Study of enteric pathogens among children in the tropics and effects of prolonged storage of stool samples.

The study was performed to compare real-time PCR after nucleic acid extraction directly from stool samples as well as from samples stored and transported on Whatman papers or flocked swabs at ambient temperature in the tropics. In addition, the possible suitability for a clear determination of likely aetiological relevance of PCR-based pathogen detections based on cycle threshold (Ct) values was assessed. From 632 Tanzanian children <5 years of age with and without gastrointestinal symptoms, 466 samples were subjected to nucleic acid extraction and real-time PCR for gastrointestinal viral, bacterial and protozoan pathogens. Equal or even higher frequencies of pathogen detections from Whatman papers or flocked swabs were achieved compared with nucleic acid extraction directly from stool samples. Comparison of the Ct values showed no significant difference according to the nucleic acid extraction strategy. Also, the Ct values did not allow a decision whether a detected pathogen was associated with gastrointestinal symptoms.

HIV prevention strategies and risk of infection: a model-based analysis.

Risk populations for HIV infections tend to neglect condom use, making alternative preventive approaches necessary. Accordingly, we modelled the risk of sexual HIV transmission for condom use vs. use of rapid diagnostic test (RDT) systems with subsequent exclusion of potential sexual partners with a correctly or falsely positive test from unprotected sex with and without the use of HIV pre-exposure prophylaxis (PrEP) in a bio-statistical approach. We combined a previously described model of transmission risk for HIV-exposed individuals with a newly suggested model of risk of HIV exposure for sexually active HIV-negative individuals. The model was adapted for several stages of infection and different strategies of HIV infection prevention.HIV prevention with RDTs can reduce the transmission risk by up to 97% compared with having sex without any prevention and up to 80% compared with condom use. Nevertheless, RDT-based prevention strategies demonstrate a lack of protection in several stages of infection; in particular, RNA-based RDT systems may fail under treatment. RDT-based pre-screening of potential sex partners prior to unprotected sexual contacts substantially reduces HIV transmission risk. Combination of different prevention strategies is advisable for high-risk groups.

PCR-based rapid diagnostic tests as a strategy for preventing infections with sexually transmitted diseases-a 'diagnostics-as-prevention' modelling approach.

The potential was modelled of molecular rapid diagnostic tests (RDTs) that target agents of sexually transmitted diseases (STDs) to contribute to a reduction in the exposure risk for sexually active populations who prefer condom-free high-risk contacts. The biostatistical approach is exemplified by considering the use of a PCR-based RDT for Chlamydia trachomatis and Neisseria gonorrhoeae in a population of German men having sex with men. We modelled the exposure risk as risk of sexual contact with individuals infected by a STD in spite of multiple RDTs having been conducted to identify STDs that could lead to avoidance of an infectious sexual contact. The risk for a given specific disease is influenced by the diagnostic accuracy of all diagnostic tests conducted. The simulation showed a reduction in exposure risk through conducting the selected PCR-based RDT as a strategy to prevent infections with C. trachomatis and N. gonorrhoeae in comparison with unprotected sexual contact of >97% for C. trachomatis and ≥96% for N. gonorrhoeae. Reliable knowledge of the performance characteristics of the diagnostic tests applied is essential for a thorough risk assessment based on such diagnostic approaches. SIGNIFICANCE AND IMPACT OF THE STUDY: A low-threshold use of molecular rapid diagnostic tests in settings where risky sexual activity is undertaken with deliberate non-use of condoms is modelled. Such an approach might contribute to a considerable reduction in the exposure risk if positively tested individuals are excluded from unprotected sexual intercourse. Protective effects are influenced by the prevalence of the disease and the performance characteristics of the applied tests. Precise knowledge of the performance characteristics of the test assays employed are prerequisites of a reliable risk assessment. The modelling approach is of particular use for preventive health experts.

[Epidemiology of Ebola virus disease and of other highly contagious, life-threatening diseases with low incidence in Germany]. / Epidemiologie des Ebolafiebers und anderer, in Deutschland seltener hochkontagiöser, lebensbedrohlicher Erkrankungen.

Apart from sporadic exported cases, the occurrence of Ebola, Marburg and Lassa virus diseases is limited to the African continent. Crimean-Congo Hemorrhagic Fever occurs in Southeastern Europe but, so far, not in Germany. Other hemorrhagic fever disease-viruses occur in distinct regions in South America. Pulmonary plague is the bacterial infectious disease with the most contagious and lethal course and it is endemic to Madagascar and East Africa, but also occurs in other countries (e.g. India, USA). Monkey pox epidemics have occurred in remote areas of the Congo Basin. Such outbreaks could potentially become more common with the discontinuation of the cross-protective smallpox vaccination. The Severe Acute Respiratory Syndrome (SARS) that emerged in 2002/2003 is another pathogen with significant epidemic potential. Typical for these diseases is a natural circulation between reservoir animals in remote areas. Sporadic transmission to humans can occur through contact with an infected animal. Subsequent human-to-human transmission can lead to epidemics, such as the current outbreak of Ebola virus disease in West Africa.

