Neoteric advancements in TB diagnostics and its future frame

Tuberculosis (TB) is one of the major infectious disease that causes threat to human health and leads to death in most of the cases. Mycobacterium tuberculosis is the causative agent that can affect both pulmonary and extra pulmonary regions of the body. This infection can be presented either as an active or latent form in the patients. Although this disease has been declared curable and preventable by WHO, it still holds its position as a global emergency. Over the past decade many hurdles such as low immunity, co-infections like HIV, autoimmune disorders, poverty, malnutrition and emerging trends in drug resistance patterns are hindering the eradication of this infection. However, many programmes have been launched by WHO with involvement of governments at various level to put a full stop over the disease. Under the Revised National Tuberculosis Control Programme (RNTCP) which was recently renamed as National Tuberculosis Elimination Programme (NTEP), the major focus is on eliminating tuberculosis by the year 2025. The main aim of the programme is to identify feasible quality testing, evaluate through NIKSHYA poshak yozana, restrict through BCG vaccination and assemble with public awareness to eradicate MTB. Numerous novel diagnostic techniques and molecular tools have been developed to elucidate and differentiate report of various suspected and active tuberculosis patients. However, improvements are still required to cut short the duration of the overall process ranging from screening of patients to their successful treatment.

Emerging Technologies for Molecular Diagnosis of Sepsis

Rapid and accurate profiling of infection-causing pathogens remains a significant challenge in modern health care. Despite advances in molecular diagnostic techniques, blood culture analysis remains the gold standard for diagnosing sepsis. However, this method is too slow and cumbersome to significantly influence the initial management of patients. The swift initiation of precise and targeted antibiotic therapies depends on the ability of a sepsis diagnostic test to capture clinically relevant organisms along with antimicrobial resistance within 1 to 3 h. The administration of appropriate, narrow-spectrum antibiotics demands that such a test be extremely sensitive with a high negative predictive value. In addition, it should utilize small sample volumes and detect polymicrobial infections and contaminants. All of this must be accomplished with a platform that is easily integrated into the clinical workflow. In this review, we outline the limitations of routine blood culture testing and discuss how emerging sepsis technologies are converging on the characteristics of the ideal sepsis diagnostic test. We include seven molecular technologies that have been validated on clinical blood specimens or mock samples using human blood. In addition, we discuss advances in machine learning technologies that use electronic medical record data to provide contextual evaluation support for clinical decision-making.

Looking in ticks for human bacterial pathogens

Ticks are considered to be second worldwide to mosquitoes as vectors of human diseases and the most important vectors of disease-causing pathogens in domestic and wild animals. A number of emerging tick-borne pathogens are already discovered; however, the proportion of undiagnosed infectious diseases, especially in tropical regions, may suggest that there are still more pathogens associated with ticks. Moreover, the identification of bacteria associated with ticks may provide new tool for the control of ticks and tick-borne diseases. Described here molecular methods of screening of ticks, extensive use of modern culturomics approach, newly developed artificial media and different cell line cultures may significantly improve our knowledge about the ticks as the agents of human and animal pathology.

Advances in the diagnosis of endemic treponematoses: yaws, bejel, and pinta

Improved understanding of the differential diagnosis of endemic treponematoses is needed to inform clinical practice and to ensure the best outcome for a new global initiative for the eradication of yaws, bejel, and pinta. Traditionally, the human treponematoses have been differentiated based upon their clinical manifestations and epidemiologic characteristics because the etiologic agents are indistinguishable in the laboratory. Serological tests are still considered standard laboratory methods for the diagnosis of endemic treponematoses and new rapid point-of-care treponemal tests have become available which are extremely useful in low-resource settings. In the past ten years, there has been an increasing effort to apply polymerase chain reaction to treponematoses and whole genome fingerprinting techniques have identified genetic signatures that can differentiate the existing treponemal strains; however, definitive diagnosis is also hampered by widespread unavailability of molecular diagnostics. We review the dilemmas in the diagnosis of endemic treponematoses, and advances in the discovery of new diagnostic tools.

