MicrobiologyBytes

There’s a great collection of freely available resources On the Nature website under Nature Collections – Malaria (maybe NPG is finally getting the message about open access – hey Nature, it’s good to share :-)

The world is on the verge of making major inroads against malaria – a deadly disease that still claims the lives of more than 1 million people annually, mostly children less than 5 years of age. Over the past decade, scientists, large pharmaceutical companies and small biotechnology firms, governments and philanthropic organizations have come together to mount a full frontal attack on malaria, and there is now even talk of the ‘E word’ – that is, eradication. This collection highlights advances in the deployment of existing tools, and in the basic science of malaria – particularly those flowing from sequencing of the malaria parasite genomes – that will underpin the next generation of malaria-control tools, which will be needed if the scourge of malaria is to be eradicated.

Contents:

• Malaria: The end of the beginning – After decades of work, a pioneering malaria vaccine may soon reach the final phase of clinical trials. A vaccine that is far from perfect – but which may provide new direction and save thousands of lives.
• Malaria vaccine gets shot in the arm from tests – Promising results pave the way for a vaccine candidate to undergo full-blown trials across Africa.
• Malaria: The big push – Zambia, with help from partners around the world, is stepping up its battle against malaria.
• The billion-dollar malaria moment – For years the global malaria effort has been asking for more resources. Now the field needs to figure out a systematic strategy for spending the money effectively.
• Review: Malaria research in the post-genomic era

Articles:

• Comparative genomics of the neglected human malaria parasite Plasmodium vivax
• Genome sequence of the human malaria parasite Plasmodium falciparum
• Genome sequence and comparative analysis of the model rodent malaria parasite Plasmodium yoelii yoelii
• The genome of the simian and human malaria parasite Plasmodium knowlesi

Related:

• MicrobiologyBytes: Malaria

Malaria is one of the most common infectious diseases in the world and one of the greatest global public health problems. The Plasmodium falciparum parasite causes approximately 500 million cases each year and over one million deaths in sub-Saharan Africa. More than 40% of the world’s population is at risk of malaria. The parasite is transmitted to people through the bites of infected mosquitoes. These insects inject a life stage of the parasite called sporozoites, which invade human liver cells where they reproduce briefly. The liver cells then release merozoites (another life stage of the parasite), which invade red blood cells. Here, they multiply again before bursting out and infecting more red blood cells, causing fever and damaging vital organs. The infected red blood cells also release gametocytes, which infect mosquitoes when they take a blood meal. In the mosquito, the gametocytes multiply and develop into sporozoites, thus completing the parasite’s life cycle. Malaria can be prevented by controlling the mosquitoes that spread the parasite and by avoiding mosquito bites by sleeping under insecticide-treated bed nets. Effective treatment with antimalarial drugs also helps to decrease malaria transmission.

In 1998, the World Health Organization and several other international agencies launched Roll Back Malaria, a global partnership that aims to reduce the human and socioeconomic costs of malaria. Targets have been continually raised since this time and have culminated in the Roll Back Malaria Global Malaria Action Plan of 2008, where universal coverage of locally appropriate interventions is called for by 2010 and the long-term goal of malaria eradication again tabled for the international community. For malaria control and elimination initiatives to be effective, financial resources must be concentrated in regions where they will have the most impact, so it is essential to have up-to-date and accurate maps to guide effort and expenditure. In 2008, researchers of the Malaria Atlas Project constructed a map that stratified the world into three levels of malaria risk: no risk, unstable transmission risk (occasional focal outbreaks), and stable transmission risk (endemic areas where the disease is always present). Now, researchers extend this work by describing a new evidence-based method for generating continuous maps of P. falciparum endemicity within the area of stable malaria risk over the entire world’s surface. They then use this method to produce a P. falciparum endemicity map for 2007. Endemicity is important as it is a guide to the level of morbidity and mortality a population will suffer, as well as the intensity of the interventions that that will be required to bring the disease under control or additionally to interrupt transmission.

