Toxoplasma-IgM and IgG-avidity in single samples from areas with a high infection rate can determine the risk of mother-to-child transmission

Anti-Toxoplasma IgG-avidity was determined in 168 serum samples from IgG- and IgM-positive pregnant women at various times during pregnancy, in order to evaluate the predictive value for risk of mother-to-child transmission in a single sample, taking the limitations of conventional serology into account. The neonatal IgM was considered the serologic marker of transmission. Fluorometric tests for IgG, IgM (immunocapture) and IgG-avidity were performed. Fifty-one of the 128 pregnant women tested gave birth in the hospital and neonatal IgM was obtained. The results showed 32 (62.75%) pregnant women having high avidity, IgM indexes between 0.6 and 2.4, and no infected newborn. Nineteen (37.25%) had low or inconclusive avidity, IgM indexes between 0.6 and 11.9, and five infected newborns and one stillbirth. In two infected newborns and the stillbirth maternal IgM indexes were low and in one infected newborn the only maternal parameter that suggested fetal risk was IgG-avidity. In the present study, IgG-avidity performed in single samples from positive IgM pregnant women helped to determine the risk of transmission at any time during pregnancy, especially when the indexes of the two tests were analysed with respect to gestational age. This model may be less expensive in developing countries where there is a high prevalence of infection than the follow-up of susceptible mothers until childbirth with monthly serology, and it creates a new perspective for the diagnosis of congenital toxoplasmosis.

Biological implications of the phenotypic plasticity in the Schistosoma mansoni - Nectomys squamipes model

The water-rat Nectomys squamipes is mostly important non-human host in schistosomiasis mansoni transmission in Brazil, due to its susceptibility, high abundance and water-contact pattern. During experimental infection of N. squamipes with Schistosoma mansoni, adult worms show phenotypic plasticity. This finding led us to investigate whether biological behavior is also affected. This was assessed comparing the biological characteristics of four S. mansoni strains: BE (State of Belém do Pará), CE (State of Pernambuco), CMO (State of Rio Grande do Norte) and SJ (State of São Paulo) using laboratory-bred N. squamipes. The infection was monitored by determination of the pre-patent period, fecal egg output, egg viability, intestinal egg count and, infectivity rate. No biological modification was observed in these parameters. Overall results highlight that N. squamipes was susceptible to several S. mansoni strains, suggesting that it might contribute to the maintenance of schistosomiasis mansoni in Brazil.

EXPERIMENTAL INFECTION OF SWISS AND AKR/J MICE WITH Centrocestus formosanus (TREMATODA: HETEROPHYIDAE)

In order to better understand the biology of Centrocestus formosanus in a definitive host model, mice of Swiss and AKR/J strains were experimentally infected with 100 metacercariae of the parasite. Fourteen days post-infection, the rodents were killed and adult trematodes were recovered from the small intestine. The percentage of parasite recovery from AKR/J mice (11.4%) was significantly higher than that from Swiss mice (5.3%). Moreover, trematodes recovered from the AKR/J strain were more developed and had greater fecundity. Peculiarities concerning the mice’s immune system could explain the difference in susceptibility and in worm development seen in the present study. The data obtained confirm that mice are susceptible to infection with C. formosanus and indicate that the AKR/J strain provides a more favorable environment for parasite development.

BRAIN ABSCESS DUE TO Staphylococcus aureus OF CRYPTOGENIC SOURCE IN AN HIV-1 INFECTED PATIENT IN USE OF ANTIRETROVIRAL THERAPY

The spectrum of neurological complications associated with human immunodeficiency virus type 1 (HIV-1) infection is broad. The most frequent etiologies include primary diseases (caused by HIV itself) or secondary diseases (opportunistic infections or neoplasms). Despite these conditions, HIV-infected patients are susceptible to other infections observed in patients without HIV infection. Here we report a rare case of a brain abscess caused by Staphylococcus aureus in an HIV-infected patient. After drainage of the abscess and treatment with oxacilin, the patient had a favorable outcome. This case reinforces the importance of a timely neurosurgical procedure that supported adequate management of an unusual cause of expansive brain lesions in HIV-1 infected patients.

