Investigation of the interaction force between Cryptosporidium parvum oocysts and solid surfaces.

Interaction force profiles between single Cryptosporidium parvum oocysts and positively charged, silane-coated silica particles were measured in aqueous solutions using an atomic force microscope. The oocysts were immobilized for the measurements by entrapment in Millipore polycarbonate membranes with 3 microm pore size. Experiments were performed in both NaCl and CaCl2 solutions at ionic strengths ranging from 1 to 100 mM. For both electrolytes, the decay length of the repulsive force profile was found to be nearly independent of the ionic strength and always much larger than the theoretical Debye length of the system. In addition, the magnitude of the force was found to be essentially the same for both electrolytes, suggesting that the long-range repulsive forces are primarily steric in nature. These results support the theory that the interaction force between oocysts and surfaces is controlled by an outer, weakly charged or uncharged carbohydrate layer. Measurements were also performed with oocysts that had been deactivated using either chemical (formalin) or heat treatment. The force profiles obtained with formalin-treated oocysts appear to be essentially the same as for the untreated oocysts, whereas the profiles measured with the heat-treated oocysts show a much stronger dependence on solution ionic strength. With either the heat-treated or formalin-treated oocysts, adhesion was observed much more frequently than with untreated oocysts, which is consistent with the increased deposition rate observed with treated oocysts by Kuznar and Elimelech (Kuznar, Z. A.; Elimelech, M. Langmuir 2005, 21, 710-716). These results also suggest that treated oocysts, especially ones that have been inactivated by heating, may not be good surrogates for viable oocysts in laboratory studies.

Interaction force profiles between Cryptosporidium parvum oocysts and silica surfaces.

The interaction force profile between single Cryptosporidium parvum oocysts and silica particles was measured in aqueous solutions using an atomic force microscope. The oocysts were immobilized during the measurements by entrapment in Millipore polycarbonate membranes with a 3 microm pore size. Experiments were performed in both NaCl and CaCl2 solutions at ionic strengths ranging from 1 to 100 mM. For both electrolytes the decay length of the repulsive force profile, obtained via the slope of a plot of the logarithm of interaction force versus separation, was found to be essentially independent of the ionic strength and always much larger than the theoretical Debye length of the system. In addition, the magnitude of the force was found to be essentially the same for both electrolytes, suggesting that the long-range repulsive forces are primarily steric in nature. Fitting the force to an expression for the steric repulsive force between two grafted brush layers yields a layer thickness of approximately 115 nm. These results support the idea that the oocysts are covered by a relatively thick layer of uncharged (or weakly charged) carbohydrates, possibly mixed with a thinner layer of charged protein.

Access to and use of ambulatory health care by a vulnerable Mexican American population on the U.S.-Mexico border.

The objective of this study was to determine if health care access is equitable and effective for Mexican Americans at the U.S.-Mexico border. The design was a cross-sectional telephone and door-to-door survey using the Behavioral Risk Factor Surveillance System, and the subjects were 1,409 El Paso County residents, ages 18 to 64 years. After controlling for other predisposing, enabling, and need characteristics, the presence of health insurance was significantly associated with health care use in the past year, both for a checkup (odds ratio [OR] = 2.48; 95 percent confidence interval [CI] = 1.83, 3.38) and a visit for any reason (OR = 2.20; 95 percent CI = 1.60, 3.04). Findings were similar for a regular source of care. Those who reported a checkup in the past year were significantly more likely to receive clinical preventive services. The lack of health insurance and a regular source of care for Mexican Americans on the U.S.-Mexico border creates significant inequalities in access to care.

The ethical dimensions of cultural competence in border health care settings.

Through thematic stories of patient and provider interactions on the U.S.-Mexico border, this article challenges the commonly understood definition of culture. It explores areas of concern related to cultural competency and medical ethics. Stories outline issues related to communication and comprehension, use of interpreters, gender and sexual orientation, traditional health care practices, socioeconomic status, age, health care settings, and involvement of community representatives. Policy recommendations address language, continuity of care, and health care professions education.

Attitudes and beliefs about environmental hazards in three diverse communities in Texas on the border with Mexico.

