Microbial characterization of biofilms in domestic drains and the establishment of stable biofilm microcosms

We have used heterotrophic plate counts, together with live-dead direct staining and denaturing gradient gel electrophoresis (DGGE), to characterize the eubacterial communities that had formed as biofilms within domestic sink drain outlets. Laboratory microcosms of these environments were established using excised biofilms from two separate drain biofilm samples to inoculate constant-depth film fermentors (CDFFs). Drain biofilms harbored 9.8 to 11.3 log(10) cells of viable enteric species and pseudomonads/g, while CDFF-grown biofilms harbored 10.6 to 11.4 log(10) cells/g. Since live-dead direct staining revealed various efficiencies of recovery by culture, samples were analyzed by DGGE, utilizing primers specific for the V2-V3 region of eubacterial 16S rDNA. These analyses showed that the major PCR amplicons from in situ material were represented in the microcosms and maintained there over extended periods. Sequencing of amplicons resolved by DGGE revealed that the biofilms were dominated by a small number of genera, which were also isolated by culture. One drain sample harbored the protozoan Colpoda maupasi, together with rhabtidid nematodes and bdelloid rotifers. The microcosm enables the maintenance of stable drain-type bacterial communities and represents a useful tool for the modeling of this ecosystem.

Association between virus-specific T-cell responses and plasma viral load in human immunodeficiency virus type 1 subtype C infection

Virus-specific T-cell immune responses are important in restraint of human immunodeficiency virus type 1 (HIV-1) replication and control of disease. Plasma viral load is a key determinant of disease progression and infectiousness in HIV infection. Although HIV-1 subtype C (HIV-1C) is the predominant virus in the AIDS epidemic worldwide, the relationship between HIV-1C-specific T-cell immune responses and plasma viral load has not been elucidated. In the present study we address (i) the association between the level of plasma viral load and virus-specific immune responses to different HIV-1C proteins and their subregions and (ii) the specifics of correlation between plasma viral load and T-cell responses within the major histocompatibility complex (MHC) class I HLA supertypes. Virus-specific immune responses in the natural course of HIV-1C infection were analyzed in the gamma interferon (IFN-gamma)-enzyme-linked immunospot assay by using synthetic overlapping peptides corresponding to the HIV-1C consensus sequence. For Gag p24, a correlation was seen between better T-cell responses and lower plasma viral load. For Nef, an opposite trend was observed where a higher T-cell response was more likely to be associated with a higher viral load. At the level of the HLA supertypes, a lower viral load was associated with higher T-cell responses to Gag p24 within the HLA A2, A24, B27, and B58 supertypes, in contrast to the absence of such a correlation within the HLA B44 supertype. The present study demonstrated differential correlations (or trends to correlation) in various HIV-1C proteins, suggesting (i) an important role of the HIV-1C Gag p24-specific immune responses in control of viremia and (ii) more rapid viral escape from immune responses to Nef with no restraint of plasma viral load. Correlations between the level of IFN-gamma-secreting T cells and viral load within the MHC class I HLA supertypes should be considered in HIV vaccine design and efficacy trials.

The physiology and collective recalcitrance of microbial biofilm communities

Microbial biofilms impinge upon all aspects of our lives. Whilst much of this impact is positive, there are many areas in which the presence and activities of biofilms are regarded as problematic and in need of control. It is in this respect that biofilms reveal their recalcitrance towards many of the long-established antibiotics, and industrial and medical treatment strategies. The nature of the resistance of biofilms, in spite of much research, remains an enigma. Whilst it is recognized that reaction--diffusion limitation properties of the biofilm matrix towards the majority of treatment agents will impede access, this cannot be the sole explanation of the observed resistance. Rather, it will delay the death of cells within the community to various extents. Similarly, it is recognized that biofilm communities are phenotypically heterogeneous and that their eradication will reflect the susceptibility of the most resistant phenotype. The nutrient and gaseous gradients that generate this heterogeneity will, however, be destroyed as a result of antimicrobial treatments and cause the phenotype of the survivors to alter from slow-growing resistant cells to fast-growing susceptible ones. Accordingly both explanations can only delay death of the community. In order to explain more fully the long-term recalcitrance of biofilms towards such a wide variety of biocidal agents, more radical hypotheses must be considered. Amongst these are that multidrug efflux pumps could be up-regulated on expression of a biofilm phenotype. Whilst this is an appealing and simple explanation, because of its ability to explain the breadth of agents to which biofilms are resistant, recent work has suggested that this is not the case. Alternative hypotheses attempt to explain the diversity of agents by invoking a common cause of death for which singular resistance mechanisms could be applied. It is therefore suggested that an altruistic majority of sublethally damaged cells in a population commit suicide (apoptosis), thereby providing some protection to the survivors. A proportion of cells (persisters) is suggested to be defective, or repressed, in their suicide response, and survive. The persisters thereby benefit from the self-sacrifice of their compatriots and maintain the gene pool. A second explanation of the presence of persisters is that the general stress response, well known to include the adoption of a viable, nonculturable state of quiescence, is up-regulated in small pockets of the biofilm community, where nutrients are particularly scarce. Such quiescent cells noted for their resistance towards the metabolically acting biocides would potentially have their dormancy broken after treatment by the replenished supply of nutrients caused by the death of the majority. A more recent hypothesis suggests that extracellular signals, 'alarmones', released from killed cells might prime recipients into a state of resistance. Thus, in biofilm communities deep lying cells might be alerted into a resistant state by the premature death of peripheral cells. It is equally possible that 'alarmones', in this context, are merely the post-treatment 'wake-up' call to a previously quiescent subset of cells. In this review, we attempt to provide a holistic view of the potential mechanisms by which biofilms express resistance. Since these mechanisms are multifaceted then their impact upon resistance will be considered against the context of biofilm formation, growth and maturation.

