Staphylococcal bacteraemia: finding the path of least persistence NishaRanganathan,RebeccaJohnson,AndrewM.Edwards
Background• DespitethefallingincidenceofMRSAbacteraemia,therateofMSSAbacteraemiaisrising1
• Inasignificantpropor@onofcases,bacteraemiapersistsdespiteappropriatetherapy2
• Challengestotreatmentariseasunderthetwinthreatsofan@bio@csandtheimmune
system,bacteriabecomedormant,metabolicallyinac@veandarethusan@bio@ctolerant3
• TheregulatorofthestressresponseinS.aureus,SigB,regulatesentryintodormancy4
Thehostenvironmentmodulatesan7bio7c
suscep7bility
A B
C
Figure2.(A)Titra7ngconcentra7onofAHTinthecomplementedsigBmutantresultedinincreasingsigB expression, as evidencedby increase inpigmentproduc7onand (B)fibronec7nbinding (bothsigBdependentphenotypes). (C)IncreasingsurvivalofS.aureusinbloodonincreasinginduc7onofsigBexpressionwithAHTincomplementedmutantbutnotinemptyplasmidvector.
Figure1.Bloodmodulatesan7bio7csuscep7bilityofS.aureusonexposuretoCloxacillin(A)Gentamicin(B),Vancomycin(C),Ciprofloxacin(D)Clindamycin(E).Withtheexcep7onof(B)theaddi7onofan7bio7cfailedtosignificantlyenhancekillingcomparedtobloodalone,howeveran7bio7csfunc7onedinserum.
A
SigBmodulatesan7bio7csuscep7bilityinthehostcontext
Figure 4. (A) sigB effectors SA2440 and SA2452 promote survival in blood infec7onmodel.IncreasingexpressionofSA2452butnotSA2440increasessurvival inbloodalone(A)andinbloodplus cloxacillin (B) inadosedependentmanner. Increasingexpressionofbothgenesincreasessurvivalonexposuretociprofloxacin(C).SA2440butnotSA2452promotessurvivalonexposuretogentamicin(D).
Conclusions• Bloodappearstohaveaninhibitoryeffectontheac@vityofcertainan@bio@cs.
• SigBpromotessurvivalinbothbloodaloneplusincombina@onwithcloxacillin,ciprofloxacinandgentamicin.
• TwoSigBregulatedgeneshavebeeniden@fiedthatpromotesurvivalinanan@bio@cspecificmanner.
• Rethinkingtherapyinthecontextofthehost-pathogen-druginterac@onsmayleadtoinnova@vesolu@onstoenhanceexis@ngtreatmentstrategies.
References1. HealthProtec@onAgency.VoluntaryRepor2ngofStaphylococcusaureusBacteraemiainEngland,WalesandNorthernIreland,2010.London:HealthProtec@onAgency,20112. Kha@bR,etal.2006.PersistenceinStaphylococcusaureusbacteremia:incidence,characteris@[email protected]:7–143. KLewisMul@drugtoleranceofbiofilmsandpersistercellsCurrTopMicrobiolImmunol,322(2008),pp.107–131BischoffM,DunmanP,KormanecJ,MacapagalD,MurphyE,MountsW,Berger-BachiB,ProjanS.2004.Microarray-basedanalysisoftheStaphylococcusaureusσBregulon.JBacteriol186:4085–4099.