The researchers identified nearly 8,000 surveys of P. falciparum parasite rates (Pf PR; the percentage of a population with parasites detectable in their blood) completed since 1985 that met predefined criteria for inclusion into a global database of PfPR data. They then used ‘‘model-based geostatistics’’ to build a world map of P. falciparum endemicity for 2007 that took into account where and, importantly, when and all these surveys were done. Predictions were comprehensive (for every area of stable transmission globally) and continuous (predicted as a endemicity value between 0% and 100%). The population at risk of three levels of malaria endemicity were identified to help summarize these findings: low endemicity, where PfPR is below 5% and where it should be technically feasible to eliminate malaria; intermediate endemicity where PfPR is between 5% and 40% and it should be theoretically possible to interrupt transmission with the universal coverage of bed nets; high endemicity is where PfPR is above 40% and suites of locally appropriate intervention will be needed to bring malaria under control. The global level of malaria endemicity is much reduced when compared with historical maps. Nevertheless, the resulting map indicates that in 2007 almost 60% of the 2.4 billion people at malaria risk were living in areas with a stable risk of P. falciparum transmission – 0.69 billion people in Central and South East Asia (CSE Asia), 0.66 billion in Africa, Yemen, and Saudi Arabia (Africaþ), and 0.04 billion in the Americas. The people of the Americas were all in the low endemicity class. Although most people exposed to stable risk in CSE Asia were also in the low endemicity class (88%), 11% were in the intermediate class, and 1% were in the high endemicity class. By contrast, high endemicity was most common and widespread in the Africaþ region (53%), but with significant numbers in the intermediate (30%), and low (17%) endemicity classes.

The accuracy of this new world map of P. falciparum endemicity depends on the assumptions made in its construction and critically on the accuracy of the data fed into it, but because of the statistical methods used to construct this map, it is possible to quantify the uncertainty in the results for all users. Thus, this map (which, together with the data used in its construction, will be freely available) represents an important new resource that clearly indicates areas where malaria control can be improved (for example, Africa) and other areas where malaria elimination may be technically possible. In addition, planned annual updates of the global P. falciparum endemicity map and the PfPR database by the Malaria Atlas Project will help public health experts to monitor the progress of the malaria control community towards international control and elimination targets.

A world malaria map: Plasmodium falciparum endemicity in 2007. 2009 PLoS Med 6(3): e1000048
Efficient allocation of resources to intervene against malaria requires a detailed understanding of the contemporary spatial distribution of malaria risk. It is exactly 40 y since the last global map of malaria endemicity was published. This paper describes the generation of a new world map of Plasmodium falciparum malaria endemicity for the year 2007. A total of 8,938 P. falciparum parasite rate (PfPR) surveys were identified using a variety of exhaustive search strategies. Of these, 7,953 passed strict data fidelity tests for inclusion into a global database of PfPR data, age-standardized to 2–10 y for endemicity mapping. A model based geostatistical procedure was used to create a continuous surface of malaria endemicity within previously defined stable spatial limits of P. falciparum transmission. These procedures were implemented within a Bayesian statistical framework so that the uncertainty of these predictions could be evaluated robustly. The uncertainty was expressed as the probability of predicting correctly one of three endemicity classes; previously stratified to be an informative guide for malaria control. Population at risk estimates, adjusted for the transmission modifying effects of urbanization in Africa, were then derived with reference to human population surfaces in 2007. Of the 1.38 billion people at risk of stable P. falciparum malaria, 0.69 billion were found in Central and South East Asia (CSE Asia), 0.66 billion in Africa, Yemen, and Saudi Arabia (Africaþ), and 0.04 billion in the Americas. All those exposed to stable risk in the Americas were in the lowest endemicity class. The vast majority (88%) of those living under stable risk in CSE Asia were also in this low endemicity class; a small remainder(11%) were in the intermediate endemicity class; and the remaining fraction (1%) in high endemicity areas. High endemicity was widespread in the Africaþ region, where 0.35 billion people are at this level of risk. Most of the rest live at intermediate risk (0.20 billion), with a smaller number (0.11 billion) at low stable risk. High levels of P. falciparum malaria endemicity are common in Africa. Uniformly low endemic levels are found in the Americas. Low endemicity is also widespread in CSE Asia, but pockets of intermediate and very rarely high transmission remain. There are therefore significant opportunities for malaria control in Africa and for malaria elimination elsewhere. This 2007 global P. falciparum malaria endemicity map is the first of a series with which it will be possible to monitor and evaluate the progress of this intervention process.

