Shigella Blog

Bad Bug Book - Foodborne Pathogenic Microorganisms and Natural Toxins - Second Edition - Shigella species

marler@marlerclark.com (Shigella Attorney) — Sat, 07 Apr 2012 21:55:52 -0800

Bad Bug Book - Foodborne Pathogenic Microorganisms and Natural Toxins - Second Edition

1. Organism

Shigella are Gram-negative, non-motile, non- sporeforming, rod-shaped bacteria. Shigella species, which include Shigella sonnei, S. boydii, S. flexneri, and

S. dysenteriae, are highly infectious agents. Some strains produce enterotoxins and Shiga toxin. The latter is very similar to the toxins produced by E. coli O157:H7.

Humans are the only host of Shigella, but it has also been isolated from higher primates. The organism is frequently found in water polluted with human feces.

In terms of survival, shigellae are very sensitive to environmental conditions and die rapidly. They are heat sensitive and do not survive pasteurization and cooking temperatures. In terms of growth, shigellae are not particularly fastidious in their requirements and, in most cases, the organisms are routinely cultivated in the laboratory, on artificial media. However, as noted in subsequent sections, the relative difficulty of cultivating this organism is dependent, in part, on the amount of time within which stool or food samples are collected and processed.

Shigella species are tolerant to low pH and are able to transit the harsh environment of the stomach. These pathogens are able to survive and, in some cases, grow in foods with low pH, such as some fruits and vegetables. They are able to survive on produce commodities packaged under vacuum or modified atmosphere and can also survive in water, with a slight decrease in numbers.

2. Disease

The illness caused by Shigella is shigellosis (also called bacillary dysentery), in which diarrhea may range from watery stool to severe, life-threatening dysentery. All Shigella spp. can cause acute, bloody diarrhea. Shigella spp. can spread rapidly through a population, particularly in crowded and unsanitary conditions.

S. dysenteriae type 1 causes the most severe disease and is the only serotype that produces the Shiga toxin, which may be partially responsible for cases in which hemolytic uremic syndrome (HUS) develops. S. sonnei produces the mildest form of shigellosis; usually watery diarrhea.

S. flexneri and S. boydii infections can be either mild or severe. In developed countries, S. sonnei is the Shigella species most often isolated, whereas S. flexneri predominates in developing countries.

• Mortality: In otherwise healthy people, the disease usually is self-limiting, although some strains are associated with fatality rates as high as 10-15%. (See Illness / complications section, below.)

• Infective dose: As few as 10 to 200 cells can cause disease, depending on the age and condition of the host.

• Onset: Eight to 50 hours.

• Illness / complications: In otherwise healthy people, the disease usually consists of self- limiting diarrhea (often bloody), fever, and stomach cramps. Severe cases, which tend to occur primarily in immunocompromised or elderly people and young children, are associated with mucosal ulceration, rectal bleeding, and potentially drastic dehydration. Potential sequelae of shigellosis include reactive arthritis and hemolytic uremic syndrome.

• Symptoms: May include abdominal pain; cramps; diarrhea; fever; vomiting; blood, pus, or mucus in stools; tenesmus (straining during bowel movements).

• Duration: Uncomplicated cases usually resolve in 5 to 7 days. Most of the time, the illness is self-limiting. In some circumstances, antibiotics are given; usually trimethoprim-sulfamethoxazole, ceftriaxone, or ciprofloxacin.

• Route of entry: The fecal-oral route is the primary means of human-to-human transmission of Shigella. With regard to foods, contamination is often due to an infected food handler with poor personal hygiene.

• Pathway: The disease is caused when Shigella cells attach to, and penetrate, colonic epithelial cells of the intestinal mucosa. After invasion, they multiply intracellularly and spread to contiguous epithelial cells, resulting in tissue destruction. As noted, some strains produce enterotoxin and Shiga toxin similar to those produced by E. coli O157:H7.