OBJECTIVE: Since communicating risk related to environmental hazards has consistently presented a challenge to government agencies and industries, our objective was to better understand the attitudes and beliefs of three communities, so as to help agencies and industries develop better risk communication interventions. METHODS: We explored attitudes and beliefs about environmental risks in three diverse communities in Texas on the border with Mexico, in the county of El Paso. During the summer of 1995, using a door-to-door survey, we interviewed 147 individuals, using a questionnaire based upon an existing instrument. Interviews were conducted in three very different areas of the county: semirural low-income, urban low-income, and suburban upper-income. We randomly selected specific sections in each of the three communities for inclusion in the sample. We assessed attitudes and beliefs about regulations and experts, risk and hazards, and how to address environmental issues. RESULTS: Attitudes and beliefs varied among the three communities, especially in the assessment of riskiness of various hazards. In general, there was mistrust of government agencies and of industries, a strong feeling that the environment can be improved, and a lack of understanding about what actions individuals might take to improve the environment. DISCUSSION: Agencies need to find ways to increase their credibility with the public, and they should assess communities in order to understand the attitudes of the residents.

Acculturation and breast-feeding intention and practice in Hispanic women on the US-Mexico border.

OBJECTIVES: To explore the extent to which acculturation indicators predict both breast-feeding history and intentions among Mexican-American mothers having their first births, and among those having subsequent births. DESIGN: Cross-sectional survey in a hospital post-partum unit. METHODS: 3,036 Hispanic women were interviewed post-partum in their hospital room. A survey was administered in English or Spanish, and included questions about prenatal care, diet, work exposures, contraceptive use, and breast-feeding history and intentions. For the purposes of this study, acculturation was measured using a series of indicators including language spoken at home, language ability, country of birth, and country in which last schooling was received. RESULTS: Previous breast-feeding was significantly associated with educational attainment, speaking both English and Spanish at home, having had prenatal care during the previous pregnancy, and with both country variables (country of birth and country where finished school). Women with less education, women who were single, and women who did not receive any prenatal care were less likely to intend to breast-feed than were women with a college education, women with a partner, and women who received any prenatal care. Women born in Mexico (for multiparous women), or having finished school in Mexico (for primiparous women), were more likely to intend to breast-feed. CONCLUSIONS: Acculturation is associated with breast-feeding history and intention to breast-feed. Acculturation is a complex construct and traditional measures of acculturation based on language preference may not be as useful on the US-Mexico border. It is recommended that further study be conducted to determine what factors prevent women from breast-feeding, even though they intend to do so, especially in multi-cultural communities like those around the US-Mexico border.

Health care professionals' skills, beliefs, and expectations about screening for domestic violence in a border community.

This article describes domestic violence education of health professionals and determines association between screening behavior and preparedness, outcome expectations, and beliefs about how and when to screen. A survey was mailed to all primary care physicians, dentists, and nurse practitioners in El Paso, Texas (n = 561). Return rate was 34.4%. Using linear regression, differences (p < 0.05) were found between dentists and others in percentage of patients screened, education, preparedness, and beliefs. Education had a positive association (p < 0.001) with preparedness, beliefs about when to screen, and outcome expectations, and a negative association with beliefs about how to screen. Preparedness, beliefs, and realistic outcome expectations had a positive association (p < 0.02) with percentage of female patients screened. Education about domestic violence is important in increasing preparedness and influencing beliefs about when to screen and what outcomes can be expected. Educational programs should include not only information, but also skills training to increase perceptions of preparedness.

The validity of self-reported seatbelt use: Hispanic and non-Hispanic drivers in El Paso.

The validity of self-reported seatbelt use among low belt use populations has not been evaluated directly, despite the importance of such data for estimating the effectiveness of community-wide interventions and compliance with state laws. To address this gap in knowledge 612 drivers were recruited from convenience stores located in 12 randomly generated zip code areas located in El Paso, TX. Self-reported seatbelt use was compared with observed seatbelt use in a single sample of participants. Both data sets were collected almost contemporaneously and no participant was aware of having their seatbelt use observed. Hispanic (n = 388) and white/non-Hispanic (n = 126) drivers over reported seatbelt use by 27 and 21%, respectively. These findings suggest that response bias within low belt use populations may be greater than suggested by state and national data.

Developing a video intervention to model effective patient-physician communication and health-related decision-making skills for a multiethnic audience.

The ENDOW study is a multisite, community-based project designed to improve decision-making and patient-physician communication skills for midlife African-American, white, and Hispanic women facing decisions about hysterectomy. Based on results of initial focus groups, a patient education video was developed in English and Spanish to serve as the centerpiece of various interventions. The video uses community women to model appropriate decision-making and patient-physician communication skills. Women in the target populations rated the video as useful to very useful and would recommend it to others. The use of theory-driven approaches and pilot testing of draft products resulted in the production of a well-accepted, useful video suitable for diverse populations in intervention sites in several states.

Aberrantly low transferrin receptor expression on human monocytes is associated with nonpermissiveness for Legionella pneumophila growth.