Is rapid hepatitis C virus testing from corpses a screening option for index persons who have died after mass-casualty incidents in high-prevalence settings in the field?

INTRODUCTION: We tested a commercially available rapid hepatitis C virus (HCV) test assay for its potential use for analyses of corpses as a screening option for index persons who have died after mass-casualty incidents in high-prevalence settings in the field. MATERIALS AND METHODS: 50 blood samples were drawn from 16 recently deceased confirmed HCV-positive patients whose corpses were stored at 4°C in the mortuary and were analysed at admission and up to 48 h post mortem by rapid serological testing using the ImmunoFlow HCV test (Core Diagnostics, Birmingham, UK) in comparison with automated serological assays and PCR. Samples from 50 HCV-negative corpses were also analysed. RESULTS: The blood of only four of the 16 HCV-positive corpses reacted clearly with the ImmunoFlow HCV test, while in five cases the result was only weakly reactive and three cases showed very weak reactivity. Four of the infected corpses showed initially negative results, three of which became very weakly reactive 48 h post mortem. 49 out of 50 samples (98%) from HCV-negative corpses tested negative. DISCUSSION: The rapid test system we investigated showed insufficient sensitivity regarding the identification of HCV positivity. Automated serological testing or PCR should be preferred if it is realistically available in the deployed military setting.

Compliance with antimalarial chemoprophylaxis in German soldiers: a 6-year survey.

PURPOSE: Since 1992, German soldiers have been deployed in areas where malaria is endemic. Antimalarial chemoprophylaxis (CP) is directed according to the assessed risk and is provided free of charge. Compliance is crucial if its effect is to be reliable. This study analysed compliance with directed CP in German soldiers as well as its determinants. METHODS: Between 2003 and 2009, standardized questionnaire-based interviews were performed with 2,149 out of approximately 100,000 German soldiers who were deployed during this period in areas where malaria is endemic. The questionnaires dealt with information that the soldiers had received about malaria prior to their missions, with their adherence to mosquito-protective and antimalarial chemoprophylactic procedures, and their estimations of their individual level of exposure. RESULTS: About 1,308 out of 2,149 interviewed soldiers had been ordered to take CP, allowing for an assessment of the outcome parameter "CP-compliance". About 76.9 % out of 1,308 soldiers to whom regular CP was directed took it regularly. The exposure variables "age", "satisfaction with malaria counselling", "perceived threat due to insects or mosquitoes" and "use of insect repellents" were positively associated with compliance with directed antimalarial CP. CONCLUSIONS: The study confirms the findings of the French and US armies that even free-of-charge access to antimalarial medication will not lead to 100 % acceptance. The compliance problem is aggravated by the generally low age of deployed soldiers. Adequate counselling is crucial to increase adherence to antimalarial CP.

National health insurance coverage and socio-economic status in a rural district of Ghana.

OBJECTIVE: To explore the association between socio-economic status (SES) and health insurance subscription to the Ghanaian National Health Insurance Scheme (NHIS) of residents of the Asante Akim North district of the Ashanti Region, Ghana. METHODS: In the course of a community survey, data on asset variables (e.g. electricity, housing conditions and other variables) and on NHIS subscription were collected on the household level in 99 villages. Using principal components analysis, households were classified into three categories of SES (20% high, 40% middle and 40% low SES). Odds ratios of NHIS subscription were calculated for all SES categories, using the low category as the reference group and adjusting for travelling time to health facilities by public transport. RESULTS: Of the 7223 households surveyed, 38% subscribed to the NHIS, of these 21% were low, 43% middle and 60% high SES households. SES was significantly associated with NHIS subscription (high SES: OR 4.9, 95% CI 4.3-5.7; middle SES: OR 2.5, 95% CI 2.2-2.9; low SES: OR 1, reference group). CONCLUSION: Four years after its introduction, the NHIS has reached subscription rates of 38% in the district surveyed. However, to achieve the aim of assuring universal access to health care facilities for all residents of Ghana, in particular for individuals living under socio-economic constraints, increasing subscription rates are necessary.

A food-borne outbreak of hepatitis A virus (HAV) infection in a secondary school in Upper Normandy, France, in November 2006.

