MicrobiologyBytes

In 1928, by chance, Alexander Fleming discovered penicillin, which was subsequently developed and saved millions from death by infectious disease. In this article in Microbiology Today, Kevin Brown recounts the story of this amazing antibiotic and tells something of the man who found it:

In many ways Fleming could have only discovered the original wonder drug in his musty, dusty, overcrowded, cluttered laboratory at St Mary’s Hospital. After all, if there was no possibility of contamination there could have been no penicillin. Some might argue that without Fleming, there would have been none either. Certainly, the chance contamination of culture plates was common, but Fleming’s genius was to notice something unusual and act upon it. As a scientist, he was very much in the tradition of the 19th-century lone researcher interested in unusual phenomena. This approach was to pay dividends when in September 1928 he returned from a 6-week holiday to find not only that a plate of staphylococci, he had been working on before his holiday had become contaminated by a fungus, but that there was the now classic zone of inhibition around the mould. Ever the master of understatement, Fleming’s response was typical of the man: “That’s funny!”

Read more

Related:

• Towards The Next 80 Years of Penicillin Production
• Penicillin: Triumph and Tragedy
• Antibiotics will not get rid of your cold

discovermagazine.com

It was just a matter of time before someone discovered that Madagascar is a museum for viruses. The discovery came when a team of American and English scientists perused the genome of the gray mouse lemur. Nestled among its genes were segments of DNA that bore a remarkable resemblance to HIV. How on Earth could a deadly virus’s genes become part of a primate’s own genome? Some kinds of viruses, known as retroviruses, replicate by inserting their DNA into host cells, where their DNA can guide the production of new viruses. But many studies indicate that sometimes these viruses infect the cells that will give rise to sperm and eggs. The virus ends up in a fertilized egg and gets passed down to ever cell in the developing embryo–including its own sex cells. Now the virus gets passed down through the generations. It may still retain the ability to infect other cells for a while, but mutations typically knock out that ability. Instead, the virus can only insert copies of its DNA back into its own host cell’s genome. Over millions of years, this viral DNA spreads through the host genome. Our own DNA contains 98,000 stretches of this virus DNA, plus 150,000 tiny viral fragments, making up about 8% of our genome – about five times more DNA than the DNA that encodes proteins.

Read more

Related:

• Phoenix from the ashes: The 5 million year old virus

Understanding the evolutionary history of human viruses, along with the factors that have shaped their spatial distributions, is one of the most active areas of study in the field of microbial evolution. This reviews give an overview of our current knowledge of the genetic diversity of human viruses using comparative studies of viral populations, particularly those with RNA genomes, to highlight important generalities in the patterns and processes of viral evolution. Special emphasis is given to the major dichotomy between RNA and DNA viruses in their epidemiological dynamics and the different types of phylogeographic pattern exhibited by human viruses. It also considers a central paradox in studies of virus evolution: Although epidemiological theory predicts that RNA viruses have ancestries dating back millennia, with major ecological transitions facilitating their emergence, the genetic diversity in currently circulating viral populations has a far more recent ancestry, indicative of continual lineage turnover.

Evolutionary history and phylogeography of human viruses. Annu Rev Microbiol. 2008 62: 307-328

Related:

• Do viruses evolve to protect their hosts?
• Global migration of influenza viruses

The discovery of the earliest known cases of human tuberculosis (TB) in bones found submerged off the coast of Israel shows that the disease is 3000 years older than previously thought. Direct examination of this ancient DNA confirms the latest theory that bovine TB evolved later than human TB. The new research sheds light on how the TB bacterium has evolved over the millennia and increases our understanding of how it may change in the future.

The bones, thought to be of a mother and baby, were excavated from Alit-Yam, a 9000 year-old Neolithic village, which has been submerged off the coast of Haifa, Israel for thousands of years. Scientists found characteristic bone lesions that are signs of TB in skeletons from the settlement, one of the earliest with evidence of domesticated cattle. An international team conducted detailed analyses of the bones using scientific techniques that revealed DNA and cell wall lipids from Mycobacterium tuberculosis, the principal agent of human TB. The DNA was sufficiently well-preserved for molecular typing to be carried out and the analysis of the bacterial cell wall lipids by high performance liquid chromatography provided direct, confirmatory evidence of tuberculosis.

This is the best evidence yet that in a community with domesticated animals but before dairying, the infecting strain was actually a human pathogen. The presence of large numbers of animal bones shows that animals were an important food source, and this probably led to an increase in the human population that helped the TB to be maintained and spread. The DNA of the strain of TB in these skeletons had lost a particular piece of DNA which is characteristic of a common family of strains present in the world today. The fact that this deletion had occurred 9000 years ago gives us a much better idea of the rate of change of the bacterium over time, and indicates an extremely long association with humans.

Examining ancient human remains for the markers of TB is very important because it helps to aid our understanding of prehistoric tuberculosis and how it evolved. This then helps us improve our understanding of modern TB and how we might develop more effective treatments.

