Infection strategies for single Salmonella in human cells

Posted on November 21, 2016 by Douglas Powell

University of Würzburg researchers have used new technology to provide insight into how single Salmonella infect human cells. The study has just been published in “Nature Microbiology”.

Some bacterial pathogens such as Salmonella invade and replicate within human cells. Science is steadily shifting its focus towards studying infected cells and how differences between individual host cells affect the cellular response to pathogens.

A research team headed by Professor Jörg Vogel from the University of Würzburg has made significant progress in this area. They have developed a novel technique that allows them to investigate the interplay of individual host cells with infecting bacteria.

The team used a technique called “single-cell RNA-seq” to study the infection of macrophages by Salmonella. Macrophages are immune cells that belong to the group of white blood cells; Salmonella are pathogenic bacteria that may be taken up by the ingestion of contaminated water or food to cause local gastroenteritis and diarrhea. In immunocompromised patients however, Salmonella may disseminate throughout the entire body and cause life-threatening diseases.

Upon the invasion of macrophages, Salmonella pursue two strategies: The bacteria either replicate to high numbers inside the host cell or adopt a non-growing state that allows them to persist for years within the body of their host. “This disparate growth behavior impacts disease progression and plays a major role in the success of antibiotic treatment” says lead researcher Jörg Vogel.

To date, very little is known if and how macrophages respond to these disparate lifestyles of intracellular Salmonella. To answer this question the Würzburg scientists cultured macrophages in the laboratory and infected them with Salmonella.

The RNA from the infected cells was subsequently extracted and analyzed using deep-sequencing, leading to the detection of more than 5,000 different transcripts per macrophage. These data on the host’s gene expression were combined with information about the growth behavior of the intracellular pathogens.

The results: Macrophages containing non-growing bacteria adopt the hallmark signature associated with inflammation. They express signaling molecules to attract further immune cells to the site of infection. In this respect, they respond similarly to macrophages that have encountered Salmonella, but have not been infected. “These macrophages cannot detect their intracellular bacteria – they are below their radar” explains Emmanuel Saliba, first author of the study.

Salmonella typhimurium Color Enhanced, TEM

In contrast, macrophages with fast-growing bacteria develop an anti-inflammatory response. These interesting results open many questions, Do Salmonella induce this different response? Do they manipulate the macrophages so they do not raise the alarm to facilitate the bacteria to evade an immune response? Are there situations where Salmonella are unable to perform this trick? In these cases, will there still be an immune response forcing the bacteria to switch to their resting growth state?

“Currently we have just looked at a single time point after infection and thus cannot differentiate between cause and consequence” explains Alexander Westermann, another member of the team. Follow-up studies are required. Nevertheless, the current findings already provide a new perspective on the host response to pathogenic microbes. And using the new technology, bacterial infections can be studied in unprecedented resolution – namely on the single-cell level.

Norovirus sucks; here’s what it does to the body

Posted on October 15, 2016 by Ben Chapman

It’s the perfect human pathogen.

A 2015 CDC report on noro burden by Ben Lopeman describes the virus as “ubiquitous, associated with 18% (95% CI: 17-20%) of diarrheal disease globally, with similar proportions of disease in high- middle- and low- income settings. Norovirus is estimated to cause approximately 200,000 deaths annually worldwide, with 70,000 or more among children in developing countries.”

Express describes what happens when the virus infects.

The viral particles hit the stomach first, but it is only when they travel into the small intestine that the virus begins to multiply.

It enters the cells lining the intestine, making copies of itself and then the cells die, release more virus particles, and the process is repeated.

The immune system recognises that cells are ‘dying’ and as an immune response, antibodies travel to the small intestine and deactivate the virus. Experts say this is when the body will start to feel the effects of the virus – such as fever and nausea.

The virus causes the gut to become inflamed or irritated – which leads to vomiting and watery diarrhoea. This, medics say, is the body’s way of fighting the infection and trying to clear it from the body.