3. Frequency

A recent Centers for Disease Control and Prevention (CDC) report on foodborne illnesses acquired annually in the United States revealed that about 15,000 laboratory-confirmed isolates are reported each year, with estimates of actual occurrence ranging from 24,511 to 374,789 cases (average of 131,243). About 31% of these are estimated to be foodborne. Estimates of foodborne illness episodes (mean) caused by 31 pathogens placed Shigella as the sixth most frequent cause (after norovirus, Salmonella species, Clostridium perfringens, Campylobacter, and Staphylococcus aureus, in that order).

Episodes of shigellosis appear to follow seasonal variations. In developed countries, the highest incidences generally occur during the warmer months of the year.

4. Sources

Most cases of shigellosis are caused by ingestion of fecally contaminated food or water. In the case of food, the major factor for contamination often is poor personal hygiene among food handlers. From infected carriers, this pathogen can spread by several routes, including food, fingers, feces, flies, and fomites.

Shigella is commonly transmitted by foods consumed raw; for example, lettuce, or as non- processed ingredients, such as those in a five-layer bean dip. Salads (potato, tuna, shrimp, macaroni, and chicken), milk and dairy products, and poultry also are among the foods that have been associated with shigellosis.

5. Diagnosis

Diagnosis is by serological or molecular identification of cultures isolated from stool. Shigella may be more difficult to cultivate if stool samples are not processed within a few hours.

6. Target Populations

All people are susceptible to shigellosis, to some degree, but children 1 to 4 years old, the elderly, and the immunocompromised are most at risk. Shigellosis is very common among people with AIDS and AIDS-related complex.

7. Food Analysis

Shigellae remain a challenge to isolate from foods. A molecular-based method (PCR) that targets a multi-copy virulence gene has been developed and implemented by FDA. Improvements in the bacterial isolation method continue and should be available in the near future.

The window for collecting and processing Shigella from foods, for cultivation, may be days (rather than hours, as is the case with stool), depending on the food matrix and storage conditions; e.g., temperature. Shigella species can be outgrown by the resident bacterial populations found in foods, which may reflect the usual low numbers of the organism present in foods and, in some foods, a very large number of non-Shigella bacteria. Another factor that reduces the chance of isolating Shigella from foods may be the physiological state of the pathogen at the time of analysis. Environmental conditions could affect its ability to either grow or survive in any food matrix.

8. Examples of Outbreaks

The CDC’s Morbidity and Mortality Weekly Reports provide information about Shigella outbreaks.

9. Other Resources

• Loci index for genome Shigella spp.

• GenBank Taxonomy database

• More information about Shigella and shigellosis can be found on the CDC website.

St. Lucie Florida Hit with Shigella

marler@marlerclark.com (Shigella Attorney) — Thu, 29 Mar 2012 23:59:09 -0800

Cases of people contracting a bacterial infection that causes diarrhea, fever and nausea are on the rise, according to St. Lucie County Health Department officials.

County health officials said lab tests have confirmed the infection, known as shigella, has infected 24 people since January. In all of 2011, there were 11 lab-confirmed cases in St. Lucie.

Escambia County Florida warns of Shigella cases at child care centers

marler@marlerclark.com (Shigella Attorney) — Wed, 29 Feb 2012 05:24:25 -0800

According to press reports, the Escambia County Health Department has reminded the public that people can reduce the spread of gastrointestinal illnesses by practicing simple hygiene. "We like to be proactive about this, and we've started seeing cases of Shigella, or shigellosis, which is a bacterial illness that can produce nausea, vomiting, diarrhea and sometimes fever in young people," said Dr. John Lanza, director of the Escambia County Health Department.

Lanza said the county usually sees three to 30 cases of Shigella a month, and this month there have been about 12 to 15 cases.

"We're seeing this in child-care centers, and that's where our most-vulnerable population center is — our children — and we just want child-care providers and parents to know what to look for," Lanza said.

He said simple hygiene practices can keep gastrointestinal illnesses like Shigella at bay.

"The No. 1 way of transmitting these kind of diseases is by not washing your hands with soap and water," Lanza said. He said it's important to thoroughly wash hands after using the bathroom, changing diapers and handling food.

