Biomedical subjects

Robert W Frenck

Publications and source records attributed to Robert W Frenck.

At least 19 recordsLinked to original sources

PubMed2006

Sensitivity and specificity of various tests for the diagnosis of Helicobacter pylori in Egyptian children.

OBJECTIVES: Many noninvasive methods (using breath, blood, and stool samples) are available to diagnose Helicobacter pylori. However, because the noninvasive tests are proxy measures of the infection, they need validation before use. Factors that may affect test validity include patient age, gender, and geographic location. Because no data were available on the validation of noninvasive tests for the diagnosis of H. pylori among children in the Middle East, this study was performed. METHODS: Children between 2 and 17 years of age evaluated at the Cairo University School of Medicine pediatric gastroenterology clinic who were already scheduled for upper endoscopy were eligible for enrollment in the study. At the time of endoscopy, 3 biopsies were collected and used for rapid urease, histology, and culture, respectively. All children also donated a sample of stool and blood and had a urea breath test performed. Stool and serum samples were tested for the presence of H. pylori by using commercially available enzyme-linked immunosorbent assay-based technology. The sensitivity, specificity, and positive and negative predictive values were calculated for each noninvasive test used in the study. Receiver operating curves also were charted to determine optimal cut points for the various tests when used in the current study cohort. RESULTS: One hundred eight children were enrolled in the study, with 52 children being under 6 years of age. The urea breath test and HpStar (DakoCytomation, Norden, Denmark) stool enzyme-linked immunosorbent assay kit had the highest sensitivity and specificity (sensitivity and specificity: 98 and 89 [urea breath test] and 94 and 81 [HpStar], respectively), whereas the serologic kit had an unacceptably low sensitivity (50%). The sensitivity of neither the urea breath test nor the HpStar tests was affected by subject age, but specificity of the HpStar test, although still high, was significantly lower among children under 6 years. Receiver operating curves found optimal cut points of the urea breath test at 6.2 delta over baseline and of the HpStar at 0.25 enzyme-linked immunosorbent assay units. CONCLUSION: The urea breath test and HpSTAR stool antigen kit are reliable tests for the noninvasive diagnosis of H. pylori among children living in the Middle East.

Adolescent↗

PubMed2006

Patients with inflammatory bowel disease are at risk for vaccine-preventable illnesses.

BACKGROUND: Patients with chronic, immune-mediated conditions such as inflammatory bowel disease (IBD) are often treated with long-term immunosuppressive therapies, potentially increasing their risk of developing an infection. Empiric data suggest that vaccines are underutilized in immunocompromised patients, despite published guidelines recommending their use. We aimed to assess exposure risk and immunization status among patients receiving care in an IBD specialty clinic. METHODS: Patients completed a self-administered, pretested, structured questionnaire during a routine visit for the management of IBD. Survey questions related to medical and immunization histories, and exposures to known risk factors for influenza, pneumococcus, viral hepatitis, and varicella. Additionally, in a subgroup of patients who agreed to donate a sample of blood, immune status to hepatitis A (HAV), hepatitis B (HBV), and varicella was determined. RESULTS: Two hundred four patients were asked to participate in the study; 169 completed surveys and comprised the study population. Mean age was 35 yr (range 13-75 yr). One hundred forty-six respondents (86%) reported current or prior use of immunosuppressive medications. Only 45% of respondents recalled tetanus immunization within the past 10 yr, 41 (28%) reported regularly receiving flu shots, and 13 (9%) reported having received pneumococcal vaccine. The most common reasons for nonimmunization with influenza included lack of awareness (49%) and concern for side effects (18%). Responses indicated that 75 (44%) patients were at risk for HBV but only 47 (28%) had been vaccinated against the infection; of patients with previous HBV vaccination, only three of nine (33%) had measurable antibodies against hepatitis B surface antigen. CONCLUSIONS: Immunization against selected vaccine-preventable illnesses was uncommon in patients with IBD, despite the presence of significant risk factors. Efforts to improve immunization status among patients with IBD and other chronic, immune-mediated conditions are needed.

Adolescent↗

PubMed2006

Enteric pathogens associated with diarrhea in children in Fayoum, Egypt.

