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1.  Calcified Neurocysticercus, Perilesional Edema, and Histologic Inflammation 
Here, we present the second report of the histopathology of a Taenia solium calcification giving rise to perilesional edema. This has important implications, because if perilesional edema lesions are inflammatory in character, immunosuppressive or anti-inflammatory medications, not just antiepileptic drugs alone, may be useful to prevent or treat recurring episodes in such patients.
PMCID: PMC3919241  PMID: 24394477
2.  Association Between Stool Enteropathogen Quantity and Disease in Tanzanian Children Using TaqMan Array Cards: A Nested Case-Control Study 
Etiologic studies of diarrhea are limited by uneven diagnostic methods and frequent asymptomatic detection of enteropathogens. Polymerase chain reaction-based stool pathogen quantification may help distinguish clinically significant infections. We performed a nested case-control study of diarrhea in infants from a community-based birth cohort in Tanzania. We tested 71 diarrheal samples and pre-diarrheal matched controls with a laboratory-developed TaqMan Array Card for 19 enteropathogens. With qualitative detection, no pathogens were significantly associated with diarrhea. When pathogen quantity was considered, rotavirus (odds ratio [OR] = 2.70 per log10 increase, P < 0.001), astrovirus (OR = 1.49, P = 0.01), and Shigella/enteroinvasive Escherichia coli (OR = 1.47, P = 0.04) were associated with diarrhea. Enterotoxigenic E. coli (0.15 SD decline in length-for-age z score after 3 months per log10 increase, P < 0.001) and Campylobacter jejuni/C. coli (0.11 SD decline, P = 0.003) in pre-diarrheal stools were associated with poor linear growth. Quantitative analysis can help refine the association between enteropathogens and disease in endemic settings.
PMCID: PMC3886409  PMID: 24189366
3.  Use of Mycobacteriophage Quantitative PCR on MGIT Broths for a Rapid Tuberculosis Antibiogram 
Journal of Clinical Microbiology  2014;52(5):1523-1528.
Phenotypic culture-based drug susceptibility testing (DST) for Mycobacterium tuberculosis is a valuable tool to identify four to six active drugs for individualized multidrug-resistant (MDR) tuberculosis (TB) regimens. Current culture-based methods are slow, however; therefore, we evaluated a rapid mycobacteriophage-based quantitative PCR (qPCR) assay for use directly on M. tuberculosis-positive MGIT broths. We compared phage qPCRs, using a simple cutoff of 3 for the ΔCq value (where Cq is quantification cycle, and ΔCq is calculated as the Cq of starting phage minus the Cq of TB isolates in drug-containing medium), on 325 clinical M. tuberculosis MGIT broth cultures versus the respective subcultured isolates tested by agar proportion. The median accuracy for the 13 drugs/concentrations tested was 98%, with most discrepancies being false-resistant results. Evaluation of phage qPCR on greater numbers of resistant strains of 393 isolates grown on Löwenstein-Jensen medium showed similar findings, with a median accuracy, sensitivity, and specificity of 97%, 90%, and 99%, respectively. This rapid culture-based DST methodology can be performed for any drug on TB-positive MGIT broths, with a specimen-to-antibiogram turnaround time of approximately 23.9 days, compared with waiting 58.6 days for isolate growth on solid medium followed by agar proportion DST.
PMCID: PMC3993688  PMID: 24574299
4.  Detection of Campylobacter in Stool and Determination of Significance by Culture, Enzyme Immunoassay, and PCR in Developing Countries 
Journal of Clinical Microbiology  2014;52(4):1074-1080.
Campylobacter is a common bacterial enteropathogen that can be detected in stool by culture, enzyme immunoassay (EIA), or PCR. We compared culture for C. jejuni/C. coli, EIA (ProSpecT), and duplex PCR to distinguish Campylobacter jejuni/C. coli and non-jejuni/coli Campylobacter on 432 diarrheal and matched control stool samples from infants in a multisite longitudinal study of enteric infections in Tanzania, Bangladesh, and Peru. The sensitivity and specificity of culture were 8.5% and 97.6%, respectively, compared with the results of EIA and 8.7% and 98.0%, respectively, compared with the results of PCR for C. jejuni/C. coli. Most (71.6%) EIA-positive samples were positive by PCR for C. jejuni/C. coli, but 27.6% were positive for non-jejuni/coli Campylobacter species. Sequencing of 16S rRNA from 53 of these non-jejuni/coli Campylobacter samples showed that it most closely matched the 16S rRNA of C. hyointestinalis subsp. lawsonii (56%), C. troglodytis (33%), C. upsaliensis (7.7%), and C. jejuni/C. coli (2.6%). Campylobacter-negative stool spiked with each of the above-mentioned Campylobacter species revealed reactivity with EIA. PCR detection of Campylobacter species was strongly associated with diarrhea in Peru (odds ratio [OR] = 3.66, P < 0.001) but not in Tanzania (OR = 1.56, P = 0.24) or Bangladesh (OR = 1.13, P = 0.75). According to PCR, Campylobacter jejuni/C. coli infections represented less than half of all infections with Campylobacter species. In sum, in infants in developing country settings, the ProSpecT EIA and PCR for Campylobacter reveal extremely high rates of positivity. We propose the use of PCR because it retains high sensitivity, can ascertain burden, and can distinguish between Campylobacter infections at the species level.
