Ciência
Rural,
SantaAmerican
Maria, clinical
v.49:01,
e20180744,
Genotyping
of South
isolates
of Pythium2019
insidiosum based on single nucleotide
polymorphism-based multiplex PCR. 1
http://dx.doi.org/10.1590/0103-8478cr20180744
ISSNe 1678-4596
MICROBIOLOGY
Genotyping of South American clinical isolates of Pythium insidiosum based on single
nucleotide polymorphism-based multiplex PCR
Maria Isabel de Azevedo4
Lara Baccarin Ianiski2
Paula Cristina Stibbe1
Carla Weiblen1
Daniela Isabel Brayer Pereira5
Régis Adriel Zanette6
Luís Antônio Sangioni1
Rodolfo Rivero7 Janio Morais Santurio3
Sônia de Avila Botton1,2*
Programa de Pós-graduação em Medicina Veterinária (PPGMV), Departamento de Medicina Veterinária Preventiva (DMVP), Universidade
Federal de Santa Maria (UFSM), Centro de Ciências Rurais (CCR), Santa Maria, RS, Brasil.
2
Programa de Pós-graduação em Ciências Farmacêuticas (PPGCF), Universidade Federal de Santa Maria (UFSM), Santa Maria, RS, Brasil.
3
Departamento de Microbiologia e Parasitologia (Demip), Universidade Federal de Santa Maria (UFSM), Centro de Ciências da Saúde (CCS),
Santa Maria, RS, Brasil.
4
Faculdade de Medicina Veterinária, Universidade Federal de Minas Gerais (UFMG), Minas Gerais, RS, Brasil.
5
Departamento de Microbiologia e Parasitologia, Instituto de Biologia (IB), Universidade Federal de Pelotas (UFPel), Pelotas, RS, Brasil.
6
Programa de Pós-graduação em Ciências Biológicas: Farmacologia e Terapêutica, Universidade Federal do Rio Grande do Sul (UFRGS),
Porto Alegre, RS, Brasil.
7
Laboratorio Regional Noroeste DILAVE “Miguel C. Rubino”, ministério de Ganadería Agricultura e Pesca Casilla de Correo, 97105-900,
Santa Maria, RS, Brasil. E-mail: sabott20@gmail.com. *Corresponding author.
1
ABSTRACT: We aimed to genotype the South American clinical isolates of Pythium insidiosum using the single nucleotide polymorphisms
(SNP) of the ribosomal DNA sequences (rDNA). Previously, an SNP-based multiplex-PCR was able to distinguish three different clades of
P. insidiosum isolates. Thus, we used this assay to evaluate South American clinical isolates of P. insidiosum (n=32), standard strains from
Costa Rica (n=4), Thailand (n=3), Japan (n=1), and India (n=1), a standard strain of Pythium aphanidermatum, and Brazilian environmental
isolates of Pythium torulosum, Pythium rhizo-oryzae and Pythium pachycaule voucher (n=3). It was possible to allocate each American P.
insidiosum isolate to clade I, the isolates of India, Japan, and Thailand to clade II, and the Thai isolate to clade III. P. aphanidermatum,
P.torulosum, P.rhizo-oryzae and P.pachycaule voucher isolates were not amplified. For the first time, a P. insidiosum isolate from Uruguay,
South America, was included in molecular analyzes. By SNP-based multiplex-PCR, it was possible to perform the identification and genotyping
of the South American isolates of P. insidiosum, demonstrating similar genetic characteristics of these isolates.
Key words: Pythium insidiosum, Pythiosis, molecular detection, genotype, single nucleotide polimorphisms.
