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
[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.
Northern Nigeria is currently affected by a new outbreak of wild poliovirus type 1 (WPV1), which has begun to spread internationally. In 2008, a nine-fold increase in new cases caused by this serotype has been reported compared with the same period in 2007. This outbreak in northern Nigeria has the potential to cause major international outbreaks, as occurred in 2003-2006. This year, Nigeria accounts for 86% of WPV1 cases in the world.
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.
Commercial hunting and habitat loss are major drivers of the rapid decline of great apes. Ecotourism and research have been widely promoted as a means of providing alternative value for apes and their habitats. However, close contact between humans and habituated apes during ape tourism and research has raised concerns that disease transmission risks might outweigh benefits. To date only bacterial and parasitic infections of typically low virulence have been shown to move from humans to wild apes. This paper presents the first direct evidence of virus transmission from humans to wild apes. Tissue samples from habituated chimpanzees that died during three respiratory-disease outbreaks at our research site, Côte d’Ivoire, contained two common human paramyxoviruses. Virus strains sampled from chimpanzees were closely related to strains circulating in contemporaneous, worldwide human epidemics. Twenty-four years of mortality data from observed chimpanzees reveal that such respiratory outbreaks could have a long history. In contrast, survey data show that research presence has had a strong positive effect in suppressing poaching around the research site. These observations illustrate the challenge of maximizing the benefit of research and tourism to great apes while minimizing the negative side effects.
Since the realization that there is life on the Antarctic continent, research has revealed a multitude of suitably adapted microbes. In the May 2008 edition of Microbiology Today, Brent Christner and John Priscu peer into this icy habitat:
The realization that there was life on the Antarctic continent, other than that associated with the marine system, did not come to light until the seminal investigations initiated by the International Geophysical Year (IGY) in the late 1950s and early 1960s. These important pioneering studies reshaped our understanding of the potential for life in the coldest and driest desert on Earth. Research since these early IGY studies has revealed that large numbers of micro-organisms thrive in environments previously thought to be uninhabitable. Microbiological investigations conducted on deep ice cores and subglacial environments now support the notion that the Antarctic cryosphere may harbour some of the most unusual and extreme microbial ecosystems on our planet.
To control influenza outbreaks or a pandemic, it is important to identify and characterize the different vectors that could promote influenza virus transmission between people. The respiratory tract of influenza virus-infected individuals is the main reservoir for the chain of transmission in a community. Based on experiments with animal models and observational field studies, large respiratory droplets are considered to be the most frequent vectors sustaining influenza transmission. However, experimental studies with animals with no direct contact have demonstrated that aerosols also play a significant role. In humans, the hypothesis that there is an aerosol route of transmission is supported by indirect evidence in special circumstances, such as confinement for a prolonged period of time in an airplane in the presence of a patient infected with influenza virus. In addition, it has been documented that human influenza A viruses can survive for a prolonged period on different types of surfaces once they are present in the environment. Although controversial, the possibility that contaminated surfaces and fomites could act as vectors of transmission needs to be considered in the context of overall influenza pandemic preparedness.
For any environmental contamination to be relevant, the virus should not only remain infectious but also persist at a sufficient concentration to enable it to reach the respiratory tract via finger contamination. Rhinovirus is the most common respiratory virus known to be easily transmitted by this route. Whether influenza virus is also commonly transmitted by this route remains a subject of debate. However, given that the biological properties of a potential influenza virus pandemic strain have not been established, this route of transmission has to be considered. The severe acute respiratory syndrome coronavirus SARS highlighted the ability of respiratory viruses to act in unconventional ways since environmental contamination by stools played a significant role in some population clusters. All these questions should be considered not only from a scientific standpoint. We must also take into account and provide answers to the many possible questions raised by various communities and public health authorities.
The authors of a recent paper hypothesized that banknotes may be one of various possible influenza vectors and may offer opportunities for infection. In Switzerland, a small country with a population of approximately 7 million, it is estimated that 20 to 100 million banknotes are exchanged each day, and billions of individual notes are exchanged daily worldwide. So could influenza be transmitted by money?
Survival of influenza virus on banknotes. Appl Environ Microbiol 2008 74: 3002-7
Successful control of a viral disease requires knowledge of the different vectors that could promote its transmission among hosts. We assessed the survival of human influenza viruses on banknotes given that billions of these notes are exchanged daily worldwide. Banknotes were experimentally contaminated with representative influenza virus subtypes at various concentrations, and survival was tested after different time periods. Influenza A viruses tested by cell culture survived up to 3 days when they were inoculated at high concentrations. The same inoculum in the presence of respiratory mucus showed a striking increase in survival time (up to 17 days). Similarly, B/Hong Kong/335/2001 virus was still infectious after 1 day when it was mixed with respiratory mucus. When nasopharyngeal secretions of naturally infected children were used, influenza virus survived for at least 48 h in one-third of the cases. The unexpected stability of influenza virus in this nonbiological environment suggests that unusual environmental contamination should be considered in the setting of pandemic preparedness.
The Baas-Becking hypothesis, also known as the “everything is everywhere” (EisE) hypothesis, encapsulates the classical view that microscopic organisms are globally distributed due to their high dispersal potential. Small size and an ability to enter dormancy might explain why prokaryotes and some microscopic eukaryotes, such as protists and small invertebrates, have acquired global distributions. The assumption that organisms smaller than 2 mm have a cosmopolitan distribution is often true when species are defined using traditional taxonomy. However, the EisE hypothesis has been challenged recently as molecular evidence revealed a high degree of cryptic diversity and restricted dispersal in a variety of microscopic organisms, including prokaryotes, protists and fungi. Other studies have found cases of restricted distributions by re-evaluating morphological evidence in species previously assumed to have cosmopolitan distributions.
