Assessment of resistance towards biocides following the attachment of micro-organisms to, and growth on, surfaces

AIMS

To develop a rapid method for the assessment of biocidal activity directed towards intact biofilms.

METHODS AND RESULTS

Escherichia coli and Staphylococcus epidermidis were cultured for up to 48 h within 96-well microtitre plates. The planktonic phase was removed and the wells rinsed. Residual biofilms were exposed to various concentrations of chloroxylenol, peracetic acid, polyhexamethylene biguanide (PHMB), cetrimide or phenoxyethanol for 1 h. At 15-min intervals, biocide was removed, and the wells washed in neutraliser and filled with volumes of fresh medium. Re-growth of the cultures was monitored during incubation at 35 degrees C in the plate reader. Times taken for the treated wells to re-grow to fixed endpoints were determined and related to numbers of surviving cells. Time--survival curves were constructed and the survival of the attached bacteria, following exposure to the agents for 30 min, interpolated for each biocide concentration. Log--log plots of these survival data and biocide concentration were constructed, and linear regression analysis performed in order to (i) calculate concentration exponents and (ii) compare the effectiveness of the biocides between variously aged biofilm and planktonic cells. From such analyses iso-effective concentrations of biocide (95% kill in 30 min) were calculated and expressed as planktonic : biofilm indices (PBI).

CONCLUSION

PBI varied between 1.02 and 0.02, were relatively unaffected by age of the biofilms but differed significantly between organism and biocide. Notably those compounds with the higher activity against planktonic bacteria (PHMB and peracetic acid) were most prone to a biofilm effect but remained the most effective of the agents selected.

SIGNIFICANCE AND IMPACT OF THE STUDY

The endpoint method proved robust, enabled the bactericidal effects of the biocides to be assessed against in-situ biofilms, and was suitable for routine screening applications.

An exploration of evolved mental mechanisms for dominant and subordinate behaviour in relation to auditory hallucinations in schizophrenia and critical thoughts in depression

BACKGROUND

Mental mechanisms have evolved to enable animals (and humans) to be able to function in various social roles. It is suggested that the nature and functions of the mental mechanisms that enable animals to act as a hostile-dominant or threatened-subordinate can be distinguished. It is further suggested these can be internally activated and 'play off' against each other, such that a person 'attacks' themselves and then responds to their own internal attacks with subordinate defences. Hence, a depressed person can submit, feel defeated, belittled, beaten down, or want to run away (escape) from their own self-attacking thoughts, while psychotic voice hearers can feel similarly to their hostile voices. Such internal interactions may relate to depression in both psychotic voice hearers and depressed people.

METHOD

A group of 66 voice hearers with a diagnosis of schizophrenia and 50 depressed patients were compared on a series of self-report questionnaires measuring the power of hostile self-directed thoughts/voices and the activation of defensive responses, especially fight/flight.

RESULTS

We present evidence that schizophrenic, malevolent voice hearers and self-critical depressed people experience their hostile, internally generated voices/thoughts as powerful, dominating and controlling (i.e. have typical characteristics of a hostile dominant). Moreover, these voices/thoughts activate evolved subordinate defences such as fight/flight and these are associated with depression in both depression and schizophrenia.

CONCLUSION

Conceptualizing aspects of depressed and psychotic thinking as relating to evolved mental mechanisms, which are role serving, but can internally play off against each other, may open new ways of investigating certain aspects of severe pathologies.

Prevalence and predictive value of intermittent viremia with combination hiv therapy

CONTEXT

In HIV-infected patients having virologic suppression (plasma HIV RNA <50 copies/mL) with antiretroviral therapy, intermittent episodes of low-level viremia have been correlated with slower decay rates of latently infected cells and increased levels of viral evolution, but the clinical significance of these episodes is unknown.

OBJECTIVE

To determine if HIV-infected patients with intermittent viremia have a higher risk of virologic failure (confirmed HIV RNA >200 copies/mL).

DESIGN AND SETTING

Retrospective analysis of subjects in well-characterized cohorts, the AIDS Clinical Trials Group (ACTG) 343 trial of induction-maintenance therapy (August 1997 to November 1998) and the Merck 035 trial (ongoing since March 1995).

PATIENTS

Two hundred forty-one ACTG 343 patients, of whom 101 received triple-drug therapy throughout the study, and a small group of 13 patients from Merck 035 having virologic suppression after 6 months of indinavir-zidovudine-lamivudine.

MAIN OUTCOME MEASURES

Association of intermittent viremia (plasma HIV RNA >50 copies/mL with a subsequent measure <50 copies/mL) with virologic failure (2 consecutive plasma HIV RNA measures >200 copies/mL) in both study groups; evidence of drug resistance in 7 patients from the small (n = 13) study group with long-term follow-up.

RESULTS

Intermittent viremia occurred in 96 (40%) of the 241 ACTG 343 patients of whom 32 (13%) had 2 consecutive HIV RNA values >50 copies/mL during the median 84 weeks of observation (median duration of observation after first intermittent viremia episode was 46 weeks). Of the 101 individuals receiving triple-drug therapy throughout, 29% had intermittent viremia; the proportion of episodes occurring during the maintenance period was 64% for the entire cohort and 68% for the group not receiving triple-drug therapy throughout vs 55% for those who did (P =.25). Intermittent viremia did not predict virologic failure: 10 (10.4%) of 96 patients with and 20 (13.8%) of 145 patients without intermittent viremia had virologic failure (relative risk, 0.76; 95% confidence interval [CI], 0.29-1.72). In a Cox proportional hazards model, the risk for virologic failure was not significantly greater in the ACTG 343 patients with intermittent viremia (hazard ratio, 1.28; 95% CI, 0.59-2.79). Median viral load in 10 ACTG 343 patients assessed between 24 and 60 weeks of therapy using an ultrasensitive 2.5-copies/mL detection level assay was 23 copies/mL in those with intermittent viremia vs <2.5 copies/mL in those without (P =.15). Intermittent viremia occurred in 6 of 13 patients from the small study group assessed after 76 to 260 weeks of therapy (using the 2.5-copies/mL detection level assay) and was associated with a higher steady state of viral replication (P =.03), but not virologic failure over 4.5 years of observation. Viral DNA sequences from 7 patients did not show evolution of drug resistance.

