Jamal A Mohamed

University of Texas Medical School, Houston, Texas, United States

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Publications (29)83.56 Total impact

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    ABSTRACT: Minocycline-rifampin-impregnated central venous catheters (M/R CVCs) have been shown to be efficacious in reducing catheter-related bloodstream infections (CRBSI) and inhibiting the biofilm adherence of resistant Gram-positive and Gram-negative pathogens, with the exception of Pseudomonas aeruginosa and Candida spp. To expand the spectrum of antimicrobial activity, a novel second-generation M/R catheter was developed by adding chlorhexidine (CHX-M/R). CVCs and peripherally inserted central catheters (PICCs) were impregnated with CHX-M/R and compared with first-generation M/R catheters, CHX-silver sulfadiazine-treated CVCs (CHX/SS-CVCs), chlorhexidine-treated PICCs, and uncoated catheters. A biofilm catheter colonization model was used to assess the efficacy of catheters against methicillin-resistant Staphylococcus aureus (MRSA), vancomycin-resistant Enterococcus faecium (VRE), P. aeruginosa, Candida albicans, and Candida glabrata. CHX-M/R-impregnated CVCs were the only antimicrobial catheters that completely inhibited the biofilm colonization of all resistant bacterial and fungal organisms tested at all time intervals, and they were significantly superior to uncoated catheters (all P values were ≤0.003). Furthermore, CHX-M/R-coated CVCs had a significantly more effective and prolonged (up to 3 weeks) antimicrobial activity against MRSA and P. aeruginosa than M/R, CHX/SS, and uncoated CVCs (P < 0.0001). Similarly, CHX-M/R-coated PICCs were also superior to M/R-coated and CHX-coated PICCs in preventing biofilms of MRSA, VRE, P. aeruginosa, and Candida species (P value = 0.003 for all). Our study shows that novel CHX-M/R-coated catheters have unique properties in completely inhibiting biofilm colonization of MRSA, VRE, P. aeruginosa, and fungi in a manner superior to that of M/R- and chlorhexidine-treated catheters.
    Antimicrobial Agents and Chemotherapy 11/2011; 56(2):935-41. · 4.57 Impact Factor
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    ABSTRACT: Comparison of three antimicrobial coated peripherally inserted central venous catheters (PICCs): What is on the horizon. Background: PICCs have been associated with a greater risk of blood stream infection in hospitalized patients, which are non-tunneled and non-cuffed, and prolonged use may predispose them to microbial colonization and biofilm formation. Impregnated PICCs with antimicrobial agents (aPICCs) might reduce the risk of BSI. We report the in vitro efficacy of 2 FDA approved aPICCS [minocycline/rifampin (M/R) and chlorhexidine (CHX)] and novel a combination of both (CHX-M/R) tested against different pathogens. Methods: PICCs of M/R and CHX PICCs were compared to CHX-M/R and uncoated PICCs (as a control) against methicillin-resistant Staphylococcus aureus (MRSA), Pseudomonas aeruginosa (PS), Candida albicans (CA), and C. glabrata (CG) by challenge in an established biofilm catheter colonization model. Results: All aPICCs significantly decreased the colonization of MRSA (6 log reduction) versus uncoated controls (p = 0.005). Only the CHX-M/R coated PICC showed zero biofilm colonization of MRSA, P. aeruginosa, C. albicans, and C. glabrata (p = 0.003) in comparison with the uncoated control PICCs. The M/R and CHX PICCS showed one-log reduction against PA, and 2-log reductions against CA, and CG. Conclusion: The novel CHX-M/R coated PICC was most effective in completely inhibiting biofilm formation of MRSA, PA, CA and CG in an in vitro biofilm colonization model. Further in vivo and clinical testing is warranted.
