[Resistance to a causative agent of infection and immune response]

An analytical literature review dealing with the problems of resistance to causative agents of infections. The review includes the data of experimental research, as well as the author's own immunological studies in children at the clinic of acute infections. Mechanisms of resistance at different phases of the infectious process, the multivalued role of Th1- and Th2-dependent responses in different infections, the role of vaccinal immunity in the resistance of children to the causative agents of vaccine-preventable infections (diphtheria and parotitis) are analyzed.

Compilation of a MALDI-TOF mass spectral database for the rapid screening and characterisation of bacteria implicated in human infectious diseases

A database of MALDI-TOF mass spectrometry (MS) profiles has been developed with the aim of establishing a high throughput system for the characterisation of microbes. Several parameters likely to affect the reproducibility of the mass spectrum of a taxon were exhaustively studied. These included such criteria as sample preparation, growth phase, culture conditions, sample storage, mass range of ions, reproducibility between instruments and the methodology prior to database entry. Replicates of 12 spectra per sample were analysed using a 96-well target plate containing central wells for peptide standards to correct against mass drift during analysis. The quality of the data was assessed statistically prior to database addition using root mean squared values of <3.0 as the criterion for rejection. Cluster analysis using a nearest neighbour algorithm also enabled subsets of data to be compared. This was achieved using the bespoke MicrobeLynx trade mark software. Columbia blood agar was used to standardise all procedures for the database, since it permitted the culture of most human pathogens and also produced spectra with a broad range of mass ions. In some instances, alternative media such as CLED were used in specific studies with greater success. Following standardisation of the procedure, a database was developed comprising ca. 3500 spectra with multiple strain entries for most species. The results to date show unequivocally that as the number of strains per species increased, so too did the success of species matching. The technique demonstrated unique mass spectral profiles for each genus/species, with the variation in mass ions among strains/species being dependent on the intra-specific diversity. The success of identification against the database for wild-type strains ranged between 33 and 100%; the lower percentage results being generally associated with poor representation of some species within the database. These findings provide a new dimension for the rapid and high throughput characterisation of human pathogens with potentially broad applications across the field of microbiology.

Update on antimicrobial resistance

WHO experts believe that antimicrobial resistance is potentially containable, but the window of opportunity to control and eventually eliminate the most dangerous infectious diseases is closing. If we miss our opportunity, it may become very difficult and expensive--and in some cases impossible--to treat infectious diseases. WHO's global strategy to contain antimicrobial resistance requires a massive effort and an alliance among countries, governments, international organizations, drug manufacturers, and private and public health care sectors. If infectious diseases are fought wisely and widely by the international community, drug resistance can be controlled and lives saved.

[Infectious diseases in the ambulatory care setting]

Hot topics in infectiology mainly include emerging diseases, particularly those caused by antibiotic-resistant bacteria. Prudent use of antibiotics is therefore mandatory. Among new classes of antibiotics for outpatients therapy are linezolid (for resistant, Gram-positive bacterial, and telithromycine (for treatment of respiratory tract infections). This review also addresses the following topics: short course of doxycycline for treatment of early Lyme disease in adults, recommendations against the widespread use of fluoroquinolones for community-acquired pneumonia, prevention of Herpes simplex type 2 transmission with valacyclovir, management of acute, symptomatic hepatitis C, and the absence of an established link between vaccines and chronic diseases.

Fighting Infection

Since the beginning of time, infections have been a major cause of disability and death of humans in every part of the world. For centuries, little was known about what caused infection, how to prevent infection, or how to cure infection. With the discovery of sulfa and penicillin in the 1930s, the ability to fight infection became reality. During the next six decades, antimicrobials were developed to fight bacterial, fungal, and viral infections. It truly seemed as if the battle against infection was won, until the rapid and global spread of drug resistance began to threaten the effectiveness of all currently available antimicrobials. A new phase of the war against infection began, and the search for methods of reducing the spread of drug resistance began. Today, it is apparent that identifying the agents of infection, understanding how antimicrobials are targeted against specific infectious organisms, and practicing the judicious application of antimicrobials will help reduce the threat of continued escalation of antimicrobial resistance. Part 1 of this three-part series will provide an overview of how antimicrobials are designed to target specific agents of infection and how drug resistance develops. Parts 2 and 3 will examine individual antibacterial, antifungal, and antiviral agents and the recommendations for their appropriate use.