PMCID: PMC3993515  PMID: 24452175
5.  Etiology of Diarrhea in Bangladeshi Infants in the First Year of Life Analyzed Using Molecular Methods 
The Journal of Infectious Diseases  2013;208(11):1794-1802.
Background. Diarrhea causes enormous morbidity and mortality in developing countries, yet the relative importance of multiple potential enteropathogens has been difficult to ascertain.
Methods. We performed a longitudinal cohort study from birth to 1 year of age in 147 infants in Dhaka, Bangladesh. Using multiplex polymerase chain reaction, we analyzed 420 episodes of diarrhea and 1385 monthly surveillance stool specimens for 32 enteropathogen gene targets. For each infant we examined enteropathogen quantities over time to ascribe each positive target as a probable or less-likely contributor to diarrhea.
Results. Multiple enteropathogens were detected by the first month of life. Diarrhea was associated with a state of overall pathogen excess (mean number of enteropathogen gene targets (±SE), 5.6 ± 0.1 vs 4.3 ± 0.1 in surveillance stool specimens; P < .05). After a longitudinal, quantitative approach was applied to filter out less-likely contributors, each diarrheal episode still had an average of 3.3 probable or dominant targets. Enteroaggregative Escherichia coli, Campylobacter, enteropathogenic E. coli, rotavirus, and Entamoeba histolytica were the most frequent probable contributors to diarrhea. Rotavirus was enriched in moderate to severe diarrheal episodes.
Conclusions. In this community-based study diarrhea seemed to be a multipathogen event and a state of enteropathogen excess above a high carriage baseline.
PMCID: PMC3814844  PMID: 24041797
Diarrhea; PCR; rotavirus; enteroaggregative e.coli; Campylobacter
6.  Discordance across Several Methods for Drug Susceptibility Testing of Drug-Resistant Mycobacterium tuberculosis Isolates in a Single Laboratory 
Journal of Clinical Microbiology  2014;52(1):156-163.
Given the increases in drug-resistant tuberculosis, laboratory capacities for drug susceptibility testing are being scaled up worldwide. A laboratory must decide among several endorsed methodologies. We evaluated 87 Mycobacterium tuberculosis isolates for concordance of susceptibility results across six methods: the L-J proportion method, MGIT 960 SIRE AST, Gene/Xpert MTB/RIF, GenoType MTBDRplus line probe assay, MycoTB MIC plate, and a laboratory-developed mycobacteriophage quantitative PCR (qPCR)-based method. Most (80%) isolates were multidrug resistant. Of the culture-based methods, the mycobacteriophage qPCR method was fastest, the L-J proportion method was the slowest, and the MGIT method required the most repeat testing (P < 0.05). For isoniazid (INH), 82% of isolates were susceptible by all methods or resistant by all methods, whereas for rifampin (RIF), ethambutol (EMB), and streptomycin (STR), such complete concordance was observed in 77%, 50%, and 51% of isolates, respectively (P < 0.05 for INH or RIF versus EMB or STR). The discrepancies of EMB and STR stemmed largely from diminished concordance of the MGIT EMB results (kappa coefficient range, 0.26 to 0.30) and the L-J STR result (kappa range, 0.35 to 0.45) versus other methods. Phage qPCR and the MycoTB MIC plate were the only methods that yielded second-line susceptibilities and revealed significant quantitative correlations for all drugs except cycloserine, as well as moderate to excellent kappa coefficients for all drugs except for para-aminosalicylic acid. In summary, the performance of M. tuberculosis susceptibility testing differs by platform and by drug. Laboratories should carefully consider these factors before choosing one methodology, particularly in settings where EMB and STR results are clinically important.
PMCID: PMC3911413  PMID: 24172155
7.  A Laboratory-Developed TaqMan Array Card for Simultaneous Detection of 19 Enteropathogens 
Journal of Clinical Microbiology  2013;51(2):472-480.