Possible implications of biocide accumulation in the environment on the prevalence of bacterial antibiotic resistance

The lethality of biocides depends upon their interaction with a number of distinct biochemical targets. This often reflects reactive chemistry for any given agent, such as thiol oxidation. Susceptibility may vary markedly between different target organisms, and changes within the more sensitive targets can alter the inhibitory effect. The multiplicity of potential targets, however, usually dictates against the development of overt resistance to concentrations used for hygienic applications. Similarly, although changes in cellular permeability toward such agents, mediated either by envelope modification or the induction of efflux-pumps may reduce susceptibility, they rarely influence the outcome of treatments at use-concentration. It has recently been proposed that chronic exposure of the environment to biocides used in a variety of commercial products might expose some microbial communities to subeffective concentrations causing emergence of resistant clones. Such resistance might relate to mutational changes in the most susceptible target or to regulatory mutants that cause the constitutive expression of certain efflux pumps. Although selection of organisms with such modifications is unlikely to influence the effectiveness of the biocides, changes in their susceptibility to third-party antibiotics can be postulated. This is particularly the case where a cellular target is shared between a biocide and an antibiotic, or where induction of efflux is sufficient to confer antibiotic resistance in the clinic. Although such linkage has been demonstrated in the laboratory in pure culture, it has not been documented in environments commonly exposed to biocides. In nature, the effects of chronic stressing with biocides are complicated by competition between microbial community members that may result in clonal expansion of naturally insusceptible clones.

Intrapatient diversity and its correlation with viral setpoint in human immunodeficiency virus type 1 CRF02_A/G-IbNG infection

The human immunodeficiency virus type 1 (HIV-1) viral setpoint during the disease-free interval has been strongly associated with future risk of disease progression. An awareness of the correlation between viral setpoint and HIV-1 genetic evolution over time is important in the understanding of viral dynamics and infection. We examined genetic diversity in HIV-1 CRF02_A/G-IbNG-infected seroincident women in Dakar, Senegal; determined whether a viral setpoint kinetic pattern existed for CRF02_A/G-IbNG during the disease-free interval; and correlated viral load level and diversity. Samples were drawn during the disease-free interval from consenting CRF02_A/G-IbNG-infected, antiretroviral therapy-naïve female commercial sex workers in Dakar, Senegal. Based on sequential plasma RNA values, low and high viral setpoint groups were established. Intrapatient diversity and divergence over time was determined from earlier and later time point DNA samples from each person. Most individuals followed the viral setpoint paradigm. For each 1/-/log(10) copy/ml of plasma increase in viral load, intrapatient diversity increased by 1.4% (P = 0.028). A greater diversification rate was observed in the high viral setpoint group than in the low viral setpoint group (P = 0.01). Greater nucleotide (P = 0.015) and amino acid (P = 0.048) divergences and a greater nucleotide divergence rate (P = 0.03) were found in the high viral setpoint group. There was no difference between the groups in the ratio of the number of nonsynonymous substitutions per nonsynonymous site to the number of synonymous substitutions per synonymous site. The greater intrapatient diversity, divergence, and diversification rates observed in the high viral setpoint group supports the notion that diversity is driven by cycles of viral replication resulting in accumulated mutations. Recognizing diversity potential based on viral load levels in individuals may inform the design of vaccines and therapies.