Lanza had another health message: If you or your child has a gastrointestinal illness, stay home instead of spreading the germs.

"If you as an adult, or your child, are sick, for at least 48 hours, stay at home. Don't go to work," he said.

Preventing the spread of shigellosis

marler@marlerclark.com (Shigella Attorney) — Mon, 27 Feb 2012 15:31:59 -0800

After a person has recovered from shigellosis, Shigella bacteria remain active for a week or two. It is even possible for a person to be infected with Shigella without exhibiting symptoms. Individuals who exhibit no symptoms are known as asymptomatic, but can pass the illness on to others.

Small children acquire Shigella at the highest rate.

Prevent the spread of Shigella from an infected person to others with frequent and careful handwashing with soap.

If a child in diapers has shigellosis, everyone who changes the child’s diapers should be sure the diapers are disposed of properly in a closed-lid garbage can, and should wash his or her hands and the child’s hands carefully with soap and warm water immediately after changing the diapers. After use, the diaper changing area should be wiped down with a disinfectant such as diluted household bleach or bactericidal wipes. When possible, young children with a Shigella infection who are still in diapers should not be in contact with uninfected children.

Basic food safety precautions and disinfection of drinking water prevents outbreaks of shigellosis from food and water. However, people with shigellosis should not prepare food or drinks for others until they have been shown to no longer be carrying Shigella bacteria, or if they have had no diarrhea for at least 2 days.

At swimming beaches, having enough bathrooms and handwashing stations with soap near the swimming area helps keep the water from becoming contaminated. Daycare centers should not provide water play areas.

When traveling in developing countries, only treated or boiled water, and eat only cooked hot foods or fruits you peel yourself.

Two Maplewood Elementary students from Ocala, Florida infected by Shigella

marler@marlerclark.com (Shigella Attorney) — Fri, 24 Feb 2012 10:12:03 -0800

According to press reports, two Maplewood Elementary School children have been infected with shigellosis, the illness caused by Shigella infection. The Marion County Health Department contacted Maplewood officials on Wednesday, informing them that two students had contracted the illness; the school district launched an immediate review and response.

School district spokesman Kevin Christian said the bacteria were not found at the school. But since both cases involved Maplewood students, officials decided to clean the school for the safety of the students. It sent a team of custodians to scrub the school and cafeteria just in case the bacteria originated there.

Christian said the illness is more common in the day-care setting.

The school district also sent an Alert Now message and a letter to Maplewood parents.

Superintendent of Schools Jim Yancey said the district does not know who the children are since, by law, the Health Department could not disclose those names.

Yancey said the district response was phenomenal. He said he was worried because of the profoundly disabled young students at the school. He wanted to make sure the bacteria, if any, was eliminated quickly.

"It sounds like they did a good job," said School Board Chairwoman Judi Zanetti.

Yancey said health officials say only 14,000 shigellosis cases are reported annually in the United States.

The reality is that raw milk is far more likely to make you ill than pasteurized milk

marler@marlerclark.com (Shigella Attorney) — Wed, 22 Feb 2012 05:33:18 -0800

A new study published in the Centers for Disease Control and Prevention’s (CDC) journal, Emerging Infectious Diseases, found that the rate of outbreaks caused by unpasteurized milk (raw milk) and unpasteurized milk products was 150 times greater than outbreaks linked to pasteurized milk. In addition, the study revealed that states where raw milk sales are legal had more than twice the rate of outbreaks as states where it was illegal.

The 13-year study, involved a review of dairy product outbreaks from 1993 to 2006 in all 50 states. The authors compared the amount of milk produced in the United States during the study period (about 2.7 trillion pounds) to the amount that CDC estimates was likely consumed raw (1 percent or 27 billion pounds) to determine the 150 times higher rate for outbreaks caused by raw milk products. Raw milk products include cheese and yogurt.

