Microbiology Flashcards
Gram stains
PiNk = Negative Purple = positive
Shapes of bacteria
Spheres = cocci Rods = bacilli Spirals = spiralli
2x cocci = diplococci
Groups of cocci = staphylococci (staph = staff = gathered together)
Strips of cocci = streptococci
Haemolysis
Alpha = green = partial = strep viridians + strep pneumonia B = better = complete = staph aureus Gamma = no hameolysis = enterococcus
Commonest cause of bacterial meningitis?
Neisseria meningitis
Why are gram positive cells stained purple?
They have a thicker layer of peptidoglycan in their cell wall and retain more of the crystal violet
Define commensal
Part of the normal flora
Define ‘opportunistic pathogen’
Normally causes disease in immunocompromised patients
Define contaminant
Grows in culture by accident
Define pathogenicity
Ability of an organism to cause disease/infect host
How can you differentiate between staphylococci and streptococci?
Staph - coagulase
Strep - haemolysis
What bacteria is gram positive and positive to coagulase?
Staph aureus - most common cause of wound/skin infections
Explain the enzyme mechanism behind complete and partial hameolysis
Complete = enzymes break down RBC Partial = enzymes denature Hb
What are the 4C’s and why do we avoid them?
Cephalosporins
Co-amoxiclav
Ciprofloxacin
Clindamycin
Increased risk of C.diff
Describe the bacteria which causes gonorrhoea
Neiserria gonorrhoea
Gram negative diplococci
What kind of organism is neisseria?
Gram negative diplococci
Name the 6 coliforms - gram negative large bacilli
What is the first line antibiotic in treating infections caused by coliforms?
Gut Commensals-
E.coli
Klebsiella
Proteus
Gut Pathogens-
E.coli 0157
Shigella
Salmonella
Gentamicin
What are the two catergories of antibiotics?
Bactericidal = kill bacteria Bacteriostatic = inhibit bacteria growth
Name the 3 things antibiotics can work in a bacteria cell?
Cell wall - interfere with peptidoglycan synthesis
Ribosome - interfere with protein synthesis
DNA - interfere with nucleic acid synthesis
What toxins do gram postive and gram negative bacteria release and where from?
Gram positive - exotoxin - produced inside cell and exported out
Gram negative - endotoxin - part of the cell wall
What antibiotic is first line in gastroenteritis? What must be noted about this antibiotic?
Gentamicin (most effective against gram negative - which often cause gastroenteritis)
It cannot be taken orally - IV or inhaled only
What antibiotic should be offered to patients who are penicillin allergic?
Doxcycline or clarithromycin
What antibiotics contain a beta-lactam ring?
Penicillins
Cephlasporins
What antibiotics work by attacking the cell wall and give an example of each type?
How are they all excerted?
PCG - penetrate cell gates
Penicillins - fluoxicillin
Cephalosporins - ceftriaxone
Glycopeptides - vancomycin
Via urine
What antibiotics work by attacking bacterial ribosomes (as these differ from mammial ribosomes it is possible)?
What is the only group of that is excreted via urine rather via the gut (via the liver -> biliary tract first)?
What is the only type that is bacterocidal as opposed to bacteriostatic?
TAM - Tam big on loads of protein
Tetracyclines - doxycycline
Amino-glycosides - gentamicin
Macrolides - erythromycin
Amino-glycosides excreted via urine and bacterocidal
What must be noted about delivery of glycopeptides e.g. vancomycin?
IV administration only
Only given orally in C.diff - when it works topically on gut lumen
Name 3 DNA attacking antibiotics
Metronidazole
Trimethoprin
Fluroquinolones
How can bacteria become antibiotic resistant?
Genetic mutation
Transfer of DNA between one antibiotic resistant bacteria to another by:
- Transformation
- bacteria die and DNA is released which can be scavenged
- Conjugation
- bridges can be formed between bacteria and DNA transferred (plasmid replicates and transfers over)
- Transduction
- Viruses infecting bacteria can transfer bits of DNA from one to another
What kind of bacteria is C.diff?
gram positive bacilli
Describe the microorganism most likely to cause urine infections
E.coli
AEROBIC Gram negative bacilli
What effect can macrolides such as erthymocin, azithromycin have on ECG?
Elongate QT interval
Side effect of tetracyclines
Photosensitivity
think of claires burnt arse