In a cross-sectional study of children <60 months old from Fayoum, Egypt, presenting with diarrhea, 46% (162/356) had detectable enteric pathogens. Bacterial pathogens were identified in 25% (89/356), whereas rotavirus and Cryptosporidium were detected in 21% (54/253) and 15% (39/253), respectively. Cryptosporidium is an important pathogen in this region.

Chi-Square Distribution↗

PubMed2006

Enterotoxigenic Escherichia coli colonization factor types collected from 1997 to 2001 in US military personnel during operation Bright Star in northern Egypt.

Operation Bright Star (OBS) is a biennial, multinational exercise in Egypt involving 15000 US troops. Consistent with past observations in deployed troops, diarrhea is the most significant cause of morbidity. Focused efforts are ongoing to develop vaccines against the most common pathogens affecting our troops. As part of these efforts, diarrhea surveillance was conducted during OBS to monitor pathogens associated with illness and to identify new vaccine targets. A retrospective review was conducted of prior studies with similar methods. Soldiers with diarrhea presenting to the OBS clinic provided a stool sample that was inoculated into Carey-Blair transport media. Within 3 days, the Cary-Blair tubes were transported to the Naval Medical Research Unit no. 3 in Cairo where bacterial culture was performed. As part of the evaluation, 5 Escherichia coli-like colonies were collected and tested for toxin production using the GM1-ELISA. Toxin-positive isolates were further tested for colonization factors (CF) by a dot-blot assay using a standardized panel of monoclonal antibodies against CFA/I, CS1-CS7, CS17, CS8 (CFA/III), CS12 (PCFO159), and CS14 (PCFO166). Enterotoxigenic E. coli (ETEC) was the most frequently isolated pathogen during each OBS from which data were collected. The rate of ETEC-associated diarrhea ranged from 22% to 58%. Over time, there were dramatic shifts in the frequency and distribution of CFs. Over the 5 years of study, an increasing number of ETEC isolates had no known CF identified, and in 2001, only 40% of ETEC was associated with known CFs. The most commonly identified CF was CS6. Diarrheal disease, particularly ETEC, continues to be a common malady among US military personnel deployed to Egypt. We have identified ETEC CF types, especially CS6, which should be considered potential vaccine candidates. However, despite intensive testing, CFs could not be identified in most of the ETEC isolated, highlighting the need for further studies to identify novel CFs and alternative vaccine targets.

Antibodies, Monoclonal↗

PubMed2006

Incidence, etiology, and impact of diarrhea among deployed US military personnel in support of Operation Iraqi Freedom and Operation Enduring Freedom.

A health assessment survey was collected from US military personnel deployed to the Middle East taking part in the "Rest and Recuperation" program or on temporary assignment to Camp As Sayliyah Doha, Qatar, from January to December 2004. In addition, a concurrent clinic-based observational study was conducted to determine pathogen etiology and potential risk factors. From 28,322 health assessment surveys, overall self-reported incidence of diarrhea was 4.9 cases per 100 person-months. Disease incidence increased with rank and was higher in Iraq compared with Afghanistan. During this period, 109 US military personnel with acute diarrhea and 85 asymptomatic personnel were enrolled in the observational study. Enterotoxigenic E. coli (ETEC) was the predominant pathogen (32%), followed by enteroaggregative E. coli (12%) and Salmonella spp. (6%). These data are consistent with previous reports implicating ETEC as the primary cause of acute diarrhea for military personnel deployed to this region.

Adult↗

PubMed2005

The changing epidemiology of meningococcal meningitis after introduction of bivalent A/C polysaccharide vaccine into school-based vaccination programs in Egypt.