[The present and future prospects in rapid molecular diagnosis of tuberculosis and MDR-TB (First Part)]

Tuberculosis is still one of the diseases with a major medical and social impact, and in terms of early diagnosis (which would imply a fair treatment and established at the time), difficulties related to the delay bacilli isolation in culture, decreased susceptibility testing methods to antituberculosis drugs, lack of methods for differentiation of M. Tuberculosis complex germs of non TB Mycobacteria, may have important clinical implications. Traditional testing of anti-TB drug susceptibility on solid Löwenstein-Jensen medium (gold standard) or liquid media can only be performed using grown samples. Determining the time it takes up to 42 days on solid media and 12 days for liquid media. For MDR/XDR TB cases is absolutely essential to reduce the detection time. In these cases prove their usefulness rapid diagnostic methods. Automatic testing in liquid medium, molecular hybridization methods are currently recommended by the current WHO guidelines. Rapid diagnosis of MDR-TB is extremely useful for the early establishment of an effective treatment tailored more accurately on the spectrum of sensitivity of the resistant strain (thus reducing the risk of developing additional resistance to other drugs) and control the spread of these strains. Genetic diagnostic methods, approved and recommended by the WHO, can reduce the time of diagnosis of TB case and, importantly, the case of MDR TB. They do not replace the current standard diagnostic methods and resistance profile, but complete them in selected cases.

Review of two decades of cholera diagnostics--how far have we really come?

BACKGROUND

Cholera, an ancient scourge, continues to inflict high rates of mortality today. The rising incidence of epidemics in areas of poor sanitation and crowding highlight the need for better epidemic prevention and early response. Such interventions require the availability of rapid and accurate diagnostic techniques to trigger timely response and mitigate the scale of the outbreak. The current gold standard of bacterial culture is inadequate for rapid diagnosis, highlighting the overarching neglect of field diagnostic needs. This paper was written to support the World Health Organisation's Global Task Force on Cholera Control mandated Cholera and diarrhoeal disease laboratory Network (CholdiNet) in devising a protocol for the validation of Rapid Diagnostic Tests (RDTs) for Vibrio cholerae. The status of diagnostic tools for Vibrio cholerae is assessed, describing products that have been commercialised over the last two decades and discussing their peer-reviewed evaluation.

METHOD

Review of post-1990 peer-reviewed and grey literature on rapid diagnostic tests for Vibrio cholerae.

RESULTS

Since 1990, twenty four diagnostic tests have been developed for the detection of Vibrio cholerae in human faecal samples. Fourteen of these have also been described in the literature, with rapid chromatographic-immuno assays (CIA) featuring strongly. Polymerase chain reaction (PCR) assays maintain the ability to detect the lowest amount of bacteria; however CIAs achieve both low detection thresholds and high sensitivity and specificity, making them possible candidates for use in field conditions. Field and laboratory studies were performed in a wide range of settings demonstrating variability in performance, however only a few of these studies were sufficiently stringent, highlighting five RDTs that showed promise in field conditions; COAT, IP cholera dipstick, SMART, IP dipstick and Medicos. In light of non-independent reporting, the authors would like to see these five products undergoing additional studies, with further technical improvements if needed and commercial production. The authors hope that public health use of such a RDT in limited-resource field conditions on stool samples may contribute to effective reduction in cholera epidemic spread.

[Bacteriological tests for tuberculosis]

This review describes current developments for the bacteriological diagnosis of active tuberculosis. It deals mainly with molecular methods, describing their performance and how they can be integrated into more traditional diagnostic approaches. At present, microscopic examination and culture are still essential for the diagnosis of TB and to guide therapeutic decisions. Nucleic acid amplification and line probe assays speed up the identification and susceptibility testing of mycobacteria in AFB smear positive specimens or in culture. They are also efficient for comparison of M. tuberculosis strains with each other (genotyping). On the other hand, at present, molecular tests are not applicable for diagnosis in smear negative specimens and even less so for diagnosis of culture-negative tuberculosis. The use of serology for antibody/antigen detection is not useful and it is not appropriate to assays based on the release of interferon-γ release as they are currently available. Notable progress has been made but more sensitive diagnostic tests for TB are still urgently needed.

