intracellular S. aureus S. aureus : : intracellular what does it - - PowerPoint PPT Presentation

▶
intracellular s aureus s aureus intracellular what does
SMART_READER_LITE
LIVE PREVIEW

intracellular S. aureus S. aureus : : intracellular what does it - - PowerPoint PPT Presentation

Apr 25, 2023 113 likes •366 views

intracellular S. aureus S. aureus : : intracellular what does it mean ? what does it mean ? F. Van Bambeke F. Van Bambeke Unit de Pharmacologie cellulaire et molculaire Unit de Pharmacologie cellulaire et molculaire Universit

slide-1
SLIDE 1

intracellular intracellular S. aureus

  • S. aureus :

: what does it mean ? what does it mean ?

  • F. Van
  • F. Van Bambeke

Bambeke Unité de Pharmacologie cellulaire et moléculaire Unité de Pharmacologie cellulaire et moléculaire Université catholique de Louvain Université catholique de Louvain Brussels, Belgium Brussels, Belgium GSK-chair of infectious diseases

slide-2
SLIDE 2

Intracellular killing of bacteria by host cell defense mechanisms

Phagosomes Lysosomes Phagolysosomes

slide-3
SLIDE 3

Some bacteria can escape host cell defense mechanisms

Phagosomes Lysosomes Phagolysosomes Phagosomes

Salmonella spp. Brucella spp.

Endoplasmic reticulum

Legionella pneumophila

Early endosomes

Mycobacterium spp.

Inclusions

Chlamydia spp.

Cytosol

Listeria monocytogenes Shigella flexeneri Legionella pneumophila Staphylococcus aureus

  • pportunistic intracellular bacteria

Carryn et al, Infect Dis Clin North Am. (2003) 17:615-34

slide-4
SLIDE 4

Evidence for intracellular S. aureus in vitro and in vivo – model of mastitis

phagocytic cells PMN, macrophages non phagocytic cells

Brouillette et al, Vet Microbiol (2004) 101:253-262; Microb Pathog. (2003) 35:159-68.

slide-5
SLIDE 5

Intracellular cycle of S. aureus

FnBP β-integrin fibronectin adhesion internalisation actin polymerisation cytotoxicity and cellular response escape In the cytosol cytokines apoptosis of host cell

Lowy, Trends Microbiol (2000) 8:341-342

slide-6
SLIDE 6

Intracellular survival of S. aureus

FnBP β-integrin fibronectin adhesion internalisation actin polymerisation cytotoxicity and cellular response cytokines

Lowy, Trends Microbiol (2000) 8:341-342

slide-7
SLIDE 7

In vivo implication remains however a matter of debate

Clearly established in in vitro models Few reports in vivo low density of intracellular foci destructive nature of S. aureus infection multiple mechanisms of adherence and invasion

slide-8
SLIDE 8
  • S. aureus can survive and multiply in

phagocytes and several other cell types

slide-9
SLIDE 9

endothelial cells epithelial cells keratinocytes

  • steoblasts

But is this associated with pathology ?

slide-10
SLIDE 10

In vivo implication remains however a matter of debate

Clearly established in in vitro models Few reports in vivo low density of intracellular foci destructive nature of S. aureus infection multiple mechanisms of adherence and invasion Useful to study to understand pathogenesis and explore therapeutic options

slide-11
SLIDE 11

Setting up a model of intracellular infection

  • ver a 24 h period of time
  • infection of macrophages (with opsonized bacteria)
  • Mouse (J774; 5 bact/cell)
  • Human (THP-1; 4 bact/cell)
  • washing with GEN 50 µg/ml to eliminate extracellular bacteria
  • incubation for up to 24 h with

GEN 0.5 µg/ml (MIC) antibiotic under study no antibiotic gentamicin 0.5 mg/L

Seral et al. AAC 2003 47:2283-2292

5 h infection

slide-12
SLIDE 12

6 12 18 24 2 4

extra intra

time (h)

∆ log CFU

from time 0 h

Description of the model : how does S. aureus grow intracellularly ?

Seral et al. AAC 2003 47:2283-2292

slide-13
SLIDE 13

intracellular vs extracellular activity of antibiotics : is it easily predictible ? Intracellular activity =

  • MIC. X accumulation
slide-14
SLIDE 14

intracellular vs extracellular activity of antibiotics : PK – PD in action

Carryn et al, Infect Dis Clin North Am. (2003) 17:615-34

slide-15
SLIDE 15

Intracellular killing is visible for antibiotics working on cell wall

control

  • xacillin
  • ritavancin
slide-16
SLIDE 16

Smart choice of antibiotics based on balanced extra- / intra- activity

slide-17
SLIDE 17

Intracellular activity : possible reasons for loss of activity

AB Cc/Ce Max. activity OXA < 4

  • 1.6

GEN 4

  • 2.5

MXF 8

  • 2.8

AZM 38

  • 0.2

ORI 148

  • 3.2

Drug (lysosomal) accumulation

slide-18
SLIDE 18

Intracellular activity : possible reasons for loss of activity

Lysosomal acidic pH

AB MIC pH 7.4 pH 5.4 AZM 0.5 512 GEN 0.5 16 MXF 0.06 0.25 ORI 0.25 0.25 OXA 0.125 0.06

slide-19
SLIDE 19

Intracellular activity : possible reasons for loss of activity

bioavailability macrophages exposed to oritavancin

slide-20
SLIDE 20

Intracellular activity : possible reasons for loss of activity

access to the infected compartment slow accumulation by endocytosis aminoglycosides glycopeptides Rapid equilibration by diffusion quinolones beta-lactams

slide-21
SLIDE 21

Intracellular activity : possible reasons for loss of activity

Bacterial responsiveness

6 12 18 24 2 4

extra intra

time (h) ∆ log CFU from time 0 h

slow growth metabolic changes involved in invasion and toxicity

slide-22
SLIDE 22

Take home message

slide-23
SLIDE 23

Thanks to …

Maritza Maritza Barcia Barcia-

  • Macay

Macay Cristina Cristina Seral Seral Marie Marie-

  • Paule

Paule Mingeot Mingeot-

  • Leclercq

Leclercq Paul M. Paul M. Tulkens Tulkens Sandrine Sandrine Lemaire Lemaire