Microbiology

Question 1

what is a commensal pathogen

Answer 1

colonises host but doesnt normally cause disease

Question 2

what is an opportunist pathogen

Answer 2

only causes disease if host defense is compromised

Question 3

bacteria nomenclature

Answer 3

genus, species

Question 4

what is virulence

Answer 4

pathogenicity; degree of which an organism is pathogenic

Question 5

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

Answer 5

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

Question 6

give 2 examples of gram positve bacilli

Answer 6

c difficile, listeria

Question 7

give 2 examples of gram negative cocci

Answer 7

n. meningitidis
n. ghonorhea

Question 8

cocci can be classified into…

Answer 8

chained, clustered (streptococci, staphylococci)

Question 9

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

Answer 9

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

Question 10

streptococci, alpha, optochins test. results

Answer 10

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

Question 11

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

Answer 11

strey pyogens- tonisilitis
first line is penicilin

Question 12

of the cocci, which group is catalase positive and negative

Answer 12

strep- catalase negative
staph- caltalse positivecl

Question 13

clustered purple cocci- what test and results

Answer 13

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

Question 14

explain gram negative bacteria classificiation

Answer 14

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

Question 15

how to diffeentiate between shigella and salmonella

Answer 15

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

Question 16

order of staining, what will gram positives and negative retain

Answer 16

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

Question 17

what is blood agar made of

Answer 17

sheep + horse blood

Question 18

what is chocolate agar and whats it used for

Answer 18

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

Question 19

what is cled agar used for

Answer 19

e.coli

Question 20

what is sabourald agar for

Answer 20

fungus

Question 21

sterile sites of body

Answer 21

blood
csf
pleural fluid
peritoneum
joints
urinary tract
lower rep tract

Question 22

example of mycobacteria

Answer 22

tb, leprosy

Question 23

is mycobacteria slow or fast growing

Answer 23

slow so gradual onset of disease

Question 24

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

Answer 24

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

Question 25

how can a virus cause disease

Answer 25

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

Question 26

how do you detect a virus

Answer 26

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

Question 27

what type of bacteria is Neisseria meningitis

Answer 27

diplococci gram negative

Question 28

headaches and neck stiffness indicate what diseasse

Answer 28

meningitis

Question 29

example of protazoa and which is the most serious

Answer 29

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

Question 30

treatment for malaria

Answer 30

iv artesunate

Question 31

what are the 2 forms of fungi

Answer 31

yeast (single cell), mould (multicellular)

Question 32

what are the diagnostic swabs for viral infection

Answer 32

green viral swab- virus black charcoal swab- bacterial

Question 33

describe pcr and benefits of it

Answer 33

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

Question 34

what virus causes shingles

Answer 34

varicella zoster virus- VZV

Question 35

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

Answer 35

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

Question 36

how does epstein barr virus present

Answer 36

myalgia, tiredness sore throat enlarged spleen!!

Question 37

what is the virus behind infective mononucleosis

Answer 37

epstein barr virus

Question 38

histological appearance of CMV

Answer 38

owl eye bodies

Question 39

what are the main AIDS defining illnesses

Answer 39

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

Question 40

what is antibiotic

Answer 40

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

Question 41

is mrsa gram positive or negative

Answer 41

gram positive

Question 42

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

Answer 42

inhibit cell wall synthesis PENECILIN carbapenem Cephalosporins

Question 43

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

Answer 43

a macroclide- clarithromycin/ erythromycin - inhibit protein synthesis

Question 44

what bacteria will be resistant to penicilin derived antibiotics

Answer 44

bacteria that produce beta lactamase

Question 45

why is mrsa resistant

Answer 45

carries gene which insit inhibited by beta lacatam antibiotics

Question 46

what antigen is a hiv marker

Answer 46

p24

Question 47

prevention of hiv

Answer 47

prep- pre exposure prophylaxis pep- post exposure prophylaxis

Question 48

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

Answer 48

no