BACKGROUND: The strategy recommended by the World Health Organization (WHO) to curtail outbreaks of meningococcus in Africa is enhanced surveillance with administration of oily chloramphenicol as well as vaccination when incidence thresholds are exceeded. The role of capsular polysaccharide meningococcal vaccine in outbreak prevention has been the subject of considerable debate. The Egyptian Ministry of Health and Population initiated a school-based vaccination program with bivalent A/C capsular polysaccharide vaccine in 1992. This investigation reviews data on meningococcal meningitis in Egypt comparing years before and after introduction of the vaccine. METHODS: This is a retrospective review of several sources to examine the rates and serogroups of meningococcal meningitis before and after the introduction of the meningococcal A/C vaccine in Egypt. FINDINGS: Between 1967 and 1991, outbreaks of meningococcal disease were documented with a periodicity of 8 years in Egypt. However, there has not been an outbreak since 1991 and over the same period, there has also been a progressive decline in the baseline incidence of meningococcus. Also, a shift from a serogroup A to serogroup B predominance in meningococcal disease was noted during the study period. These data suggest that there has been an alteration in the epidemiology of meningococcal disease in Egypt that coincided with the implementation of the school-based vaccination program. INTERPRETATION: Routine use of the bivalent A/C meningococcal vaccine may be an alternative for the control and prevention of meningococcal disease in high-risk areas including the "meningitis belt".

Egypt↗

PubMed2005

Serologic correlates of protection against enterotoxigenic Escherichia coli diarrhea.

BACKGROUND: We conducted a nested case-control study in 397 rural Egyptian children <36 months of age to assess the correlation between serum levels of antibodies against toxin and colonization factors (CFs) and the risk of homologous enterotoxigenic Escherichia coli (ETEC) diarrhea. METHODS: Active case detection was performed via semiweekly home visits, and blood was obtained at 3-month intervals. After each serosurvey, case subjects were selected from children experiencing a CF antigen (CFA)/I-, CFA/II-, CFA/IV-, or heat-labile enterotoxin (LT)-ETEC diarrheal episode during the subsequent 3 months. Up to 5 control subjects per case subject were selected from children who did not experience an ETEC diarrheal episode during the corresponding interval. Serum titers of immunoglobulin G antibodies against CFA/I, coli surface antigen (CS) 3, CS6, and LT were measured by enzyme-linked immunosorbant assay. RESULTS: The distribution of serum titers of LT, CS3, and CS6 antibodies did not differ between the case and control subjects. For children <18 months of age, serum titers of CFA/I antibody were inversely related to the risk of CFA/I-ETEC diarrhea; reciprocal serum titers of CFA/I antibody > or =76 were associated with a 77% reduction in the odds of CFA/I-ETEC diarrhea. CONCLUSION: Induction of reciprocal serum titers of antibodies against CFA/I within or above the 76-186 range should be further evaluated as a predictor for assessment of the ability of candidate vaccines to protect against CFA/I-ETEC diarrhea.

Antibodies, Bacterial↗

PubMed2005

Diarrheal illness among deployed U.S. military personnel during Operation Bright Star 2001--Egypt.

In the fall of 2001, approximately 15,000 U.S. military personnel participated in a military exercise in the northwestern Egyptian desert. To assess the prevalence and impact of diarrhea and enteropathogen distribution, we conducted a post-deployment survey and a case series study. A departure convenience sampling (n = 3725) was used in the post-deployment survey. Overall, 9.3% reported diarrhea, 2.6% sought medical care, and 2.8% stopped or decreased their work for at least a day. Among those reporting diarrhea, 41.7% had symptoms for less than 2 days, 43.5% had symptoms from 2-5 days, and 14.8% had symptoms for more than 5 days. In the case series study, pathogens were identified in 53.6% of the 129 cases enrolled. Pathogens identified included enterotoxigenic E. coli (n = 53), enteroaggregative E. coli (n = 13), Cryptosporidium (n = 9), Campylobacter jejuni (n = 7), noroviruses (n = 7), Shigella flexneri (n = 2), rotavirus (n = 2), and Entamoeba histolytica (n = 2). Among those seeking care for diarrhea, two thirds reported a decreased ability or inability to perform their jobs for at least one day, but overall, diarrhea was much less prevalent than in past surveys in this region, with minimal impact on the mission.

Adult↗

PubMed2005

Posttreatment changes in Escherichia coli antimicrobial susceptibility rates among diarrheic patients treated with ciprofloxacin.

Changes in antimicrobial resistance of Escherichia coli among deployed U.S. military personnel being treated for diarrhea were evaluated. Stool samples were collected pretreatment and on days 7, 14, and 28 posttreatment. Resistance to ciprofloxacin was noted in 13.3% of baseline specimens, and rates of resistance against multiple antibiotics increased dramatically from baseline to day 7 and then tapered off to return to pretreatment levels by day 28, except for ciprofloxacin, suggesting that population accumulative usage of fluoroquinolones may result in an incremental increase in resistance rates.