Could Alzheimer’s stem from infections like Salmonella

Posted on May 26, 2016 by Douglas Powell

Gina Kolata of The New York Times reports on new research by a team of investigators at Harvard which suggests Alzheimer’s disease stems from the toxic remnants of the brain’s attempt to fight off infection.

It is still early days, but Alzheimer’s experts not associated with the work are captivated by the idea that infections, including ones that are too mild to elicit symptoms, may produce a fierce reaction that leaves debris in the brain, causing Alzheimer’s. The idea is surprising, but it makes sense, and the Harvard group’s data, published Wednesday in the journal Science Translational Medicine, supports it. If it holds up, the hypothesis has major implications for preventing and treating this degenerative brain disease.

The Harvard researchers report a scenario seemingly out of science fiction. A virus, fungus or bacterium gets into the brain, passing through a membrane — the blood-brain barrier — that becomes leaky as people age. The brain’s defense system rushes in to stop the invader by making a sticky cage out of proteins, called beta amyloid. The microbe, like a fly in a spider web, becomes trapped in the cage and dies. What is left behind is the cage — a plaque that is the hallmark of Alzheimer’s.

So far, the group has confirmed this hypothesis in neurons growing in petri dishes as well as in yeast, roundworms, fruit flies and mice. There is much more work to be done to determine if a similar sequence happens in humans, but plans — and funding — are in place to start those studies, involving a multicenter project that will examine human brains.

“It’s interesting and provocative,” said Dr. Michael W. Weiner, a radiology professor at the University of California, San Francisco, and a principal investigator of the Alzheimer’s Disease Neuroimaging Initiative, a large national effort to track the progression of the disease and look for biomarkers like blood proteins and brain imaging to signal the disease’s presence.

The work began when Robert D. Moir, of Harvard Medical School and Massachusetts General Hospital, had an idea about the function of amyloid proteins, normal brain proteins whose role had long been a mystery.

The proteins were traditionally thought to be garbage that accumulates in the brain with age. But Dr. Moir noticed that they looked a lot like proteins of the innate immune system, a primitive system that is the body’s first line of defense against infections.

Elsewhere in the body, such proteins trap microbes — viruses, fungi, yeast and bacteria. Then white blood cells come by and clear up the mess. Perhaps amyloid was part of this system, Dr. Moir thought.

He began collaborating with Rudolph E. Tanzi, also at Harvard Medical School and Massachusetts General Hospital, in a study funded by the National Institutes of Health and the Cure Alzheimer’s Fund. The idea was to see if amyloid trapped microbes in living animals and if mice without amyloid proteins were quickly ravaged by infections that amyloid could have stopped.

The answers, they reported, were yes and yes.

In one study, the group injected Salmonella bacteria into the brains of young mice that did not have plaques.

“Overnight, the bacteria seeded plaques,” Dr. Tanzi said. “The hippocampus was full of plaques, and each plaque had a single bacterium at its center.”

In contrast, mice that did not make beta amyloid succumbed more quickly to the bacterial infection, and did not make plaques.

I’m missing something here: NJ school closed due to staff with C. difficile?

Posted on January 13, 2015 by Ben Chapman

According to NBC 10, Perth Amboy’s William McGinnis Middle School is closed for cleaning and sanitizing as a staff member was found to have C. difficile.

Perth Amboy’s William McGinnis Middle School remains closed while it undergoes an extensive cleaning after an adult who works there was diagnosed with a germ that causes infectious diarrhea.

The school was closed as a precaution on Friday after the woman was sent home on Thursday. The district says she has an intestinal bacillus known as clostridium difficile.

The district did not release her name or say what her job is.

The district says it has hired a company to completely disinfect the school and classes are scheduled to resume on Thursday.

Closing a school for C. difficile is a new one to me.

Maybe they mean norovirus, I dunno.