Frequency of the toxic shock syndrome toxin-1 gene in methicillin-susceptible and -resistant Staphylococcus aureus isolates from teaching hospitals in Shiraz, Iran

INTRODUCTION: Staphylococcus aureus produces a range of virulence factors such as toxic shock syndrome toxin-1. METHODS: In this cross-sectional study of 345 clinical S. aureus isolates, the presence of the tst gene was assessed by polymerase chain reaction (PCR). RESULTS: The study revealed 53/345 (15.4%) isolates were positive for the tst gene. The tst gene was present in 18.1% of methicillin-susceptible S. aureus (MSSA) isolates and 11.6% of methicillin-resistant S. aureus (MRSA) isolates (p = 0.136). CONCLUSIONS: These results reveal the remarkable risk of S. aureus infections in hospitals, regardless of methicillin-resistance status.

Determinants of mortality in oncology patients colonized or infected with Staphylococcus aureus

Oxacillin-resistant Staphylococcus aureus (ORSA) infection is an important cause of hospital morbidity and mortality. The objective of this study was to identify the main factors associated with death in patients colonized or infected with Staphylococcus aureus in a cancer center. A matched-pair case-control study enrolled all patients infected or colonized with ORSA (cases) admitted to the Hospital do Câncer in Rio de Janeiro from 01/01/1992 to 12/31/1994. A control was defined as a patient hospitalized during the same period as the case-patients and colonized or infected with oxacillin-susceptible Staphylococcus aureus (OSSA). The study enrolled 95 cases and 95 controls. Patient distribution was similar for the two groups (p > or = 0.05) with respect to gender, underlying diseases, hospital transfer, prior infection, age, temperature, heart and respiratory rates, neutrophil count, and duration of hospitalization. Univariate analysis of putative risk factors associated with mortality showed the following significant variables: admission to the intensive care unit (ICU), presence of bacteremia, use of central venous catheter (CVC), ORSA colonization or infection, pneumonia, use of urinary catheter, primary lung infection, prior use of antibiotics, mucositis, and absence of cutaneous abscesses. Multivariate analysis showed a strong association between mortality and the following independent variables: admission to ICU (OR [odds ratio]=7.2), presence of Staphylococcus bacteremia (OR=6.8), presence of CVC (OR=5.3), and isolation of ORSA (OR=2.7). The study suggests a higher virulence of ORSA in comparison to OSSA in cancer patients.

Analysis of the interacting components between larval Schistosoma mansoni and schistosome-susceptible and resistant Biomphalaria glabrata

Cell-free hemolymph (serum) and hemocytes from Schistosoma mansoni-susceptible (PR albino M-line) and resistant (10-R2) strains of Biomphalaria glabrata were compared by SDS-PAGE, immunoblotting and radioiodination. Whole serum of both snail strains is dominated by hemoglobin (Hb) (MW = 160 Kd). SDS-PAGE. of Hb-depleted serum indicated that the 10-R2 strain has dominant polypeptides in the 50 to 30 Kd range whereas PR albino snails have few low MW proteins. Antibodies raised to whole PR albino and 10-R2 serum, and the 160 Kd (Hb) band reacted similarly in immunoblot assays. Analysis of hemocytes revealed that 10-R2 snails have a surface-exposed protein at about 80 Kd which is not present on PR albino hemocytes. An examination of primary cultured sporocysts indicated the presence of four major surface proteins (40, 50, 55, 70 Kd) and two minor surface-exposed polypeptides (92, 170 Kd). Antibodies raised against live, intact sporocysts reacted almost exclusively with sporocyst-surface proteins when tested by immunoblotting.

