Helicobacter pylori infection and the effect on growth in a cohort of children in the US/Mexico border

Helicobacter pylori (H. pylori) is an S-shaped or curved gram-negative bacterium that is mostly found in the human stomach. H. pylori causes gastritis in adults and children, which can lead to gastric ulcers or risk of cancer. Transmission of this bacterial infection remains to be unknown but is mostly acquired during childhood. Little is known about the effect H. pylori has on growth in children. Although some studies have reported that H. pylori is associated with subnormal growth, the association of H. pylori with growth retardation and malnutrition is poorly described. Data from this study comes from The Pasitos Cohort Study which draws its population from three border communities which include Socorro and San Elizario in Texas, as well as Ciudad Juarez, Chihuahua, Mexico. Birth documentation was obtained for 803 infants and 472 entered follow-up. This cohort study allowed us to assess the growth of children from 6 months to the seventh anniversary, and describe the prevalence of underweight, short stature and overweight in the study population. We also tested the hypothesis that children in the Pasitos Cohort Study who were ever infected with H. pylori show an increased risk of growth retardation or malnutrition at 66 months of age. Using the 2000 CDC Growth Reference, we found that the mean BMI of the study population increased as children grew older, while the mean of their height for age decreased slightly. The proportion of children who were classified as of short stature was under 5%, while those considered underweight were less than 10% at selected six-months of age intervals. Using the subset of children who were 66 months of age we found that the risk of underweight was higher among those who ever tested positive for H. pylori infection using the urea breath test; however, due to small numbers of children with 'wasting' this difference was not statistically significant. Moreover, since the six cases of under weight occurred among children of low socio-economic status we could not rule out potential confounding. The risk of developing short stature was not different among those ever infected and those who never tested positive for H. pylori infection. ^

A physiological role of cytochromes P450 4Fs: Mouse model

Cytochromes P450 4Fs (CYP4F) are a subfamily of enzymes involved in arachidonic acid metabolism with highest catalytic activity towards leukotriene B 4 (LTB4), a potent chemoattractant involved in prompting inflammation. CYP4F-mediated metabolism of LTB4 leads to inactive ω-hydroxy products incapable of initiating chemotaxis and the inflammatory stimuli that result in the influx of inflammatory cells. Our hypothesis is based on the catalytic ability of CYP4Fs to inactivate pro-inflammatory LTB4 which assures these enzymes a pivotal role in the process of inflammation resolution. ^ To test this hypothesis and evaluate the changes in CYP4F expression under complex inflammatory conditions, we designed two mouse models, one challenged with lipopolysaccharide (LPS) as a sterile model of sepsis and the other challenged with a systemic live bacterial infection of Citrobacter rodentium, an equivalent of the human enterobacterium E. coli pathogen invasion. Based on the evidence that Peroxisome Proliferator Activated Receptors (PPARs) play an active role in inflammation regulation, we also examined PPARs as a regulation mechanism in CYP4F expression during inflammation using PPARα knockout mice under LPS challenge. Using the Citrobacter rodentium model of inflammation, we studied CYP4F levels to compare them to those in LPS challenged animals. LPS-triggered inflammation signal is mediated by Toll-like 4 (TLR4) receptors which specifically respond to LPS in association with several other proteins. Using TLR4 knockout mice challenged with Citrobacter rodentium we addressed possible mediation of CYP4F expression regulation via these receptors. ^ Our results show isoform- and tissue-specific CYP4F expression in all the tissues examined. The Citrobacter rodentium inflammation model revealed significant reduction in liver expression of CYP4F14 and CYP4F15 and an up-regulation of gene expression of CYP4F16 and CYP4F18. TLR4 knockout studies showed that the decrease in hepatic CYP4F15 expression is TLR4-dependent. CYP4F expression in kidney shows down-regulation of CYP4F14 and CYP4F15 and up-regulation of CYP4F18 expression. In the LPS inflammation model, we showed similar patterns of CYP4F changes as in Citrobacter rodentium -infected mice. The renal profile of CYP4Fs in PPARα knockout mice with LPS challenge showed CYP4F15 down-regulation to be PPARα dependent. Our study confirmed tissue- and isoform-specific regulation of CYP4F isoforms in the course of inflammation. ^