In a 2009 review of C. difficile infections, Rupnik, Wilcox and Gerding suggest that the pathogen is out there (environmentally and in food) but risk factors for acquiring the pathogen include the use of antibiotics and hospital stays. Not going to a school where someone has the bug.

Hospitalization is a risk because it brings together multiple major [C. difficile infection] CDI risks, including exposure to antibiotics, a spore-contaminated environment, inadequate hand hygiene by health care workers and a highly susceptible elderly population of patients

Possible community sources for CDI include soil, water, pets, animals used for food, meats and vegetables. There is no conclusive evidence that C. difficile contamination of food has led to clinical CDI in humans.

I wonder if they will be using hydrogen peroxide to disinfect (it’s not too common outside of healthcare).

Bring holiday cheer, not norovirus, into care settings

Posted on December 9, 2014 by Ben Chapman

As North Carolinians (and others) get into the festive season, kids (like mine) are visiting retirement residences and nursing homes to bring holiday cheer.

And they also might be bringing norovirus.

Today I brought Sam (below, exactly as shown) to a local care center so he and his preschool classmates could sing carols to residents.

Heightened to noro season and control measures I looked for messages around ill visitors. I didn’t see any but I did see some off-the-shelf hand sanitizer that wouldn’t do much to the non-enveloped virus.

In related news, BBC is reporting that Scottish hospitals are asking visitors who have recently been ill to stay away. Something that I’ll suggest to Sam’s preschool organizers.

NHS Greater Glasgow and Clyde (GGC) said people ignoring the advice could end up passing on symptoms to patients.

The appeal is part of wider attempts to minimise the effects of norovirus in hospitals across the area.

Visitors are also being reminded about the “importance of hand hygiene when entering and leaving” hospitals.

Prof Craig Williams, lead infection control doctor at NHS GGC, said: “We understand that when a relative or friend is in hospital you want to offer them comfort and support by visiting them.

“Unfortunately visiting a loved one if you have experienced sickness and diarrhoea in the last 48 hours can have consequences for the person you are visiting. They would potentially catch whatever infection you have leading to their health being compromised.

“We are asking people not to visit friends or relatives in hospital if they have experienced any sickness or diarrhoea in the last 48 hours.”

Prof Williams added: “Norovirus is particularly prevalent during the winter and it’s not unusual to see this type of virus in the community.

Culture change isn’t about training, education and environment

Posted on July 21, 2014 by Ben Chapman

Over the past decade lots of folks have been throwing around the term food safety culture to describe how a business operates. Education, training, equipment, tools, the environment, investment and support from higher-ups all influence how well an organization addresses risk, there’s something else that binds it together.

The culture, or value system, can be difference between having an outbreak or not. The values dictate decisions from the front-line staff to the CEO.

Maybe it’s the hippie in me but it’s sort of like the vibe of the organization that can be gauged by asking does anyone really care?

images-1

And if they do, do they know what they should be caring about?

The health care world struggles with the same issues, with similar consequences. According to Yahoo News the Vanderbilt University Hospital dealt with a culture change around infection control. And it’s taken six years to turn things around.

Dr. Gerald Hickson had two primary concerns after his wife’s double-knee replacement operation at Vanderbilt University Hospital in July 2008: making sure she received appropriate pain control and getting her moving as quickly as possible to avoid blood clots. But as he sat with her during her recovery, Hickson made a disturbing discovery. Most of the nurses, doctors and other hospital workers filing in and out of the room to care for his wife, who was at risk of contracting an infection after surgery, were not washing their hands.

A compulsive person by nature, Hickson started counting. He found 92 instances when staff members should have soaped up or used antiseptic foam. The total number of times they actually did? 32. Hickson did not want to humiliate anyone, but he was also fiercely committed to protecting his wife. With polite Southern collegiality, he calmly pointed out the 60 opportunities when staffers could have provided safer care but didn’t. Some staffers were immediately embarrassed. Several wondered if he was kidding, got defensive and offered explanations for their lapses.