Optimisation of antiretroviral therapy : pharmacokinetic and pharmacogenetic approaches

Les progrès de la thérapie antirétrovirale ont transformé l'infection par le VIH d'une condition inévitablement fatale à une maladie chronique. En dépit de ce succès, l'échec thérapeutique et la toxicité médicamenteuse restent fréquents. Une réponse inadéquate au traitement est clairement multifactorielle et une individualisation de la posologie des médicaments qui se baserait sur les facteurs démographiques et génétiques des patients et sur les taux sanguins totaux, libres et/ou cellulaires des médicaments pourrait améliorer à la fois l'efficacité et la tolérance de la thérapie, cette dernière étant certainement un enjeu majeur pour un traitement qui se prend à vie.L'objectif global de cette thèse était de mieux comprendre les facteurs pharmacocinétiques (PK) et pharmacogénétiques (PG) influençant l'exposition aux médicaments antirétroviraux (ARVs) nous offrant ainsi une base rationnelle pour l'optimisation du traitement antiviral et pour l'ajustement posologique des médicaments chez les patients VIH-positifs. Une thérapie antirétrovirale adaptée au patient est susceptible d'augmenter la probabilité d'efficacité et de tolérance à ce traitement, permettant ainsi une meilleure compliance à long terme, et réduisant le risque d'émergence de résistance et d'échec thérapeutique.A cet effet, des méthodes de quantification des concentrations plasmatiques totales, libres et cellulaires des ARVs ainsi que de certains de leurs métabolites ont été développées et validées en utilisant la chromatographie liquide coupée à la spectrométrie de masse en tandem. Ces méthodes ont été appliquées pour la surveillance des taux d'ARVs dans diverses populations de patients HIV-positifs. Une étude clinique a été initiée dans le cadre de l'étude VIH Suisse de cohorte mère-enfant afin de déterminer si la grossesse influence la cinétique des ARVs. Les concentrations totales et libres du lopînavir, de l'atazanavir et de la névirapine ont été déterminées chez les femmes enceintes suivies pendant leur grossesse, et celles-ci ont été trouvées non influencées de manière cliniquement significative par la grossesse. Un ajustement posologique de ces ARVs n'est donc pas nécessaire chez les femmes enceintes. Lors d'une petite étude chez des patients HIV- positifs expérimentés, la corrélation entre l'exposition cellulaire et plasmatique des nouveaux ARVs, notamment le raltégravir, a été déterminée. Une bonne corrélation a été obtenue entre taux plasmatiques et cellulaires de raltégravir, suggérant que la surveillance des taux totaux est un substitut satisfaisant. Cependant, une importante variabilité inter¬patient a été observée dans les ratios d'accumulation cellulaire du raltégravir, ce qui devrait encourager des investigations supplémentaires chez les patients en échec sous ce traitement. L'efficacité du suivi thérapeutique des médicaments (TDM) pour l'adaptation des taux d'efavirenz chez des patients avec des concentrations au-dessus de la cible thérapeutique recommandée a été évaluée lors d'une étude prospective. L'adaptation des doses d'efavirenz basée sur le TDM s'est montrée efficace et sûre, soutenant l'utilisation du TDM chez les patients avec concentrations hors cible thérapeutique. L'impact des polymorphismes génétiques des cytochromes P450 (CYP) 2B6, 2A6 et 3A4/5 sur la pharmacocinétique de l'efavirenz et de ces métabolites a été étudié : un modèle de PK de population intégrant les covariats génétiques et démographiques a été construit. Les variations génétiques fonctionnelles dans les voies de métabolisation principales (CYP2B6) et accessoires {CYP2A6et 3A4/S) de l'efavirenz ont un impact sur sa disposition, et peuvent mener à des expositions extrêmes au médicament. Un? ajustement des doses guidé par le TDM est donc recommandé chez ces patients, en accord avec les polymorphismes génétiques.Ainsi, nous avons démonté qu'en utilisant une approche globale tenant compte à la fois des facteurs PK et PG influençant l'exposition aux ARVs chez les patients infectés, il est possible, si nécessaire, d'individualiser la thérapie antirétrovirale dans des situations diverses. L'optimisation du traitement antirétroviral contribue vraisemblablement à une meilleure efficacité thérapeutique à iong terme tout en réduisant la survenue d'effets indésirables.Résumé grand publicOptimisation de la thérapie antirétrovirale: approches pharmacocinétiques et pharmacogénétiquesLes progrès effectués dans le traitement de l'infection par le virus de llmmunodéficienoe humaine acquise (VIH) ont permis de transformer une affection mortelle en une maladie chronique traitable avec des médicaments de plus en plus efficaces. Malgré ce succès, un certain nombre de patients ne répondent pas de façon optimale à leur traitement etyou souffrent d'effets indésirables médicamenteux entraînant de fréquentes modifications dans leur thérapie. Il a été possible de mettre en évidence que l'efficacité d'un traitement antirétroviral est dans la plupart des cas corrélée aux concentrations de médicaments mesurées dans le sang des patients. Cependant, le virus se réplique dans la cellule, et seule la fraction des médicaments non liée aux protéines du plasma sanguin peut entrer dans la cellule et exercer l'activité antirétrovirale au niveau cellulaire. Il existe par ailleurs une importante variabilité des concentrations sanguines de médicament chez des patients prenant pourtant la même dose de médicament. Cette variabilité peut être due à des facteurs démographiques et/ou génétiques susceptibles d'influencer la réponse au traitement antirétroviral.Cette thèse a eu pour objectif de mieux comprendre les facteurs pharmacologiques et génétiques influençant l'efficacité et ta toxicité des médicaments antirétroviraux, dans le but d'individualiser la thérapie antivirale et d'améliorer le suivi des patients HIV-positifs.A cet effet, des méthodes