Microarrays for bacterial pathogens—hope or hype?

Despite advances in the treatment of infectious disease, pathogenic bacteria still represent one of the most important threats to human health worldwide. Many infectious disease agents have never been controlled, or have re-emerged as global pathogens, while others pose a new threat. Media and scientific attention has focused on a range of problems, including the alarming spread of antibiotic resistance, the threat of bioterrorism, microbial contamination of food, the global resurgence of tuberculosis, and other emerging and re-emerging infections triggered by lifestyle, political, economic and ecological changes. It is also becoming increasingly clear that bacteria have a causative role in major diseases such as cancer (e.g. Helicobacter pylori and gastric cancer) and heart disease (e.g. Chlamydia pneumoniae). The need to gain an integrated and comprehensive understanding of the workings of our old bacterial adversaries is as great as ever. Do DNA microarrays provide the hope? DNA microarrays are the current tool for highthroughput hybridization analysis. Generally they consist of amplified gene fragments representing individual genes that are robotically printed on suitably coated glass slides. There two principal experiments that can be performed with microarrays, hybridization of DNA (often referred to as genomotyping) or hybridization of mRNA (expression analysis). Much hype has surrounded the application and exploitation of DNA microarrays, particularly expression analysis, where it was hoped that it would be possible to monitor at a glance the temporal and spatial expression of all pathogen and host genes during infection. Not too long ago there were more reviews on the subject than original articles. So what is the reality?