    Infectious Diseases Society of America 2011 Annual Meeting; 10/2011
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    ABSTRACT: Central venous catheters, often needed by cancer patients, can be the source of Nocardia bacteremia. We evaluated the clinical characteristics and outcomes of 17 cancer patients with Nocardia bacteremia. For 10 patients, the bacteremia was associated with the catheter; for the other 7, it was a disseminated infection. N. nova complex was the leading cause of bacteremia. Nocardia promoted heavy biofilm formation on the surface of central venous catheter segments tested in an in vitro biofilm model. Trimethoprim- and minocycline-based lock solutions had potent in vitro activity against biofilm growth. Patients with Nocardia central venous catheter-associated bloodstream infections responded well to catheter removal and antimicrobial drug therapy, whereas those with disseminated bacteremia had poor prognoses.
    Emerging Infectious Diseases 09/2011; 17(9):1651-8. · 6.79 Impact Factor
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    ABSTRACT: Under normal conditions, the expression of CD14, which is the principal receptor for bacterial lipopolysaccharide, is down-regulated in the intestinal mucosa but increases in response to inflammatory stimuli. The aim of the present study was to investigate whether fecal CD14 levels increased in response to infection with diarrheagenic Escherichia coli and whether single nucleotide polymorphisms (SNPs) in the CD14 gene were associated with an increased susceptibility to traveler's diarrhea (TD) in US visitors to Mexico. Six SNPs located at the promoter, exon, and untranslated regions of CD14 were typed in a prospective cohort study of 1360 visitors to Mexico at risk for TD. Stools from visitors with TD were studied for enteric pathogens by culture, colony hybridization, and polymerase chain reaction. Fecal soluble CD14 (sCD14) was measured in a subgroup of 203 adults with diarrhea and 66 healthy controls by enzyme-linked immunosorbent assay. The minor allele frequencies for CD14 SNPs were significantly different among the various racial and ethnic groups studied. Two SNPs in the promoter region of CD14 (-159 C > T; rs2569190 and -4191 C > T; rs5744441) were found to be associated with TD in White visitors. The -159 TT genotype was associated with a higher risk for TD (Relative risk [RR], 1.21; 95% confidence interval [CI], 1.05-1.38; P = .008), whereas individuals with the -4191 TT genotype were protected from infection (RR, 0.82; 95% CI, 0.71-0.92; P = .006). Subjects with TD excreted higher levels of fecal CD14 than did healthy controls (33,480 pg/mL vs 6178 pg/mL; P < .02). Fecal sCD14 levels were higher in stool samples from visitors with TD and the -159 TT genotype than they were in visitors with the CC/CT genotypes (P = .02), and stool samples from subjects with the -4191 CC genotype had higher fecal sCD14 levels than did stool samples from visitors with the CT/TT (P = .005) genotype. In a multivariate analysis with haplotypes constructed with the 6 SNPs studied, subjects with the haplotype containing the -159 C and the -4191 T allele were less likely to acquire TD (P = .015). Our study suggests that CD14 levels increase in response to bacterial diarrhea and that polymorphisms in the CD14 gene influence susceptibility to TD. Intestinal CD14 plays an important role in the innate immune response to enteric pathogens.
    Clinical Infectious Diseases 06/2011; 52(11):1332-41. · 9.37 Impact Factor
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    ABSTRACT: Ventilator-associated pneumonia (VAP) continues to be the nosocomial infection associated with the highest mortality in critically ill patients. Since silver-coated endotracheal tubes (ETT) was shown in a multicenter prospective randomized trials to decrease the risk of VAP, we compared the efficacy of two antiseptic agents such as gardine- and gendine-coated ETTs with that of silver-coated ETTs in preventing biofilm. The ETTs were tested for their ability to prevent the biofilm formation of methicillin-resistant Staphylococcus aureus (MRSA), Pseudomonas aeruginosa, Acinetobacter baumannii, Klebsiella pneumoniae, Enterobacter cloacae, and Candida albicans. Scanning electron microscopy studies revealed a heavy biofilm on uncoated and silver-coated ETT but not on the gardine-coated ETT. The gardine and gendine ETTs completely inhibited the formation of biofilms by all organisms tested and were more effective in preventing biofilm growth than the silver ETTs (p < 0.001). The gardine- and gendine-coated ETTs were more durable against MRSA than either the silver-coated or uncoated ETTs for up to 2 weeks (p < 0.0001). We have therefore shown that gardine- and gendine-coated ETTs are superior to silver-coated ETTs in preventing biofilm. Future animal and clinical studies are warranted to determine whether the gardine- and gendine-coated ETTs can significantly reduce the risk of VAP.