de dosage très sensibles ont été développées pour permettre la quantification des médicaments antirétroviraux dans le sang et les cellules. Ces méthodes analytiques ont été appliquées dans le cadre de diverses études cliniques réalisées avec des patients. Une des études cliniques a recherché s'il y avait un impact des changements physiologiques liés à la grossesse sur les concentrations des médicaments antirétroviraux. Nous avons ainsi pu démontrer que la grossesse n'influençait pas de façon cliniquement significative le devenir des médicaments antirétroviraux chez les femmes enceintes HIV- positives. La posologie de médicaments ne devrait donc pas être modifiée dans cette population de patientes. Par ailleurs, d'autres études ont portés sur les variations génétiques des patients influençant l'activité enzymatique des protéines impliquées dans le métabolisme des médicaments antirétroviraux. Nous avons également étudié l'utilité d'une surveillance des concentrations de médicament (suivi thérapeutique) dans le sang des patients pour l'individualisation des traitements antiviraux. Il a été possible de mettre en évidence des relations significatives entre l'exposition aux médicaments antirétroviraux et l'existence chez les patients de certaines variations génétiques. Nos analyses ont également permis d'étudier les relations entre les concentrations dans le sang des patients et les taux mesurés dans les cellules où le virus HIV se réplique. De plus, la mesure des taux sanguins de médicaments antirétroviraux et leur interprétation a permis d'ajuster la posologie de médicaments chez les patients de façon efficace et sûre.Ainsi, la complémentarité des connaissances pharmacologiques, génétiques et virales s'inscrit dans l'optique d'une stratégie globale de prise en charge du patient et vise à l'individualisation de la thérapie antirétrovirale en fonction des caractéristiques propres de chaque individu. Cette approche contribue ainsi à l'optimisation du traitement antirétroviral dans la perspective d'un succès du traitement à long terme tout en réduisant la probabilité des effets indésirables rencontrés. - The improvement in antirétroviral therapy has transformed HIV infection from an inevitably fatal condition to a chronic, manageable disease. However, treatment failure and drug toxicity are frequent. Inadequate response to treatment is clearly multifactorial and, therefore, dosage individualisation based on demographic factors, genetic markers and measurement of total, free and/or cellular drug level may increase both drug efficacy and tolerability. Drug tolerability is certainly a major issue for a treatment that must be taken indefinitely.The global objective of this thesis aimed at increasing our current understanding of pharmacokinetic (PK) and pharmacogenetic (PG) factors influencing the exposition to antirétroviral drugs (ARVs) in HIV-positive patients. In turn, this should provide us with a rational basis for antiviral treatment optimisation and drug dosage adjustment in HIV- positive patients. Patient's tailored antirétroviral regimen is likely to enhance treatment effectiveness and tolerability, enabling a better compliance over time, and hence reducing the probability of emergence of viral resistance and treatment failure.To that endeavour, analytical methods for the measurement of total plasma, free and cellular concentrations of ARVs and some of their metabolites have been developed and validated using liquid chromatography coupled with tandem mass spectrometry. These assays have been applied for the monitoring of ARVs levels in various populations of HIV- positive patients. A clinical study has been initiated within the frame of the Mother and Child Swiss HIV Cohort Study to determine whether pregnancy influences the exposition to ARVs. Free and total plasma concentrations of lopinavir, atazanavir and nevirapine have been determined in pregnant women followed during the course of pregnancy, and were found not influenced to a clinically significant extent by pregnancy. Dosage adjustment for these drugs is therefore not required in pregnant women. In a study in treatment- experienced HIV-positive patients, the correlation between cellular and total plasma exposure to new antirétroviral drugs, notably the HIV integrase inhibitor raltegravir, has been determined. A good correlation was obtained between total and cellular levels of raltegravir, suggesting that monitoring of total levels are a satisfactory. However, significant inter-patient variability was observed in raltegravir cell accumulation which should prompt further investigations in patients failing under an integrase inhibitor-based regimen. The effectiveness of therapeutic drug monitoring (TDM) to guide efavirenz dose reduction in patients having concentrations above the recommended therapeutic range was evaluated in a prospective study. TDM-guided dosage adjustment of efavirenz was found feasible and safe, supporting the use of TDM in patients with efavirenz concentrations above therapeutic target. The impact of genetic polymorphisms of cytochromes P450 (CYP) 2B6, 2A6 and 3A4/5 on the PK of efavirenz and its metabolites was studied: a population PK model was built integrating both genetic and demographic covariates. Functional genetic variations in main (CYP2B6) and accessory (2A6, 3A4/5) metabolic pathways of efavirenz have an impact on efavirenz disposition, and may lead to extreme drug exposures. Dosage adjustment guided by TDM is thus required in those patients, according to the pharmacogenetic polymorphism.Thus, we have demonstrated, using a comprehensive approach taking into account both PK and PG factors influencing ARVs exposure in HIV-infected patients, the feasibility of individualising antirétroviral therapy in various situations. Antiviral treatment optimisation is likely to increase long-term treatment success while reducing the occurrence of adverse drug reactions.

