Norovirus: Como y donde se disemina. Un cuadro más claro.

Análisis de datos recolectados por casi dos décadas entregan información importante acerca de cómo se comportan los brotes de este patógeno.

Norovirus, un microorganismo que produce enfermedad gastrointestinal, es responsable de cerca de un 12% de las enfermedades diarreicas en el mundo y cada año causa un estimado de 218.000 muertes entre niños menores de 5 años.

Un nuevo estudio publicado en la revista “Epidemiology and Infection” (Epidemiología e Infección) ofrece una mejor visión de la que se tenía hasta ahora acerca de cómo este virus se disemina, y cuales son sus fuentes u orígenes.

El norovirus deriva de la materia fecal y puede infectar a las personas por 4 vías principalmente: agua contaminada, alimentos contaminados, superficies contaminadas o por el contacto con personas infectadas.

Investigadores de la Universidad de Michigan y de Emory analizaron datos de 902 brotes de norovirus documentados entre los años 1993 y 2011, encontrando que la mayoría de ellos se asociaban a transmisión por medio de comida en servicios de alimentación. Los casos menos comunes fueron los asociados a superficies contaminadas en colegios o lugares de cuidados de niños.

Uno de los factores que analizó el estudio fue “la tasa de ataque” de un brote, es decir, cuantas de las personas que fueron expuestas al virus son infectadas. Los brotes asociados a alimentos y servicios de alimentación son los que presentaron un mayor índice en tasa de ataque, seguido de los brotes asociados al consumo de agua contaminada.

De acuerdo a los investigadores, esto podría deberse al hecho de que las personas expuestas a este tipo de rutas (alimentos y agua) consumen dosis infectantes mayores del virus. Otro motivo de porque estos brotes tienen tasas de ataque totales mayores es que es más fácil hacer la asociación entre población afectada y fuente de contagio (todas las personas que han consumido el alimento contaminado), mientras que en un brote donde el contagio es de persona a persona el número de personas expuestas es muy difícil de cuantificar.

Los lugares donde se cuidan niños (enfermerías, casinos de colegios, jardines infantiles) son los que presentaron las tasas más bajas, lo que posiblemente se debe a que las medidas de aseo y sanitización son más estrictas que en otros lugares. Por otra parte, este escenario está asociado con un bajo número de casos primarios (casos en donde el paciente enfermo fue infectado a partir de la fuente original del brote).

Lo mismo ocurre con los casos de brotes asociados a alimentos y servicios de alimentación. Esto sugiere que la transmisión viral en un lugar confinado (como un restaurant, un casino, etc) puede limitar los casos primarios solo a las personas que comparten ese espacio.

Los brotes cuyo origen es el agua de bebida contaminada, por otro lado, tienen una mayor cantidad de casos primarios dado que la fuente puede alcanzar a toda una comunidad, al igual que en los caos de contagio de persona a persona cuando una persona infectada se convierte en una fuente de exposición móvil.

El estudio también confirmó un link entre brotes de norovirus y las estaciones del año. Aquellos brotes con una sola ruta de transmisión suelen presentar altas tasas de ataque en invierno, mientras que aquellos con múltiples rutas presentan tasas de ataque mayores en primavera.

Fuente: http://www.foodsafetynews.com/2012/03/norovirus---how-and-where-it-spreads/

Sistema de sanitización por ultrasonido: Una alternativa para la producción de alimentos orgánicos inocuos

El uso de ultrasonido de alta potencia elimina E. coli 0157:H7 en los alimentos orgánicos

El efecto bactericida del ultra sonido se conoce de la década de los 20` y se basa en una cavitación celular que deriva en la lisis dada por las compresiones y descompresiones alternas de la célula bacteriana. El campo de acción de ésta técnica es múltiple pero ahora se ha enfocado al área de alimentos orgánicos, con el fin de evitar la proliferación de microorganismos patógenos en ellos.

