Métodos de diagnóstico rápido en microbiología clínica: necesidades clínicas

The diagnostic methods of infectious diseases should be fast, accurate, simple and affordable. The speed of diagnosis can play a crucial role in healing the patient, allowing the administration of appropriate antibiotic treatment. One aspect that increasingly determines the need for rapid diagnostic techniques is the increased rates of serious infections caused by multidrug resistant bacteria, which cause a high probability of error in the empirical treatment. Some of the conventional methods such as Gram staining or antigen detection can generate results in less than 1 hour but lack sensitivity.Today we are witnessing a major change in clinical microbiology laboratories with the technological advances such as molecular diagnostics, digital microbiology and mass spectrometry. There are several studies showing that these changes in the microbiological diagnosis reduce the generation time of the test results, which has an obvious clinical impact.However, if we look into the future, other new technologies which will cover the needs required for a rapid microbiological diagnosis are on the horizon. This review provides an in depth analysis of the clinical impact that the implementation of rapid diagnostic techniques will have on unmet clinical needs.     

Results of a Local Antibiotic Management Program on Antibiotic Use in a Tertiary Intensive Care Unit in Hungary

Background  Massive antibiotic use in intensive care units (ICU) is associated with increased microbial resistance. Therefore avoiding unneccesary antibiotic usage is essential. To achieve a more considered antibiotic prescribing practice, a new antibiotic policy was implemented at our ICU. In this paper, we evaluated the impact of this intervention, and described the aetiology and incidence of blood stream infections and selected antibiotic-resistant pathogens. Materials and Methods  In November 2002, a local antibiotic management program (LAMP) was implemented. This included a new infectious diseases specialist consultation service and restricted authorisation to prescribe antibiotics. The effect on ward-level antibiotic use was examined by segmented regression analysis. Patient, ICU and microbiology data were also recorded and compared before and after policy implementation. Results  The patient populations and the subsequent mortality rate were comparable before and after the implementation of the policy. Total antibiotic consumption was markedly reduced from 162.9 to 101.3 defined daily dose (DDD) per 100 patients, and per day (DDD per 100 patient-days). This was mainly accounted for a reduction in the use of quinolones, aminoglycosides, glycopeptides, metronidazol, carbepenems and third generation cephalosporins. Conclusion  This study has confirmed that establishing a targeted LAMP, based on close co-operation between intensive care physicians and infectious disease specialists together with a restricted prescribing authority, can reduce the use of antibiotics.     

Antimicrobial susceptibility testing: special needs for fastidious organisms and difficult-to-detect resistance mechanisms.

Clinical microbiology laboratories are faced with the challenge of accurately detecting emerging antibiotic resistance among a number of bacterial pathogens. In recent years, vancomycin resistance among enterococci has become prevalent, as has penicillin resistance and multidrug resistance in pneumococci. More recently, strains of methicillin-resistant Staphylococcus aureus with reduced susceptibility to vancomycin have been encountered. In addition, molecular techniques have demonstrated that there are still problems detecting methicillin resistance in staphylococci, especially in coagulase-negative species. Among members of the family Enterobacteriaceae, mutated beta-lactamase enzymes may confer difficult-to-detect resistance to later-generation penicillins and cephalosporins. Anaerobic bacteria are no longer entirely predictable in their susceptibility to agents that might be selected for empiric therapy. Therefore, clinical microbiology laboratories may not be able to rely on a single susceptibility testing method or system to detect all those emerging resistant or fastidious organisms. For reliable detection, laboratories may need to employ conventional, quantitative susceptibility testing methods or use specially developed, single concentration agar screening tests for some resistant species. Certain of these screening tests are highly specific, while others may require additional confirmatory testing for definitive results. Therefore, laboratories must retain the versatility to apply several different approaches to detect resistance in both common and infrequently encountered bacterial pathogens.     