Hickson reported his findings to Dr. Tom Talbot, VUMC’s chief epidemiologist, and Talbot ran with it, spearheading an ambitious clean hands initiative that was launched in July 2009. Since then, hand-washing rates at Vanderbilt have jumped from 58 percent to 97 percent; at the same time, the number of several stubborn infections has dropped, one of them by as much as 80 percent. “We get into bad habits, all of us do, and sometimes we need somebody to remind us to get back on the right pathway,” says Hickson. “That’s the key to transforming health care.”

Talbot orchestrated a number of practical changes right away, including installing additional hand sanitizer dispensers at the entrance and exit of every patient’s room or bay and within easy reach inside. Staffers were instructed to clean their hands before and after every encounter with patients, even if all they planned to do was have a conversation. Even the smallest details were addressed. Clinicians who complained that their skin had become irritated by excess antiseptic gel were told to cut back to a dime-size portion, and moisturizing lotion dispensers were added throughout the hospital.

That was the easy part. Talbot knew that it would take an all-out culture shift to see dramatic improvement. A prior hand-washing program, which focused largely on education and random surveillance, had done little to boost rates. This time, Talbot drilled down on what he believed would be the keys to success: training, communication and shared accountability up and down the staff hierarchy.

Because the hospital’s top leadership would be the ultimate enforcers, Hickson and Talbot knew they needed buy-in before the program was officially launched. The old days of giving high-performing doctors a pass on unprofessional conduct — “Oh, that’s just Dr. So and So, that’s how he is” — would be over. Every hospital worker, no matter his or her rank, would be held to the same high standards. “We had to have support from leadership, so if we had pushback, we would elevate that up and they wouldn’t blink,” says Talbot. “Instead, they would say, ‘That’s not the kind of behavior we expect here.’”

Competition is a big motivator at Vanderbilt, too. Hand-washing scores for individual units and departments are tallied up from highest to lowest, and results are posted every month in break rooms and other staff areas so that everyone can see how his or her team compares with the one down the hall. “You want to look better than other services when that scorecard comes out,” says Johnson. “You don’t want to be at the bottom. That’s just human nature.”

Today, after more than 200,000 hand-washing observations, Vanderbilt’s overall hand-washing compliance rate has almost doubled. At the same time, three major types of infections linked to the insertion of tubes and catheters have been reduced considerably, according to Talbot. Urinary tract infections related to catheters in intensive care units have dropped by 33 percent; pneumonia linked to ventilators by 61 percent; and bloodstream infections associated with central lines — the tubing that delivers fluids and medications to patients — by 80 percent in ICUs.

Culture change is not about mission statements and core values written on a poster. It’s about fostering feelings within the organization from top-to-bottom that this stuff matters.

Welsh Hilton Hotel linked to 74 cases of norovirus

Posted on September 25, 2012 by Ben Chapman

When I was in high school I had a friend who worked as a maid at a motel. Not the greatest job but she needed to make money to offset schooling costs. She used to tell stories of cleaning up vomit, diarrhea and, um, other stuff. She couldn’t believe how guests treated the bathrooms – likely figuring the mess wasn’t their problem, someone would clean it up.

According to BBC, a Hilton hotel in Newport (that’s in south east Wales) has been linked to over 70 cases of norovirus and it’s not clear whether messy vomit and diarrhea incidents, or food, are to blame. The outbreak has not only hit guests, but over 20 staff members are ill.

Hilton Worldwide said the wellbeing of guests and staff was of “paramount importance” and it had brought in “stringent” health and safety measures.

Public health officials say the outbreak is not linked to a particular function or event, but the virus was passed by someone originally infected.

Newport council alerted Public Health Wales two days after the first illnesses.

These symptoms are described as “unpleasant but short-lived” and the condition is described as not serious unless a patient is already in a vulnerable group.

Control measures have been put in place at the hotel to prevent the spread of the infection.