CONCLUSIONS

Intermittent viremia occurred frequently and was associated with higher levels of replication (Merck 035), but was not associated with virologic failure in patients receiving initial combination therapy of indinavir-zidovudine-lamivudine (ACTG 343 and Merck 035). In this population, treatment changes may not be necessary to maintain long-term virologic suppression with low-level or intermittent viremia.

Menstruation in schoolgirls--1: The normal menarche

The mean age for onset of menstruation (menarche) is 12.8 years. Many schools teach girls about puberty and menstruation and prepare them for the menarche. The school nurse has a valuable part to play in all aspects of menstruation in schoolgirls, psychological as well as physical. The early periods may be irregular and vary markedly in the amount of blood loss. It can take up a year or more for a steady pattern to develop. Dysmenhorrhoea may occur, which may be mild or of the severe spasmodic type. Premenstrual tension syndrome is less common in schoolgirls. Girls should be taught about the importance of hygiene, especially if tampons are used.

Depression and stress: a biopsychosocial exploration of evolved functions and mechanisms

Depression is a common and debilitating disorder linked to social adversity and stress. There have been many theories suggesting possible evolved functions of depression but few have explored evolved defensive mechanisms for coping with stressful events and how these maybe compromised in human depression. This paper will review some of the current evolutionary theories of depression and explore how major depression can arise when evolved defences to cope with adversity (e.g., fight, flight, disengage, submit and help-seeking) are aroused but blocked, arrested or ineffective. Psychosocial stressors can be seen as both activating,but also as arresting, evolved stress-coping defences leading to chronic states of stress with physiological effects on mood. This paper is set in the context of an evolution informed biopsychosocial approach.

Evolutionary approaches to psychopathology: the role of natural defences

OBJECTIVE

Psychoanalytic theories of the mind emerged in the immediate post-Darwinian era of the 1880s and 1890s. Since that time much has changed in both psychoanalytic and evolutionary theorizing. This paper explores recent evolutionary thinking on psychopathology.

METHOD

Relevant literature was reviewed.

RESULTS

This paper outlines some of the common behavioural defence mechanisms and then explores ways in which they are represented in various disorders, with a focus on depression. This paper suggests that 'symptoms' can be related to the activation of evolved defence mechanisms to respond to losses and threats. Such will involve, for example, anxious arousal and heightened vigilance and attention to the threat, with the type of defence (e.g. fight, flight, submit, help seeking) being mirrored in particular symptom presentations.

CONCLUSION

Defences can become pathological when they are too easily aroused or prolonged, are arrested (aroused but not expressed) and/or ineffective.

Sieve analysis: methods for assessing from vaccine trial data how vaccine efficacy varies with genotypic and phenotypic pathogen variation

A key component in the evaluation of efficacy of a vaccine to protect against disease caused by an antigenically diverse infectious pathogen in a preventative vaccine trial is assessing how vaccine-induced protection depends on genotypic and phenotypic variations of the exposing pathogen. This assessment is made by comparing pathogen isolates between infected vaccinated subjects and infected unvaccinated subjects. A survey of efficacy trial reports reveals a lack of systematic, quantitative investigation in this question. Analysis tools for testing if vaccine protection against disease is superior against some pathogen strains, and for estimating the magnitude of this differential vaccine protection, are described. The broad applicability of the methods is illustrated through analysis of isolates taken from persons infected while participating in vaccine trails for cholera, HIV-1, hepatitis B, rotavirus, and pneumococcus. These analyses reveal intriguing trends for Genentech's monovalent rgp120 HIV-1 vaccine, for two whole-killed-cell oral cholera vaccines, and for other vaccines.

The molecular epidemiology of HIV type 1 of men in Mexico

Genotypic characteristics of human immunodeficiency virus type 1 (HIV-1) in Mexico were investigated in a multicenter study that involved centers in five geographic regions of the country. Study samples (n = 65) collected from male patients in 1998-1999 were sequenced within the C2-V5 region of the gp120 env gene. Phylogenetic analysis revealed that subtype B predominates in Mexico. The level of interpatient nucleotide diversity (mean value of 8.9%) was congruent with multiple introductions of the virus and the "aging" epidemic in Mexico. One-third of samples (30.8% of cases) showed polymorphism within the crown of the V3 loop demonstrating non-GPGR motifs. Two new motifs in the V3 loop crown - HPGG and GPEG - were observed. The evolution of the AIDS epidemic in Mexico should be closely monitored since non-B HIV-1 subtypes might be introduced. The nucleotide sequences were deposited in the GenBank under accession numbers AF200855-AF200869, AF200871-AF200892, and AF200894-AF200921.

The effect of a rapid change in availability of epidural analgesia on the cesarean delivery rate: a meta-analysis

OBJECTIVE

This study was undertaken to quantitatively estimate the effect of a rapid introduction or withdrawal of on-demand epidural analgesia on the cesarean delivery rate.

