Environmental benchmarks based on ecotoxicological assessment with planktonic species might not adequately protect benthic assemblages in lotic systems.

Freshwater ecosystems face widespread diffuse and point-source contamination. Species Sensitivity Distributions (SSDs) have been used as a tool to determine chemical concentration benchmarks that represent protective levels for most species in the environment. Here we used a SSD approach to assess on the adequacy of standard planktonic organisms to reflect the response of benthic communities, critically supporting the structure and function of lotic ecosystems. For the purpose, SSDs reflecting non-lethal responses of standard planktonic and selected benthic organisms were built based on EC50 values (collected in the literature or estimated following testing herein) regarding three model contaminants: potassium dichromate (PD), 3,5-dichlorophenol (DCP) and lead chloride (LC). The derived HC5 estimates were discriminatory between chemicals and the uncertainty associated with the estimate was remarkably low. The HC5 estimates with corresponding uncertainty were generally within the same order of magnitude for the three chemicals tested, with better discrimination between chemicals regarding their hazardous potential being achieved for benthic organisms: DCP was clearly less hazardous than PD, but LC tends to be as hazardous as PD and DCP (assuming the confidence interval ranges). Moreover, benthic communities were more sensitive to both DCP and PD, in this later case the HC5 being lower by more than one order of magnitude than that found for planktonic communities; for LC, confidence intervals overlapped, preventing a feasible assumption regarding differential sensitivity of the compared communities. Microphytobenthos was highlighted as the most sensitive group to the three tested chemicals in SSDs covering the benthic compartment, while SSDs with planktonic organisms did not consistently show trends in sensitivity ordering. Overall, our results suggest that protective benchmarks retrieved from SSDs built with the responses of standard planktonic organisms (which are the most commonly used for regulation purposes) do not adequately protect benthic communities.

Effects of oral soy phosphatidylcholine on phagocytosis, arachidonate concentrations, and killing by human polymorphonuclear leukocytes.

A dietary supplement of linoleic acid (LA) as soy phosphatidylcholine (PC) or as triglyceride on polymorphonuclear leukocyte (PMNL) functions, arachidonate (AA) concentrations, AA release, and leukotriene B4 (LTB4) generation was studied in normal adults. Study 1: Eight subjects were fed PC (27 g) or placebo for 3 d in a blinded crossover experiment with PMNL assays at baseline and 4, 7, and 14 d. Study 2: Subjects were fed equal quantities of LA as PC (18 g, n = 8), safflower (SF, n = 4), or soybean oil (SY, n = 4) with PMNL assays at baseline and 48 h. Study 1: PC increased PMNL phagocytosis and killing of Candida albicans twofold (P less than 0.001) and PMNL phospholipid AA content threefold (P less than 0.001); AA release after Candida albicans stimulation increased 5.3-fold, correlating with PMNL killing (r = 0.932) and phagocytosis (r = 0.872). Study 2: PC, but not SF or SY, produced changes similar to those of study 1. With PMNL exposure to calcium ionophore A23187 or N-formyl-methionyl-leucyl-phenylalanine, PC increased LTB4 generation. Phospholipid LA, in contrast to triglyceride LA, enhanced PMNL phospholipid AA, phagocytosis, and killing.

Potentiation of Clostridium botulinum toxin aminoglycoside antibiotics: clinical and laboratory observations.

A child with infant botulism became apneic and died while receiving ampicillin and gentamicin therapy. As aminoglycosides have been implicated in the induction and/or exacerbation of neuromuscular blockade, we used an animal model to test the hypothesis that aminoglycosides potentiate neuromuscular blockade of botulinum toxin. In the range of aminoglycoside doses utilized in these experiments, both gentamicin and tobramycin enhance neuromuscular impairment and death of botulinum toxin-exposed mice. These results support recently published clinical observations that aminoglycosides may potentiate neuromuscular weakness caused by botulinum toxin, and suggest that these antibiotics should be used with caution in suspected cases of infant botulism.

Cellulitis: treatment with cefoxitin compared with multiple antibiotic therapy.