Subscribe to podcasts (free):
[iTunes] Enhanced podcasts
[RSS] mp3 podcasts (audio only) Play this episode:Enhanced version
Audio only:
The current debate on the EisE hypothesis divides scientists in two major groups. On one side, scientists holding to the hypothesis in its original form assume that species differences in samples from different areas occur because of environmental differences, and not because of restricted dispersal. Thus, “everything is everywhere, but the environment selects” is considered the rule for microorganisms. On the other hand, other scientists propose that classical morphological taxonomy of microscopic organisms is not able to resolve their true diversity, and therefore that cosmopolitan ranges result from misidentification and lumping of spatially isolated lineages. So cosmopolitanism is considered as an exception in microorganisms, as it is in macroorganisms.
A recent paper tested the EisE hypothesis in an interesting test-case, the bdelloid rotifers (Molecular evidence for broad-scale distributions in bdelloid rotifers: everything is not everywhere but most things are very widespread. Molecular Ecology, 03 Jun 2008). Bdelloids are microscopic animals (the vast majority smaller than 1 mm) that have been regarded traditionally to have cosmopolitan species. The authors sampled living bdelloid rotifers from water in rivers, ponds and water bodies, and dormant animals in dry mosses and lichens. The sampling effort was greatest in Italy and the UK, with lesser sampling across seven other countries in Europe, including with 25 samples from Africa, Antarctica, Australia, New Zealand, North America and Southeast Asia. They used cytochrome oxidase I (COX1) sequence data to determine relationships. Many traditional bdelloid species were found commonly in almost every place sampled, supporting the idea of cosmopolitan distribution. Hence, the molecular data tended to support the traditional EisE hypothesis based on morphological species identification.
So what?
Rotifers are interesting organisms which have attracted some attention lately. As far as anyone can tell, the bdelloid rotifers are ancient asexuals - they appear to have been living entirely without sex for more than 85 million years (Who Needs Sex (or Males) Anyway? PLoS Biol 5(4): e99). Instead of reproducing via eggs and sperm, asexual organisms can reproduce in any number of ways. For instance, some bud off a piece of themselves; the piece grows into a whole new animal. The bdelloids, like many other asexuals, reproduce by means of eggs that don’t need to be fertilized. Evolving asexuality isn’t the hard part. The hard part is making an evolutionary success of this lifestyle. So rotifers steal genes. Bdelloid rotifers contain many genes that appear to have originated in bacteria, fungi, and plants. These fascinating organisms not only have relaxed the normal barriers to incorporating foreign genetic material, but more surprisingly, they even managed to keep some of these alien genes functional (Massive Horizontal Gene Transfer in Bdelloid Rotifers. Science 2008 320: 1210).
Nevertheless, although “everything is not everywhere”, bdelloid rotifers do display broad geographical distributions typical of those of other microscopic organisms. Broad dispersal and large population sizes might be factors lessening the evolutionary cost of long-term abstinence from sexual reproduction in this group of obligate parthenogens.
Coronaviruses are the causative agents of many respiratory and enteric infections in humans and animals, including SARS. As with all viruses, virtually all of the steps of their infection cycle depend on host cellular factors. As the first and most crucial step after their entry into cells, coronaviruses assemble their replication complexes in association with characteristic, newly induced membranous structures. The cellular pathways hijacked by these plus-strand RNA viruses to create these “factories” have not been elucidated.
A new study shows the involvement of the secretory pathway in mouse hepatitis coronavirus (MHV) replication by using the drug brefeldin A (BFA), which interferes with ER–Golgi membrane traffic by inhibiting the activation of ADP-ribosylation factor (ARF) small GTPases. MHV RNA replication is sensitive to BFA treatment and the BFA-sensitive guanidine nucleotide exchange factor GBF1 and its downstream effector ARF1 are of critical importance for coronavirus replication. The authors speculate that while GBF1 and ARF1 are not involved in the formation of the viral replication structures, they probably play a key role in their maturation or functioning. As this work was limited to the mouse hepatitis coronavirus, an interesting next step would be to study the importance of GBF1 and ARF1 in the replication of other coronaviruses.
Mouse Hepatitis Coronavirus RNA Replication Depends on GBF1-Mediated ARF1 Activation. PLoS Pathog 4(6): e1000088
Coronaviruses induce in infected cells the formation of double membrane vesicles, which are the sites of RNA replication. Not much is known about the formation of these vesicles, although recent observations indicate an important role for the endoplasmic reticulum in the formation of the mouse hepatitis coronavirus (MHV) replication complexes (RCs). We now show that MHV replication is sensitive to brefeldin A (BFA). Consistently, expression of a dominant-negative mutant of ARF1, known to mimic the action of the drug, inhibited MHV infection profoundly. Immunofluorescence analysis and quantitative electron microscopy demonstrated that BFA did not block the formation of RCs per se, but rather reduced their number. MHV RNA replication was not sensitive to BFA in MDCK cells, which are known to express the BFA-resistant guanine nucleotide exchange factor GBF1. Accordingly, individual knockdown of the Golgi-resident targets of BFA by transfection of small interfering RNAs (siRNAs) showed that GBF1, but not BIG1 or BIG2, was critically involved in MHV RNA replication. ARF1, the cellular effector of GBF1, also appeared to be involved in MHV replication, as siRNAs targeting this small GTPase inhibited MHV infection significantly. Collectively, our results demonstrate that GBF1-mediated ARF1 activation is required for efficient MHV RNA replication and reveal that the early secretory pathway and MHV replication complex formation are closely connected.
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.