    Biomaterials 04/2011; 32(11):2689-94. · 8.31 Impact Factor
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    ABSTRACT: Up to 60% of the US visitors to Mexico develop travelers' diarrhea (TD). In Mexico, rates of diarrhea have been associated with the rainy season and increase in ambient temperature. However, the seasonality of the various diarrheagenic Escherichia coli pathotypes in travelers has not been well described. A study was undertaken to determine if ambient temperature and rainfall have an impact on the acquisition of TD due to different diarrheagenic E coli pathotypes in Mexico. We conducted a cohort study of the US adult students traveling to Cuernavaca, Mexico, who were followed during their stay and provided a stool sample with the onset of TD. The presence of E coli was analyzed by a direct fecal multiplex polymerase chain reaction for common E coli pathotypes including enterotoxigenic, enteropathogenic, enteroinvasive, shiga toxin-producing, and enteroaggregative E coli (ETEC, EPEC, EIEC, STEC, and EAEC respectively). The presence of pathotypes was correlated with daily rainfall, average, maximum, and minimum temperatures. A total of 515 adults were enrolled from January 2006 to February 2007. The weekly attack rate of TD for newly arrived travelers was lower in the winter months (range 6.8%-16.3%) than in summer months (range 11.5%-25%; p = 0.05). The rate of ETEC infection increased by 7% for each degree centigrade increase in weekly ambient temperature (p = 0.003). In contrast, EPEC and EAEC were identified in similar proportions during the winter and summer seasons. Temperature variations in central Mexico influenced the rate of ETEC but not EAEC-associated diarrhea in the US visitors. This epidemiological finding could influence seasonal recommendations for the use of ETEC vaccines in Mexico.
    Journal of Travel Medicine 03/2011; 18(2):121-5. · 1.68 Impact Factor
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    ABSTRACT: Campylobacter jejuni is an unusual cause of travelers' diarrhea acquired in Mexico, but previous studies have relied only on stool culture for diagnosis. We conducted a cohort study to determine if antibody seroconversion to C jejuni would better reflect the occurrence of infection acquired in Mexico. Serum IgG, IgA, and IgM antibodies to Campylobacter seroconverted in only 2 of 353 participants (0.6%). These data further support that C jejuni infection is an unusual cause of travelers' diarrhea in US visitors to Mexico.
    Journal of Travel Medicine 01/2011; 18(1):56-8. · 1.68 Impact Factor
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    ABSTRACT: Background: Enteroaggregative Escherichia coli (EAEC) are a common bacterial pathogen isolated in patients suffering from infectious diarrhea in developed and developing countries. Dispersin, a 10.2 kDa protein encoded by aap, is a well defined putative virulence factor and has previously only been described in EAEC. We have observed that up to 25% of diarrheagenic non-EAEC strains harbor the app gene and that some individuals suffering from diarrhea due to non-EAEC strains may develop anti-dispersin antibodies during convalescence. Objective: To demonstrate the presence and expression of dispersin in non-EAEC strains. Methods: Previously characterized non-EAEC strains collected from adult travelers suffering from diarrhea in a larger epidemiological cohort study in Mexico were studied. Twelve non-EAEC strains harboring the aap, but not aggR or aatA, genes were tested for bioflm formation, IL-8 induction, and expression of dispersin by reverse transcriptase polymerase chain reaction (RT-PCR). Results: One non-EAEC (7248-C) strain harboring the aap and Stx1 genes expressed dispersin by RT-PCR when cultured in arabinose enriched media. None of the other eleven strains expressed dispersin by RT-PCR. Nine of the twelve tested strains, including 7248-C, elicited an increased IL-8 response of co-cultured intestinal HCT-8 cells. None of the twelve tested strains produced biofilm by the microtiter plate assay with the crystal violet staining method. Conclusions: We provide evidence that a putative EAEC virulence factor can be produced by E. coli isolated from patients with diarrhea that otherwise would not be classified as diarrheagenic E. coli. It is unknown if the expression of dispersin confers disease causing virulence to non-EAEC strains or if the transcription of aap occurs when other neighboring plasmid genes are expressed.