The TaqMan Array Card (TAC) system is a 384-well singleplex real-time PCR format that has been used to detect multiple infection targets. Here we developed an enteric TaqMan Array Card to detect 19 enteropathogens, including viruses (adenovirus, astrovirus, norovirus GII, rotavirus, and sapovirus), bacteria (Campylobacter jejuni/C. coli, Clostridium difficile, Salmonella, Vibrio cholerae, diarrheagenic Escherichia coli strains including enteroaggregative E. coli [EAEC], enterotoxigenic E. coli [ETEC], enteropathogenic E. coli [EPEC], and Shiga-toxigenic E. coli [STEC]), Shigella/enteroinvasive E. coli (EIEC), protozoa (Cryptosporidium, Giardia lamblia, and Entamoeba histolytica), and helminths (Ascaris lumbricoides and Trichuris trichiura), as well as two extrinsic controls to monitor extraction and amplification efficiency (the bacteriophage MS2 and phocine herpesvirus). Primers and probes were newly designed or adapted from published sources and spotted onto microfluidic cards. Fecal samples were spiked with extrinsic controls, and DNA and RNA were extracted using the QiaAmp Stool DNA minikit and the QuickGene RNA Tissue kit, respectively, and then mixed with Ag-Path-ID One Step real-time reverse transcription-PCR (RT-PCR) reagents and loaded into cards. PCR efficiencies were between 90% and 105%, with linearities of 0.988 to 1. The limit of detection of the assays in the TAC was within a 10-fold difference from the cognate assays performed on plates. Precision testing demonstrated a coefficient of variation of below 5% within a run and 14% between runs. Accuracy was evaluated for 109 selected clinical specimens and revealed an average sensitivity and specificity of 85% and 77%, respectively, compared with conventional methods (including microscopy, culture, and immunoassay) and 98% and 96%, respectively, compared with our laboratory-developed PCR-Luminex assays. This TAC allows fast, accurate, and quantitative detection of a broad spectrum of enteropathogens and is well suited for surveillance or clinical purposes.
PMCID: PMC3553916  PMID: 23175269
8.  Plasma Drug Activity in Patients on Treatment for Multidrug-Resistant Tuberculosis 
Little is known about plasma drug concentrations relative to quantitative susceptibility in patients with multidrug-resistant tuberculosis (MDR-TB). We previously described a TB drug activity (TDA) assay that determines the ratio of the time to detection of plasma-cocultured Mycobacterium tuberculosis versus control growth in a Bactec MGIT system. Here, we assess the activity of individual drugs in a typical MDR-TB regimen using the TDA assay. We also examined the relationship of the TDA to the drug concentration at 2 h (C2) and the MICs among adults on a MDR-TB regimen in Tanzania. These parameters were also compared to the treatment outcome of sputum culture conversion. Individually, moxifloxacin yielded superior TDA results versus ofloxacin, and only moxifloxacin and amikacin yielded TDAs equivalent to a −2-log killing. In the 25 patients enrolled on a regimen of kanamycin, levofloxacin, ethionamide, pyrazinamide, and cycloserine, the C2 values were found to be below the expected range for levofloxacin in 13 (52%) and kanamycin in 10 (40%). Three subjects with the lowest TDA result (<1.5, a finding indicative of poor killing) had significantly lower kanamycin C2/MIC ratios than subjects with a TDA of ≥1.5 (9.8 ± 8.7 versus 27.0 ± 19.1; P = 0.04). The mean TDAs were 2.52 ± 0.76 in subjects converting to negative in ≤2 months and 1.88 ± 0.57 in subjects converting to negative in >2 months (P = 0.08). In Tanzania, MDR-TB drug concentrations were frequently low, and a wide concentration/MIC range was observed that affected plasma drug activity ex vivo. An opportunity exists for pharmacokinetic optimization in current MDR-TB regimens, which may improve treatment response.