Related:

• MicrobiologyBytes: Malaria
• Malaria, mosquitoes and the legacy of Ronald Ross
• New ways to beat malaria
• Researchers characterize potential protein targets for malaria vaccine
• Researchers Find Essential Proteins for Critical Stage of Malaria Transmission

Burkitt’s lymphoma (BL) was first described 50 years ago, and the first human tumour virus Epstein–Barr virus (EBV) was discovered in BL tumours soon after. Since then, the role of EBV in the development of BL has become more and more enigmatic. Only recently have we finally begun to understand, at the cellular and molecular levels, the complex and interesting interaction of EBV with B cells that creates a predisposition for the development of BL. This review discusses the intertwined histories of EBV and BL and their relationship to the cofactors in BL pathogenesis: malaria and the MYC translocation.

The curious case of the tumour virus: 50 years of Burkitt’s lymphoma. 2008 Nature Reviews Microbiology 6, 913-924

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• Herpesviruses – not all bad?

Transmission of Plasmodium, the causative agent of malaria, requires the completion of a complex life cycle in the mosquito, which includes invasion of the salivary glands. This invasion depends on the recognition of mosquito salivary gland surface components by the parasite. Malaria is estimated to infect 300 to 500 million people worldwide resulting in over 1 million deaths each year.

Researchers have now identified the molecular components that enable the malaria-causing parasite Plasmodium to infect the salivary glands of the Anopheles mosquito – a critical stage for spreading malaria to humans. Saglin, a mosquito salivary protein, is a receptor for the Plasmodium protein Thrombospondin-Related Anonymous Protein (TRAP). The two proteins bind together to allow invasion of the salivary gland by Plasmodium sporozoites, which can be transmitted to a human when bitten by an infected mosquito. Through a series of experiments, the scientists found that saglin bound with the artificial peptide SM1. The team then developed an antibody to find a protein similar to SM1 that existed naturally in the parasite, which they identified as TRAP. To further prove the interaction between saglin and TRAP, the team conducted experiments to down-regulate, or switch off, saglin expression, which greatly diminished salivary gland invasion in the mosquito. This work is the culmination of a decade-long research project in which peptide libraries were used to understand the mechanisms that the parasite uses to develop in its obligatory mosquito host, and demonstrates that interaction between the salivary-gland-specific surface protein saglin and the parasite surface protein TRAP is essential for invasion to occur. A better understanding of the mechanisms used by the parasite to develop in the mosquito may lead to novel approaches to intervene with the spread of the disease.

Malaria Parasite Invasion of the Mosquito Salivary Gland Requires Interaction between the Plasmodium TRAP and the Anopheles Saglin Proteins. 2009 PLoS Pathog 5(1): e1000265
SM1 is a twelve-amino-acid peptide that binds tightly to the Anopheles salivary gland and inhibits its invasion by Plasmodium sporozoites. By use of UV-crosslinking experiments between the peptide and its salivary gland target protein, we have identified the Anopheles salivary protein, saglin, as the receptor for SM1. Furthermore, by use of an anti-SM1 antibody, we have determined that the peptide is a mimotope of the Plasmodium sporozoite Thrombospondin Related Anonymous Protein (TRAP). TRAP binds to saglin with high specificity. Point mutations in TRAP’s binding domain A abrogate binding, and binding is competed for by the SM1 peptide. Importantly, in vivo down-regulation of saglin expression results in strong inhibition of salivary gland invasion. Together, the results suggest that saglin/TRAP interaction is crucial for salivary gland invasion by Plasmodium sporozoites.

