salmonella.org FAQ

A: Yes this is possible. In fact, most eggs will be Salmonella free. Some people have estimated that only 1 in 1000 eggs (or less) will be contaminated with Salmonella. however it varies by chicken, Salmonella type, and lots of other factors that we don't understand.

In general, most of the Salmonella are on the outside of the egg, but one type of Salmonella (Salmonella enterica servoar Enteritidis, aka Salmonella enteritidis) is especially good at getting inside the egg and waiting there. This is why eggs should be stored in the refigerator, it slows down the degredation of the egg and growth of the bacteria

A: Most of the work figuring out how Salmonella and similar bacteria (like E. coli) grow is very old. People tried to guess what it would be like in the intestines, where they knew that Salmonella grew, and copied that. They tested different temperatures and found that 37 celsius (98 F) works the best. This is also the temperature of our bodies! Also, they tried lots of combinations of nutrients, and found that Salmonella like to grow with a carbon (sugar) source. Glucose is the best source, just as it is for us. It is high in energy, and so the bacteria can grow quickly. Amino acids, the building blocks that make up proteins, also help the bacteria to grow, but if they are not present, they can make their own amino acids. Finally, most bacteria like a few minerals and ions to be in the media. They need these to help the proteins work and grow, and to make more DNA (the genetic material that is copied each time the cell divides). So most people add some magnesium, phosphorus and few other things.

In fact, in the laboratory, we usually use a very complex mixture that contains three things:

1. yeast extract: this is like the yeast that is used to make bread and beer, but we kill the yeast, and then the bacteria can grow on them. The yeast extract contains lots of nutrients and goodies for the bacteria to eat.
2. tryptone: this is a broken down form of casein, proteins that are found in milk. This supplies the bacteria with some amino acids that are not present in the yeast extract.
3. NaCl: this is table salt. We use this because the Salmonella like a salt rich environment (like the intestine is) but other bacteria don't like it and won't grow so well.

   If we put Salmonella in this mixture, and warm them at 98F, they divide about once every 20 minutes!

   We can also grow Salmonella in a defined media that contains magnesium, iron, and phosphorus, along with some nitrogen (we usually use ammonia because they like this) and glucose. In this case they grow a bit slower because they have to make all their own amino acids.

   Salmonella like to have oxygen, but they don't need very much of it. In fact, if there is none around, they can still grow but they do it much slower.

   Also, Salmonella don't grow very well in colder places. That is why it is important to keep things that Salmonella like to grow on (like raw chickens and eggs) in the fridge. This slows them down so that you are much more likely to kill them all when you cook the chicken.

   Good luck with your assignment.

A: The risk strictly depends upon contamination. Salmonella contamination is acquired from animal/bird/reptile/human feces, so if the tanks are not exposed to such sources of contamination, it should be OK from a Salmonella perspective. If it is exposed to such contamination, it is unsafe no matter how long is has been stored. Note that Salmonella is not the only potential bio-contaminant in water.

A: Fowl can be carriers of Salmonella. although the probability is relatively low (in fact, probably lower than the likelihood of contacting Salmonella from common food sources). Because shedding of the bacteria from an asymptomatic carrier can be sporadic, it may be difficult to detect Salmonella in the pet duck. Although this is somewhat difficult to control with a two-year old, avoiding oral ingestion of the water or feces possibly contaminated by the duck, and careful handwashing after contacting the duck will effectively decrease the potential for contacting a Salmonella infection. Nevertheless, there is no absolute guarantee.

A: First, Salmonella are a bacteria and not a virus. This is a very important distinction, because bacteria can be treated with antibiotics, but they do not work with viruses. That is why when you get a cold (usually a virus) the doctor may not give you antibiotics.

There is not a lot of work on using Salmonella to cure other diseases, although there is a report that Salmonella can be used to treat cancer. This is very preliminary work, and scientists are still studying it to find out how to make the system better and develop a potential cure. It is a long way off though.

A: First let me begin by saying that I am not a physician. If you know of someone who is ill, you should promptly see a physician.

Adults or teens can die from a Salmonella infection. Although this is rare in otherwise healthy individuals, Salmonella can be lethal for people who are immunocompromised (have a weakened immunity) due to another illness or medical treatment (e.g. due to cancer chemotherapy or due to treatments following organ transplantation). It is also possible that if a person is treated with an inappropriate antibiotic (an antibiotic that the Salmonella is resistant to but which kills other bacteria that normally live in the intestines of healthy people), the illness will be much more severe and possibly lethal.

