Micro – test 1 – Flashcards
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Unlock answers| infectious disease |
| a disease in which pathogens invade a susceptible host and carry out at least part of their life cycle in the host |
| endogenous infection |
| an infection that you get from a microorganism that has already been inside your body which spreads to another part of your body -> flora |
| exogenous infection |
a foreign microorganism that causes an infection inside your body -more than 1/4 of all deaths globally |
| top 7 causes of death from infectious disease |
acute respiratory infections aids diarrheal diseases - dysentary TB Malaria Measles Hep B |
| microparasites |
replicate inside a host and produce large # of progeny and potentially serious infection. -bacteria, viruses, protozoa, fungi -can be intracellular (viruses) or extracellular (entamoeba) -intracellular have access to nutrient, supply genetic material, and can avoid immune response |
| macroparasites |
typically have one infectious stage maturing into a reproducing stage with offspring exiting the host -arthropods, helminths (worms) -only extracellular -> feed on host cells or take up nutrients from tissue fluids |
| vector |
| generally arthropods that carry a disease and trasmit that disease to another organism |
| Bacteria |
-single celled prokaryotes -have long circular DNA with no envelope found in the nucleoid -cell wall is complex and often has a thick capsule |
| obligate aerobes |
| require oxygen to live |
| obligate anaerobes |
| unable to use oxygen for energy-yielding reactions; are harmed by oxygen |
| facultative anaerobes |
| can use oxygen when it is present but are able to continue growth via fermentation or anaerobic respiration when O2 isn't available |
| microaerophiles |
| require oxygen; grow in oxygen concentrations lower than air |
| bacterial cell wall |
peptidoglycan;is the main component providing a hydrophilic surface -elicits innate immune response in humans |
Procedure for Gram staining (important to know) |
1. bacteria are heat fixed or dried on a slide 2. stain with crystal violet and gram's iodine 3. excess stain removed by washing w/ acetone-based decolorizer and water 4. red counterstain (safranin) is added -gram negative bacteria will stain red and gram positive will stain purple -the extra outer layer of gram negative bacteria serves as a structural barrier for the violet to reach the peptidoglycan layer -during decolorization, the outer layer is removed, and then gram negatives are stained with counterstain, which is lighter than the original stain -gram staining doesn't work for: ;starved cells, old cells in the stationary phase, cells treated with antibiotics/antibacterials etc., mycobacteria (waxy outer shell)/ mycoplasmas (no peptidoglycan) |
| gram positive bacteria |
-have thick multilayered cell wall made of peptidoglycan surrounding the cell membrane -peptidoglycan can block phagocytosis and induce fever -no outer membrane -lysozyme sensitive -thicker cell wall -no lipopolysaccharide -no production of endotoxin (mainly exotoxins) |
| gram negative bacteria |
-outer membrane is both hydrophilic and hydrophobic due to lipid unique to GN bacteria -porins;(special pores made of protein) allow for passage of nutrition -lipopolysaccharide on the outer membrane confers antigenic and toxic properties -lysozyme resistant -thinner cell wall -endotoxins releases upon destruction of cell |
| bacterial shapes |
coccus - spherical (staphylococcus) diplococcus - two spherical cells together (streptococcus) bacillus - rod shaped (ecoli) spiral or spirillum - snakelike (borrelia) |
| transformation |
| bacteria take up fragments of naked DNA and incorporate them into their genomes |
| conjugation |
| a one way transfer of DNA from a donor (male) cell to a recipient (female) cell through the sex pilus |
| Transduction |
the transfer of genetic material from one bacterium to another via a bacteriophage (bacterial viruses with extrachromosomal genetic elements). -once in a cell, a transposon can jump between plasmid to plasmid or plasmid to chromosome |
| cell wall synthesis |
1. production of the basic bulding block takes place inside of the cell 2. precursor unit is carried from inside the membrane outside. ;The basic units are modified (adding second sugar) and are covalently linked to the preexisting cell wall -drugs that target this stage require active division of the bacteria 3. a variety of reactions that cross link peptides in the cell wall |
| types of AB therapy |
prophylaxis - prevantative empiric - broad spectrum ABs cover many but not all pathogens definitive - know what pathogen is and tailor therapy to the specific disease state |
| viruses |
- cannot make energy or proteins independant of a host cell - contain RNA or DNA - have to be able to use host processes to produce proteins, viral mRNA, copies of the genome - have single stranded or double stranded, linear or circular DNA or RNA within a capsule (capsid) - virus may only be a nucleocapsid or it may have an outer membrane or envelope |