Related:

• MicrobiologyBytes: Malaria
• Malaria, mosquitoes and the legacy of Ronald Ross
• New ways to beat malaria
• Researchers characterize potential protein targets for malaria vaccine
• Gametogenesis in malaria parasites

One of the main problems in fighting malaria is the speed with which Plasmodium falciparum, the causative agent of human malaria, is able to vary its genetic makeup. This allows antigenic variation, which makes the creation of effective vaccines very difficult. Antigenic variability also gives P. falciparum the ability to persist in the face of an immune reaction and to reinfect people who have been previously exposed to the disease. Effective immunity to malaria requires repeated infections and is slow to develop, so children under ten years of age are most susceptible to illness. The entry of malaria parasites into red blood cells during the replication cycle creates two opportunities to evade host immunity. First, infected red blood cells do not induce a CTL response due to their lack of MHC I expression. Second, malaria antigens exposed on the surface of the cell are highly variable. The P. falciparum erythrocyte membrane protein 1 (PfEMP1) is a key virulence factor which is expressed on the surface of infected erythrocytes and causes the blood cells to stick to the walls of small blood vessels, preventing infected cells from going through the general circulation and to the spleen (see: Giving malaria the slip).

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Red blood cells infected with Plasmodium display immunodominant parasite antigens on their surface. The reason for this is not clear, but it may be to modify the physical properties of the host cells so that they are not trapped and destroyed in the spleen. The expression of the immunodominant surface protein PfEMP1 is also linked to suppression of host interferon-gamma in the early immune response to the parasite, and low interferon-gamma levels may improve parasite survival.

PfEMP1 is in fact a family of cell surface molecules, encoded by approximately 60 var genes. Antigenic variation is controlled by epigenetic factors including monoallelic var transcription in separate domains at the nuclear periphery, differential histones on otherwise identical var genes, and var gene silencing mediated by telomeres (Antigenic variation in Plasmodium falciparum. Annu Rev Microbiol. 2008 62: 445-470).

Targeting the mechanisms responsible for antigen switching could be a promising approach to tackle the malaria parasite without having to deal with phenotypic variation of the surface molecule. The development of specific biological assays that target antigenic variation could uncover crucial mechanisms required for export to the cell surface, repression of the var gene family, or switching to new variants and would allow the screening of drugs which block these essential processes. Plasmodium’s trump card could yet prove to be its undoing.

Related:

• Malaria, mosquitoes and the legacy of Ronald Ross
• Malaria: now you see me, now you don’t
• Researchers characterize potential protein targets for malaria vaccine
• Blood group O protects against severe malaria
• Tough Choices – DDT or Malaria?

Every day 2000 children die from malaria in Africa alone. The infection is transmitted from human to human by biting mosquitoes. Despite many years of effort, a vaccine is still not available to fight the deadly disease. Once injected by a mosquito, parasites migrate to the liver where they mature and then their sporozoites (infective cells) are released into the blood, causing disease and fatal complications. Human malaria is caused by Plasmodium falciparum, a unicellular protozoan parasite that is transmitted by Anopheles mosquitoes. An infectious mosquito injects saliva containing sporozoite forms of the parasite and these then migrate from the skin to the liver, where they establish an infection. Many intervention strategies are currently focused on preventing the establishment of infection by sporozoites. Clearly, an understanding of the biology of the sporozoite is essential for developing new intervention strategies. Sporozoites are produced within the oocyst, located on the outside wall of the mosquito midgut, and migrate after release from the oocysts to the salivary glands where they are stored as mature infectious forms. Comparison of the proteomes of sporozoites derived from either the oocyst or from the salivary gland reveals remarkable differences in the protein content of these stages despite their similar morphology. The changes in protein content reflect the very specific preparations the sporozoites make in order to establish an infection of the liver. Analysis of the function of several previously uncharacterized, conserved proteins revealed proteins essential for sporozoite development at distinct points of their maturation.

Researchers characterized a large number of parasite proteins that may prove useful in the development of a human malaria vaccine. A promising method for vaccination is to sufficiently weaken these parasites such that they invade liver cells and stimulate an immune response, but don’t develop further. This can be achieved by genetically inactivating individual parasite genes that are active during the parasite’s growth in the liver. The researchers achieved this by modifying the proteins essential for sporozoite development, which their study identified. Collaborators had previously shown how to successfully vaccinate mice using a rodent malaria which had one of these liver stage genes removed, specifically p36p.

