Yolanda López-Vidal

Protection of breast-fed infants against Campylobacter diarrhea by antibodies in human milk

To investigate the role of breast-feeding in preventing diarrhea caused by Campylobacter jejuni , we followed 98 Mexican children prospectively for 2 years beginning at their birth. Attack rates of diarrhea in children less than 6 months of age who were not fed human milk were 2.3 times greater than those in children of the same age who were fed human milk. Breast-fed children remained free of diarrhea for a longer time than non-breast-fed children ( p C. jejuni for non-breast-fed infants was significantly greater ( p C. jejuni were high in colostrum, decreased during the first month of breast-feeding, and generally persisted throughout lactation. Human milk consumed by children in whom Campylobacter diarrhea developed did not contain secretory IgA antibodies to the glycine acid-extractable common antigen of Campylobacter . This study shows an association between Campylobacter antibodies in human milk and prevention of diarrhea caused by Campylobacter .

DETECTION OF MYCOBACTERIAL ANTIGENS IN CEREBROSPINAL FLUID OF PATIENTS WITH TUBERCULOUS MENINGITIS BY ENZYME-LINKED IMMUNOSORBENT ASSAY

Culture and identification of Mycobacterium tuberculosis in cerebrospinal fluid (CSF) of patients with tuberculous meningitis is slow, and prognosis depends on early diagnosis and treatment. An enzyme-linked immunosorbent assay with commercial BCG and anti-BCG was designed to detect mycobacterial antigens in human body fluids. Absorbance at 405 nm was measured and readings greater than or equal to 0.20 were considered positive. The readings were above 0.20 for four patients with confirmed tuberculous meningitis and nine of twelve patients with probable tuberculous meningitis. In all but one of ten patients with meningitis of other causes and in eleven control subjects the readings were below 0.20. The specificity of the test was 95% and its sensitivity 81.25%.

Capsaicin consumption, Helicobacter pylori positivity and gastric cancer in Mexico

Gastric cancer (GC) incidence has not declined in Mexico. We assessed whether the intake of capsaicin (CAP), the pungent compound of chili peppers, increases the risk of GC independently of H. pylori positivity (Hp). From 1994 to 1996, a hospital‐based case‐control study was performed in 3 areas of Mexico; 234 cases of GC and 468 matched controls were enrolled and their diet and other characteristics were inquired. Chili pepper intake was queried by interview and CAP content of chilies was determined in a separate analysis by gas chromatography to estimate CAP intake; IGg Hp serum antibodies were determined by ELISA. The risk of GC was increased (OR = 1.71; 95% CI = 0.76–3.88) among high‐level consumers of CAP (90–250 mg of capsaicin per day, approximately 9–25 jalapeño peppers per day) as compared to low‐level consumers (0–29.9 mg of capsaicin per day, approximately 0 to less than 3 jalapeño peppers per day; p for trend p = 0.026); this effect was independent of Hp status and other potential GC determinants and was higher among diffuse GC cases (OR = 3.64; 95% CI = 1.09–12.2; p for trend = 0.002) compared to intestinal GC cases (OR = 1.36; 95% CI = 0.31–5.89; p for trend = 0.493). No significant interaction was found between CAP intake and Hp on GC risk. Chili pepper consumption might be an independent determinant of GC in Mexico.

Polymerase chain reaction for the detection of Mycobacterium tuberculosis DNA in tissue and assessment of its utility in the diagnosis of hepatic granulomas.

A polymerase chain reaction (PCR) assay for the rapid identification of Mycobacterium tuberculosis, based on amplification of the IS6110 insertion sequences, was tested in paraffin-embedded tissue from 64 biopsy samples with either positive or negative cultures for Mycobacterium tuberculosis. The utility of this PCR assay in the diagnosis of tuberculosis among patients with hepatic granulomas (HGs) was then tested by examining 43 liver biopsy samples. They were classified as either having definitive or probable tuberculosis or as being of nontuberculous origin, on the basis of clinical and microbiologic data and on their response to antituberculous treatment. PCR was 100% sensitive in the diagnosis of culture-positive M. tuberculosis infection in the lymph node, lung, and liver. The sensitivity of the PCR in the diagnosis of HG of definitive tuberculous origin was 58%, and the specificity was 96%. PCR is a valuable test for the demonstration of mycobacterial DNA in tissues. Although it is not highly sensitive, the DNA amplification method may also be more sensitive than culture in the diagnosis of M. tuberculosis-associated HG.