Genotipagem de isolados clínicos de Pythium insidiosum da América do Sul utilizando polimorfismos
de nucleotídeo único baseado em PCR multiplex
RESUMO: O objetivo deste estudo foi genotipar isolados clínicos de Pythium insidiosum da América do Sul utilizando polimorfismos de
nucleotídeo único (SNP) de sequências de rDNA. Anteriormente, um multiplex-PCR baseado em SNP foi capaz de distinguir P. insidiosum
em três diferentes clados. Dessa forma, utilizamos este método para avaliar isolados clínicos de P. insidiosum da América do Sul (n=32),
cepas padrão da Costa Rica (n=4), Tailândia (n=3), Japão (n=1) e Índia (n=1), uma cepa padrão de Pythium aphanidermatum e isolados
ambientais brasileiros de Pythium torulosum; Pythium rhizo-oryzae e Pythium pachycaule voucher (n=3). Os isolados analisados foram
alocados aos clados: I (americanos), II (isolados da Índia, Japão e Tailândia), e III (um isolado tailandês). P. aphanidermatum, P.torulosum,
P.rhizo-oryzae e P.pachycaule voucher não foram amplificados. Pela primeira vez, um isolado de P. insidiosum do Uruguai foi incluído
em análises moleculares. Através da multiplex-PCR baseada em SNP, foi possível realizar a identificação e genotipagem dos isolados sulamericanos de P. insidiosum, demonstrando características genéticas semelhantes entre esses isolados.
Palavras-chave: Pythium insidiosum, Pitiose, detecção molecular, genótipo, polimorfismos de nucleotídeo único.
INTRODUCTION
Pythium genus is an ecofriendly
oomycete found in a varied ecosystem. Most
species are saprobic or pathogens of plants, algae,
fishes, insects, and mammals (ADHIKARI et al.,
Received 09.11.18
2013). Pythium insidiosum causes pythiosis, a
relevant infectious disease in human and animals
that is widely distributed throughout the world
(GAASTRA et al., 2010). In Brazil, this oomycete
is present predominantly in the swampy areas of
Pantanal Mato-Grossense and Rio Grande do Sul
Approved 11.09.18
Returned by the author 12.09.18
CR-2018-0744.R1
Ciência Rural, v.49, n.1, 2019.
2
Weiblen et al.
State (RS) (SANTOS et al., 2014; WEIBLEN et
al., 2016). Little is known about the presence of
pythiosis in some countries of South America,
such as Uruguay, where the first case in an equine
was recently reported in Costas del Tacuarí,
Departamento de Treinta y Tres (LABORATORIO
REGIONAL ESTE DE DILAVE, 2012).
Due to the difficulty of diagnosing
pythiosis and the high costs for laboratory
identification of P. insidiosum, as well as the
similarity to other agents, especially other
oomycetes and filamentous fungi, there is a need
for diagnostic tools that can identify rapidly this
relevant microorganism. VILELA et al. (2015)
proposed a biochemical assay for identification of
oomycetes; however, this technique should still be
used carefully for the evaluation of P. insidiosum
isolates (KRAJAEJUN et al., 2018).
Molecular biology tools have been
successfully employed for diagnosing pythiosis,
mainly using polymerase chain reaction (PCR)
targeting the P. insidiosum internal transcribed
spacer (ITS) of the rRNA locus, i.e., the ribosomal
DNA (rDNA region) that consists of 18S rRNA,
internal transcribed spacer 1 (ITS1), 5.8S rRNA,
internal transcribed spacer 2 (ITS2), and 28S rRNA
(GROOTERS & GEE, 2002). Phylogenetic studies of
P. insidiosum have already been used with different
genetic markers to elucidate aspects related to
epidemiology, pathogenesis, and hosts (SCHURKO
et al., 2003a,b; KAMMARNJESADAKUL et al.,
2011; AZEVEDO et al., 2012; RIBEIRO et al., 2017).
The first phylogenetic analyses grouped P. insidiosum
in three clusters: cluster I North, Central, and South
America; cluster II Australia, North America,
Southeast Asia, and Thailand; and cluster III North
America and isolates from Thailand (SCHURKO
et al., 2003a,b). However, these analyses have
limitations owing to the high costs, time required for
DNA sequencing, and the delay in obtaining results.
Simple sequence repeat (SSR) and single
nucleotide polymorphism (SNP) markers have been
used for studies of diversity and relationship in
different microorganisms, including P. insidiosum
(SUPABANDHU et al., 2007; RUJIRAWAT et al.,
2017). The purpose of our study was genotyping
American clinical isolates of P. insidiosum using a fast,
simple, and low-cost tool based on SNP multiplex PCR.
