[CURRENT EPIDEMIOLOGY AND METHODS OF COMBATING TUBERCULOSIS. (II.)].
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Epidemiology↗
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Pneumococcal capsular antigen detection after enrichment culture: an alternative to culture methods in epidemiologic research.
Bacterial culture of Streptococcus pneumoniae followed by serotyping is not always feasible under field conditions. Antigen detection methods could be an alternative, but they are associated with sensitivity problems. In an effort to improve their sensitivity, we introduced an enrichment phase before antigen detection and compared the results with direct bacterial culture, using nasopharyngeal swabs from 95 children with symptoms of acute respiratory infection. Antigen detection was performed by latex agglutination and counterimmunoelectrophoresis. Streptococcus pneumoniae was found in 29 (30%) of the samples by culture, and in 42 (44%) by antigen detection after enrichment, an excess of 45% over culture findings. This excess was shown to represent true positive samples since pneumococcal DNA could be detected by polymerase chain reaction in all 15 antigen-positive, culture-negative samples. Two culture-positive samples were antigen-negative; in one of these the bacteria were nonencapsulated. We conclude that for type-specific demonstration of S. pneumoniae, detection of pneumococcal antigen after an enrichment step is a sensitive method that can be applied for epidemiologic study purposes, e.g., in vaccine trials, in areas without ready access to a good microbiology laboratory.
Acute Disease↗
[Epidemiology of noninfectious diseases--principles and methodology].
Contemporary epidemiology as a science extends considerably its object of research interest. Originally it was interested in the prevalence of communicable diseases in the population and investigated all the factors, which affected this distribution. In the last few decades, epidemiology passed from following-up of communicable diseases to the description and the analysis of all diseases, which occur on our planet. Because of interest in the diseases, which endanger civilization as a result of its development, is the epidemiology with this target is called sometimes the epidemiology of non-communicable diseases. Traditional and the historical experience of communicable diseases epidemiology, methods of the classic statistics and the epidemiological working method are its basic principles. Adequate design of epidemiological studies and modern indicators for evaluation of the health status are used. Epidemiology does not investigate the disease and the risk factor separately, but they are analyzed mutually at three levels as a relation, association and causality. Emphasis is laid on minimalization or complete elimination of confounding and bias.
Epidemiologic Methods↗
A comparative study on the application of 3 molecular methods in epidemiological typing of bacterial isolates using MRSA as a prototype.
OBJECTIVE: To evaluate and compare 3 widely used molecular techniques, namely, restriction endonuclease analysis of plasmid deoxyribonucleic acid (REAP), randomly amplified polymorphic DNA (RAPD) and pulsed-field gel electrophoresis (PFGE) for their suitability and usefulness in the typing and fingerprinting of bacterial isolates. METHODS: Twenty-four epidemiologically unrelated methicillin-resistant Staphylococcus aureus (MRSA) isolates were used to evaluate the molecular typing methods (REAP, RAPD and PFGE). The study was conducted at the Research and Diagnostic Laboratories of King Faisal Specialist Hospital and Research Center from January 2002 through January 2003. RESULTS: Only 20.8% of all isolates studied were of the same genotypes by all 3 methods. Two major clusters of strains each representing 33% of the total number of isolates were identified by REAP analysis. Each of RAPD and PFGE however, identified one major cluster represented by 54% and 83% of the total number of isolates, all 3 typing methods, therefore, showed the clonal genetic relatedness among distant MRSA isolates. However inter-strain comparison of fingerprint data generated from each method revealed differences in clonal representation of the MRSA isolates. CONCLUSION: Although a variety of molecular assays are available for typing of bacterial species, there is no single standardized protocol for routine analysis. Reproducibility and interpretation of genotypic data are therefore, highly dependent on methodologies employed by the individual laboratory. Our findings illustrate the importance of using a combination of methods in typing schemes of bacterial isolates. In terms of reproducibility and typeability we found that PFGE is superior to REAP and RAPD and, therefore, more suitable for routine, standardized tracing of nosocomial bacterial isolates.
Anti-Bacterial Agents↗
[Epidemiology and prevention of mental disorders].