AcknowledgementsMembersofthefi`hflooroftheCentreforMolecularBacteriologyandInfec@onatImperialCollegeLondon,andtheEdwardsgroupinpar@cular,areacknlowedgedfortheir invaluable support. This work is funded by the MRC as part of a clinicalresearchtrainingfellowship
SigBpromotessurvivalinblood
010100010100AHT
WTΔsigB
ΔsigB
pEmpty
ΔsigBpEmpty
ΔsigBpEmpty
ΔsigBpsigB
ΔsigBpsigB
ΔsigBpsigB
0
10
20
30
40
50
% S
urviv
al
010100010100AHT
WTΔsigB
ΔsigB
pEmpty
ΔsigB
pEmpty
ΔsigB
pEmpty
ΔsigB
psigB
ΔsigB
psigB
ΔsigB
psigB
0.0
0.2
0.4
0.6
0.8
gentamicin
% S
urvi
val
WTΔsigB
ΔsigB
pEmpty
ΔsigB
pEmpty
ΔsigB
pEmpty
ΔsigB
psigB
ΔsigB
psigB
ΔsigB
psigB
0
2
4
6
8cloxacillin
% S
urvi
val
WTΔsigB
ΔsigB
pEmpty
ΔsigB
pEmpty
ΔsigB
pEmpty
ΔsigB
psigB
ΔsigB
psigB
ΔsigB
psigB
0
2
4
6
8
10
ciprofloxacin
% S
urvi
val
WT
ΔsigB
ΔsigBpEmpty
ΔsigBpEmpty
ΔsigBpEmpty
ΔsigBpsigB
ΔsigBpsigB
ΔsigBpsigB
0
100
200
300
clindamycin
% S
urv
ival
BloodSerum
WTΔsigB
ΔsigB
pEmpty
ΔsigB
pEmpty
ΔsigB
pEmpty
ΔsigB
psigB
ΔsigB
psigB
ΔsigB
psigB
0
50
100
150
vancomycin
% S
urvi
val
SigBregulatedgenesmodulatesurvivalinblood+/-
an7bio7cs
D
WTΔsigBp2440p24
40p2440
2440
pEmpty
2440
pEmpty
2440
pEmptyp2452p2452p2452
2452
pEmpty
2452
pEmpty
2452
pEmpty
0
5
10
15Blood Alone
% S
urvi
val
WTΔsigBp2440p2440p2440
2440
pEmpty
2440
pEmpty
2440
pEmptyp2452p2452p2452
2452
pEmpty
2452
pEmpty
2452
pEmpty
0
5
10
15
20
25
% S
urvi
val
Blood + Cloxacillin
WTΔsigBp2440p2440p2440
2440
pEmpty
2440
pEmpty
2440
pEmptyp2452p2452p2452
2452
pEmpty
2452
pEmpty
2452
pEmpty
0
2
4
6
% S
urvi
val
Blood + Ciprofloxacin
WTΔsigBp2440p2440p2440
2440
pEmpty
2440
pEmpty
2440
pEmptyp2452p2452p2452
2452
pEmpty
2452
pEmpty
2452
pEmpty
0.00
0.05
0.10
0.15
0.20
% S
urvi
val
Blood + Gentamicin
B
DC
A
E
cB
0 2 4 610
100
1000
Cloxacillin
Time (h)
% S
urvi
val
0 2 4 61
10
100
1000
Cloxacillin
Time (h)
% S
urvi
val
0 2 4 61
10
100
1000
Cloxacillin
Time (h)
% S
urvi
val
0 2 4 61
10
100
1000
Cloxacillin
Time (h)
% S
urvi
val
0 2 4 60.001
0.01
0.1
1
10
100
1000
Gentamicin
Time (h)
% S
urvi
val
0 2 4 61
10
100
1000
Vancomycin
Time (h)
% S
urvi
val
MJ blood+ vancMJ Blood
0 2 4 60.001
0.01
0.1
1
10
100
1000
Ciprofloxacin
Time (h)
% S
urvi
val
0 2 4 610
100
1000
Clindamycin
Time (h)
% S
urvi
val
B
Figure3.IncreasingsigBexpressionincreasessurvivalofS.aureusinbloodpluscloxacillinciprofloxacinandgentamicin(A,B,C)butnotonexposuretobloodplusvancomycinorclindamycin(D,E).
A
• Aim:TocharacterisetheroleofSigBanditseffectormoleculesinthesurvivalofS.aureusinaclinicalbacteraemiamodelLewisetal3
C D E
