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Clinical Pathology > Advanced Microbiology > Flashcards

Advanced Microbiology Flashcards

1
Q

investigation for meningitis

A

lumbar puncture
blood cultures x2
blood for bacterial PCR - S.pneumoniae and N.meningitidis

Immunosuppressed: cryptococcal antigen, TB culture/ PCR

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2
Q

investigation for encephalitis

A

CSF viral PCR

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3
Q

investigation for brain abscess

A

local sampling of pus
gram, culture, sensitivity
blood cultures

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4
Q

investigation for acute otitis media

A

clinical diagnosis
viral and bacterial
send pus if ear drum perforated

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5
Q

investigation for acute otitis externa

A

ear swab

determine cause and sensitivity

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6
Q

investigation for rhino-sinusitis

A

majority viral
2nd bacterial infection
severe cases: pus from operative sinus lavage
FBC, blood cultures

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7
Q

investigation for pharyngitis

A

most viral
throat swabs if evidence of bacterial infection
B-haem-strep
EVB serology, diptheria swab, pus if quinsy abscess

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8
Q

investigation for influenza

A

test those who may require treatment

PCR has sens>90% and spec >99%

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9
Q

investigation for pneumonia

A

CURB65
0-1 no investigations
2-5 - sputum, blood cultures, atypical screen

atypical screen: legionella antigen, nose/throat for mycoplasma PCR, might include serum

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10
Q

investigation for TB

A

exposure testing: mantoux, IGRA, rely on intact immune system

Pulmonary symptoms: 3 sputum samples
microscopy and culture
PCR - rapid, costly, lower sensitivity

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11
Q

investigation for atypical infections

A

PCR for viral/ pneumocytosis

cultures for fungal e.g. aspergillus

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12
Q

investigation for localised skin infection

A

blister fluid/ abscess puss
needle aspirates from cellulitis
blood cultures - send if sepsis

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13
Q

investigation for necrotising fasciitis

A

debrided tissue - pus
2 sets blood cultures
bloods - FBC, U&Es, LFTs, CRP

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14
Q

investigation for diabetic foot

A

mild infection: wound swabs

mod/severe infection - debride wound then clean bone/ tissue sample

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15
Q

investigation for cystitis/ pyelonephritis

A

urine sample: WBC, RBC, epithelial cells, bacterial growth, sensitivities

Kass criteria: significant bacteruria

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16
Q

investigation for prostatitis

A

urinalysis

post prostatic massage

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17
Q

investigation for epididymo-orchiditis

A

either enteric/UTI or STI
urine sent for cultures
urine - chylamydia and gonorrhoea

severe: bloods, blood cultures, USS +/- drainage

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18
Q

investigation for infectious diarrhoea

A 
lab guiding with clinical details 
stool sample x3 for parasites 
bloods: FBC, clotting, U&Es, LFTs, CRP
blood cultures
abdominal imaging
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19
Q

investigation for H. pylori

A 
H. pylori antibody test 
H. Pylori stool antigen 
urea breath test - gold standard for test of sure 
biopsy urease test 
stop PPIs before testing
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20
Q

investigation for liver abscess

A

pyogenic (bacterial), hyatid or amoebic

pus if safe to frain 
stool for OCP 
blood cultures
FBC, U&Es, LFTs CRP
hydatid serology 
USS/CT
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21
Q

investigation for cholangitis/ cholecystitis

A

FBC, U&E, LFT, blood cultures, clotting, amylase, USS/CT, bile fluid/ pus

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22
Q

investigation for diverticulitis

A

pus
blood cultures
FBC, U&E, LFT, clotting, amylase, CT

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23
Q

investigation for endocarditis

A

blood cultures
3 sets taken at different times during first 24 hrs
echocardiography - trans-thoracic echo, trans-oesophageal echo (done for suspected PVE)
FBC, CRP, U&E, LFTs
bartonella, chylamydia, coxiella, brucella serology
valve tissue if valve replaced

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24
Q

investigation for vascular graft infection

A

3 sets blood cultures in 1st 24 hrs
CT, PET, WBC scan - fluid around graft, fistulae
tissue/fluid from around the graft for culture or PCR