A related article shows the first transition of such a vaccination from the rodent system to humans, by inactivating the equivalent gene (p52) in the major human malaria parasite, P. falciparum. Similar to the results with the rodent parasite, these human parasites are unable to develop in liver cells. This is the first time that genetic modification of a human parasite results in its growth arrest in a liver cell, opening up promising possibilities for its use as a human vaccine. These studies show how results obtained in rodent models of malaria can be pipelined to form the basis for clinical development of anti-malaria vaccines in humans.

Proteomic Profiling of Plasmodium Sporozoite Maturation Identifies New Proteins Essential for Parasite Development and Infectivity. PLoS Pathog 4(10): e1000195
Plasmodium falciparum sporozoites that develop and mature inside an Anopheles mosquito initiate a malaria infection in humans. Here we report the first proteomic comparison of different parasite stages from the mosquito – early and late oocysts containing midgut sporozoites, and the mature, infectious salivary gland sporozoites. Despite the morphological similarity between midgut and salivary gland sporozoites, their proteomes are markedly different, in agreement with their increase in hepatocyte infectivity. The different sporozoite proteomes contain a large number of stage specific proteins whose annotation suggest an involvement in sporozoite maturation, motility, infection of the human host and associated metabolic adjustments. Analyses of proteins identified in the P. falciparum sporozoite proteomes by orthologous gene disruption in the rodent malaria parasite, P. berghei, revealed three previously uncharacterized Plasmodium proteins that appear to be essential for sporozoite development at distinct points of maturation in the mosquito. This study sheds light on the development and maturation of the malaria parasite in an Anopheles mosquito and also identifies proteins that may be essential for sporozoite infectivity to humans.

Related:

• Gametogenesis in malaria parasites
• Malaria, mosquitoes and the legacy of Ronald Ross
• New target for anti-malaria drugs
• Blood group O protects against severe malaria

According to a new analysis, neglected tropical diseases (NTDs) as a group may have surpassed HIV/AIDS, tuberculosis and malaria as the most prevalent infectious diseases in Latin America and the Caribbean. The work found that NTDs are the most common infections of approximately 200 million of the poorest people in the region. They include tens of millions of cases of intestinal worm infections, and almost 10 million cases of Chagas disease, as well as schistosomiasis, trachoma, dengue fever, leishmaniasis, lymphatic filariasis (LF), and onchocerciasis. NTDs produce extreme poverty by adversely impacting child development, pregnancy outcomes and worker productivity. In some cases in Latin America and the Caribbean, NTDs also represent a living legacy of slavery, because they were first introduced into the region through the global slave trade, and even today they predominantly affect people of African descent and indigenous groups, as well as other vulnerable groups such as women and children.

In the coming years, schistosomiasis transmission could be eliminated in the Caribbean, and that transmission of lymphatic filariasis and onchocerciasis could be eliminated in Latin America and the Caribbean with proven successful, cost effective and low-cost treatments. The most burdensome NTDs, such as Chagas disease, intestinal worm infections, and schistosomiasis may first require scale-up of existing resources and/or the development of new tools in order to achieve wider control and/or elimination. Ultimately, successful wide-scale efforts for NTD elimination will require an inter-sectoral approach that bridges public health with social services and environmental interventions.

Neglected diseases impose a huge burden on developing countries, constituting a serious obstacle for socioeconomic development and quality of life. They mostly affect people living either in shantytowns, indigenous communities or poor rural and agricultural areas. Last week, UK government officials announced that they will be contributing £50 million over the next five years toward the control and elimination of NTDs, including Guinea worm. In addition, the World Health Organziation announced that in 2007 alone, 546 million of the world’s poorest people received treatment for lymphatic filariasis at a cost of 10 cents per person, enabling them to live healthier more productive lives. After rainfall-induced disasters like Hurricane Ike, respiratory and intestinal infections usually increase and there is increased risk of breeding of the mosquito that transmits lymphatic filarisis in Haiti. While around three million people will be treated in Haiti in 2008 for lymphatic filariasis, additional resources are needed to step up and maintain treatment coverage in Haiti with its population of 9.5 million people, particularly in the wake of the Hurricane.

