Plays Well With Others


Salmonella enteritidis is a parasitic organism which benefits from living inside the host, but it harms the host in the process.   As mentioned on the home page, raw eggs are very common hosts to Salmonella. 


     There are two different ways that hen eggs become infected:


Testing for Salmonella enteritidis (Image from



Making Humans RunRunning (Image from Microsoft Clip Art)

Once Salmonella strains enter the stomach via oral ingestion, they penetrate the mucosal barriers of the intestines.  Salmonella target the specialized antigen transporting membrane cells (M cells) which are located among the mucous cells.  They then enter the host tissues, bind to the cells lining the gut, begin to grow, and use the M cells for their own use.  They begin to multiply while invading the intestinal tissues and produce an enterotoxin which causes an inflammatory reaction, leading to diarrhea.  S. enteritidis is a heterotrophic organism which means that it does not produce its own food.  It gains nutrients by feeding inside of the host.



Effects on humans

Infants and elderly are at the highest risk for being affected by Salmonella as their immune systems are generally the weakest.  It is estimated that 2 to 4 million cases of salmonellosis occur in the U.S. each year.  S. enteritidis has a 3.6% mortality rate, most of these patients being elderly.   On the other hand, some individuals infected with Salmonella will only have very mild symptoms or no symptoms at all.  The only way to truly diagnose a Salmonella infection is by analyzing a stool sample for the bacteria. Below is a graph showing the number of reported cases of Salmonellosis in the United States each year.

 Reported cases of Salmonellosis in the United States (Image from




 Sick (Image from Microsoft Clip Art)Initial symptoms may persist 3-7 days and include:Sick (Image from Microsoft Clip Art)



Abdominal cramps




Chronic problems may usually occur 3-4 weeks after initial symptoms and may include:


Joint swelling



Reducing Pit StopsPit Stop (Image from Microsoft Clip Art)

Antibiotics are used to rid the infected human or animal of the bacteria.  In the past, our nation overused antibiotics.  Natural selection acts on the bacteria and kills off the majority of them when they are exposed to the antibiotic.  However, some of the bacteria are better-suited to survive.  They then reproduce, which is done very fast, especially for these prokaryotic bacteria.  As generations elapse, the population will eventually develop immunity to these drugs that were first introduced to kill the bacteria.  It is through these adaptations that these bacteria are such a growing problem to the human population.


Salmonella enteritidis (Copyright Dennis Kunkel Microscopy, Inc.) 
Copyright Dennis Kunkel Microscopy, Inc.


For example, in many large scale farming operations, cows and pigs are fed antibiotics from a very young age.  This is cheaper for the farmer in the short term as these animals appear healthier and can grow faster.  However, these bacteria develop resistance fairly quick. 

~ For MOOving information about cows, visit a  
        page by clicking on the link below:
        Domestic cow

Check out some interesting selected outbreaks