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25
Q

investigation for viral hepatitis

A

serology +/- PCR
antigen and antibody detection
PCR detects DNA or RNA from living/dead organisms
suggests active infection

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26
Q

investigation for syphilis

A

PCR

serology - IgM in primary infection, treponemal specific antibody, non-treponemal specific antibody

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27
Q

bacterial cell wall inhibitors

A

B-lactams

glycopeptides

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28
Q

antifungal cell wall inhibitors

A

echinocandins

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29
Q

structure of B-lactams

A

CCCN ring structure

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30
Q

B-lactam mechanism of action

A

interfere with function of penicillin binding proteins - transpeptidase enzymes involved in peptidoglycan cross-linking

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31
Q

first true antibiotic in clinical practice

A

benzyl penicillin

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32
Q

B-lactam antibiotics

A

penicillins
Cephalosporins
Carbapenems
Monobactams

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33
Q

examples of penicillins

A

benzylpenicillin, amoxicillin, flucloxacillin - narrow spectrum

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34
Q

examples of cephalosporins

A

cefuroxime, ceftadime

  • broad specrum
  • arranged into generations
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35
Q

examples of carbapenems

A

meropenem, imipenem

- extremely broad spectrum

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36
Q

examples of monobactams

A

aztreonam

- gram-negative activity only

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37
Q

common mechanism of resistance to b-lactams

A

B-lactamase enzymes

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38
Q

which b-lactams are staphylococcal b-lactamase resistant to

A

some penicillins only

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39
Q

which b-lactams are extended spectrum b-lactamase resistant to

A

penicillins and cephalosporins

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40
Q

which b-lactams are carbapenemases resistant to

A

carbapenems

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41
Q

what are BLBLI

A

b-lactam/b-lactamase inhibitor combinations

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42
Q

what is co-amoxiclav

A

amoxicillin and clavulanic acid

gram -ve, anaerobes

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43
Q

what is tazocin

A

piperacillin-tazobactam
anti-pseudomonal, staph, strep, enterococci, anaerobes, pseudomonas, gram -ve
greatly increase spectrum = risk of c.diff

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44
Q

mechanism of action of glycopeptides

A

large molecules bind directly to terminal D-ananyl-D-alanine on NAM pentapeptides
inhibit linking of transpeptidases and thus peptoglycan cross linking

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45
Q

what bacteria do glycopeptides target

A

gram +ve

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46
Q

examples of glycopeptides

A

vancomycin, teicoplanin

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47
Q

different protein synthesis inhibitors

A

aminoglycosides
macrolides, lincosamides
tetracyclines
oxazolidones

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48
Q

examples of aminoglycosides

A

gentamicin, amikacin

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49
Q

mechanism of action of aminoglycosides

A

bind to 30S subunit

50
Q

examples of macrolides

A

erythromycin, clarythromicin

51
Q

example and mechanism of action of a Lincosamide

A

clindamycin
bind to 50S subunit
inhibit protein elongation

52
Q

mechanism of action of tetracycline

A

bind to 30S subunit

inhibit translation by interfering with binding tRNA to rRNA

53
Q

examples of tetracyclines

A

tetracycline, doxycycline, tigecycline - modern derivative with a similar mechanism of action and much broader spectrum

54
Q

mechanism of action of oxalidinones and example

A

linezolid
inhibits initiation of protein synthesis
binds to 50S ribosomal subunit
inhibits assembly of initiation complex

55
Q

mechanism of action of echinocandins (antifungal)

A

inhibition of B-1,3-glucan synthase

construction of severly abnormal cell wall

56
Q

examples of echinocandins

A

anidulafungin
caspofungin
micafungin

57
Q

examples of DNA synthesis inhibitors

A

trimethoprim and sulfonamides

58
Q

mechanism of action of DNA synthesis inhibitors

A

inhibit folate sythesis
trimethoprim - dihydropteroate synthetase
sulfonamides - dihydropteroate synthesis

59
Q

mechanism of action of quinolones and fluoroquinolones

A

inhibit one or more of two related bacterial enxymes
- DNA gyrase and topoisomerase IV
which is involved in remodelling DNA in DNA replication

