microbiology Flashcards
What is virulence?
the degree to which a pathogen is pathogenic
What shape are cocci?
spheres
What shape are bacilli?
rods
what are the different types of agar?
blood
chocolate (cooked blood)
MacConkey
XLD agar
What colour do gram positive bacteria stain?
purple
what is the sequence for gram staining?
Come In And Stain
crystal violet
iodine
alcohol
safranin
What environments do gram positive bacteria prefer?
dry/dusty - skin colonisers
What environments do gram negative bacteria prefer?
wet/damp - mucous membranes
What test is used on gam positive cocci to differentiate staph from strep?
catalase test (staph=+, strep=–
What test is used to differentiate S. aureus from other staphs?
coagulase test (S. aureus = +)
What two groups are strep initially differentiated into?
alpha and beta haemolytic streps
What test is used to differentiate the alpha haemolytic steps?
optochin test
Which alpha haemolytic strep is optochin susceptible?
S. pneumoniae
(other streps - viridans are resistant)
What grouping is used to differentiate beta haemolytic streps?
lancefield grouping
What bacteria is group A lancefield?
S. pyogenes
What is the usual pathogen to cause CAP?
S. pneumoniae
What is the first line treatment for CAP?
oral amoxicillin
What are the most common pathogens to cause HAP?
E. coli, K. pneumoniae
What is the 1st line treatment for hospital acquired pneumonia?
IV co-amoxiclav and gentamicin
What type of gram positive rods are strict anaerobes?
clostridium spp - C. difficile
What are the 4 C’s associated with C. difficile infection?
clindomycin
cephalopsorins
co-amoxiclav
ciprofloxacin
What is the treatment for C. difficile?
stop inciting agent and start fidaxomicin or vancomycin
What is the usual pathogen to cause meningitis?
S. pneumoniae
How is meningitis treated?
IV cefotaxime or ceftriaxone (cephalosporins)
How is meningococcal septicaemia treated in the community?
IM benxylpenicillin
what test is used to split gram negative rods into two groups?
oxidase test (determines if bacteria produce certain cytochrome C oxidases
What test is used do differentiate the oxidase positive gram negative rods?
indole test
What gram negative bacteria is oxidase positive and indole negative?
pseudomonas aeruginosa
What gram negative bacteria is oxidase positive and indole positive?
haemophilus influenzae
What test is used to split the gram negative, oxidase negative bacteria into two groups?
lactose fermentation test
What are the non lactose fermenting gram negative bacteria?
proteus mirabilis
shigella spp
salmonella spp
What further test is done on the lactose fermenting gram negative bacteria?
indole test
Give an example of a lactose fermenting, indole positive bacteria
E.coli
Give an example of a lactose fermenting, indole negative bacteria?
klebsiella pneumoniae
What organism causes 90% of UTIs?
E. coli
What are the antibiotics used to treat UTI?
nitrofurantoin or
trimethoprim
What type of antibiotics inhibit cell wall synthesis?
glycopeptides
beta lactams:
- penicillins
- cephalosporins
- carbapenems
(usufell to treat gram +ve bacteria as they have thick cell wall)
Give an example of a glycopeptide
vancomycine
teicoplanin
Give an example of a penicillin
benzylpenicillin
amoxicillin
flucloxacillin
give and example of a cephalosporin
cephalexin
cefotaxime
ceftriaxone
Give an example of a carbapenem
imipenem
estapenem
What groups of antibiotics inhibit protein synthesis?
chloraramphenicol
macrolides
tetracyclines
aminoglycosides
Give and example of a macrolide
clarithromycin
erythromycin
(used instead of penicillins if allergic)
Give an example of a tetracycline
doxycycline
Give an example of an aminoglycoside
gentamicin
streptomycin
What groups of antibiotics inhibit nucleic acid synthesis?
trimethoprim (inhibits folate)
sulphonadmides
fluroquinolones
rifampicin
metronidazole
Give an example of a sulphonamide
sulphamethoxazole (inhibits folate synthesis)
Give an example of a fluroquinolone
ciprofloxacin (inhibits DNA gyrase)
What is the action of rifampicin?
binds to DNA polymerase
What is the action of metronidazole?
DNA strand breaks
What group of people should you never give trimethoprim to?
pregnant women
Name three antibiotic resistance mechanisms
beta-lactamase producing bacteria (resistant to penicillin derived antibiotics)
MRSA - mecA gene - unique transpeptidase not inhibited by B-lactam abx
efflux pump resistance mechanism
What are the symptoms of TB?
night sweats, cough, haemoptysis, weight loss, malaise
What is the treatment for TB?
isoniazid
rifampicin
ethambutamol
pyrazinamide
What test is used for TB?
histology with Ziehl-Neelson stain
What test is used for TB?
histology with Ziehl-Neelsen stain
What is the process of the Ziehl-Neelsen stain?
heat sample with carbol fuchsin dye
(heat makes it resistant to decolourisation with acid)
acid wash
methylene blue counterstain
Give an example of an anti fungal drug
clotrimazole (-azole)
Give an example of fungal infections
candida albicans (vaginal/oral infections, catheter/line infections
aspergillus fumigatus (lung infections)
What test is used to confirm active HBV infection?
HBsAg test - positive will mean active infection
Which cells does HIV effect?
CD4+
What are the symptoms of HIV?
non-specific malaise, recurrent infection
Give an example of a pathogenic protozoa
malaria, giardia lambia, toxiplasmosis
What does malaria effect?
liver and RBCs
What are the symptoms of malaria?
fever, chills, sweats, headaches, myalgia
What test is done to check for malaria?
Giemsa stained thin and thick blood film
Which is the most common pathogen to cause malaria?
plasmodium falciparum
What two species can cause dormant malaria?
P. ovale and P. vivax
What is the treatment for simple malaria?
hydroxycholoroquine
What is the treatment for complicated malaria?
IV artusenate
What medication can be given for dormant malaria?
primaquine