    Infectious Diseases Society of America 2009 Annual Meeting; 10/2009
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    ABSTRACT: Background: Travelers’ diarrhea (TD) is the most common illness in adults from developed countries visiting developing nations. The majority of infections are due to enterotoxigenic E. coli (ETEC) and enteroaggregative E. coli (EAEC). Objective: To investigate the incidence of the different diarrheagenic pathotypes of E. coli among travelers in Mexico developing diarrhea. Methods: We conducted a prospective cohort study in US students traveling to Cuernavaca, Mexico during 2004 to 2007. The participants were followed for the development of acute diarrhea and a stool specimen was collected for microbiological analysis. Five individual E. coli-like colonies from each clinical specimen were characterized for adherence by the HEp2 assay and for the presence of Enteroinvasive E. coli (EIEC) ipaH,ETEC(lt, st), EPEC (eaeA, bfpA), STEC (stx1, stx2), and EAEC (aap, aatA, and aggR) by colony and direct stool multiplexed PCR. Results: We studied 953 subjects (74.3% female, mean age = 34 yr.) traveling for mean of three weeks 72.7% (693) visited Mexico during the summer months. Three hundred and eighty seven (40.7%) travelers developed diarrhea while in Mexico and 284 (73.4%) provided a stool specimen for microbiological examination. Fecal or colony PCR identified EAEC in 93 (35.2%) subjects, ETEC in 77 (29.2%), EPEC in 65 (24.6%) 4/65 strains were defined as typical EPEC (eae+,bfp+) and 61/65 were atypical (eae+,bfp-, EIEC was found in 15 (5.7%) and 33 (12.5%) subjects had STEC. Conclusions: Clinically, diarrhea due to EPEC, EIEC and STEC was indistinguishable from diarrhea due to ETEC and EAEC. EPEC and STEC warrant additional study as causal agents of TD in US adult travelers to Mexico.
    Infectious Diseases Society of America 2009 Annual Meeting; 10/2009
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    ABSTRACT: Osteoprotegerin (OPG), an immunoregulatory member of the TNF receptor superfamily, is expressed in inflamed intestinal mucosa. We investigated whether OPG is produced by intestinal epithelial cells and tested the hypothesis that single-nucleotide polymorphisms (SNPs) in the gene encoding OPG (TNFRSF11B) are associated with traveler's diarrhea (TD) among North American travelers to Mexico. OPG concentration was measured in the supernatants of T84 cells infected with various diarrheagenic Escherichia coli pathotypes. Genotyping was performed for 4 SNPs in the OPG gene for 968 North American travelers with or without TD. Stool samples from travelers with TD were evaluated for the presence of enteric pathogens. T84 cells produced higher OPG levels in response to infection with various diarrheagenic E. coli pathotypes than with E. coli controls (P<.05). A SNP in the exon 1 region of the OPG gene (OPG+1181G>C) was associated with TD in white travelers who stayed in Mexico for >1 week during the summer (P=.009) and for TD due to nonsecretory pathogens (P=.001). Our study suggests that OPG is secreted by intestinal epithelial cells in response to enteropathogens and that a polymorphism in the OPG gene is associated with an increased susceptibility to TD.