60
Q

examples of quinolones

A

nalidixic acid, ciprofloxacin, levofloxacin

61
Q

mechanism of RNA synthesis inhibitors

A

RNA polymerase inhibitor

prevents synthesis of mRNA

62
Q

examples of RNA synthesis inhibitors

A

Rifampicin

63
Q

mechanism of action of Terbafine

A

inhibit synthesis of ergosteroll

64
Q

mechanism of action of amphotericin B

A

bind to ergesterol and cause physical damage to the membrane

65
Q

virus syndromes that cause non-vesicular rashes

A 
measles 
rubella 
parvovirus 
adenovirus 
HHV6
66
Q

virus syndromes - vesicular rashes

A

chicken pox
herpes simplex
enterovirus

67
Q

when would you use antivirals

A 
acute infections in general population
- primary HSV and HS encephalitis 
- chickenpox in adolescents and adults 
- shingles in eye 
- elderly 
chronic infections
infections in immunocompromised
68
Q

mechanism of action of nucleoside reverse transcriptase inhibitors

A

inhibit reverse transcriptase

69
Q

NRTIs used in HIV

A

azidothymine
thymine analogues - zidovudine
cytosine analogues - lamivudine
purine analogues - abacavir, tenofovir

70
Q

NNRTIs

A

efavirenz

neviparine

71
Q

what is HAART

A

highly active antiviral therapy
2NRTIs + NNTRI
2NRTIs + boosted PI (protease inhibitor)
boosted when CD4 count falls

72
Q

indications for aciclovir

A

HSV, VZV

73
Q

mechanism of action of aciclovir

A

inhibit herpes DNA polymerase

74
Q

administration of aciclovir

A

topically, IV, orally

75
Q

what is valacyclovir

A

prodrug converted to acyclovir - prevents CMV following organ transplantation

76
Q

indication for osteltamivir

A

Influenza A or B

77
Q

mechanism of action of osteltamivir

A

neuramidase enzyme cleaves sialic acid on glycoproteins allowing virions to exit

78
Q

treatment for CMV

A

ganciclovir

79
Q

indication for ribavirin

A

RSV, HCV, HEV

80
Q

leucocyte esterase meaning

A

enzyme produced by neutrophils
WBCs anywhere in GU tract
+ve - chylamydia, urethritis, TB, bladder tumours, viral infections, nephroliasis, foreign bodies and corticosteroid use

81
Q

nitrites meaning

A

some bacteria nitrates>nitrities
+ve means infection
some organisms do not reduce nitrates

82
Q

Urine dip RBC

A

peroxidase activity of erythrocytes

high doses of Vit C can produce false negative

83
Q

bacterial pathogens of lower UTI

A

enterobacteriaciae - GI organisms - E.coli, proteus, klebsiella
Enterococci - GI organisms
Staphylococci - S.aureus
streptococci - aHS, bHS

84
Q

common antibiotics for lower UTI

A 
Trimethoprim 
Nitrofurantoin 
Amoxicillin 
(piv)mecillinam fosfomycin
cephalosporins, cirpfloxacin
85
Q

nitrofurantoin

A

therapeutic levels only achieved in urine
treatment of simple, uncomplicated UTI
can be given in pregnancy

86
Q

(piv)mecillinam

A

oral pro-drug of mecillinam
relatively stable to bacterial beta-lactamases, including ESBLs
active against range of coliform organisms
pseudomonas not susceptible
no Gram +ve activity e.g. enterococci
lower UTI

87
Q

antibiotics suitable for upper UTI due to E.coli

A 
cefuroxime 
azteronam - used in case
piperacillin-taxobactam 
ciprofloxacin 
gentamicin
88
Q

innate resistance mechanism

A

fundamental property of the bacterium/antibiotic combination

89
Q

what antibiotics are gram-negatives resistant to?

A

glycopeptides, daptomycin

90
Q

what antibiotics are gram-positives resistant to?

A

aztreonam, colistin

91
Q

what antibiotics are anaerobes resistant to?

A

aminoglycosides

92
Q

what antibiotics are streptococci resistant to?