STUDY DESIGN

MEDLINE and meeting abstracts were searched for studies reporting the cesarean delivery rate immediately before and after a rapid change in the availability of epidural analgesia. Nine studies reporting data on 37,753 patients were selected. Meta-analysis was performed to estimate the means and 95% confidence intervals for the changes in rates of total cesarean deliveries, cesarean deliveries among nulliparous women, cesarean deliveries for dystocia, and operative vaginal deliveries.

RESULTS

There was no significant change in the overall cesarean delivery rate with an increase in the availability of epidural analgesia. Similarly, the rates of cesarean deliveries among nulliparous patients, of cesarean deliveries for dystocia, and of operative vaginal deliveries did not significantly differ between periods of high and low epidural analgesia availability.

CONCLUSION

A rapid change in the availability of epidural analgesia is not associated with any increase in the cesarean delivery rate.

An evaluation of the potential of the multiple antibiotic resistance operon (mar) and the multidrug efflux pump acrAB to moderate resistance towards ciprofloxacin in Escherichia coli biofilms

The chromosomal multiple antibiotic resistance operon, mar, is widely represented amongst Gram-negative bacteria and has been implicated in resistance towards oxidative stress agents, organic solvents and a large number of structurally unrelated antimicrobial agents. The major mechanism associated with such increased resistance is an upregulation of the efflux pump acrAB. Growth as a biofilm is often associated with similar generalized reductions in susceptibility to inimical agents. Escherichia coli K12 (AG100), an isogenic mutant of AG100 constitutive for mar expression (AG102) and an isolate deleted of the mar locus (MCH164) were grown as biofilms in cellulose-fibre depth filters and perfused with a simple salts, minimal medium (CDM) over 120 h. Biofilms were exposed to various concentrations of ciprofloxacin (0.004, 0.015 and 0.1 mg/L) for 42 h. The numbers of viable cells within the perfusate and within the biofilm were estimated throughout. Whereas no differences were seen between the wild-type and mar-deleted isolates, that constitutive for mar displayed reduced susceptibility to ciprofloxacin at concentrations of 0.004 mg/L (MIC for AG100 was 0.0052 mg/L). Similar antibiotic perfusion experiments were conducted using isolates in which the efflux pump acrAB was either deleted (AG100-A) or constitutively expressed (AG100-B). Exposure of AG100-A biofilms to ciprofloxacin at 0.004 and 0.1 mg/L showed similar susceptibilities to those seen in the wild-type (AG100) and mar-deleted (MCH164) isolates and suggested that acrAB was not induced within the attached population. On the other hand, constitutive expression of acrAB (AG100-B) protected biofilms against the lower concentration of ciprofloxacin used (0.004 mg/L). This protection was again lost at concentrations of 0.1 mg/L. Overall, these results show that ciprofloxacin resistance in biofilms is not mediated by the upregulation of the mar or acrAB operons.

The power and omnipotence of voices: subordination and entrapment by voices and significant others

BACKGROUND

Cognitive therapy for psychotic symptoms often embraces self-evaluative beliefs (e.g. self-worth) but whether and how such beliefs are related to delusions remains uncertain. In previous research we demonstrated that distress arising from voices was linked to beliefs about voices and not voice content alone. In this study we examine whether the relationship with the voice is a paradigm of social relationships in general, using a new framework of social cognition, 'ranking' theory.

METHOD

In a sample of 59 voice hearers, measures of power and social rank difference between voice and voice hearer are taken in addition to parallel measures of power and rank in wider social relationships.

RESULTS

As predicted, subordination to voices was closely linked to subordination and marginalization in other social relationships. This was not the result of a mood-linked appraisal. Distress arising from voices was linked not to voice characteristics but social and interpersonal cognition.

CONCLUSION

This study suggests that the power imbalance between the individual and his persecutor(s) may have origins in an appraisal by the individual of his social rank and sense of group identification and belonging. The results also raise the possibility that the appraisal of voice frequency and volume are the result of the appraisal of voices' rank and power. Theoretical and novel treatment implications are discussed.

Expression of the multiple antibiotic resistance operon (mar) during growth of Escherichia coli as a biofilm

The multiple antibiotic resistance (mar) operon is a global regulator controlling the expression of various genes in Escherichia coli which constitutes the mar regulon. Upregulation of mar leads to a multi-drug resistant phenotype, which includes resistance towards structurally unrelated antibiotics, organic solvents and the disinfectant pine oil. Biofilms also display similar decreases in susceptibility to antimicrobial agents. A marOII-lacZ fusion strain (SPC105) of E. coli was used to monitor mar expression under various growth conditions including batch, continuous and biofilm culture. In chemically-defined media (CDM), mar expression was maximal in mid-log and declined in the stationary phase. Conversely, in rich media (Luria-Bertani broth), minimal expression in mid-log was followed by an increase in the stationary phase. In continuous culture, expression was inversely related to specific growth rate (mu = 0.05-0.4 h-1). LacZ expression by the marOII-lacZ fusion was generally low within the total biofilm population and equivalent to that of stationary phase cultures grown in batch culture. When the expression of mar in CDM batch culture was compared with that in biofilm populations, beta-galactosidase activity was generally higher throughout batch culture than in the attached population. Overall, these results suggest that while mar expression will be greatest within the depths of a biofilm where growth rates are suppressed, its probable induction within biofilms cannot explain the elevated levels of antibiotic resistance observed.

Recall of shame and favouritism in relation to psychopathology

OBJECTIVES

There is good evidence that early rearing experiences affect vulnerability to subsequent psychopathology. Recent research on memories of rearing style have been influenced by attachment theory and have focused primarily on domains of emotional warmth and control. However, early experiences of being shamed, criticized and made to feel inferior, together with believing one's sibling is favoured over oneself, are also likely to play a role in vulnerability. This study therefore explored recall of being shamed and sibling favouritism.