Granjeros de alimentos orgánicos en California están trabajando con investigadores del Institute of Food Safety and Healt h (IFSH) –con sede en Chicago- para desarrollar un nuevo sistema de sanitización mas “amigable” con los productos orgánicos de manera tal que se consiga de manera segura y confiable la tan anhelada inocuidad alimentaria. Ellos están llevando a cabo pruebas piloto,  utilizando ultrasonido de alta potencia (HPU; sigla en inglés) combinándola con el efecto microbicida de dos desinfectantes uno en base a ácido peracético y otro en ácido cítrico -ambos agentes permitidos para su uso en procesos orgánicos- para verificar las actividad que provoca su uso sobre alimentos contaminados con distintos patógenos. La aplicación del sistema HPU consiste en la creación de pequeñas burbujas en la solución desinfectante las cuales estallan al entrar en contacto con la superficie del alimento, logrando la lisis de cualquier tipo de patógeno presente en esta; siendo muy útil para evitar la aparición de E. coli 0157:H7 en los alimentos orgánicos.

Will Daniels, vicepresidente de operaciones e integridad orgánica dice: “se ha visto un aumento considerable en la eficacia del sistema de lavado con HPU que sin éste. Estamos testeando el uso de HPU con sanitizantes en base a ácido peracético y cítrico para  evitar el uso de compuestos clorados para el lavado, dado que dejan muchos residuos en el alimento y reglamentariamente éstos no deben superar las 4 partes por millón de Cloro”

El sistema de ultrasonido de alta potencia  aun no ha sido implementado en las granjas pero se espera que pronto se adopte como una técnica de múltiples enfoques para lograr de forma segura y confiable la producción de alimentos inocuos. A propósito de aquello Daniels agrega “Su aplicación solo sería un paso más para garantizar la seguridad de los productos orgánicos para ensaladas que entran al mercado, dado que estos son alimentos frescos que se consumen crudos; siendo muy importante el rol de la higiene en la manipulación por parte de los consumidores”

Fuente: Food Safety

Aporte: Francisco Pérez

Dr. Elisabeth Hagen explains the new policy on non-O157 STEC (Shiga Toxin-producing E. coli).

Dr. Elisabeth Hagen explains the new policy on non-O157 STEC (Shiga Toxin-producing E. coli).

Q: Can you give us a little bit of the background - some of the back story or detail that we maybe haven't heard - on how the non-O157 policy was developed?
A:  It's been going on for longer, in April of 2006 we had some illness cases of O103 in New York and we thought they might have been connected to beef. It started a series of inquiries: How are states handling this? What kind of surveillance is out there? And how come this state does it differently from that state?.

We just started digging for information and eventually presented it to Dr. Raymond who was the under secretary at the time. The first time we talked about it in October 2007. We brought together the clinical perspective, the state perspective and the international perspective in, because other countries had dealt with outbreaks we hadn't yet dealt with. We were learning that the states that were looking for it were finding non-O157 STECs in really significant numbers. And in some cases much higher numbers than O157.
We didn't have any detection capabilities, either for our labs, or commercial detection kits available. So we spent two years working with Agricultural Research Service so that we would have the right technology to find them in meat, and to be able to find them in a rapid turnaround, while not having a massive impact on production.
Once we got those things in place, then the data just kept adding up. CDC released new burden estimates for the first time in a decade and non-O157 was showing up at twice the rate of O157. The Food Net data came out for 2009 and it was very clear that things were on the upswing, and then the 2010 numbers for the first time ever showed non-O157 exceeding O157.

Q: Were you surprised by the very public push back from the industry, which argues that this isn't needed, it won't benefit public health, and it will impact trade?
A:  In the beginning, industry had a lot of questions: How strong is the science? What is this going to mean for us? How much is this going to cost us? Is this really going to help? I don't think we were that surprised about the questions. There are so many great leaders in the industry who are totally headed in the right direction on this. But there's a small group that continues to advocate against our ability to protect consumers from something we know doesn't belong in the food supply.