Sickle cell disease: Its signs, symptoms and varied manifestations

Seventy-five sickle cell patients, age 3-36 years from Houston, Texas, participated in the research study to investigate sickle cell manifestations, conducted between November 1989 and August 1990. All the participants were blacks. There were 35 females and 39 males among the participants in this research study. One of the participants did not document the gender.^ The sickle cell history questionnaire was administered to the participants. Data collected from this study were statistically analyzed using frequencies, percentages, crosstabulations and chi-squares.^ Regular source of health care influences the time of diagnosis of sickle cell disease. Early diagnosis of sickle cell disease with proper care and management will reduce the morbidity and mortality rate of the disease.^ Fevers, bacterial infection, pneumoniae, anemiae, pains, ulcers and cardiovascular problems are common causes of hospitalizations. The average length of stay in the hospital on admission were higher among the sickle cell patients than their family members who themselves did not have sickle cell disease. ^

Incidence of enteric bacterial infections complicating Clostridium difficile infection (CDI)

The purpose of this study was to assess whether C. difficile infection (CDI) increases the risk of bacteremia or E. coli infection. The first specific aim of this study was to study the incidence of post C. difficile bacteremia in CDI patients stratified by disease severity vs. controls. The second specific aim was to study the incidence of post C. difficile E. coli infection from normally sterile sites stratified by disease severity vs. controls. This was a retrospective case case control study. The cases came from an ongoing prospective cohort study of CDI. Case group 1 were patients with mild to moderate CDI. Case group 2 were patients who had severe CDI. Controls were hospitalized patients given broad spectrum antibiotics that did not develop CDI. Controls were matched by age (±10 years) and duration of hospital visit (±1 week). 191 cases were selected from the cohort study and 191 controls were matched to the cases. Patients were followed up to 60 days after the initial diagnosis of CDI and assessed for bacteremia and E. coli infections. The Zar score was used to determine the severity of the CDI. Stata 11 was used to run all analyses. ^ The risk of non staphylococcal bacteremia after diagnosis of CDI was higher compared to controls (14% and 7% respectively, OR: 2.27; 95% CI:1.07-5.01, p=0.028). The risk of getting an E.coli infection was higher in cases than in controls (13% and 9% respectively although the results were not statistically significant (OR:1.4; 95% CI:0.38-5.59;p=0.32). Rates of non-staphylococcal bacteremia and E. coli infection did not differ cased on CDI severity. ^ This study showed that the risk of developing non-staphylococcus bacteremia was higher in patients with CDI compared to matched controls. The findings supported the hypothesis that CDI increases the risk of bacterial translocation specifically leading to the development of bacteremia.^

Molecular basis of Corynebacterium diphtheriae virulence and infection in the Caenorhabditis elegans model host

Corynebacterium diphtheriae is the causative agent of cutaneous and pharyngeal diphtheria in humans. While lethality is certainly caused by diphtheria toxin, corynebacterial colonization may primarily require proteinaceous fibers called pili, which mediate adherence to specific tissues. The type strain of C. diphtheriae possesses three distinct pilus structures, namely the SpaA, SpaD, and SpaH-type pili, which are encoded by three distinct pilus gene clusters. The pilus is assembled onto the bacterial peptidoglycan by a specific transpeptidase enzyme called sortase. Although the SpaA pili are shown to be specific for pharyngeal cells in vitro, little is known about functions of the three pili in bacterial pathogenesis. This is mainly due to lack of in vivo models of corynebacterial infection. As an alternative to mouse models as mice do not have functional receptors for diphtheria toxin, in this study I use Caenorhabditis elegans as a model host for C. diphtheriae. A simple C. elegans model would be beneficial in determining the specific role of each pilus-type and the literature suggests that C. elegans infection model can be used to study a variety of bacterial species giving insight into bacterial virulence and host-pathogen interactions. My study examines the hypothesis that pili and toxin are major virulent determinants of C. diphtheriae in the C. elegans model host.

Characterization of the ebp(fm) pilus-encoding operon of Enterococcus faecium and its role in biofilm formation and virulence in a murine model of urinary tract infection.

We recently identified 15 genes encoding putative surface proteins with features of MSCRAMMs and/or pili in the Enterococcus faecium TX0016 (DO) genome, including four predicted pilus-encoding gene clusters; we also demonstrated that one of these, ebpABC(fm), is transcribed as an operon, that its putative major pilus subunit, EbpC(fm) (also called pilB), is polymerized into high molecular weight complexes, and that it is enriched among clinical E. faecium isolates. Here, we created a deletion of the ebpABC(fm) operon in an endocarditis-derived E. faecium strain (TX82) and showed, by a combination of whole-cell ELISA, flow cytometry, immunoblot and immunogold electron microscopy, that this deletion abolished EbpC(fm) expression and eliminated EbpC(fm)-containing pili from the cell surface. However, transcription of the downstream sortase, bps(fm), was not affected. Importantly, the ebpABC(fm) deletion resulted in significantly reduced biofilm formation (p < 0.0001) and initial adherence (p < 0.0001) versus the wild-type; both were restored by complementing ebpABC(fm) in trans, which also restored cell surface expression of EbpC(fm) and pilus production. Furthermore, the deletion mutant was significantly attenuated in two independent mixed infection mouse urinary tract experiments, i.e., outnumbered by the wild-type in kidneys (p = 0.0003 and < 0.0001, respectively) and urinary bladders (p = 0.0003 and = 0.002). In conclusion, we have shown that the ebpABC(fm) locus encodes pili on the E. faecium TX82 cell surface and provide the first evidence that pili of this emerging pathogen are important for its ability to form biofilm and to cause infection in an ascending UTI model.