METHOD

A large community sample (N = 638) and a varied non-psychotic patient sample (N = 213) completed two recall of parent rearing scales (the PBI and EMBU). These gave measures of recall of emotional warmth, overprotection/control, being shamed and shown up, and self or sibling favouring. Participants also completed the SCL-90-R scale.

RESULTS

Patients recalled less warmth, more control, more shame and more favouring of siblings than the community sample. The difference was greatest for shame, and following MANOVA analysis shame remained significantly different between the two groups even after controlling for emotional warmth and control. Similarly, recalling being less favoured than a sibling and shamed had robust associations with indicators of psychopathology and these were only marginally reduced when emotional warmth was controlled for. Moreover, hostility (as measured by the SCL-90-R) was specifically related to recall of being shamed but not emotional warmth.

CONCLUSION

This study suggests that over and above issues of emotional warmth and control, recall of direct experiences of being shamed, feeling inferior and less favoured in a family, may be particularly pathogenic. They operate independently of warmth and may be especially important in proneness to hostile feelings. Given this, therapists may wish to specifically explore shame issues with patients.

Emerging recombinant human immunodeficiency viruses: uneven representation of the envelope V3 region

OBJECTIVE

To determine whether the envelope V3 region from HIV-1 subtypes A, C or D had the same probability of being present in intersubtype recombinant genomes.

MATERIALS AND METHODS

The envelope C2-C5 and the gag p24-p7 regions from one hundred infants infected perinatally in Tanzania were compared using phylogenetic and recombination analysis. Exact binomial and Fisher's exact tests were used to assess if various genomic regions were more likely to be overrepresented in intersubtype recombinants.

RESULTS

Of one hundred HIV-1 positive infants analyzed, twenty-two (22%) showed exclusively subtype A sequence in gag and env. Subtype C accounted for twenty-two infants (22%) whereas nineteen infants (19%) were infected by HIV-1 subtype D. Intersubtype recombinant genomes accounted for thirty-seven infections (37%). The V3 region from subtype A was found in all fifteen A-D recombinants (P = 0.00003) and the V3 region from subtype C was found in all twelve C-D recombinants (P = 0.0002). Conversely, subtype D gag sequences were preferentially represented in the gag of A-D recombinants (P = 0.0003) as well as C-D recombinants (P = 0.002). In A-D recombinants, the V3 region of subtype A was generally surrounded by subtype A C3-C5 sequences. In contrast, the V3 region from subtype C was surrounded by subtype D C3-C5 sequences in C-D recombinants. Significant differences were not found in the number of subtype A or subtype C sequences in A-C recombinants.

CONCLUSION

We have shown that several recombinant HIV-1 viruses have been generated and efficiently transmitted to infants in Tanzania. The recombination patterns showed that the V3 region of subtypes A or C was always selected in A-D and C-D recombinants. This selection suggests that the fitness of subtype D-V3 in perinatal transmission may be reduced with respect to V3 from subtype A and/or subtype C. The elevated number of recombinants transmitted perinatally suggests that co-infection or super-infection by two HIV-1 subtypes is not uncommon in this population.

A murine model of myocardial microvascular thrombosis

Disorders of hemostasis lead to vascular pathology. Endothelium-derived gene products play a critical role in the formation and degradation of fibrin. We sought to characterize the importance of these locally produced factors in the formation of fibrin in the cardiac macrovasculature and microvasculature. This study used mice with modifications of the thrombomodulin (TM) gene, the tissue-type plasminogen activator (tPA) gene, and the urokinase-type plasminogen activator (uPA) gene. The results revealed that tPA played the most important role in local regulation of fibrin deposition in the heart, with lesser contributions by TM and uPA (least significant). Moreover, a synergistic relationship in fibrin formation existed in mice with concomitant modifications of tPA and TM, resulting in myocardial necrosis and depressed cardiac function. The data were fit to a statistical model that may offer a foundation for examination of hemostasis-regulating gene interactions.

Concomitant Block of the Rapid (I(Kr)) and Slow (I(Ks)) Components of the Delayed Rectifier Potassium Current is Associated With Additional Drug Effects on Lengthening of Cardiac Repolarization

BACKGROUND: The delayed rectifier potassium current, which comprises both a rapid (I(Kr)) and as slow (I(Ks)) component, is a major outward current involved in repolarization of cardiac myocytes. I(Kr) is the target of most drugs that prolong repolarization, whereas electrophysiological effects resulting from combined block of I(Kr) and I(Ks) still need to be characterized. METHODS AND RESULTS: Studies in isolated, buffer-perfused guinea pig hearts were undertaken to compare lengthening of cardiac repolarization under conditions of I(Kr) block alone, I(Ks) Block alone, or combined block of I(Kr) and I(Ks). In protocol A, isolated perfusion with N-acetylprocainamide (NAPA) (I(Kr) block), indapamide (I(Ks) block), or combined NAPA/indapamide was performed at a pacing cycle length of 250 msec. Increases in monophasic action potential duration measured at 90% polarization (MAPD(90)) from baseline after perfusion with NAPA 100 µmol/L (IC(50) for block of I(Kr)) was 19 +/- 6 msed (P <.05), after indapamide 100 µmol/L (EC(50) for block of I(Ks)) 13 +/- 2 msec (P <.05), but 42 +/- 5 msec after combined NAPA 100 µmol/L and indapamide 100 µmol/L (P <.05 vs. baseline and isolated administrations), suggesting the possibility of excessive lengthening of cardiac repolarization by blocking both I(Kr) and I(Ks). As well, in protocol B where sequential perfusions with dofetilide (I(Kr) blocker), dofetilide/indapamide, and indapamide in the same hearts were used, combined dofetilide/indapamide infusion showed a greater increase in MAPD(90) during all pacing cycles studied (250 to 150 msec). CONCLUSIONS: Combined I(Kr) and I(Ks) block may lead to excessive lengthening of cardiac repolarization. This may predispose patients to proarrhythmia during coadministration of drugs.