Growth of Legionella pneumophila within human monocytes is iron dependent. A person with monocytes uniquely nonpermissive to L. pneumophila growth was identified whose monocytes expressed an abnormally low number of transferrin receptors in the nonactivated state, similar to the typically low level expressed in the interferon-gamma-activated state. The monocytes failed to up-regulate transferrin receptor expression appropriately in response to iron-transferrin. After treatment for chronic periodontal disease, the subject's monocytes converted to a permissive state. In contrast to the nonpermissive state, the permissive monocytes had normal transferrin receptor expression and up-regulated transferrin receptor expression appropriately in response to iron-transferrin. Thus, a nonpermissive state for L. pneumophila intracellular multiplication is associated with low levels of transferrin receptor expression in nonactivated monocytes and with an inability to up-regulate transferrin receptor expression in response to iron-transferrin. This nonpermissive state may be related to chronic inflammatory conditions such as periodontal disease.

Decision making, beliefs, and attitudes toward hysterectomy: a focus group study with medically underserved women in Texas.

Variations in hysterectomy rates have been associated with assorted physician and patient characteristics, and the disproportionate rate of hysterectomies in African American women has been attributed to a higher prevalence of leiomyomas. The role of women's beliefs and attitudes toward hysterectomy and participation in decision making for medical treatment has not been explored as a source of variance. The purposes of this qualitative study were to explore these constructs in a triethnic sample of women to understand beliefs, attitudes, and decision-making preferences among underserved women; to facilitate development of a quantitative survey; and to inform development of interventions to assist women with such medical decisions. Twenty-three focus groups were conducted with 148 women from community sites and public health clinics. Thirteen self-identified lesbians participated in three groups. Analysis of audiotaped transcripts yielded four main themes: perceived outcomes of hysterectomy, perceived views of men/partners, opinions about healthcare providers, decision-making process. Across groups, the women expressed similar expectations from hysterectomy, differing only in the degree to which dimensions were emphasized. The women thought men perceived women with hysterectomy as less desirable for reasons unrelated to childbearing. Attitudes toward physicians were negative except among Hispanic women. All women expressed a strong desire to be involved in elective treatment decisions and would discuss their choice with important others. Implications for intervention development include enhancing women's skills and confidence to evaluate treatment options and to interact with physicians around treatment choices and creation of portable educational components for important others.

The rapidly growing mycobacteria: saprophytes and parasites.

Rapidly growing mycobacteria are widespread saprophytes, but approximately one-third of identified species are also opportunistic pathogens in humans and animals, associated with skin, soft tissue, bone, and pulmonary infections as well as disseminated disease. Clinical and experimental evidence indicates a major role for the cell-mediated immune response in the pathogenesis of infection.

Preliminary characterization of a Mycobacterium abscessus mutant in human and murine models of infection.

The ability to persist in the host after the establishment of infection is an important virulence determinant for mycobacteria. Mycobacterium abscessus is a rapidly growing mycobacterial species which causes a variety of clinical syndromes in humans. We have obtained a rough, wild-type human clinical isolate of M. abscessus (M. abscessus-R) and a smooth, attenuated mutant (M. abscessus-S) which spontaneously dissociated from the clinical isolate. We have found that M. abscessus-R is able to persist and multiply in a murine pulmonary infection model in contrast to M. abscessus-S, which is rapidly cleared. To understand the basis for this difference, we characterized the behavior of these variants in human tissue culture models of infection. M. abscessus-R is able to persist and multiply in human monocytes, while M. abscessus-S is deficient in this ability. Both of these variants are phagocytized by human monocytes. M. abscessus-R resides in a phagosome typical for pathogenic mycobacteria with a tightly adherent phagosomal membrane. In contrast, M. abscessus-S resides in a "loose" phagosome with the phagosomal membrane separated from the bacterial cell wall. Both M. abscessus variants also have distinctive growth patterns in a recently described fibroblast-mycobacterium microcolony assay, with M. abscessus-R exhibiting growth characteristics similar to those previously reported for virulent M. tuberculosis and M. abscessus-S exhibiting growth characteristics similar to those previously reported for avirulent M. tuberculosis. In both the monocyte infection assay and the murine pulmonary infection model, numerous infected mononuclear phagocyte aggregates develop at sites of M. abscessus-R infection, but are absent with M. abscessus-S infection. We conclude that a mutation has occurred in the M. abscessus-S variant which has altered the ability of this organism to persist and multiply in host cells and that this may be related to the phenotypic changes we have observed in our tissue culture models of infection.

Seatbelt use and belief in destiny among Hispanic and non-Hispanic drivers.

