Lec 5 typical and atypical pathogens

Question 1

Typical pathogens

1) Staph aureus:

G+ve coccus

risk factors and charecteristically

Answer 1

Risk factors:
aspiration
hospital stay
cystic fibrosis
Viral RTI’s

charecteristically:
cavitary with pneumotocele and abscess formation

**MSSA-isoxazolyl penicillins
MRSA- glycopeptides (vancomycin,teicoplanin) and linezolid **

Question 2

2)M.Catarrhalis

oxidase +ve G-ve diplococcus

Infections and treatment

Answer 2

RTI infections:
Sinusitis and otitis media
acute exacerbations of COPD
pneumonia in elderly

treatment: Amoxicillin/augmentin, cephalosporins, Co-trimoxazole, macrolides, tetracyclines

Question 3

3)Enterobacteriales

Klebsiella and E.coli

risk factors and treatment

Answer 3

Risk factors:
Extremes of age
hospital stay
COPD
hospital stay

drugs used before resistance: B-lactam/B-lactamase inhibitors (amoxicillin/clavulanate)

Question 4

4)Psuedomonas aeruginosa

Oxidase positive, motile, non fermenting, G-ve bacillus

Answer 4

-resistant to many antibiotics and disinfectants
-present in natural environment and in moisture

Question 5

virulence factor 1- adhesins:

Answer 5

Flagella and pilli
Lipopolysaccharide: for endotoxic activity
Alginate: forms capsule for- resisting phagocytosis and colonization

Question 6

Virulence factor 2 : Toxins and enzymes

Answer 6

-Exotoxin A (ETA): inhibit peptide chain elongation

-Exoenzymes S and T: actin rearrangement and cause necrosis

-LasA and LasB elastases: degrade tissue elastin and inhibit neutrophil

-Alkaline protease: disrupt immunity

-Phospholipase C: destroys tissues thru breaking down lipids

Question 7

Virulent factor 3: Diffusable pigments:

Answer 7

Pyocyanin- blue;toxic O2 prod

Pyoverdin-yellow green prod by pseudomonas

Pyorubin- reddish brown

Pyomelannin- dark brown

Question 8

Clinical features of typical pathogens:

Answer 8

A) necrotizing bronchopneumonia

B)skin and soft tisses:
Burn colonization
Ecthyma gangreosum

C)Urinary tract: urinary catheters

D) eyes: inital injury to cornea

E) Ears;
-swimmers ear
-malignant otitis- elderly and diabetics
-chronic otitis

Question 9

Antipseudomonal activity drugs:

Answer 9

B-lactams: Piperacillin,ceftazidime,imipenm,aztreonam

-Fluoroquinolone: Ciprofloxacin

-Aminoglycosides :Gentamicin and amikacin

MDR P.aeruginosa needs: ceftolozane/tazobactam