The study included 121 dairy–related disease outbreaks, which caused 4,413 illnesses, 239 hospitalizations and three deaths. In 60 percent of the outbreaks (73 outbreaks) state health officials determined raw milk products were the cause. Nearly all of the hospitalizations (200 of 239) were in those sickened in the raw milk outbreaks. These dairy-related outbreaks occurred in 30 states, and 75 percent (55 outbreaks) of the raw milk outbreaks occurred in the 21 states where it was legal to sell raw milk products at the time. The study also reported that seven states changed their laws during the study period.

For a consumer, it is impossible to tell if raw milk is safe to drink by simply looking at, smelling, or tasting it. Even under ideal conditions of cleanliness, the process of collecting milk introduces some bacteria. Unless the milk is pasteurized, these bacteria can multiply and grow in the milk and cause illness in those who consume it. Pasteurization involves heating milk to kill disease-causing bacteria.

“This study shows an association between state laws and the number of outbreaks and illnesses from raw milk products,” said Robert Tauxe, M.D., M.P.H., deputy director of CDC’s Division of Foodborne, Waterborne and Environmental Diseases (DFWED). “Restricting the sale of raw milk products is likely to reduce the number of outbreaks and can help keep people healthier. The states that allow sale of raw milk will probably continue to see outbreaks in the future.”

The study also found that the raw milk product outbreaks led to much more severe illnesses, and disproportionately affected people under age 20. In the raw milk outbreaks with known age breakdowns, 60 percent of patients were younger than age 20, compared to 23 percent in outbreaks from pasteurized products. Because of their underdeveloped immune systems, children are more likely than adults to get seriously ill from the bacteria in raw milk.

“While some people think that raw milk has more health benefits than pasteurized milk, this study shows that raw milk has great risks, especially for children, who experience more severe illnesses if they get sick,” said study co-author Barbara Mahon, M.D., M.P.H., deputy chief of CDC’s DFWED Enteric Diseases Epidemiology Branch. “Parents who have lived through the experience of watching their child fight for their life after drinking raw milk now say that it’s just not worth the risk.”

Additional information on evidence-based scientific studies covering the benefits and risks of raw milk consumption can be found HERE (pdf).

Sources of Shigella

marler@marlerclark.com (Shigella Attorney) — Thu, 16 Feb 2012 16:00:49 -0800

Shigella bacteria cause human illness when they are ingested, and can lead to Shigella infection, or shigellosis, through various modes of transmission, including through food and water sources, animal-to-human contact, and person-to-person contact in daycares and other settings.

Improper sanitation and cross-contamination can be contributing factors to Shigella outbreaks associated with restaurant food.

The introduction of pasteurization greatly reduced the number of foodborne illness outbreaks associated with milk and other dairy sources, but the consumption of raw milk and unpasteurized cheeses remains a risk factor for Shigella infection. Shigella and other pathogens are shed in the feces of livestock such as cows and goats and can contaminate milk during the milking process.

Fresh fruits and vegetables can become contaminated before or after harvest. Water intended for recreation (e.g., pools, shallow lakes) and for human consumption can also become contaminated. When lakes become contaminated it may be several weeks or months before water quality conditions to improve or return to normal. Proper chlorination kills Shigella bacteria in pools and municipal water systems.

Person-to-person transmission of Shigella occurs through a fecal-oral route, and is particularly common among infants and young children due to their unrefined hygienic practices. Person-to-person transmission of Shigella has also been known to occur between infected individuals and their caregivers, and between infected food handlers and people who consume the food they prepare.

Louisville-area Shigella illnesses continue to increase

marler@marlerclark.com (Shigella Attorney) — Tue, 31 Jan 2012 06:57:46 -0800

Shigellosis cases continue to rise in Louisville, with 18 laboratory-confirmed cases last week.

That’s the highest number in any week so far during the current outbreak, which has seen 84 confirmed cases in 13 weeks.

Shigellosis is a highly-contagious diarrhea illness caused by Shigella bacteria. Symptoms include watery or loose stools for several days, and in severe cases abrupt onset of fever, nausea, abdominal cramping and vomiting.

For the past five years, Louisville has had an average of 62 confirmed cases annually.