Importance of the ebp (endocarditis- and biofilm-associated pilus) locus in the pathogenesis of Enterococcus faecalis ascending urinary tract infection.

BACKGROUND: We recently demonstrated that the ubiquitous Enterococcus faecalis ebp (endocarditis- and biofilm-associated pilus) operon is important for biofilm formation and experimental endocarditis. Here, we assess its role in murine urinary tract infection (UTI) by use of wild-type E. faecalis OG1RF and its nonpiliated, ebpA allelic replacement mutant (TX5475). METHODS: OG1RF and TX5475 were administered transurethrally either at an ~1 : 1 ratio (competition assay) or individually (monoinfection). Kidney pairs and urinary bladders were cultured 48 h after infection. These strains were also tested in a peritonitis model. RESULTS: No differences were observed in the peritonitis model. In mixed UTIs, OG1RF significantly outnumbered TX5475 in kidneys (P=.0033) and bladders (P< or =.0001). More OG1RF colony-forming units were also recovered from the kidneys of monoinfected mice at the 4 inocula tested (P=.015 to P=.049), and 50% infective doses of OG1RF for kidneys and bladder (9.1x10(1) and 3.5x10(3) cfu, respectively) were 2-3 log(10) lower than those of TX5475. Increased tropism for the kidney relative to the bladder was observed for both OG1RF and TX5475. CONCLUSION: The ebp locus, part of the core genome of E. faecalis, contributes to infection in an ascending UTI model and is the first such enterococcal locus shown to be important in this site.

Detailed analysis of sequence changes occurring during vlsE antigenic variation in the mouse model of Borrelia burgdorferi infection.

Lyme disease Borrelia can infect humans and animals for months to years, despite the presence of an active host immune response. The vls antigenic variation system, which expresses the surface-exposed lipoprotein VlsE, plays a major role in B. burgdorferi immune evasion. Gene conversion between vls silent cassettes and the vlsE expression site occurs at high frequency during mammalian infection, resulting in sequence variation in the VlsE product. In this study, we examined vlsE sequence variation in B. burgdorferi B31 during mouse infection by analyzing 1,399 clones isolated from bladder, heart, joint, ear, and skin tissues of mice infected for 4 to 365 days. The median number of codon changes increased progressively in C3H/HeN mice from 4 to 28 days post infection, and no clones retained the parental vlsE sequence at 28 days. In contrast, the decrease in the number of clones with the parental vlsE sequence and the increase in the number of sequence changes occurred more gradually in severe combined immunodeficiency (SCID) mice. Clones containing a stop codon were isolated, indicating that continuous expression of full-length VlsE is not required for survival in vivo; also, these clones continued to undergo vlsE recombination. Analysis of clones with apparent single recombination events indicated that recombinations into vlsE are nonselective with regard to the silent cassette utilized, as well as the length and location of the recombination event. Sequence changes as small as one base pair were common. Fifteen percent of recovered vlsE variants contained "template-independent" sequence changes, which clustered in the variable regions of vlsE. We hypothesize that the increased frequency and complexity of vlsE sequence changes observed in clones recovered from immunocompetent mice (as compared with SCID mice) is due to rapid clearance of relatively invariant clones by variable region-specific anti-VlsE antibody responses.

Relative contributions of Enterococcus faecalis OG1RF sortase-encoding genes, srtA and bps (srtC), to biofilm formation and a murine model of urinary tract infection.