The evolving field of imaging mass spectrometry and its impact on future biological research

Within the past decade, imaging mass spectrometry (IMS) has been increasingly recognized as an indispensable technique for studying biological systems. Its rapid evolution has resulted in an impressive array of instrument variations and sample applications, yet the tools and data are largely confined to specialists. It is therefore important that at this junction the IMS community begin to establish IMS as a permanent fixture in life science research thereby making the technology and/or the data approachable by non-mass spectrometrists, leading to further integration into biological and clinical research. In this perspective article, we provide insight into the evolution and current state of IMS and propose some of the directions that IMS could develop in order to stay on course to become one of the most promising new tools in life science research.

Emerging trends in the diagnosis of tuberculosis--RNTCP and beyond

Though the Koch's bacillus was discovered 128 years ago, still there lies some dilemma in its diagnosis in certain clinical situations. Here in this article two basic approaches have been described for its diagnosis. One is the 'direct' approach in which detection of mycobacteria or its products is done, the other being 'indirect' approach, which includes measurements of humoral and cellular responses of the host against tuberculosis. 'Direct' methods include sputum smear microscopy, culture and molecular amplification methods. The 'indirect' methods include antibody detection, antigen defection, cellular immunity mediated tests and biochemical assays. All the methods have been narrated in a nutshell in this article.

[Approaches to improvement of laboratory diagnosis of infectious diseases]

Modern routine and novel techniques for diagnostics of infectious diseases and identification of intoxication syndrome markers are reviewed. Also presented are results of original studies of mixed intestinal infections and methods of their rapid differential diagnostics.

Molecular approaches: advantages and artifacts in assessing bacterial diversity

Bacteria account for a major proportion of Earth's biological diversity. They play essential roles in quite diverse environments and there has been an increasing interest in bacterial biodiversity. Research using novel and efficient tools to identify and characterize bacterial communities has been the key for elucidating biological activities with potential for industrial application. The current approach used for defining bacterial species is based on phenotypic and genomic properties. Traditional and novel DNA-based molecular methods are improving our knowledge of bacterial diversity in nature. Advances in molecular biology have been important for studies of diversity, considerably improving our knowledge of morphological, physiological, and ecological features of bacterial taxa. DNA-DNA hybridization, which has been used for many years, is still considered the golden standard for bacteria species identification. PCR-based methods investigating 16S rRNA gene sequences, and other approaches, such as the metagenome, have been used to study the physiology and diversity of bacteria and to identify novel genes with potential pharmaceutical and other biotechnological applications. We examined the advantages and limitations of molecular methods currently used to analyze bacterial diversity; these are mainly based on the 16S rRNA gene. These methods have allowed us to examine microorganisms that cannot be cultivated by routine methods and have also been useful for phylogenetic studies. We also considered the importance of improvements in microbe culture techniques and how we can combine different methods to allow a more appropriate assessment of bacterial diversity and to determine their real potential for industrial applications.

[New diagnosis tools for tuberculosis laboratory network in Latin America]

Feasibility of rapid and sustainable diagnostic methods that provide useful and timely results to guide the clinical control of tuberculosis patients was analyzed. However, policies guiding the insertion of new diagnostics in the laboratory services that support the tuberculosis control are lacking in developing countries. The introduction of these methods in developing countries laboratories requires rational policies guiding the application of these technologies. In the last few years, some automated systems for culture and molecular testing in laboratory services for tuberculosis diagnosis, which offered accuracy and speed, have been reported. However, their implementation is restricted because of costly resources, logistics and infrastructure. Recently, various economically feasible tests have demonstrated to be applicable in poor-resource labs. The detection of adenosine desaminase (ADA) in pleural fluid is a valuable low-cost approach to the diagnosis of tuberculosis. On the other hand, the microscopic detection of Mycobacterium tuberculosis using thin layer agar is a moderate cost alternative method. Drug susceptibility testing to antituberculous drugs can be expedited by the nitrate reduction assay in tuberculosis laboratories using routine procedures for tuberculosis diagnosis.

