antigenic variation in this important human pathogen.

The complete nucleotide sequence of chromosome 3 of Plasmodium falciparum

Analysis of Plasmodium falciparum chromosome 3, and comparison with chromosome 2, highlights novel features of chromosome organization and gene structure. The sub-telomeric regions of chromosome 3 show a conserved order of features, including repetitive DNA sequences, members of multigene families involved in pathogenesis and antigenic variation, a number of conserved pseudogenes, and several genes of unknown function. A putative centromere has been identified that has a core region of about 2 kilobases with an extremely high (adenine + thymidine) composition and arrays of tandem repeats. We have predicted 215 protein-coding genes and two transfer RNA genes in the 1,060,106-base-pair chromosome sequence. The predicted protein-coding genes can be divided into three main classes: 52.6% are not spliced, 45.1% have a large exon with short additional 5' or 3' exons, and 2.3% have a multiple exon structure more typical of higher eukaryotes.

Community-based clinical education at the University of Birmingham Medical School

Throughout the United Kingdom, medical schools have begun to make significant changes in the content and delivery of their undergraduate curricula in response to a number of social and educational forces. In particular, many schools have begun to focus increasingly on community-based education. This and other changes mirror developments that have taken place in other countries and in the context of other health care systems, with such forerunners as Harvard, Maastricht, and McMaster having had a fundamental influence. In this article, the authors describe the forces for curricular change in the United Kingdom and the specific recommendations for change made by the General Medical Council. They then discuss in detail the new curriculum at the University of Birmingham medical school, focusing in particular on a community medicine module, where students spend ten days per academic year learning in general medical practices in and around the city of Birmingham.

Deciphering the biology of Mycobacterium tuberculosis from the complete genome sequence

Countless millions of people have died from tuberculosis, a chronic infectious disease caused by the tubercle bacillus. The complete genome sequence of the best-characterized strain of Mycobacterium tuberculosis, H37Rv, has been determined and analysed in order to improve our understanding of the biology of this slow-growing pathogen and to help the conception of new prophylactic and therapeutic interventions. The genome comprises 4,411,529 base pairs, contains around 4,000 genes, and has a very high guanine + cytosine content that is reflected in the biased amino-acid content of the proteins. M. tuberculosis differs radically from other bacteria in that a very large portion of its coding capacity is devoted to the production of enzymes involved in lipogenesis and lipolysis, and to two new families of glycine-rich proteins with a repetitive structure that may represent a source of antigenic variation.

The nucleotide sequence of Saccharomyces cerevisiae chromosome XIII

Systematic sequencing of the genome of Saccharomyces cerevisiae has revealed thousands of new predicted genes and allowed analysis of long-range features of chromosomal organization. Generally, genes and predicted genes seem to be distributed evenly throughout the genome, having no overall preference for DNA strand. Apart from the smaller chromosomes, which can have substantially lower gene density in their telomeric regions, there is a consistent average of one open reading frame (ORF) approximately every two kilobases. However, one of the most surprising findings for a eukaryote with approximately 6,000 genes was the amount of apparent redundancy in its genome. This redundancy occurs both between individual ORFs and over more extensive chromosome regions, which have been duplicated preserving gene order and orientation. Here we report the entire nucleotide sequence of chromosome XIII, the sixth-largest S. cerevisiae chromosome, and demonstrate that its features and organization are consistent with those observed for other S. cerevisiae chromosomes. Analysis revealed 459 ORFs, 284 have not been identified previously. Both intra- and interchromosomal duplications of regions of this chromosome have occurred.

