Batteri e loro Classificazione

Professor and Topic

• Professor: Maria Luisa Savo Sardaro
• Topic: Gram-negative pathogens 2

Gram-Negative Pathogens: Enteric Bacteria

• Gram-negative bacteria are categorized by their characteristics, such as the presence or absence of a cell wall.
• Phylum, group and genus of bacteria are presented with different classification methods.
• Some gram-negative bacteria are shown to be important pathogens, while others are not.

Yersinia

• Family: Enterobacteriaceae
• Genus: Yersinia
• Species: 11 species are discussed.
• Pathogenic serotypes are found in specific species of the Yersinia genus.
• Y.pestis, Y.pseudotubercolosis and Y.enterocolitica are examples of species causing different diseases, such as the bubonic plague.

Classification

• The pathogens are divided into 30 subgroups based on biochemical activity and antigen.
• Important pathogenic biotypes belong to biovariants 1A, 1B, 2, 3, 4, and 5 of serotype 0:3.
• Biovariant 1 is often found in water and environmental samples.

Habitat

• Yersinia is ubiquitous in different environments.
• It is found in water, the intestines of warm-blooded animals, including pigs (tonsils, intestines).
• It can withstand cold temperatures and is present in environmental isolates like lakes, ponds, and even food like ice cream.

Growth Conditions

• The minimum growth temperature is -1.3 °C.
• The optimum range is 25-37 °C.
• The maximum temperature is 42°C.
• Optimum pH range is 7.2.
• The maximum pH is 9.6
• Yersinia is a psychrotrophic pathogen, meaning it can grow at low temperatures.

Pathogenicity

• Not all serotypes are pathogenic.
• Pathogenicity is linked to adherence, invasion of intestinal epithelial cells, bacterial proliferation, and interaction with the host's immune system.
• Enterotoxin is another factor in the pathogenicity of Yersinia species, but its exact role in the disease may not be fully understood.

Diseases

• Yersinia causes gastroenteritis or symptoms similar to appendicitis.
• Incubation period varies from 1 to 11 days, with typical symptoms lasting 5 to 14 days. The illness can occasionally last for months.
• Common symptoms include abdominal pain, diarrhoea, fever, nausea, vomiting, and headache.

Food Transmission

• Infection occurs through ingestion of contaminated food, particularly pork products.
• Exposure to infected animals during processing can cause food contamination.
• Raw milk and dairy products are also potential sources of infection.
• Cooked food is a safer source of consuming Yersinia.

Prevention

• Avoiding raw or undercooked meat is crucial to prevent infection.
• Thorough cooking, pasteurisation are vital methods to destroy the bacteria.
• Proper food hygiene practices and sanitary procedures are essential during food processing and preparation, especially for contaminated meats and dairy products

Escherichia Coli

• E. coli is another gram-negative bacterium, and some strains are pathogenic.
• The specific details regarding the different types of E. coli and the possible effects are discussed in further sections of the study material.

E. coli Enteropathogenic (EPEC)

• The earliest type of pathogenic E.coli discovered.
• Pathogenic properties related to adhesion factors.
• The infecting agent damages the intestinal villi tissue.
• Common in infants, causing diarrhoea.

E. coli Enteroinvasive (EIEC)

• Similar properties and pathogenic characteristics to Shigella.
• Enters and damages the colon lining
• Associated with fever and bloody diarrhoea.

E. coli Enterotoxigenic (ETEC)

• Associated with traveller's diarrhoea.
• Produces toxins which alter the electrolyte balance, resulting in diarrhoea
• Symptoms are primarily diarrhoea, lasting for a brief period.

E. coli Enterohaemorrhagic (EHEC)

• Produces shiga-like toxins.
• Related to severe illness and is associated with bloody diarrhoea.
• Contaminated food sources need careful consideration
• Related to a form of food posioning.

E. coli Enterobacter Sakazakii

• A pathogenic E. coli strain causing serious illness.
• Mainly affecting newborn babies.
• Can cause chronic illness.
• Related to contaminated food products like powdered milk.

Growth Characteristics

• Minimum temperature for growth is around 5°C.
• Maximum temperature for growth is 45°C.
• Yersinia has a remarkable ability to resist drying and survive harsh conditions.