Adult↗

PubMed2005

Relationship between intracranial granulomas and cerebrospinal fluid levels of gamma interferon and interleukin-10 in patients with tuberculous meningitis.

Cerebrospinal fluid gamma interferon (IFN-gamma) and interleukin-10 levels in 39 patients with tuberculous meningitis were serially measured. Cytokine levels did not predict intracranial granuloma (IG) development, but IFN-gamma levels in the top quartile after 1 month of therapy were highly associated (odds ratio = 18) with detection of an IG by computed tomography scanning.

Adolescent↗

PubMed2005

Knowledge, attitudes, and practices regarding epidemiology and management of travelers' diarrhea: a survey of front-line providers in Iraq and Afghanistan.

To evaluate the relationship between medical knowledge and clinical practice, a survey on travelers' diarrhea was administered to military health care providers attending a professional development and trauma management conference. The survey was administered at the beginning of the conference and 58 of the 76 attendees participated by completing a questionnaire. Respondents were aware of the standard definition of travelers' diarrhea; however, their knowledge about the epidemiology and management of travelers' diarrhea was low. Less than one-third correctly answered questions on etiology and more than two-thirds made incorrect management choices in treatment of mild to moderate watery diarrhea and dysentery. Important knowledge gaps about gastroenteritis were identified and should serve as a basis to develop military-specific clinical guidelines and training programs.

Afghanistan↗

PubMed2005

Impact of illness and non-combat injury during Operations Iraqi Freedom and Enduring Freedom (Afghanistan).

Historically, non-combat injuries and illnesses have had a significant impact on military missions. We conducted an anonymous cross-sectional survey to assess the prevalence and impact of common ailments among U.S. military personnel deployed to Iraq or Afghanistan during 2003-2004. Among 15,459 persons surveyed, diarrhea (76.8% in Iraq and 54.4% in Afghanistan), respiratory illness (69.1%), non-combat injuries (34.7%), and leishmaniasis (2.1%) were commonly reported. For all causes, 25.2% reported that they required intravenous fluids, 10.4% required hospitalization, and 5.2% required medical evacuation. Among ground units, 12.7% reported that they missed a patrol because of illness, and among air units, 11.7% were grounded because of illness. The incidence of diarrhea and respiratory infections doubled from the pre-combat to combat phases, and the perceived adverse impact of these illnesses on the unit increased significantly during the combat phase. Despite technologic advances in warfare and preventive medicine, illness and non-combat injuries have been common during operations in Iraq and Afghanistan, resulting in frequent transient decreases in operational efficiency.

Afghanistan↗

PubMed2004

Short-course azithromycin for the treatment of uncomplicated typhoid fever in children and adolescents.

We studied 149 children and adolescents 3-17 years of age with clinical typhoid fever who were treated with either oral azithromycin (20 mg/kg per day; maximum dose, 1000 mg/day) or intravenous ceftriaxone (75 mg/day; maximum dose, 2.5 g/day) daily for 5 days. Blood and stool specimens were obtained for culture before the initiation of therapy and were repeated on days 4 and 8 of treatment. Isolation of Salmonella enterica serovar Typhi or S. enterica serovar Paratyphi from the initial culture was required for inclusion in the final analysis. S. Typhi was isolated from 68 patients, 32 of whom were receiving azithromycin. Cure was achieved in 30 (94%) of 32 patients in the azithromycin group and in 35 (97%) of 36 patients in the ceftriaxone group (P=NS). Mean time to clearance of bacteremia was longer in the azithromycin group than in the ceftriaxone group. No patient who received azithromycin had a relapse, compared with 6 patients who received ceftriaxone. A 5-day course of azithromycin was found to be an effective treatment for uncomplicated typhoid fever in children and adolescents.

Adolescent↗

PubMed2004

The epidemiology of self-reported diarrhea in operations Iraqi freedom and enduring freedom.