Recent advances in the diagnosis of childhood tuberculosis

Children account for a major proportion of the global tuberculosis disease burden, especially in endemic areas. However, the accurate diagnosis of childhood tuberculosis remains a major challenge. This review provides an overview of the most important recent advances in the diagnosis of intrathoracic childhood tuberculosis: (1) symptom-based approaches, including symptom-based screening of exposed children and symptom-based diagnosis of active disease; (2) novel immune-based approaches, including T cell assays and novel antigen-based tests; and (3) bacteriological and molecular methods that are more rapid and/or less expensive than conventional culture techniques for tuberculosis diagnosis and/or drug-resistance testing. Recent advances have improved our ability to diagnose latent infection and active tuberculosis in children, but establishing a diagnosis of either latent infection or active disease in HIV-infected children remains a major challenge, particularly in high-burden settings. Although improved access to diagnosis and treatment is essential, ultimately the burden of childhood tuberculosis is determined by the level of epidemic control achieved in a particular community. Several recent initiatives, in particular the United Nations Millennium Developmental Goals, deal with the problem of poverty and disease in a holistic fashion, but global political commitment is required to support these key initiatives.

[Bacterial keratitis. Current diagnostic aspects]

Keratitis remains the third most common etiology for blindness worldwide. Whereas bacteria still predominate as causative organisms in temperate climates, fungal and mixed infections are more common in tropical and semitropical areas. In recent years, a shift in the causative organisms, as well as predisposing factors, has been reported. Risk factors that may have gained in importance, such as wearing contact lenses and corneal surgery, have been identified. Microorganisms, especially Pseudomonas spp. and mycobacteria have been frequently isolated in these patients. A changing pattern in microorganism infection has been observed that might be caused by inappropriate use of potent antimicrobial agents. Because of the sight threatening nature of bacterial keratitis, proper diagnosis and antibiotic selection are required. Management should be guided by the appropriate diagnosis, severity of clinical symptoms and underlying risk factors. Molecular techniques, such as polymerase chain reaction, have increased our diagnostic options, even when they cannot replace established procedures. This article reviews the current data and procedures available for the diagnosis of bacterial keratitis.

[The direct diagnosis of syphilis--modern standards and directions of development]

The methods of direct diagnosis of syphilis developed slowly, in contrast to dynamic development of serological diagnosis of the disease. The authors present modern modes of identification of Treponema pallidum and directions of their modifications. The cultivation of Treponema pallidum in vitro, the different methods of nucleic acids amplifications and their practical application are discussed.

[Experience in improving the microbiological diagnosis of tuberculosis in the Kemerovo Region]

Measures to improve the organization of microbiological diagnosis of tuberculosis and to upgrade its quality have been implemented in the Kemerovo Region. The regional reference laboratory has been reconstructed in accordance with the international standards. Inter-regional centers for microbiological diagnosis of tuberculosis have been set up on the basis of large tuberculosis treatment facilities. Sputum microscopy centers have been opened on the basis of general medical service. A multileveled system for surveillance of laboratories and their staff training has been established. The work done has significantly improved the coverage of those who are to be studied and the quality of microbiological diagnosis.