Deletion mutants of the two sortase genes of Enterococcus faecalis OG1RF were constructed. srtC (renamed here bps for biofilm and pilus-associated sortase) was previously shown to be necessary for the production of Ebp pili and important for biofilm formation and endocarditis. Here, we report that a srtA deletion mutant showed a small (5%) yet significant (P = 0.037) reduction in biofilm relative to OG1RF, while a DeltasrtA Deltabps double mutant showed a much greater reduction (74% versus OG1RF and 44% versus the Deltabps mutant). In a murine urinary tract infection (UTI), the 50% infective doses of both the DeltasrtA Deltabps and Deltabps mutants were approximately 2 log10 greater than that of OG1RF or the DeltasrtA mutant. Similarly, approximately 2 log10 fewer bacteria were recovered from the kidneys after infection with the Deltabps mutant (P = 0.017) and the DeltasrtA Deltabps double mutant (P = 0.022) compared to wild-type strain OG1RF. In a competition UTI, the Deltabps mutant was slightly, but not significantly, less attenuated than the DeltasrtA Deltabps double mutant. Fluorescence-activated cell sorter analysis with Ebp-specific antibodies confirmed that a minority of OG1RF cells express Ebp pili on their surface in vitro and that Bps has a major role in Ebp pilus biogenesis but also indicated a function for SrtA in surface localization of the pilus subunit protein EbpA. In conclusion, deletion of bps had a major effect on virulence in murine UTIs, as well as biofilm; deletion of srtA from OG1RF had little effect on these phenotypes, but its deletion from a bps mutant had a pronounced effect on biofilm, suggesting that Bps and/or the proteins it anchors may compensate for the loss of some SrtA function(s).

Relative contributions of Enterococcus faecalis OG1RF sortase-encoding genes, srtA and bps (srtC), to biofilm formation and a murine model of urinary tract infection.

Deletion mutants of the two sortase genes of Enterococcus faecalis OG1RF were constructed. srtC (renamed here bps for biofilm and pilus-associated sortase) was previously shown to be necessary for the production of Ebp pili and important for biofilm formation and endocarditis. Here, we report that a srtA deletion mutant showed a small (5%) yet significant (P = 0.037) reduction in biofilm relative to OG1RF, while a DeltasrtA Deltabps double mutant showed a much greater reduction (74% versus OG1RF and 44% versus the Deltabps mutant). In a murine urinary tract infection (UTI), the 50% infective doses of both the DeltasrtA Deltabps and Deltabps mutants were approximately 2 log10 greater than that of OG1RF or the DeltasrtA mutant. Similarly, approximately 2 log10 fewer bacteria were recovered from the kidneys after infection with the Deltabps mutant (P = 0.017) and the DeltasrtA Deltabps double mutant (P = 0.022) compared to wild-type strain OG1RF. In a competition UTI, the Deltabps mutant was slightly, but not significantly, less attenuated than the DeltasrtA Deltabps double mutant. Fluorescence-activated cell sorter analysis with Ebp-specific antibodies confirmed that a minority of OG1RF cells express Ebp pili on their surface in vitro and that Bps has a major role in Ebp pilus biogenesis but also indicated a function for SrtA in surface localization of the pilus subunit protein EbpA. In conclusion, deletion of bps had a major effect on virulence in murine UTIs, as well as biofilm; deletion of srtA from OG1RF had little effect on these phenotypes, but its deletion from a bps mutant had a pronounced effect on biofilm, suggesting that Bps and/or the proteins it anchors may compensate for the loss of some SrtA function(s).

Characterization of Staphylococcus aureus adhesins important for respiratory tract infection

Staphylococcus aureus is a leading cause of lower respiratory tract infections in both adult and pediatric populations. In the past two decades, reports have described emergent incidence of severe necrotizing pneumonia in previously healthy individuals, frequently caused by antibiotic resistant strains. Additionally, S. aureus remains the most common cause of ventilator-associated pneumonia, contributing morbidity and mortality in intensive care units. As treatment of infection is made more difficult by the resistance to multiple antibiotics including vancomycin, there is a pressing need for novel strategies to prevent and treat S. aureus infections. Targeting essential mechanisms that promote infection such as adhesion, colonization, invasion, evasion of immune system and signaling may lead to inhibition of pathogenic surge. Staphylococcal adhesins of the MSCRAMM family (microbial surface components recognizing adherent matrix molecules) represent viable targets for such investigations. Understanding the molecular mechanism of binding is the first step toward the development of such therapies. Analysis of bacterial strains isolated from patients with staphylococcal pneumonia show increased expression of protein A, SdrD, SdrC and ClfB, cell surface proteins members of the MSCRAMM family. In this study the interaction of these MSCRAMMs with candidate ligands has been examined. We found that SdrD mediates S. aureus adherence to the lung epithelial cell line A549. Consistently, bacteria expressing SdrD have increased persistence in the lungs of infected mice after bronchoalveolar lavage in comparison with bacteria lacking this protein. Inhibition studies revealed that bacterial attachment can be abolished using neutralizing antibodies against SdrD. Using phage display, neurexin β isoforms were identified as SdrC binding partners. Previous reports postulated that MSCRAMMS bind their ligands by a 'dock, lock and latch' mechanism of interaction. Our data suggested that ClfB, an MSCRAMM responsible for nasal colonization, binds cytokeratin 10 by a 'dock and lock' variant of this model, in which the 'latching' event is not necessary. In summary, we have characterized aspects of molecular interaction between several MSCRAMMS and host components. We hope that continued delineation of these interactions will lead to identification of novel therapeutic targets or preventive strategies against S. aureus infections. ^