    The Journal of Infectious Diseases 01/2009; 199(4):477-85. · 5.85 Impact Factor
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    ABSTRACT: Background: The human intestinal mucosa has the ability to tolerate commensal organisms and respond to enteric pathogens when needed. We hypothesized that the balance between colonization and symptomatic infection with enteropathogens partially depends on host genetic factors and that single nucleotide polymorphisms (SNPs) in genes coding for these molecules would correlate with susceptibility to travelers’ diarrhea (TD). Methods: We studied the impact of 28 SNPs in 17 genes, potentially involved in susceptibility, injury and control of enteropathogens, in 1,915 US travelers to Mexico at risk for TD. Analysis was limited to SNPs in Harding-Weinberg equilibrium, with minor allele frequencies of >5%, and with ≥300 participants with genotypes available for analysis. Results: SNPs in 6 genes showed an association with susceptibility to TD due to all causes. SNPs in four genes were involved in LPS response and signaling (CD14, TLR4, Lactoferrin, CARD 15), one in inflammatory response (IL-6) and one in anti-inflammatory response (osteoprotegerin). In contrast, genes not associated with TD due to all causes included SNPs in collectins (MBL, Surfactant D), pathogen receptors (CD55, CFTR, FUT-2, Guanylate Cyclase, and TLR5), pro-inflammatory cytokines (TNFα, IL-1, IL-6 and IL-8) and anti-inflammatory cytokines (IL-10). Conclusions: These data suggest that SNPs in host molecules involved in LPS response and signaling are important determinants of susceptibility to TD. The innate immune response to LPS may be a stereotypical reaction to infection with various Gram negative enteropathogens. The study of SNP associations with specific agents of diarrhea is ongoing.
    Infectious Diseases Society of America 2008 Annual Meeting; 10/2008
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    ABSTRACT: Background: Travelers’ diarrhea (TD) affects 40-60% of US adult visitors to Mexico and is due to enterotoxigenic E. coli (ETEC), enteroaggregative E. coli (EAEC) and other bacterial, viral and protozoan enteropathogens. Shiga toxin-producing E. coli (STEC) has been previously identified in a small percentage of cases. We sought to determine the incidence and clinical features of STEC-associated TD in US travelers to Mexico. Methods: US students (n=327) in Mexico with TD from 2004-2008 were examined for enteropathogens, fecal leukocytes and occult blood. E. coli colonies were tested by PCR for STEC (stx1 and stx2), EAEC, ETEC, enteroinvasive E. coli, and enteropathogenic E. coli genes. Stools (n=88) were studied for the presence of Shiga toxin by ELISA. Fecal excretion patterns of 21 cytokines in cases with STEC were compared to pathogen-negative cases. Results: Of 327 fecal samples, 51 (16%) were positive by PCR for stx1 or stx2 genes. Shigella spp. was found in only one specimen. Eight (11%) of 75 specimens tested by ELISA showed the presence of Shiga toxin. Of the 75 ELISA-tested specimens, Shiga toxin was found in 6 of 42 specimens that were PCR-positive for stx1 or stx2. Only 1 of the STEC PCR-positive and none of the STEC ELISA-positive fecal specimens contained WBCs, blood, or mucus. In subjects with STEC identified in stools, fecal cytokine levels did not differ from those measured in stools in which a pathogen was not identified. Conclusions: STEC is more commonly associated with travelers’ diarrhea than historically believed with the majority of cases showing non-inflammatory diarrhea. The clinical features and epidemiology of STEC infection acquired during travel differs from the STEC cases reported domestically.