Bacterial taxonomics: finding the wood through the phylogenetic trees

Bacterial taxonomy comprises systematics (theory of classification), nomenclature (formal process of naming), and identification. There are two basic approaches to classification. Similarities may be derived between microorganisms by numerical taxonomic methods based on a range of present-day observable characteristics (phenetics), drawing in particular on conventional morphological and physiological test characters as well as chemotaxonomic markers such as whole-cell protein profiles, mol% G+C content, and DNA-DNA homologies. By contrast, phylogenetics, the process of reconstructing possible evolutionary relationships, uses nucleotide sequences from conserved genes that act as molecular chronometers. A combination of both phenetics and phylogenetics is referred to as polyphasic taxonomy, and is the recommended strategy in description of new species and genera. Numerical analysis of small-subunit ribosomal RNA genes (rDNA) leading to the construction of branching trees representing the distance of divergence from a common ancestor has provided the mainstay of microbial phylogenetics. The approach has some limitations, particularly in the discrimination of closely related taxa, and there is a growing interest in the use of alternative loci as molecular chronometers, such as gyrA and RNAase P sequences. Comparison of the degree of congruence between phylogenetic trees derived from different genes provides a valuable test of the extent they represent gene trees or species trees. Rapid expansion in genome sequences will provide a rich source of data for future taxonomic analysis that should take into account population structure of taxa and novel methods for analysis of nonclonal bacterial populations.

Mycobacteraemia among HIV-1-infected patients in São Paulo, Brazil: 1995 to 1998

From July 1995 to August 1998, mycobacterial blood cultures were obtained from 1032 HIV-infected patients seen at the Centro de Referência e Treinamento de AIDS (CRTA), Hospital São Paulo (HSP), and Centro de Referência de AIDS de Santos (CRAS). Overall, 179 episodes of mycobacteraemia were detected: 111 (62.0%) at CRTA, 50 (27.9%) at HSP, and 18 (10.1%) at CRAS. The frequency of positive cultures declined sharply from 22.6% in 1995 to 6.9% in 1998, consistent with the decrease in opportunistic infections following the publicly funded distribution of highly active antiretroviral therapy. In 1995, mycobacteraemia was more frequently due to Mycobacterium avium complex (59.2%) than Mycobacterium tuberculosis (28.6%), whereas in 1998 the relative frequencies were reversed (28.6 vs. 64.3% respectively), probably justified by the increased virulence of M. tuberculosis and the greater risk of invasive infection in less-immunocompromised patients, including patients unaware they are infected with HIV.

[Fast tests in bacteriology]

Advances in biotechnologies and miniaturization over the past few decades have led to an explosion in the number of rapid tests in in vitro diagnosis and explain their ever-growing presence in international markets. Although based on classic immunological and biochemical methods, these tests deliver many more benefits for laboratories. They are rapid and simple to perform, provide results rapidly and can be performed in remote laboratories, making them invaluable for both routine and emergency analyses. As beneficial as they may be, however, they still have a long way to go before they find widespread use in infectious disease control. Currently, rapid testing methods are used only to screen for urinary tract infections, monitor certain infectious parameters and make more accurate diagnosis of a still small number of species of bacteria. This narrow catalogue of available tests is yet another disadvantage in a list of drawbacks typically associated with rapid tests. A good portion of complaints centers on the fact that they are still too recent to have sufficient information on their levels of sensitivity and reliability. Furthermore, regulations, in particularly concerning accountability, remain to be established. Nevertheless, constant innovation coupled with the experience of laboratory professionals in the field should open the way for rapid testing to earn its place in the line-up of medical laboratory tests.

High-density cell microarrays for parallel functional determinations

Whole-genome sequencing projects have generated a wealth of gene sequences from a variety of organisms. A major challenge is to rapidly uncover gene regulatory circuits and their functional manifestations at the cellular level. Here we report the coupled fabrication of nanocraters ranging in size from 100 pL to 1.5 nL on permeable membranes for culturing cells. Using this approach, we developed bacterial and yeast cell microarrays that allowed phenotypic determinations of gene activities and drug targets on a large scale. Cell microarrays will therefore be a particularly useful tool for studying phenotypes of gene activities on a genome-wide scale.