Infectious diseases as a Canadian subspecialty, with projections to the year 2000

Infectious diseases is a relatively new subspecialty in Canada. During the past decade, however, important advances have been made. These include the formation of the Canadian Infectious Diseases Society and the development of the first Royal College of Physicians and Surgeons examinations in the subspecialty of infectious diseases. The majority of Canadians training for practice in the field of infectious diseases are now enrolled in programs in Canada. Despite predictions in the United States of an excess of physicians who specialize in infectious diseases, such a situation has not occurred in Canada. More physicians with training in infectious diseases will be required in Canada in the next decade to fill positions in patient care, microbiology (for individuals with both clinical and laboratory training), research, epidemiology and infection control, programs related to human immunodeficiency virus infections, geographic and international medicine, the pharmaceutical industry, and education and administration. In Canada, the extent to which infectious diseases physicians are involved in these areas varies from that in the United States. This review suggests a continued need for physicians with appropriate training in infectious diseases.     

Interpretive reading of the antibiogram: Intellectual exercise or clinical need?

Clinical categorisation of susceptibility testing results according to criteria established by different committees is daily performed in clinical microbiology laboratories. By this process clinicians can predict the therapeutic success of antimicrobial treatment in patients infected with susceptible microorganisms. In addition, microbiology laboratories that include a suitable number of antimicrobial agents in susceptibility tests can perform interpretive reading of the antibiogram. With this approach, resistance phenotypes are recognized and allow microbiologist: a) detection of mechanisms of resistance, including low levels of expression; b) modification of clinical classifications that are inconsistent with the inferred resistance mechanism; and c) inference of susceptibility values for antimicrobials that are not included in the antibiogram. In the laboratory, this approach facilitates quality control and validation of susceptibility results. Moreover, it increases the value of the results obtained because new mechanisms of resistance can be characterized and the epidemiology of resistance can be established. From the clinical point of view, this approach contributes to improving the adequacy of treatment (since it is useful for predicting therapeutic failure with the use of antimicrobials in patients with infections due to resistant microorganisms) and to controlling and defining antimicrobial policies. Despite the growing complexity of resistance mechanisms, which makes interpretative reading of the antibiogram difficult, this process should be incorporated into routine practice in microbiology laboratories. Interpretive reading of antibiograms is clinically necessary and not simply a intellectual exercise.     

Real-time PCR

PCR based assays are currently used routinely in most microbiology laboratories. But, with few exceptions, they are restricted to the field of virology, especially to a limited number of viral targets with important economical interest for which commercially well standardized assays are available. For several reasons, it has had a poor implementation of the PCR assays into routine diagnostics for other infectious diseases despite they are advantageous. Combined with automated sample isolation of nucleic acids, real-time PCR gives an ideal platform for the development of molecular assays for a wide range of infectious agents with clinical interest. Because of its advantages, as simplicity, rapidity and minor risk of contamination, real-time PCR will go replace conventional PCR assays and its use will extend to a wide range of applications in clinical microbiology.     

Clinical microbiology and the outpatient

The boundaries between "hospital" and "extrahospital" microbiology do not exist as such and it would be more appropriate to speak of the microbiological care of inpatients or outpatients. Therefore, today, the development of clinical microbiology obligatorily the outpatient. The strengthening of this interventional setting should entail both individual diagnosis of outpatients as well as epidemiological surveillance of infectious diseases in the non-hospital setting, detection of levels of resistance among the most common pathogens and, moreover, the control of this resistance in the healthy population.     

宏基因组技术在感染性疾病中的应用

宏基因组测序(mNGS)正越来越多地应用于临床实验室的诊断.该文探讨了这项诊断传染病的新技术的目前实施情况,并讨论将mNGS转变为常规诊断技术的可行性.大量研究表明,mNGS在直接从临床样本中识别常规、罕见、协同感染病原体并对解决抗生素耐药性问题,提供了新的诊断证据,可用于指导治疗方案和改进抗生素管理.mNGS是解决临...     

