Antimicrobial Nanoparticles and MRSA

   by  EMSL "Zinc Oxide Particles"

A study done last year shows that certain nanoparticles can kill bacteria, even MRSA and other resistant strains. The nanoparticles are made with zinc oxide (ZnO) and titanium dioxide (TiO2). The researchers believe one of the ways these resistant species are so hard to control is their ability to form biofilms. Biofilms are large aggregates of bacteria that produce a matrix. The matrix protects some of the bacteria by not allowing antibiotics to come in to contact with the bacterial cells. The study focuses on the effectiveness of nanoparticles on the bacterial biofilms of MRSA.

Several isolates of MRSA that were shown to produce biofilms were cultured and allowed to aggregate. Commercially produced TiO2 and ZnO nanoparticles were introduced and the effects were measured. The particles had much greater inhibitory effects than all the antibiotics tested with it. Even low doses were better than most antibiotics, and some doses even prevented biofilms from forming. The results show that nanoparticles can be valuable tools to combat resistant bacterial strains. Using the particles to coat medical devices where biofilms readily form, like catheters, may prevent the formation of biofilms. Other possibilities for drugs or use with antibiotics should be researched further.

Antimicrobial Activity of Zinc and Titanium Nanoparticles against Biofilm Producing MRSA

Ants and Disease Transmission

   by  tarotastic 

Entomology and Biology professor David Hughes from Penn State was given the lead to find out if ants can teach us about the spread of disease in certain environments, such as large communal groups and offices. The National Science Foundation and the National Institutes of Health granted Dr. Hughes and his team a $1.8 million grant under the Ecology and Evolution of Infectious Diseases research initiative. The initiative "supports efforts to understand the underlying ecological and biological mechanisms that govern relationships between human-induced environmental changes and the emergence and transmission of infectious diseases."

The researchers will introduce various agents to ants and track the transmission. By varying the colony size and complexity, they hope to produce a mathematical model to expain the spread of diseases in populations that can eventually be used to predict transmission routes of human pathogens and help manage outbreaks. The team believes that ants can provide a reliable interactive community which to base the model on. Ants can be manipulated and colony size and structure can easily be changed to fit the goals of the researchers, and they're behavior is similar to other social groups.

A positive side effect of the study is an in-depth look at ant colony interactions. The social structures and methods of carrying out tasks could lead to a better understanding of how colonies react to insecticides that could be used to create more effective means of controlling pest ant species. The mathematical model of transmission could also be applied to livestock and agricultural diseases, leading to better prevention strategies and healthier animals and crops.

Penn State Study
Ecology and Evolution of Infectious Diseases Initiative

Infections From Cats

This weekend some friends finally got me to watch the BBC show "Sherlock". I know it's in its 3rd season, but I'm usually behind on things like this. Anyways, I've made my way through the 1st season, and its pretty good, even if some of the lab tests he performs are wrong or impossible, but that's another topic. In the 3rd (or last) episode, a woman dies from what seems to be an infection, but they are unable to figure out how she was infected. Watson visits her home and believes it was cat scratch. I'm not going to give away any more, but this got me thinking about cats. My family has had our share of cats, and along with that cat scratches. So what are some things you can get from your overly playful cat?

Cat scratch fever (Bartonellosis) is a bacterial infection caused by Bartonella henselae. It is the most common bacterial disease acquired from cats. The bacteria are commonly found in cats and don't usually cause a disease until it enters into the bloodstream. Fleas can also transmit the bacteria. Kittens are the most prone to harboring the bacteria and causing an infection in people or spreading it to other cats. Cats can also carry Salmonella and can infect through a scratch.

Cats may also have dirt in the claws, which can have a lot of bacteria found in soil that are pathogenic. The genus Clostridium lives in the soil and can cause tetanus and botulism. Bacillus can cause serious infections, including anthrax. Listeria and Camplybactor may be found and can also be transmitted via cat scratches.

This is not a comprehensive list, but just some common infections that can be passed from cats to humans.