PMCID: PMC3910816  PMID: 24247125
9.  Enteroaggregative Escherichia coli quantification in children stool samples using quantitative PCR 
Enteroaggregative Escherichia coli (EAEC) is a common cause of infectious diarrhea, especially in children living in poor-resource countries. In this article, we present a SYBR Green-based real-time polymerase chain reaction (qPCR) method for quantitative detection of EAEC in DNA directly extracted from human stool samples. In order to test the proposed qPCR system, we examined specificity, sensitivity, repeatability, and also the degree of DNA extraction efficiency using EAEC strain 042 spiked into EAEC-free stool sample. The specificity of this assay was proved using 6 strains of EAEC, 7 strains of other E. coli types, and one strain of Shigella. The detection limit of qPCR was 67 CFU/reaction. In naturally infected stool samples, we found EAEC in quantities varying from 6.7 × 105 to 2 × 109 CFU/g of feces. We could not detect any reduction after stool DNA extraction for the amounts of 107 and 106 CFU/mL of spiked EAEC. This qPCR assay is simple, rapid, reproducible, sensitive, specific, and allows rapid EAEC quantification to be used in a variety of further EAEC studies. This new quantitative method provides a relatively simple means to quantifify EAEC, which will likely be key to understanding the pathophysiology and impact of EAEC infection.
PMCID: PMC3604144  PMID: 23216208
qPCR; Enteroaggregative Escherichia coli; DNA stool samples; childhood diarrhea
10.  Giardia intestinalis Assemblages A and B Infections in Nepal 
Giardia intestinalis is comprised of two major genotypes, A and B, which may vary in their propensity to cause disease. We tested for the presence of these two genotypes in stool samples from patients with gastrointestinal symptoms in Nepal. A total of 1,096 clinical specimens were screened by microscopy, and 45 samples with G. intestinalis were identified. Giardia infection was confirmed in 35 of 45 samples by a Giardia specific real-time polymerase chain reaction (PCR) assay. Genotyping of the Giardia PCR product by restriction fragment length polymorphism indicated that 74% (26 of 35) were assemblage B, 20% (7 of 35) were assemblage A, and 6% (2 of 35) were mixed assemblages.
PMCID: PMC3412867  PMID: 19706929
11.  Efficacy of Antiamebic Drugs in a Mouse Model 
Nitroimidazole antibiotics are the mainstay of treatment of invasive amebiasis; however, few comparative studies of applicable antibiotics are available. Evidence of sporadic clinical failure and rare reports of metronidazole resistance have led to the investigation of novel antiamebic therapeutics. The goal of this study was to examine drug efficacy in both in vitro and in vivo models of intestinal amebiasis. We studied six current and three novel drugs. Many drugs, including metronidazole, nitazoxanide, and nitazoxanide derivatives, were shown to be potently inhibitory in vitro. However, metronidazole remained the most effective in vivo, both in preventative and curative regimens, underscoring the value of animal models in evaluating future therapies.
PMCID: PMC3062453  PMID: 21460014
12.  CD4+ and CD8+ T cell- and IL-17-mediated Protection against Entamoeba histolytica Induced by a Recombinant Vaccine 
Vaccine  2010;29(4):772-777.
Amebiasis in the murine model can be prevented by vaccination with the Gal/GalNAc lectin through a T cell-dependent mechanism. In this work we further decipher the mechanism of this protection. Mice vaccinated with the recombinant “LecA” fragment of the Gal/GalNAc lectin with alum were capable of transferring protection to naïve recipients by both CD4+ T cells and surprisingly CD8+ T cells. We then examined the cytokine profile of these cells. CD4+ T cells from PBMC of LecA-alum vaccinated mice were observed to be a major source of IFN-γ, known to be a protective cytokine with this vaccine. In contrast, CD8+ T cells produced relatively little IFN-γ but more IL-17 than the CD4 compartment. We thus examined the role of IL-17 in vaccine mediated protection and found through neutralization experiments that this cytokine contributed to LecA-alum vaccine protection. In addition we examined whether these cells exhibited direct amebicidal activity in vitro and found that both populations had amebicidal activity at high concentrations (1000:1) but CD8+ T cells appeared more potent, capable of cytotoxicity at a 100:1 ratio. In conclusion, both CD4 and CD8 T cells exert protection with this amebiasis vaccine. The mechanism of CD8 T cell-mediated protection may include direct amebicidal activity and/or IL-17 production. Both IL-17 and IFN- γ are useful surrogates for immune protection.
PMCID: PMC3014458  PMID: 21095257
Vaccine; Entamoeba histolytica; CD8+ T cell; IL-17; Amebicidal activity
13.  Febrile illness and pro-inflammatory cytokines are associated with lower neurodevelopmental scores in Bangladeshi infants living in poverty 
BMC Pediatrics  2014;14:50.
An estimated one-third of children younger than 5 years in low- and middle-income countries fail to meet their full developmental potential. The first year of life is a period of critical brain development and is also when most of the morbidity from infection is suffered. We aimed to determine if clinical and biological markers of inflammation in the first year of life predict cognitive, language, and motor outcomes in children living in an urban slum in Bangladesh.