“Investigations carried out by Newport City Council’s environmental health team indicate that the illness was consistent with a viral infection passed from person to person, most likely norovirus,” said Dr Lika Nehaul, a consultant in communicable disease control with Public Health Wales.

Having norovirus sucks. The mighty little virus gives an affected individual nasty cramps, violent vomiting and in some cases violent diarrhea. With each expulsion of bodily fluids billions of virus particles are spread throughout a bathroom. Or in some cases, throughout a public area (like a walkway or plane). Who knows what happened here but if the outbreak is linked to one initial ill individual (with single or multiple incidents) the cleaning and sanitizing of common areas may be a factor. It’s possible that improper infection control practices, and staff who are attempting to clean, spread particles throughout the hotel. Or staff became the vectors themselves.

Nightmare in the playground, ‘I saw filth and grime coupled with clumps of dirt, matted hair and rotting food’

Posted on March 6, 2012 by Ben Chapman

Last weekend we took the family to Myrtle Beach, land of golf, outlet malls and lazy rivers. After hitting a kids museum, a pizza arcade and the Ripley’s Aquarium I asked Jack, our three-year-old, where he wanted to eat dinner and he emphatically replied ‘Chick-Fil-A’ because of the playground. No wonder I dream about the place.

Being a food safety nerd, we do a bunch of handwashing after visiting the play area and before jumping into our meals. A friend of mine who runs one told me the staff also disinfect the whole room using a bunch of different sanitizers every night. Not risk elimination, but definitely reduction.

According to USA Today, a mother of four has embarked on a national crusade to reduce illness risks associated restaurant playgrounds, including suggesting regulations on sanitation.

Arizona’s most populous county is looking at new regulations to safeguard restaurant play areas after one mother here discovered unsanitary conditions when her 3-year-old wanted to play at a nearby McDonald’s.Maricopa County health officials are looking at expanding their oversight of restaurant cleanliness to playgrounds."This is a giant step in the right direction," said Erin Carr-Jordan, 37, a mother of four with a doctorate in developmental psychology who lives in this Phoenix suburb.The proposal would require sanitizing of those areas after every shift, detailed cleaning protocols, permanent signs encouraging children’s hand washing before meals and immediate closure of the play areas "when vomiting and/or fecal accidents occur."But getting those changes into law isn’t a sure thing. The approval process takes months, the county supervisor she is working with leaves office at the end of the year and a candidate for another supervisor’s seat is president of the Arizona Restaurant Association.

Carr-Jordan is getting support from the county’s public-health director, Dr. Robert England (not to be confused with Robert Englund – ben).
"It’s just common sense. You don’t want to facilitate something that’s going to make kids’ hands filthy dirty right before they handle food," England said. "But we also don’t want to do anything that discourages physical activity. For some, this is the best playground equipment available."
England said he hasn’t read the proposed health-code changes but would support "reasonable" play-equipment-cleanliness requirements.The Arizona Restaurant Association would prefer advisory, not mandatory, cleaning standards for play areas."Our restaurants do everything in their power to make sure these locations are clean," said Sherry Gillespie, the association’s government relations manager.

The mother’s outrage started about a year ago when Carr-Jordan’s son asked to go on the slide at a Tempe, Ariz., McDonald’s."I saw filth and grime coupled with clumps of dirt, matted hair and rotting food. The entire structure was riddled with swear words and gang signs," she said.
The Arizona Restaurant Association would prefer advisory, not mandatory, cleaning standards for play areas.

"Our restaurants do everything in their power to make sure these locations are clean," said Sherry Gillespie, the association’s government relations manager.

While I’m not a fan of regulation just because, Gillespie’s comments sound like ‘just trust us’ to me. Everything in their power is pretty empty, if there are cleaning and sanitizing guidelines that folks are following, tell people what they are. My Chick-Fil-A friend showed me what he does and that was good enough for me.

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