About the Listeria outbreaks in the US and Canada UPSC

LISTERIA

Source: IndianExpress

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Context

Two significant Listeria outbreaks have been reported in the United States and Canada, resulting in four deaths and several hospitalizations.

Details

What is Listeria?

Listeria monocytogenesis a type of bacterium commonly found in soil, water, vegetation, sewage, and feces of animals and humans.
It can contaminate various foods and lead to an infection called listeriosis.

Pathogenesis and Transmission

Listeria monocytogenes can survive and multiply at low temperatures, making refrigerated foods a common source of infection.
The bacterium can contaminate various foods, including dairy products, raw vegetables, meats, and seafood.
Once ingested, it can cross the intestinal barrier, enter the bloodstream, and infect other tissues, including the central nervous system and the placenta in pregnant women.

Symptoms of Listeriosis

Symptoms can appear up to two months after ingesting contaminated food, making it challenging to link the infection to a specific food source. They include:
Vomiting
Nausea
Cramps
Severe headache
Constipation
Fever
High-risk groups such as immunocompromised individuals, pregnant women, newborns, and the elderly are particularly vulnerable.
In pregnant women, listeriosis can cause pregnancy loss, premature birth, or severe infection in newborns.

Treatment

Treatment varies based on the infection's severity. Mild cases, presenting as gastrointestinal symptoms, may require antibiotics similar to those for routine stomach infections.
Invasive listeriosis, where the infection spreads beyond the intestines, manifests severe symptoms two weeks after consuming contaminated food and requires more intensive antibiotic treatment.

About Bacteria

*Aspect*	*Description*	*Examples*
Morphology	Bacteria come in various shapes, such as cocci (spherical), bacilli (rod-shaped), spirilla (spiral), and vibrios (comma-shaped).	Staphylococcus aureus (cocci), Escherichia coli (bacilli), Spirillum volutans (spirilla)
Gram Stain Reaction	Gram-positive: Thick peptidoglycan layer, retains crystal violet dye. Gram-negative: Thin peptidoglycan layer, outer membrane, does not retain crystal violet dye.	Gram-positive: Staphylococcus, Bacillus. Gram-negative: Escherichia, Salmonella.
Oxygen Requirement	Obligate Aerobes: Require oxygen. Obligate Anaerobes: Cannot tolerate oxygen. Facultative Anaerobes: Can grow with or without oxygen. Microaerophiles: Require low oxygen levels. Aerotolerant Anaerobes: Do not use oxygen but tolerate its presence.	Obligate Aerobes: Mycobacterium tuberculosis. Obligate Anaerobes: Clostridium tetani. Facultative Anaerobes: E. coli. Microaerophiles: Helicobacter pylori.
Temperature Preference	Psychrophiles: Grow best at low temperatures (-5°C to 20°C). Mesophiles: Grow best at moderate temperatures (20°C to 45°C). Thermophiles: Grow best at high temperatures (45°C to 80°C). ·Hyperthermophiles: Grow at extremely high temperatures (80°C to 122°C).	Psychrophiles: Pseudomonas. Mesophiles: E. coli, S. aureus. Thermophiles: Thermus aquaticus. Hyperthermophiles: Pyrolobus fumarii.
pH Preference	Acidophiles: Prefer acidic environments (pH 1-5). Neutrophiles: Prefer neutral pH environments (pH 6-8). Alkaliphiles: Prefer basic environments (pH 9-11).	Acidophiles: Acidithiobacillus. Neutrophiles: E. coli. Alkaliphiles: Bacillus alcalophilus.
Nutrition	Autotrophs: Produce their own food. Heterotrophs: Obtain food from organic matter. Phototrophs: Use light as energy source. Chemotrophs: Use chemicals as energy source. Lithotrophs: Use inorganic compounds as electron donors. Organotrophs: Use organic compounds as electron donors.	Autotrophs: Cyanobacteria. Heterotrophs: E. coli. Phototrophs: Rhodobacter. Chemotrophs: Nitrosomonas. Lithotrophs: Acidithiobacillus. Organotrophs: Streptomyces.
Pathogenicity	Bacteria can cause diseases in humans, animals, and plants. They produce toxins, invade tissues, or cause immune responses.	Pathogens: Mycobacterium tuberculosis (tuberculosis), Vibrio cholerae (cholera), Yersinia pestis (plague).
Antibiotic Resistance	Some bacteria have developed resistance to antibiotics, posing significant treatment challenges. Mechanisms include enzyme production, efflux pumps, and mutation of target sites.	Resistant bacteria: Methicillin-resistant Staphylococcus aureus (MRSA), Multi-drug resistant Mycobacterium tuberculosis (MDR-TB).
Examples of Specific Bacteria	Klebsiella pneumoniae: Causes pneumonia, UTIs, and wound infections. Acinetobacter baumannii: Causes wound and respiratory infections, resistant to many antibiotics. Proteus mirabilis: Causes UTIs and wound infections, known for its foul odor. Haemophilus influenzae: Causes respiratory and wound infections.	Klebsiella pneumoniae, Acinetobacter baumannii, Proteus mirabilis, Haemophilus influenzae.

Sources:

IndianExpress

PRACTICE QUESTION

Q: Consider the following statements about Listeria:

1. Listeria monocytogenes is the primary species of Listeria responsible for human illness.
2. Listeriosis primarily affects pregnant women, newborns, the elderly, and individuals with weakened immune systems.
3. Listeria can grow at refrigerator temperatures.
Which of the above statements is/are correct?

A. 1 and 2 only
B. 2 and 3 only
C. 1 and 3 only
D. 1, 2, and 3

Answer: D.