From a bibliographic analysis and personal experiences, the authors present the advantages of the epidemiologic method in psychiatry. They point out its specificity and the methodological difficulties. Since the psychiatric practices are being deeply transformed, it becomes essential to know precisely the importance and the distribution of mental diseases in the population. It is not possible to image changing a care system trend without knowing the real needs of the population. The descriptive epidemiologic method contributes to this. The aim of analytic epidemiology is ever more important since it allows to spot the circumstances in which mental diseases appear and are developed, and to elaborate etiological hypotheses. Finally, this favors preventive approaches where evaluative epidemiology permits to measure the validity and effectiveness of programs which, like those elaborated for other social calamities (transmissible diseases, degenerative diseases), take place for studies in the field of mental health disorders.
Epidemiologic Methods↗
Point sources of air pollution.
Many people live near point sources of air pollution such as industrial sites and waste disposal operations and there are often suggestions of clusters of disease around such activities. Such alleged clusters will generate significant public concern and media interest and in many cases will warrant detailed investigation. However, the ability of current epidemiological methods to investigate such clusters is limited, particularly with regard to obtaining reliable and accurate population exposure data. In many cases, the key question is whether releases from a point source result in a significant increase in exposure or whether other sources (background exposure) give rise to the dominant exposure. This review considers some of the issues around point sources including methods of estimating exposure and briefly discusses some of the epidemiological evidence linking respiratory disease and cancer with specific industries such as coking works and incinerators.
Air Pollution↗
Epidemiological analysis and its importance in the problem of the eradication of infectious diseases. I. The theoretical and organizational prerequisites for the development of the method of epidemiological analysis.
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Communicable Diseases↗
[Use of computers and mathematical methods in epidemiological work. V. Assessment of infection morbidity using standardized indices].
The paper treats of the method of obtaining special and generalized indices on the computer M-222 to be used for the analysis of infectious morbidity under the automatic control system conditions. Assessment of significance of the differences between the actual number of diseases and the "usual" morbidity level characteristic of the given territory and the time of the year lies at the basis of the calculation of the standardized indices. Complex evaluation of the epidemiological condition of the controlled district was carried out according to the data of the official monthly and annual sanitary-epidemiological report forms No. 85.
Computers↗
Evaluation of methods for epidemiologic typing of group A streptococci.
Serotyping is widely used for epidemiologic investigation of group A streptococci (GAS). To evaluate molecular typing methods of GAS, restriction endonuclease analysis (REA) of genomic DNA and analysis of DNA restriction fragment length polymorphism of rRNA genes (ribotyping) were used in parallel with serotyping. The genomic DNA of 239 epidemiologically unrelated GAS isolates from human invasive infections was digested with HindIII restriction enzyme. Both REA and ribotyping differentiated subclasses within serotypes. However, they did not consistently differentiate between isolates of different serotypes. Ribotyping was less discriminatory than REA. Within the T1M1 serotype, often associated with invasive GAS infections, 92% of the REA patterns were identical, suggesting a common origin for these isolates. Most other serotypes studied were more heterogenic. Among 32 isolates nontypeable by serotyping, 11 distinct REA patterns and 5 ribotypes were identified. REA and ribotyping are useful supplementary tools for classification of GAS and can add to the discriminatory power of serotyping.
Deoxyribonuclease HindIII↗
Applications of the case-control method in genetic epidemiology.
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Case-Control Studies↗
Phenotyping methods in epidemiological analysis of epidemic Staphylococcus aureus strains.
One hundred and fifty hospital Staphylococcus aureus strains isolated on Polish hospitals during an outbreaks were used to evaluate usefulness of S. aureus phenotyping methods. According to the expression of resistance to methicillin (a marker of resistance to all beta-lactam antibiotics) all strains were classified as homogeneously of heterogeneously resistant to methicillin (methicillin resistant S. aureus--MRSA) and as susceptible to this antibiotic (methicillin-susceptible S. aureus--MSSA). All strains were analysed according to the resistance patterns to fifteen antistaphylococcal drugs, results of crystal violet test, phage patterns and results of biochemical fingerprinting by PhenePlate (PhP) System (BioSys inova). All MSSA analysed were resistant to penicillin and 22% to tetracycline, and only occasionally resistant to other antimicrobials. They showed sensitive to phages of all international and additional lytic groups. Heterogeneous MRSA were widely susceptible to almost all antimicrobials except tetracycline and were lysed by phages of Ist, IIIrd international groups and additional phages. All these strains produced penicillinases. Homogeneous MRSA were multi-drug resistant and were not typable by phages of Ist and IInd lytic groups and weakly typable by phages of IIIrd and additional groups. PhP Systems divided all used strains into 13 common (with two dominating) and 50 single strain PhP-types. The combination of various phenotyping methods may be useful in epidemiological investigation of hospitals.
