The effect of single and multiple infections on atopy and wheezing in children.

BACKGROUND: The current epidemic of asthma and atopy has been explained by alterations in immune responses related to reduction in childhood infections. However, the findings of epidemiologic studies investigating the association between infection with atopy and asthma have been inconsistent. OBJECTIVE: We sought to investigate the effect of single or multiple infections (pathogen burden) on atopy and wheeze in urban children from Latin America. METHODS: Specific IgE against aeroallergens (sIgE) and skin prick test (SPT) reactivity for the most common local allergens were measured in 1128 children aged 4 to 11 years. Data on wheezing and potential confounders were collected by questionnaire. Infections by 8 pathogens were assessed by using serology and stool examination. Associations of wheeze and atopic outcomes with single and multiple infections were analyzed by means of logistic regression. RESULTS: Negative results for Toxoplasma gondii were associated with a higher prevalence of sIgE (≥0.70 kU/L), whereas negative results for Ascaris lumbricoides, T gondii, herpes simplex virus, and EBV were associated with a higher prevalence of SPT reactivity. Children with 3 or fewer infection markers had a higher prevalence of sIgE and SPT reactivity compared with those with 4 or more infection markers. However, isolated infections or pathogen burden were not associated with the prevalence of atopic or nonatopic wheeze. CONCLUSION: The findings provide support for the idea that the hygiene hypothesis is operating in an urban Latin American context, but its expression is thus far restricted to the atopic status of patients and not the perceived asthma symptoms.

Nosocomial pneumonia in the intensive care unit of a Brazilian university hospital: an analysis of the time span from admission to disease onset.

BACKGROUND: In addition to controversies as to the definition of nosocomial pneumonia (NP) because of the lack of a widely accepted diagnostic standard, there has been no agreement concerning the time span from hospital admission to disease onset. This study aims at both estimating the time span, in hours, from admission to the occurrence of suspected NP and investigating risk factors that might influence this time span. METHODS: This is a cohort study, and subjects were patients with nosocomial infection acquired in the intensive care unit of Edgard Santos University Hospital (HUPES/ICU) in Salvador, Brazil, from January 1995 to December 1997. Patients were observed from admission to 48 hours after discharge from the intensive care unit. The time span from admission to occurrence of suspected NP, the reason for admission, patient's origin, history of surgery, general anesthesia, mechanical ventilation, and use of antibiotic were analyzed and given a multivariate analysis using Cox regression model. RESULTS: Among 246 patients with nosocomial infection, 198 (80.5%) were suspected cases of NP, whereas 48 patients (19.5%) were not classified as such. The mean time, in hours, for the NP-free time span was 85.1 +/- 3.5 hours, and the median time was 72 hours when estimated by Kaplan-Meier method. Patients admitted from surgical heart procedures who had been given general anesthesia, mechanical ventilation, and antibiotics showed statistically significant shorter mean time spans from admission to NP occurrence when compared with the other patients. Age >or=50 years, use of mechanical ventilation, and use of antibiotics were associated with NP. CONCLUSIONS: Our finding for the estimated mean NP-free time span at the HUPES/ICU is somewhat in accordance with the literature (48 to 72 hours). Patients at HUPES/ICU might be considered as showing early NP, because they were diagnosed before the 5th day after admission. Preventive measures to NP should be reviewed and intensified at the HUPES/ICU, especially as related to mechanical ventilation.

Effects of helminth co-infections on atopy, asthma and cytokine production in children living in a poor urban area in Latin America.

BACKGROUND: Helminths are modulators of the host immune system, and infections with these parasites have been associated with protection against allergies and autoimmune diseases. The human host is often infected with multiple helminth parasites and most studies to date have investigated the effects of helminths in the context of infections with single parasite or types of parasites (e.g. geohelminths). In this study, we investigated how co-infections with three nematodes affect markers of allergic inflammation and asthma in children. We selected Ascaris lumbricoides and Trichuris trichiura, two parasites that inhabit the human intestine and Toxocara spp (Toxocara canis and/or T. cati), intestinal roundworms of dogs and cats that cause systemic larval infection in humans. These parasites were selected as the most prevalent helminth parasites in our study population. RESULTS: 36.4% of children were infected with one parasite; 12.7% with 2 and 5.2% with 3. Eosinophilia>4% and >10% was present in 74.3% and 25.5% of the children, respectively. Total IgE>200 IU/mL, sIgE≥0.70 kU/L and SPT positivity were present in 59.7%, 37.1% and 30% of the children, respectively. 22.7% had recent asthma (12.0% non-atopic and 10.7% atopic). Helminth infections were associated in a dose-dependent way to decrease in the prevalence of SPT and increase in eosinophilia, total IgE, and the production of the regulatory cytokine IL-10 by unstimulated peripheral blood leukocytes. No association with asthma was observed. CONCLUSIONS: Helminth co-infections in this population were associated with increased markers of the Th2 immune response, and with a host immune regulatory phenotype that may suppress allergic effector responses such as immediate hypersensitivity reactions in the skin.