The nucleotide sequence of Saccharomyces cerevisiae chromosome IX

Large-scale systematic sequencing has generally depended on the availability of an ordered library of large-insert bacterial or viral genomic clones for the organism under study. The generation of these large insert libraries, and the location of each clone on a genome map, is a laborious and time-consuming process. In an effort to overcome these problems, several groups have successfully demonstrated the viability of the whole-genome random 'shotgun' method in large-scale sequencing of both viruses and prokaryotes. Here we report the sequence of Saccharomyces cerevisiae chromosome IX, determined in part by a whole-chromosome 'shotgun', and describe the particular difficulties encountered in the random 'shotgun' sequencing of an entire eukaryotic chromosome. Analysis of this sequence shows that chromosome IX contains 221 open reading frames (ORFs), of which approximately 30% have been sequenced previously. This chromosome shows features typical of a small Saccharomyces cerevisiae chromosome.

Acquisition of basic clinical skills in the general practice setting

Undergraduate medical education in the UK is changing due to both education pressure (from the General Medical Council) and changes in the hospital service. As a result the role of general practice in providing core clinical experience is under debate. The purpose of this study was to determine the clinical contact available for junior clinical medical clerks (third year) attached to five general practices. We report here on the clinical experience recorded by students during 106 sessions (74% of possible sessions). One hundred and one patients were seen, 54% females; ages ranging from 14 to 92. Four hundred and twenty-six symptoms were recorded; the largest category (36%) was CVS/respiratory followed by neurological (20%). Shortness of breath was the commonest single symptom (46% in the CVS/respiratory category). Three hundred and seventy-one signs were recorded; 48% were in the CVS/respiratory category, 33% in the neurological category. Cardiac murmurs were the commonest single sign (34% of the CVS/respiratory category). Sixty-nine separate comments were made by students about the range of clinical experience available; all were favourable. Forty-eight per cent of comments highlighted the availability of patients with appropriate symptoms and signs. This study has demonstrated that general practices can provide appropriate clinical exposure which complements hospital teaching for junior students.

Analysis of the structure of original research papers: an aid to writing original papers for publication

BACKGROUND

An increasing number of people involved in medicine are under pressure to publish research, but there is little understanding of how to describe structured writing.

AIM

This paper aims to describe the structure of original research papers published in the British Journal of General Practice with a view to providing insight into the nature of such analyses, and particularly to help researchers and trainers to write and teach writing more successfully.

METHOD

A sample of 50 original papers published in the Journal between January 1989 and March 1993 were examined. The papers were subjected to a form of 'move structure analysis', a technique used in applied linguistics; move structure analysis assigns a tentative function to a piece of text, and identifies words/phrases associated with it. To be recognized, moves thus identified had to occur in the same section of the paper in 65% of the corpus, and/or appear in the same order relative to other moves in 50%.

RESULTS

Fifteen moves were identified, four in the introduction, three in the method, and four each in the results and discussion. These moves functioned, for example in the discussion, to state limitations and defend successes; describe achievements; contextualize procedures and findings; and offer recommendations. Frequency scores ranged from 66% to 100%, and order stability scores from 50% to 80%, with three moves being unordered.

CONCLUSION

It is possible to derive from this study a template for structuring academic medical writing. This template may be built up from the exemplary quotations in the text, to provide assistance to educators and less experienced writers.

A prospective randomized trial comparing the infectious and noninfectious complications of an externalized catheter versus a subcutaneously implanted device in cancer patients

PURPOSE

To compare the frequency of infectious episodes or other problems occurring with an externalized catheter (Hickman) versus a subcutaneously implanted device (Port-a-Cath, Pharmacia, Piscataway, NJ) in cancer patients, we performed a prospective, randomized study in 100 cancer patients (age range, 5 to 74 years).

PATIENTS AND METHODS

Patients who were chemotherapy candidates and required an indwelling catheter were monitored prospectively and evaluated during the 180 days after the insertion of the catheter and again at time of study closure. The frequency of catheter use, reason for access, and any problems that might have been related to catheter use were noted. All data were collected prospectively and included the patient's age, sex, underlying malignancy, temperature, and leukocyte and absolute granulocyte counts at the time of catheter insertion and when complications occurred. The time to and reason for removal of the catheter, as well as any intercurrent infectious or mechanical problems, were also determined.

