Chlamydia: unlocking the secrets of a stealth pathogen
Dr Richard Hayward – a Royal Society University Research Fellow and a member of the Institute of Structural Molecular Biology at Birkbeck/UCL – presented his group’s latest findings on Chlamydia on 17 April during Science Week.
Dr Richard Hayward (right) and Professor Nick Keep. Photo: Harish Patel
Dr Hayward started with an overview of bacteria, explaining that most bacteria are good so-called commensal bacteria that coexist alongside us fine. Indeed our bodies contain more bacterial cells than human cells. Some bacteria can be bad when we are weakened and there is opportunist infection. A few bacteria are always BAD, these are the pathogens such as the bacteria that cause TB. These pathogenic bacteria secrete toxins or, as in the case of Chlamydia, have developed a syringe like mechanism to inject proteins into host cells. Dr Hayward also compared the parts of both a bacterial cell and human cell to parts of a town – the power station, the waste dump and so on.
He then focussed on Chlamydia, which is the most common sexually transmitted disease. Often infections are not noticed, but even these can lead to infertility. Chlamydia infection is also associated with pelvic inflammatory disease and cancer in women. He turned to the effect on men towards the end of the talk, where his own research in collaboration with Addenbroke’s Hospital in Cambridge has shown that Chlamydia bacteria can enter sperm and will almost certainly therefore impact on male fertility.
The National Screening Programme for Chlamydia has unfortunately had a limited effect in reducing infection according to a National Audit Office report. Persuading teenagers to reduce their sexual activity has proved to be difficult. Perhaps development of a vaccine will be a more productive approach.
In the third world Chlamydia, however, is the cause of blindness by trachoma, which is an eye infection spread by touch between family members rather than a sexually transmitted disease. The WHO S.A.F.E. programme (Surgery, Antibiotics, Facial cleanliness and Environmental change – access to clean water) is starting to positively impact on this form of infection.
The core of Dr Hayward’s was his group’s own research on looking at Chlamydia. Chlamydia is hard to study as it cannot be grown in liquid or plate culture, it can only be grown in cell lines. There are also no systems to manipulate its genetics. It has two stages of its life cycle – elementary bodies and reticulate bodies. These had led to a debate only recently resolved as to whether Chlamydia was a bacteria, virus or parasite.
Dr Hayward showed some beautiful pictures and movies using fluorescence microscopy, confocal microscopy and electron tomography, which have shown for the first time the interactions between Chlamydia and the host cell in great detail. It was even possible to just about see the needle injection apparatus of the bacteria actually penetrating the host cell. These new insights into the infection cycle show up possible places to target to counter this complex infection. Dr Hayward did an excellent job in explaining what we know and what we still need to find out.