Children living in Dhaka, Bangladesh were observed from birth until 24 months of age. Febrile illness was used as a clinical marker of inflammation and elevated concentrations of inflammation-related cytokines (IL-1β, IL-6, TNF-α, IL-4, IL-10) in sera collected from a subset of the cohort (N = 127) at 6 months of age were used as biomarkers of inflammation. Psychologists assessed cognitive, language, and motor development using a culturally adapted version of the Bayley Scales of Infant and Toddler Development, Third Edition (Bayley-III) at 12 (N = 398) and 24 months of age (N = 210). We tested for the ability of febrile illness and elevated cytokine levels to predict developmental outcomes, independent of known predictors of stunting, family income, and maternal education.
Every additional 10 days of fever was associated with a 1.9 decrease in language composite score and a 2.1 decrease in motor composite score (p = 0.005 and 0.0002, respectively). Elevated levels of the pro-inflammatory cytokines IL-1β (> 7.06 pg/mL) and IL-6 (> 10.52 pg/mL) were significantly associated with a 4.9 and 4.3 decrease in motor score, respectively. Conversely, an elevated level of the Th-2 cytokine IL-4 (> 0.70 pg/mL) was associated with a 3.6 increase in cognitive score (all p < 0.05).
Clinical and biological markers of inflammation in the first year of life were significantly associated with poor neurodevelopmental outcomes. Conversely, a Th2-like response was associated with a better outcome. These findings suggest that markers of inflammation could serve as prognostic indicators and potentially lead to immune-based therapies to prevent developmental delays in at-risk children.
PMCID: PMC3936797  PMID: 24548288
IL-1β; IL-6; IL-4; Child development; Cognition; Fever; Inflammation; Motor; Neurodevelopment; Pro-inflammatory
14.  Leptin Signaling in Intestinal Epithelium Mediates Resistance to Enteric Infection by Entamoeba histolytica 
Mucosal immunology  2010;4(3):294-303.
Leptin is an adipocytokine that links nutrition to immunity. Previous observation that a genetic polymorphism in the leptin receptor affected susceptibility to Entamoeba histolytica infection led to the hypothesis that leptin signaling plays a protective role during intestinal amebic infection. Here we show that mice lacking the functional leptin receptor developed devastating mucosal destruction after E. histolytica infection. Bone marrow chimera experiments demonstrated that leptin receptor expressed on hematopoietic cells was not sufficient to confer resistance. Similarly peripheral knockout of the leptin receptor rendered animals susceptible, indicating that central expression of the leptin receptor was not sufficient to confer protection. The site of leptin action was localized to the gut via an intestinal epithelium-specific deletion of the leptin receptor, which rendered mice susceptible to infection and mucosal destruction by the parasite. Mutation of tyrosine 985 or 1138 in the intracellular domain of the leptin receptor, which mediates signaling through the SHP2/ERK and STAT3 pathways respectively, demonstrated that both were important for mucosal protection. We conclude that leptin-mediated resistance to amebiasis is via its actions on intestinal epithelium rather than hematopoietic cells or the brain, and requires leptin receptor signaling through both the STAT3 and SHP2/ERK pathways.
PMCID: PMC3079783  PMID: 21124310
15.  Quantitative PCR for Detection of Shigella Improves Ascertainment of Shigella Burden in Children with Moderate-to-Severe Diarrhea in Low-Income Countries 
Journal of Clinical Microbiology  2013;51(6):1740-1746.
Estimates of the prevalence of Shigella spp. are limited by the suboptimal sensitivity of current diagnostic and surveillance methods. We used a quantitative PCR (qPCR) assay to detect Shigella in the stool samples of 3,533 children aged <59 months from the Gambia, Mali, Kenya, and Bangladesh, with or without moderate-to-severe diarrhea (MSD). We compared the results from conventional culture to those from qPCR for the Shigella ipaH gene. Using MSD as the reference standard, we determined the optimal cutpoint to be 2.9 × 104 ipaH copies per 100 ng of stool DNA for set 1 (n = 877). One hundred fifty-eight (18%) specimens yielded >2.9 × 104 ipaH copies. Ninety (10%) specimens were positive by traditional culture for Shigella. Individuals with ≥2.9 × 104 ipaH copies have 5.6-times-higher odds of having diarrhea than those with <2.9 × 104 ipaH copies (95% confidence interval, 3.7 to 8.5; P < 0.0001). Nearly identical results were found using an independent set of samples. qPCR detected 155 additional MSD cases with high copy numbers of ipaH, a 90% increase from the 172 cases detected by culture in both samples. Among a subset (n = 2,874) comprising MSD cases and their age-, gender-, and location-matched controls, the fraction of MSD cases that were attributable to Shigella infection increased from 9.6% (n = 129) for culture to 17.6% (n = 262) for qPCR when employing our cutpoint. We suggest that qPCR with a cutpoint of approximately 1.4 × 104 ipaH copies be the new reference standard for the detection and diagnosis of shigellosis in children in low-income countries. The acceptance of this new standard would substantially increase the fraction of MSD cases that are attributable to Shigella.