Methicillin-susceptible Staphylococcus aureus clonal complex 398: high prevalence and geographical heterogeneity in bone and joint infection and nasal carriage.

The prevalence of clonal complex (CC) 398 methicillin-susceptible Staphylococcus aureus (MSSA) was unexpectedly high among bone and joint infections (BJIs) and nasal-colonizing isolates in France, with surprising geographical heterogeneity. With none of the major, most-known staphylococcal virulence genes, MSSA CC398 BJI was associated with lower biological inflammatory syndrome and lower treatment failure rates.

Enhancement of Leishmania amazonensis infection in BCG non-responder mice by BCG-antigen specific vaccine

Different patterns of cutaneous leishmaniasis can be induced when a challenge of alike dose of Leishmania amazonensis amastigotes in various inbred strains was applied. Two strains of mice, the Balb/c and C57 BL/10J, showed exceptional suscepbility, and 10(elevado a sexta potência) amastigotes infective dose lead, to ulcerative progressive lesions with cutaneous metastasis and loss by necrosis of leg on wich the footpad primary lesion occured. Lesions were also progressive but in a lower degree when C3H/HeN and C57BL/6 were infected. Lesions progress slowly in DBA/2 mice presenting lesions wich reach a discreet peack after 12 weeks, do not heal but do not uncerate. DBA/2 mice is, therefore, a good model for immunomodualtion. In attempt to determine the influence of BCG in vaccination schedule using microsomal fraction, DBA/2 became an excellent model, since it is also a non-responder to BCG. Vaccination of DBA/2 mice, receiving the same 10(elevado a sexta potência) BCG viable dose and 10 *g or 50 *g of protein content of microsomal fraction, lead to a progressive disease with time course similar to those observed in susceptible non-vaccinated C57BL/10J mice after 6 months of observation. An enhancement of infection in BCG non-responder mice suggests that use of BCG as immunostimulant in humans could be critical for both vaccination and immunoprophylactic strategies.