Most healthy adults and teens infected with types of Salmonella that are common in the US will be quite sick for several days, then recover without antibiotic treatment. Many physicians and scientists believe that unless there are other factors (e.g. immunocompromised or an exceptionally long illness) that it is best to avoid antibiotic treatment.

A: When present, Salmonella is initially in the "whites" of fresh eggs. However, this environment is restricted for some nutrients that Salmonella needs so the bacteria are usually present in low numbers. As eggs age the membrane around the yolk sac begins to break down and releases nutrients that Salmonella needs to grow, so the bacteria can move toward the yolk (by a process called chemotaxis) and reproduce.

A: It is not clear that Salmonella does not affect dogs in a negative way. Most dogs do not get serious Salmonella infections, but that is probably because they do not usually get large doses of infected food/water as might occur if fed raw chicken. Furthermore, dogs can be carriers of Salmonella. so infected dogs can be a serious risk for human health. (Also note that raw chicken may lead to Campylobacter infections as well as Salmonella infections.)

There is ample epidemological evidence that dog feces may be an important source of environmental contamination, and spread of Salmonella to humans (try a search of PubMed for the keywords Salmonella AND dog). One reference directly related to inclusion of raw chicken in dogfood is:

Can Vet J 2002 Jun;43(6):441-2 Preliminary assessment of the risk of Salmonella infection in dogs fed raw chicken diets. Joffe DJ, Schlesinger DP.

Also note the following reference that mentions the incidence of disease in dogs:

Vaccine 2002 Feb 22;20(11-12):1618-23 Immunogenicity of chi4127 phoP- Salmonella enterica serovar Typhimurium in dogs. McVey DS, Chengappa MM, Mosier DE, Stone GG, Oberst RD, Sylte MJ, Gabbert NM, Kelly-Aehle SM, Curtiss R. "Salmonellae are commonly isolated from dogs. The number of dogs infected with Salmonella spp. is surprisingly high and greater than the incidence of clinical disease would suggest. Salmonellosis is common in greyhound kennels. Morbidity can approach 100% in puppies and the mortality ranges to nearly 40%."

Bleach is an effective disinfectant of the countertop, but it is essential that the area is thoroughly cleaned because the bleach may not effectively penetrate any dried residue.

A: I do not specifically know about Salmonella serotype Tennessee, however it is possible that if one serotype (Seftenberg) can be isolated from coconut products another could also.

There have been a few confirmed illnesses with Salmonella serotype Tennessee, for example (http://vm.cfsan.fda.gov/~mow/saltenn.html), therefore I suggest that you employ the services of a diagnostic laboratory that will be able to test whether your product is contaminated with Salmonella.

A: Raw eggs can contain Salmonella. The probability depends on where your eggs come from, how fresh your eggs are, and other factors. You can get lucky for quite awhile, but you are taking a chance with raw eggs. It is possible to buy pasteurized or irradiated eggs that are "Salmonella-free".

A: I am not a physician, so I am not competent to give medical advice. However, I'd make sure she is seen by a good infectious disease specialist. I know how worrisome this must be ... sorry I couldn't help.

A: If the gravy is boiled the Salmonella and other bacteria that may be in the blood will be killed. If the juices from the cooked poultry are +used, as long as the poultry is thoroughly cooked the bacteria will also be killed.

A: Bleach will effectively kill Salmonella. but it demands prolonged exposure (also true for other decontamination solutions available). Bleach is a good way to decontaminate solid surfaces, for example if some solution is spilled.

The best way to treat solutions (or contaminated petrie dishes, paper bench covers, set) is by autoclaving. After autoclaving the solutions can be poured down the sink and flasks, etc can be simply washed in an automatic dishwasher or by hand. The only caveat is that the autoclaving must be sufficiently long to fully sterilize the solutions (which depends upon the volume of the solutions).

A:You are correct. Once defrosted Salmonella can grow on the chicken and continue to grow until it is completely frozen again -- upon re-defrosting that Salmonella will begin with a larger starting population and resulting in a larger final population.

There usually isn't a problem if the chicken is marinated for a limited time in the refrigerator (kept at 4 C, not at room temperature), then cooked immediately. However, this could depend upon the marinade, the time in the refrigerator, and the number of bacteria associated with the chicken prior to use.

A: There is not a simple answer to this question because it depends upon the inoculum of microbes (they have to be present in the food or from human contamination), the composition of the food, etc. It takes time for the bacteria to reproduce in the food. The longer the food sits at room temperature the more likely there is to be a problem (overnight is way too long). In particular, when warm food slowly cools to room temperature, the bacteria can grow quite quickly at the intermediate temperatures. It is unlikely that if the food is allowed to cool sufficiently to be placed in the refrigerator (that is, it is no longer hot, but still warm) that there will be a problem. Sorry there is not a straightforward, simple answer, but I hope this helps.

