HEALTH MICROBIOLOGY

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BIO 431

HEALTH MICROBIOLOGY

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Disease formation:

Infection and the effect of toxins

• Pathogens provide access to the host tissues and the interaction of the host macromolecules and attachment to the mucosal surfaces. The pathogen begins to spread in the attachment zone and can be spread throughout the host with the circulatory system.

• Virulence is determined by the spread, toxicity, and other factors it produces. In most pathogens, several factors contribute to the virulent. Attenuation is the loss of virulence. Salmonella shows a wide variety of properties that improve virulence.

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Microorganism - Host Relations

• Anatomical, physiological and biochemical differences in different parts of the body create selective environments for microorganisms, causing different microorganism groups to settle.

• Skin: Dry conditions ↔ Staphylococcus aureus (Dehydration resistant)

• Lung: High Oxygen ↔ Mycobacterium tuberculosis (Mandatory aerob)

• Large intestine: Oxygen-Free ↔ Clostridium (Mandatory anaerobe)

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• The mucous surface area is approximately 400 m2.

• The skin surface area is approximately 400 m2

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Pathogenesis-Adhesion

• The majority of The majority of Escherichia coli Escherichia coli members are not pathogenic and members are not pathogenic and are located in the large intestine with cecum (blind intestine), the are located in the large intestine with cecum (blind intestine), the

majority of which are excreted with feces.

• Some Some Escherichia coli Escherichia coli strains produce fimbrial proteins called CFA strains produce fimbrial proteins called CFA (colonization factor antigen) and attach to the small intestinal (colonization factor antigen) and attach to the small intestinal

epithelium.

• Bacteria colonize this region and produce enterotoxins, causing Bacteria colonize this region and produce enterotoxins, causing diarrhea (= diarrhea) and some other diseases.

diarrhea (= diarrhea) and some other diseases.

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Colonization and Development

• Colonization: Proliferation of a pathogen in tissueColonization: Proliferation of a pathogen in tissue

• TemperatureTemperature

• pHpH

• OxygenOxygen

• Food sources affect colonization.Food sources affect colonization.

• Brucella abortus Brucella abortus develops very slowly in many tissues, while it develops very slowly in many tissues, while it develops very fast in the placenta: Erythrol

develops very fast in the placenta: Erythrol

• Siderophores (have affinity for iron in Transferrin and Lactoferrin)Siderophores (have affinity for iron in Transferrin and Lactoferrin)

• Aerobaktin in Aerobaktin in Escherichia coli Escherichia coli (encoded by Col V plasmid)(encoded by Col V plasmid)

• Transferrine-specific receptor proteins in NeisseriaTransferrine-specific receptor proteins in Neisseria

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Virulence Factors

• They are proteins that cause the formation or continuation of the disease and are secreted out of the cell.

• enzymes

• Hyaluronidase: Spread → Streptococci, staphylococci, some clostrides

• Protease, nuclease, lipase → Streptococci and staphylococci

• Collagenase (κ-toxin): Spread → Gas gangrene causing clostrides

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Fibrin, Clot and Virulence

• Fibrin clot is formed in the region where there is microbial invasion and the infection is tried to be limited.

• Streptococcus pyogenes → Streptokinase

• (Fibrin cover pieces, fibrinolytic)

• Staphylococcus aureus → Coagulase

• (Coagulates fibrin, protection of bacteria)

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Exotoxins

• The strongest biological toxins are exotoxins produced by microorganisms. Each exotoxin acts on specific host cells, leading to significant impairment in their function.

• They are generally examined in 3 categories:

• Cytolytic toxins: Enzymatic effect, lysis

• A-B Toxins: They are covalently bound, the B subunit binds to surface receptors and allows the A subunit to pass through the membrane

• Superantigens: Stimulates a large number of immune cells, causing excessive inflammation.

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Enterotoxins and Endotoxins

• Enterotoxins are exotoxins that act on the small intestine, alter intestinal permeability and lead to diarrhea. Many enteric bacteria colonize the small intestine and produce A – B type enterotxins.

Bacteria that cause food poisoning often produce cytotoxins or superantigens.

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Enterotoxins and Endotoxins

• Endotoxins are lipopolysaccharides derived from the outer membranes of Gram-negative Bacteria. Endotoxins are generally less toxic than exotoxins. The presence of endotoxin, which is revealed by limulus amebocyte lysate analysis, indicates that the substance is contaminated by Gram-negative Bacteria.

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Cytolytic Toxins

• Hemolysins: These are toxins that cause lysis of the cell by acting on Hemolysins: These are toxins that cause lysis of the cell by acting on the cytoplasmic membrane.

the cytoplasmic membrane.

• Phospholipase (=Lecithinase): Phospholipid acts on lecithin Phospholipase (=Lecithinase): Phospholipid acts on lecithin (phosphotidylcholine).

(phosphotidylcholine).

• ((Clostridium perfringens Clostridium perfringens → → α-α-toxin)toxin)

• Streptolizin acts on O → Sterols.Streptolizin acts on O → Sterols.

• Cytolytic Toxins Leukosidines → Affect white blood cells.Cytolytic Toxins Leukosidines → Affect white blood cells.

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Exotoxins Produced by Pathogens and Extracellular Virulence Factors

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