Q:  How much discussion has there been on the trade implications, could this potentially be a WTO issue?
A:  The question that we had to answer in terms of trade was: Do we have a scientific basis for what we're doing?. In fact, what's required is that we have a scientific basis for what we're doing -- that we're not doing something protectionist.
We're tackling a domestic challenge, first and foremost, and as you know the way equivalency works, importing nations are going to have to meet the same challenges we're meeting. It's something we definitely have to think about, but I think we're in a good place. I'm not concerned about us not being able to stand behind the scientific basis of our decision-making.

 Source: www.foodsafetynews.com/
Aporte: Eduardo Castillo

Advisory Committee Discusses New School Ground Beef Safety Criteria

The National Advisory Committee on Microbiological Criteria for Foods (NACMCF), held a meeting Wednesday to discuss ground beef purchasing requirements for federal food and nutrition assistance programs and unanimously accepted the group's recommendations on safety questions raised by the U.S. Department of Agriculture's Agriculture Marketing Service (AMS).

AMS asked NACMCF three questions to help develop microbiological criteria, pathogen testing methodology, and sampling plans for the National School Lunch Program ground beef purchases for 2012-2013:

1. AMS is considering elimination of the requirement to test for Staphylococcus aureus from the Federal Purchase Ground Beef Program and AMS asks NACMCF to provide considerations and scientific discussion regarding this action with respect to public health.

The committee concluded that the exclusion of S. aureus-specific testing will not negatively impact the safety or quality of ground beef in the National School Lunch Program and recommended that the "criterion be removed from the Federal Purchase Ground Beef Program."

2. Should AMS consider the use of alternative screening procedures beyond those stipulated in the FSIS Microbiology Laboratory Guidebook (MLG), and if so, would the AMS testing program results be comparable to FSIS' verification testing programs, and therefore useful to FSIS? What should be considered in distinguishing acceptable and unacceptable alternative screening procedures? Is it appropriate to allow alternative sample preparation procedures (portion size, enrichment broth, portion to broth ratio, enrichment time and temperature) which differed from the MLG, or which differed by AMS designated laboratory?

The committee recommended that AMS consider using validated alternative screening methods to "reduce the level of false-positive results and allow for more rapid release of raw product."

3. AMS asks NACMCF to evaluate boneless beef and finished product compliance program lotting and frequency of testing for pathogens and indicators of process control for both raw ground beef to be cooked on-site at schools.

The committee recommended that AMS "maintain high standard supplier control, HACCP implementation, carcass testing, traceability, etc as in current program." Adding, "With the exception of S. aureus testing, no changes to testing of indicator organisms are recommended at this time." The committee also said that, regardless of sampling program, ongoing program review needed to be strengthened.

Source: Food News Safety

CDC research shows outbreaks linked to imported foods grew in the last decade

Vegetables, seafood and processed food products the most common sources
Foodborne disease outbreaks caused by imported food appeared to rise in 2009 and 2010, and nearly half of the outbreaks implicated foods imported from areas which previously had not been associated with outbreaks, according to research from the Centers for Disease Control and Prevention, presented today at the International Conference on Emerging Infectious Diseases in Atlanta.
CDC experts reviewed outbreaks reported to CDC’s Foodborne Disease Outbreak Surveillance System from 2005-2010 for implicated foods that were imported into the United States. During that five-year period, 39 outbreaks and 2,348 illnesses were linked to imported food from 15 countries. Of those outbreaks, nearly half (17) occurred in 2009 and 2010. Overall, fish (17 outbreaks) were the most common source of implicated imported foodborne disease outbreaks, followed by spices (six outbreaks including five from fresh or dried peppers). Nearly 45 percent of the imported foods causing outbreaks came from Asia.
According to a report by the Department of Agriculture's Economic Research Service (ERS), U.S. food imports grew from $41 billion in 1998 to $78 billion in 2007.  Much of that growth has occurred in fruit and vegetables, seafood and processed food products.  The report estimated that as much as 85 percent of the seafood eaten in the United States is imported, and depending on the time of the year, up to 60 percent of fresh produce is imported. ERS also estimated that about 16 percent of all food eaten in the United States is imported. The types of food causing the outbreaks in this analysis aligned closely with the types of food that were most commonly imported.
 Recently, the Food and Drug Administration has have stepped up its efforts to conduct environmental assessments to determine the root cause of outbreaks. With lessons learned from outbreaks, measures will be taken to prevent such outbreaks in the future.  The newly enacted FDA Food Safety Modernization Act is also a major step in establishing a prevention based food safety system that would address domestic as well as imported foods. CDC, FDA and USDA will continue to work together to prevent foodborne illness and stop harmful products from entering commerce.

