In some snake venoms, the toxins are too large to immediately enter the bloodstream and instead first travel through the lymphatic system before entering the heart. As nitric oxide inhibits the pumping action of the body’s lymph system, Megan Saul and colleagues reasoned that applying topical agents that release nitric oxide to the snakebite wound could impede the venom’s progress in the body. Thus, the researchers tested an ointment that contained nitric-oxide-releasing glyceryl trinitrate in their study published in Nature Medicine.

By simulating a snakebite in human volunteers (6 men and 9 women, who were told to remain still throughout the experiment, an important component of snake bite first aid) and injecting participants with a molecular dye, the researchers could track the progress of ‘snake venom’ through the lymph (from the initial ‘bite’ site in the foot to the lymph nodes in the groin). Applying a thick layer of the ointment within 1 minute of the injection markedly increased the foot-to-groin lymph transit time of the dye by nearly fourfold, from 13 min without treatment to 54 min with the ointment. Similarly, using the same principle in rats, the ointment also increased lymph transit time by threefold (from 3.2 min to 9.4 min). The researchers then went on to test whether the ointment could improve survival in rats injected with snake venom (from the Eastern Brown snake, one ofAustralia’s most deadly) and measured how time it took before the animals stopped breathing. Crucially, rats treated with the ointment lived about 50% longer (time to respiratory rest was 65 min in controls and 96 min in treated rats).

Pressure bandages and pads can be used to mechanically block the flow of snake venom in the body, but this approach can’t be used on bites to the face or torso and can be difficult to perform properly. Arguably, carrying a cream with you when out hiking in the wild is a simple new addition to your first aid kit and a bonus is that the ointment used in the study (Rectogesic, Care Pharmaceuticals) is already commercially available, albeit as a treatment for anal fistulas. Even though we don’t know exactly how much additional time this ointment will buy in bitten humans, that extra time could prove vital when seeking suitable antivenom treatment, especially in those in which pressure immobilisation is not possible.

Megan E Saul, Paul A Thomas, Peter J Dosen, Geoffrey K Isbister, Margaret A O’Leary, Ian M Whyte, Sally A McFadden &, & Dirk F van Helden (2011). A pharmacological approach to first aid treatment for snakebite Nature Medicine : doi:10.1038/nm.2382

Dorner, M., Horwitz, J., Robbins, J., Barry, W., Feng, Q., Mu, K., Jones, C., Schoggins, J., Catanese, M., Burton, D., Law, M., Rice, C., & Ploss, A. (2011). A genetically humanized mouse model for hepatitis C virus infection Nature, 474 (7350), 208-211 DOI: 10.1038/nature10168

Depressingly, in this modern era, diarrhoea—three or more loose bowel movements a day—is still a common cause of death in developing countries and is the 2^nd biggest killer of young children (under 5 years) worldwide. Poor hygiene, inadequate sanitation and lack of clean, safe drinking water all contribute to the spread of the harmful viruses, bacteria and parasites that cause diarrhoea. Now, Fischer Walker and colleagues use their Lives Saved Tool (LiST) to estimate the potential lives saved after implementing two different scale-up scenarios for key diarrhoeal prevention (breastfeeding, vitamin A supplements, basic water, sanitation, hygiene, and rotavirus vaccination) and treatment (oral rehydration salts, zinc supplementation, and antibiotics for dysentery) intervention strategies in 68 countries with high childhood mortality.

The researchers put forward two scenarios for the priority countries, which included Bangladesh, China and Haiti, for a 5-year period (between 2010 and 2015)—the “ambitious” (which assumed feasible improvement in all interventions) and the “universal” (which assumed near 100% coverage for all interventions). By 2015, diarrhoeal deaths could be reduced by 78% and 92% in the ambitious and universal scenarios, respectively. With the universal scenario, nearly 5 million deaths could be averted at an additional costs of US$0.80 per capita using some of the key diarrhoea prevention and treatment interventions (such as rotavirus vaccination and oral rehydration salts) and $3.24 per capita when all sanitation and water interventions (such as handwashing, improved sanitation and access to safe, clean water) implemented.

