What is the Difference Between Listeria and Salmonella

The key difference between Listeria and Salmonella is that Listeria is a genus of gram-positive pathogenic bacteria while Salmonella is a genus of gram-negative pathogenic bacteria.

Food-borne illnesses are caused by bacteria, viruses, or parasites that contaminate food. The symptoms of such illnesses often include vomiting, fever, aches, and diarrhoea. Some of the microbes that cause food-borne illnesses escape from the intestine and enter the bloodstream. Therefore, these microbes can cause systematic infections in other parts of the human body. However, all food-borne illnesses ultimately result in gastroenteritis. Gastroenteritis is the inflammation of the gastrointestinal tract, including the stomach and intestine. Listeria and Salmonella are two bacterial genera capable of causing gastroenteritis.

1. Overview and Key Difference
2. What is Listeria
3. What is Salmonella
4. Similarities – Listeria and Salmonella
5. Listeria vs Salmonella in Tabular Form
6. Summary – Listeria vs Salmonella

What is Listeria?

Listeria is a genus of bacteria that acts as intracellular parasites in mammals. About 21 bacterial species have been identified and included in this genus. This genus is named in honor of British surgeon and medical scientist Joseph Lister, the pioneer of antiseptic surgery. The Listeria species are gram-positive, rod-shaped, and facultative anaerobes. They do not produce endospores.

Listeria and Salmonella - Side by Side Comparison

Figure 01: Listeria

The major human pathogen in the genus Listeria is Listeria monocytogens. This species is usually the causative agent of the relatively rare bacterial disease in humans called listeriosis. Listeriosis is an infection occurring due to eating food contaminated with Listeria monocytogens. Listeriosis can cause systematic infections in pregnant women, newborns, the elderly, and people who have weakened immunity. These systematic infections include miscarriages, septicemia, and meningitis. In others, it causes only gastroenteritis. Some virulent factors of Listeria monocytogens include hemolysins (listeriolysin O), two distinct phospholipases, a protein called ActA, and internalins. Furthermore, Listeria ivanovii is another pathogen of mammals, specifically in ruminants, and rarely causes listeriosis in humans. The treatment for listeriosis includes intravenous delivery of high-dose antibiotics such as ampicillin, penicillin, amoxicillin, and gentamicin, and hospital care.

What is Salmonella?

Salmonella is a genus of rod-shaped, gram-negative facultative anaerobes bacteria belonging to the family enterobacteriaceae. Salmonella species are non-spore-forming, motile enterobacteria with cell diameters between 0.7 to 1.5 μm and lengths from 2 to 5 μm. These species also have peritrichous flagella around the cell body. The two species of Salmonella genus include Salmonella enterica and Salmonella bongori. Salmonella enterica is further divided into six subspecies.

Figure 02: Salmonella

Salmonella species are normally intracellular pathogens. Most infections are due to the ingestion of foods that are contaminated by animal feces or human feces. Moreover, pathogenic Salmonella serotypes can be divided into two main groups as typhoidal and nontyphoidal. Nontyphoidal serotypes can be transferred from animal to human or from human to human. They only invade the gastrointestinal tract and cause salmonellosis. Sub-Saharan African nontyphoidal Salmonella species are more invasive and cause paratyphoid fever. On the other hand, typhoidal serotypes can only be transferred from human to human, causing food-borne infections such as typhoid fever and paratyphoid fever. Typhoid fever is caused by Salmonella serotypes invading the bloodstream, spreading and invading throughout the other body organs. Typhoidal serotypes also secrete endotoxins. Infections by typhoidal serotypes can lead to life-threatening hypovolemic shock, septic shock that requires intensive care, and antibiotics. Antibiotics that are used for treatment include ciprofloxacin, azithromycin, and cephalosporins.

What are the Similarities Between Listeria and Salmonella?

Listeria and Salmonella are two bacterial genera capable of causing gastroenteritis.
Bacteria of both genera are intracellular pathogens.
They are rod-shaped and facultative anaerobes.
These are non-spore-forming and motile.
They can cause systematic infections by spreading to the other parts of the body.
Infections by bacteria of both genera are treated with antibiotics.

What is the Difference Between Listeria and Salmonella?

Listeria is a genus that contains gram-positive pathogenic bacteria, while Salmonella is a genus that contains gram-negative pathogenic bacteria. Thus, this is the key difference between Listeria and Salmonella. Furthermore, the genus Listeria contains 21 bacterial species, while the genus Salmonella contains two bacterial species.

The below infographic presents the differences between Listeria and Salmonella in tabular form for side by side comparison.

Summary – Listeria vs Salmonella

Listeria and Salmonella are two bacterial genera that are capable of causing food-borne illnesses (gastroenteritis) in humans. Listeria is a genus that contains gram-positive pathogenic bacteria, while Salmonella is a genus that contains gram-negative pathogenic bacteria. So, this summarizes the difference between Listeria and Salmonella.

Reference:

1. “Questions and Answers – Listeriosis.” Centers for Disease Control and Prevention, Centers for Disease Control and Prevention.
2. Giannella, Ralph A. “Salmonella.” Medical Microbiology. 4th Edition., U.S. National Library of Medicine.