Tensions in antibiotic prescribing

BACKGROUND: To reduce the prevalence of antibiotic-resistant bacteria in the community, physicians must optimize their use of antibiotics. However, optimal use from the perspective of the community (reserving newer agents for future use) is not always consistent with optimal use from the perspective of the individual patient (prescribing newer, broader agents). OBJECTIVES: To identify preferred patterns of antibiotic prescribing for patients with community-acquired pneumonia (CAP), measure explicit attitudes toward antibiotics and antibiotic resistance, and determine the relationship between these prescribing patterns and attitudes. DESIGN: Cross-sectional anonymous mail survey. PARTICIPANTS: National random sample of 400 generalist physicians (general internal medicine and family practice) and 429 infectious diseases specialists. MEASUREMENTS: Rank ordering of antibiotic preferences for a hypothetical outpatient with CAP and reasons for antibiotic selection. Endorsement of attitudes regarding antibiotic prescribing decisions and resistance. RESULTS: Both generalists and infectious diseases specialists were more likely to prefer newer, broader drugs for the treatment of CAP compared to older agents still recommended by national guidelines. Physicians rated the issue of contributing to antibiotic resistance lowest among 7 determinants of their choices. CONCLUSIONS: Despite national guidelines and increasing public awareness, the public health concern of contributing to the problem of antibiotic resistance does not exert a strong impact on physician prescribing decisions for CAP. Future efforts to optimize antibiotic prescribing decisions will need to consider options for increasing the impact of public health issues on the patient-oriented decisions of individual physicians.     

Basis, types and application of DNA arrays in clinical microbiology

The DNA microarrays or microchips are sets of DNA probes bound to a solid support in a prefixed and regular disposition. The target nucleic acid that can be detected is either DNA or RNA, which is previously labeled with a fluorochrome or a radioactive compound. The main advantage with respect to other molecular biological tools, such as polymerase chain reaction, is that thousands of genes can be detected in a single procedure. The application of the DNA arrays in the field of clinical microbiology is so far scarce. Among the specific applications we can point out: 1. Investigation of bacterial pathogenesis; 2. Analysis of bacterial evolution and molecular epidemiology; 3. Study of the mechanisms of action and resistance to antimicrobial agents and 4. Microbiological diagnostic of the infectious diseases. This methodology is still in an embryonic phase with respect to its application in clinical microbiology. However, it presents a series of advantages that make it very attractive and in the future it may become a valuable tool for the diagnosis of infectious diseases.     

The Potential for PCR Based Testing to Improve Diagnosis and Treatment of Sepsis

Early and appropriate antibiotic use is critical for the treatment of sepsis. In practice, however, early antibiotic administration is hampered by diagnostic uncertainty with regard to both early diagnosis of disease and delayed or absent microbiological results. The diagnostic uncertainty often persists into the later stages of sepsis when clinical response to antibiotic treatment is assessed. Blood culture, the current “gold standard” test for diagnosis of sepsis, is inadequate due to low sensitivity and delayed results. However, despite this, the technology remains entrenched in microbiology laboratories due to decades of accumulated experience with the technique. However, in recent years there has been increasing experience with testing based on polymerase chain reaction (PCR). As the technology continues to improve, PCR testing is becoming faster and more sensitive. Moreover, PCR technologies that quantify bacterial load may enable monitoring of response to treatment and susceptibility testing.     

Use of the clinical microbiology laboratory for the diagnosis and management of infectious diseases related to the oral cavity

Our knowledge regarding the pathogenesis of infections relative to the oral cavity is rapidly expanding, similar to our overall understanding of how infectious diseases impact our daily lives. The complexity of the flora within the oral cavity is quite unique and often makes diagnosis difficult; however, it is becoming more apparent that accurate diagnostic testing is important from the standpoint of focusing appropriate therapy on pathogens within this crucial body site, and avoiding overuse of antimicrobial agents in settings of infection where they have no demonstrated benefit. New diagnostic methods are being developed to detect pathogens and rapidly delineate resistance patterns. Many will be based on new genetic assays, but they must be cost effective, sensitive, and specific. Another growing challenge is to provide adequate lab support to outpatient offices and clinics, without compromising the specimen culture or turnaround times. So many patients are being seen away from hospital laboratories that we need ways to diagnose sinusitis, pharyngitis, abscess, and other infections of the oral cavity without killing the anaerobes and other significant facultative bacteria, and without ruining the direct stains by overgrowth or inflammatory cell degradation during specimen transport. These results need to be available quickly enough to give useful information for office diagnosis in order to effect therapy. To optimize both diagnosis and treatment, a key to the future will be better communication between the clinical practitioner and laboratory, with an increasing emphasis on training expertise in medical microbiology and infectious diseases.     