Diarrhea remains a potential cause of compromised military effectiveness. To assess diarrhea rates and mission impact in operations in Iraq and Afghanistan, a survey was administered to soldiers participating in the "Rest and Recuperation" program in Doha, Qatar. Between October and December 2003, 2,389 volunteers completed a questionnaire designed to assess the occurrence and impact of diarrhea. The median length of deployment was 7.2 months, 70% reported at least one episode, and 56% had multiple episodes of diarrhea. Overall, 43% reported decreased job performance for a median of 2 days, and 17% reported being on bed rest for a median of 2 days. While this survey showed high rates of diarrhea associated with decreased operational effectiveness, the results are consistent with prior military operations in this region. Further research is needed to develop better methods for illness prevention and its minimization on operational impact.

Adult↗

PubMed2004

Universal high-level primary metronidazole resistance in Helicobacter pylori isolated from children in Egypt.

Antimicrobial susceptibility testing was performed on 48 isolates of Helicobacter pylori recovered from Egyptian children undergoing routine endoscopies. The isolates were universally highly resistant to metronidazole, but resistance to other tested antimicrobial agents was rare (4% for clarithromycin, erythromycin, and azithromycin resistance versus 2% for ciprofloxacin and ampicillin resistance). Use of metronidazole for the treatment of H. pylori in Egypt should be avoided.

Adolescent↗

PubMed2004

Epidemiology of Shigella-associated diarrhea in rural Egyptian children.

During the period from February 1995 to February 1998, the epidemiology of Shigella diarrhea was studied among children less than three years of age residing in Egypt's Nile Delta. Children were visited twice a week and a stool sample was collected from any of them with diarrhea. The incidence of Shigella-associated diarrhea was 0.2 episodes/child-year, with S. flexneri being the most common serogroup isolated (55% of Shigella episodes). Younger age and the warm months increased the risk of developing Shigella-associated diarrhea, while breastfeeding was protective. Children with Shigella were ill for a mean of four days and passed a mean of six stools per day. Common symptoms included fever (35%), vomiting (19%), and dehydration (16%). Dysentery, however, was unusual, occurring in only 11% of the cases. In conclusion, Shigella-associated diarrhea remains relatively common in Egyptian children and supports the need for additional control measures including vaccine development.

Case-Control Studies↗

PubMed2003

Antimicrobial susceptibility trends in Campylobacter jejuni and Campylobacter coli isolated from a rural Egyptian pediatric population with diarrhea.

Comparative and trend analysis was conducted on annual prevalence of antimicrobial susceptibility among Campylobacter jejuni and Campylobacter coli recovered from rural Egyptian children from 1995 through 2000. C. jejuni and C. coli demonstrated significant decreasing trends in ciprofloxacin susceptibility over the study period (p < 0.001 for both). In general, C. coli demonstrated a higher degree of susceptibility than C. jejuni, however, there was no statistical difference (p = 0.2) comparing the linear trends over the duration of the study. There was no indication of frank macrolide (erythromycin or azithromycin) resistance among any Campylobacter. Moreover, there were statistically significant positive trends in both the MIC(50) and MIC(90) values for the erythromycin and azithromycin during the study period, suggesting a possible decreasing trend in susceptibility among Campylobacter. This study demonstrated that antimicrobial susceptibility in Campylobacter has significantly decreased from 1995 through 2000 among pediatric diarrhea cases in rural Egypt.

Anti-Bacterial Agents↗

PubMed2003

Helicobacter in the developing world.

Helicobacter pylori in the developing world is associated with many unique challenges not encountered in an industrialized setting. The 20% prevalence of infection with H. pylori among adolescents in the United States pales in comparison to infection rates exceeding 90% by 5 years of age in parts of the developing world. While H. pylori within the developed world is associated with gastritis, which may lead to peptic ulcer and gastric carcinoma, the infection in the developing world appears to also be linked with chronic diarrhea, malnutrition and growth faltering as well as predisposition to other enteric infections, including typhoid fever and cholera. Once identified, treatment of H. pylori within the developing world presents increased difficulties due to the frequency of antibiotic resistance as well as the frequency of recurrence after successful treatment. Control, and possibly eradication, of H. pylori could likely be achieved through increased standards of living and improved public health, as it has in the industrialized world. However, these measures are distant objectives for most developing countries, making long-term control of the organism dependent on the development and administration of an effective vaccine.

Adult↗