Microbiology Flashcards
chain of infection
1) Causative Agent - bacteria, virus, fungi (microorganism)
2) Reservoir (source) – Humans, animals and the environment can all be reservoirs for microorganisms to grow and multiply
3) Portal of Exit - the path for the microorganism to escape from the host. The blood, respiratory tract, skin and mucous membranes, GU tract and GI tract are all examples (many more exist)
4) Mode of Transmission - how microorganisms are transferred (to other organisms, locations)
5) Portal of Entry - a path for the microorganism to get into a new host, similar to the portal of exit (ie nasal passages, broken skin, eyes, GU system, GI tract and many more)
6) Susceptible Host - a person susceptible to the microorganism.
microbes
include bacteria, fungi, protozoa, microscopic algae, and viruses
prions
- proteins that are infectious
- Proteinaceous infectious particles
- Inherited and transmissible by ingestion, transplant, and surgical instruments
- Cases are rare
- Treatment is mainly supportive – no specific treatment exists for prion-related diseases
- Spongiform encephalopathies
- “Mad cow disease”
- Creutzfeldt-Jakob disease (CJD)
pathogen
a micro-organism that has the potential to cause disease
infection
the invasion and multiplication of pathogenic microbes in an individual or population
normal flora
microorganisms that live on another organism or object without causing disease
opportunistic infection
when non-pathogenic microbes take advantage of a host with a weakened immune system or disrupted flora
disease
when the infection causes damage to the individual’s vital functions or systems
causative agents
Prokaryotic (cells without a nucleus)
- Bacteria
Non-cells
- Viruses (RNA or DNA in a capsid)
- Prions (infectious proteins)
Eukaryotic (cells with a nucleus)
- Fungi
- Protozoa
- Algae
- Multicellular Animal Parasites
shapes of bacteria
Coccus (spherical) (ball)
Bacillus (rod-shaped) (hot-dog)
Spirochetes (corkscrews/wine opener) (spiral)
Vibrios (comma shaped) (hotdog with a tail)
Spirilla (spirals) (hot dog with lots of spiral tails)
ARRANGEMENT
Strepto – chains
Staph – clusters
all bacterial cells have
Cell membrane
Cytoplasm
Ribosomes
Cytoskeleton
DNA (usually one circular chromosome, may also have plasmids)
most bacteria have
Cell wall
Glycocalyx - surface coating (slime)
some bacteria have
- Flagella - involved in motility
- Pili - involved in motility (gliding and twitching motility); involved in DNA transfer from one cell to another
- fimbriae - hairlike appendages that allow for attachment
glycocalyx
- Surface coating external to the cell wall
- Viscous and gelatinous
- Made of polysaccharide and/or polypeptide
- Contributes to virulence (harmfulness of a disease):
- Prevents phagocytosis (engulfs a larger particle)
- Helps form protective biofilms
- 2 types of glycocalyx
Capsule: neatly organized and firmly attached
Slime layer: unorganized and loose
special functions of the capsule
- Have greater likelihood to cause disease with a capsule than without
- Protects from other cells (ie white cells) to engulf / kill / perform phagocytosis to the bacterium
special functions of the biofilm
- Microbes attach to surfaces and grow into masses
- Biofilms protect bacteria from drying out, from becoming dislodged, and being destroyed
- Grow on rocks, teeth, medical implants, etc.
- Difficult to remove – a few cells left behind can regrow
- Responsible for persistent colonization of catheters, IUDs, pacemakers, and other implanted medical devices.
gram positive bacteria
- The thick layers of peptidoglycan in a gram-positive help to support the cell membrane and provide a place of attachment for other molecules.
- The thick Peptidoglycan layer also enables Gram positive bacteria to retain most of the crystal violet dye during Gram staining causing them to appear purple.