Predictive factors for vaginal douching and tampon use among US women: Are these behaviors risk factors for bacterial vaginosis and trichomonas?

The use of feminine products such as vaginal douches, tampons, and sanitary napkins are common among women. Despite the results of some studies that suggest an association between douching and bacterial vaginosis, douching remains a topic that is understudied. The possibility of an association between tampon use and infection has not been significantly investigated since the toxic shock outbreak in the 1980s. The first objective of our study was to evaluate demographic, reproductive health, and sexual behavior variables to establish an epidemiologic profile of menstruating women who reported douching and women who reported using sanitary napkins only. The second objective of our study was to evaluate whether the behaviors of douching and using tampons were associated with an increased risk of bacterial vaginosis or trichomonas. We analyzed these factors, using logistic regression, among the 3,174 women from the NHANES cross sectional data from 2001-2004, who met the inclusion criteria determined for our study. We established an epidemiologic profile for women who had the highest frequency of douching reported as women who were age 36-49, had a high school education or GED, black race, not taking oral contraceptives, reported vaginal symptoms in the last month, two or more sexual partners in the last year, or tested positive for bacterial vaginosis or trichomonas. The profile for those who had the highest frequency of exclusive sanitary napkin use included women with less than a high school education, married women, women classified as black or "other" in race, and women who were not on oral contraceptives. While we were able to establish a significant increase in the odds of douching among women who tested positive for bacterial vaginosis or trichomonas, we did not find any significant difference in the odds of exclusive napkin use and testing negative for bacterial vaginosis or trichomonas.^

The influence of antibacterial susceptibility and pharmacodynamics on the therapeutic response of infection

This prospective cohort study estimated how antibacterial resistance affected the time until clinical response. Relative rates of improvement and cure were estimated by proportional-hazards regression for 391 patients with culture-confirmed bacterial keratitis who had the ciprofloxacin minimal inhibitory concentration (MIC) measured of the principal corneal isolate and who were treated with ciprofloxacin 0.3% solution or ointment. After adjusting for age and hypopyon status and stratifying by ulcer size, clinic, and ciprofloxacin formulation, the summary rate of clinical improvement with ciprofloxacin therapy was reduced by 42% (95% confidence limits [CL], 3%, 65%) among patients whose corneal isolate's ciprofloxacin MIC exceeded 1.0 μg/mL compared to those with more sensitive isolates. The summary rate of resolution to improvement and cure was reduced by 36% (95% CL, 11%, 53%) among corneal infections having a higher ciprofloxacin MIC. Rate ratios were modified by the size of the presenting corneal ulceration; for ulcer diameters of 4 mm or less and of more than 4 mm, improvement rate ratios were 0.56 (95% CL, 0.31, 1.02) and 0.65 (95% CL, 0.23, 1.80), respectively; resolution rate ratios were 0.63 (95% CL, 0.44, 0.91) and 0.67 (95% CL, 0.32, 1.39), respectively. Sensitivity analysis showed that the summary improvement rate ratio could be maximally overestimated by 24% (95% CL, −29%, 114%) because of informative censoring or by 33% (95% CL, −21%, 126%) from loss to follow up. Based on reported corneal pharmacokinetics of topical ciprofloxacin, the probability of clinical improvement was 90% or more if the ratio of the achievable corneal ciprofloxacin concentration to the corneal isolate's ciprofloxacin MIC was above 8 or the ratio of the area under the 24-hour corneal concentration curve to the ciprofloxacin MIC was greater than 151. This study suggests that corneal infections by bacteria having a higher ciprofloxacin MIC respond more slowly to ciprofloxacin treatment than those with a lower MIC. While the rate of clinical resolution is affected by patient age and clinical severity, antimicrobial susceptibility testing of corneal cultures can indicate the relative effectiveness of antibacterial therapy. A pharmacodynamic approach to treating bacterial keratitis offers the prospect of optimal antimicrobial selection and modification. ^