Evolutionary psychopathology: why isn't the mind designed better than it is?

This paper outlines some of the basic issues in evolutionary thinking when applied to psychopathology. It aims to give some background and context to the papers that follow. Particular attention is given to the way evolution is constrained by previous design features, the importance of trade offs between advantages and disadvantages of different traits, the way social dilemmas and conflicts have shaped the evolution of human motivational systems, and the psychology that supports them. The paper concludes with a plea to avoid thinking of evolutionary approaches as a reductionist science, when the focus needs to be on the way evolution theory informs the study of the social-biological interface.

The evolved basis and adaptive functions of cognitive distortions

This paper explores common cognitive distortions from the perspective of evolutionary psychology. It is suggested that cognitive distortions are natural consequences of using fast track defensive algorithms that are sensitive to threat. In various contexts, especially those of threat, humans evolved to think adaptively rather than logically. Hence cognitive distortions are not strictly errors in brain functioning and it can be useful to inform patients that 'negative thinking' may be dysfunctional but is a reflection of basic brain design and not personal irrationality. The evolved nature of cognitive distortions has been implicit in cognitive therapy from its early days (Beck, 1963; Ellis, 1962) but has not been fully articulated in what is now known about evolved mental processes. Many forms of cognitive distortion can be seen to use the (previously) adaptive heuristic of better safe than sorry.

Performance evaluation of disinfectant formulations using poloxamer-hydrogel biofilm-constructs

Poloxamer F127 is a di-block co-polymer of polyoxyethylene and polyoxypropylene. Aqueous solutions show thermo-reversible gelation, being liquid at temperatures < 15 degrees C and robust gels at temperatures > 15 degrees C. Chilled poloxamer solutions (30% w/v) were inoculated with approximately 10(4-5) cfu ml-1 of stationary phase cultures of Pseudomonas aeruginosa, Ps. fluorescens, Pantoea agglomerans, Micrococcus luteus, Staphylococcus epidermidis, Bacillus subtilis or Listeria innocua. Drops (200 microliters) of the inoculated poloxamers were placed on stainless steel coupons held in Petri dishes containing moistened cotton wool and incubated at 30 degrees C for 5 h. All strains grew well giving between 10(6-7) cfu ml-1 at 5-6 h. The cultured gels were readily applied to tests of biocide effectiveness as the stainless steel coupons could be removed and flooded with biocide solution for fixed exposure times. Provided that the temperature of the biocide solutions was > 15 degrees C, the integrity of the gels could be maintained during exposure. After exposure, the gels and their supports were removed to separate tubes containing neutralizer solution (< 15 degrees C). The gels rapidly dispersed within 5 min to ensure a complete recovery of the sample population. Biofilm-constructs and cell suspensions (10(7) cfu ml-1) were exposed to four commercial disinfectant formulations, based on hypochlorite, alcohol, hydrogen peroxide and a tenside, at recommended use levels. Cell suspensions, in the presence of bovine serum albumen (BSA; 0.03% w/v), were subject to a > 5-log kill within 5 min while the killing effected against the biofilm-constructs varied between 0.4 and 2-log reductions. The results indicate a high degree of reproducibility between replicate samples, with patterns of susceptibility varying both as a function of organism, biocide type and concentration. The experiments strongly support the view that poloxamer-constructs are suitable for application in trials and testing of disinfectant formulations.

The use of poloxamer hydrogels for the assessment of biofilm susceptibility towards biocide treatments

Poloxamer F127 is a non-toxic, di-block copolymer of polyoxyethylene and polyoxypropylene. Aqueous solutions (30% w/v) show thermoreversible gelation, being liquid at temperatures < 15 degrees C and robust gels at temperatures > 15 degrees C. Chilled poloxamer (30% in tryptone soya broth) was mixed with an inoculum of Pseudomonas aeruginosa (10(4) cfu ml-1) and placed as 100 microliters drops onto separate glass cover-slips. These were placed into sealed Petri dishes containing moistened cotton wool and incubated at 35 degrees C. Viable counts could be performed on the poloxamer gels by transfer of the coverslips to diluents at < 15 degrees C. Growth curves in the gels and in liquid batch cultures were indistinguishable from one another with stationary phase cell densities, being approximately 5 x 10(10) cfu ml-1 in each at 16 h. SDS-PAGE of cell envelope preparations showed the poloxamer-grown cells to exhibit a biofilm rather than planktonic phenotype. Susceptibility towards various concentrations of chlorhexidine, iodine and hydrogen peroxide was assessed for 10 min at 35 degrees C for suspensions of broth-grown cells and for incubated poloxamer-gels (1 and 16 h). The gels were immersed in biocide, on their glass supports, before transfer to neutralizer at 10 degrees C where dissolution was complete within 5 min. Further serial dilutions and plate counts were made. While modest decreases in susceptibility towards all biocides were associated with incorporation of the inoculum with the gel (1 h incubation), substantial changes were noted after prolonged incubation and adaptation to a biofilm phenotype (16 h incubation). The gel populations mimic the localized high cell densities observed in biofilms and will also be subject to the same nutrient and chemical gradients as found within natural biofilms. Thermoreversible gelation enables complete recovery of the test inoculum without further trauma. They therefore provide an effective model for assessing biofilm susceptibility towards biocides and would be suitable for screening programmes.