Magnitude and frequency of cytotoxic T-lymphocyte responses: identification of immunodominant regions of human immunodeficiency virus type 1 subtype C

A systematic analysis of immune responses on a population level is critical for a human immunodeficiency virus type 1 (HIV-1) vaccine design. Our studies in Botswana on (i) molecular analysis of the HIV-1 subtype C (HIV-1C) epidemic, (ii) frequencies of major histocompatibility complex class I HLA types, and (iii) cytotoxic T-lymphocyte (CTL) responses in the course of natural infection allowed us to address HIV-1C-specific immune responses on a population level. We analyzed the magnitude and frequency of the gamma interferon ELISPOT-based CTL responses and translated them into normalized cumulative CTL responses. The introduction of population-based cumulative CTL responses reflected both (i) essentials of the predominant virus circulating locally in Botswana and (ii) specificities of the genetic background of the Botswana population, and it allowed the identification of immunodominant regions across the entire HIV-1C. The most robust and vigorous immune responses were found within the HIV-1C proteins Gag p24, Vpr, Tat, and Nef. In addition, moderately strong responses were scattered across Gag p24, Pol reverse transcriptase and integrase, Vif, Tat, Env gp120 and gp41, and Nef. Assuming that at least some of the immune responses are protective, these identified immunodominant regions could be utilized in designing an HIV vaccine candidate for the population of southern Africa. Targeting multiple immunodominant regions should improve the overall vaccine immunogenicity in the local population and minimize viral escape from immune recognition. Furthermore, the analysis of HIV-1C-specific immune responses on a population level represents a comprehensive systematic approach in HIV vaccine design and should be considered for other HIV-1 subtypes and/or different geographic areas.

Relationship of anhedonia and anxiety to social rank, defeat and entrapment

There is good evidence to suggest that depression is highly correlated with perceptions of low rank and subordinate status (i.e. feeling inferior, low-self esteem, feeling that others look down on the self, and submissive behaviour). However, it is possible for people to feel inferior and anxious, and behave submissively but not necessarily be depressed. More recently two other processes, defeat and entrapment, have attracted attention as possible processes linked specifically to depression and anhedonia. This research explored the relationship of these variables (social rank variables and defeat and entrapment) to two measures of hedonic tone (low positive affectivity and anhedonia) and anxiety in both a clinical and student population. All variables were strongly associated with lowered hedonic tone and anxiety. However, partial correlations, and a structural equation model fitted to the data from combined groups, suggests that perceptions of defeat play a specifically important role in anhedonia as measured by low positive affect. Framed within an evolutionary model the data suggest that the mechanisms which evolved to help animals accommodate and respond to defeats may have important regulatory effects over positive affect, reducing exploration of and engagement with the environment.

Biofilms in vitro and in vivo: do singular mechanisms imply cross-resistance?

Microbial biofilm has become inexorably linked with man's failure to control them by antibiotic and biocide regimes that are effective against suspended bacteria. This failure relates to a localized concentration of biofilm bacteria, and their extracellular products (exopolymers and extracellular enzymes), that moderates the access of the treatment agent and starves the more deeply placed cells. Biofilms, therefore, typically present gradients of physiology and concentration for the imposed treatment agent, which enables the less susceptible clones to survive. Such clones might include efflux mutants in addition to genotypes with modifications in single gene products. Clonal expansion following subeffective treatment would, in the case of many antibiotics, lead to the emergence of a resistant population. This tends not to occur for biocidal treatments where the active agent exhibits multiple pharmacological activity towards a number of specific cellular targets. Whilst resistance development towards biocidal agents is highly unlikely, subeffective exposure will lead to the selection of less susceptible clones, modified either in efflux or in their most susceptible target. The latter might also confer resistance to antibiotics where the target is shared. Thus, recent reports have demonstrated that sublethal concentrations of the antibacterial and antifungal agent triclosan can select for resistant mutants in Escherichia coli and that this agent specifically targets the enzyme enoyl reductase that is involved in lipid biosynthesis. Triclosan may, therefore, select for mutants in a target that is shared with the anti-E. coli diazaborine compounds and the antituberculosis drug isoniazid. Although triclosan may be a uniquely specific biocide, sublethal concentrations of less specific antimicrobial agents may also select for mutations within their most sensitive targets, some of which might be common to therapeutic agents. Sublethal treatment with chemical antimicrobial agents has also been demonstrated to induce the expression of multidrug efflux pumps and efflux mutants. Whilst efflux does not confer protection against use concentrations of biocidal products it is sufficient to confer protection against therapeutic doses of many antibiotics. It has, therefore, been widely speculated that biocide misuse may have an insidious effect, contributing to the evolution and persistence of drug resistance within microbial communities. Whilst such notions are supported by laboratory studies that utilize pure cultures, recent evidence has strongly refuted such linkage within the general environment where complex, multispecies biofilms predominate and where biocidal products are routinely deployed. In such situations the competition, for nutrients and space, between community members of disparate sensitivities far outweighs any potential benefits bestowed by the changes in an individual's antimicrobial susceptibility.