Oxidative Stress Caused by Ozone Exposure Induces Loss of Brain Repair in the Hippocampus of Adult Rats

Oxidative stress is involved in many neurodegenerative diseases. Chronic ozone exposure causes a secondary increase of reactive oxygen species, which cause an oxidative stress state in the organism. Ozone is one of the main components of photochemical pollution. Our purpose was to test that oxidative stress caused by chronic low doses of ozone, by itself, alters adult neurogenesis and causes progressive neurodegeneration in the hippocampus, which actions lead to the loss of brain plasticity in the mature central nervous system of rats. Animals were exposed to an ozone-free air stream and for 15, 30, 60, and 90 days to low doses of ozone to cause oxidative stress. Each group was then tested by (1) a spectrophotometer test to quantify lipid peroxidation (LPO) levels; (2) immunohistochemistry testing against doublecortin, Neu-N, p53, microglia, and glial fibrillary acidic protein; (3) Western blot tests for doublecortin and Neu-N; and (4) a one-trial passive avoidance test. Our results indicated that ozone causes an increase of LPO levels, morphological changes in the nucleus and the cytoplasm, and cell swelling in neurons. The Western blot shows a decrease for Neu-N and doublecortin. Activated and later phagocytic microglia and an increased number of astrocytes were found. There was a memory deficiency positively related to the amount of ozone exposure. These alterations suggest that oxidative stress caused by low doses of ozone causes dysregulation of inflammatory processes, progressive neurodegeneration, chronic loss of brain repair in the hippocampus, and brain plasticity changes in the rat analogous to those seen in Alzheimers disease.

Mycobacterium bovis BCG Substrains Confer Different Levels of Protection against Mycobacterium tuberculosis Infection in a BALB/c Model of Progressive Pulmonary Tuberculosis

ABSTRACT Mycobacterium bovis BCG is the only available vaccine against tuberculosis. Reasons for why diverse BCG substrains induce different levels of protection in clinical trials remain unclear. The aim of this study was to compare the effectiveness of 10 BCG substrains in a mouse model of pulmonary tuberculosis. BALB/c mice were subcutaneously vaccinated and 2 months later were challenged with Mycobacterium tuberculosis H37Rv by intratracheal injection. Two and 4 months after challenge, delayed-type hypersensitivity (DTH) response, lung tissue affected by pneumonia, CFU, T-cell counts, and cytokine expression (interleukin-2 [IL-2], IL-4, IL-10, and gamma interferon) were determined. A differential protective effect of the diverse BCG substrains was found. BCG Phipps led to the largest and most persistent reduction of CFU counts and of the area of pneumonia at 2 and 4 months after challenge. This protection was accompanied by reduced IL-10-producing T cells. Contemporary BCG substrains induce a wide range of protection in this animal model. These data can help in the selection of the best vaccine for human immunization and for the development of novel recombinant BCG-based vaccine.

Detection of genetic variation in Taenia solium

Genetic variability among Taenia solium isolates was studied in 160 cysticerci from 6 pigs, 4 from Mexico, 1 from Honduras, and 1 from Tanzania. Random amplified polymorphic DNA (RAPD) analysis performed with 4 commercial primers showed 88% polymorphic loci and an average heterozygosity of 0.077; however, several alleles were fixed within each isolate. Linkage disequilibrium analysis indicated that 3 of the 6 isolates had a random association of alleles, whereas the other 3 had a clonal structure. These results suggest the existence of local lineages in T. solium, with events of genetic recombination within them.

Asymptomatic Shigella infections in a cohort of Mexican children younger than two years of age.