Skin problems and parasites in children: 2. Parasitic worms

The skin is an organ which has many important functions for body maintenance and health. Infestation by a wide variety of worms is a worldwide public health problem. Threadworms are believed to infect up to 50% of London school children. Dogs and other pets have much to teach children but regular care of pets should include attention to hygiene. Nurses and midwives can help to educate the public about worms and their advice can help prevent toxocara infections.

Skin problems in children: 1. Infections in the early years

The skin is an organ which has many important functions for body maintenance and health. The condition of the skin is a good indicator of health and disease. A rash has many diagnostic features. Bacteria, virus and fungi all give rise to specific effects on the skin. Some skin infections are localised, affecting only a small area of skin, while others cover extensive areas of the body. Some skin infections are systemic, ie affect the body as a whole, often producing both internal and external symptoms. A sound knowledge of skin infections will enable the nurse or midwife to give the parents appropriate advice and reassurance, and to make appropriate referrals.

Common feeding problems in babies and children: 2

Weaning is the cause of much concern among first-time mothers. A milk-only diet is advised until 3-4 months of age. Health professionals should ensure the baby receives a sufficient and balanced diet during the weaning period, to meet the needs for energy and growth. Breast milk or infant formula should continue up to the age of at least one year. The weaning period is a good time to educate parents in good nutrition. A wide variety of foods should be the aim in child nutrition, but each different type needs to be started separately during weaning. Care is needed to ensure vegetarian babies receive enough proteins, vitamins and minerals (especially iron). Failure to thrive has a multitude of causes, and treatment must be that of the cause. Strictly vegan children who eat no dairy products will need added synthetic vitamin B12. Failure to thrive may be due to physical problems (eg choanal atresia), infection, vomiting, diarrhoea, anorexia, parental ignorance or poverty. Other causes include coeliac disease, cow's milk protein allergy, cystic fibrosis, severe eczema or asthma, or diabetes.

Extracellular products as mediators of the formation and detachment of Pseudomonas fluorescens biofilms

Pseudomonas fluorescens B52 produces substantial biofilms at the air/liquid/solid interface of glass coverslips clamped vertically and partly submerged in liquid medium at 21 degrees C. Biofilm formation was maximal ca. 20-50 h after inoculation of the liquid medium and as indicated by environmental scanning electron microscopy (ESEM), contained large numbers of bacterial cells that were embedded within an extensive exopolymeric matrix. Incubation beyond 50 h led to reductions in biofilm which ESEM related primarily to losses of exopolymer. Both biofilm formation and the subsequent decline in exopolymer deposition was more rapid, and occurred to greater extents, when supernatants from two-day old cultures of B52 were used as the initial growth media. The addition of N-acyl-hexanoyl homoserine lactone to fresh growth medium had a similar effect upon biofilm formation as using spent culture medium. Homoserine lactones could not be demonstrated in spent culture supernatants by an Agrobacterium tumefaciens bioassay. An exopolysaccharide lyase was detected in spend culture media taken from dense biofilm cultures whose action was specifically directed towards biofilm exopolysaccharide. Results suggest that (i) cell-cell signals such as homoserine lactones are associated with the formation of P. fluorescens biofilms, (ii) the enzymic degradation of exopolymers has a specific role in the detachment of cells under starvation conditions, and (iii) whilst short chain (C6) exogenous homoserines can trigger such response in P. fluorescens, its own signal substance is likely to possess a longer (> C8) fatty acyl chain.

Changes in the strength of attachment of micro-organisms to surfaces following treatment with disinfectants and cleansing agents

Suspensions of Pseudomonas aeruginosa and Staphylococcus epidermidis, and biofilms established (16 h) on submerged glass and stainless steel (216 2B) coupons, were exposed to sodium hypochlorite (0.02% or 0.015% w/v), Dodigen (0.0015% w/v or 0.0006% w/v), sodium dodecylsulphate (6% w/v or 0.1% w/v) and Tween-80 (6% w/v) for 5 min at 20 degrees C. Survival was assessed by viable counts and blot succession. Biofilm bacteria were significantly less susceptible to these biocides than were planktonic cells, but their attachment to the surfaces was loosened by such treatments. Treatment with the non-ionic surfactant, Tween-80, however, strengthened the attachment of Staph. epidermidis to stainless steel. Such effects on attachment strength, which are species and surface dependent, have profound implications on post-treatment cleansing and possible re-contamination of product in clean-in-place (CIP) systems.

Efficient trial designs for studying combination antiretroviral treatments in patients with various resistance profiles

Selecting antiretroviral therapies for human immunodeficiency virus type 1-infected persons is complicated by the availability of a vast number of potentially useful drug combinations and by extensive variation among patients in their resistance to various drugs. AIDS clinical trials have used designs in which a handful of drug regimens in a few patient classes can be compared. Here is proposed implementation of innovative designs with factorial structure that permit assessment of many treatment arms and patient classes in a single trial; when and how they can be appropriately used are discussed. These designs are efficient, permit systematic investigation of correlations between genetic mutations and in vivo drug resistance, and provide insight into important drug interactions in people that conventional designs are unable to provide. Through creative application of these designs, identification of superior drug combinations and the science of understanding in vivo joint drug dynamics and genotypic resistance will progress at an optimum pace.