    Infectious Diseases Society of America 2008 Annual Meeting; 10/2008
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    ABSTRACT: Background: Seasonal changes in infectious diarrhea incidence have been described; however seasonality of diarrhea due to different diarrheagenic E. coli has not been described. Methods: We conducted a prospective study to determine if temperature and rainfall change have an impact on travelers’ diarrhea (TD) due to the different diarrheagenic E. coli. US travelers to Mexico were followed during their stay in Mexico for TD and provided a stool sample with diarrhea for microbiological analysis; different diarrheagenic E. coli were determined by multiplex PCR. Results: Adult travelers (n=1,101) to Cuernavaca, Mexico were followed between January 2006 and February 2008. The weekly TD attack rate during winter ranged between 6.8-12.5% while during the summer it ranged between 8.2-38%. Local temperature ranged from 9.5 to 35.5 °C throughout the year. Increase in weekly average temperature statistically correlated with increased frequency of TD (R2=0.18, P=0.01). There was a linear increase in ETEC attack rates during warmer weeks with the odds of developing ETEC TD increasing 22% per every degree increment in the average week temperature (P=0.004). In contrast, the attack rate of EAEC TD remained constant throughout the study (R2=0.074, P=0.1). STEC and EPEC TD showed a non significant trend (27% p=0.1 and 29% P=0.08). There were too few cases of EIEC. There was a negative trend between rainfall and occurrence of TD (-0.21, P=0.2). Conclusions: Temperature variations influenced the occurrence of TD due to ETEC, while EAEC attack rates remained stable during seasonal variations. This epidemiological finding could impact the use and timing of administration of ETEC vaccines.
    Infectious Diseases Society of America 2008 Annual Meeting; 10/2008
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    ABSTRACT: Background: Enteroaggregative Escherichia coli (EAEC) are an important cause of diarrhea in travelers to developing regions of the world. EAEC exhibits an aggregative, stacked-bricked pattern of adherence to HEp-2 epithelial cells. Dispersin is an anti-aggregative protein (encoded by aap) previously only described in EAEC. Objectives: To determine the frequency of aap in E. coli isolates from US adult travelers to Mexico with diarrhea and its relationship to other diarrheagenic E. coli. Methods: We analyzed 512 strains from US travelers to Mexico with diarrhea for the presence of aap by PCR. Isolates were also studied for the presence of the genes aatA, aggR for EAEC, ipaH for enteroinvasive E. coli (EIEC), lt, st for enterotoxigenic E. coli (ETEC), eaeA, bfpA for enteropathogenic E. coli (EPEC), and stx1, stx2 for Shiga toxin producing E. coli (STEC). Results: Twenty five percent (127/512) of tested isolates carried aap. In 62 isolates (49%) aap was the only gene found. Dispersin by PCR was found in 51 of 61 (83%) EAEC, 2 of 5 (40%) EIEC, 5 of 40 (12%) ETEC, 0 of 17 EPEC , 14 of 30 (46%) STEC and in 3 of 5 (60%) of isolates with unconventional combinations. The presence of aap correlated strongly with EAEC (p<.0001). Conclusions: The gene for the antiaggregative protein dispersin is commonly found in E. coli from US travelers with diarrhea belonging to diverse pathotypes but appears to be more common in EAEC.
    Infectious Diseases Society of America 2008 Annual Meeting; 10/2008
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    ABSTRACT: We studied 1,179 North American travelers who visited Mexico from 2005 to 2007. Travelers' diarrhea (TD) was reported by 521 (44%) participants. Among subjects with TD, 218 cases were examined for cryptosporidiosis by polymerase chain reaction (PCR) and enzyme-linked immunoassays (ELISA). There were 14 (6%) cases of cryptosporidiosis and 141 cases (64%) of bacterial diarrhea. Compared with bacterial diarrhea, a longer stay in Mexico was a risk factor for cryptosporidiosis. Additionally, Cryptosporidium cases passed greater number of watery stools (P < 0.05), suffered more episodes of diarrhea (P < or = 0.05), and were more likely to experience tenesmus (P < or = 0.05) compared with bacterial causes of TD. ELISA detected seven (3%) cases of Cryptosporidium, whereas PCR identified an additional seven cases (6%). Speciation by 18SrRNA sequencing showed that 13 cases were caused by C. parvum and only 1 case was caused by C. hominis. ELISA showed a sensitivity of 50% and specificity of 100% compared with PCR.
