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.
gram negative bacteria
- In gram-negative bacteria, the peptidoglycan layer is a single thin layer compared to the thick layers in gram + cells.
- The thin layer does not retain the crystal violet light but picks up the pink colour of the counter stain (Safranin) during gram staining
plasmids
- Nonessential pieces of DNA
- Can accumulate protective traits such as drug resistance and pathogenic traits
- Can be transferred from one bacteria to another
- “Survival of the fittest”
ribosomes
- Site where genetic material is made into protein molecules
- Ribosomes consists of a large and small subunit
- Small subunit: 30S
- Large subunit: 50S
- Large and small subunits together: 70S
bacterial endospores
- Dormant, tough, non-reproductive structure
- Produced by Clostridia, Bacillus, and Sporocina
- Bacillus anthracis: agent of anthrax
- Clostridium tetani: cause of tetanus
- Clostridium perfringens: cause of gas gangrene
- Clostridium botulinum: cause of botulism
- Clostridium difficile: “C. diff,” a serious gastrointestinal disease
- Most endospores ensure the survival of a bacterium through periods of environmental stress
- Endospores resist extremes of heat, drying, freezing, radiation, and chemicals that would kill vegetative cells
- Can be vegetative or sporulative (cells start to grow again)
prokaryotes
No nucleus
One circular chromosome
No organelles
Peptidoglycan cell walls
Divides by binary fission
Bacteria are prokaryotic cells
eukaryotes
Distinct nuclear membrane
Paired chromosomes inside nucleus
Organelles
Polysaccharide cell walls, when present (plants)
Divides by mitosis
viruses
- Viral replication is intimately associated with the host cell
viruses are obligate intracellular parasites - Acellular (or non-cellular)
- Consist of DNA or RNA core
- Core is surrounded by a protein coat (capsid)
- Contains spikes—projections from outer surface of the envelope
- Viruses infect every type of cell, including bacteria, algae, fungi, protozoa, plants, and animals.
- Millions of viruses found in a milliliter of sea water
- Can be simple or complex shapes
H1N1
- 2009 pandemic
- Resulted from the reassortment of viral genetic information from multiple (four) influenza A viruses
- the individual gene segments of the virus originated from humans, birds, North American pigs and Eurasian pigs
- Highlights the need for better surveillance of viruses – something we learned again during COVID19
- Early detection and intervention is key
- SARS-CoV2 (COVID19) -> did we apply what we learned from H1N1 adequately?
Ebola
- Can be transmitted between humans and wild animals
- Fatality rate around 50%; early intervention important
- Vaccine has been developed to be used in countries where outbreaks have occurred
- Mode of transmission: blood, other bodily fluids, and objects contaminated with those fluids
- Symptoms: fever, fatigue, muscle pain, headache, sore throat, vomiting, diarrhea, rash, failing kidneys/liver, internal and external bleeding
fungi
- Eukaryotes
- Yeasts are unicellular
- Molds and mushrooms are multicellular
- Thousands of species
- Examples: oral candidiasis (thrush), tinea infections (athletes foot), aspergillosis, blastomycosis, onychomycosis (nail infection)
- Think COSIS
protozoa
- Eukaryotes
- May be motile via pseudopods, cilia, or flagella
- Free-living or parasitic (derive nutrients from a living host)
- Name comes from the Greek for “first animals”
- Most are harmless, living in the environment around us
- A few species of parasites are responsible for hundreds of millions of infections each year
- Common protozoan infectious diseases include malaria, giardiasis (“beaver fever”) and toxoplasmosis (common parasite) (get it from undercooked meat, cat feces, contaminated soil)
algae
- Eukaryotes
- Cellulose cell walls
- Found in freshwater, saltwater, and soil
- Use photosynthesis for energy
Algae blooms
- Can produce toxins
- Can cause harmful effects to humans
- Can kill marine life
multicellular parasites
tape worms
hookworms
pinworms
tapeworms
- Inhabits intestines of humans and other animals
- May be up to 10m long
- Each segment in chain has reproductive organs
- Can be transmitted in feces and infected food (with worms or eggs)
- Nausea, vomiting, diarrhea, weight loss
hookworms
Lives in small intestines
From no symptoms to GI symptoms, anemia and protein loss
Worms are usually treatable with anti-helminthic medications
pinworms
- Enterobius vermicularis
- tiny (2–13 mm) nematodes that cause enterobiasis or - “pinworm infection”
- Very common
- Common symptoms are anal itching (especially at night!) and abdominal pain
- Route of transmission: fecal – oral route
- Treatment = Vermox
fomites
microorganisms that can survive on surfaces (tables, floors, bedding, etc)
vehicle
a single contaminated source spreads infection
can be a common source
point source: food borne outbreak from infected food
vector borne
transmission by insect or animal vector
mosquitoes, ticks
granulocytes
neutrophils, eosinophils and basophils
Agranulocytes
Lymphocytes and monocytes
myeloid cells
associated with innate immunity
lymphoid line
associated with adaptive immunity
innate immune system
Initial response to microorganisms
- the immediate innate immunity response includes: (0-4hr)
- enzymes and peptides (building blocks of proteins)
- complement system proteins
- anatomical / physical barriers (ie mucous membranes, skin, etc)
the early induced innate immune includes: (4-96hr)
- phagocytic cells: macrophages & leukocytes (neutrophils, eosinophils, and monocytes
- cells that release inflammatory mediators: such as mast cells, macrophages, and leukocytes (basophils and eosinophils)
- natural killer cells
complement system
The complement pathway carries out six beneficial functions for the innate immune system.
- facilitate an inflammatory response
- Promote phagocytosis
- Promote attachment of antigens to phagocytes
- Cause lysis of various pathogens
- Assists in activating naive B-lymphocytes during adaptive immunity
- Remove harmful immune complexes from the body
adaptive immunity
- antigen-specific defense mechanisms that takes several days to become operational
- antigens are brought to the lymphoid organs by dendritic cells (initially derived from monocytes) that where they are processed by naïve T-lymphocytes; antigens then are also brought to naïve B-lymphocytes
- Once the B and T lymphocytes are activated, they proliferate into effector cells
- These are then able to better fight the pathogens in the body
- Effector B cells are called plasma cells and secrete antibodies
- Effector T cells include cytotoxic T cells and helper T cells, which carry out cell-mediated responses