Fischer Walker and co-workers argue that “real progress” could be made in the treatment and management of diarrhoeal diseases if intervention strategies are made an international priority and the global health community works together to eliminate this harmful disease. Furthermore, the research acts as a pertinent reminder that we already have the technologies and interventions needed to prevent and reduce the devastating effects of diarrhoea, we just need to use them in the right scenario.

Walker, C., Friberg, I., Binkin, N., Young, M., Walker, N., Fontaine, O., Weissman, E., Gupta, A., & Black, R. (2011). Scaling Up Diarrhea Prevention and Treatment Interventions: A Lives Saved Tool Analysis PLoS Medicine, 8 (3) DOI: 10.1371/journal.pmed.1000428

Rasko and colleagues used highly accurate whole-genome sequencing and comparative genomics (against the B. anthracis Ames ancestor, believed to be the progenitor of all Ames lab samples and used as a gold standard reference strain in the USA) to determine the source strain of B. anthracis used in the letter attacks. First, the scientists took spore samples from some of the letters and grew them in the lab. A number of morphological variants were observed in these letter-isolated bacterial samples (yellow or yellow–grey coloured rather than the usual grey–white of wild-type anthrax colonies) and all had diminished abilities to sporulate. These variants were then sequenced and compared with genomes sequences of the gold standard Ames ancestor to identify four distinct loci with genetic mutations (three of which were in B. anthracis sporulation pathways, specifically regulation of a key protein, Spo0F) in the morpholigical variants—features unique to the isolated anthrax variants. None of these variants were found to be prevalent in the environment (even in the areas associated with the Amerithrax investigation).

Ultimately, using comparisons with genomes of repository anthrax sources, the anthrax spores used to lace the letters were found to have a unique genetic fingerprint; anthrax batches were eventually traced back to a source flask (RMR-1029) in the lab of Dr Bruce Ivins (a key suspect in the subsequent criminal investigation who later committed suicide before a criminal case could be brought to trial).

The study authors conclude that the B. anthracis bioterror attack investigations “taught us important lessons about the integration of whole-genome sequencing for forensic applications”, although they do concede that their methods might not applicable to other bioterror agents.

Rasko, D., Worsham, P., Abshire, T., Stanley, S., Bannan, J., Wilson, M., Langham, R., Decker, R., Jiang, L., Read, T., Phillippy, A., Salzberg, S., Pop, M., Van Ert, M., Kenefic, L., Keim, P., Fraser-Liggett, C., & Ravel, J. (2011). Bacillus anthracis comparative genome analysis in support of the Amerithrax investigation Proceedings of the National Academy of Sciences DOI: 10.1073/pnas.1016657108

Intestinal schistosomiasis (caused by the parasite Schistosoma mansoni) can be detected easily and accurately by measuring levels of an excreted parasite antigen called circulating cathodic antigen, or CCA, in an individual’s urine, according to new research published in PLoS Neglected Tropical Diseases. This method has been found to be at least as effective as the existing ‘gold standard’ diagnostic test the Kato-Katz assay—literally counting the number of parasite eggs per gram of poo—and also to blood tests that test for parasite-specific antibodies. Moreover, switching to these urine-based tests for schistomiasis diagnosis is, quite frankly, preferable to sifting through someone’s faeces (messy, risky, time consuming, and actually not that useful), and could also make it easier to assess the prevalence and resolution of S. mansoni infection, which could be beneficial for disease control programmes.