    The American journal of tropical medicine and hygiene 08/2008; 79(2):210-4. · 2.53 Impact Factor
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    ABSTRACT: Up to 60% of U.S. visitors to Mexico develop traveler's diarrhea (TD), mostly due to enterotoxigenic Escherichia coli (ETEC) strains that produce heat-labile (LT) and/or heat-stable (ST) enterotoxins. Distinct single-nucleotide polymorphisms (SNPs) within the interleukin-10 (IL-10) promoter have been associated with high, intermediate, or low production of IL-10. We conducted a prospective study to investigate the association of SNPs in the IL-10 promoter and the occurrence of TD in ETEC LT-exposed travelers. Sera from U.S. travelers to Mexico collected on arrival and departure were studied for ETEC LT seroconversion by using cholera toxin as the antigen. Pyrosequencing was performed to genotype IL-10 SNPs. Stools from subjects who developed diarrhea were also studied for other enteropathogens. One hundred twenty-one of 569 (21.3%) travelers seroconverted to ETEC LT, and among them 75 (62%) developed diarrhea. Symptomatic seroconversion was more commonly seen in subjects who carried a genotype producing high levels of IL-10; it was seen in 83% of subjects with the GG genotype versus 54% of subjects with the AA genotype at IL-10 gene position -1082 (P, 0.02), in 71% of those with the CC genotype versus 33% of those with the TT genotype at position -819 (P, 0.005), and in 71% of those with the CC genotype versus 38% of those with the AA genotype at position -592 (P, 0.02). Travelers with the GCC haplotype were more likely to have symptomatic seroconversion than those with the ATA haplotype (71% versus 38%; P, 0.002). Travelers genetically predisposed to produce high levels of IL-10 were more likely to experience symptomatic ETEC TD.
    Clinical and vaccine Immunology: CVI 07/2008; 15(8):1194-8. · 2.60 Impact Factor
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    ABSTRACT: Large field studies of travelers' diarrhea for multiple destinations are limited by the need to perform stool cultures on site in a timely manner. A method for the collection, transport, and storage of fecal specimens that does not require immediate processing and refrigeration and that is stable for months would be advantageous. This study was designed to determine if enterotoxigenic Escherichia coli (ETEC) and enteroaggregative E. coli (EAEC) DNA could be identified from cards that were processed for the evaluation of fecal occult blood. U.S. students traveling to Mexico during 2005 to 2007 were monitored for the occurrence of diarrheal illness. When ill, students provided a stool specimen for culture and occult blood by the standard methods. Cards then were stored at room temperature prior to DNA extraction. Fecal PCR was performed to identify ETEC and EAEC in DNA extracted from stools and from occult blood cards. Significantly more EAEC cases were identified by PCR that was performed on DNA that was extracted from cards (49%) or from frozen feces (40%) than from culture methods that used HEp-2 adherence assays (13%) (P < 0.001). Similarly, more ETEC cases were detected from card DNA (38%) than from fecal DNA (30%) or by culture that was followed by hybridization (10%) (P < 0.001). The sensitivity and specificity of the card test were 75 and 62%, respectively, compared to those for EAEC by culture and were 50 and 63%, respectively, compared to those for ETEC. DNA extracted from fecal cards that was used for the detection of occult blood is of use in identifying diarrheagenic E. coli.
    Journal of clinical microbiology 07/2008; 46(7):2227-30. · 4.16 Impact Factor
  • Jamal A Mohamed, David B Huang
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    ABSTRACT: Enterococci are an important global cause of nosocomial infections, being increasingly associated with urinary tract infections, endocarditis, intra-abdominal and pelvic infections, catheter-related infections, surgical wound infections, and central nervous system infections. The two most common enterococci species are Enterococcus faecalis and Enterococcus faecium. Both are capable of producing biofilms, which consist of a population of cells attached irreversibly on various biotic and abiotic surfaces, encased in a hydrated matrix of exopolymeric substances. Many environmental and genetic factors are associated or have been proposed to be associated with the production of biofilm. This review discusses recent advances in knowledge about the biology and genetics of biofilm formation and the role of biofilms in enterococci pathogenesis.