When your patients are itching to see you: not all hives are urticaria

When patients present with itching and the perception that they have hives, what other processes can mimic urticaria? With the exception of urticarial vasculitis, urticaria typically lasts less than 24 to 36 hours at one site. A rash that persists longer should raise the suspicion of another inflammatory process. When the hive-like rash does not respond to antihistamines, a biopsy may reveal an alternative diagnosis. All biopsies should also be submitted for immunofluorescence to exclude atypical presentations of inflammatory bullous disease presenting with urticaria. However, even biopsies can be subject to misinterpretation and if the clinical picture does not support the biopsy, an alternative consultation with a dermatopathologist may be required. The extent of the laboratory and radiologic evaluation should be dictated by the clinician's suspicion of alternative causes for the hive(s) because rarely malignancies may present with urticaria. Common things are indeed common with urticaria and the more urticaria does not appear to be typical, the more often the clinician should consider alternative diagnoses.

[Molecular paleopathology: a novel perspective for biomedical history]

Molecular paleopathology is an emerging field that is devoted to the detection, indentification and characterization of the molecular signatures in past diseases. When studied with modern molecular techniques, ancient human remains may yield direct informations on the diseases of ancient populations as well as the history of human diseases. Data concerning specific diseases of infectious, neoplastic and genetic origin can be obtained by molecular investigations of skeletal and mummified human remains. In particular, ancient DNA extracted from bone tissue, teeth and mummified soft tissue can be deeply analyzed by using PCR-based molecular techniques. Additionally, DNA of ancient pathogens, including bacteria, viruses and parasites, can be isolated from human remains and molecular diagnosis of infectious diseases can be made. Thus, molecular data, complemented by morphological and biochemical analyses, could help to reconstruct the epidemiology of past diseases and epidemics.

Rapid, species-specific detection of uropathogen 16S rDNA and rRNA at ambient temperature by dot-blot hybridization and an electrochemical sensor array

Development of rapid molecular approaches for pathogen detection is key to improving treatment of infectious diseases. For this study, the kinetics and temperature-dependence of DNA probe hybridization to uropathogen species-specific sequences were examined. A set of oligonucleotide probes were designed based on variable regions of the 16S gene of the Escherichia coli, Proteus mirabilis, Klebsiella oxytoca, and Pseudomonas aeruginosa. A universal bacterial probe and probes-specific for gram-positive and gram-negative organisms were also included. The oligonucleotide probes discriminated among 16S genes derived from 11 different species of uropathogenic bacteria applied to nylon membranes in a dot-blot format. Significant binding of oligonucleotide probes to target DNA and removal of nonspecific binding by membrane washing could both be achieved rapidly, requiring as little as 10 min. An oligonucleotide probe from the same species-specific region of the E. coli 16S gene was used as a capture probe in a novel electrochemical 16-sensor array based on microfabrication technology. Sequence-specific hybridization of target uropathogen 16S rDNA was detected through horseradish peroxidase acting as an electrochemical transducer via a second, detector probe. The sensor array demonstrated rapid, species-specific hybridization in a time course consistent with the rapid kinetics of the dot-blot hybridization studies. As in the dot-blot hybridization studies, species-specific detection of bacterial nucleic acids using the sensor array approach was demonstrated both at 65 degrees C and at room temperature. These results demonstrate that molecular hybridization approaches can be adapted to rapid, room temperature conditions ideal for an electrochemical sensor array platform.

Inhaling to mitigate exhaled bioaerosols

Humans commonly exhale aerosols comprised of small droplets of airway-lining fluid during normal breathing. These "exhaled bioaerosols" may carry airborne pathogens and thereby magnify the spread of certain infectious diseases, such as influenza, tuberculosis, and severe acute respiratory syndrome. We hypothesize that, by altering lung airway surface properties through an inhaled nontoxic aerosol, we might substantially diminish the number of exhaled bioaerosol droplets and thereby provide a simple means to potentially mitigate the spread of airborne infectious disease independently of the identity of the airborne pathogen or the nature of any specific therapy. We find that some normal human subjects expire many more bioaerosol particles than other individuals during quiet breathing and therefore bear the burden of production of exhaled bioaerosols. Administering nebulized isotonic saline to these "high-producer" individuals diminishes the number of exhaled bioaerosol particles expired by 72.10 +/- 8.19% for up to 6 h. In vitro and in vivo experiments with saline and surfactants suggest that the mechanism of action of the nebulized saline relates to modification of the physical properties of the airway-lining fluid, notably surface tension.

Global Infectious Diseases and Epidemiology Network (GIDEON): a world wide Web-based program for diagnosis and informatics in infectious diseases

The Global Infectious Diseases and Epidemiology Network (GIDEON) (http://www.gideononline.com) consists of 4 modules. The first is designed to generate a ranked differential diagnosis list for any infectious diseases scenario in any of 220 countries. The second follows the country-specific epidemiology of 337 individual diseases. The third presents a comprehensive encyclopedia of 308 generic anti-infective drugs and vaccines, including a listing of >9500 trade names. The fourth generates a ranked identification list based on the phenotype of bacteria, mycobacteria, and yeasts. The program performs well and serves as a useful paradigm for World Wide Web-based informatics. GIDEON is an eclectic program that can serve the needs of clinicians, epidemiologists, and microbiologists working in the fields of infectious diseases and geographic medicine.