Cefoxitin, a parenteral cephamycin beta-lactam antibiotic was prospectively evaluated as a single drug alternative in 31 children with cellulitis and the results of therapy were compared retrospectively with those from prevailing multiple antibiotic therapy for cellulitis in 56 children. Periorbital and lower extremity cellulitis accounted for more than 60% of the cases in both study groups. The most common bacterial agents included Haemophilus influenzae, Staphylococcus aureus, and group A beta-hemolytic Streptococcus. In as many as 50% of the cases, no etiologic agent could be found. In addition to blood cultures, cellulitis leading edge aspirate cultures were helpful in establishing the etiologic diagnosis. Of 52 patients sampled in the combined studies, 21% had positive aspirate cultures in the presence of negative blood cultures. The outcome and mean duration of hospital stay were similar in both groups. No severe adverse reactions were encountered. The mean number of antibiotics used in the retrospective study was three (range 1 to 7) whereas cefoxitin alone was used in the prospective study. All organisms isolated in the prospective study were susceptible to cefoxitin. Single antibiotic therapy with cefoxitin appears to be as safe and as effective in the treatment of cellulitis in children as multiple antibiotic therapy.

Comparative efficacies of aztreonam and chloramphenicol in children with typhoid fever.

We compared aztreonam with chloramphenicol in a randomized trial involving the treatment of 36 children with typhoid fever. Eighteen children were randomized to receive aztreonam, 150 mg/kg/day intravenously, and 18 to receive chloramphenicol, 100 mg/kg/day orally. On entry in the study the clinical characteristics of the two treatment groups were comparable. The duration of therapy was 14.9 +/- 3.6 days for the aztreonam group and 12.8 +/- 2.6 days for the chloramphenicol group. The mean duration of fever was 5.9 +/- 3.1 days and 4.05 +/- 2.1 days for aztreonam and chloramphenicol groups respectively (P greater than 0.05). Clinical cure was observed in all patients treated with aztreonam and in 17 of 18 children given chloramphenicol; one patient died in the latter group. There were no relapses in either group. We observed clinical adverse reactions during the treatment with aztreonam in 2 patients. All strains of Salmonella typhi were susceptible to aztreonam, 1 strain was resistant to chloramphenicol and 3 strains were resistant to ampicillin. Aztreonam appears to be a satisfactory alternative to chloramphenicol in cases of typhoid fever caused by resistant strains or when chloramphenicol is contraindicated.

Multiresistant extended-spectrum beta-lactamase-producing Klebsiella pneumoniae causing an outbreak of nosocomial bloodstream infection.

This article describes an outbreak of bloodstream infection due to clonal dissemination of multiresistant Klebsiella pneumoniae in a neonatal area, during August 1999, in Mexico City General Hospital. The intestinal tract was the likely reservoir, and intensification of Contact Precaution measures contained the outbreak.

Outbreak of nosocomial sepsis and pneumonia in a newborn intensive care unit by multiresistant extended-spectrum beta-lactamase-producing Klebsiella pneumoniae: high impact on mortality.

We describe a case-control study of a small outbreak of nosocomial sepsis and pneumonia with high mortality due to clonal dissemination of a multiresistant Klebsiella pneumoniae in the neonatal intensive care unit of a Mexican institution. Our study helped to change nosocomial infection control policy in this hospital.

Nutrition, infection, and immunocompetence.

The nutritional status of an individual has a profound effect on both host susceptibility to specific infectious diseases and on their outcome. Available data suggest that specific and aggregate nutritional deficiencies can alter a host's immune response and increase susceptibility to infection. From a nutritional point of view, the process of nutrient loss and redistribution has the potential for being exploited to the benefit of the infected malnourished host. The proposal to use nutritional support to bolster the host response to infection in severely ill malnourished patients gains support from the fact that this reiterative cycle of malnutrition and infection is the main cause of morbidity and mortality in children in underdeveloped countries.

State of immunization in the Americas.

