PATHOGEN-INFECTION-ANTIBIOTIC MATCHING CONSIDERING RESISTANCE - INTERMEDIATE

Question 1

Is it an infection

YES

Answer 1

YES  empirical antibiotics sepsis - ?source - broad-spectrum, rapid, localised - ‘educated guess’ most likely pathogen. Microbiological diagnosis – targeted Rx (de-escalate).

Question 2

NO

Answer 2

no antibiotics

Question 3

NOT SURE

Answer 3

severity?? possible sepsis, BS rapid empirical antibiotics no sepsis, Ix/review

Question 4

Common sites of infection

Answer 4

Urinary tract, Respiratory tract, Skin/soft tissue SSTI, GI tract, CNS, CVS

Question 5

Gram positive organisms

Answer 5

GPC (cocci) – staphylococci, streptococci, GPB (bacilli

Question 6

Gram negative organisms

Answer 6

GNB, GNC eg meningococcus, gonococcus

Question 7

Anaerobes

Answer 7

GN/GP, B/C), Other (eg mycobacteria, viruses,fungi

Question 8

URT flora

Answer 8

mouth flora/upper RT
•	 streptococci, anO2, (GNC, candida, staphylococci)
nasopharynx – colonising flora includes
•	S pneumoniae
•	H influenzae (GNC)
•	M catarrhalis (GNC)
•	GNC, streptococci AND S aureus
Viral
Sore throat/tonsillitis
•	 viral (EBV, RhV etc)
•	 streptococci (GAS), anO2
Sinusitis 
•	S pneumoniae, H influenzae, 
•	M catarrhalis
•	anO2 (chronic sinusitis)

Question 9

LRTI

Answer 9

acute bronchitis – viral/’atypical’
IE COPD – viral, bacterial pneumonia
bacterial pathogens
Strep pneumo, H influenzae (GNC), M catarrhalis (GNC)
‘hospital acquired’ +GNB, S aureus
‘atypicals’ eg mycoplasma, chlamydia, legionella
viruses eg Influenza, para-influenza

Question 10

CNS

Answer 10

sterile site
encephalitis – viral (eg HSV, EV), meningitis
N meninigitis, S pneumoniae, H influenzae, Listeria
Neonates: gpB streptococci, GNB, Listeria
Immunosuppressed: + GNB, Listeria
Post-op: +skin organisms (staphylococci), viral
cerebral abscesses, streptococci, anaerobes
staph, fungal (IVDU, IE)

Question 11

Formulary B antibacterials b-lactams

Answer 11

Penicillins
(benzylpenicillin, phenoxymethylpenicillin, flucloxacillin, amoxicillin, pivmecillinam)
b-lactam/ b-lactamase inhibitor combinations (amoxicillin-clavulanic acid co-amoxiclav, piperacillin-tazobactam tazocin)
Cephalosporins
(cephalexin, cefuroxime, cefotaxime, ceftriaxone, ceftazidime)

Question 12

Formulary B antibacterials - non-b-lactams

Answer 12

aminoglycosides; gentamicin
macrolides; ery/clari/azi thromycin
clindamycin, fosfomycin
glycopeptides; vancomycin, teicoplanin
metronidazole, nitrofurantoin
quinolones; ciprofloxacin and levofloxacin
tetracyclines; doxycycline
trimethoprim

Question 13

Formulary B antimicrobials

Answer 13

Formulary B antimicrobials
Antifungals
•	azoles; clotrimazole, fluconazole, nystatin
Anti-virals: aciclovir and valciclovir
penicillins’
•	low toxicity, bactericidal, allergic reactions
•	cross-reaction with other b-lactams 
–	Cephalosporins
–	Carbapenems
–	(Monobactams)
Flucloxacillin oral/iv	
spectrum 
as for pen G but broader, not destroyed by staphylococcal b-lactamase
staphylococci (not MRSA)
few GNC, many anO2, most streptococci

Question 14

Penicillin G and Penicillin V

Answer 14

Pen G = benzylpenicillin , iv/im
Pen V = phenoxymethylpenicillin, oral
Spectrum: narrow-spectrum
•	streptococci  eg S pneumoniae (pneumococcus)
     	S pyogenes (group A streptococci)
•	many anaerobes
•	some GNC eg Neisseria meningitidis (meningococcus), (N gonorrhoeae ‘gonococcus’)
destroyed by b-lactamases

Question 15

Flucloxacillin oral/iv

Answer 15

spectrum as for pen G but broader, not destroyed by staphylococcal b-lactamase
staphylococci (not MRSA)
few GNC, many anO2, most streptococci

Question 16

Amoxicillin oral/iv

Answer 16

spectrum 
as for pen G but broader
\+ some gram negative bacilli (acquired/intrinsic resistance) + most enterococci (‘streptococci’)
streptococci, enterococci, some GNB
destroyed by b-lactamase

Question 17

Co-amoxiclav

Answer 17

•	Amoxicillin + clavulanic acid
•	CA = inhibitor of b – lactamase
•	broad spectrum:
pen G/V eg streptococci
flucloxacillin – staphylococci (not MRSA)
amoxicillin eg most ECOC
many GNB
many anaerobes
NOT ESBL- producers
Incr. risk of CDI (C difficile infection), allergic reactions

Question 18

Tazocin’

Answer 18

• piperacillin-tazobactam
• piperacillin – more GNB than amoxicillin
• tazobactam – BLI
• anti-pseudomonal activity
• broad-spectrum: staphylococci (not MRSA), most streptococci and enterococci, anaerobes, pseudomonas sp, GN organisms (GNC and GNB)
• not effectively cross BBB
• ESBL

Question 19

Macrolides

Answer 19

erythromycin, clarithromycin, azithromycin
spectrum
• most gram-positive organisms (staph, strep)
• intracellular organisms eg mycoplasma pneumoniae, chlamydia/chlamydophila, legionella sp = ‘atypical’
• limited gram negative

Question 20

Glycopeptides

Answer 20

• vancomycin, teicoplanin- iv *
• gram positive organisms
• staphylococci, streptococci, enterococci
• acquired resistance uncommon
• non-b-lactam
• vancomycin – renal monitoring
• *oral vancomycin CDI

Question 21

Clindamycin

Answer 21

• po/iv
• gram positive organisms, anO2
• staphylococci, streptococci, anaerobes
• variable acquired resistance
• anti-toxin action
• good tissue penetration
• associated with CDI

Question 22

aminoglycosides

Answer 22

• gentamicin: iv, im, (topical)
• gram-negative bacilli, including pseudomonas sp
• staphylococci
• poor streptococcal activity (nb synergy)
• no anO2 activity, monitoring
• nephro and ototoxicity

Question 23

Fluoroquinolones

Answer 23

•	oral/iv
•	good absorption/tissue penetration
•	non b-lactam
•	associated with CDI
•	intracellular activity
ciprofloxacin = early FQ
•	gram negatives, anti-pseudomonas
•	staphylococci, ‘atypicals’
•	 poor streptococcal/anO2 activity,
levofloxacin = later FQ
•	improved gram positive, streptococci, atypicals’,  = ‘respiratory FQ’
•	less GN, pseudomonas,