PMCID: PMC3716050  PMID: 23536399
16.  Early Therapeutic Drug Monitoring for Isoniazid and Rifampin among Diabetics with Newly Diagnosed Tuberculosis in Virginia, USA 
Slow responders to tuberculosis (TB) treatment in Virginia have prolonged treatment duration and consume more programmatic resources. Diabetes is an independent risk factor for slow response and low serum anti-TB drug concentrations. Thus, a statewide initiative of early therapeutic drug monitoring (TDM) for isoniazid and rifampin at 2 weeks after TB treatment was piloted for all diabetics with newly diagnosed TB. During the period of early TDM, 12/01/2011–12/31/2012, 21 diabetics had C2 hr concentrations performed and 16 (76%) had a value below the expected range for isoniazid, rifampin, or both. Fifteen had follow-up concentrations after dose adjustment and 12 (80%) increased to within the expected range (including all for rifampin). Of 16 diabetic patients with pulmonary TB that had early TDM, 14 (88%) converted their sputum culture to negative in <2 months. Early TDM for diabetics was operationally feasible, may speed response to TB therapy, and can be considered for TB programs with high diabetes prevalence.
PMCID: PMC3855970  PMID: 24349775
17.  Primary Multidrug-Resistant Mycobacterium tuberculosis in 2 Regions, Eastern Siberia, Russian Federation 
Emerging Infectious Diseases  2013;19(10):1649-1652.
Of 235 Mycobacterium tuberculosis isolates from patients who had not received tuberculosis treatment in the Irkutsk oblast and the Sakha Republic (Yakutia), eastern Siberia, 61 (26%) were multidrug resistant. A novel strain, S 256, clustered among these isolates and carried eis-related kanamycin resistance, indicating a need for locally informed diagnosis and treatment strategies.
PMCID: PMC3810730  PMID: 24047678
tuberculosis; multidrug-resistant tuberculosis; MDR TB; HIV; Siberia; Russian Federation; genotype; mycobacterial interspersed repetitive unit; MIRU-VNTR; pncA; pyrazinamide; tuberculosis and other mycobacteria
18.  Protection against Intestinal Amebiasis by a Recombinant Vaccine Is Transferable by T Cells and Mediated by Gamma Interferon▿  
Infection and Immunity  2009;77(9):3909-3918.
We have previously shown that vaccination with purified Entamoeba histolytica Gal/GalNAc lectin or recombinant subunits can protect mice from intestinal amebiasis upon intracecal challenge. In this study, we demonstrated with adoptive-transfer experiments that this lectin vaccine protection is mediated by T cells but not serum. The cell-mediated immune (CMI) response was characterized by significant gamma interferon (IFN-γ), interleukin 12 (IL-12), IL-2, IL-10, and IL-17 production. To move toward a human vaccine, we switched to a recombinant protein and tested a range of adjuvants and routes appropriate for humans. We found that subcutaneous delivery of LecA with IDRI's adjuvant system EM014 elicited a potent Th1-type CMI profile and provided significant protection, as measured by culture negativity (79% efficacy); intranasal immunization with cholera toxin provided 56% efficacy; and alum induced a Th2-type response that protected 62 to 68% of mice. Several antibody and CMI cytokine responses were examined for correlates of protection, and prechallenge IFN-γ+ or IFN-γ-, IL-2-, and tumor necrosis factor alpha-triple-positive CD4 cells in blood were statistically associated with protection. To test the role of IFN-γ in LecA-mediated protection, we neutralized IFN-γ in LecA-immunized mice and found that it abrogated the protection conferred by vaccination. These data demonstrate that CMI is sufficient for vaccine protection from intestinal amebiasis and reveal an important role for IFN-γ, even in the setting of alum.
PMCID: PMC2738017  PMID: 19564375
19.  Application of quantitative second-line drug susceptibility testing at a multidrug-resistant tuberculosis hospital in Tanzania 
BMC Infectious Diseases  2013;13:432.
Lack of rapid and reliable susceptibility testing for second-line drugs used in the treatment of multidrug-resistant tuberculosis (MDR-TB) may limit treatment success.