Countries in the Americas have led the world in conquering infectious diseases preventable through vaccination. In 1971, the Western hemisphere achieved smallpox eradication. In 1991, the Americas were free of indigenous transmission of wild poliovirus. In 1998, overall regional vaccination coverage was 86% for diphtheria-pertussis-tetanus, 89% for oral poliovirus vaccine 3, 98% for bacille Calmette-Guérin vaccine, and 85% for measles. These figures confirm that most of the children in the Americas are protected against these diseases. The breakthroughs obtained in immunization have stimulated countries to promote new initiatives aimed at the control and eradication of other vaccine-preventable diseases and to introduce new vaccines into routine schedules. In the 21st century, vaccines will remain the most cost-effective means of preventing diseases and avoiding expensive treatment costs.

Human visceral leishmaniasis: analysis of the specificity of humoral immune response to polypeptides of Leishmania donovani chagasi.

Soluble antigens from Leishmania donovani chagasi were studied in terms of their ability to react with sera from human visceral leishmaniasis. Thirty-six polypeptides, with molecular weights ranging from 14,400 to 123,000 were demonstrated by Western blot analysis. An extensive cross-reactivity with sera from patients with cutaneous leishmaniasis and Chagas' disease also was observed. Two polypeptides (Mr 119,000 and 123,000) reacted with all the sera from visceral leishmaniasis patients. When they were electroeluted from gels and evaluated with respect to specificity to the L. donovani chagasi subspecies, these components were expressed in all strains of Leishmania tested, but not in those of Trypanosoma cruzi. These results indicated that these components are shared by Trypanosomatidae of genus Leishmania. The eluted polypeptides did not react with sera from patients with Chagas' disease, indicating the feasibility of using purified antigens to discriminate between the humoral immune responses in T. cruzi and Leishmania infections.

Hepatitis A in Latin America: a changing epidemiologic pattern.

In a multicenter study, hepatitis A virus (HAV) seroprevalence was surveyed in six countries in Latin America in which in 12,000 subjects were stratified for age. The highest rates of seroprevalence were recorded in the Dominican Republic (89.0%) and Mexico (81.0%), with lower rates in Brazil (64.7%), Chile (58.1%), Venezuela (55.7%), and Argentina (55.0%). The seroprevalence of HAV in children between 1 and 5 years of age was less than 50%, except in the Dominican Republic. In the 5-10-year-old age group, seroprevalence rates have also decreased compared with previous reports. This suggests that the epidemiology is shifting from high to intermediate endemicity, with the population susceptible to HAV infection shifting from children to adolescents and adults. Furthermore, data from Brazil, Argentina, and Mexico show that HAV seroprevalence is significantly lower in people living in medium and high socioeconomic conditions. This study suggests the need for appropriate vaccination programs to be implemented targeting children, adolescents, and adults, particularly in higher socioeconomic groups.

The in vitro effect of sulbactam on polymorphonuclear leukocyte function.

The effects of sulbactam on polymorphonuclear leukocyte (PMN) chemotaxis, respiratory burst, and microbicidal activity against Staphylococcus aureus were evaluated in vitro. PMNs from normal adult volunteers were incubated with 0.5, 2, 5, 10, and 20 micrograms/ml of sulbactam for 30 min each. At concentrations of 5 and 10 micrograms/ml, sulbactam was found to enhance PMN bactericidal activity. No inhibitory effects on PMN function were noted at the concentrations of sulbactam that were tested. In addition, the in vitro inhibitory effect of ampicillin on PMN chemiluminescence was partially abrogated by the presence of sulbactam. These findings suggest that the microbicidal phagocytic response of human PMNs against S. aureus may be improved in vitro using concentrations of sulbactam that may be readily achieved with therapeutic doses of sulbactam/ampicillin.

In vitro and in vivo effects of clindamycin on polymorphonuclear leukocyte function.

The effects of clindamycin on polymorphonuclear leukocytes (PMNLs) were evaluated in vitro and in vivo in an experimental model and in immunocompromised patients with and without infection. Chemotaxis, chemiluminescence, and bactericidal capacity were evaluated using PMNLs preincubated with clindamycin in different concentrations. In the three phases of the study, clindamycin at a concentration of 2 mg/L significantly increased PMNL function. In contrast, when higher concentrations were used, PMNL function was not modified and in some cases it was decreased. Our findings suggest that clindamycin, in concentrations of 2 mg/L, positively modifies PMNL function.

