Yersinia pestis in Madagascar paper Flashcards
What
3 pandemic of plague
6th century (Procopius)
14th century (Boccacio)
• 1894 (Camus)
1894
Alexandre Yersin identify a gram-negative rod:
Yersinia pestis (then Pasteurella pestis), and its reservoir:
rats
1898
Paul Louis Simond: Y. pestis transmitted by fleas
Y. pestis is subdivided into ..
three biovars
Antiqua
•Medievalis
•Orientalis
•Because strains in areas of antique foci are not
Orientalis, then Orientalis must be associated
with 3rd pandemic
Pulse Field Gel Electrophoresis (PFGE)
SpeI DNA patterns of 8 strains of Y. pestis closely
related to biovars (Lucier & Brubaker 1992
I-CeuI
DNA patterns of 9 strains also closely related to biovars (Rakin & Heeseman 1995)
RFLP
of 16S rRNA genes of 70 strains can be subdivided into 16 ribotypes
Orientalis
Orientalis correspond to Ribotype B (Guiyoule et
al. 1994)
But some Orientalis have ribotype G or E
1994 outbreak in India: ribotype S
Suggest that within a century:
Chromosomal rearrangement leading to new
strains
Madagascar:
I. Plague arrived first time in 3rd pandemic
II. Risks of extraneous plague importation
limited because it is an island
III. Wide range of strains and epidemiological
characteristics available
Objective of paper
To demonstrate that in Madagascar Y. pestis strains
collected
1. Before 1982 had classical ribotype B
2. After 1982 new strains with ribotype R, Q
and T emerged in a specific region of the
island and are now well established in
ecosystem
3. Association between genomic profiles,
ribotypes, and plasmids
Methods
All are biovar Orientalis (negative for glycerol fermentation,
positive for nitrate reduction to nitrite)
Strains grown on Tryptic soy agar plates
DNA extracted and digested with EcoRI or EcoRV
0.8% agarose gel electrophoresis
Then hybridization with 16S+23S rRNA probes
Plasmid extracted and digested with EcoRV
PFGE
genomic DNA in agarose plugs
angle of 120opulse, 1 to 10 s over 29 h
Antibiotic resistance profile with disk
how many strains of Y. pestis isolated between 1939 and 1996
187
Results
Ribotype B: RI.1 + RV.2
Ribotype R: RI.12 + RV.12
Ribotype Q: RI.13 + RV.2
Ribotype T: RI.15 + RV.2
R: isolated from Ambositra prefecture
Q: isolated from Ambohimahasoa prefecture
High plateaus
identification of how many new ribotypes strains
59
How many isolates from Ambositra
98
How many isolates from Ambohimahasoa
33
Before 1982
13 strains B only
1982-1994
strains R only from Ambositra
All strains within 20 km
1994
first time R is outside this region
1983
Q in areas wide apart
so origin before 1983
Ambositra and Ambohimahasoa
Strain 22/95: mix of Q and R in one female, 40
years old
1994
: T in Ambohimahasoa only
Evolution of new variants in Ambositra and Ambohimahasoa
Longitudinal study
I. Total number of isolates has increased since
1980’s
II. Ribotype B remains major ribotype in this region
III. Since 1982 and 1983: Q and R isolated more
frequently over increasingly wider areas
42% of strains since 1990 are Q and R
how many pulsotypes
11
B: pulsotypes 1-8
R: pulsotypes 10-11
Q: pulsotype 9
clonal origin
Consistent pulsotype for Q and R
Three plasmids
I. pFra/Tox: fraction 1 antigen and a murine
toxin
II. pYV: virulence plasmid common to three
pathogenic Yersinia species
III. pPla: bacteriocin pesticin and
plasminogen activator
Three plasmid profiles
P1: Ribotype B and R
P2: Ribotype Q
P3: ribotype T
is there Phenotypic differences associated with ribotypes
no
Plague introduced in 1898 by
ship from India
Unlikely that new strains of Y. pestis introduced from
abroad as..
I. No Y. pestis in the world display ribotypes
Q, R, T
II. New variants isolated from high plateaus
III. They appeared recently many years after
establishment of surveillance
IV. Introduction of 3 different strains in 3
different times is unlikely
V. Little divergence in pulsotypes
what may reflect
intensive multiplication and circulation of the
microorganism
Isolation of 3 new variant from same region
Spreading of this strain suggest ….
it is now
colonizing new areas
R, Q, and T: different from original type (B) in their…
Ribotypes (rRNA) Pulsotypes (genomic DNA) Plasmid profiles (plasmid DNA)
what is explained by a local
modification of the original Y. pestis that spread
over the world
Isolation of strains of biovar Orientalis with a ribotype
other than B in countries such as Madagascar,
India, Vietnam
Based on comparative genomic analysis: genome of 1347-1349…
appears as ancestor of all contemporary Y. pestis. (biovars are
following environmental adaptation of post 1347 pandemic)
• Other factors such as:
– environment
– vector dynamics
– host susceptibility