Taking advantage of a large study to assess schistosomiasis prevalence in young children, the researchers tested the sensitivity and specificity of two different types of CCA urine tests—a strip test designed for use in the laboratory (unfortunately no longer under production) and a cassette test suited for field use—and compared them to both the Kato-Katz technique for assessing S. mansoni egg burden and ELISAs to detect anti-schistosome antibodies. Stool, urine and blood samples were collected from 484 children (aged 1–15 years old) who lived in the village, Usoma, in Western Kenya, which is near Lake Victoria, an area known to have high S. mansoni infection rates. Even when taking into account the limitations of the Kato-Katz assay in their analysis, the urine-based diagnostics tests were still sensitive and specific with CCA test levels reflecting the stool egg burden, and thus the intensity of the infection (a finding that confirmed other study results). Moreover, the tests worked even if the children were also infected with other parasites (Ascaris lumbricoides, hookworm or Trichuris trichuria), which can affect the performance of some diagnostic tests.

The CCA diagnostic test for schistomiasis has now been shown to be effective in areas with a high burden of the disease, but more work is needed to see whether it is sensitive enough to detect disease in areas with low S. mansoni infection rates. Whether these urine tests will eventually replace the tried and tested Kato-Katz technique remains to be seen; one advantage of examining stool samples is that other parasites may be found and identified at the same time, which is not possible with the CCA test as it is specific for schistosomiasis.

Shane, H., Verani, J., Abudho, B., Montgomery, S., Blackstock, A., Mwinzi, P., Butler, S., Karanja, D., & Secor, W. (2011). Evaluation of Urine CCA Assays for Detection of Schistosoma mansoni Infection in Western Kenya PLoS Neglected Tropical Diseases, 5 (1) DOI: 10.1371/journal.pntd.0000951

Courtesy of CDC/ Dr. Balasubr Swaminathan; Peggy Hayes

The intracellular pathogen Listeria monocytogenes must escape the vacuole formed during entry into the host cell to replicate in its preferred environment—the cell cytosol—and continues its life cycle. Although the pore-forming bacterial toxin listeriolysin O is vital for Listeria escape and virulence, new research by Radtke and colleagues published online in PNAS shows that a host cell protein, CFTR (cystic fibrosis transmembrane conductance regulator, which forms a chloride ion channel that, incidentally, when dysfunctional results in cystic fibrosis), promotes escape of L. monocyotgenes from intracellular vacuoles.

Radtke et al. reasoned that, as the intravacuolar environment is dynamic and likely modulated by a variety of proteins, regulation of ion flux whilst Listeria is inside a vacuole could affect its subsequent escape from this membrane-bound organelle. The researchers confirmed that CFTR was endogenously expressed by mouse macrophages and addition of a CFTR inhibitor did not affect uptake of Listeria into host cells but did reduce the number of intracellular bacteria, indicating that the bacteria might be trapped within the vacuole. Using macrophages isolated from either wild-type mice or mice carrying the CFTR mutation associated with human cystic fibrosis, they found that defects in CFTR led to delayed intracellular replication (indicative of a defect in vacuole escape). Finally, the researchers conclude that CFTR potentially promotes escape of Listeria by controlling the flux of chlorides into the vacuole—a high chloride concentration seems to increase both the oligomerisation and haemolytic activity of listeriolysin O, the key bacterial toxin needed for escape.

Little is known about the role of ion transport in the context of bacterial infection and it would be interesting to see whether other ion channels and transporters also contribute to the virulence of Listeria and other intracellular bacteria.

 Radtke, A., Anderson, K., Davis, M., DiMagno, M., Swanson, J., & O’Riordan, M. (2011). Listeria monocytogenes exploits cystic fibrosis transmembrane conductance regulator (CFTR) to escape the phagosome Proceedings of the National Academy of Sciences DOI: 10.1073/pnas.1013262108

Salmonella species can cause a range of infections from typhoid fever to food poisoning. Ordinarily, the intracellular bacteria Salmonella enterica resides and replicates within a membrane-bound vacuole in epithelial cells. During its life cycle, the bacteria are adapted to survive within a wide range of environmental niches within the human host (including cells such as enterocytes and macrophages and organs such as the spleen and gastrointestinal tract).