 Additional information on CDC’s foodborne outbreak surveillance is available at: http://www.cdc.gov/outbreaknet/surveillance_data.html

Clostridium difficile an emergent food pathogen

New virulent strains produce high doses of toxins and cause severe colitis and deaths in the elderly

The prevalence of C. difficile infection has been increasing steadily particularly in the elderly. There have been reports from several hospitals of a newer, more virulent strain of C. difficile bacteria that produces large amounts of both toxins A and B and as well as a third toxin. This strain produces more severe colitis than the usual strains. Patients infected by this strain are more seriously ill, require surgery more frequently, and die from the infection more frequently than patients infected with the usual strains. Currently, the commercially available diagnostic tests cannot distinguish this strain from the usual strains.

Traditionally, antibiotic use is often considered the most important factor for the development of C. difficile colitis. Increasingly though doctors are diagnosing C. difficile colitis in patients without antecedent antibiotic exposure. This is especially true in patients with Crohn's disease or ulcerative colitis. In one study of 92 patients with ulcerative colitis and Crohn's disease relapse, 10 patients tested positive for C. difficile. Another change that is occurring with C. difficile infection is that it is no longer restricted to patients in hospitals or nursing homes. Up to one-quarter of infections begin out of the hospital.

Doctors are witnessing increasing difficulty in treating C. difficile colitis. Firstly, resistance to metronidazole is on the rise. Secondly, colitis (along with symptoms of diarrhea and cramps) is taking longer to resolve and may require higher doses of vancomycin. Thirdly C. difficile colitis relapse (with recurrent diarrhea) is common. More troublesome still, many patients experience multiple relapses, often requiring prolonged (months) antibiotic (such as vancomycin) treatment.

Source: http://www.medicinenet.com/clostridium_difficile_colitis/page7.htm#new

Mayor Bloomberg announces decrease in foodborne illness and increase in restaurant revenue since letter grading began.