Cluster formation for multi-strain infections with cross-immunity

Many infectious diseases exist in several pathogenic variants, or strains, which interact via cross-immunity. It is observed that strains tend to self-organise into groups, or clusters. The aim of this paper is to investigate cluster formation. Computations demonstrate that clustering is independent of the model used, and is an intrinsic feature of the strain system itself. We observe that an ordered strain system, if it is sufficiently complex, admits several cluster structures of different types. Appearance of a particular cluster structure depends on levels of cross-immunity and, in some cases, on initial conditions. Clusters, once formed, are stable, and behave remarkably regularly (in contrast to the generally chaotic behaviour of the strains themselves). In general, clustering is a type of self-organisation having many features in common with pattern formation.

Peptide-protein microarrays for the simultaneous detection of pathogen infections

We describe novel peptide-protein microarrays, which were fabricated using semicarbazide glass slides that permitted the immobilization of glyoxylyl peptides by site-specific ligation and the immobilization of proteins by physisorption. The arrays permitted the simultaneous serodetection of antibodies directed against hepatitis C virus (HCV core p21 15-45 peptide, NS4 1925-1947 peptide, core, NS3, NS4, and mixture of core, NS3, NS4, and NS5 antigens), hepatitis B virus (HBc, HBe, and HBs), human immunodeficiency virus (Gp41 and Gp120 for HIV-I and Gp36 for HIV-II), Epstein-Barr virus (VCAp18 153-176 peptide), and syphilis (rTpN47 and rTpN17) antigens using an immunofluorescence assay. Peptide-protein microarrays displayed high signal-to-noise ratios, sensitivities, and specificities for the detection of antibodies as revealed by the analysis of a collection of human sera referenced against these five pathogens.

The global mortality of infectious and parasitic diseases in children

Although considerable advances in the reduction of global child morbidity and mortality have been made since 1970, when more than 17 million children died, the burden of child mortality is still intolerably high today. An estimated 10.5 million younger than the age of 5 years died in the year 2002 from largely preventable diseases, such as those having infectious, parasitic, and perinatal causes. The reductions in rates of mortality observed did not take place uniformly across time and regions of the world, but the success stories in developing countries demonstrate clearly that low mortality levels are achievable in those settings. If the whole world came to share the current child mortality experience of Northern European countries, more than 10 million deaths of children could be prevented each year. This work aims to answer the questions concerning where and why so many of the world's children still succumb to largely preventable causes.

The effect of treatment on pathogen virulence

The optimal virulence of a pathogen is determined by a trade-off between maximizing the rate of transmission and maximizing the duration of infectivity. Treatment measures such as curative therapy and case isolation exert selective pressure by reducing the duration of infectivity, reducing the value of duration-increasing strategies to the pathogen and favoring pathogen strategies that maximize the rate of transmission. We extend the trade-off models of previous authors, and represents the reproduction number of the pathogen as a function of the transmissibility, host contact rate, disease-induced mortality, recovery rate, and treatment rate, each of which may be influenced by the virulence. We find that when virulence is subject to a transmissibility-mortality trade-off, treatment can lead to an increase in optimal virulence, but that in other scenarios (such as the activity-recovery trade-off) treatment decreases the optimal virulence. Paradoxically, when levels of treatment rise with pathogen virulence, increasing control efforts may raise predicted levels of optimal virulence. Thus we show that conflict can arise between the epidemiological benefits of treatment and the evolutionary risks of heightened virulence.

Inflammatory smears--is there a correlation between microbiology and cytology findings?

Cervical smear results reporting the presence of inflammation are regularly encountered by smeartakers, yet the significance of this finding is not clear. We wished to evaluate whether the presence of inflammation on smear test was associated with a higher incidence of lower genital tract infection. A retrospective review was carried out on women attending our colposcopy unit for their first visit during 2001. Results of 256 women were available for analysis. Evidence of inflammation was found in 9.7% of smears. Genital tract infection was found in 29.2% of women overall. Infection with more than one micro-organism was present in 8.9 percent. Forty eight percent of women having inflammatory changes on smear test had genital tract infection. This compared with 27.3% of women whose smear tests showed no evidence of inflammation. Prevalence of infection with Chlamydia trachomatis, Candida, Bacteroides and Gardnerella vaginalis was higher in the inflammatory smear group. This study shows that women with an inflammatory smear are more likely to harbour genital tract infection than women whose smear shows no evidence of inflammation. Chlamydia infection in particular has long-term fertility consequences through its potential to cause asymptomatic tubal damage: it was present in a substantial proportion of women with inflammation on smear (20%). Screening for lower genital tract infection via high vaginal swab and either intracervical swab or urinary screening for Chlamydia infection should be carried out in all women with smear tests reporting the presence of inflammation.