Professional challenges and opportunities in clinical microbiology and infectious diseases in Europe

The two closely linked specialties of clinical microbiology and infectious diseases face important challenges. We report the consensus of clinical microbiologists and infectious disease physicians assembled by the European Society for Clinical Microbiology and Infectious Diseases. Both specialties have different training requirements in different European countries and are not universally recognised as professions. The specialties are rapidly evolving as they adapt to the changing demands within hospital practice, including the need to deal with emerging infections, rapidly increasing internationalisation, and immigration. Clinical microbiology needs to develop and master technological advances such as laboratory automation and an avalanche of new methods for rapid diagnostics. Simultaneously, the pressure for concentration, amalgamation, and out-sourcing of laboratory services is ever-increasing. Infectious disease physicians have to meet the professional challenge of subspecialisation and the continual need to find new niches for their skills. Despite these challenges, each of these specialties continues to thrive in Europe and will enjoy important opportunities over the next few years. The recently formed European Centre for Disease Prevention and Control in Stockholm, Sweden, will increase demands in areas of surveillance of infectious diseases and antimicrobial resistance on both specialties.     

感染性疾病科医生应具备的素养

感染性疾病(感染病)科医生在感染病的临床诊治、危重症救治、抗感染药物的合理应用、感染控制以及临床教学和科研等方面发挥着重要作用,因此须注重在临床实践中不断提高自身的素养.本文就感染病科医生如何提高自身素养进行探讨.     

Optimizing therapy for infections caused by enterobacteriaceae producing extended-spectrum beta-lactamases

The spread of multidrug-resistant Enterobacteriaceae is complicating the treatment of nosocomial infections. In many parts of the world, resistance to third-generation cephalosporins exceeds 10% of total nosocomial isolates and 30% of isolates detected in the intensive care unit. This resistance is frequently due to the acquisition of plasmids containing genes encoding for extended-spectrum beta-lactamases (ESBLs). Furthermore, these mobile elements often carry genes encoding resistance to other drugs such as aminoglycosides. A high risk of poor clinical outcome has been observed in patients infected with ESBL producers receiving third-generation cephalosporins, even if the organism appears susceptible to the antibiotic. For this reason, clinical microbiology laboratories are advised to incorporate specific ESBL detection methodology into routine clinical practice. This should prevent erroneous use of cephalosporins for these infections. Most ESBL producers remain susceptible to carbapenems, and these agents are considered the drugs of choice against ESBL-producing organisms. Unfortunately, there is now an increasing occurrence of carbapenem resistance in the Enterobacteriaceae. In this context, clinical response to new antibiotics (e.g., tigecycline) and old antibiotics (e.g., colistin) with good in vitro activity against ESBL producers needs to be evaluated.     

2013年美国《感染性疾病微生物学实验室诊断应用指南》简介--病原及标本处理部分

为了更好地发挥微生物学检测结果在感染病临床诊断中的重要作用,提高微生物检测前标本质量,本文重点介绍《美国感染性疾病微生物学实验室诊断指南》中微生物标本的选择、采集、运输等方法和处理原则,为临床和实验室规范操作提供指导。     

The European Laboratory Working Group on Diphtheria: A global microbiologic network