Klebsiella pneumoniae 35 and 36 kDa porins are common antigens in different serotypes and induce opsonizing antibodies.

BACKGROUND: Klebsiella pneumoniae is a major cause of neonatal sepsis and nosocomial infections in Mexico. Antibiotic therapy is the first choice for treatment but the increase in multiple resistance strains has forced scientists to look for alternative treatments, such as immunotherapy. In this work, we propose that porins could be a common antigen among four different capsular serotypes of Klebsiella pneumoniae for the production of immune sera with opsonizing capacity. METHODS: The 35 and 36 kDa porins from four different serotypes of the bacteria were isolated by the Nikaido method followed by purification in Sephacryl column chromatography. The 36 kDa of serotype K8 was further purified by electroelution. The 35 and 36 kDa porins were used to obtain rabbit polyclonal antibodies (PolyAb) to the four serotypes and the 36 kDa from K8 for the production of monoclonal antibodies (MoAb). Antigenic reactivity of PolyAb and MoAb were analyzed by ELISA and WB and their opsonizing capacity for human PMN was measured by chemiluminescence (CL) using capsulated and non-capsulated bacteria. RESULTS: Porins from the four strains showe electrophoretic homology and cross reaction by ELISA and WB. CL assays indicated that PolyAb opsonized heterologous strains and that MoAb perform this in the absence of capsule. CONCLUSIONS: K.pneumoniae 35 and 36 kDa porins are common antigens for the four serotypes studied and induce opsonizing antibodies.

Comparative analysis of plasmids from nosocomial Klebsiella pneumoniae strains isolated from two hospitals.

A total of 46 clinical isolates of Klebsiella pneumoniae were studied. Of these, 33 were from "Hospital Infantil de México" (HIM) and 13 from "Hospital General de México" (HGM). The susceptibility of these strains to five antibiotics, as well as the plasmid DNA profiles, were determined for each group. Antibiotic susceptibility profiles were very similar in strains from both hospitals; however, most of the strains analyzed exhibited heterogeneous plasmid DNA profiles. Results showed that strains isolated in the two hospitals did not differ regarding morphology, biochemical profiles, antibiotic susceptibility or plasmid populations, and these characteristics may not be used as markers to differentiate Klebsiella pneumoniae strains from different hospitals.

Mortality associated with systemic candidiasis in children.

The purpose of this study was to determine factors associated with an increased risk of mortality due to systemic Candida infections in children hospitalized at our tertiary care facility. A total of 71 cases of Candida bloodstream infections were identified over a 2-year period. The attack rate was 47 cases of candidemia per 10,000 discharges and the case fatality rate was 46.5%. Sixty-one cases occurred in infants under 2 years; 27 were newborns (38%). Using logistic regression analysis, we evaluated the independent effects of potential risk factors for death due to candidemia. Three factors were associated with the subsequent risk for death due to systemic candida infection: malnutrition (OR = 4.3; 95% CI 1.2-14.8), prior surgery (OR = 3.8; 95% CI 1.2-13.2), and the number of days between the first positive candida blood culture and the onset of antifungal treatment (OR = 1.12; 95% CI 1.06-1.25). Newborns showed an almost three times greater risk of death due to candidemia as compared to other age groups, but this association was only marginally significant (OR = 2.8; 95% CI 0.9-9.3). There was no difference in the rate of candidemia between the 2 years of the study; however, the observed mortality declined significantly from 65% in year one to 20% in year two (p = 0.02). The major finding of this study was to observe that for every day treatment was delayed the risk of death increased significantly. Thus, this study provides support for empirical antifungal therapy early in the course of suspected systemic candidiasis in order to improve survival among children.

Determination of serum aluminum, platelet aggregation and lipid peroxidation in hemodialyzed patients.

