Unit 9 Flashcards
Symbiotic association
Organisms live in close nutritional relationships; required by one or both members
Non symbiotic association
Organisms whose relationship is not required for survival
Synergism
Members cooperate and share nutrients
Antagonism
One or several members are inhibited or destroyed by others
Pathogen
Microbe whose relationship with its host is parasitic and results in an infection
Non pathogenic microorganisms
Commensals or mutualists
Saprobes/saprophytes ( gets nutrients from dead remains of other organisms)
Types of pathogenic microorganisms
Primary/ True pathogens
Opportunistic pathogens
Facultative pathogens
Emerging pathogens
Primary pathogen
Capable of causing disease in healthy person with normal immune defenses
Opportunistic pathogens
Cause disease when host’s defenses are compromised or when they become established in a part of the body that is not natural to them
Facultative pathogens
organisms for which the host is only one of the niches they can exploit to reproduce.
Emerging
Newly identified
Pathogenicity
The ability to produce a disease
Virulence
Degree of pathogenicity
Virulence factors
Characteristics conferring virulence. Assist the pathogen in colonizing the host’s cells
Example: Toxins, capsule, degradative enzymes…
Infection
Multiplication of the pathogen in the host
Disease
Alteration in physiology due to infection
Direct damage is due to
Bacteria and their products
Indirect damage
Immunopathology (inflammation, complement s…)
Exagerated immune response
Chronicity of the infection
Sequence of events leading to disease
Transmission
Colonization and growth at the inoculation site
Tissue invasion/virulence factor product•
Immune response in the host
Resolution or infectious disease
Routes of transmission
Respiratory: Flugge drops
Gastrointestinal: fecal-oral
Genital : STD
Skin : wounds, puncture
Steps of pathogenesis
Transmission
Adherence
Invasiveness
Toxin production
Persisting in a new environment
Adhesion via
Adhesins
Fimbriae
Glycocalyx (capsule and slime layer)
Invasiveness def and via
Entry into host cells and tissues as a strategy for bacterial survival and multiplication
Via enzymes (to destroy the tissue) and immune response evasion (capsule to evade macrophages)
Enzymes invasion
- Collagenase and hyaluronidase
Damage connective tissue - Proteases. Destroys protein such as immunoglobulin
- Leukocidine. Pore forming protein
- Lecithinase and phospholipase (destroy the tissues)
Toxin production
Damages other cells or functional abnormalities
Exotoxins
Endotoxins
Exotoxins +ex
Secreted in a soluble form into the media
Encoded by plasmids or phages
Both gram + -
Exemple dipheteria, tetanus, botulinum toxins
Endotoxins
Lipopolysaccharide on gram -
Encoded on chromosome
Protects the bacteria
Systemic effects such as fever or hypotension
Can lead to toxic shock
Persisting in a new environment
(Not being recognized)
Encapsulation
Intracellular replication
Evasion of complement system action
Antigenic variation
Antigenic masking
Destruction of phagocytes
Proteases for igA (destroys igA)
Encapsulation definition and function
Isolation of the cell in a semi permeable membrane allowing the entrance of nutrients and gases but not the host immune cells.
Also resemblance to host tissue components
Intracellular replication permitted because of
Inhibition of phagolysosome fusion
Resistance to lysosomal enzymes
Escape form phagosome and grow in cytoplasm
Antigen masking
On their surface, foreign molecules have receptors for Fc, so antigen bind and the molecule is not recognized
Criteria for proving the causal relationship between a microorganism and specific disease according to Koch
- The microorganism must be present in every case of the disease but
absent from healthy organisms. - The suspected microorganism must be isolated and grown in a pure
culture. - The same disease must result when the isolated microorganism is
inoculated into a healthy host. - The same microorganism must be isolated again from the diseased
Limitations of Koch postulate
- some pathogens cannot be grown in pure culture outside the host (E.g.
Mycobacterium leprae) - some pathogens grow only in humans
- some pathogens produce more than one disease
- opportunistic pathogens
- polymicrobial diseases
Normal flora or microbiota
Microorganisms (bacteria and fungi) that colonize the healthy human body
Called resident microorganisms
Human microbiome
Genome of the normal microbiota
Human microbiome project
Understand the role played by resident microbial ecosystems in heath and diseases
Normal flora function
Provided metabolic functions like synthesis of vitamin B and K
Stimulates immunity
Prevents colonization from unwanted pathogens
What influences normal flora
Anatomical location
Diet
Water
Medicines
Personal hygiene
The disruption of normal flora is called
Dysbiosis
Diseases related to microbiota
Disruption of normal flora, dysbiosis
Breach of natural barriers
- in the case of immunosuppression can cause infection because grow more
- close to where the normally inhabit exemple anus vagina
- not be in natural place
Microorganisms in skin where and type
Entry : sweat glands, hair follicle, sebaceous glands
Abundant in folds (moisture and acidity)
Essentially gram + bacteria:
- staphylococcus epidermidis / aureus
- Propionibacterium acnes
- Corynebacterium
External ear
Similar to skin microbiota
Microorganisms in eyes
Similar to skin flora
Nasal communication: if infection in nose, can spread to eyes
Naso and oropharynx microorganisms
Non pathogenic Neisseria and Haemophilus,
Streptococcus viridans, bacteroids and some Clostridium in abundance
Streptococcus viridans, nonpathogenic neiserias and the
Staphylococcus epidermidis inhibit the growth of:
Streptococcus pyogenes,
Neisseria meningitidis and Staphylococcus aureus, all
disease-causing more or less severe.
Esophagus microorganisms
Oropharyngeal bacteria and yeast
Stomach microorganisms
Helicobacter pilori
Intestines microorganisms
Intestine: Enterobacteriaceae (type of negative bacilli) and
anaerobes
-Bacteroides fragilis
-Escherichia coli
-Clostridium perfringens
-Enterococcus faecalis
-Lactobacilli
Amount of microorganisms in the gastrointestinal tract
From almost 0 in the stomach to a billion per gram of intestinal content in the colon
Normal urine is…
Sterile but close to anus, that’s why infections. Caused by gastrointestinal flora: E. coli, Proteus, enterococcus faecalis
Flora of the vagina
Lactobacillus ferment glucose on vaginal cells producing lactic acid. The low pH control he growth of Candida.
- Gram positive and gram negative bacteria Staphylococcus, Enterococcus, Enterobacteria etc.)
- candida
Flora of distal portion of urethra
S. epidermidis. E. faecalis, Corynebacterium spp.
Probiotics
> Probiotics: alive microorganisms that when administered in a appropriate dosis benefits the host.
Prebiotic
non digestible ingredients (typically soluble fiber) that stimulate the growth and/or activity of the beneficial microbiota .
E.g. fructo-oligosaccharides that favor the growth of bifidobacteria.
Symbiotics
probiotics + prebiotics.
E.g. oligofructose and bifidobacteria.
How are called the microorganisms living in a healthy human being
Resident microorganisms