| lytic infections |
viruses replicate, produce new viruses, and they are released when the cell lyses ; |
| persistent infections |
| the infected cell survives and releases particles slowly |
| latent infections |
the virus is quiescent with the DNA or RNA existing in the host's cytoplasm or in the host's genome -replication takes place when some type of activation occurs |
| classification of viruses |
-biochemical properties: mode of replication -strucure: size, morphology, nucleic acids -associated disease -mode of transmision -host cell -target tissue or organ |
| fungi |
-multicellular, branching filamentous (hyphae) forms or as unicellular yeast -distinguished from other eukaryotes by a rigid cell wall made of chitin and glucan and a cell membrane with ergosterol instead of cholesterol Mycelium- mass of hyphae |
| types of fungal infections |
superficial- body surface cutaneous or subcutaneous- nails, subcu skin systemic- internal organs, systems opportunistic- cause disease in immunocompromised hosts |
| protozoa |
reproduction usually asexual; sexual (rare) in an arthropod vector -common in tropical, subtropical regions -intracellular parasites- infect erythrocytes, macrophages, brain, muscle, and epithelial cells -;;nutrient uptake from host cells -extracellular pathogens- infect the blood, intestines, urinary or reproductive tracts -; nutrient uptake from host cells or ingest whole cell |
| protozoan survival mechanism |
-can continuously change surface antigens -develop into cyst form under harsh conditions -consume complement at the cell surface (blocks immune response) -intracellular protozoans can evade intracellular enzymes -utilize aerobic and anaerobic respiration ; |
| 3 major disease causing helminths |
flatworms: tapeworm (cestoda), flukes (trematoda) roundworms: (nematoda) ; |
| helminth modes of transmission |
-fecal oral route - accidental ingestion of eggs or larvae originating from feces of infected host -intermediate host - accidental ingestion of larvae in tissue of another host -active penetration of skin - larval stages invade through skin -injection by blood-sucking insect - larval stages develop to infectivity in insect |
| risk factors for becoming infected in human patients |
| poor hygeine, improper food prep, unsanitary conditions, improper hand washing, dealing with pets, outdoors, warmer tropical climates, open wounds |
| arthropod transmission of disease |
direct: cause disease by feeding on a host -the bite itself is the "disease" indirect: transmission of pathogens as they feed -bite causes another disease ; |
| symbiosis |
commensalistic- a relationship of convenience -one benefits, the other is unaffected mutualistic- a relationship with mutual benefits -both parties benefit parasitic- only one party benefits, while one party is adversely affected |
| Koch's postulates |
1. the microbe must be present in every case of the disease 2. the microbe must be isolated from the diseased host and grown in pure culture 3. the disease must be reproduced when a pure culture is introduced into a non-diseased susceptible host 4. the microbe must be recoverable from an experimentally infected host |
| exceptions to Koch's rule |
viral diseases cannot be cultured cannot always find an equivalent experimental host some pathogenic diseases are co-infections ; |
| Common Cold |
-most common infectious disease. ;more than 200 agents cause colds. ;spread by nasal/oral transmission and fomites -rhinoviruses (picornaviridae)cause at least 50% -coronavirusus (coronaviridae) cause 20% -incidence decreases with age -; more IgA AB's -may spread to sinuses, LRT, middle ear |
| exotoxins |
toxic proteins produced by some bacteria (mostly gram positive) and secreted or released after lysis
|
| endotoxins |
| part of the outer portion of the cell wall (lipid A) of most gram-negative bacteria, released on destruction of the cell |
streptococcal pharyngitis (strep throat) |
Streptococcus pyogenes -gram positive coccus; facultative anaerobe -produces many exotoxins (streptolysins -> cause lysis of pharyngeal cells and produce spots) -cause of 95% of bacterial sore throats -can spread causing rheumatic fever |
cytomegalovirus infection (CMV) -(pharyngitis) |
-largest human herpesvirus (herpesviridae) -acquired from most bodily secretions and blood -originally called salivary gland virus- transmitted by salivary glands. Persistant and latent infections; remains latent in neutrophils, t-cells, and monocytes -often asymptomatic but can spread to lymphoid tissue, then salivary glands, kidneys, reproductive organs -dangerous to babies CMV: enlarges cells that it affects |
| Epstein-Barr virus |
-infectious mononucleosis (fever, anorexia, lethargy, splenic rupture) -herpesvirus transmitted in saliva -replicates in B-cells -shed in saliva from infected salivary glands and spreads to B-cells in lymphoid tissue -T-cells proliferate in response to infected B-cells |