RESULTS

Most of the infections that occurred were caused by gram-positive organisms, especially staphylococci or streptococci. A total of 22 complications (11 in each group) resulted in removal of the central line. Only one infection in the Hickman catheter group and four in the Port-a-Cath group led to removal of the central line. All other infectious episodes were successfully treated without removal of the catheters. The mean device life was 230 days for the Hickman catheter and 318 days for the Port-a-Cath (not significant).

CONCLUSION

There were no differences between the two study groups regarding incidence of documented infections or mechanical or thrombotic complications.

Amphotericin B vs high-dose ketoconazole for empirical antifungal therapy among febrile, granulocytopenic cancer patients. A prospective, randomized study

We compared high-dose ketoconazole (800 mg/kg per day, orally) with amphotericin B (0.5 mg/kg per day, intravenously) for empirical antifungal therapy in a prospective, randomized study of persistently or recurrently febrile granulocytopenic cancer patients. Among 97 patients eligible for empirical antifungal therapy, 20 (21%) of these patients were ineligible for randomization to ketoconazole treatment because of their inability to tolerate oral medications. Among 72 patients eligible for randomization, 64 were assessable (32 in each arm of the study). Five of six patients with proved fungal infections who were randomized to receive ketoconazole treatment required crossover to amphotericin B treatment because of progressive infection. The conditions of three of these five patients improved after receiving amphotericin B. The frequency of transaminase elevation was higher in those receiving ketoconazole, while the frequency of azotemia was higher in those receiving amphotericin B. Bioavailability of ketoconazole was unpredictable. Amphotericin B remains the drug of choice for empirical antifungal therapy in granulocytopenic patients; whereas, lack of a parenteral formulation, ineffectiveness against proved mycoses, and unreliable bioavailability preclude high-dose ketoconazole from being an appropriate compound for this purpose.

Fungal tracheobronchitis. Report of 9 cases and review of the literature

Clinical, roentgenographic and pathologic findings are described in 9 patients with fungal tracheobronchitis and comparison is made with 25 additional cases in the literature. Two morphologic patterns were identified: the first appears as a pseudomembrane of necrotic tissue, exudate, and fungal hyphae involving more-or-less the entire circumference of the bronchial wall or as mucus/fungus plugs completely occluding the airway lumen; the second consists of single or multiple discrete plaques on the airway wall, sometimes associated with invasion of the adjacent lung parenchyma or pulmonary artery. As with more invasive forms of fungal infection, a compromise in host defenses is probably the most important factor leading to fungal colonization and subsequent local invasion. Malignancies of the hematologic and lymphoreticular systems, solid neoplasms, granulocytopenia, and a history of a protracted course of broad-spectrum antibiotics, corticosteroids, and chemotherapy were present in most of our patients and in those reported in the literature. Despite this, there is some evidence that tracheobronchitis may occur in individuals with a relatively lesser degree of host defense impairment. Local damage to the airway wall such as occurs with prolonged mechanical ventilatory support, neoplastic infiltration, or nonfungal infection may also be a factor predisposing to fungal colonization and invasion. In 4 of our patients, the fungal infection of the tracheobronchial tree probably contributed significantly to the development of terminal respiratory failure. Although recognition of the infection may not have altered the course of the underlying disease in some of our patients, in others identification and early treatment might have been life-saving. Thus, culture and histologic examination of bronchoscopically identified tracheobronchial mucus plugs and necrotic material should be performed in all immunocompromised individuals.

Problems of intensive therapy in childhood cancer

Tremendous progress has been made in the treatment of childhood cancers. Certain hematologic malignancies have an impressive cure rate with the current intensive antineoplastic treatment regimens. There is optimism that the treatment of children who have advanced stage solid tumors with intensive, multimodality therapy may improve their chances for long-term survival. These treatment programs, though potentially curative, are highly toxic, with severe myelosuppression and damage to other organ systems. An awareness of these potential toxicities, an understanding of how to prevent or minimize certain problems, and the ability to treat those complications which do arise are all essential to the successful management of childhood cancer.