The proportion of Shigella infections that occur asymptomatically in young children has not been established. A community-based cohort study of 367 infants was followed prospectively by weekly home visits from January, 1990, through December, 1991. Stool samples were collected weekly and when diarrhea occurred and were tested for Shigella and other enteropathogens. There were 2925 child months of observation and 65 episodes of Shigella infection. There were 3.1 episodes/100 child months during the warm season (May through September) and 0.97 episode/100 child months during the cold season. Shigella infections were rare during the first 6 months of life but increased with age (P < 0.0001). Overall 55% of detected infections were asymptomatic. The proportion of infections that were asymptomatic increased as age increased (P < 0.01). Symptom status was not significantly associated with Shigella species or season. All isolates from symptomatic and asymptomatic children had the 120- to 140-megadalton virulence plasmid. We conclude that infections with virulent strains of Shigella are commonly asymptomatic in Mexican children during the first 2 years of life.

Microbiological Implications of Periurban Agriculture and Water Reuse in Mexico City

Background Recycled treated or untreated wastewater represents an important health challenge in developing countries due to potential water related microbiological exposure. Our aim was to assess water quality and health implications in a Mexico City periurban agricultural area. Methodology/Principal Findings A longitudinal study in the Xochimilco wetland area was conducted, and 42 sites were randomly selected from 211, including irrigation water canals and effluents of treatment plants. Sample collection took place during rainy and dry seasons (2000–2001). Microbiological parameters (total coliforms, fecal coliforms, streptococci/enterococci, and bacteria other than Vibrio grown on TCBS), Helicobacter pylori, and physicochemical parameters including trihalomethanes (THM) were determined. Fecal coliforms and fecal streptococci are appropriate indicators of human or animal fecal contamination. Fecal coliform counts surpass Mexican and World Health Organization irrigation water guidelines. Identified microorganisms associated with various pathologies in humans and domestic animals comprise Escherichia coli, Klebsiella spp., Salmonella spp., Enterobacter spp., Enterococcus spp., and Pseudomonas spp; H. pylori was also present in the water. An environmental characteristic of the canal system showed high Total Organic Carbon content and relatively low dissolved oxygen concentration; residual chlorine as a disinfection control is not efficient, but THMs do not represent a problem. During the rainy season, temperature and conductivity were higher; in contrast, pH, dissolved oxygen, ammonia, and residual chlorine were lower. This is related with the continuous load of feces from human and animal sources, and to the aquatic systems, which vary seasonally and exhibit evidence of lower water quality in effluents from treatment plants. Conclusions/Significance There is a need for improvement of wastewater treatment systems, as well as more efficient monitoring, regulation, and enforcement procedures for wastewater disposal into bodies of water.

Longitudinal Study of Microbial Diversity and Seasonality in the Mexico City Metropolitan Area Water Supply System

ABSTRACT In the Mexico City metropolitan area (MCMA), 70% of the water for 18 million inhabitants is derived from the Basin of Mexico regional aquifer. To provide an overview of the quality of the groundwater, a longitudinal study was conducted, in which 30 sites were randomly selected from 1,575 registered extraction wells. Samples were taken before and after chlorine disinfection during both the rainy and dry seasons (2000-2001). Microbiological parameters (total coliforms, fecal coliforms, streptococci, and Vibrio spp.), the presence of Helicobacter pylori, and physicochemical parameters, including the amount of trihalomethanes (THMs), were determined. Although microorganisms and inorganic and organic compounds were evident, they did not exceed current permissible limits. Chlorine levels were low, and the bacterial counts were not affected by chlorine disinfection. Eighty-four bacterial species from nine genera normally associated with fecal contamination were identified in water samples. H. pylori was detected in at least 10% of the studied samples. About 40% of the samples surpassed the THM concentration allowed by Mexican and U.S. regulations, with levels of chloroform being high. The quality of the water distributed to the MCMA varied between the rainy and dry seasons, with higher levels of pH, nitrates, chloroform, bromodichloromethane, total organic carbon, and fecal streptococci during the dry season. This study showed that the groundwater distribution system is susceptible to contamination and that there is a need for a strict, year-round disinfection strategy to ensure adequate drinking-water quality. This situation in one of the worlds megacities may reflect what is happening in large urban centers in developing countries which rely on a groundwater supply.