Flow cytometry of bacteria: glimpses from the past with a view to the future

Measurement of bacteria and other microorganisms at the level of single cells has progressed enormously over the last couple of decades. Up to the late 1970s, there were no other means than microscopy for observation of single microorganisms, making any type of measurement very cumbersome and tedious, at best. Today, we measure several parameters simultaneously with a precision of a few per cent, and at a rate of 1000 cells per second. The first papers on the use of flow cytometry to measure bacteria appeared only in 1977, although the method had proved highly successful in studies of mammalian cells for almost a decade. There were several reasons for this relatively late introduction, including technical limitations, problems with adequate staining, and, not least, the human factor. Today, flow cytometry has a wide range of microbiological applications, ranging from studies of the bacterial cell cycle and many other cellular characteristics to assessment of antibiotic susceptibility of clinical samples, and monitoring of bacteria and other microorganisms in anything from sewage to sea water. Still, the potential of flow cytometry in microbiology is far from fully utilised. Better instruments and new stains will provide new opportunities to understand, control and exploit this vital part of the biosphere.

Changing trends in the laboratory diagnosis of gastroenteritic infections

The micro-organisms responsible for causing gastroenteritis have changed over the last few decades. This article chronicles those changes and describes the laboratory tests devised to improve diagnosis.

Tuberculosis in the 1990's: From bedside to bench and back

Since the mid-1980s, the rate of new cases of tuberculosis (TB) diagnosed in Canada ceased to follow a downward trend, and has instead stabilized at approximately 7 cases/100,000 population. In the United States, a similar trend emerged, such that in the early 1990s there was an increase in new cases of TB. Outbreaks of drug-resistant TB also occurred with devastating clinical impact. These observations prompted laboratories to re-examine their role in halting the spread of TB. Laboratories play a critical part in the diagnosis of TB; procedures must be optimized to provide rapid and accurate results. This review discusses the role of the mycobacteriology laboratory in the diagnosis of TB, and how new technologies available today have enhanced the ability of the laboratory to provide timely, efficient and accurate results.

Secular trends in incidence and mortality of bacteraemia in a Danish county 1981-1994

We estimated the incidence and mortality of bacteraemia in the County of North Jutland and examined factors that could explain the changes observed. A population-based survey of bacteraemia was conducted in the Danish County of North Jutland during 1981-1994. Data were retrieved from a regional bacteraemia register. The mortality was determined through linkage to the Danish Civil Registration System. A total of 7198 bacteraemias were detected, and the annual incidence increased from 76 per 100,000 person-years in 1981 to 153 in 1994. One major determining factor was a change in blood culture system with a higher volume of blood per sample, but annual numbers of blood cultures also increased. The 30-day mortality rate increased from 17 to 40 per 100,000 person-years during the study period, whereas the case-fatality rate remained constant (23.6%; 95% confidence intervals 22.6%-24.6%). The number of bacteraemias increased significantly. This observation could be explained only partly by changes in demography, in blood culture system, and in diagnostic activity. The case fatality rate remained constant despite the fact that more people were diagnosed with bacteraemia; this indicates that, with recent blood culture practice, more clinically significant bacteraemias are diagnosed.

Flow cytometry and bacterial pathogenesis

Our understanding of microbial adaptations to diverse and threatening environments is limited by the assumption that the behavior of individual bacteria can be accurately determined by measuring the behavior of populations. Recent advances in gene expression reporter systems, fluorescence microscopy and flow cytometry allow microbiologists to explore the complex interactions between bacteria and their environment with single cell resolution. The application of these technologies has been particularly useful in systems, such as host-pathogen interactions, where genetic analysis is often cumbersome. Recently, flow cytometry is increasingly being applied to study host-pathogen interactions.

