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2a systems > Microbiology > Flashcards

Microbiology Flashcards

1
Q

what is a commensal pathogen

A

colonises host but doesnt normally cause disease

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2
Q

what is an opportunist pathogen

A

only causes disease if host defense is compromised

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3
Q

bacteria nomenclature

A

genus, species

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4
Q

what is virulence

A

pathogenicity; degree of which an organism is pathogenic

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5
Q

difference between gram positive and negative bacteria- membrane, wall, endo/exo toxin, stain , what tlr detects negative

A

positive:
- single membrane
- thick peptidoglycan wall
- exotoxin only
- stains purple
mainly cocci

negative:
- double membrane
- thin peptidoglycan wall
- exotoxin and endotoxin
- stains pink
- mainly bacilli
- detected by tlr 4

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6
Q

give 2 examples of gram positve bacilli

A

c difficile, listeria

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7
Q

give 2 examples of gram negative cocci

A

n. meningitidis
n. ghonorhea

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8
Q

cocci can be classified into…

A

chained, clustered (streptococci, staphylococci)

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9
Q

if you have chained purple cocci, whats the next test youd do + further tests

A

look at haemolysis on blood agar
if it goes green, its alpha do optochins test to see if its virdians (resistant) or s.pneumoniae (sensetive)
if its clear, its beta- lancefield antigenic group

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10
Q

streptococci, alpha, optochins test. results

A

resistant= viridans strep- poor dental hygeine
sensetive- s. pnuemoniae

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11
Q

streptococci- beta- lancefield. what is strep a + treatment

A

strey pyogens- tonisilitis
first line is penicilin

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12
Q

of the cocci, which group is catalase positive and negative

A

strep- catalase negative
staph- caltalse positivecl

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13
Q

clustered purple cocci- what test and results

A

staphlococci- coagulase test
positive= s.aureus (gold colonies)
negative- epidermidis

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14
Q

explain gram negative bacteria classificiation

A

look at appearance on macConkey agar to see lactose status
pink= lactose fermenting= probs e.coli (gram negative rod)
white= non-lactose fermenting—oxidase test
positive oxidase= psudonomal, negative is shigella or salmonella

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15
Q

how to diffeentiate between shigella and salmonella

A

XLD agar- salmonella will be red with black center and shigella is red only

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16
Q

order of staining, what will gram positives and negative retain

A

crystal violet
iodine
acetate/ alcohol
safrain counterstain
positive will retain crustal violet- purple
negative will decolorise and hold safrain - pink

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17
Q

what is blood agar made of

A

sheep + horse blood

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18
Q

what is chocolate agar and whats it used for

A

cooked ba for 5 mins at 80 degrees- fastidious organisms like h.influenzae

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19
Q

what is cled agar used for

A

e.coli

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20
Q

what is sabourald agar for

A

fungus

21
Q

sterile sites of body

A

blood
csf
pleural fluid
peritoneum
joints
urinary tract
lower rep tract

22
Q

example of mycobacteria

A

tb, leprosy

23
Q

is mycobacteria slow or fast growing

A

slow so gradual onset of disease

24
Q

what stain is usedd for mycobacteria like tb and what colour will they stain

A

ziehl neelson- all mycobacteria will stain red bc theyre acid fast

25
Q

how can a virus cause disease

A

direct destruction of host cell
modification
over reactivity of immune system
cell proliferation
evasion of host defense

26
Q

how do you detect a virus

A

PCR or electron microscopy and nucleic acid amplification test (NAAT)

27
Q

what type of bacteria is Neisseria meningitis

A

diplococci gram negative

28
Q

headaches and neck stiffness indicate what diseasse

A

meningitis

29
Q

example of protazoa and which is the most serious

A

malaria falciparum from a female mosquitoe- fever from someone returning from travels!

30
Q

treatment for malaria

A

iv artesunate

31
Q

what are the 2 forms of fungi

A

yeast (single cell), mould (multicellular)

32
Q

what are the diagnostic swabs for viral infection

A

green viral swab- virus
black charcoal swab- bacterial

33
Q

describe pcr and benefits of it

A

need to suspect a virus beforehand but can test for multiple viruses simultaneously using a mix of primers
very sensetive and quick (24hrs) and cheap

34
Q

what virus causes shingles

A

varicella zoster virus- VZV

35
Q

how would you identify epstein barr virus which leads to infective mononucleosis

A

s pyogens presents int the same way as IM- white/yellow puss over tonsils so to exclude this we do a black charcoal swab
then blood test- fbc- atypical lymphocytes on blood film(basophillic with prominent nucleolus) and serology test for EBV igs
pcr for next day

36
Q

how does epstein barr virus present

A

myalgia, tiredness
sore throat
enlarged spleen!!

37
Q

what is the virus behind infective mononucleosis

A

epstein barr virus

38
Q

histological appearance of CMV

A

owl eye bodies

39
Q

what are the main AIDS defining illnesses

A

Pneumocystis pneumonia!!!!!!!!!!!!!
CMV collitis
oral candida (thrush)
lymphoma

40
Q

what is antibiotic

A

produced by microorganisms and kill or inhibit the growth of other microorganisms

41
Q

is mrsa gram positive or negative

A

gram positive

42
Q

what do beta lactams do and what are the 3 main groups

A

inhibit cell wall synthesis
PENECILIN
carbapenem
Cephalosporins

43
Q

if someone has a penicilin allergy what would you give them next and what do these do

A

a macroclide- clarithromycin/ erythromycin - inhibit protein synthesis

44
Q

what bacteria will be resistant to penicilin derived antibiotics

A

bacteria that produce beta lactamase

45
Q

why is mrsa resistant

A

carries gene which insit inhibited by beta lacatam antibiotics

46
Q

what antigen is a hiv marker

A

p24

47
Q

prevention of hiv

A

prep- pre exposure prophylaxis
pep- post exposure prophylaxis

48
Q

if you have an undetectable viral load for hiv can it be transmitted

A

no

49
Q
A

2a systems (7 decks)

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