Cornell Veterinary College
Soil-Related Bacterial Infections

UPDATE: Chikungunya Virus

Over the last week four more cases of Chikungunya virus have been reported in Alabama, along with the Huntsville case last week. One of those cases was in Birmingham. So far, all the people infected were travelers to parts of the Caribbean and no cases of infection from Alabama mosquitoes have been reported. However, the disease can cause relatively mild symptoms that may seem like allergies and a bad week of arthritis, which may prompt some people to stay at home instead of going to the doctor, so the exact number of actual cases is unknown.

There is still worry that the virus will spread to mosquitoes in the Southeast and an outbreak will occur. The CDC recommends following mosquito bite prevention guidelines, which can be found on their website and in the previous post. The CDC also urges anyone who has a fever and joint pain to see a doctor. There is no treatment and symptoms go away in about a week, but it is important that clinicians correctly identify cases of the virus so the infection patterns and numbers can be used to gather information and monitor its spread.

Certain Caribbean regions have been assigned Precaution Level 1 because of Chikungunya virus outbreaks. Anyone traveling to the Caribbean or South America should look up the region on the CDC Traveler's Page, which has information on current outbreaks and how to best prepare for travel to those regions.

CDC Mosquito Bite Prevention Guidelines

• Use air conditioning or window/door screens to keep mosquitoes outside. If you are not able to protect yourself from mosquitoes inside your home or hotel, sleep under a mosquito bed net.
• Help reduce the number of mosquitoes outside your home or hotel room by emptying standing water from containers such as flowerpots or buckets.
• When weather permits, wear long-sleeved shirts and long pants.
• Use insect repellents.
• Repellents containing DEET, picaridin, IR3535, and oil of lemon eucalyptus and para-menthane-diol products provide long lasting protection.
• If you use both sunscreen and insect repellent, apply the sunscreen first and then the repellent. 
• Do not spray repellent on the skin under your clothing.
• Treat clothing with permethrin or purchase permethrin-treated clothing.
• Always follow the label instructions when using insect repellent or sunscreen.

AL.com 4 More Virus Cases
CDC Chikungunya Virus
CDC Traveler's Page

Chikungunya Virus in the Southeast

The virus is transmitted by the yellow fever mosquito, which also carries yellow fever and dengue fever. The virus can cause fever and joint pain that can be debilitating in severe cases. The virus cannot be transmitted between people, but only by mosquito bite. There is no vaccine against it. Chikungunya outbreaks have been reported in several Central American and Caribbean countries in the past two years. So far, all the reported cases in the U.S. have been by travelers to countries where the virus is established.

The virus can spread by a mosquito biting someone infected and then biting someone without the disease. The CDC is worried that the virus will spread to the United States from either infected mosquitoes from Caribbean countries or from infected individuals introducing the virus into the yellow fever mosquitoes already found in the United States, and possibly other mosquito species.

Symptoms develop within 3 to 7 days of infection. The fever usually lasts a few days to a week, but the joint pain may last more than a month. Anyone with a fever, headache, rash, and/or joint pain should go to a doctor.

The CDC gives guidelines to prevent mosquito bites and possible infection.

• Use air conditioning or window/door screens to keep mosquitoes outside. If you are not able to protect yourself from mosquitoes inside your home or hotel, sleep under a mosquito bed net.
• Help reduce the number of mosquitoes outside your home or hotel room by emptying standing water from containers such as flowerpots or buckets.
• When weather permits, wear long-sleeved shirts and long pants.
• Use insect repellents.
• Repellents containing DEET, picaridin, IR3535, and oil of lemon eucalyptus and para-menthane-diol products provide long lasting protection.
• If you use both sunscreen and insect repellent, apply the sunscreen first and then the repellent. 
• Do not spray repellent on the skin under your clothing.
• Treat clothing with permethrin or purchase permethrin-treated clothing.
• Always follow the label instructions when using insect repellent or sunscreen.

CDC Chikungunya virus
 AL.com First Alabama Virus Case

Yersinia Infections in Transfusions

  by  makelessnoise 

Yersinia enterocolitica is a human pathogen that affects the G.I. system. It causes fever, diarrhea, and abdominal pains, and can sometimes be mistaken for appendicitis and is usually spread by contact with fecal material. However, it is a very important infection in blood banking, as it is the leading cause of post-transfusion septic infections.

