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Chemical Pathology > Microbiology > Flashcards

Microbiology Flashcards

1
Q

Name 2 antibiotics that interfere with folic acid metabolism

A

. Trimethoprim
• sulfonamides

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2
Q

Name 2 antibiotics that interfere with cell wall synthesis

A

• Beta lactaMs
• glycopeptides
Also: lysozyme, cycloserine, bacitracin

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3
Q

Name 5 types beta lactaMs

A

• Penicillin
• beta lactam - beta/ lactamase inhibitor combinations
• cephalosporins
• carbapenems
• monobactams

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4
Q

Name 5 types penicillins with examples

A

• Natural penicillins: penicillin g, vk (narrow spectrum, primarily G +)
• beta lactamase resistant: methicillin, oxacillin, cloxacillin (staphylococci)
• amino penicillins semi synthetic: ampicillin, amoxicillin (broad spectrum)
• carboxy penicillins
• ureido penicillins: carbenicillin, piperacillin (pseudomonas)

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5
Q

How are bacteria resistant to penicillins? (2)

A

Enzymatic degradation
• G +: penicillinases
• G - : beta lactamases (tem-1 /shV-1)

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6
Q

Name 4 beta-lactam-beta /lactamase inhibitor combinations

A

• Augmentin: co- amoxicillin - clavulanic acid!
. PiperaCillin: tazobactam !
• ticarcillin: clavulanic
• ampicillin: sulbactam

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7
Q

Name 3 second generation cefalosporins

A

• Cefoxitin!
• cefuroxime
• cefamandole

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8
Q

Which antibiotics have the broadest antimicrobial spectrum and are beta lactamase stable

A

CarbapenemS

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9
Q

Name 2 glycopeptides antibiotics and moa

A

• Vancomycin
• teicoplanin
- Interfere with cell wall synthesis by binding to terminal d-ala-d-ala (only G + bc large molecules that they can’t penetrate )

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10
Q

Name a side effect of glycopepticles

A

Nephrotoxic

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11
Q

Which antibiotics are cell membrane inhibitors and what is their spectrum of activity

A

Polymyxin’s
Used as last resort for multi drug resistant bacteria (neuro and nephrotoxic): acinetobacter baumanii, pseudomonas aeruginosa, carbapenemase producing enterobacteriaçae (cre)
Nb no gram positive or anaerobic cover

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12
Q

Name 2 inhibitors of folate (nucleic acid) synthesis and use

A

• Sulfonamides: sulfamethoxazole (bacteriostatic, )
• trimethoprim
( usually used together for UTI, pneumocystis pneumonia, drug prophylax in HIV)

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13
Q

Name 3 side effects sulfonamides

A

• Fever, rashes! Photosensitive, bone narrow suppress
• Steven Johnson syndrome!,erythema multiforme
• toxic epidermal necrolysis

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14
Q

Name 2 antibiotic inhibitors of DNA (nucleic acid) synthesis

A

• Quinolones:
-1st gen- nalidixic acid (G-)
-2nd gen - fluoro quinolones: ciprofloxacin (G-, g+, excellent pseudomonas)
-3rd gen - levo floxacin
-4th gen: trovafloxaCin
• metronidazole

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15
Q

Name antibiotic inhibitors of m RNA (nucleic acid) synthesis

A

Rifampicin

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16
Q

Name 3 contraindications and side effects fluoroquinolones

A

Contraindications
• pregnancy
• children - damage growing bone and cartilage

Side effects
• tendinitis and tendon rupture in > 60 and corticosteroid use

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17
Q

Name 7 antibiotic inhibitors of protein synthesis with examples

A

• Aminoglycosides: gentamicin, neomycin, streptomycin (bactericide , prevent formation initiation complex) (g+, g-, pseudomonas)
• tetracyclines: doxycycline (bacteriostatic, block attach of charged amino acyl t rna to the A site on ribosome s.30) (mycoplasma, chlamydia, rickettsiae)
• chloramphenicol (bacteriostatic, bind to ribosome 50S to inhibit peptide transfer) (broad spec, good CSF penetration, reserved for severe haemophilus influenza bc bm suppression)
• Macrolide’s: ace azithro, clarithro, erythromycin (bacteriostatic, bind to ribosome 50s to prevent translocation) (broad spec, pseudomonas, but may aerobic G- enterobac resistant)
• lincosamides: clindamycin (bacteriostatic, ribosome 50s) ( g+ cocci, anaerobes!)
. Oxazolidinone’s: linezolid (bacterio static, 50s) (mrsa and other resistant enterococci and pneumococci)
• streptogramins: quinupristin-dalfopristin ( vancomycin resistant enterococci)

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18
Q

Name 2 side effects aminoglycosides

A

• Ototoxic
• nephrotoxic

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19
Q

Name 4 contraindications and side effects tetracyclines

A

Eg doxycycline

Contraindications,
• pregnancy
• children < 8: yellow staining developing teeth, effect bone development

Side effects
• suppress gut -flora: git upset
• resistance transmitted easily: superinfections

20
Q

Which 3 antibiotics that inhibit protein synthesis share overlapping binding sites and why is this important

A

Macrolide’s (ace), lincosamides (clindamycin) and streptogramins (quinupristin - dalfopristin) bind to subunit 50S
Therefore if resistance to one group, resistance to all groups

Aerobic g- (esp enterobacteria) are intrinsically resistant to macrolides
Lincosamides may cause antibiotic associated pseudomenbranous colitis by removing normal anaerobic bowel flora, allowing C diff procreation

21
Q

Describe the components of the chain of infection (6)

A

Infectious agents: bacteria prions etc →
Reservoir: people, water food →
Portal of exits: blood, secretions etc →
Mode of transmission: physical contacts, droplets, airborne (try to stop here usually)
Portal of entry: mucous membrane, broken skin etc →
Susceptible host: immune deficiency, diabetes, burns, surgery, age →.