Mycobacteriology laboratory

This review summarizes the most important features of different mycobacterial species, and addresses the issues of specimen collection and shipment, bacteriological diagnosis of tuberculosis and other mycobacterial infections, and drug susceptibility testing of different mycobacteria. Special emphasis is placed on the expected turnaround time for the various laboratory reports from different methods. The potential of new methods of today and tomorrow to expedite laboratory results are discussed.

Quality improvement of diagnostic microbiology through a peer-group proficiency assessment program. A 20-year experience in Ontario. The Microbiology Committee

OBJECTIVE

To evaluate the microbiology laboratory performance in Ontario over a 20-year period of participation in a quality assessment program and to assess the impact of quality improvement strategies.

DESIGN

Longitudinal review of isolation, identification, and antimicrobial susceptibility testing of bacteria from lyophilized, simulated patient samples.

SETTING

Ontario medical laboratories, licensed by the Ministry of Health, have been subjected to mandatory testing by the Laboratory Proficiency Testing Program of the Ontario Medical Association since 1974. Survey reports, information bulletins, correspondence, on-site consultations, educational assistance tutorials, and teleconference education are used as quality improvement strategies.

PARTICIPANTS AND INTERVENTIONS

Laboratories were subjected annually to 20 external quality assessment challenges. Performance was assessed against consensus reference values. Single survey and cumulative profiles were reviewed by a peer-group panel for acceptable or unacceptable performance. Specific interventions are used to improve collective and individual laboratory performance.

RESULTS

The number of microbiology laboratories declined from 335 in 1974 to 190 in 1994. Twenty-one percent failed expected performance standards on initial review. One hundred forty-two on-site consultations and 61 educational assistance tutorials have been provided. Twenty-five laboratories were declared nonproficient. Since 1989, 50% of the laboratories have scored at or above 80% for isolation and identification, but 25% have scored at or below 50% on susceptibility testing, and 10% or fewer have scored at or above 80%. Poor susceptibility testing performance is due to inappropriate agent selection, not testing errors.

CONCLUSIONS

The emphasis of the Laboratory Proficiency Testing Program is on quality improvement, not punishment. Performance has improved, but poor performers have the same characteristics as in 1974. Identification to species is common owing to the use of commercial systems. Automated susceptibility testing has increased to 45% of participants.

Mycobacterial testing in clinical laboratories that participate in the College of American Pathologists Mycobacteriology Surveys. Changes in practices based on responses to 1992, 1993, and 1995 questionnaires

OBJECTIVE

To determine whether the trend of increasing use of rapid methods of mycobacterial testing among participants in the College of American Pathologists (CAP) Mycobacteriology E Proficiency Testing Survey noted between 1992 and 1993 continued through 1995, and to collect information concerning mycobacterial staining and culture protocols from laboratories that do limited mycobacterial testing.

METHODS

The 1993 CAP E Survey questionnaire addressing mycobacterial laboratory practices, test volumes, and rate of recovery of drug-resistant Mycobacterium tuberculosis was included with the CAP 1995 E-A Survey. A shortened list of these same questions, excluding those addressing mycobacterial identification and susceptibility test methods, was added to the CAP 1995 E1-A Survey, to which laboratories that do limited mycobacterial testing subscribe.

RESULTS

A total of 802 and 1490 participants in the E and E1 surveys, respectively, returned responses to the CAP by the cutoff date for data analysis. For E Survey participants who answered questions concerning test methods in the years being compared, the percentage who used rapid techniques increased significantly over the study period. More participants used the fluorochrome stain (58% in 1992, 62% in 1993, and 72% in 1995), BACTEC TB plus a solid medium for culture (36% in 1992, 42% in 1993, and 50% in 1995), DNA probes for identification of M tuberculosis (68% in 1993, 79% in 1995), and BACTEC TB for susceptibility testing (65% in 1993, 71% in 1995). The percentages of E1 Survey participants who used a fluorochrome stain for detection of acid-fast bacilli and both a liquid and a solid medium for mycobacterial culture were lower than the percentages of E Survey participants who used these methods. Among participants who responded in all years being compared, the percentage processing respiratory specimens at least 7 times per week increased from 26% in 1992 to 30% in 1993 and 43% in 1995 (P < .001), and the percentages reporting an identification of M tuberculosis within 21 days and susceptibility test results within 28 days increased significantly over the study period (29% in 1992, 40% in 1993, and 56% in 1995 for identification; 13% in 1992, 19% in 1993, and 30% in 1995 for susceptibility testing). Turnaround times for E Survey participants were significantly shorter than those for E1 Survey participants. The number of specimens tested per month appeared to remain relatively stable between 1993 and 1995; however, the number of new patients with tuberculosis and the number of known tuberculosis patients with positive cultures declined significantly.