Surface-catalysed disinfection of thick Pseudomonas aeruginosa biofilms

Transition metal catalysts were incorporated into polymers which formed the surface for bacterial attachment and biofilm formation in a constant depth film fermenter (100 microns thickness), flow chamber (about 30 microns thickness) and in batch culture (< 30 microns thickness). The catalysts drive the breakdown of persulphates to reactive oxygen species. When Pseudomonas aeruginosa biofilms were exposed to dilute solutions of potassium monopersulphate (20 micrograms ml-1-1 mg ml-1), significant enhancement of killing was notable for catalyst-containing surfaces over that of controls. The degree of enhancement was greatest for thin films, but was nevertheless significant for the 100 microns thick biofilms. Fluorescence probes and viability staining, in conjunction with laser confocal microscopy, showed that reactive species were generated at the biofilm-substratum interface and killed the biofilm from the inside. Reaction-diffusion limitation now concentrates the active species within the biofilm rather than protecting it, and a diffusion bump is established whereby further treatment agent is drawn to the substratum enabling relatively thick biofilms to be disinfected.

Determination of 226Ra in mineral drinking waters by alpha liquid scintillation with rejection of beta-gamma emitters

The radiotoxicity of radium isotopes (especially the long-half-life 226Ra) requires their monitoring in drinking waters or nuclear wastes. We studied the applicability of the PERALS method of detection (photon electron rejecting alpha liquid scintillation) for radium measurement. This method combines alpha liquid scintillation with pulse shape analysis for beta rejection and specific chemical extractants included in the scintillating cocktail. Radium is separated by an extractive-scintillator cocktail called RADAEX containing 2-methyl-2-heptylnonanoic acid (HMHN) and dicyclohexano-21-crown-7 (Cy(2)21C7) as extractant molecules. The variation of the radium extraction has been studied relative to pH, salt concentrations, anion and cation effects, and the volume ratio between aqueous and organic phases. The main parameter affecting the radium extraction in mineral drinking water is its complexation by inorganic anions, especially sulfate. Due to the lack of thermodynamic data, some complexation constants had to be determined. For instance, the value reported in this paper for radium sulfate (log beta = 2.58 +/- 0.22) is in good agreement with that from the literature. The knowledge of complexation constants allows the determination of radium extraction recovery for any solution when the inorganic anion concentrations had been measured by capillary zone electrophoresis. The detection limit for this technique is found to be equal to 0.006 Bq.L-1 using only 6 mL of sample solution for analysis. Several French mineral waters have been studied and the results compared with determinations of uranium and thorium concentrations by ICPMS and time-resolved laser induced fluorescence (TRLIF).

Nurse triage for house call requests in a Tyneside general practice: patients' views and effect on doctor workload

BACKGROUND

Demand for consultations in primary care has risen recently, necessitating a change in working practices. As part of this process, the possible contribution of practice nurses in the telephone assessment of home visit requests merits attention.

AIMS

To survey the views of our patients encountering our nurse triage system for home visit requests, set up in June 1995, and to plot its effect on the routine visiting workload of our doctors and thus their availability at the surgery.

METHOD

The outcome of each request was categorized as: doctor to visit (DV), surgery consultation with doctor (SC), nurse advice given and accepted (NA), or call passed to doctor for advice (DA). Frequency data from September 1995 to December 1996 were recovered. Questionnaires for self-completion were sent to all those requesting a routine weekday house call during two four-week periods in 1995 and 1996.

RESULTS

Analysable activity data revealed 1764 house call requests, with 41% DV, 18% SC, 24% NA, and 8% DA. In the first survey, 121 questionnaires were sent out and 84 returned (69% response rate) and, in the second, the corresponding figures were 113, 85, and 75%. About 80% of responders reported that they were satisfied with the help received from the nurse.

CONCLUSIONS

Nurse triage of house call requests has led to more efficient care for our patients, as we have increased the availability of surgery consultations by reducing the number of house calls made by our general practitioners.

Changes in the biocide susceptibility of Staphylococcus epidermidis and Escherichia coli cells associated with rapid attachment to plastic surfaces

Differences in opacity between wells of a microtitre plate containing different volumes of inoculated growth medium reflected planktonic growth without any contribution from cells attached at the well surface. Simple algebra and a knowledge of the dependence of optical density upon sample path length (volume) for suspensions of differing cell density enables the generation of growth curves for attached populations (biofilms). In this manner, minimum inhibitory concentrations (MICs) were determined at various stages of growth (0-20 h), both for cells growing attached to the bases of the plate wells and, simultaneously, for cells growing in suspension above them. Biocides included cetrimide, polyhexamethylene biguanide, peracetic acid, phenoxyethanol and chloroxylenol. Results, expressed as planktonic:biofilm MIC ratios, showed susceptibility to change, not only as a function of attachment and biofilm formation, but also with respect to the nature of the chemical agent. In some instances, changes in susceptibility greater than twofold occurred immediately on attachment and could occur in the presence of biocide concentrations which exceeded the MIC.

The role of defeat and entrapment (arrested flight) in depression: an exploration of an evolutionary view

BACKGROUND

The social rank theory of psychopathology suggests that with the evolution of social hierarchies various psychobiological mechanisms became attuned to the success or failure in conflict situations. Specifically, subordinates and those who have lost status are at greater risk of pathology than winners and those of higher status. In this theory concepts of defeat and entrapment are seen to be of special relevance to the study of depression. We outline the role of defeat and entrapment within the social rank theory of depression.

METHODS

New self-report measures of entrapment and defeat were developed and used to test predictions of the social rank theory of depression. Both a sample of students and depressed patients were assessed with these new scales and other social rank measures (e.g. social comparison and submissive behaviour).

RESULTS

The entrapment and defeat measures were found to have good psychometric properties and significantly correlated with depression. They were also strongly associated with other rank variables. Defeat maintained a strong association with depression even after controlling for hopelessness (r = 0.62), whereas the relationship between hopelessness and depression was substantially reduced when controlling for defeat. Entrapment and defeat added substantially to the explained variance of depression after controlling for the other social rank variables.