The Neglected Tropical Diseases of Latin America and the Caribbean: A Review of Disease Burden and Distribution and a Roadmap for Control and Elimination. 2008 PLoS Negl Trop Dis 2(9): e300

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Researchers at Johns Hopkins University have characterized a virus that is infectious to Anopheles gambiae – the mosquito primarily responsible for transmitting malaria. According to the researchers, this virus could potentially be used to pass on new genetic information to A. gambiae mosquitoes to help control malaria, which kills over one million people worldwide each year.

Paratransgenesis, the genetic manipulation of mosquito symbiotic microorganisms, is being considered as a potential strategy to control malaria. Microorganisms associated with Anopheles mosquitoes could be manipulated to alter the mosquito’s ability to become infected with and transmit the malaria parasites, or reduce mosquito fecundity or lifespan. The researchers identified the first potential microorganism (A. gambiae densovirus; AgDNV) for paratransgenesis of the major malaria vector Anopheles gambiae. AgDNV is highly infectious to A. gambiae larvae, disseminates to adult tissues and is transmitted vertically to subsequent generations. Recombinant AgDNV was able to transduce expression of an exogenous gene (EGFP) in A. gambiae cells and mosquitoes. EGFP-transducing virions infected mosquitoes, expressed EGFP in epidemiologically relevant tissues and were transmitted to offspring in a similar manner to wild-type virus. AgDNV could be used as part of a paratransgenic malaria control strategy by transduction of anti-Plasmodium genes or insect-specific toxins in Anopheles mosquitoes, as well as an easy-to-use system for transient gene expression and RNAi for basic laboratory research.

AgDNV is a member of the Parvovirus family, a “densovirus”, which are quite common in mosquitoes and other insects, but do not infect vertebrates such as humans. Although AgDNV does not appear to harm the mosquitoes, the researchers determined it is highly infectious to mosquito larvae and is easily passed on to the adults. The discovery came about serendipitously while the research team was conducting experiments to determine whether Wolbachia bacteria could be used to infect A. gambiae mosquito cells. During the analysis, they noticed an “artifact” that appeared as an unexpected prominent band in the gel used to detect the bacteria. The virus could be altered to kill the mosquito or make A. gambiae incapable of transmitting malaria. To test the concept, the research team successfully used altered AgDNV to express harmless green fluorescent protein in the adult mosquitoes which could be easily spotted under the microscope. In theory, we could use this virus to produce a lethal toxin in the mosquito or instruct the mosquito to die after 10 days, which is before it can transmit the malaria parasite to humans. However, these concepts are still many years away from practical use.

Viral Paratransgenesis in the Malaria Vector Anopheles gambiae. PLoS Pathog 2008 4(8): e1000135

Related:

• Malaria, mosquitoes and the legacy of Ronald Ross
• New target for anti-malaria drugs
• Blood group O protects against severe malaria
• Tough Choices – DDT or Malaria?
• DNA Viruses

Resistance to ciprofloxacin, a member of one of the most commonly used groups of antibiotics in the world, has been discovered by a team of Canadian researchers among people in remote South American villages who are believed to have never taken this medication. The researchers found high levels of ciprofloxacin resistance in Escherichia coli in Amerindians from the Guyanese rainforest. These individuals are reported as never having received treatment with ciprofloxacin or related fluoroquinolone antibiotics. The Amerindians had however received frequent treatment for malaria (which is a eukaryotic parasite and not a bacterium) with chloroquine. Chloroquine is used widely around the world to combat malaria, and it also is a close chemical cousin of the fluoroquinolones. Fluoroquinolones began widespread use in the late 1980s and now are among the most commonly used antibiotics in North America and Europe. Because the bacteria carried by the Guyanese Amerindians were resistant to ciprofloxacin, the researchers suggest that it is possible that exposure to chloroquine may make the bacteria that people carry in their intestines resistant to fluoroquinolones – a theory that, if corroborated by further research, could have important public health implications in developing countries and in the developed world. They also found resistance in many other species of bacteria – including Salmonella – that are found in rectal swabs. This means that chloroquine use for malaria may make the fluoroquinolones less effective for many common tropical diseases such as typhoid fever, diarrheal illnesses, and possibly also tuberculosis and pneumonia in the developing world.

