Mahdi A. Saeed

Multiple-locus variable-number tandem repeat analysis of Salmonella Enteritidis isolates from human and non-human sources using a single multiplex PCR

Simplified multiple-locus variable-number tandem repeat analysis (MLVA) was developed using one-shot multiplex PCR for seven variable-number tandem repeats (VNTR) markers with high diversity capacity. MLVA, phage typing, and PFGE methods were applied on 34 diverse Salmonella Enteritidis isolates from human and non-human sources. MLVA detected allelic variations that helped to classify the S. Enteritidis isolates into more evenly distributed subtypes than other methods. MLVA-based S. Enteritidis clonal groups were largely associated with sources of the isolates. Neis diversity indices for polymorphism ranged from 0.25 to 0.70 for seven VNTR loci markers. Based on Simpsons and Shannons diversity indices, MLVA had a higher discriminatory power than pulsed field gel electrophoresis (PFGE), phage typing, or multilocus enzyme electrophoresis. Therefore, MLVA may be used along with PFGE to enhance the effectiveness of the molecular epidemiologic investigation of S. Enteritidis infections.

The role of neighborhood level socioeconomic characteristics in Salmonella infections in Michigan (1997-2007): assessment using geographic information system.

Background:The majority of U.S. disease surveillance systems contain incomplete information regarding socioeconomic status (SES) indicators like household or family income and educational attainment in case reports, which reduces the usefulness of surveillance data for these parameters. We investigated the association between select SES attributes at the neighborhood level and Salmonella infections in the three most populated counties in Michigan using a geographic information system.Methods:We obtained data on income, education, and race from the 2000 U.S. Census, and the aggregate number of laboratory-confirmed cases of salmonellosis (1997–2006) at the block group level from the Michigan Department of Community Health. We used ArcGIS to visualize the distribution, and Poisson regression analysis to study associations between potential predictor variables and Salmonella infections.Results:Based on data from 3,419 block groups, our final multivariate model revealed that block groups with lower educational attainment were less commonly represented among cases than their counterparts with higher education levels (< high school degree vs. ≥ college degree: rate ratio (RR) = 0.79, 95% confidence interval (CI):0.63, 0.99; ≥ and high school degree, but no college degree vs. ≥ college degree: RR = 0.84, 95% CI: 0.76, 0.92). Levels of education also showed a dose-response relation with the outcome variable, i.e., decreasing years of education was associated with a decrease in Salmonella infections incidence at the block group level.Conclusion:Education plays a significant role in health-seeking behavior at the population level. It is conceivable that a reporting bias may exist due to a greater detection of Salmonella infections among high education block groups compared to low education block groups resulting from differential access to healthcare. In addition, individuals of higher education block groups who also have greater discretionary income may eat outside the home frequently and be more likely to own pets considered reservoirs of Salmonella, which increase the likelihood of contracting Salmonella infections compared to their counterparts with lower levels of education. Public health authorities should focus on improving the level of disease detection and reporting among communities with lower income and education and further evaluate the role of higher educational attainment in the predisposition for salmonellosis.

Prevalence and tissue distribution of Besnoitia darlingi cysts in the Virginia opossum (Didelphis virginiana) in Michigan

Specimens of Virginia opossums (Didelphis virginiana) in Michigan were examined over 1 year to document the presence of Besnoitia darlingi cysts. Cyst morphology, prevalence, seasonal variation, and tissue sites of isolation were studied. Histology and ultrastructural features of the detected cysts and bradyzoites were consistent with B. darlingi. In the opossums, B. darlingi had intracellular tissue cysts. Tissue cysts had a mean diameter of 560 microm and were separated from the host tissue by a thick (5-20 microm) cyst wall. Overall prevalence of B. darlingi cysts in opossums was 10.9% (15/137). Variations in the prevalence were detected during spring (3/17; 17.6%), summer (10/34; 29.4%), and fall (2/60; 3.3%). No cysts were detected in the specimens examined during winter (0/26; 0%). Numerous B. darlingi cysts were detected in ears, conjunctiva, tongue, abdominal muscles, diaphragm, stomach, heart, liver, kidney, lung, and spleen. Cysts were detected mainly in adult female opossums that were debilitated. Ear was the most frequent organ from which the cysts were reported (10/15; 66.7%) when compared individually with other body tissues (P<0.05).

Purification of Sarcocystis neurona sporocysts from opossum (Didelphis virginiana) using potassium bromide discontinuous density gradient centrifugation

This report describes a new, inexpensive procedure for the rapid and efficient purification of Sarcocystis neurona sporocysts from opossum small intestine. S. neurona sporocysts were purified using a discontinuous potassium bromide density gradient. The procedure provides a source of sporocyst wall and sporozoites required for reliable biochemical characterization and for immunological studies directed at characterizing antigens responsible for immunological responses by the host. The examined isolates were identified as S. neurona using random amplified polymorphic DNA primers and restriction endonuclease digestion assays. This method allows the collection of large numbers of highly purified S. neurona sporocysts without loss of sporocyst viability as indicated by propidium iodide permeability and cell culture infectivity assays. In addition, this technique might also be used for sporocyst purification of other Sarcocystis spp.