CONCLUSIONS

Defeat and entrapment appear to be promising variables for the study of depression. These variables may also help to develop linkages between human and animal models of psychopathology.

Realizing specialist and advanced nursing practice: a typology of innovative nursing roles

This paper outlines the findings of the first phase of a Department of Health funded project: Realizing Specialist and Advanced Nursing Practice establishing the parameters of and identifying competencies for 'Nurse Practitioner' roles and evaluating programmes of preparation. An extensive literature review and interviews with 49 key informants was used to revise a typology of Domains of Innovative Nursing Roles which the authors had constructed. It also emerged from the key informant interviews that a substantial number of respondents considered the role of the Nurse Practitioner (NP) to be a composite of both specialist and advanced practice. Further analysis indicated that although current preparation for a 'specialist' role would meet many of the outcomes perceived necessary to prepare individuals for the NP role, something 'extra' was seen as a prerequisite for the NP. It is suggested, therefore, that there is a strong case for considering the NP role in terms of 'specialist plus', and that the typology can be helpful in considering the major emphasis within NP roles.

Submissive behaviour and psychopathology

OBJECTIVES

A variety of behaviours have been identified as submissive (Buss & Craik, 1986). These are believed to be associated with vulnerability to psychopathology. This paper explores the construct and measurement of submissive behaviours and their association with psychopathology.

DESIGN

Two self-report scales were designed to measure the frequencies of (a) typical submissive behaviours (SBS) and (b) passive/withdrawal and affiliative strategies focused on conflict de-escalation (CDS). The association of these scales with psychopathology was explored in a series of questionnaire studies.

METHODS

Study 1 assessed the SBS using a student sample (N = 332) and a mixed clinical group (N = 136). Of these, 177 students and 66 patients also completed the SCL-90-R. In Studies 2 and 3, the CDS and its association with depressive symptoms were assessed using a student sample (N = 154) and a depressed patient group (N = 60).

RESULTS

The SBS and CDS appeared reliable. There was a positive relationship between the SBS and the SCL-90-R, including interpersonal sensitivity and unexpressed hostility. The passive/withdrawal subscale of the CDS was associated with depressive symptoms. Evidence was obtained for sex differences with the affiliative subscale.

CONCLUSIONS

Some forms of submissive behaviour, especially those associated with passive/withdrawal and inhibition, are associated with a wide range of psychological problems.

In-vitro studies of the activity of glycopeptide combinations against Enterococcus faecalis biofilms

Perfused biofilms of Enterococcus faecalis reached a pseudo-steady state, with respect to bioburden and the numbers of cells liberated within the perfusates. Biofilm growth rate was slow (approximately 0.006 doublings/h) relative to batch culture (approximately 0.01 doublings/h). MICs were determined for vancomycin (0.12 mg/L) and teicoplanin (1.2 mg/L) in batch culture. Steady-state biofilms (24 h and 48 h) were perfused continuously for 96 h with medium containing antibiotic at 4 X MIC. Susceptibility was assessed as cfu in the perfusate, indicating growth inhibition, and as cfu for the parent biofilm. Vancomycin at these levels had little or no effect on either parameter, whilst teicoplanin produced a temporary (30 h) reduction in growth rate (99.99% for 24 h biofilms, 50% for 48 h biofilms). Antibiotic concentrations were raised to therapeutic (trough) levels (vancomycin, 5 mg/L; teicoplanin, 12 mg/L) and applied continuously to 24 h old biofilms. Neither agent affected viability of the biofilm over 96 h. Biofilm growth rate, however, was decreased markedly over the first 8-10 h of antibiotic treatment and was maintained at the reduced level for approximately 40 h. Thereafter growth of the biofilms gradually returned to pre-exposure levels. The pattern of recovery was different for the two agents suggesting that different mechanisms might be involved. Accordingly biofilms were exposed to successive and concurrent 24 h treatments with vancomycin (5 mg/L) and teicoplanin (12 mg/L). This led not only to a further 2-3 log reduction in the growth rate but also to a 3 log reduction in the viability of the parent biofilm. Such synergy between the glycopeptide agents might have therapeutic implications for the treatment of E. faecalis infection.

The development of a small-scale biofilm model suitable for studying the effects of antibiotics on biofilms of gram-negative bacteria

A method for the study of membrane-associated biofilm populations of Escherichia coli ATCC 8739 using modified Swinnex filter units was developed. Biofilms were established under carbon limitation in a chemically defined simple salts medium. Cells, pressure filtered on to cellulose nitrate membranes in situ, were perfused from the sterile side. Steady-state conditions were attained at which the growth rate of the sessile cells could be demonstrated to be proportional to the flow rate of medium. The antibiotic susceptibility of these biofilms was examined by including ciprofloxacin within the perfusing medium. Susceptibility of the biofilms to ciprofloxacin was found to be affected not only by its concentration, but also by the growth rate of the bacteria.

The evolution of social attractiveness and its role in shame, humiliation, guilt and therapy

This paper suggests that humans have innate needs to be seen as attractive to others. These needs form the basis for shame and mediate evaluations of social standing (status), social acceptance and social bonds. Shame and humiliation are associated with attacks on, and losses of, social attractiveness. The internal experiences of shame are derived from submissive strategies where one seeks to signal to others awareness of loss of social standing and limit possible damage. However, it is suggested that shame and humiliation differ from each other in a number of ways. For example, in shame the focus is on the self, while in humiliation the focus is on the harm done by others. Variations in the defensive strategies of shame and humiliation (e.g. avoidance, escape versus aggression and revenge) can pose particularly difficult problems in therapy. A focus on the role of social attractiveness in shame also allows for important distinctions to be drawn between shame and guilt.