Microbiology Flashcards
Gram+ organisms stain…
Purple
Stain well due to thick peptidoglycan layer
Gram- organisms stain…
Pink
Thinner peptidoglycan layer doesn’t retain stain well
Endotoxin is produced by…
Gram- organisms
Part of the cell wall
Exotoxin is produced by…
Gram+ organisms
Exported from the cell
Gram+ cocci in chains are?
Streptococci
Gram+ cocci in clusters are?
Staphylococci
The test to classify different Streptococci spp.?
Haemolysis
Alpha (partial) - dark green - Strep. pneumoniae + viridans
Beta (complete) - yellow - Group A (pyogenes) and B Strep.
Gamma (none) - red - Enterococcus sp.
Examples of: Alpha-haemolytic Streptococci?
Strep. pneumoniae + “viridans” group
Examples of: Beta-haemolytic Streptococci?
Group A Strep. (Strep. pyogenes), Group B Strep.
Examples of: Non-haemolytic Streptococci?
Enterococcus sp.
The test to distinguish Staphylococcus aureus from other Staph. spp.?
Coagulase test
+ve = Staph. aureus
-ve = other Staph. spp. (common skin commensals)
Treatment of choice for Staph. aureus infection?
Flucloxacillin
Examples of gram- cocci in pairs (diplococci)
Neisseria meningitidis and Neisseria gonorrhoeae
Some examples of Gram- bacilli
H. pylori H. influenzae Coliforms Pseudomonas Campylobacter
Examples of coliforms that are gut commensals
E. coli
Klebsiella sp.
Proteus sp.
Examples of coliforms that are gut pathogens
Salmonella sp.
Shigella sp.
E. coli 0157
The name of the toxin produced by E. coli 0157 is…
Verotoxin (VTEC)
Treatment of choice for coliform infections?
Gentamicin
Examples of strict aerobes (2)
Pseudomonas sp. (Gram- bacilli)
Legionella sp. (Gram- bacilli)
Examples of strict anaerobes (2)
Clostridium spp. (Gram+ bacilli)
Bacteroides spp. (Gram- bacilli)
Treatment of choice for anaerobic infections?
Metronidazole
Genetic variation in bacteria is dangerous because…
Resistance to antibiotics may develop.
Gene transfer: Transformation
DNA from dead bacteria is taken up by living bacteria and incorporated into plasmids/bacterial chromosome.
Gene transfer: Conjugation
Sex pilus forms between bacteria to allow transfer of plasmid DNA.
Gene transfer: Transduction
Viruses can transfer bacterial DNA between cells they infect.
The 5 methods of spread of infection are…
Inhalation, Ingestion (faecal-oral), Inoculation (blood), mother to Infant, Intercourse (sex)
Viruses contain RNA or DNA, never both. True/False?
True
Size of their capsid (protein coat) limits space
Bactericidal antibiotics inhibit cell growth. True/False?
False
Kill bacteria directly - bacteriostatic inhibits cell growth
Vancomycin is part of which family of antibiotics?
Glycopeptides
Penicillins, cephalosporins and glycopeptides act on the bacterial ___ ___
Cell wall
Penicillins are bactericidal/bacteriostatic, safe/not safe in pregnancy, excreted via kidneys/urine/liver
Bactericidal, safe in pregnancy, kidneys
Flucloxacillin is a ___ spectrum antibiotic. Which organisms is it effective against?
Narrow
Staph and Strep only (1st line for Staph aureus)
Beta lactamase destroys which antibiotic?
Amoxicillin
Co-amoxiclav is probs the best antibiotic to have on a desert island - why?
Treats everything apart from Pseudomonas and MRSA
Can be taken orally or IV
Cephalosporins are bactericidal/bacteriostatic, safe/not safe in pregnancy, excreted via kidneys/urine/liver
Bactericidal, safe in pregnancy, kidneys + urine
Glycopeptides are only active against Gram _ cell walls
+ve
Can you name the 3 macrolides?
Erythromycin, clarythromycin, azythromycin
Gentamicin belongs to which class of antibiotics?
Aminoglycosides
Macrolides are bactericidal/bacteriostatic, safe/not safe in pregnancy, excreted via kidneys/urine/liver
Bacteriostatic, erythromycin safe in pregnancy, liver
Gentamicin [aminoglycoside] is bactericidal/bacteriostatic, safe/not safe in pregnancy, excreted via kidneys/urine/liver
Both bacteriostatic + bactericidal, not safe in pregnancy, urine
Name the antibiotics that act on bacterial DNA
Metronidazole, trimethoprim +/- sulphanimide, fluoroquinolones
Metronidazole is bactericidal/bacteriostatic, safe/not safe in pregnancy, treats aerobes/anaerobes
Bactericidal, safe in pregnancy, anaerobes (Clostridium and Bacteroides)
Trimethoprim +/- sulphonamide is bactericidal/bacteriostatic, can be combined with sulphonamide to form _____
Bacteriostatic, co-trimoxazole
The 4 antibiotics that most commonly cause C diff infection are…
Ciprofloxacin
Co-amoxiclav
Clindamycin
Cephalosporins (ceftriaxone)