Aluminum (Al3+) overload is frequently associated with lipid peroxidation and neurological disorders. Aluminum accumulation is also reported to be related to renal impairment, anemia and other clinical complications in hemodialysis patients. The aim of the present study was to determine the degree of lipid peroxidation, platelet aggregation and serum aluminum in patients receiving regular hemodialytic treatment. The level of plasma lipid peroxidation was evaluated on the basis of thiobarbituric acid reactive substances (TBARS). Mean platelet peroxidation in patients undergoing hemodialysis was significantly higher than in normal controls (2.7 +/- 0.03 vs. 1.8 +/- 0.06 nmol/l, P<0.05). Platelet aggregation and serum aluminum levels were determined by a turbidimetric method and atomic absorption spectrophotometry, respectively. Serum aluminum was significantly higher in patients than in normal controls (44.5 +/- 29 vs. 10.8 +/- 2.5 microg/l, P<0.05). Human blood platelets were stimulated with collagen (2.2 microg/ml), adenosine diphosphate (6 microM) and epinephrine (6 microM) and showed reduced function with the three agonists utilized. No correlation between aluminum levels and platelet aggregation or between aluminum and peroxidation was observed in hemodialyzed patients.

Educational outcomes of an otitis media workshop for primary care providers in Latin America.

Otitis media is a prevalent condition that can be diagnosed and treated by primary care providers skilled in otoscopy. Previous analysis demonstrated that brief, intensive instruction at one site in rural Mexico improved the test scores of health care providers and changed long-term practices (Eavey R, et al. Otolaryngol Head Neck Surg 1993; 109:895-8). We wanted to confirm these test score findings at other sites. A didactic course on otitis media with a practical otoscopy workshop was conducted at six Mexican locations and in one Venezuelan city by an interdisciplinary group of physicians. The same coded test was given immediately before and after the course. The Wilcoxon test for significance of intrasubject performance before and after intervention was used as a nonparametric assessment. At all seven sites (n = 190 subjects), test scores demonstrated statistically significant improvement (range = p < 0.001 to p < 0.0001). We conclude that this educational method consistently improved short-term knowledge of otitis media and that further teaching efforts and a longer term practice-impact study are warranted.

An education model for otitis media care field-tested in Latin America.

The World Health Organization has designated the teaching of otitis media management skills a "priority" status. Effective treatment of ear disease requires that the physician be both informationally educated as well as physically trained to use otoscopy. Little is known about how well this education can be provided in a short time and in a foreign country. To more objectively assess teaching effect, results of an education session for rural Mexican pediatric primary-care providers who were given an intensive otitis media lecture and otoscopy skills workshop in 1990 were evaluated. To test immediate cognitive impact, an anonymous written examination was given both before and after the teaching session. Average test scores after the educational sessions improved 24% (p < 0.001) over baseline scores before the sessions. To evaluate long-term impact on clinical practice, a follow-up telephone survey 2 years later was conducted. The use of an otoscope to diagnose otitis media had increased from 40% to 93% of respondents. We conclude that pediatric primary-care providers in rural Mexico possess a baseline level of knowledge about otitis media that can be significantly enhanced with one educational session. Further, this teaching effort produces an impact on practice pattern that lasts at least 2 years.

Some hematimetric findings in human Giardia lamblia infection.

Up to now few reports about haematological alterations induced by Giardia lamblia infection have been described. Because there are questions on this matter still not answered, we carried out a study to evaluate some erythrometric and leucometric parameters in a sample that consisted of 55 patients exclusively infected with G. lamblia and of 55 sex and age matched parasite-free individuals. The haematological parameters evaluated were: mean corpuscular volume (MCV), hemoglobin concentration, and relative and absolute number of eosinophils and lymphocytes. No significant differences in the mean values of MCV, hemoglobin levels and absolute relative lymphocyte numbers between the two groups could be detected. When the giardiasis and control groups were separated by pediatric (0-18 years old) and adult (older than 18 years) classes, a very significant difference in both relative and absolute number of eosinophils in the adult class was observed. With respect of the pediatric class, no differences, either in relative and absolute number of eosinophils, could be observed. Our findings suggest that, during G. lamblia infection, some kind of parasite allergen(s) could be secreted and be responsible for the increasing of eosinophil counts in peripheral blood of adults.