In order to determine if fatalism is associated with seatbelt use, 312 drivers were recruited from convenience stores located within 12 randomly generated zip-code areas along the Texas-Mexico border. The seatbelt use of drivers was recorded unobtrusively; self-reported seatbelt use and belief in destiny (fatalism) were subsequently obtained by interview. The majority of respondents rejected a fatalistic orientation, although Hispanic drivers were significantly less likely to do so. Fatalism was not associated with observed seatbelt use. Our results suggest that ethnic differences in seatbelt use are not due to ethnic differences in fatalism. These findings have implications for developing health interventions in Hispanic and non-Hispanic communities.

Differential growth characteristics and streptomycin susceptibility of virulent and avirulent Mycobacterium tuberculosis strains in a novel fibroblast-mycobacterium microcolony assay.

The ability to spread from cell to cell may be an important virulence determinant of Mycobacterium tuberculosis. An in vitro assay was developed to characterize this ability among four strains of M. tuberculosis: the attenuated strain H37Ra, the virulent strains H37Rv and Erdman, and a virulent clinical isolate (Stew). Confluent monolayers of human skin fibroblasts were infected with these strains and overlaid with agar-medium. M. tuberculosis infection developed over 21 days as microcolonies originating within the plane of the fibroblasts. Microcolonies of the virulent strains had an elongated appearance and exhibited extensive cording. The cords appeared to invade adjacent cells within the plane of the monolayer. Microcolony diameter of the Erdman strain was significantly larger than that of the other virulent strains, indicating that virulent strains can have distinguishing phenotypes in this assay. In contrast, avirulent H37Ra microcolonies were rounded and noncorded. H37Ra microcolonies were significantly smaller than those of the virulent strains. Microcolony diameter of the virulent strains was not reduced by the extracellularly acting antibiotic streptomycin at concentrations of up to 5.0 microgram/ml. In contrast, H37Ra microcolony size was reduced at concentrations as low as 0.5 microgram/ml. Growth of all strains was similarly inhibited by 1.0 microgram of streptomycin per ml in fibroblast-conditioned tissue culture medium alone. When fibroblasts were infected with the M. tuberculosis strains without an agar overlay, with and without streptomycin, numbers of CFU mirrored the changes observed in the microcolony assay. There was a statistically significant decrease in H37Ra CFU compared to virulent strains after treatment with streptomycin. These differences between H37Ra and virulent strains in human fibroblasts suggest that H37Ra may be lacking a virulence determinant involved in cell-to-cell spread of M. tuberculosis.

Multinucleated giant cell formation induced by IFN-gamma/IL-3 is associated with restriction of virulent Mycobacterium tuberculosis cell to cell invasion in human monocyte monolayers.

One of the hallmarks of an effective immune response against Mycobacterium tuberculosis is the formation of granulomas containing multinucleated giant cells. IFN-gamma and interleukin-3 (IL-3) promote Langhans-type multinucleated giant cell formation and have been identified in T cell clones reacting to M. tuberculosis antigens. The ability of human monocytes treated with IFN-gamma and IL-3 to limit the spread of M. tuberculosis in an in vitro infection assay was examined. Monocytes were incubated with control medium, IFN-gamma, TNF-alpha, and calcitriol, a combination permissive to M. tuberculosis growth, or IFN-gamma and IL-3 and infected with a low inoculum of M. tuberculosis (Erdman). IFN-gamma/IL-3 treatment reduced M. tuberculosis CFU relative to both untreated and IFN-gamma/TNF-alpha/calcitriol-treated monocytes. Specifically, CFU were reduced by 79% at 14 days in the IFN-gamma/IL-3 treatment group relative to the IFN-gamma/TNF-alpha/calcitriol treatment group, an effect that was not due to toxic monocyte metabolites. M. tuberculosis growth restriction by IFN-gamma/IL-3-treated monocyte monolayers was associated with the development of Langhans-type multinucleated giant cells. At the light microscope level, dense growth of M. tuberculosis surrounded by a ring of nuclei localized to the center of individual cells. The intracellular location of M. tuberculosis was confirmed by electron microscopy. In contrast, monocyte monolayers treated with IFN-gamma/TNF-alpha/calcitriol consisted of a syncitium of cells containing monocyte aggregates. Nonlocalized linear arrays of M. tuberculosis were observed to be growing throughout such aggregates. These results suggest that physical sequestration of M. tuberculosis by Langhans-type multinucleated giant cells may limit cell to cell spread of this pathogen, thereby restricting growth.