Heavy rainfall and waterborne disease outbreaks: the Walkerton example

Recent research indicates that excessive rainfall has been a significant contributor to historical waterborne disease outbreaks. The Meteorological Service of Canada, Environment Canada, provided an analysis and testimony to the Walkerton Inquiry on the excessive rainfall events, including an assessment of the historical significance and expected return periods of the rainfall amounts. While the onset of the majority of the Walkerton, Ontario, Escherichia coli O157:H7 and Campylobacter outbreak occurred several days after a heavy rainfall on May 12, the accumulated 5-d rainfall amounts from 8-12 May were particularly significant. These 5-d accumulations could, on average, only be expected once every 60 yr or more in Walkerton and once every 100 yr or so in the heaviest rainfall area to the south of Walkerton. The significant link between excess rainfall and waterborne disease outbreaks, in conjunction with other multiple risk factors, indicates that meteorological and climatological conditions need to be considered by water managers, public health officials, and private citizens as a significant risk factor for water contamination. A system to identify and project the impacts of such challenging or extreme weather conditions on water supply systems could be developed using a combination of weather/climate monitoring information and weather prediction or quantitative precipitation forecast information. The use of weather monitoring and forecast information or a "wellhead alert system" could alert water system and water supply managers on the potential response of their systems to challenging weather conditions and additional requirements to protect health. Similar approaches have recently been used by beach managers in parts of the United States to predict day-to-day water quality for beach advisories.

[Applications of PCR techniques for molecular epidemiology of infectious diseases]

The development of new PCR-based typing methods in the last years have supposed an important advance in the study of infectious diseases. Arbitrarily primed PCR (AP-PCR) and repetitive element sequence-based PCR (rep-PCR) are the most widely used PCR-based fingerprinting methods for bacteria and fungi. Major advantages of these methods are flexibility, technical simplicity and high discriminatory power. The AP-PCR presents problems of low inter-run and inter-laboratory reproducibility which make necessary the optimization of the protocol and reagents. PCR-RFLP is based in the enzymatic digestion of polymorphic genes amplified by PCR. This method is easy to perform and discriminatory, although less than AP-PCR or rep-PCR. Amplified fragment length polymorphism (AFLP) is a highly reproducible and discriminatory typing method based on the amplification by PCR of restriction fragments obtained from chromosomic DNA. This method is more discriminative and reproducible than AP-PCR, rep-PCR and PCR-RFLP, but it is more time-consuming and expensive, and requires specialised personnel. Most of these PCR-based typing methods are less time-consuming, rapid and easy to perform and of interpretation than pulsed-field gel electrophoresis (PFGE; gold standard method for typing most bacterium and fungi), but they usually are less discriminative and reproducible than PFGE, depending on the species studied and the method of PCR used. In summary, there are several PCR-based methods which are useful as a primary approach to the study of the clonal relationship among microbial isolates. The selection of the method to be used depend on technical (rapid, low time-consuming, easy to perform and to interpret, reproducible and discriminatory) and economical (low cost) factors.

Tuberculosis: from prehistory to Robert Koch, as revealed by ancient DNA

During the past 10 years palaeomicrobiology, a new scientific discipline, has developed. The study of ancient pathogens by direct detection of their DNA has answered several historical questions and shown changes to pathogens over time. However, ancient DNA (aDNA) continues to be controversial and great care is needed to provide valid data. Here we review the most successful application of the technology, which is the study of tuberculosis. This has provided direct support for the current theory of Mycobacterium tuberculosis evolution, and suggests areas of investigation for the interaction of M tuberculosis with its host.

Development of rationally designed nucleic acid signatures for microbial pathogens

The detection and identification of microbial pathogens are critical challenges in clinical medicine and public health surveillance. Advances in genome analysis technology are providing an unprecedented amount of information about bacterial and viral organisms, and hold great potential for pathogen detection and identification. In this paper, a rational approach to the development and application of nucleic acid signatures is described based on phylogenetically informative sequence features, especially single nucleotide polymorphisms. The computational tools that are available to enable the development of the next generation of microbial molecular signatures for clinical diagnostics and infectious disease surveillance are reviewed and the impact on public health and national security will be discussed.

Evolution of virulence

At the close of the 19th century, the germ theory had generated a new understanding of the causes of acute infectious diseases and revealed new directions for study. This understanding contributed to the greatest improvements in health in the history of medicine. At the end of the 20th century, the second stage of this disciplinary development is occurring. The old germ theory is being expanded into a new germ theory, which, by integrated the full spectrum of biologic disciplines. This new germ theory is emphasizing how environments and human activities influence the characteristics of infectious agents and the broader role of infection as a cause of chronic diseases.