CONCLUSIONS

The recent emphasis placed on utilization of rapid methods of mycobacterial testing appears to have influenced laboratories that subscribe to the CAP E Survey. Significantly more of these laboratories were following the Centers for Disease Control and Prevention's recommendations in 1995 than in 1993 and 1992. However, many laboratories that provide only limited mycobacterial testing still have not adopted the more rapid techniques. Because tuberculosis remains a public health problem, the efforts directed at its control must not wane if the recent downward trend in incidence is to be maintained.

High cell-density culture of Escherichia coli

Escherichia coli is the most widely used prokaryotic system for the synthesis of heterologous proteins. Once an optimal expression system has been constructed, protein production can be enhanced by increasing the production of protein per cell per unit time (specific productivity), or by increasing the cell concentration per unit time (cell productivity). Various high cell-density culture (HCDC) techniques have been developed for growing recombinant and non-recombinant E. coli strains in fed-batch cultures at concentrations greater than 100 grams (dry cell weight) per liter. This article reviews the problems encountered in HCDC of E. coli, and discusses various solutions. Feeding strategies for HCDC of E. coli, and the results obtained using them, are also described.

Laboratory diagnosis of tuberculosis: past, present, and future

Resurgence of tuberculosis justifies extraordinary efforts to expedite TB diagnosis and susceptibility testing. This demands that laboratory support expand to a "second generation" of methods and procedures, including rapid availability of fluorochrome smears of concentrated specimens, faster techniques for detection (e.g., the BACTEC radiometric broth system and microcolony detection), quicker identification (e.g., high-pressure liquid chromatography, nonisotopic genetic probes), more rapid susceptibility testing methods (e.g., BACTEC), and reporting of these results as critical values. Guidelines have been established for turnaround time for results of smears, TB organism identification, and susceptibility testing to usual first-line drugs. A "third generation" of laboratory techniques soon will make testing not only more effective but also more efficient. These methods include direct testing of respiratory specimens through nonisotopic genetic probes as well as nucleic acid amplification techniques utilizing polymerase chain reaction (PCR) and other molecular procedures. These new procedures and protocols place heavy demands on laboratory test volume, technologist time and costs. For the healthcare system or clinical laboratory without the resources to deal with these new demands, referral of TB specimens represents a reasonable alternative, as long as transport is adequate to meet current CDC and other guidelines for turnaround time.

[Status and developmental trends in the use of fluorescence microscopy studies in microbiology]

There are many applications for fluorescence microscopy in the field of microbiology for diagnostic and scientific purposes. Autofluorescence as well as secondary fluorescence induced by staining of specimen with fluorochromes or with fluorochrome labeled antibodies are used for detection and differentiation of microorganisms. Small demands for object preparation and short test times are advantages for screening tests. During the last time considerable progresses in methods and technical equipments are noticeable and offer numerous new applications for fluorescence microscopy. New microscopes show clearly increased intensity of excitation. This requires a selection of object slides and cover glasses with lowest autofluorescence, blocking of fading by addition of PPD to embedding medium and a better adaptation of filters for excitation and fluorescence to the characteristics of fluorochromes. Multiple fluorochroming and combined application of fluorescence and alternative contrast techniques such as phase contrast are of rising importance in practice.