Anti-Bacterial Agents↗
Value of molecular epidemiologic analysis in a nosocomial methicillin-resistant Staphylococcus aureus outbreak.
OBJECTIVE: To evaluate two molecular epidemiologic methods used in the analysis of a nosocomial methicillin-resistant Staphylococcus aureus (MRSA) outbreak. DESIGN: Restriction endonuclease analysis of plasmid DNA (REAP) was used in the analysis of 45 MRSA isolates. After termination of the outbreak, isolates were retrospectively analyzed in a blind fashion using the newly described technique of arbitrarily primed polymerase chain reaction (AP-PCR). Molecular analyses were compared with epidemiologic and antimicrobial susceptibility data. SETTING: Tertiary care university hospital. SUBJECTS: Twenty-eight patients and 12 employees infected or colonized with MRSA during a 6-week period. RESULTS: A clonal relationship demonstrated among isolates from burn unit patients and staff was clearly distinguishable from MRSA isolates arising from other hospital wards. The combination of REAP and AP-PCR provided complementary information in several instances. Aggressive measures to isolate infected patients and eradicate colonization from patients and staff terminated the outbreak. CONCLUSIONS: Although traditional epidemiologic methods retain their central role in modern hospital infection control, molecular epidemiologic analysis can significantly enhance the ability of infection control officers to analyze and terminate hospital epidemics. The combination of AP-PCR and REAP may prove to be a particularly informative means of tracking the nosocomial spread of microbial strains and their mobile genetic elements.
Adolescent↗
[Intraocular pressure and primary open-angle glaucoma. Epidemiologic technics in practice].
It is the object of this paper to familiarize the ophthalmologist with some modern epidemiological techniques and to present examples of their application to a consideration of the influence of the level of intraocular pressure on the development of the type of visual field loss characteristic of primary open angle glaucoma. Epidemiological methods are particularly required in chronic multifactorial diseases such as primary open angle glaucoma and arterial hypertension to obtain reliable guidance on practical measures for their treatment or control. Two basic requirements are reliable uniform data suitable for computer manipulation and epidemiological methods to exploit the data and yield conclusions as free of bias and confounding as possible. An example of a glaucoma data base is described and types of enquiry and the importance of standardising prevalence estimations are discussed. Analyses by the four-fold table, risk ratios, the effect of stratification, sensitivity, specifity and the decision curve are described. Attributable risk (potential for prevention) is indicated as yielding information suitable for public health programmes. The life table method is described when relating initial observations to subsequent progressive visual field loss. The factors to be considered in epidemiological work generally and the inferences concerning the early diagnosis of primary open angle glaucoma are discussed.
Age Factors↗
The role of epidemiology in public health.
Epidemiology is the study of disease in populations. Veterinarians and others involved in the preventive medicine and public health professions use epidemiological methods for disease surveillance, outbreak investigation, and observational studies to identify risk factors of zoonotic disease in both human and animal populations. Knowledge of these risk factors is used to direct further research investigation and to implement disease control measures. The use of hazard analysis critical control point (HACCP) systems depends greatly on information produced by epidemiological studies. Epidemiological methods are used for disease surveillance to identify which hazards are the most important. Epidemiological studies are also used to identify risk factors which may represent critical control points in the food production system.
Animals↗
Molecular epidemiology of Staphylococcus epidermidis in a neonatal intensive care unit over a three-year period.