22
Q

Name 5 Tb tests

A

• Tb microscopy eg auramine fluorescence microscopy
• X pert mtb/rif and Xpert mtb/ rif ultra (real time pcr) (mycobacterium tuberculosis bacilli From sputum,identify rifampicin resistance, < 2 hours )
• line probe assay (genotype mtbdrplus [ ID MTB complex and detect rifampicin and isoniazid resistance ] + genotype mtbdrs/ [also detect fluoroquinolone and second line injectable drug resistances ] by HAIN life sciences)
• X pert xdr cartridge
• liquid culture (take 15 -42 days)

23
Q

Name 2 limitations Gene X pert mtb/rif and Xpert mtb/ rif ultra

A

•Low specificity (false negatives)
• can’t determine response to treatment

24
Q

Approach to Tb GXP positive and rifampicin sensitive? (2)

A

• Treat as tb, start on regimen 1 ripe
• send one specimen for microscopy

25
Q

Approach to Tb suspect with GXP positive and rifampicin resistant? (2)

A

• Treat as mdr-tb and refer to unit
• collect one specimen for culture and DST for rifampiCIN, isoniazid, fluoroqunolone, aminoglycoside

26
Q

Approach to Tb suspect with GXP positive and rifampicin unsuccessful? (2)

A

• Treat as tb: start on regimen 1
• collect one specimen for microscopy and LPA (line probe assay)

27
Q

Approach to Tb suspect with GXP negative? (8)

A

• Do HIV test!

If HIV positive,
. collect one specimen for culture and LPA or DST (for r and H )
• chest xray
• treat with antibiotics and review after 5 days
-if poor response to antibiotics or clinically Tb on Cxr, treat as Tb and start on regimen 1 ,
-if LPA / DST results show resistant to r and h or r only, treat as mdr-tb and refer to unit

If HIV negative, treat with antibiotics
• good response: no further follow up, advise to returnwhen symptoms recur
• poor response: consider other diagnosis and refer

28
Q

Approach to Tb suspect with GXP unsuccessful?

A

Repeat

29
Q

Approach to Tb suspect with X pert ultra “mtb trace detected”? (3)

A

• Clinical assessment and collect sputum for Tb culture and DST
. If asymptomatic or clinical findings don’t suggest tb, follow up culture and DST results
. If clinical presentation consistent with tb, commence ds -tb treatment and follow up

30
Q

Approach to positive Tb fluorescence microscopy smear?

A

Do line probe assay

31
Q

Approach to negative Tb fluorescence microscopy smear?

A

Do culture

32
Q

Approach to positive Tb culture?

A

Do ziehl Nielsen microscopy
- if cords, mtbdr plus
- if no cords, Cm

33
Q

Type specimen needed for anaerobic cultures?

A

Tissue and fluids
Swabs not acceptable

34
Q

What is anal sellotape used for

A

Enterobius threadworms

35
Q

Which 2 genes cause isoniazid resistance

A
  • Kat G
  • inhA

(Also fab G1, oxyr-ahpc intergenic region)
Detected in mtbdr plus line probe assay

36
Q

What gene detects rifampicin resistance

A

81bp rpoB gene

37
Q

What is line probe assay

A
  • Molecular assay based on DNA amplification and reverse hybridisation
  • ID MTB complex and rifampicin and isoniazid resistance
  • MTBDR plus assay
38
Q

Name 3 macrolides and moa

A
  • Erythromycin
  • azithromycin
  • clarithromycin
    (Ace)

Broad spectrum but many G - resistant
Bind to 505 bacterial ribosomal unit to prevent translocation
Bacteriostatic

39
Q

What caused acquired resistance to macrolides?

A

Loss of binding affinity caused by plasmid-mediated methylation of 23S rRNA

40
Q

Name 2 lincosamides and moa

A
  • Clindamycin
  • lincomycin

Broad spec, esp anaerobes!

Ae = antibiotic associated pseudo-membranous colitis ( C diff )

41
Q

Name a streptogramin and moa

A

Quinupristin - dalfopristin

Act synergistically against g+
Disrupt translation mRNA into protein
Mainly to treat vancomycin resistant enterococci

42
Q

Name antibiotic susceptibility testing methods (5)

A
  • Kirby - Bauer disc diffusion method (qualitative)
  • broth microdilution (quantitative) ( test tubes)
  • Gradient diffusion e test (quantitative) (strip)
  • automated methods: vital, phoenix, microscan
  • molecular methods: Gene expert, mtbdr plus LPA, gene sequencing
43
Q

How report antibiotic susceptibility testing results? (4)

A
  • Categorical reporting (intermediate/ sensitive/ resistant)
  • MIC data
  • cascade reporting (based on principle of antimicrobial stewardship)
  • antibiograms
44
Q

Name 7 high risk microbiology specimens

A
  • Blood borne virus infection or carrier: hepatitis b/c, HIV /AIDS
  • Tb
  • brucellosis
  • typhoid / paratyphoid
  • prion disease
  • e coli 0157
  • viral haemorrhagic fivers
45
Q

How transport high risk microbiology specimens (4)

A
  • Label container properly
  • biohazard plastic bag
  • laboratory request form
  • transport immediately and inform lab

Chemical Pathology (23 decks)

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