Microbiology Flashcards
name infectious agents
parasites fungi bacteria viruses prion proteins
single cell parasites
protozoa
flagella
tall bacterial structures
pili
adhesion coccus bacteria
Bacillus
rod shaped bacteria
spirochaetes
spiral shaped bacteria
what are prion proteins
infectious proteins that have no DNA or RNA and cannot be removed by sterilisation or disinfectant
gram +ve stains
purple
gram -ve stains
pink
pathogen
harmful organism
commensal
organism that is part of a normal flora
opporunistic pathogen
probably only cuase infection in immunocomprimised patients
contaminant
organism that has got into a culture by accident
pathogenicity
ability of a microorganism to produce a disease
virulence
degree of pathogenicity of an organism
how does bacterial replicate
via binary fission
what does bacteria need to grow
correct temp
correct pH
food
moisture
4 phases of bacterial growth
lag phase
log phase
stationary phase
death phase
What are exotoxins
usually gram positive bacteria- produced inside a cell and exported from it
what are endotoxins
usually gram negative bacteria-part of gram neg bacterial cell wall
what are the functions of toxins
- cause release of cytokines from immune cells
- cause damage to red and white blood cells and make blood vessels leaky- reduced clotting ability, BP resulting in sepsis
what is sepsis
causes leaky blood vessels (poor tissue perfusion) and activated clotting systems (increasing risk of haemorrhage) gram -ve sepsis worse than gram +ve
moulds
produce spores (spreads in air) and hyphae (invades organ tissues)- does not gram stain
Aspergilus
usually targets immunocompromised patients
yeast
single cells that reproduce by budding
gram stain= large gram +ve oval
Gram +ve
purple stain= thick layer of peptoglycan and then just deep to that have a cytoplasmic membrane made of phospholipids
Gram -ve
pink stain= outer cytoplasmic mambrane, a middle thin layer of peptidoglycan and an inner cytoplasmic membrane
diagnostic methods for bacteria
- microscophy (gram film)
- culture
- antigen detenction (urine)
- serology (antibody detection in blood)
- PCR
Streptococcus
Gram positive cocci
aerobic
cocci chains
Alpha haemolysis (partial)
strep pnuemoniae and strep virdans
Beta haemolysis (complete)
group strep A (throat and skin infection )
group strep B (neonatal meningitis)
most pathogenic strep
strep pyrongenes (sore throat, skin and soft tissue infections and puerperal sepsis) severe life threatening in pregnant ladies
gamma haemolysis
none
Enterococcus
Gram positive cocci aerobic non-haemolytic normal gut commensal and cause of UTIs VRE- antibiotic resistant strains of E.faecium is v bad in hospitals
Staphylococcus
Gram positive cocci
cocci clusters
Staph aureus
coagulase positive (golden) wound and skin infections Tx: flucoxacillin common cause of bacteraemia (bacterial in blood) IV drug users toxic shock syndrome
Staph epidermis
Coagulase negative (white)
IV line infection
produces a surface slime to allow them to stick to plastic and other artificial things in the body
prosthetic heart valve or joint
Panton-valentine leucocidin
toxin of staph aureus that can damage white blood cells
MSSA
METHICILLIN SENSITIVE STAPH AUREUS
Fever cascade
antigen attacks macrophage
releases cytokines
travel to anterior hypothalamus of brain
stimulates production of prostiglandin E
resets bodys thermostat
body percieves its cold so shivers to conserve heat
Fever- growth of pathogens slow if temp increases
Fever cascade
antigen attacks macrophage
releases cytokines
travel to anterior hypothalamus of brain
stimulates production of prostiglandin E
resets bodys thermostat
body percieves its cold so shivers to conserve heat
Fever- growth of pathogens slow if temp increases
Gram negative cocci
- diplococci
- aerobic
- gonorrhoea
- bacterial meningitis
Coliforms
- gram neg bacilli
- aerobic but can be anerobic
how can you differentiate coliforms?