Case-control study of disease determinants for non-typhoidal Salmonella infections among Michigan children

BackgroundInfections with Salmonella serotypes continue to be a significant global public health problem. In addition to contaminated foods, several other sources contribute to infections with Salmonella serotypes. We have assessed the role of socioeconomic factors, exposure to food, and environmental sources in the etiology of non-typhoidal Salmonella infections in Michigan children.FindingsA case-control study among Michigan children aged ≤ 10 years was conducted. A total of 123 cases of children with laboratory-confirmed Salmonella infections and 139 control children, who had not experienced symptoms of gastrointestinal illness during the month prior to the interviews, were enrolled. The cases and controls were matched on age-category (<1 year, 2-<6 years and 6-10 years). Data on socioeconomic status, food intake, and environmental exposures, were collected on the queried case and control subjects. After adjusting for race and household-income the final regression multivariable model revealed that Salmonella infections were significantly associated with attendance of a daycare center (adjusted matched odds ratio = 5.00, 95% CI: 1.51 - 16.58), contact with cats (MOR = 2.53, 95% CI: 1.14 - 5.88), and contact with reptiles (MOR = 7.90, 95% CI: 1.52 - 41.01), during the 3 days prior to the onset of childs illness.ConclusionsStudy results suggest that exposure to environmental sources may play an important role in sporadic infections with Salmonella serotypes in children. Additional efforts are needed to educate parents and caretakers about the risk of Salmonella transmission to children from these sources.

Effects of temperature and host cell type on the in vitro growth and development of Sarcocystis falcatula

The growth and development of Sarcocystis falcatula in four different cultured cell lines [vero cells, bovine turbinate (BT) cells, equine dermal (ED) cells, and human Hep-2 cells] inoculated with culture-derived merozoites are described. Parasite yields, viability, and plaque forming efficiency were used to compare the growth between different cell lines. Additionally, each cell line was tested at two temperatures of incubation (35°C and 37°C). Based on yield, viability, and plaque forming efficiency, vero cells and BT cells supported growth of S. falcatula better than ED cells and Hep-2 cells. During an 18-day culture period, vero cells produced a mean total of 1.3×107 S. falcatula merozoites/T25 flask, BT cells 1.1×107, ED cells 0.9×107, and Hep-2 cells 0.7×107 merozoites/T25 flask. All experimental cell lines grew equally well at 35°C and 37°C. The type of host cells but not the temperature of incubation had a profound effect on the in vitro growth and proliferation of S. falcatula.

Spatial epidemiology of HIV-hepatitis co-infection in the State of Michigan: A cohort study

Abstract Background: Acquired immunodeficiency syndrome (AIDS) is a continuing global public health threat affecting millions of individuals. In 2009, 33.3 million people worldwide were living with human immunodeficiency virus (HIV) infection. HIV-infected individuals are at an increased risk of acquiring hepatitis B and hepatitis C viral (HBV, HCV)infections because of shared transmission routes. The purpose of this study was to identify geographical clusters of HIV-(HBV/HCV) co-infection in the State of Michigan. Methods: Retrospective cohort data on HIV-infected individuals were matched to all hepatitis B and C cases in Michigan during the period of January 1, 2006 through December 31, 2009. A prevalence map of HIV infection was created and spatial clusters of HIV-hepatitis B or C co-infection were detected using GeoDas bivariate local Morans I and SaTScans discrete Poisson model. Results: A bivariate cluster of high prevalence HIV and hepatitis B or C was identified in the Detroit Metropolitan Area and surrounding counties. A Poisson cluster of HIV-hepatitis B or C co-infection was identified, relative risk (RR) = 1.38 (p = 0.029) in the western and northwestern counties of Lower Michigan, controlling for sex, race, and AIDS status. Conclusion: This study identified elevated HIV-hepatitis B or C co-infection unexplained by sex, race or AIDS status in counties outside of the Detroit Metropolitan Area where HIV prevalence was highest in Michigan. The findings from this study may be used to target future public health policy and healthcare interventions for HIV-hepatitis co-infection in these areas.

Survival of HIV-positive individuals with hepatitis B and C infection in Michigan.

We sought to estimate mortality and associated factors in HIV-hepatitis co-infected individuals in Michigan using a retrospective cohort study. For the study period of 1 January 2006 to 31 December 2009, all HIV-infected individuals were matched to hepatitis B and C cases. In the final Cox proportional hazards regression model, individuals of other [hazard ratio (HR) 2·2, 95% confidence interval (CI) 1·4-3·2] and black (HR 1·3, 95% CI 1·1-1·6) race had decreased survival compared to white race. Similarly, injecting drug users (IDUs) (HR 2·1, 95% CI 1·6-2·6), men who have sex with men (MSM)/IDUs (HR 1·5, 95% CI 1·1-2·2), individuals with undetermined risk (HR 1·5, 95% CI 1·2-1·9) and heterosexual practices (HR 1·4, 95% CI 1·1-1·8) had decreased survival compared to MSM. Additionally, an interaction was found between current HIV status and co-infection. Mortality in HIV-hepatitis co-infected individuals remains a continuing problem. Our study can help in planning interventions to reduce mortality in HIV-infected individuals.

Hepatitis B and C co-infection in HIV/AIDS population in the state of Michigan

A retrospective cohort study was conducted from 1 January 2006 to 31 December 2009 in Michigan to estimate the prevalence of HIV and hepatitis co-infection and identify associated factors. The prevalence of co-infection was 4.1% [95% confidence interval (CI) 3.8-4.5]. Multivariable logistic regression analysis revealed a significant association between co-infection and being male and: of Black race [odds ratio (OR) 2.0, 95% CI 1.2-3.6] and of Other race (OR 3.5, 95% CI 1.7-7.0) compared to Hispanic race. A significant association was found between co-infection and risk categories of blood products (OR 11.1, 95% CI 6.2-20.2), injecting drug user (IDU) (OR 3.6, 95% CI 2.7-4.8) and men who have sex with men/IDU (OR 3.4, 95% CI 2.4-4.9) in addition to two interactions; one between sex and current HIV status and the other between current HIV status and age at HIV diagnosis. Our results document the changing epidemiology of HIV-hepatitis co-infection which can guide preventive measures and interventions to reduce the prevalence of hepatitis co-infection.