Tumor necrosis factor alpha (TNFalpha) promotes growth of virulent Mycobacterium tuberculosis in human monocytes iron-mediated growth suppression is correlated with decreased release of TNFalpha from iron-treated infected monocytes.

The human immune response to Mycobacterium tuberculosis is not well characterized. To better understand the cellular immune response to tuberculosis, a human mononuclear phagocyte culture system using a low-infecting inoculum of M. tuberculosis to mimic in vivo conditions was developed. Using this system, monocytes treated with IFNgamma/TNFalpha/ calcitriol (CytD) were permissive for the growth of virulent M. tuberculosis. In the presence of iron, however, these monocytes suppressed the growth of M. tuberculosis. The enhanced permissiveness of CytD-preincubated monocytes was found to be due to TNFalpha, however, the ability of iron to suppress M. tuberculosis growth also required preincubation with TNFalpha. Iron-mediated growth suppression was correlated with selective suppression of TNFalpha release from infected monocytes. In addition, removal of TNFalpha from CytD-treated monocytes 2 d after infection mimicked the suppressive effect of iron, suggesting that iron may also be decreasing monocyte sensitivity to exogenously added TNFalpha. In the absence of iron, permissive, CytD-treated monocytes formed large infected cellular aggregates. With iron treatment, aggregation was suppressed, suggesting that the iron-suppressive effect on M. tuberculosis growth may be related to suppression of monocyte aggregation and diminished cell-to-cell spread of M. tuberculosis. The results of this study indicate that TNFalpha preincubation is required for human monocytes to exert an iron-mediated suppressive effect on M. tuberculosis growth. In the absence of iron, however, the continued presence of TNFalpha has a growth-promoting effect on M. tuberculosis in human monocytes. Iron may be an important early modulator of M. tuberculosis growth via its effects on TNFalpha.

Successful treatment of chronic severe neutropenia with weekly recombinant granulocyte-colony stimulating factor.

Daily treatment for symptomatic chronic neutropenia with recombinant granulocyte-colony stimulating factor (rhG-CSF) filgrastim is costly and sometimes causes neutrophillia. We report the use of weekly filgrastim in a 40-year-old man with life-long symptomatic neutropenia. Baseline neutrophil counts were < 1 x 10(9)/l 60% of the time, and fell below 0.5 x 10(9)/l for 7d periods every 22 d. Following 1 year of weekly filgrastim treatment, the absolute neutrophil count was maintained > 1 x 10(9)/l (averaging 2 x 10(9)/l) and the frequency and severity of symptoms were reduced by 85%. Therefore the benefits of filgrastim for the treatment of at least one form of chronic severe neutropenia can be derived from weekly rather than daily doses.

Initiation of prenatal care by low-income Hispanic women in Houston.

OBJECTIVE: To understand why many Hispanic women begin prenatal care in the later stages of pregnancy. METHODS: The authors compared the demographic profile, insurance status, and health beliefs--including the perceived benefits of and barriers to initiating prenatal care--of low-income Hispanic women who initiated prenatal care at different times during pregnancy or received no prenatal care. RESULTS: A perception of many barriers to care was associated with later initiation of care and non-use of care. Perceiving more benefits of care for the baby was associated with earlier initiation of care, as was having an eligibility card for hospital district services. Several barriers to care were mentioned by women on open-ended questioning, including long waiting times, embarrassment the physical examination, and lack of transportation. CONCLUSIONS: Recommendations for practice included decreasing the number of visits for women at low risk for poor pregnancy outcomes while increasing the time spent with the provider at each visit, decreasing the number of vaginal examinations for low risk women, increasing the use of midwives, training lay workers to do risk assessment, emphasizing specific messages about benefits to the baby, and increasing general health motivation to seek preventive care through community interventions.

Cutaneous miliary tuberculosis in the AIDS era: case report and review.

Tuberculosis with extrapulmonary manifestations is common in patients with AIDS. The skin is a site of dissemination that has often been overlooked. Historically, cutaneous miliary tuberculosis, also known as tuberculosis cutis miliaris disseminata, was noted to be a rare entity in adults; however, over the past 5 years, five cases of cutaneous miliary tuberculosis in human immunodeficiency virus (HIV)-seropositive individuals have been reported. We present the sixth such case and review the medical literature on cutaneous miliary tuberculosis in adults both before and during the AIDS era. The incidence of tuberculosis cutis miliaris disseminata in HIV-seropositive adults is likely higher than the incidence among the HIV-seronegative population that has been suggested in the historical literature. Its appearance can be quite nondescript; a high index of suspicion must be maintained, particularly for those patients with a CD4 cell count of < 200/mm3, to achieve the proper diagnosis and initiate appropriate therapy.