- biochem reactions
2. antigenic structures (either o antigen on cell wall or H antigen on flagella)
gut commensals
e.coli, klebsiella, proteus, enterobacter spp
gut pathogens
salmonella, shigella, e.cole 0157
Strict anerobes
gram neg bacilli
pseudomonoas aeruginosa
legionella pneumophilia
curved gram neg bacilli
campylobacter
h.pylori
Haemophilus influenzae
small gram neg bacillis, common cause of chest infection esp COPD exacerbation
Gram positive anaerobic bacilli
Clostridium spp- antibiotic assoc diarrhoea
part of normal bowel flora
produces spores
produces exotoxin- that causes severe tissue damage
clostridium perfringens
a severe soft tissue tissue infection following contamination of a wound
clostridium tetani
tetnus- a fatal paralytic illness
Gram neg anaerobic bacilli
bacteroides spp
normal gut commensals, only pathogenic when found in other sides
Tx: metronidazole
Mycobacteria
thick waxy outer coat
Ix: acid fast bacilli or ziehl neelson stain
TB
Stages of gene transfer
- transformation
- conjugation
- transduction
what is transformation
DNA from dead bacteria is taken up by the living bacteria and incorporated in plasmids or the bacterial chromosome
what is conjugation
sex pilus produced by one bacterial through which plasmid DNA can be transferred
what is transduction
viruses infecting bacteria can transfer bits of DNA from one bacterium to another
5 I’s of infection
Inhalation Ingestion Inoculation Mother to Infant Intercourse
Chain of infection
infectious microbe–>reservoir–> portal of exit–>modes of transmission–>portal of entry–> suceptable host (circle and key is to break chain)
when should you wash hands
before patient contact before aeseptic task after fluid exposure after patient contat after contact with patient surroundings
antibiotics
drugs that are used to treat or prevent infection caused by microorganisms
Bactericial
kill bacteria
Bacteriostatic
inihibit bacterial growth
narrow spec Abx
penicillin
Broad spec Abx
tetracycline
antibiotic resistance
- production of enzymes that destory ABX
- altered Abx binding sites
- alteration of cell wall porins
- up-regulating of efflux pumps
Antibiotics that work on cell wall;
penicillin
cephalosporins (ceftriaxone)
glycopeptides (vancomycin)
Gram positive
thick layer of peptidoglycan and a single phospholipid bilayer
Gram negative
thin layer of peptidoglycan and a double phospholipid bilayer
Penicillin
inhibit cell wall synthesis by preventing cross linking of peptidoglycan subunits beta-lactam Abx Excreted rapidly via kidneys type 1 hypersensitivity eg flucoxacillin, amoxicillin
Amoxicillin
gram +ve and -ve
co-amoxiclav= amoxicillin and clavulanic acid (inhibits the action of beta lactamase enzyme)
Cephalosporins
inhibit cell wall synthesis bactericidal beta-lactam abx may induce C.diff excreted by kidneys
Glycopeptides
gram positive effect
cell wall antibiotics
binds to end of growing chain and prevents cross linking and weakens bacterial cell wall
bacericidal
only effective agains gram +ve cell walls
EG VANCOMYCIN
Glycopeptides
gram positive effect
cell wall antibiotics
binds to end of growing chain and prevents cross linking and weakens bacterial cell wall
bacericidal
only effective agains gram +ve cell walls
EG VANCOMYCIN
Abx that inhibit protein synthesis
macrolides (erythromycin, clarithromycin and azithromycin) BACTERIOSTATIC
tetracyclines (doxacycline and minocycline) BACTERIOSTATIC
aminoglycosides (gentamicin) BACTERICIDAL
Macrolides
Lipophilic and pass through cell membranes easily (useful for infections where the bacteria ‘hides’ from the hosts immune system)
- excreted via biliary tract
Tetracycline
Doxycycline (IV, sometimes IM)
- Broad spectrum, can destruct intestinal flora (so increased secondary infections) - can permanently stain teeth of children <12 years
Aminoglycosides
EG. Gentamicin
-Inhibit protein synthesis but are bactericidal
-Mainly active against gram negative aerobic organisms
E.g. coliforms and pseudomonas aeruginosa
-Toxicity - kidney damage and damage of CN VIII - vestibulocochlear (deafness and dizziness)
-Excreted in the urine
Abx that act on bacterial DNA
- Metronidazole
- Trimethoprim
- Fluoroquinolones
Metronidazole
- Causes strand breakage of bacterial DNA
- Treat true anaerobic infections
- Interacts with alcohol
Trimethoprim
- Inhibits bacterial folic acid synthesis
- Some activity against some gram negative and some gram positive
- Exceted in urine
Fluoroquinolones
- Ciprofloxacin, Levofloxacin
- Prevent supercoiling of bacterial DNA
- Bactericidal
- Restricted use in order to prevent Clostridium difficile
- Weakens tendons, causes seizures
- Excreted in urine
Side effects of ABX
Gentamicin (renal and VIII nerve damage)
Ciprofloxacin (tendonitis)
Metronidazole (interacts with alcohol)
Broad spectrum Abs increase risk of C.Diff (avoid 4 Cs)
Abx to avoid in pregnancy
Trimethoprim + Metronidazole in first 3 months
Gentamicin, tetracycline and Fluoroquinolones avoided all together
Abx to avoid in pregnancy
Trimethoprim + Metronidazole in first 3 months
Gentamicin, tetracycline and Fluoroquinolones avoided all together
Lantency
virus that can become inactive then reactivate later
EG. Varicella-zoster virus remains latent in the dorsal root ganglia before becoming reactivated (shingles)
viral replication
1) Attachment
Interact with specific receptors in target cell, ligand > receptor
2)Entry
Endocytosis (non-enveloped viruses)
3)Uncoating
Viral nucleic acid released from capsid
4) Nucleic acid and protein synthesis
Host ribosomes used, host polymerases may be used also
5)Assembly
Nucleic acid and proteins packaged together
6)Release
-Budding(Virus released with envelope derived from host cell membrane) Doesn’t kill cell
-Lysis (Viruses accumulate until cell bursts)Kills cell
signs of recent infection
- detection of virus specific IgM antibodies
- detection of rising titre volume of virus sepcific IgG antibodies
immunity and virus infection
- Cytotoxic T lymphocytes - recognise proteins on cell surface as being foreign and will signal infected cell to commit suicide in order to prevent formation of new viruses
- Neutralising antibodies - IgG, IgM - prevent virus binding to cellular receptors
- Hep B and C have a role to play in primary hepatocellular carcinoma
Virus detection
PCR and antigen detection
Serology
antigen etection in blood
PCR
detects DNA or RNA and replicates it millions of times
Anthrax
disease of cows and sheep
enterotoxins
toxins that act in the gut- food poisoning
4 C’s
cephalosporins
co-amoxiclav
ciprofloxacin
clindamycin
