Bacteriology 2 Flashcards
True or False : Fungi are like bacteria, they are prokaryotic cells.
False, they are eukaryotic.
What do fungi does to absorbes nutrients?
They produce exoenzymes to obtain nutrients –> they are non-photosynthetic heterotrophs.
Do fungi needs oxygen to grow?
Yes, they grow aerobically and many are strict aerobes.
What is inside the cell membrane of the fungi?
STEROLS (ergosterol)
+ plant-like cell wall with CHITIN, glucan and mannoproteins.
What are the two categories of fungi?
- Branching hyphae multicellular molds
- Unicellular yeasts
What contains the branching hyphae multicellular molds?
- Spores (inside hyphae and fruiting bodies)
- Mycelium (filamentous mass of hyphae)
Unicellular yeasts are characterized by….
BUDDING (they are round single cell).
How does fungi reproduce?
SEXUALLY(spores)
+
ASEXUALLY (spores, budding or fragmentation)
True or False. You can get rid of fungi with antimicrobial drugs.
False. Fungi are resistant to classical antimicrobial drugs.
What are the steps of the cycle of infection?
Starts with exposure to the pathogen from either animate (vectors) or inanimate (fomites) reservoir.
- Pathogen
- Reservoir
- Modes of shedding
- Mode of transmission
- Portal of entry
- Host susceptibility
Describe pathogenicity and pathogenesis.
Pathogenicity : ability of a microorganism to cause disease.
Pathogenesis : biological mechanism(s) that lead to a disease.
What are the 3 different disease carriers?
- Convalescent carrier
- Healthy carrier (subclinical)
- Incubatory carrier
What is a convalescent carrier?
Carrier that recovers but still shed the pathogen.
–> Clinical recovery, but not a bacteriological recovery. So ++ important to do bacteriological surveillance of carrier state is necessary!
What is an example of disease that will need a bacteriological surveillance?
Strangles in horses : important to detect the convalescence carrier.
What is the type of carrier state that can shed the disease, but has no clinical symptoms?
Healthy carrier (subclinical).
What the name of the carrier that is incubating the pathogen but not yet ill?
Incubatory carrier (shedding of pathogen during incubation period).
Describe virulence and virulence factors.
Virulence : measurement of pathogenicity (capacity to damage the host).
Virulence factors : bacterial characteristics that contribute to virulence.
What are the two types of virulence factors?
Physical structures (e.g. capsule, flagella) Chemical substances (e.g. toxins, adhesins).
What are the pathogenicity islands and how do they transfer their genes?
Islands carry genes for one or more virulence factors (they can be on bacterial chromosome or plasmids)
Transferred through HORIZONTAL gene transfer.
What are the 3 types of horizontal gene transfer? And which one involves a bacteriophage (the virus form of bacteria)?
- Bacterial transformation
- Bacterial transduction (involves a bacteriophage)
- Bacterial conjugaison
What is the regulatory mechanism of Quorum sensing? Explain the steps of how it works.
Some gene expression will start presenting at a certain fluctuation in cell population density.
- At low density, the cells starts multiplying and produce autoinducers.
- At high density (a certain density), the autoinducers binds to the receptor for those on the bacteria = promote group behavior (help microbial community).
Give few examples of group behavior in bacterias.
- Symbiosis
- Virulence
- Competence
- Conjugaison
- Antibiotic production
- Motility (flagellum)
- Sporulation
- Biofilm formation
Why is quorum sensing important?
Because the bacteria want to stay low (hide) until they get to a good density to develop their virulence factors.
True or false. Molecular strategies used by bacteria to interact with the host can be unique and always change between different species.
False. They can be unique, but they can be conserved across several different species.
What are the two mechanisms bacterial (virulence factors)?
- Penetration or evasion of host defenses
- Damage to host cells.
What are the different on/around cell adherence and colonization factor? (3)
- Flagella
- Pili/Fimbriae
- Capsule
Does Flagella have a big role in adherence?
No, mainly just to get into the host.
What is the capsule made of and what is capsule used for?
Made of : glycocalyx, layer of exopolysaccharides
Function : protection from phagocytosis (inhibition of opsonization) and from antibiotics.
What is called the ability of the pathogen to spread to other locations in the host?
INVASION
What are the 2 types of invasion?
- Extracellular invasion
- Intracellular invasion
How do bacteria achieve extracellular invasion?
Break down the barriers of a tissue to disseminate in the host while staying outside of the cell –> produce extracelllular enzymes.
How do bacteria achieve intracellular invasion?
Bacteria penetrate the cells and survive within this environment:
- Facultative intracellular
- Obligate intracellular
What are exotoxins? And what are delivery mode?
Usually proteinaceous toxins.
Delivery mode :
- Secretion into surrounding milieu
- Direct injection into host cells cytoplasm
What are the 3 major classes of extoxins and their effect on the body?
Type I Exotoxin : cell-surface active = disturbance of cell metabolism (e.g. clostridium perfringens)
Type II Exotoxin : membrane-damaging (e.g. staphylococcus aureus)
Type III Exotoxin : Intracellular (e.g. clostridium botulinum)
What is an example of proteolytic toxins?
Botulinum toxin
Tetanus toxin
What are endotoxins?
They are toxic components of the prokaryotic cell wall that are not released until cell death and lysis of bacteria.
What is the effect of endotoxins on the body?
Fever, diarrhea, weakness, blood coagulation, septic shock and death.
What are the 2 types of characteristics of endotoxins?
Lipopolysaccharide (LPS) :
- heat stable
- lipid A acts as endotoxin
- mediator of septic shock
- only in gram - bacteria
(Lipo) Teichoic acid :
- mediator of septic shock
- only in Gram + bacteria
What are the difference in the gene location with exotoxin and endotoxin?
Exo : usually on plasmids
Endo : usually on bacterial chromosome
What is more toxic? Endotoxin and exotoxin?
Exotoxin have a higher toxicity than endotoxin.
Between endotoxin and exotoxin, which one has a high antigenicity?
Exotoxin.
Which toxine is have heat stability?
Endotoxin.
True or false. There is a vaccine for endotoxin and exotoxin.
False. There’s only vaccin available for exotoxin (called toxoids).
What is the biofilm and what does it produce?
Mass of bacteria cling to surfaces
Produce extracellular polymer matrix and exchange nutrients
What is the function of a biofilm?
- Bacterial persistence (endocarditis)
- Reduction of host immunity
- Local damage (e.g. catheter)
- Reduced susceptibility to antibiotics
Does bacteria need iron sometimes? If yes, where do they take it?
YES, bacteria need iron for their growth and will take it from the vertebrate tissue.
How does bacteria gets the iron from the vertebrate tissue?
- Bacterial cytotoxins damage host cells = that damage will release ferritin, hemoglobin, lactoferrin.
- Receptor-mediated recognition (specific mechanism is FYI)
What can the non-pathogenic and pathogenic bacteria can do in the gut?
Non-pathogenic : maintain gut homeostasis
Pathogenic : invasive pathogen open the way into the cell for non-invasive pathogen that would not have got in without them.