    Journal of Medical Microbiology 01/2008; 56(Pt 12):1581-8. · 2.30 Impact Factor
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    ABSTRACT: Enterotoxigenic Escherichia coli (ETEC) is the most common bacterial pathogen isolated from travelers suffering of diarrhea. Exposure to heat-labile toxin (LT) produces a high rate of seroconversion. However, the role of LT-producing ETEC (LT-ETEC) as a cause of diarrhea is controversial. We conducted a cohort study in US students traveling to Mexico to assess the ETEC-LT seroconversion rate after natural exposure. Participants provided a serum sample on arrival and departure and a stool sample when ill. ETEC-LT immunoglobulin G antibodies were measured by enzyme-linked immunosorbent assay, and LT-ETEC were detected by means of polymerase chain reaction done on fecal DNA. A total of 422 participants with a mean age of 34.5 years were followed a mean of 19.9 days; 304 were females (72.0%), and 319 (75.6%) traveled during the summer months. In total, 177 individuals (41.9%) developed travelers' diarrhea and 33.9% had LT-ETEC identified in their stools. Among individuals having an LT-ETEC strain, 74% seroconverted compared to 11% of those not having diarrhea (p < 0.0001). When analyzed with a logistic regression model, the odds of seroconversion were significantly reduced in participants not having LT-ETEC in their stool (odds ratio = 0.1, p < 0.0001) after adjusting for season, length of stay, age, gender, race, and ethnicity. In US young adults traveling to Mexico, ETEC-LT seroconversion reliably identifies individuals naturally exposed to ETEC and correlates with symptomatic illness, length and season of travel.
    Journal of Travel Medicine 01/2008; 15(3):156-61. · 1.68 Impact Factor
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    ABSTRACT: Background: Osteoprotegerin (OPG), an immunoregulatory glycoprotein belonging to the TNF receptor super family, is expressed in various tissues including the intestinal mucosa. We tested the hypothesis of whether OPG SNPs are associated with an increased risk of travelers’ diarrhea (TD) among North American visitors to Mexico. Methods: Four SNPs located at the promoter, exon and intron regions of OPG gene were genotyped by oligonucleotide ligation/PCR based SNPlex genotyping method (Applied Biosystems Inc.,) with DNA samples extracted from 968 US visitors to Mexico with and without TD. Stools from subjects with TD were evaluated for the presence of enteropathogens, and inflammatory makers (WBCs, RBCs, and mucus). Results: Among the 4 SNPs studied, a SNP in the exon1 region (G1181C; Lys→Asn) was associated with TD (P = 0.001). Among the 872 Caucasians, an increased risk of diarrhea was observed for the individuals with CC genotype compared to CG and GG genotypes (P = 0.001); the frequencies for the CC, CG and GG genotypes were 41%, 56% and 50% on healthy controls versus 59%, 44% and 50% on TD cases respectively (P = 0.001). When compared with healthy travelers and after adjusting for race, season of travel and length of stay, Caucasians who stayed more than 7 days during summer with the CC genotype were more likely to experience TD (60% vs. 40%; P = 0.009) due to bacterial pathogens (P = 0.0002) or with markers of inflammation (P = 0.006). Conclusion: Our study suggests that North American Caucasian travelers with the OPG G1181C CC genotype are susceptible to TD and suggests that OPG plays an important role in host response to gastrointestinal infections. The effect of this polymorphism is similar to the effect of polymorphisms in other genes such as IL-8 and lactoferrin.
    Infectious Diseases Society of America 2007 Annual Meeting; 10/2007

Publication Stats

434 Citations
83.56 Total Impact Points

Institutions

  • 2004–2011
    • University of Texas Medical School
      • Division of Infectious Diseases
      Houston, Texas, United States
  • 2007–2009
    • Baylor College of Medicine
      • Section of Infectious Diseases
      Houston, TX, United States
  • 2007–2008
    • University of Texas Health Science Center at Houston
      • Center for Infectious Diseases
      Houston, TX, United States
  • 2006–2008
    • University of Houston
      Houston, Texas, United States