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Phenotypic Characterisation of an
Outbreak Strain of Salmonella enterica
serovar Heidelberg
Claire Fingleton
Galway-Mayo Institute of Technology
Contents
1. Introduction
2. Methods & Results
3. Conclusions
4. Future Work
Introduction




Salmonella Heidelberg strain SH2107
Infection outbreak across 34 states
136 cases, 37 hospitalisations, 1 death
FDA investigation & product recall
Project Aim: Phenotypic characterisation of
SH2107 outbreak strain, in order to gain
understanding of its pathogenicity.
Methods of Characterisation
1.
Resistance
profiling
4. Biofilm
Formation
2. Curli
Fimbriae
expression
5. Motility:
(a) Swim
(b) Swarm
Control:
S. Typhimurium ATCC 14028
Reference: S. Heidelberg NCTC 5717
Outbreak: S. Heidelberg SH2107
3. Cellulose
Biosynthesis
6. Acid
Tolerance
1. Resistance Profiling
Outbreak Strain → Multi-Drug Resistant Phenotype
Antimicrobial Class
Antimicrobial
Amoxicillin
Penicillins
Ampicillin
Carbenicillin
Aminoglycosides
Gentamicin
Tobramycin
Tetracycline
Tetracyclines
Doxycycline
Minocycline
Key:
Sensitive Intermediate
Resistant
Reference Outbreak
2. Curli Fimbriae Expression
Control
Reference
Outbreak
• Red, dry and
rough (RDAR)
• Red and smooth
(RAS)
• Red and smooth
(RAS)
• Curli Fimbriae
expression
• Absent / Low
level expression
• Absent / Low
level expression
3. Cellulose Biosynthesis
Control
Reference
Outbreak
Strong cellulose
biosynthesis
Low level
cellulose
biosynthesis
Low level
cellulose
biosynthesis
4. Biofilm Assay in Defined Media and
Temperature Conditions
Absorbance at 570 nm
2.0
1.5
1.0
0.5
0.0
LB / LB / M9 / M9 / LB / LB / M9 / M9 / LB / LB / M9 / M9 /
25°C 37°C 25°C 37°C 25°C 37°C 25°C 37°C 25°C 37°C 25°C 37°C
Control
Control
Reference
Reference
Outbreak
Outbreak
5. Swim Motility Assay
Diameter of region of spread (mm)
Swim Motility of Isolates following 8 Hours Incubation
80
60
Room Temp
40
37°C
20
0
Control
Reference
Outbreak
6. Acid Tolerance Assay
100
Control
Reference
% Survival
80
Outbreak
60
40
20
0
0
30
60
90
120
150
Time
180 (Min)
Conclusions
SH2107
Pathogenicity
Multi-Drug
Resistant
Phenotype
Evasion of Innate
Immune System
Lack of
Curli
Fimbriae
Increased
Acid
Tolerance
Future Work
References
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