In November 2006, six symptomatic cases of hepatitis A in pupils of a secondary school in Upper Normandy, France, were reported to the district health service. This paper describes the outbreak investigation undertaken with the aim to identify the vehicle and source of infection, implement control measures and estimate the size of the outbreak. A primary case at the secondary school was defined as a pupil or a member of the staff with IgM anti-HAV detected in the serum and with onset of symptoms between 12 and 21 November 2006; a secondary case was defined as a contact to a primary case and who developed symptoms and had IgM anti-HAV two to seven weeks later. We performed a case control study of primary cases, controls being pupils visiting the same school (cases/controls 1:4) and inspected the canteen facilities. All 13 canteen employees were examined for anti-HAV IgM antibodies. A phylogenetic analysis of HAV of cases was performed. We identified 10 primary and 5 secondary cases. Among primary cases 90% reported eating liver pate at the canteen compared to 62% among controls (OR 5.5, 95% CI 0.62-256.9). One liver pate sample contained markers of faecal contamination. HAV genotypes were of one identical type. All 13 canteen employees were negative for IgM anti-HAV while four had anti-HAV total antibodies. We found deficiencies regarding food preparing procedures and insufficient hand washing facilities. The vehicle of the outbreak was believed to be the liver pate but the source of HAV could not be identified. Insufficient facilities in the canteen hindered staff from maintaining a high hygiene standard and were subsequently improved.

Comparing a single-day swabbing regimen with an established 3-day protocol for MRSA decolonization control.

OBJECTIVES: Success of methicillin-resistant Staphylococcus aureus (MRSA) decolonization procedures is usually verified by control swabs of the colonized body region. This prospective controlled study compared a single-day regimen with a well-established 3-day scheme for noninferiority and adherence to the testing scheme. METHODS: Two sampling schemes for screening MRSA patients of a single study cohort at a German tertiary-care hospital 2 days after decolonization were compared regarding their ability to identify MRSA colonization in throat or nose. In each patient, three nose and three throat swabs were taken at 3- to 4-hour intervals during screening day 1, and in the same patients once daily on days 1, 2 and 3. Swabs were analysed using chromogenic agar and broth enrichment. The study aimed to investigate whether the single-day swabbing scheme is not inferior to the 3-day scheme with a 15% noninferiority margin. RESULTS: One hundred sixty patients were included, comprising 105 and 101 patients with results on all three swabs for decolonization screening of the nose and throat, respectively. Noninferiority of the single-day swabbing scheme was confirmed for both pharyngeal and nasal swabs, with 91.8% and 89% agreement, respectively. The absolute difference of positivity rates between the swabbing regimens was 0.025 (-0.082, 0.131) for the nose and 0.006 (-0.102, 0.114) (95% confidence interval) for the pharynx as calculated with McNemar's test for matched or paired data. Compliance with the single-day scheme was better, with 12% lacking second-day swabs and 27% lacking third-day swabs from the nostrils. CONCLUSIONS: The better adherence to the single-day screening scheme with noninferiority suggests its implementation as the new gold standard.

Difficulties in species identification within the genus Haemophilus - A pilot study addressing a significant problem for routine diagnostics.

Diagnostic misidentifications of commensalic Haemophilus haemolyticus as pathogenic Haemophilus influenzae are frequent. This pilot study evaluates whether isolations of H. haemolyticus are frequent enough in Germany to cause a relevant diagnostic problem, considering the fact that even H. influenzae is a mere colonizer in about 30% of isolations. In microbiological laboratories of two hospitals located in Northern and Southern Germany, the distribution of Haemophilus spp. was analyzed during a six-month-period. Site of infection, sex, and age of the patients was taken into consideration. A total of 77 Haemophilus spp. isolates was acquired and discriminated on species level, comprising: 48 H. influenzae, 25 Haemophilus parainfluenzae, 3 H. haemolyticus, and 1 Haemophilus parahaemolyticus. The proportion of H. haemolyticus was calculated to range between 1.2% and 16.2 % within the 95% confidence limits. Commensalic Haemophilus spp. were isolated from oropharynx-associated sites only. H. influenzae, in contrast, was detected in clinically relevant materials like lower respiratory materials and conjunctiva swabs. Altogether, there was a low proportion of clinical H. haemolyticus isolates. Accordingly, the problem of unnecessary antibiotic therapies due to misidentifications of H. haemolyticus as H. influenzae is quantitatively negligible compared with the risk of confusing H. influenzae colonizations with infections.

Extrapolating respiratory tract infection incidences to a rural area of Ghana using a probability model for hospital attendance.

OBJECTIVE: The aim of the current study was to extrapolate incidences for respiratory tract infections (RTI) using referral data from a local hospital in Ghana weighted by the individual likelihood of a hospital visit. METHODS: Diagnoses from children visiting a rural hospital in Ghana during August 2007 to September 2008 were recorded. A logistic regression model, based on a population study conducted within the hospital catchment area, was used to calculate the individual probability of clinic attendance and to extrapolate the number of recorded cases. Cumulative incidences for children living in the hospital catchment area were estimated. RESULTS: Upper RTI was the most common respiratory diagnosis, with an extrapolated incidence of 17481 cases per 100000 per year, followed by pneumonia with an incidence of 2496 per 100 000 per year. All diseases analyzed were most common in the first year of life. CONCLUSIONS: In general the study results are in line with comparable studies. Several methodological issues biasing the results in different directions were identified. For example, opportunistic infections that are more often observed in hospital attendees are likely to be overestimated. However, the applied approach presents a tool for areas where disease monitoring systems are not established.