A

aminoglycosides

93
Q

acquired resistance mechanism

A

acquisition of a gene that encodes an antibiotic resistance mechanism

  • new mutation
  • horizontal transfer
94
Q

mechanisms of antibiotic resistance

A
  1. absent target
  2. decreased permeability
  3. target modification
  4. enzymatic degradation
  5. drug efflux
95
Q

absent target examples

A

antibacterial agents/fungi

antiviral agents/bacteria

96
Q

decreased permeability examples

A

Vancomycin: gram -ve bacilli
- gram negatives have outer membrane that is impermeable to vancomycin

Gentamycin: anaerobes
uptake of aminoglycosides requires an O2 dependent AT mechanism

97
Q

target modification examples

A

flucloxacillin: MRSA
- altered penicillin binding protein does not bind B-lactams

Vancomycin: VRE
- altered peptide sequence in gram + peptidoglycan reduces binding of vancomycin

Trimethoprim: Gram -ve bacilli
- mutations in dhr

98
Q

enzymic degradation examples

A

penicillins and cephalosporins: B-lactamses

  • staphylococcal penicillinase
  • extended spectrum B-lactamases
  • carbapenems

Gentamycin: aminoglycoside modifying enzymes

Chloramphenicol: chloramphenicol acetyltransferase (CAT)

99
Q

drug efflux examples

A

multiple antibiotics - Gram -ve

100
Q

development of resistance

A

encoded by single genes
resistance genes in plasmids
- conjugation
- horizontal transfer - transposons and integrons
- vertical transfer - chromosomal or plasmid-borne resistance genes transferred to daughter cells

101
Q

gram positive cocci

A

staph, strep

102
Q

gram neg cocci

A

meningococcus, gonococcus

103
Q

gram positive bacilli

A

cornyebacterium
listeria
clostridium

104
Q

gram negative bacilli

A

enterobactericeae

  • e. coli
  • proteus
  • klebsiella
  • enterobacter
105
Q

what is penicillin G

A

benzylpenicillin iv/im

106
Q

what is penicillin V

A

phenoxymethylpenicillin

107
Q

spectrum of penicillin G and V

A

narrow-spectrum
streptococci - s. pneumoniae, s. pyogenes
many anaerobes
some GNC e.g. N.meningitidis

108
Q

flucloxacillin spectrum

A

broader than pen G
not destroyed by staphylococcal B-lactamase
staphyloccoci
few GNC, anaerobes, streptococci

109
Q

amoxicillin spectrum

A 
as for pen G but broader 
some GNB 
most enterococci 
strep, entero 
destroyed by b-lactamase
110
Q

co-amoxiclav spectrum

A 
broad 
pen G/V e.g. strep 
flucloxacillin e.g. staph 
amoxicillin - most ECOC
many GNB
many anaerobes 
increased c.diff risk
111
Q

tazocin

A

piperacillin-tazobactam

112
Q

tazocin spectrum

A

piperacillin - more GNB than amoxicillin
anti-pseudomonal activity
broad-spectrum
-staph, strep, enterococci, anaerobes, pseudomonas sp. GN organisms

113
Q

marcolides

A

erythromycin, clarithromycin, azithromycin

114
Q

spectrum of macrolides

A

most gram pos
intracellular organisms e.g. mycoplasma, chlamydia, legionella - atypical
limited gram neg

115
Q

glycopeptides

A 
vancomycin, teicoplanin
iv 
gram + 
staph, strep, entero 
non-b-lactam 
vancomycin - renal
116
Q

clindomycin

A 
po/iv
gram + organisms 
staphylococci, streptococci, anaerobes 
anti-toxin action 
good tissue penetration 
associated with Cdiff
117
Q

fluoroquinolones

A

oral/iv
non-b-lactam
associated with CDI
intracellular

118
Q

fluorquinones - ciprofloxacin

A

gram -
anti-pseudomonas
staph, atypicals
poor strep/anaerobe

119
Q

fluorquinones - levofloxacin

A

gram +
strep, atypicals
resp FQ
less GN, pseudomonas

120
Q

aminoglycosides

A 
gentamicin 
gram - bacilli inc pseudomonas 
staph
poor strep 
no anaerobes 
nephro/ototoxicity
121
Q

metronidazole

A

oral/iv
bacteria - anaerobes
parasites - protoza, helminths

122
Q

oral options of MRSA

A

clarithromycin
clindamycin
doxycycline
trimethoprim/co-trimoxazole

Clinical Pathology (8 decks)

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