Y. enterocolitica is a common contaminant is stored blood. The bacteria has several adaptions that allow it to thrive under the conditions blood is stored. Yersinia species are siderophilic, meaning they like high-iron environments, as is in stored blood. Y. enterocolitica can survive and even reproduce in temperatures down to -2C, allowing them to grow at the refrigerated temperatures blood is stored. The bacteria use glucose and adenine, found in storage additives, for metabolism and growth, and have an optimal pH of 7.0 – 8.0, and blood is stored around 7.3. It has been shown calcium prevents growth of pathogenic Yersinia but only above 30C, so blood stored with a calcium chelated anticoagulant does not prevent infection.

Y. enterocolitica can cause an asymptomatic infection in the intestines that disseminates to the blood, which is how is eventually contaminates stored blood. Donors who are asymptomatic or who have bacterial counts low enough to not present symptoms are not routinely screened. The bacteria do not actively cause sepsis, but trigger a major generalized inflammatory response, thought to be the result of a cell wall component that strongly binds to and activates macrophages, who initiate a cytokine cascade throughout the body.

Serologic donor testing is expensive and infections caused by Y. enterocolitica is relatively rare. The simplest ways to prevent post-transfusion infections from the bacteria are not allowing donors the give blood if they do not feel well or have any signs of infection, not giving blood older than 3 weeks to susceptible recipients because the  bacteria take 3 to 4 weeks to reach dangerous levels in refrigerated blood, and using pre-storage leukocyte-reducing techniques because the bacteria have a strong affinity for WBCs.

http://www.ncbi.nlm.nih.gov/pubmed/21865196

Sous-vide Cooking and Bacteria

I have a confession: I love to cook. It's a combination of art and science, and you can eat the final product! My favorite aspect of cooking is food science and learning the processes that take raw ingredients and turn them into food, and I read a lot about modern and next gen cooking techniques. That's how I learned about and started using sous-vide.

  by  AustinMatherne 

Sous-vide is a cooking method like baking, broiling, or grilling. Food is placed into a vaccum-sealed bag and usually submersed in a water bath. The water is kept at a precise temperature using some type of heater/thermostat combination and the food is cooked by heat diffusion through the bag. The food cooked this way is not soggy, the flavors are sealed with the food, and extremely specific temperatures can be used. Most sous-vide is done with meat. Steaks can be cooked to a perfect medium-rare just by setting the temperature to the correct degree. And because the water, and therefore the food, never exceeds that temperature and no moisture is lost, food can be left in it for days without overcooking. The problem is most sous-vide cooking takes place between 120F to 150F; in the bacterial danger zone.

The theory behind preparing food safely is bacteria don't have a thermometer that kills them only if a certain temperature is reached. There are charts, graphs, and computer models that predict the death rate of certain food-borne pathogens, and the rate is a curve. Cooking chicken to 165F kills salmonella in a few seconds, but it take several minutes to completely kill at 150F. So theoretically, as long as you let food sit in the water bath long enough, it will pasteurize it and be as safe as conventional cooking, while being juicer and more tender.

However, most models for recommended cooking times do extend into the low temperatures that sous-vide uses. Many publications exist, but few actually link scientific or regulatory reports for the cooking times. Here is a page from a popular sous-vide immersion circulator company that lists times and temperatures, but the only source is a link to the FDA homepage. Most cooking times are based on the old models for high temperature, so the temperatures are not approved by food agencies. But the Institute of Food Research in the UK and the USDA/FDA have both begun programs to update the current models to include low temperature cooking.

I personally don't have a problem with sous-vide and have made several meals at home without any problems using the times provided from other chefs, as have many other people. I will continue to use sous-vide as an alternative cooking method and use safe food-handling practices when cooking to keep the risk for contamination low.

Douglas Baldwin: A Practical Guide to Sous Vide Cooking

Institute of Food Research Bacterial Growth Model Study pdf