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: Staphylococcus, Bacillus. Gram-negative: Escherichia, Salmonella. |
|
Oxygen Requirement |
|
Obligate Aerobes: Mycobacterium tuberculosis. Obligate Anaerobes: Clostridium tetani. Facultative Anaerobes: E. coli. Microaerophiles: Helicobacter pylori. |
|
Temperature Preference |
|
Psychrophiles: Pseudomonas. Mesophiles: E. coli, S. aureus. Thermophiles: Thermus aquaticus. Hyperthermophiles: Pyrolobus fumarii. |
|
pH Preference |
|
Acidophiles: Acidithiobacillus. Neutrophiles: E. coli. Alkaliphiles: Bacillus alcalophilus. |
|
Nutrition |
|
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, Acinetobacter baumannii, Proteus mirabilis, Haemophilus influenzae. |
Sources:
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PRACTICE QUESTION Q: Consider the following statements about Listeria: 1. Listeria monocytogenes is the primary species of Listeria responsible for human illness. A. 1 and 2 only Answer: D.
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