Salmonella Cases Fall 14% and Revenue at Restaurants Up 9.3% since Grading Began

The reported Salmonella infections, an important indicator of foodborne illness, fell 14% during letter grading’s first full year to the lowest level in the last 20 years. In addition, total restaurant sales in New York City increased 9.3 percent – $800 million – in the first nine months since grading began compared to the year before. New York City’s restaurants have made significant improvements in food sanitary practices with more than 72 percent of the City’s restaurants earning “A” grades, up from 65 percent a year ago. The increase in “A” grades reflects fewer violations of public health standards such as inadequate hand washing facilities, food not being held at cold or hot enough temperatures and having conditions conducive to pests, according to a report on the program’s progress released today. The Mayor also released results of a new survey conducted by Baruch College at the City University of New York revealing that 91 percent of New Yorkers approve of grading and 88 percent of those surveyed consider letter grades when dining. And now restaurant grades are more accessible than ever with “ABCEats NYC,” a new app that lets New Yorkers check a restaurant’s letter grade from any street corner throughout the City. The Mayor made the announcement at Zero Otto Nove in the Bronx.
 “With restaurants making improvements, diners across the city have many more ‘A’ grade restaurants to choose from,” said Deputy Mayor Gibbs. “New Yorkers are paying attention to grades in restaurant windows and restaurant operators are clearly paying attention to food safety practices and cleanliness. Restaurants are making the grade and early results show foodborne illness is declining.”
 “The Health Department’s new ABCEats NYC app puts more power in the hands of New Yorkers, enabling them to make informed restaurant decisions, quickly and easily,” said Rachel Sterne, Chief Digital Officer, Mayor’s Office of Media and Entertainment. “Thanks to the GPS search, users benefit from fast, mobile access to inspection grades and detailed results. The Health Department is already a leader in digital engagement, and this is a great example of how technology can help New Yorkers take advantage of City services.”
Diners use the grades in their decision-making, as a new survey conducted by Baruch College at the City University of New York revealed, with 88 percent of those surveyed considering letter grades when dining out and 76 percent feeling more confident in a restaurant’s food safety if it has an “A” grade posted. The Baruch College poll also showed that 91 percent of New Yorkers approve of grading and 88 percent approve of the city’s approach of more frequent inspections for “B” and “C” graded spots than for restaurants earning “A”s. The survey consisted of a random sample of 511 New York City adults who were contacted by telephone from Jan. 31 through Feb. 5, 2012.
Beginning today, New Yorkers can check a restaurant’s letter grade from any street corner throughout the City using ABCEats NYC, a free iPhone, iPad and iPod Touch application that offers easy access to restaurant inspection grades and detailed inspection reports for each of the City's 24,000 restaurants. New Yorkers can find a restaurant’s latest inspection results by entering the name of a restaurant, searching by borough, or using their current location to find restaurants with “A,” “B,” “C,” or Grade Pending grades in close proximity. Global positioning system (GPS) technology on iPhones works with the City’s letter grading database to show letter grades of nearby restaurants. Information is updated daily.
To download the free ABCEats NYC application, those with Apple mobile phones or devices can search for ‘NYC Restaurant Grading’ in the iPhone App Store on their device. The app is available for iPhone and iPod users and will be available for Android users by this summer. For more information on the 18-month report on restaurant grading please search “Restaurant Grading at 18 Months” on NYC.gov.

http://www.nyc.gov/portal/site/nycgov/menuitem.c0935b9a57bb4ef3daf2f1c701c789a0/index.jsp?pageID=mayor_press_release&catID=1194&doc_name=http%3A%2F%2Fwww.nyc.gov%2Fhtml%2Fom%2Fhtml%2F2012a%2Fpr076-12.html&cc=unused1978&rc=1194&ndi=1

A PRINCESS Cruise Lines ship was forced to return to its Florida port overnight following a second outbreak of the highly-contagious Norovirus.

During the latest Crown Princess voyage, which set sail February 4, 226 passengers and 63 crew members contracted the gastrointestinal illness.
The cruise had been scheduled to visit Curacao and Aruba and enter port tomorrow but was forced to return two days early "to undergo an extensive two-day sanitization," the operator said.
"In consultation with the US Centers for Disease Control (CDC) ... it was agreed that this was the best course of action to stop the spread of the illness," it continued. "We sincerely regret having to cut short our passengers' cruise vacations because of this highly-unusual situation."
Staff members were set to begin the arduous task of cleaning the vessel in an attempt to rid it of the virus, which quickly spreads through person-to-person contact and via contaminated food and water.
"The enhanced disinfection of the ship in Fort Lauderdale will include bringing aboard additional cleaning crew to assist with a thorough sanitization of all public spaces and surfaces, including soft furnishing and carpets, railings, door handles and the like," the operator said.
The ship will return to sea for its next scheduled cruise Saturday, it added.
The previous cruise affected by the outbreak departed January 28, before returning February 4. Princess Cruise Lines said 364 passengers and 30 crew members contracted the virus.
The Crown Princess was not the only Florida-based cruise liner to suffer a norovirus outbreak recently. The Ruby Princess -- also a Princess Cruise Lines vessel -- returned to its Fort Lauderdale port February 5 after more than 100 passengers and crew became ill.
The Norovirus is a problem on cruise ships because it spreads more easily among large numbers of people concentrated in limited areas.
Symptoms include diarrhea, vomiting, nausea and stomach cramps, according to the CDC.
Source: http://www.heraldsun.com.au/news/breaking-news/cruise-ship-returns-to-florida-port-early-after-second-virus-outbreak/story-e6frf7jx-1226267436593

Whole-genome sequencing of 2011 E. coli outbreaks in Europe provides new insight

Study revealed small differences among the 
E. coli O104:H4 strains.
 

