Microbiology review Flashcards
Bacteria is…
prokaryotic
Small, primative & simple. They lack membrane bound organelles (have no nucleus, golgi, ER, mitochondria, or vacuoles)
2-10 uM
fungi & protozoa are…
eukaryotic
viruses are…
non-cellular
how may microorganisms are pathogenic
less than 3%
Explain the binomial nomenclatures system
first work = genus
second word = species
how are bacteria classified
- O2 requirements
- metabolism
- differential staining
- motility
- pathogenicity
- morphology
- *Mostly done with DNA sequence these days
how to describe bacteria shape
grouping-shape
bacterial cell structure:
- Circular DNA
- abundent ribosomes
- cell envelope = membrane & cell wall
- gelatinous capsule
- flagella for locomotion
- pilli for attachment/ transfer of genetic material
Gram +
thick peptidoglycan then protein cell membrane
Gram -
lipopolysaccharide then peptidoglycan
explain bacteria growth
binary fission (mitosis/identical cells) ca double every 1-24hr -some are highly resistant endospores
Bacteria are the…
most numerous & pervasive oragamism (ubiquitous)
Normal flora
life on/in GI tract, resp, mucous membranes, skin, ears
NOT NORMALLY in the blood, urine, lymph, CSF
-they inhibit pathogens
-secrete antimicrobial toxins that alter ph
-compete for nutrients /space
-stimulate immune defense
What is pathogenicity
ability to enter host & cause disease
these are complex interactions between pathogen & host
what is opportunistic pathogens
normal microbiota become harmful if poortunity rises such as immunosuppression, disturbances in flora, barrier damage, organisms in unusual locations
what are pathogenic factors
1) Virulence (how likely to cause disease)
2) Invasiveness (chemicals that allow invasion/adhesion)
3) Toxins (Endotoxins released when cell lyses or dies) (exotoxins secreted by cells)
what are host factors
1) compromised immune system
2) malnutrition
3) invasive procedure, injury, stress
4) other infections
What are reservoirs of infection
human, animal, plant, soil, food, water, fomites (inanimate surfaces)
What are the modes of transmission
Direct contact - fluid/skin
Airborn - Respiratory droplets
Contamination- water, food, fomites
animal contact
what is a bactericide
it destroys bacteria
what is bacteriostatic
inhibit growth of bacteria (not sterile)
what is antiseptic
applied to body surface
what is disinfectant
applied to surface of objects (not sterile)
What are antibiotics
antimicrobial agents used in treatment & prevention of bacterial infections
What are ideal antibiotics
Highly toxic to pathogen
- favourable pharmodynamics (what the drug does to the body)
- Favourable pharmokinetics (what the body does to the drug. eg. metabolism)
- not likely to cause resistance
what is antibiotic resistance
Bacteria are always reproducing by cloning. Sometimes there is mutation errors, causing abnormal bacteria to be produced & cloned further.These abnormal bacteria with the gene mutation sometimes prove to be a new resistant strain of bacteria. but since it’s only a few among millions its ok. When antibiotics are used when they aren’t needed they kill all the non-mutated bacteria & leave only the clones with mutations that allow the antibiotics to not work… so then these ones with mutation will continue to reproduce by cloning & now you only have the mutated resistant bacteria cloning & thriving while the susceptible bacteria has all died.
what are some modes of antibiotic action
- inhibit cel wall synthesis
- inhbit protein synthesis
- distrupt cell membrane
- inhibit bacterial enzymes
- inhibitDNA/RNA synthesis
explain viruses generally
very small (0.2-0.02 um) (much smaller than bacteria)
not cellular (protein capsule surrounded by genetic material
-OBLIGTE INTRACELLULAR PARASITE
-can’t reproduce w/o host
-cannot produce eng..
what is the structure of viruses
genetic material = DNA/RNA protein coat = capsid -some have protective envelope -no cell membrane or organelles -viral spikes recognize & buds to SPECIFIC receptors on host cell membrane -geometric/symetrical shape
what is viral host specificity
The viral spikes recognize specific receptors on specific host cells
- Hepatitis -> hepatocyes
- HIV -> T cells
- norovirus -> epithelial cells of intestine
- Rhinovirus -> lining of upper resp tract
explain the general virus life cycle
1) viral spike recognizes host cell
2) virus enters cell
3) host cell makes viral RNA “transcription”
4) host synthesizes viral DNA
5) Host cell assembles virus
6) aquire a glycoprotein envelope as they exit
7) new virus
explain the LYTIC CYCLE
“Virulent” ex. Cold sore
- viruses assembled by host cell
- cause host cell lysis when they escape
- may be triggered by: Stress, decreased immune system, infection or tissue damage, environmental risk factors (heat, cold, UV light)
explain the LYSOGENIC CYCLE
“temperate”
- viral DNA incorporated into host genome
- host replicate viral DNA as it divides
ex. Chickenpox/shingles
what is an oncogenic virus
cancer coughing
-insertion of viral DNA into host genome may trigger transformation if genes that regulate cell division or growth (proton-oncogenes) are affected
-ex. Epstein barr virus -> burkitts lymphoma
papilloma virus -> cerival cancer
hepatitis b -> liver cancer
How do you control viruses
- ANTIBIOTICS DONT WORK
- antiviral agents are often toxic to host
- most disrupt viral life
- most effective control of viruses is achieved by vaccination
what is mycoses
disease caused by fungi
characteristics of fungi
often opportunitistic, can be caused by use of antibiotics where normal flora are disturbed.
many antibiotics are made from fungi
(Athletes foot, ring work, candida, lung infection)
characteristics of protozoa
- most are non-pathogenic but some single celled eukaryotes are parasites
- route of infection by oral ingestion or transmission by animals
(eg. Malaria, toxoplasmosis, schistosomiasis, giardia)
characteristics of metazoan
some muilticelular parasites cause disease
round works, tapeworms, flukes