Coagulase-negative staphylococci, especially Staphylococcus epidermidis, are increasingly important nosocomial pathogens, particularly in critically ill neonates. A 3-year prospective surveillance of nosocomial infections in a neonatal intensive care unit (NICU) was performed by traditional epidemiologic methods as well as molecular typing of microorganisms. The aims of the study were (i) to quantify the impact of S. epidermidis on NICU-acquired infections, (ii) to establish if these infections are caused by endemic clones or by incidentally occurring bacterial strains of this ubiquitous species, (iii) to evaluate the use of different methods for the epidemiologic typing of the isolates, and (iv) to characterize the occurrence and the spread of staphylococci with decreased glycopeptide susceptibility. Results confirmed that S. epidermidis is one of the leading causes of NICU-acquired infections and that the reduced glycopeptide susceptibility, if investigated by appropriate detection methods such as population analysis, is more common than is currently realized. Typing of isolates, which can be performed effectively through molecular techniques such as pulsed-field gel electrophoresis but not through antibiograms, showed that many of these infections are due to clonal dissemination and, thus, are potentially preventable by strict adherence to recommended infection control practices and the implementation of programs aimed toward the reduction of the unnecessary use of antibiotics. These strategies are also likely to have a significant impact on the frequency of the reduced susceptibility of staphylococci to glycopeptides, since this phenomenon appears to be determined either by more resistant clones transmitted from patient to patient or, to a lesser extent, by strains that become more resistant as a result of antibiotic pressure.
Birth Weight↗
Cancer Epidemiology.
The methods of epidemiological studies of cancer in man are discussed briefly with reference to sources of information and the clues they may provide to cancer aetiology. Some of the features of the cancer patterns in Singapore are presented. Geographical and racial variations in cancer incidence and their possible determinants are discussed and tabulated.
Data Collection↗
Overview of preventable industrial causes of occupational cancer.
This paper summarizes what is known about preventable causes of occupational cancer, including single agents, complex mixtures, and broad occupational associations. Epidemiologic methods have been very successful in documenting cancer risks associated with single agents. Epidemiologic data are most conclusive when an exposure-response relationship can be demonstrated. Examples of agents for which epidemiologic studies provide evidence of an exposure-response relationship include benzene and (concurrent exposure to) ortho-toluidine and aniline. Vinyl chloride and bischloromethyl ether are examples of associations between single agents and rare histologic types of cancer. It is more difficult to conduct epidemiologic studies to identify cancer risks associated with complex mixtures. Studies of diesel exhaust and lung cancer and metal machining oils are cited as having employed advanced industrial hygiene and epidemiologic methods for studies of complex mixtures. Elevated cancer risks have also been identified in broad occupational groups, including painters and dry cleaners. Epidemiologic case-control studies are often used to detect such associations but are limited in their abilities to detect the causal agents. Major gaps exist in knowledge of occupational cancer risks among women workers and workers of color. Because epidemiologic research measures illness and mortality that have already occurred, a positive study can be interpreted to represent a failure in prevention. The challenge we face in the next decade is to identify interventions earlier in the causal pathway (toxicologic testing, biomarkers of exposure or precancerous changes, institution of engineering and good industrial hygiene practices to reduce occupational exposure levels) so that occupational cancer can be prevented.
Carcinogens↗
[New methods for studying drug associated risk: experience of the Toulouse Regional Pharmacovigilance Center].
This review examines the methods used to study adverse drug reactions (ADRs) and to quantify drug risk in pharmacovigilance. Beside analysis of spontaneous reports (the basic and universal alert method in pharmacovigilance), epidemiological methods can also be used. Classical methods are based on intensive recording, case-control or cohort studies, and clinical trials. Other more recent methods have been applied to pharmacovigilance. Using recent personal data, the authors present and discuss these new methods. Case/non-case studies quantify drug risk based on a pharmacovigilance database, and are used as signals in pharmacovigilance. Analysis of laboratory data can also be used to evaluate biological ADRs such as elevated liver enzyme and creatine phosphokinase levels. Cross-linkage studies can be used to minimize the consequences of under-notification in pharmacovigilance. Finally, ADR perception analysis is a useful method to evaluate the perceived social and medical importance of drug risks in different populations (public, pharmacists, general practitioners, medical specialists).
Adverse Drug Reaction Reporting Systems↗