A: Salmonella has been isolated from fish. It is not clear to me whether the source is via the human handlers or via the fish per se. Human outbreaks from fish seem to be rare, but I recall that several years ago there was an outbreak due to smoked eel consumption in Germany.

A: There are reports that ferrets can be infected with Salmonella. but I know of no documented cases where they have been shown to act as carriers. From reports I am aware of, ferrets seem quite sensitive to Salmonella showing gastrointestinal symptoms like those of humans. Nevertheless, it is probable that a low percentage of any susceptible animals will become carriers following an overt infection.

A: The eggs are now pasteurized before use in commercial ice cream (including componants of ice cream like cookie dough). Freezing can decrease the number of viable Salmonella. but other components like milk protein, etc can protect the Salmonella. so this is not an effective way of decontamination. The risk from raw eggs varies greatly depending upon the number of eggs used, the part of the country you are from, and other factors. There have been cases of Salmonellosis attributed to foods made with raw eggs, including key lime pie, mayonnaise, caesar salad, andlicking utensils from uncooked foods. The risk of acquiring Salmonellosis from licking a spoon may be small, but there is indeed some risk if raw (unpasteurized or unirradiated) eggs are used.

A: Although it seems trivial, that is not a easy question to answer because survival depends upon conditions like humidity, etc, and infection depends upon susceptibility and dose of the bacteria consumed. However, when surrounded by proteins from the egg, it is clear that Salmonella can survive for weeks or months. Therefore, it is a good idea to clean your counters thoroughly. Salmonella is quite sensitive to mild disinfectants, including simple things like a dilute bleach solution.

One more point ... although some eggs may contain Salmonella so this is a real food safety issue, the presence of Salmonella in eggs remains quite low in most parts of the country at most times because of careful surveillance. The biggest problem is when lots of eggs are combined, like when making an omelette for a very large group of people.

A: It is extremely unlikely that you acquired Salmonella from an aerosol from the drain. Although there are reports of Salmonella infection via aerosol, these cases all involve very high concentrations of Salmonella in a laboratory setting known to produce aerosols. (The drain pipe situation is common in many buildings with open overflow drains, often resulting from evaporation of fluid from the sewage trap. Simply pouring water down the drain is usually enough to prevent the odor, but bleach would work also.) It is more likely that you acquired the Salmonella from water or food. In particular, lettuce is often a culprit because it is easily contaminated and each leaf must be individually scrubbed to remove surface bacteria. I have spent a lot of time in in parts of the world where Salmonella is an endemic problem, and I know that it is sometimes difficult to provide completely avoid Salmonella even in the very best and cleanest establishments. I hope this helps.

A: For advice on diagnosis, we recommend that you contact your local county/state/regional public health laboratory or the CDC. You might begin by an online search for Salmonella and Pulsenet

A: Salmonella is notcompletely killed by freezing, especially when present in food. Freezing is NOT an effective way of decontamination. The Salmonella that survive freezing can grow during defrosting at elevated temperatures (above refrigerator temperature).

A: Freezing is NOT an effective way of killing Salmonella. Although Salmonella is sensitive to freezing in water, the protein in the ice cream protects the Salmonella. There have been documented cases of Salmonella infections from raw eggs in frozen ice cream. If you are dealing with the public, particularly sensitive populations like children, you should avoid uncooked eggs unless they are irradiated or "Pasteurized".

A: There is no a health reason for not defrosting. Rather, it is difficult to cook the meet thoroughly when it begins frozen. Fast food restaurants uses very thin patties to avoid this problem.

A: There is not a simple, over the counter test for Salmonella that would be useful. Most places have requirements for "coliform counts" (indicating all types of bacteria that indicate sewage/fecal contamination) to be below a certain level considered safe by public health standards for use of public lakes, etc, however this criteria will not apply to farm ponds, etc.

In fact, a microscope is not an appropriate test for Salmonella. Every environment has many bacteria that are not harmful, and many have the same size and shape as Salmonella under the microscope. Identifying Salmonella would require culturing the bacteria on special media, tests with specific antibodies, or assaying for Salmonella specific DNA -- i.e. reasonably complex unless you are trained in microbiology and have the appropriate equipment. Moreover, it is even more difficult with a lake because the bacteria may be quite dilute.