Human immunodeficiency virus type 1 subtype C molecular phylogeny: consensus sequence for an AIDS vaccine design?

An evolving dominance of human immunodeficiency virus type 1 subtype C (HIV-1C) in the AIDS epidemic has been associated with a high prevalence of HIV-1C infection in the southern African countries and with an expanding epidemic in India and China. Understanding the molecular phylogeny and genetic diversity of HIV-1C viruses may be important for the design and evaluation of an HIV vaccine for ultimate use in the developing world. In this study we analyzed the phylogenetic relationships (i) between 73 non-recombinant HIV-1C near-full-length genome sequences, including 51 isolates from Botswana; (ii) between HIV-1C consensus sequences that represent different geographic subsets; and (iii) between specific isolates and consensus sequences. Based on the phylogenetic analyses of 73 near-full-length genomes, 16 "lineages" (a term that is used hereafter for discussion purposes and does not imply taxonomic standing) were identified within HIV-1C. The lineages were supported by high bootstrap values in maximum-parsimony and neighbor-joining analyses and were confirmed by the maximum-likelihood method. The nucleotide diversity between the 73 HIV-1C isolates (mean value of 8.93%; range, 2.9 to 11.7%) was significantly higher than the diversity of the samples to the consensus sequence (mean value of 4.86%; range, 3.3 to 7.2%, P < 0.0001). The translated amino acid distances to the consensus sequence were significantly lower than distances between samples within all HIV-1C proteins. The consensus sequences of HIV-1C proteins accompanied by amino acid frequencies were presented (that of Gag is presented in this work; those of Pol, Vif, Vpr, Tat, Rev, Vpu, Env, and Nef are presented elsewhere [http://www.aids.harvard.edu/lab_research/concensus_sequence.htm]). Additionally, in the promoter region three NF-kappa B sites (GGGRNNYYCC) were identified within the consensus sequences of the entire set or any subset of HIV-1C isolates. This study suggests that the consensus sequence approach could overcome the high genetic diversity of HIV-1C and facilitate an AIDS vaccine design, particularly if the assumption that an HIV-1C antigen with a more extensive match to the circulating viruses is likely to be more efficacious is proven in efficacy trials.

Evolution and social anxiety. The role of attraction, social competition, and social hierarchies

If human social anxiety is not predominately about the fear of physical injury or attack, as it is in other animals, then, to understand human social anxiety (i.e., fear of evaluation), it is necessary to consider why certain types of relationships are so important. Why do humans need to court the good feelings of others and fear not doing so? And why, when people wish to appear attractive to others (e.g., to make friends, date a desired sexual partner, or give a good presentation), do some people become so overwhelmed with anxiety that they behave submissively and fearfully (which can be seen as unattractive) or are avoidant? This article has suggested that humans have evolved to compete for attractiveness to make good impressions because these are related to eliciting important social resources and investments from others. These, in turn, have been linked to inclusive fitness and have physiological regulating effects. Being allocated a low social rank or ostracized carries many negative consequences for controlling social resources and physiological regulation. Social anxiety, like shame, can be adaptive to the extent that it helps people to "stay on track" with what is socially acceptable and what is not and could result in social sanction and exclusion. However, dysfunctional social anxiety is the result of activation of basic defensive mechanisms (and modules for) for threat detection and response (e.g., inhibition, eye-gaze avoidance, flight, or submission) that can be recruited rapidly for dealing with immediate threats, override conscious wishes, and interfere with being seen as a "useful associate." Second, this article has suggested that socially anxious people are highly attuned to the competitive dynamics of trying to elicit approval and investment from others but that they perceive themselves to start from an inferior (i.e., low-rank) position and, because of this, activate submissive defensives when attempting to present themselves as confident, able, and attractive to others. These submissive defenses (which evolved to inhibit animals in low-rank positions from making claims on resources or up-rank bids) interfere with confident performance, leading to a failure cycle. While psychological therapies may target specific modules, cognitions, and behaviors (e.g., damage limitation behaviors, eyes gaze avoidance, theory of mind beliefs) that underpin social anxiety, drugs may work by having a more generalized effect on the threat-safety balance such that there is a different "weighting" given to various social threats and opportunities. If social anxiety (and disorders associated with it) are increasing in the modern age, one reason may be invigorated competition for social prestige, attractiveness, and resources.