Knodler et al. observed a subpopulation of Salmonella that were ‘hyper-replicating’; these bacteria were doubling in number at almost five times the rate of the overall population of bacteria in the epithelial cell. Not only that, these bacteria were rapidly proliferating not in the Salmonella-containing vacuole, but in the host cell cytosol (which is believed to be nutrient rich) and were ready to invade other cells (they expressed type III secretion system 1 components and flagella, virulence factors that are required for invasion). Moreover, epithelial cells overloaded with these hyper-replicating cytosolic Salmonella were forced out of the apical side of the epithelial-cell layer—just as when dying cells are extruded out of the epithelium during the normal rapid turnover of epithelial cells that occurs to maintain the gut epithelium. Subsequently, invasive bacteria are released into the lumen and are primed and ready to infect new cells. The extruded host cells then die in a caspase-1-dependent manner and trigger the production of the proinflammatory cytokine interleukin 18—a process which could, in part, explain the high levels of mucosal inflammation observed in Salmonella infections of the gut and gallbladder.


Knodler, L., Vallance, B., Celli, J., Winfree, S., Hansen, B., Montero, M., & Steele-Mortimer, O. (2010). Dissemination of invasive Salmonella via bacterial-induced extrusion of mucosal epithelia Proceedings of the National Academy of Sciences, 107 (41), 17733-17738 DOI: 10.1073/pnas.1006098107

Gibiansky et al. studied the behaviour of Pseudomonas aeruginosa, a bacteria that is ordinarily found in soil and water, but has increasingly been associated with opportunistic infections in humans (and is a particular problem in those with cystic fibrosis). A key feature of P. aeruginosa is that these bacteria form multicellular, surface-bound communities called biofilms and are able to move within these communities by twitching motility owing to their type IV pili (hair-like structures on bacteria that can extend, tether to a surface and then retract to move bacteria along). The researchers studied microscopy movies of the P. aeruginosa biofilms and used computer software to track how the bacteria transitioned from planktonic state (that is, freely suspended in liquid) to the surface-bound biofilm.

Two different surface motility mechanisms were observed just after P. aeruginosa bacteria attached to a surface, but before a microcolony of bacteria were formed. The scientists studied mutant bacteria lacking flagella (a tail-like bacterial appendage that can also enable bacteria to move) that can only move using their type IV pili. These bacteria tended to ‘crawl’ in one direction when positioned horizontal to the surface and ‘walked’ in all directions when attached vertically to the surface by one end of the bacteria. Each movement mechanism was useful for surface exploration; crawling enabled directional movement across larger areas (6 μm distance) than walking, which enabled rapid exploration in local areas (up to 2 μm distance). Furthermore, these same movements were observed in wild-type bacteria. Moreover, the orientation of bacteria influenced biofilm morphology. Surface detachment was facilitated by type IV pili by tilting bacteria from horizontal to vertical positions and after bacterial division newborn bacteria detach and then ‘walk’ away. Finally, bacteria lacking type IV pili could neither ‘crawl’ or ‘walk’.

Scientific observations like this brevia report add to the understanding of bacterial behaviour in biofilms and could eventually lead to useful, new treatments against biofilm-forming pathogens.

Gibiansky, M., Conrad, J., Jin, F., Gordon, V., Motto, D., Mathewson, M., Stopka, W., Zelasko, D., Shrout, J., & Wong, G. (2010). Bacteria Use Type IV Pili to Walk Upright and Detach from Surfaces Science, 330 (6001), 197-197 DOI: 10.1126/science.1194238

The increasing incidence of antibiotic resistance and the emergence of so-called ‘superbugs’ are of huge importance to medicine and society as a whole with the ever-increasing likelihood of a return to a world without antibiotics. This potentially disastrous public health crisis led the Infectious Diseases Society of America to launch the “10x’20” initiative in which they call for a global commitment to research and develop 10 new, effective antibiotic drugs by 2020. As a complement to this drug development, research into how bacteria develop this resistance could provide crucial clues for the rational design of new antimicrobial agents.

