Bacterial Microbiology Flashcards
Give a few important characteristics of bacteria.
Small and unicellular, no intracellular organelles, haploid round chromosome, some have flagella, different cell wall
Explain gram staining and identifying bacteria-with a few exemples of shape and genus
Gram staining was developed in the 1800 and it distinguished between types of cell wall-pink is gram-negative and purple-gram-positive
gram negative-2 cell lipid wall, seperated by peptidoglycan-and Lipopolysacharides achored at the exterior eg: e.coli, salmonella, shigella
Gram positive-1 cell wall covered in large peptidoglycan exterior layer-and no LPS eg: Staph aureus, step pneumonia, step pyogenes
Bacterias can take many shapes, but main ones are cocci, bacilli and spirilli
Describe the 5 goals of a bacteria in its host
colonize (find a niche), persist (avoid, subject and escape immune system), replicate (aquire nutrients such as iron, energy and grow), disseminate (in cell or tissue-move around to grow more), cause disease (produce toxins that kills hosts, induce diarhea, dysregulate immune system)
Can bacteria be extra cellular? Intracellular? Both? Explain mechanisms if needed and give exemples of any
What does salmonella use for mobility and invasion?
Give another exemple of actin manipulation by bacteria?
They can be both-some extracellular are Staph, Strep, Neisseria
Intracellular pathogens aim to be uptaken into a vacuole-then want to escape the vacuole (Shigella, Listeria), survive in the phagolysosome (coxiella) or prevent fusion with lysosome (Salmonella, Chlamydia)
Salmonella moves around to find cells with a flagellae (motility), but also uses an injectisome to inject virulence proteins into the host-and cause actin polymerisation that forces uptake by membrane
Listeria also acts on actin-gets inside cell and use it to move around and go from cell to cell
What is horizontal gene transfer? Explain the 3 mechanisms. And what is a pathogenecity island
Transformation-DNA uptake. DNA in the solution is stipped into ssDNA and uptaken by the bacteriam then integrated into the bacteria chr
Conjugation-Replication of plasmid from one cell to another. Mating bridge form between bacteria, and some plasmids have gene allowing transfer-rolling replication through the bridge into new cell-each have the plasmid
Transduction-bacteriophages infest bacteria-and when they package, can inadventerly pack up host DNA-then when integrate into genome of other bacteria, gene added
A pathogenecity island in horizontally acquires DNA that contribute to virulance-packaged and expressed together and can usually be the cause of illness
List the 6 main portals of entry for pathogens in the body, give an example of each and explain possible sources. Quickly explain expected and unexpected pathogens
Upper respiratory tract -S.pneumoniae, Stomach-Heliobacter pylori, Skin-Staph epidermis, Mouth-Strep spp, Small Intestine-E.coli, Lower genital tract (Lactobacillius)
Bacteria usually come from 2 sources-extrinsic (environement) or Intrinsic (from own body)
Expected bacteria/entry are bacterias that usually live in the body, like small intestine of vagina (harmless)
Unexpected pathogens are those tnetering
Describe the URT as a portal of entry for bacteria. Give exemples of pathogens, disease and dangers
URT-usually extrinsic bacteria acquired from other URT-airborne on droplets, airborne or hand as intermediates
Exemples of bacteria: Step spp (dental), Step pneumoniae, step pyogenes, strep pneumo, neisserisa meningitis
If it reached throat-tonsilitis, parynghytis
From there, can either stay around and replicate (middle ear infection) and in some cases, reach trough the bone into brain-brain abcesse or meningitis (Neisserissa particularly good at that)
Or can go down to Lower RT (lungs), causing bronchitis, pneumonia (Step pneumoniae good at that)
All of these routes, if left too long can reach the bloodstream-bacteraemia-systemic damages can causes spesis-immune response usually the danger
Describe the Urogenital tract as a portal of entry for bacteria. Give exemples of pathogens, disease and dangers
Urogenital (vagina, urthra, penis, bladder) can be extrinsic (catheter) or intrinsic (large intestine/colon or surgery)
Usually URINARY intrinsic-exemples are (E.Coli, Klebstriella, Enterobacter, candida) but can be exterinsic (catheters mostly E.Coli and Klebstriella)