Plans are being considered by major global health-promotion organizations to launch a campaign of widespread use in Africa and South America of a new anti-malarial treatment regimen called Artemesinin combination therapy (ACT). ACT usually includes quinoline drugs similar to chloroquine. These drugs are closely related to both chloroquine and fluoroquinolones. The researchers plan to carry out further studies to identify whether some quinolines may be less likely to induce quinolone resistance than others, and thus may be safer for malaria control programs. Dr Mike Silverman and 19 other volunteer health care professionals traveled by airplane from Bartica, a town that serves as the gateway to the interior of the Guyanese rainforest, to a handful of remote villages as part of annual humanitarian medical missions between 2002 and 2005. They took rectal swabs from 535 people in Bartica and the remote villages. They also asked the local inhabitants about whether they had ever been exposed to chloroquine or fluoroquinolones, and took water samples. They took the samples home and analyzed them. The team found that 5.4% of the rectal-swab samples contained ciprofloxacin-resistant Escherichia coli, with a 4.8% resistance rate among the remote-village samples. This is a very high rate – particularly when compared to the 4% rate found in a recent study of ciprofloxacin resistance in American intensive care units where fluroquinolones are very intensively used. It is also particularly remarkable because fluoroquinolones had never been available in these communities.

The ciprofloxacin-resistant E. coli samples were also all found to be highly resistant to chloroquine, and to have characteristics that would confer resistance to all fluoroquinolones including the newer drugs levofloxacin and moxifloxacin. Furthermore, the team found that one of the water samples they took in 2004 contained ciprofloxacin-resistant E. coli and another contained a small amount of chloroquine, probably from human waste contamination. Because of a widespread malaria outbreak in rural Guyana in late 2002, 30% of the villagers tested by the Canadian team in 2003 said they had been given chloroquine within the past six months, and in 2005 86% said they had used chloroquine within the past two years. The rates of chloroquine use may in fact have been much higher the investigators believe. This is because patient reports are not always reliable, and because of the very extensive treatment with chloroquine during the late-2002 malaria epidemic. The data also showed that community-wide fluoroquinolone resistance rose dramatically shortly after the malaria outbreak, further suggesting a link between chloroquine use for malaria and bacterial resistance to fluoroquinolones. Together, these data suggest that we must focus our efforts on prevention of malaria using mosquito-control measures such as bednets and by developing vaccines. For the short term, however, we still will have no choice but to use these lifesaving antimalarial drugs. However we need to investigate which of the antimalarials can be used in the future with the least impact on bacterial drug resistance.

Antimalarial Therapy Selection for Quinolone Resistance among Escherichia coli in the Absence of Quinolone Exposure, in Tropical South America. PLoS ONE 3(7): e2727
Bacterial resistance to antibiotics is thought to develop only in the presence of antibiotic pressure. Here we show evidence to suggest that fluoroquinolone resistance in Escherichia coli has developed in the absence of fluoroquinolone use. Over 4 years, outreach clinic attendees in one moderately remote and five very remote villages in rural Guyana were surveyed for the presence of rectal carriage of ciprofloxacin-resistant Gram-negative bacilli (GNB). Drinking water was tested for the presence of resistant GNB by culture, and the presence of antibacterial agents and chloroquine by HPLC. The development of ciprofloxacin resistance in E. coli was examined after serial exposure to chloroquine. Patient and laboratory isolates of E. coli resistant to ciprofloxacin were assessed by PCR-sequencing for quinolone-resistance-determining-region (QRDR) mutations. In the very remote villages, 4.8% of patients carried ciprofloxacin-resistant E. coli with QRDR mutations despite no local availability of quinolones. However, there had been extensive local use of chloroquine, with higher prevalence of resistance seen in the villages shortly after a Plasmodium vivax epidemic (p 0.01). Antibacterial agents were not found in the drinking water, but chloroquine was demonstrated to be present. Chloroquine was found to inhibit the growth of E. coli in vitro. Replica plating demonstrated that 2-step QRDR mutations could be induced in E. coli in response to chloroquine. In these remote communities, the heavy use of chloroquine to treat malaria likely selected for ciprofloxacin resistance in E. coli. This may be an important public health problem in malarious areas.