Endothelium-derived endothelin-1 reduces cerebral artery sensitivity to nitric oxide by a protein kinase C-independent pathway

BACKGROUND AND PURPOSE

Nitric oxide (NO) reduces endothelin-1 (ET-1) production and blunts ET-1 dependent vasoconstriction. The direct effects of smooth muscle ET(A) receptor stimulation on NO-mediated relaxation are unknown. We hypothesized that endothelium-derived ET-1 regulates vascular tone by reducing smooth muscle sensitivity to NO, possibly through activation of protein kinase C (PKC).

METHODS

Rings of rabbit middle cerebral artery were mounted on microvessel myographs to measure isometric tension. Dose-response curves to acetylcholine (ACh) and sodium nitroprusside (SNP; an NO donor) were obtained with or without ET-1 receptor blockade. Experiments were performed in the presence of indomethacin (10 micromol/L). Results are expressed as mean+/-SEM.

RESULTS

In depolarized conditions (40 mmol/L KCl physiological solution), ACh-induced relaxation was entirely NO-dependent, as indicated by its suppression by N(omega)-nitro-L-arginine (P<0.05). Arterial sensitivity (pD(2)) to ACh (6.32+/-0.11, n=6) was increased (P<0.05) to 6.77+/-0.10 (n=6) by BQ123 (ET(A) receptor antagonist, 5 micromol/L) but not by BQ788 (ET(B) receptor antagonist, 5 micromol/L; 6.08+/-0.22, n=5). Consistent with this finding, blockade of ET(A) receptors increased (P<0.05) vascular sensitivity to SNP (6.95+/-0.10, n=8), whereas BQ788 had no influence on arterial sensitivity to SNP (6.17+/-0.07, n=7) compared with control (6.43+/-0.13, n=11). In denuded arteries, the sensitivity to SNP (7.10+/-0.08, n=8) was reduced by exogenous ET-1 (6.51+/-0.35, n=7, P<0.05). Chelerythrine, a PKC inhibitor, did not alter smooth muscle sensitivity to NO, whereas phorbol 12-myristate 13-acetate, a PKC activator, strongly increased it.

CONCLUSIONS

Blockade of ET(A) but not ET(B) receptors sensitizes vascular smooth muscle to exogenous and endothelium-derived NO. This suggests that ET-1 regulates smooth muscle sensitivity to NO by a PKC-independent pathway. This represents an alternative pathway by which NO and ET-1 interact to regulate vascular tone.

Identification of human immunodeficiency virus type 1 subtype C Gag-, Tat-, Rev-, and Nef-specific elispot-based cytotoxic T-lymphocyte responses for AIDS vaccine design

The most severe human immunodeficiency virus type 1 (HIV-1) epidemic is occurring in southern Africa. It is caused by HIV-1 subtype C (HIV-1C). In this study we present the identification and analysis of cumulative cytotoxic T-lymphocyte (CTL) responses in the southern African country of Botswana. CTLs were shown to be an important component of the immune response to control HIV-1 infection. The definition of optimal and dominant epitopes across the HIV-1C genome that are targeted by CTL is critical for vaccine design. The characteristics of the predominant virus that causes the HIV-1 epidemic in a certain geographic area and also the genetic background of the population, through the distribution of common HLA class I alleles, might impact dominant CTL responses in the vaccinee and in the general population. The enzyme-linked immunospot (Elispot) gamma interferon assay has recently been shown to be a reliable tool to map optimal CTL epitopes, correlating well with other methods, such as intracellular staining, tetramer staining, and the classical chromium release assay. Using Elispot with overlapping synthetic peptides across Gag, Tat, Rev, and Nef, we analyzed HIV-1C-specific CTL responses of HIV-1-infected blood donors. Profiles of cumulative Elispot-based CTL responses combined with diversity and sequence consensus data provide an additional characterization of immunodominant regions across the HIV-1C genome. Results of the study suggest that the construction of a poly-epitope subtype-specific HIV-1 vaccine that includes multiple copies of immunodominant CTL epitopes across the viral genome, derived from predominant HIV-1 viruses, might be a logical approach to the design of a vaccine against AIDS.

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.