Perspective on the management of catheter-related infections in cancer patients

The risk of infectious complications ranges from 9 to 80% depending on patient population and definition of catheter-related infection. In the vast majority of these patients, those infections can be treated successfully without catheter removal. The major exceptions to this guideline are patients with significant exit site or tunnel infections or with fungal isolates. Because the majority of those infections are caused by Gram-positive organisms such as S. epidermidis or S. aureus that have variable sensitivities to the antistaphylococcal penicillins, intravenous vancomycin along with gentamicin should be administered empirically until culture results are available. It appears to be unnecessary to remove the Silastic catheter automatically just because the patient is febrile, particularly if there is no microbiological evidence that the catheter is the source of the fever. Quantitative blood cultures drawn through the catheter and from a peripheral vein may lead to a better understanding of the role the catheter plays in the septic episodes in these patients but has yet to be definitive in identifying patients who absolutely require catheter removal to cure their infection. Surveillance cultures have not proved helpful in defining an "at risk" group for catheter-related infection and, due to cost and possible added risk of inducing an infectious complication, should not be routinely performed outside of an investigational setting. Instruction of patients in proper catheter care both before and after placement is of critical importance. To date there is no proved standard of catheter care and maintenance. There is a need for careful investigation in this area. We recommend that routine handling of the catheter be done with aseptic technique, which usually requires use of Betadine swabs when manipulating the catheter tip and use of a sterile dressing (e.g. E. Med IV Strip) or Op-Site (a transparent occlusive dressing) at the exit site. Continued dressings with either daily, every other day or biweekly changes may protect the catheter from gross contamination but do not protect it from catheter-associated infections. Controlled studies are needed to compare the numerous methods of postplacement catheter management and to determine the rate of infectious complications with the recently available double and triple lumen Silastic catheters and the subcutaneous implantable port-type catheters. We are presently pursuing such an investigation.

New beta-lactam antibiotics in granulocytopenic patients. New options and new questions

Infectious complications are a frequent cause of morbidity and, at many centers, the major cause of death in patients with cancer. The increased risk and severity of infectious sequelae result from profound alterations in normal host defenses that occur secondary to the underlying malignancy and the treatment thereof. During the last decade, early empiric antibiotic therapy has become standard practice in the initial management of febrile granulocytopenic patients and has contributed significantly to the improved outcome among patients undergoing cancer therapy. Although early death due to unsuspected or inadequately treated bacterial infection has been largely overcome, new problems--also with life-threatening implications--have emerged. As the use of cancer chemotherapy continues to increase, new populations of patients are being placed at increased risk of infection. Defining the host and environmental factors that contribute to this risk assumes central importance for delineating those patients who require the most intense surveillance. Changing medical practices (e.g., increased use of indwelling catheters) have contributed to the emergence of new pathogens. Recent drug developments (e.g., the third-generation cephalosporins and extended-spectrum penicillins) offer new treatment options, as well as generate controversy and confusion. For example, authorities disagree on the optimal duration and modifications in treatment that are required by cancer patients who remain granulocytopenic and who thus are at continued risk of multiple infectious episodes or superinfections. A question of current interest is whether combination therapy with synergistic agents is important in light of the development of the third-generation cephalosporins and extended-spectrum penicillins. Several of these new antibiotics have an exceedingly broad spectrum of activity that includes Pseudomonas aeruginosa, as well as Enterobacteriaceae, Serratia, Citrobacter, indole-positive Proteus, and anaerobes (including Bacteroides fragilis). However, the third-generation cephalosporins are not as active against staphylococci and streptococci as are the first-generation cephalosporins, and none is effective against enterococci. Nonetheless, these agents achieve serum levels that can be 10 to 100 times greater than the minimal inhibitory and bactericidal concentrations of gram-negative bacteria, raising the possibility that these drugs might be effective as single agents. The advantages of the third-generation cephalosporins are their minimal toxicity and long serum half-lives.(ABSTRACT TRUNCATED AT 400 WORDS)