Increasing international travel, migration to and from epidemic areas, and the emergence of epidemic Corynebacterium diphtheriae strains globally have highlighted the need for better microbiologic surveillance and greater clinical and laboratory awareness. As part of the strategy developed by the World Health Organization, one major goal is particularly applicable to the microbiology and epidemiology of diphtheria: to improve surveillance for early detection of emerging and reemerging diseases by establishing a network of national and international laboratories. The European Laboratory Working Group on Diphtheria (ELWGD) was therefore formed in 1993 as a result of the epidemic situation in Eastern Europe. Currently, there is participation from 20 different countries from Western and Eastern Europe, the United States, Australia, and Southeast Asia. ELWGD is a prime example of a collaborative and coordinated approach to the microbiology of diphtheria and should serve as a potential model for other infectious diseases networks.     

Community-acquired bacterial pneumonias

Community-acquired bacterial pneumonias are among the most common of infectious diseases. The diagnosis of the etiological agent is becoming more challenging and more critical as new organisms are recognized as pathogens, and as well established agents become increasingly resistant to antimicrobial agents. The value of clinical microbiology laboratory data in the management of pneumonia is controversial. A well recognized, published guideline suggests that no laboratory studies be performed. Yet common practice and a more recent guideline advocate routine collection of sputum for Gram's stain and culture, along with traditional blood work. Given the increasing need to distinguish among a long list of possible pathogens and the need to recognize antibiotic resistance, it seems most prudent to include microbiological studies.This information can be used to guide initial therapy, and perhaps limit the overutilization of broad-spectrum antimicrobials. However, a prerequisite for the use of all cunently available test methods is their deployment in patients for whom there is clinical and radiographic evidence of pneumonia because recovery of a microorganism, especially from sputum, will occur with or without this clinical condition.     

The role of antibiotics in the treatment of infectious diarrhea

Infectious diarrhea is a significant cause of morbidity and mortality and a common complaint in clinical practice. Routine empirical use of antibiotics for infectious diarrhea should be avoided because of the self-limited nature of most cases, the cost of antibiotics, and the potential to worsen the already significant problem of antibiotic resistance of enteric pathogens. For patients with severe invasive or prolonged diarrhea or who are at high risk of complications, such as the elderly, diabetics, cirrhotics, and immunocompromised patients, empirical treatment with a quinolone antibiotic for 3 to 5 days can be considered. Antibiotic treatment can be highly effective for Shigella, ETEC, and V. cholerae infections, and metronidazole is indicated for C. difficile colitis. The impact of antibiotics for other specific pathogens is modest, and antibiotic therapy should be reserved for the same group of patients who would be considered for empirical treatment. The most significant problem in the antibiotic treatment of infectious diarrhea is the progressive increase in resistance among enteric pathogens; only the prudent use of antimicrobials in all areas of daily practice can limit or delay the impact of this serious problem.     

A national task analysis of infection control practitioners, 1982. Part Two: Tasks, knowledge, and abilities for practice

Respondents (N = 473) from a randomized stratified sample (N = 600) of U.S. hospital ICPs in a national survey sponsored by the Certification Board of Infection Control were asked to rate specific task, knowledge, and ability statements related to infection control for frequency and importance. The questions included 175 items, of which 99 were for specific tasks and 76 were for knowledge and abilities for practice. Areas covered included patient care practices, infectious diseases, epidemiology and statistics, microbiologic practices, sterilization and disinfection, education, employee health services, and management and communications. A "profile respondent" group (N = 317) was defined as persons most likely to be practicing the full scope of infection control practice and was used to identify key tasks, knowledge, and abilities for practice. Results showed that patient care practices (i.e., suctioning, dressing changes, and catheterization) were rarely performed. The development of infection control policies and procedures were key tasks. Knowledge of microbiology and infectious diseases in order to interpret laboratory reports and other patient data was rated as essential; however, few respondents actually performed laboratory procedures. Epidemiologic principles were frequently used for surveillance and problem investigation. Although presentation of epidemiologic data was rated as important, analytic statistics were rarely used. Assessment of educational needs and teaching were large components of ICPs' activities.