To prevent the illness, health officials are urging people to wash their hands carefully with soap and water, including under the fingernails. This is especially important after handling items such as diapers, after each bowel movement, after helping children use the toilet and before preparing or eating food, health officials said.

Cleveland-area schools see increase in Shigella illnesses

marler@marlerclark.com (Shigella Attorney) — Fri, 27 Jan 2012 05:09:17 -0800

Twenty-one cases of Shigella had been confirmed in eastern Cuyahoga County and western Lake County as of Jan. 20, and more cases were reported this week, according to officials of the Cuyahoga County Board of Health. Some cases have occurred in the Orthodox Jewish community.

"The Academy's health professional saw a handful of cases," Rabbi Simcha Dessler, dean of Hebrew Academy of Cleveland, said Jan. 23. "As with any health-related issues, we immediately contacted the Cuyahoga County Department of Health and continued to follow their lead. A letter and fact sheet with comprehensive information and prevention strategies were sent out to the parent body."

Amy Anter, program manager in epidemiology at the Cuyahoga County Board of Health, said the board had been in touch with Mendel Singer, Ph.D., associate professor at Case Western Reserve University School of Medicine, director of Jewish Community Health Initiative, and CJN blogger, to help convey information about the illness.

"Shigella does pop up in the Orthodox community from time to time," Singer said. "When there are lots of kids in diapers and not fully toilet-trained, there are opportunities for the illness to spread. It's extremely contagious, and it takes very little of it to cause infection.

"Hand washing with warm water and soap is the best defense," Singer said. Within the Orthodox community, soap (that requires lathering) and pre-moistened wipes (that often require tearing) become an issue on Shabbat. He recommends liquid soap as a substitute for bar soap and advises keeping soap available where ritual hand washing is taking place. If pre-moistened wipes aren't used when diaper changing, cleaning with "Shabbat-friendly" wipes is needed, he said.

Jefferson County, Kentucky schools bitten by the Shigella bug

marler@marlerclark.com (Shigella Attorney) — Fri, 13 Jan 2012 09:53:04 -0800

WDRB reports that Jefferson County Kentucky schools are currently seeing a significant increase in Shigella illnesses:

In the last few months health officials say they've noticed the increase in Shigellosis.

A letter went out to all schools on Wednesday from the health department and will soon alert parents of the outbreak in Louisville.

On November 30th, a notice from Louisville Metro Public Health & Wellness said the health department had received reports of Shigellosis, a diarrhea illness caused by Shigella bacteria, which is highly contagious.

"Unfortunately, this is something that is transmitted fecally orally. So, since kids aren't paying as much attention to hygiene sometimes, or parents who are taking care of kids who have a diarrhea illness, that can be a challenge," says Dr. Paul Schulz, Medical Director of Infection Prevention with Norton Healthcare.

Fast-forward to this week and now a JCPS spokesperson says the health department has asked all schools to send out a notice to students about an outbreak of Shigellosis in Jefferson County.

JCPS spokesperson, Lauren Roberts, says they are sending the letters out because they've been asked to, and not as a result of any particular case in the school.

The health department has averaged 62 cases a year of the illnesses for the last five years.

However, in the last 3 months, they say they've already seen 60 cases.

"Technically we would call this an epidemic and try to do things to reduce that spread, like putting out these kinds of notices so that parents, teachers and other folks in the community are more aware," says Dr. Paul Schulz.

The symptoms include blood in stools, fever, nausea, abdominal cramping and vomiting.

One of the ways they say you can prevent the spread of the disease is to wash your hands carefully, and often. They say it's especially important to wash your hands after changing diapers, using the restroom, after helping a child use the restroom, or before preparing or eating food.

Dr. Paul Schulz, with Norton Healthcare, also recommends not going to school or work if you have the illness to avoid spreading it to other people.

Going to the doctor is at the top of the list.

"Even if you don't feel like you're that ill, getting evaluated and diagnosed and treated can be a good thing for you and the community," says Dr. Paul Schulz.

There are antibiotics that doctors can prescribe to help you treat this illness.

The Health Department wants everyone to be aware, and take precautions.