Henry Lee and colleagues investigated the population dynamics of antibiotic resistance. They grew a vat of E. coli with increasing amounts of the antibiotic norfloxacin and then took samples of the bacteria and monitored the percentage of bacteria that became resistant to the antibiotic. The scientists found an individual isolate that was highly resistant to norfloxacin (even higher than the greatest norfloxacin levels tested in their bioreactor). These bacteria produced indole, which is known to aid tolerance to stress in E. coli—indole induces anti-stress mechanisms such as drug efflux pumps that help drive out toxic substances from the bacterial cell—although its production can reduce the overall fitness of the bacteria. Moreover, indole boosts the antibiotic resistance of the whole bacterial population and not just the select few that produce it. This population-based resistance was not drug specific and was even observed when the scientists challenged E. coli with gentamicin, which is a different type of antibiotic (with a different mode of action) to the quinolone norfloxacin.

The researchers conclude that under antibiotic stress, a few drug-resistant mutants will endure a fitness cost to produce and share the benefits of the metabolite indole to “shield the less-resistant bacteria from antibiotic insult” and enable these ‘weak’ bacteria to survive.

Lee HH, Molla MN, Cantor CR, & Collins JJ (2010). Bacterial charity work leads to population-wide resistance. Nature, 467 (7311), 82-5 PMID: 20811456

The monkeypox virus can cause a serious zoonotic disease (potentially transmitted to humans from rodent species such as squirrels as well as primates such as monkeys) that is similar to smallpox. Smallpox vaccinations not only helped eradicate the smallpox virus, but also provided cross-protective immunity to monkeypox virus infection.

Anne Rimoin and colleagues assessed the burden of human monkeypox in the DRC by analyzing surveillance data for this disease from 2005–2007 in regions known to be endemic for the virus, a feat which had not been conducted since the early 1980s. In their up-to-date surveillance data across nine health zones in central DRC, 760 human monkeypox cases were confirmed by laboratory tests and the researchers found that the average annual cumulative incidence of monkeypox virus infection was 5.53 cases per 10,000 people across all zones. Men, children under the age of 15 years and people living in forested areas or who had not received a prior smallpox vaccination were at an increased risk of monkeypox infection whilst those who had been vaccinated against smallpox had a 5.2-fold lower risk of infection by the monkeypox virus than unvaccinated individuals. Rimoin et al. then compared the 1980s active surveillance data with their new 2000s findings from the same health zone and found that the incidence of human monkeypox in this zone increased substantially from 0.72 cases per 10,000 people in the 1980s to 14.42 cases per 10,000 people between 2005 and 2007.

The investigators add that “entire households are now mostly or completely [smallpox] vaccine naive”, which could result in increased human-human transmission between different generations within the same house. Furthermore, Rimoin and colleagues argue that because of several limitations (including poor access to remote areas) their study could have under-reported the true incidence of human monkeypox and the observed dramatic increase in disease incidence could in fact be a “conservative estimate”. Improved and continued disease surveillance will be needed to assess the true burden of monkeypox virus infection on public health in African populations, and could aid the development and implementation of strategies to reduce the risk of monkeypox virus infection.

Anne W. Rimoin, Prime M. Mulembakani, Sara C. Johnston, James O. Lloyd Smith, Neville K. Kisalu, Timothee L. Kinkela, Seth Blumberg, Henri A. Thomassen, Brian L. Pike, Joseph N. Fair, Nathan D. Wolfe, Robert L. Shongo, Barney S. Graham, Pierre Formenty, E, & Major (2010). Major increase in human monkeypox incidence
30 years after smallpox vaccination campaigns
cease in the Democratic Republic of Congo Proceedings of the National Academy of Sciences USA (Published ahead of print 30th August 2010) DOI: 10.1073/pnas.1005769107