Pathogenic bacteria utilise a number of mechanisms to cause disease in human hosts. Bacterial pathogens express a wide range of molecules that bind host cell targets to facilitate a variety of different host responses. The molecular strategies used by bacteria to interact with the host can be unique to specific pathogens or conserved across several different species. A key to fighting bacterial disease is the identification and characterisation of all these different strategies. The availability of complete genome sequences for several bacterial pathogens coupled with bioinformatics will lead to significant advances toward this goal.

Infectious diseases are the leading cause of death worldwide. Not only are new infectious diseases emerging, but the re-emergence of deadly infectious diseases, and the increasing prevalence of antimicrobial resistant strains, presents a formidable threat to public health and welfare. Recently, significant evidence has emerged which indicates that markedly different microbial pathogens use common strategies to cause infection and disease. For example, many diverse bacterial pathogens share common mechanisms in terms of their abilities to adhere, invade, and cause damage to host cells and tissues, as well as to survive host defences and establish infection. A diagrammatic overview of some of these mechanisms is given in fig 1. Many of these commonalities of infection appear to be related to the acquisition of large blocks of virulence genes from a common microbial ancestor, which can be disseminated to other bacteria via horizontal transfer. The horizontal transmission of large blocks of virulence determinants is also directly attributable to the constant emergence of new strains of bacterial pathogens, many of which are resistant to multiple antibiotics. Indeed, antibiotic resistance of bacterial pathogens has emerged as one of the most important issues facing critical care practitioners. A more thorough comprehension of the common themes in microbial pathogenicity is essential to understanding the molecular mechanisms of microbial virulence and to the development of novel vaccines and other therapeutic agents for the treatment and prevention of infectious diseases.

Some bacteria overproduce and excrete copious amounts of high molecular weight polysaccharides, also called exopolysaccharides, when isolated from clinical samples. This extracellular sugar coating is termed capsule. Different species of bacteria utilise diverse sugars to produce the capsule. Capsule production is one of the major virulence factors utilised by bacteria to evade clearance from an infectious site. Specifically, the capsule provides bacteria with protection from the host immune response as well as antibiotics.

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Microbiology: Current Research
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