The outbreak in Germany, which was caused by the strain E. coli O104:H4, led to around 4,000 cases of bloody diarrhea, 850 cases of hemolytic uremic syndrome (HUS), which can lead to kidney failure, and over 50 deaths. The source of the outbreak was traced to sprouts from an organic farm in Germany. In France, where 15 people were sickened with bloody diarrhea that progressed to HUS in nine people, the source of the outbreak was sprouts, germinated from seeds purchased at a garden retailer, that were served at a children's community center buffet. European investigators, using traditional epidemiological methods, traced the outbreaks to a shipment of seeds from Egypt that arrived in Germany in December 2009.

The researchers analyzed isolates of E. coli from both the German and French outbreaks. Based on conventional molecular epidemiological analysis, the E. coli strains from the outbreaks in Germany and France appear identical. However, by the whole-genome sequencing and analysis allow to determine that there were small, but measurable, differences among the isolates. They found two surprising findings: All the strains connected to the larger German outbreak were found to be nearly identical, while the strains in France showed greater diversity; and the German isolates appeared to be a subset of the diversity seen in the French isolates.
 

If genomes have fewer differences than we expect, like the German outbreak, it suggests that the outbreak might have passed through a single bottleneck. A bottleneck might be something like disinfection procedures that killed most but not all of the bugs, or maybe passage through a single infected individual.

Another hypothesis offered by the researchers is that there was uneven distribution of diversity in the original shipment of contaminated seeds.

As costs for genomic sequencing decline, these tools, combined with traditional epidemiological techniques, can provide greater insight into the emergence and spread of infectious diseases and will help guide preventive public health measures in the future.
 

Source: http://www.eurekalert.org/pub_releases/2012-02/hsop-wso020612.php

Drug-Resistant Staphylococcus aureus linked to animal antibiotics

Multi resistant strains causes severe infections in humans
A study recently published in MBio lends further weight to the growing theory that using animal antibiotics in livestock contributes to drug resistance among human bacteria.
Methicillin-resistant Staphylococcus aureus, or MRSA, is a strain of Staph that's resistant to methicillin - the drug most commonly used to treat Staphylococcal infections. 
Using a detailed DNA mapping technique, researchers at the Translational Genomics Research Institute (TGen) in Arizona were able to trace one of these superbugs - MRSA CC398 - to its origins, discovering that the human strain of this pathogen developed its drug resistance in animals rather than in people.
Often referred to as "pig-MRSA" or "livestock-associated MRSA," the strain is known to affect humans who have been exposed to live animals, such as farmers or veterinarians. But this study found that CC398 was originally a human bacterium, susceptible to antibiotics, before it spread to animals and then back to people. By the time it returned to humans it had picked up two souvenirs: resistance to methicillin and resistance to tetracycline - a drug often used to treat Staphylococcus aureus infections in patients allergic to the penicillin class of antibiotics, which includes methicillin.  
Because both tetracycline and penicillin are commonly administered to food animals, the study finds that it is likely that the use of these drugs in livestock gave Staphylococcus aureus the exposure it needed to develop resistance to these drugs.
In 2010, Tetracycline - used to promote growth and prevent the spread of disease - comprised over 42 percent of all antibiotics administered to food-producing animals in the United States. That year 12,328,520 pounds of the drug were given to animals, while just over 100,000 pounds of the drug are sold for human use. And while over 1.9 million pounds of penicillin were sold for animal use in 2010, approximately 1.5 million pounds are distributed for human use. 

Source: MBio, ASM