Detection and Molecular Characterization of 9000-Year-Old Mycobacterium tuberculosis from a Neolithic Settlement in the Eastern Mediterranean. PLoS ONE 3(10): e3426
Mycobacterium tuberculosis is the principal etiologic agent of human tuberculosis. It has no environmental reservoir and is believed to have co-evolved with its host over millennia. This is supported by skeletal evidence of the disease in early humans, and inferred from M. tuberculosis genomic analysis. Direct examination of ancient human remains for M. tuberculosis biomarkers should aid our understanding of the nature of prehistoric tuberculosis and the host/pathogen relationship. We used conventional PCR to examine bone samples with typical tuberculosis lesions from a woman and infant, who were buried together in the now submerged site of Atlit-Yam in the Eastern Mediterranean, dating from 9250-8160 years ago. Rigorous precautions were taken to prevent contamination, and independent centers were used to confirmauthenticity of findings. DNA from five M tuberculosis genetic loci was detected and had characteristics consistent with extant genetic lineages. High performance liquid chromatography was used as an independent method of verification and it directly detected mycolic acid lipid biomarkers, specific for the M. tuberculosis complex. Human tuberculosis was confirmed by morphological and molecular methods in a population living in one of the first villages with evidence of agriculture and animal domestication. The widespread use of animals was not a source of infection but may have supported a denser human population that facilitated transmission of the tubercle bacillus. The similarity of the M. tuberculosis genetic signature with those of today gives support to the theory of a long-term co-existence of host and pathogen.

Related:

• Tuberculosis diagnostic tools
• Tuberculosis – is the white plague winning?

According to new research, the spread of the Roman Empire through Europe could help explain why those living in its former colonies are more vulnerable to HIV.

People once ruled by Rome are less likely to have a gene variant which protects against HIV. In countries inside the borders of the Roman Empire for longer periods, such as Spain, Italy and Greece, the frequency of the CCR5-delta32 gene, which offers some protection against HIV, is between 0% and 6%. Countries at the fringe of the empire, such as Germany and England, the rate is between 8% and 11.8%, while in countries never conquered by Rome the rate is greater than this.

On June 17 1867, the British surgeon Joseph Lister was the first person to perform surgery under antiseptic conditions. Lister came from a prosperous Quaker family in Essex and graduated with a degree in medicine from the University of London. In just a few years he became Professor of Surgery at the University of Glasgow. At that time the usual explanation for wound infections was that the exposed tissues were damaged by bad smells in the air which were called “miasma”. Hospital wards usually smelled bad, not due to “miasma” but due to the rotting of infected wounds.

Although anesthesia had been introduced in the preceding decades, post-surgical death rates ran at 40 to 50 percent because of hospital-acquired infections such as septicemia. Scientists were just beginning to make the connection between hygiene and infection. Hungarian physician Ignaz Semmelweis had discovered in 1847 that the simple act of obstetricians washing their hands in a chlorine solution could cut deaths from childbed fever from 10 percent to less than 2 percent. Lister had not heard of Semmelweis, but it is usually believed that his work to reduce mortality rates in British hospitals stemmed from his reading of Louis Pasteur’s research. In 1865, Pasteur reported that microorganisms cause matter to ferment and eventually rot. Lister made the connection between Pasteur’s research and his own profession.

Subscribe to podcasts (free):
[iTunes] Enhanced podcasts & videos
[RSS] mp3 podcasts (audio only)
Play this episode: Enhanced version
Audio only

Carbolic acid (phenol) had been used by the authorities in the town of Carlisle to treat smelly sewage, so Lister tested the results of spraying instruments, surgical incisions and dressings with a solution phenol. He also found that phenol solution swabbed on wounds markedly reduced the incidence of gangrene and subsequently published a series of articles on this finding. He also made surgeons wear clean gloves and wash their hands before and after operations with 5% phenol solution. Instruments were also washed in the same solution and assistants sprayed the solution into the air in the operating theatre. Another of his innovations was to stop using porous natural materials in manufacturing the handles of surgical instruments.

Lister reported that his surgical wards remained free of sepsis for nine months. Between 1864 and 1866, Lister lost 46 percent of his surgical patients. From 1867 to 1870, he lost “only” 15 percent. By 1877, he had dropped the death rate to 5 percent. As the germ theory of disease became more widely accepted, it was realised that infection could be better avoided by preventing bacteria from getting into wounds in the first place. This led to the development of sterile surgery. Lister went on to pioneer new surgical techniques, became Baron Lister of Lyme Regis and was made one of the twelve original members of the Order of Merit. The bacterial genus Listeria, including the food-borne pathogen Listeria monocytogenes, was named in his honour.

Related:

• Now wash your hands

In the years during and after World War II, the Microbiological Research Establishment (MRE) at Porton Down was the UK Government’s centre for germ warfare research (or defence, depending on who you believe). There were two parts to the MRE, the part “outside the wire”, which contained among other things, the Common Cold Unit, and the section “inside the wire”, which was top secret and has been the subject of much rumour and speculation.

I recently came across an article by Bill Parker, who worked at the MRE for two years and which lifts some of the curtain of secrecy. Makes interesting reading.