Flashcards in Scenario 15 Deck (102)
What are the 3 classes of microorganisms?
Viruses, prokaryotes (bacteria/ mollicutes), eukaryotes (fungi, protozoa, nematodes, ectoparasites)
What is the difference between a parasite and commensal?
Both live in/ on another organism but commensal does not injure the organism
What colour is gram positive?
What colour is gram negative?
What classification are mycobacteria?
Gram positive but dont take up aq gram stain- walls made up of waxy my colic acid (use ziehl nelson stain)
What are the properties of gram positive bacteria?
survive well on drying some produce spores/ toxins and have teichoic acids in their cell wall
What are the properties of gram negative bacteria?
dont survive drying, no spores, have endotoxin in their cell wall (LPS)
Is staph aureus gram negative or positive?
Gram positive coccus which forms clusters
What are some distinguishing factors of staph aureus?
Grow readily on blood agar, golden colonies after 48 hours, coagulase and DNAase production
What are the virulence factors of staph aureus?
Protein A- anti-phagocytic and secretes coagulase and exotoxins
Where is it found/ transmitted?
Normal human flora, transmission from some carriers and close contact
What infections does staph aureus cause?
Skin and soft tissue, ENT, pneumonia, bone and joint, sepsis, infective endocarditis, implanted prosthetics
What toxin mediated problems does it cause?
Staphylococcal toxic shock and food poisoning
What do you use to treat s aureus?
NOT penicillin- 90% resistant sue to beta lactamase, can use fluoxacillin or co-amoxiclav or macrolides (erythromycin) for MRSA use vancomycin
How do you classify streptococcus pyogenes?
gram positive cocci in chains, grows readily on blood agar
What are the virulence factors of s.pyogenes?
M protein in cell wall and endotoxins
Where is it found and how is it transmittes?
In nose and throat of 1-5% of population and transmitted by close contact
What infections does s.pyogenes cause?
pus forming, ENT and RT, skin and soft tissue (impetigo), puerpal fever, blood stream, streptococcal toxic shock
What are some post infecitve manifestations of s.pyogenes?
non suppurative sequalae, acute rheumatic fever, acute glomerulonephritis
How do you treat s.pyogene?
PENICILLIN OR AMOXICILLIN erythromycin, vancomycin if allergy
How do you distinguish streptococcus pneumonia?
Gram positive cocci in pairs/short chains up to 4 cells long, produced pheumolysin in alpha haemolysis on blood agar
What are the virulence factors of s. pneumo
pneumococcal teichoic acid c-polysaccharide and polysaccharide capsule which is anti-phagocytic
Where is it found?
Commensal URT flora in humans, transmission by resp secretions
What infections does s.pneumo cause?
URTIs, LRTIs, CNS (meningitis), sepsis, peritonitis, endocarditis
What is the treatment for s.pneumo?
2 vaccines in UK, penicillin (90%), erythromycin (not in meningitis), ceftriaxone in meningitis
What are some other gram positive bacteria?
Coagulase-negative staphylococci (normal skin flora, implanted prosthetics), Clostridium (spore forming rods, commensals in GIT produce endotoxins, difficile, tetani, botulinum, perfringens) Bacillus (rods, anthrax and cereus), cornyebacterium species (non spore forming rods, skin commensals)
What are the distinguishing factors of E coli?
gram negative bacilli, grow on blood agar, fements lactose, cell wall contains LPS, proteins and porins, motile (flagellae, fimbiae)
What are the virulence factors of E coli?
LPS, iron binding proteins, small polysaccharide capsule, fimbiae or pili, endotoxin priduction
Where is it found and how is it transmitted?
normal colonic flora, contaminated food/water, ascending infection