Schizotrypanids: the occurence of dermatitis in immunodeficiency animals infected with Trypanosoma cruzi

Congenitally athymic nude Balb/c (nu/nu) and their phenothypically normal adult and neonate littermates (nu/+), the C3H/HeN as well, were intraperitoneally infected with two strains (Y or CL) of Trypanossoma cruzi. The nude mice and the neonates developed a severe parasitaemia, the susceptible C3H/HeN also presented high level and adult Balb/c mice presented parasitaemia similar to that observed in outbred mice. Erythematous skin lesions were observed initially in infected athymic nude and neonates, being charactherized by nests of amastigotes in the dermis; in C3H/HeN infected mice no nest of parasite was observed but a low-grade inflammatory reaction was seen. In adult Balb/c or OF1 outbred mice nest was found but discreet inflammatory reaction was observed in severe infections.

Efficacy of trovafloxacin in treatment of experimental staphylococcal or streptococcal endocarditis.

The efficacy of trovafloxacin against Staphylococcus aureus and viridans group streptococci was investigated in vitro and in an experimental model of endocarditis. The MICs at which trovafloxacin and ciprofloxacin inhibited 90% of clinical isolates of such bacteria (MIC90s) were (i) 0.03 and 2 mg/liter, respectively, for 30 ciprofloxacin-susceptible S. aureus isolates, (ii) 32 and 128 mg/liter, respectively, for 20 ciprofloxacin-resistant S. aureus isolates, and (iii) 0.25 and 8 mg/liter, respectively, for 28 viridans group streptococci. Rats with aortic vegetations were infected with either of two ciprofloxacin-susceptible but methicillin-resistant S. aureus strains (strains COL and P8), one penicillin-susceptible Streptococcus sanguis strain, or one penicillin-resistant Streptococcus mitis strain. Rats were treated for 3 or 5 days with doses that resulted in kinetics that simulated those achieved in humans with trovafloxacin (200 mg orally once a day), ciprofloxacin (750 mg orally twice a day), vancomycin (1 g intravenously twice a day), or ceftriaxone (2 g intravenously once a day). Against the staphylococci, the activities of both trovafloxacin and ciprofloxacin were equivalent to that of vancomycin, and treatment of endocarditis with these drugs was successful (P < 0.05). However, ciprofloxacin selected for resistant derivatives in vitro and in vivo, whereas trovafloxacin was 10 to 100 times less prone than ciprofloxacin to select for resistance in vitro and did not select for resistance in vivo. Against the two streptococcal isolates, trovafloxacin significantly (P < 0.05) decreased bacterial counts in the vegetations but was less effective than the control drug, ceftriaxone. Thus, a simulated oral dose of trovafloxacin (200 mg per day) was effective against ciprofloxacin-susceptible staphylococci and was less likely than ciprofloxacin to select for resistance. The simulated oral dose of trovafloxacin also had some activity against streptococcal endocarditis, but optimal treatment of infections caused by such organisms might require higher doses of the drug.

Unusual spread of a penicillin-susceptible methicillin-resistant Staphylococcus aureus clone in a geographic area of low incidence.

We describe the unusual spread of a penicillin-susceptible methicillin-resistant Staphylococcus aureus (MRSA) clone in hospitals in western Switzerland, where the incidence of MRSA is usually low. During a 2-year period, this clone had been responsible for several outbreaks and had been isolated from >156 persons in 21 institutions. Molecular typing by pulsed-field gel electrophoresis (PFGE) demonstrated that all of these isolates belonged to the same clone. In 1 of the outbreaks, involving 30 cases, the clone was responsible for at least 17 secondary cases. In contrast, during the period of the latter outbreak, 9 other patients harboring different MRSA strains, as assessed by PFGE, were hospitalized in the same wards, but no secondary cases occurred. These observations suggest that this clone, compared with other MRSA strains, had some intrinsic factor(s) that contributed to its ability to disseminate and could thus be considered epidemic.