Lecture - Antimicrobial Action In Resp Disease

Question 1

Pathogen for community aquired pneumonia

Answer 1

• Strep pneumonia : 15-76%
• H. Influenzae
• Legionella
• Mycoplasma pneumonia
• chlamydophila pneumonia
• viruses
• oral anaerobes
• staph aureus
• Gram neg
• unknown

Question 2

Antibiotic guidelines: community-acquired pneumonia in adults: moderate disease

Answer 2

• benzylpenicillin 1.2g IV, 6 hourly until significant improvement
• then amoxyxillin 1g orally, 8 hourly for a total of 7 days
• plus doxyccline 100 mg orally, 12 hourly for 7 days

Question 3

Community acquired pneumonia in adults: severe disease

Answer 3

• ceftriaxone 1g IV, daily

- plus azithromycin 500 mg IV, daily

Question 4

Typical bacteria

• pathogens
• antibiotic

Answer 4

• strep pneumonia
• H influenza
• narrow specrtrum b lactams first
• if doesnt work: macrolides, tetracyclines, new quinolones

Question 5

Bacteria: atypical

Answer 5

• Mycoplasma pneumonia
• chlamydia pneumonia
• C. Psittaci
• Legionella species
• b lactams ineffective
• macrolides, tetracyclines, or quinolones

Question 6

Anaerobes

• treatment

Answer 6

• penicilin
• metronidazole
• clindamycin

Question 7

Hospital acquired

• pathogens
• treatment

Answer 7

• pseudomonia aeruginosa and other gram neg rods
• MRSA
• treatment: broad spectrum b-lactams +/- aminoglycosides, quinolones, vancomycin, linezolid

Question 8

Causes of chest infiltrates in AIDS patients

Answer 8

• pneumocystis jiroveci (PJP)
• mycobacteria TB, mycobacteria avium
• nocardia
• legionella
• typical bacterial pathogens
• cytomegalovirus

Question 9

Fungi

• pathogens
• treatment

Answer 9

• Dimorphic fungi, Aspergillus, C. Neoformans
• Treatment: amphotericin B, triazoles, echinocandins
• Pneumocystis jiroveci
• Treatment: sulphonamides + DHFR inhibitors, pentamidine, atovaquone

Question 10

Viruses

Answer 10

• influenza

- Treatment: neuraminidase inhibitor (Oseltamivir)

Question 11

S pneumonia infection: presentation

Answer 11

• sudden onset
• productive cough
• Fever, chills, pleuritic pain
• Gram stain highly specific

Question 12

M pneumonia
C pneumonia

Presentation

Answer 12

• Prodrome 4-5 days
• Non purulent cough
• URT symptom
• Extra thoracic symptome

Question 13

Effective antibiotic use

Answer 13

• active against bacteria likely to be at the site of infection (eg: S pneumonia/lung)
• Good penetration and concentration at site of infection
• stay at high level for long enough to eradicate the bacteria (Time>MIC)
• narrowest spectrum for shortest duration
• stop if viral aetiology confirmed and bacterial infection unlikely

Question 14

B-lactams antibiotics

Answer 14

• include penicillins, cephalosporins and carbapenems
• inhibit bacterial cell wall synthesis
• are bactericidal can be given in large doses
• are not concentrated in cells
• may be slowly or rapidly excreted
• are destroyed by bacterial b-lactamases

Question 15

Bacterial resistance mechanisms

Answer 15

• entry or active efflux
• modified target
• inactivating enzymes - b-lactamase
• intinsic or acquired
• chromosomal or plasmid

Question 16

Minimum inhibitory concentration

Answer 16

• the lowest concentration in a dilution series of set antibiotic that completely prevents growth of the organism
• antibiotic needs to be 40% of the time above the MIC
• breakpoint concentration
• think about where the pathogen has infected as well

Question 17

S pneumonia b-lactam resistance

Answer 17

• incremental
• Rising MIC
• follows multiple mutations in PBP genes
• altered binding affinity for penicillins and cephalosporins

Question 18

H influenzae b-lactam resistance

Answer 18

• Frequencu of the TEM-1 b-lactamase: hydrolyses penicillin, ampicillin and amoxycillin

Question 19

Mycoplasma and chlamydophlia

Answer 19

• mycoplasmas do not have cell walls and are therefore not destroyed by b-lactams
• chlamydia are obligate intracellular bacteria, incapable of synthesizing aTP
• they multiply in the phagosomes of phagocytic cells
• this is an all or nothing resistance

Question 20

Fluoroquinolones

Answer 20

• Norfloxacin: renal tract infections
• Ciprofloxacin: gram - sepsis, including pseudomonas aeruginosa and legionella
• Moxifloxacin: respiratory quinolones: spectrum includes pneumococci

Question 21

Aminoglycosides

Answer 21

• Gentamicin, tobramycin, Amikacin
• excreted only by glomerular filtration and accumulate if renal function is poor
• no activity against stric anaerobes
• most useful for aerobic Gram neg
• inherently nephro and neurotoxic
• synergistic in combination with b-lactams

Question 22

Systemic antifungal agents

Answer 22

• ergosterol plasma membrane integrity
• polyenes: amphotericin B
• ERgosterol biosynthesis inhibitors: Azoles
• GLucan synthesis inhibitors: Echinocandins

Question 23

Drug development and antibiotic resistance

Answer 23

• drug evaluation defines the spectrum of activity
• laboratory tests estimate the likelihood of resistance develop
• emergence of resistance will only become apparent with clinical use
• the degree and rate will depend on level of use

Question 24

Bacterial antibiotic resistance

Answer 24

• the driving force of antibiptic resistance is widespread antibiotic use
• 40-50% of acute care inpatients receive antibiotics as treatment or prophylaxis
• many studies show excessive and inappropriate medical prescribing