Mycobacterium tuberculosis isolates from patients referred to Kibong’oto National TB Hospital in Tanzania for second-line TB treatment underwent confirmatory speciation and susceptibility testing. Minimum inhibitory concentration (MIC) testing on MYCOTB Sensititre plates was performed for all drugs available in the second-line formulary. We chose to categorize isolates as borderline susceptible if the MIC was at or one dilution lower than the resistance breakpoint. M. tuberculosis DNA was sequenced for resistance mutations in rpoB (rifampin), inhA (isoniazid, ethionamide), katG (isoniazid), embB (ethambutol), gyrA (fluoroquinolones), rrs (amikacin, kanamycin, capreomycin), eis (kanamycin) and pncA (pyrazinamide).
Of 22 isolates from patients referred for second-line TB treatment, 13 (59%) were MDR-TB and the remainder had other resistance patterns. MIC testing identified 3 (14%) isolates resistant to ethionamide and another 8 (36%) with borderline susceptibility. No isolate had ofloxacin resistance, but 10 (45%) were borderline susceptible. Amikacin was fully susceptible in 15 (68%) compared to only 11 (50%) for kanamycin. Resistance mutations were absent in gyrA, rrs or eis for all 13 isolates available for sequencing, but pncA mutation resultant in amino acid change or stop codon was present in 6 (46%). Ten (77%) of MDR-TB patients had at least one medication that could have logically been modified based on these results (median 2; maximum 4). The most common modifications were a change from ethioniamide to para-aminosalicylic acid, and the use of higher dose levofloxacin.
In Tanzania, quantitative second-line susceptibility testing could inform and alter MDR-TB management independent of drug-resistance mutations. Further operational studies are warranted.
PMCID: PMC3848720  PMID: 24034230
Multidrug-resistant tuberculosis; Minimum inhibitory concentration; Aminoglycosides; Flouroquinolones; Para-aminosalicylic acid; Ethionamide; rpoB; inhA; embB; pncA
20.  High Prevalence of Entamoeba moshkovskii in a Tanzanian HIV population 
Acta tropica  2008;107(1):48-49.
Entamoeba moshkovskii and Entamoeba dispar are microscopically indistinguishable from the pathogenic species Entamoeba histolytica. There are limited data on the prevalence of these commensal infections from Africa. We utilized PCR and antigen detection to evaluate the carriage rate of E. moshkovskii, E. dispar, and E. histolytica infection in stool from a cohort of HIV-suspected or confirmed inpatients from Tanzania. Entamoeba histolytica was detected by ELISA in 4% (5/118) while Entamoeba moshkovskii and E. dispar were detected by PCR in 13% (18/136) and 5% (7/136) of individuals, respectively (P < 0.05). Supporting their commensal nature, neither Entamoeba moshkovskii nor E. dispar infection was statistically associated with HIV status, CD4 count, or the presence of diarrhea. These data suggest E. moshkovskii is a common infection in HIV-infected individuals in northern Tanzania and supports the concept that the microscopic detection of Entamoeba should be interpreted cautiously.
PMCID: PMC2459240  PMID: 18471796
Entamoeba; moshkovskii; histolytica; dispar; Tanzania; HIV
Cryptosporidium is a significant cause of diarrheal illness worldwide, especially among children and immunocompromised patients. Currently used diagnostic techniques are time-consuming, require skilled technicians, and are not useful for quantification of oocysts in fecal and environmental samples. In this study, we examined the use of a real-time polymerase chain reaction (PCR) assay for detecting and quantifying Cryptosporidium parvum in three distinct and progressively more complex matrices: phosphate-buffered saline (PBS), HCT-8 cells (human ileocecal carcinoma), and human fecal specimens. A reliable standard curve was generated using the PBS samples spiked with pure oocysts, and oocyst starting quantities were calculated for the infected HCT-8 cell and spiked fecal samples. The assay detected Cryptosporidium in samples infected/spiked with ≥103 oocysts/sample and detected both C. hominis and C. parvum in clinical specimens. This assay is useful in a variety of samples in the research laboratory and will likely prove to be a useful tool in the clinical laboratory.
PMCID: PMC2253489  PMID: 17488919
22.  Diagnosis and Interim Treatment Outcomes from the First Cohort of Multidrug-Resistant Tuberculosis Patients in Tanzania 
PLoS ONE  2013;8(5):e62034.
Kibong’oto National Tuberculosis Hospital (KNTH), Kilimanjaro, Tanzania.
