Flashcards in Lecture 1 - Microbiology Deck (50):
What is microbiology?
The study of microorganisms.
What are the structural components of prokaryotes?
Nucleoid containing DS circular DNA genome.
Peptidoglycan cell wall
May contain plasmids
What is the mesosome?
vesicles formed by invagination of plasma membrane, may be involved in cell wall formation and/or chromosome replication.
What are the structural components of eukaryotes?
Nucleus containing DS linear DNA.
Nucleolus - production and maturation of ribosomes.
What is the endoplasmic reticulum?
Site of translation, folding, and transport of proteins that are to become part of the cell membrane or proteins that are to be secreted.
What is the golgi apparatus?
Central delivery system for the cell, primary function is to process and sort proteins targeted to the plasma membrane.
What is the internal structure of bacterial cells?
What is the external structure of bacterial cells?
Pilli and fimbriae
What is a Gram +ve bacteria?
Turns purple - stain gets trapped
Thick multi-layered peptidoglycan wall
What is a Gram -ve bacteria?
Thin peptidoglycan wall
Inner membrane and outer membrane
Which type of bacteria form spores Gram +ve or Gram -ve?
What is a bacterial spore?
Dehydrated, multishell structure that protects bacteria.
Bacteria convert from a vegetative state to a dormant state.
Resistant to environmental factors.
What is a facultative anaerobe?
Can grow with or without presence of O2.
What is an obligate aerobe?
Requires O2 for growth.
What is an obligate anaerobe?
Cannot grow in presence of O2.
Bacterial mechanisms and byproducts of bacterial growth that cause damage to the human host.
What are virulent factors?
Adherence factors, invasion factors, capsules, endotoxin, exotoxins, siderospores.
What is opportunistic bacteria?
Cause disease only in people who have preexisting conditions.
What are local effects of bacterial pathogenesis?
Produce enzymes (exotoxin) that damage host cells and cellular components.
What are systemic effects of bacterial pathogenesis?
Septicaemia - wide spread destruction caused by absorption of bacteria or toxins from the blood.
Endotoxins (released by Gram -ve) triggers immune response, fever, septic shock, death.
Exotoxins (produced by Gram +/-) such as cytotoxins or neurotoxins.
What is septic shock?
Shutdown of body systems to preserve the most important organs.
What are the stages in the progression of bacterial infection?
Incubation period (no signs or symptoms).
Prodromal period (vague, general symptoms).
Illness (most severe symptoms).
Convalescence (no signs or symptoms).
What are fungi?
Non motile, aerobic eukaryotes (yeast).
Reproduce by forming spores (asexual reproduction).
How does fungal pathogenesis occur?
A defect in the barrier.
Fungi enter into tisue.
Multiplication of fungi.
Tissue inflammation reaction and necrosis.
What are superficial mycoses?
Occur only on the outermost layers of the skin/cuticle.
What are cutaneous mycoses (dermatophytes)?
Extend deeper into the epidermis (invasive nail diseases).
What are subcutaneous mycoses?
Infections involving the dermis, subcutaneous tissue, muscle.
Associated with traumatic injuries.
What are systemic mycoses?
Infections originating primarily in the respiratory tract.
May spread to multiple sites.
What are protozoa?
Develop into cyst to survive under harsh conditions.
What are viruses?
Rely on host for replication machinery.
Metabolically inactive outside host.
Attach to host, insert genome, hijack, replicate.
How does viral replication occur?
Early phase (recognition, attachment, penetration, release).
Late phase (genome replication, virion production).
Latent phase (extracellular infectious virus not detected).
Nonspecific early symptoms.
Caused by tissue damage and systemic effects.
Body repairs the damage.
What are prions?
Infectious agent composed entirely of protein material.
Long incubation periods, neuronal loss, failure to induce inflammatory response.
Extremely resistant to heat and chemicals.
How do prions propagate?
By transmitting their misfolded protein by inducing the normal existing protein to become misfolded and become dysfunctional - cascade effect.
Direct transmission examples?
Mucous membrane to mucous membrane.
Skin to skin.
Indirect transmission examples?
An organism able to evade the various normal
defences of the human host to cause infection.
When an organism enters the body, increases in number and causes damage to the host.
Where the host and bacteria live together with no effect on each other's life cycle.
Un-equal relationship - one organism benefits to the detriment of another; happens in all infections.
Where species live together for their mutual benefit.
Define opportunistic infection?
When the healthy human defences are weakened infection by organisms not generally able to cause infection in a healthy human.
Define nosocomial infection?
Infections transmitted in hospitals.
What is Staphylococcus aureus (golden staph)?
• Common cause of hospital/community acquired infection.
• Causes disease through the production of toxin (hyaluronidase) or through direct invasion & destruction of tissue.
• Clinical disease ranges from cellulitis, UTI, surgical wound infection to septicaemia, endocarditis, osteomyelitis, pneumonia.
• The clinical manifestations of some staphylococcal diseases are the result of toxin activity such as toxic shock & scalded skin syndrome and food poisoning.
What are predictors of Staphylococcus aureus (golden staph) carriage?
• Hospital setting
– Prolonged hospital stay (often > 14 days) – Preceding antimicrobial therapy
– Surgical procedure(s)
– Presence in ICU or burn unit
– Proximity to a known MRSA case
• Community setting
– Recent hospitalisation
– Presence of decubitus ulcer – Indwelling catheters
What may antibiotics target?
Cell wall synthesis
Nucleic acid synthesis
What 3 ways can antibiotics be produced?
Chemotherapeutic or synthetic agents (in lab).
Semi synthetic (hybrid of two).
What is selective toxicity?
Interfere with vital function of bacteria without affecting host.
High therapeutic index.
What is innate antibiotic resistance?
An intrinsic resistance based on the mechanism of action of the drug.