Usual genital tract are- Extrinsic-stepp group B (pregnancy), candida or extrinsic (STD’s-Neisserissa gonorrhoae, chalmydia, syphilis)
Consequences of genital (gonnococal urethritis, pelvic inflamation disease, tubo ovarian abscesses), pregnancy (neonatal step group B, neonatal gonococcal), or Urinary (cystitis, pyelonephritis (spread to kidney)
all these can spead to the blood again-cause dangerous bacteremia
Describe Broken Skin as a portal of entry for bacteria. Give exemples of pathogens, disease and dangers
Many sources: Surgery/wounds, skin diseases, synringes (drugs), Insect bites, animal/human bites, IV
Usually skin pathogens are opportunistic-those not are Staph aureus, strep pyogens , in hospital MRSA, or after surgery of gut-exposure. Unusual bacteria can come in-Pasteurella from dogs, Aeromonas Hydrophilia from leeches, Clostridium Perfingens from soil
Consequences can be superficial infection, cellulitis, abcesses, fascilits, myosisys, grangrene, and ofc bacterimia
Describe the feaco-oral route as a portal of entry for bacteria. Give exemples of pathogens, disease and dangers
Also called gastrointestinal-bacteria that target stomach
Exemples: E.Coli, Shigella, Cholerae, Salmonella, listeria, Clostridium difficiles
Usually cause diarhoeal illnesses-Vomiting, D&V, diarhoae, dystentry (bloody stool). Toxins can spread and cause diarhoae or neurological damage (botulism)
Can also spread to be systemic after a while (typhoid (s.tyohi), listeriosis (listeria), salmonella and sceptic arthiritis and aortitis
Define pathogens, commensals, pathogencity factors affecting pathogencity, infectious dose and factors affecting it, virulance and exemples of virulence
Pathogens are bacteria that cause diseas (true-always and can infect healthy being, opportunistic-take advantage of weakness/other illness)
Commensals are bacteria that do not cause disease
pathogenicity is the ability to cause disease
Its affected by infectivity (features favoring infection)- such as transmission, ability to colonise, tropism, replication, immune evasion
and its affected by virulence (features that cause disease) such as toxin production, enzyme that degrade host molecules, interuption of host processes and complete immune evasion
Infectious dose is the number of bacteria required to cause an infection-affected by route (stomach-acid requires high numbers), ability to colonise host (adherence, etc), Tropism and motility (where they want to live, how easy is it to get there-cholerae has flagella), replication speed (faster usually better-but TB is so slow it evades immune system), and immune evasion
Virulence can be caused by toxins (pneumolysin made by S pneumoniae makes a pore in cells-affect lung architecture), Degradation of host molecules (eg Hyaluronan lyase-degrades host EC for nutrition and spead), Interference with host function (Superantigens by S.Aureus interfere with T cell activation) and immune evasion (S aureus leukocidins killd neutrophils, causing absesses)
What are Beta lactams? Give a few exemples
Beta lactams are a type of anti-biotics that interfere with peptigoglycan cell wall synthesis-kills bacteria
penicillin, methicilin, imipenem
What is an antibiotic? Where do they come from? What are different terms to describe their function?
Antibiotics describe any form of antomicrobial agent produced by a microorganism or inhibits microorganism
Classically, most Abx come from soil dwelling fungi (Penicillium) or bacteria
But today, Use range of natural, semi-synthetic or synthetic chemicals
Antimicrobial-chemical that selectively kills miccrobes
Bacteriocidal (kills bacteria), Bacteriostatic (stops bacteria from growing), Antispetic-chemical killing microbes to stop infection
What is meant by Abx resistance? Why does it arise?
It describes the ability for a bacteria to grow above the breakpoint (maximum clinically achievable concentration)
Minimal inhibitory concentration-lowest conc of Abx required to inhibit growth
Abx resistance exist naturally (and always has), but Abx use provides selective pressure-only those with resistance survive and proliferate, and if they do, take over-so survivors are Abx resistant
Give exemples of the main Gram negative and gram positive Abx resistant bacteria?
Gram - : Pseudomonas aeruginosa, E.Coli, Klebstriella, Salmonella, Neisserissa ghonorrhoae
Gram +: Staph aureus (MRSA), Strep pneumoniae, clostrum difficile, enterococcus, mycobacterium