Characterize the diagnostic process and interim treatment outcomes from patients treated for multidrug-resistant tuberculosis (MDR-TB) in Tanzania.
A retrospective cohort study was performed among all patients treated at KNTH for pulmonary MDR-TB between November 2009 and September 2011.
Sixty-one culture-positive MDR-TB patients initiated therapy, 60 (98%) with a prior history of TB treatment. Forty-one (67%) were male and 9 (14%) were HIV infected with a mean CD4 count of 424 (±106) cells/µl. The median time from specimen collection to MDR-TB diagnosis and from diagnosis to initiation of MDR-TB treatment was 138 days (IQR 101–159) and 131 days (IQR 32–233), respectively. Following treatment initiation four (7%) patients died (all HIV negative), 3 (5%) defaulted, and the remaining 54 (89%) completed the intensive phase. Most adverse drug reactions were mild to moderate and did not require discontinuation of treatment. Median time to culture conversion was 2 months (IQR 1–3) and did not vary by HIV status. In 28 isolates available for additional second-line drug susceptibility testing, fluoroquinolone, aminoglycoside and para-aminosalicylic acid resistance was rare yet ethionamide resistance was present in 9 (32%).
The majority of MDR-TB patients from this cohort had survived a prolonged referral process, had multiple episodes of prior TB treatment, but did not have advanced AIDS and converted to culture negative early while completing an intensive inpatient regimen without serious adverse event. Further study is required to determine the clinical impact of second-line drug susceptibility testing and the feasibility of alternatives to prolonged hospitalization.
PMCID: PMC3652861  PMID: 23675411
23.  Dual probe DNA capture for sensitive real-time PCR detection of Cryptosporidium and Giardia 
Molecular and Cellular Probes  2011;26(2):104-106.
Nucleic acid amplification for the enteropathogens Cryptosporidium and Giardia is complicated by low target template concentrations and PCR inhibitors. In this work we designed dual capture oligonucleotides for both Cryptosporidium and Giardia 18S rRNA targets which when utilized during DNA extraction from stool improved the limit of detection of our multiplex PCR assay by 1-2 logs, to as little as 10 cysts. When applied to clinical specimens, the method improved the real-time PCR CT by an average of 10.7 9.7 cycles. This work provides a highly sensitive protocol for Cryptosporidium and Giardia when limit of detection is of utmost importance.
PMCID: PMC3319247  PMID: 22227113
Cryptosporidium; Giardia; PCR; fecal
24.  18-fluorodeoxyglucose positron emission tomography for tuberculosis diagnosis and management: a case series 
F-fluorodeoxyglucose positron emission tomography (FDG-PET) is increasingly used to investigate for malignancy in the evaluation of pulmonary nodules, yet both active tuberculosis (TB) and malignancy have high uptake of FDG. Definitive diagnosis of TB can be further hindered in patients without growth of the organism from sputum.
Case presentations
We describe a series of four representative cases of TB in varying disease state originally imaged by FDG-PET during evaluation for malignancy. Decisions regarding treatment for active TB in the presence of negative cultures and the evolving understanding of the spectrum of the TB disease state are discussed.
FDG-PET may possess a role in the diagnosis of active TB infection in settings where conventional microbiological methods are unavaiable and holds particular promise for monitoring response to therapy in cases of unsettled treatment duration such as multidrug-resistant TB or in extrapulmonary TB.
PMCID: PMC3637578  PMID: 23514625
Positron emission tomography; Tuberculosis; Multidrug-resistant tuberculosis; Pulmonary nodule
25.  Molecular Diagnosis of Diarrhea: Current Status and Future Potential 
Determining the microbiologic etiology of enteric infection remains an elusive goal. Conventional approaches, including culture, microscopy, and antigen-based tests have significant limitations such as limit of detection and the need for multiple procedures. Molecular diagnostics, especially PCR based tests, are rapidly changing research and practice in infectious diseases. Diarrheal disease, with its broad range of potential infectious etiologies, is well suited for multiplex molecular testing. This review highlights examples of currently employed molecular tests, as well as ways in which these tests can be applied in the future. The absence of a gold standard for the microbiologic cause of diarrhea means that the clinical significance of detected organisms may not always be clear. Conventional wisdom is that there should be one main pathogen causing diarrhea, however our thinking is challenged by increased detection of mixed infections. Thus, the successful incorporation of molecular diagnostics for diarrheal disease into practice will require both a careful understanding of the technical aspects and research to define their clinical utility.
PMCID: PMC3253426  PMID: 22116640
diarrhea; molecular diagnosis; PCR; enteropathogens

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