Costa Rica (n=4), Thailand (n=3), Japan (n=1), and
India (n=1) were analyzed (Table1). Additionally, one
standard strain of Pythium aphanidermatum and three
environmental species of Pythium (P.torulosum, P.rhizooryzae and P.pachycaule voucher) were included in this
research. All isolates were cultivated and submitted to
total DNA extraction and amplification of rDNA region
were according to AZEVEDO et al. (2012) using the
primers ITS1 (5′-TCCGTAGGTGAACCTGCGG-3′)
and ITS4 (5′-CTTCCGTCAATTCCTTTAAG-3′)
(WHITE et al., 1990). The primers used for
SNP multiplex PCR amplification were ITS1,
R1
(5′-CCTCACATTCTGCCATCTCG-3’),
R2
(5′-ATACCGCCAATAGAGGTCAT-3′),
and
R3
(5′-TTACCCGAAGGCGTCAAAGA-3′)
(RUJIRAWAT et al., 2017). Amplifications were
performed according to RUJIRAWAT et al. (2017)
with modifications. Briefly, in a final volume of 25μL,
the PCR reaction contained 1μM of the forward primer
ITS1, 0.5μM each of the reverse primers (R1, R2, and
R3), 1.5 units of Taq DNA polymerase (Invitrogen),
200μM of each deoxynucleotide, 1.5mM MgCl2,
1x enzyme buffer, and 100ng of DNA sample. The
amplifications were carried out in a programmable
thermal cycler (PTC-100, MJ Research), with initial
denaturation at 95°C for 5min, 20 cycles of denaturation
at 95°C for 30s, annealing at 53°C for 30s, and extension
at 72°C for 45s, and then a final extension at 72°C for
10min. A 5µL aliquot of the PCR product was submitted
to electrophoresis on 1% agarose gels, stained with
ethidium bromide, and visualized under ultraviolet light.
The PCR products of rDNA region
presenting a single band with the desired length
(approximately 500-800pb) were purified with
PureLink PCR Purification Kit (Invitrogen), and the
DNA was sequenced in an automatic sequencer (ABIPrism 3500 Genetic Analyzer) using the primers ITS1
and ITS4 (WHITE, 1990). Phylogenetic analysis for
rDNA region was conducted by Neighbor-joining (NJ)
method with 10,000 bootstrap replicates. All rDNA
sequences from P. insidiosum clinical isolates from
South America and standard strains of Costa Rica, India,
Japan and Thailand, as well as P. aphanidermatum,
P.torulosum, P.rhizo-oryzae and P.pachycaule voucher
and Phytopythium vexans (outgroup) were used to
construct the phylogenetic tree.
MATERIALS AND METHODS
Based on the multiplex PCR targeting
the three SNPs identified in the rDNA region, all
the thirty-six South and Central American isolates
of P. insidiosum and the five standard strains from
Thirty-one clinical isolates of P. insidiosum
from Brazil, one from Uruguay, standard strains from
RESULTS AND DISCUSSION
Ciência Rural, v.49, n.1, 2019.
Genotyping of South American clinical isolates of Pythium insidiosum based on single nucleotide polymorphism-based multiplex PCR. 3
Thailand, India and Japan were grouped in their
respective clades, as suggested by RUJIRAWAT et
al. (2017) (Table 1, Figure 1). We observed that the
American clinical isolates, grouped in clade I, generated
amplicons of approximately 490 and 660bp when
using the primers ITS1/R1 and ITS1/R2, respectively.
P. aphanidermatum, P.torulosum, P.rhizo-oryzae and
P.pachycaule voucher were not amplified since these
isolates do not belong to any P. insidiosum clade.
The multiplex PCR targeting the three
SNPs identified in the rDNA region was developed by
RUJIRAWAT et al. (2017) and has many advantages,
such as 100% of sensitivity, and specificity, rapid
and cost-effective identification, and genotyping of P.
insidiosum. As these authors evaluated only one Brazilian
isolate of P. insidiosum in their study, we proposed to
evaluate an expressive number of P. insidiosum clinical
isolates from South America using this technique.
The molecular phylogeny obtained for the
rDNA region showed P. insidiosum as paraphyletic
in relation to other Pythium species. However, it
was observed that South and Central American P.
insidiosum isolates were grouped together, forming
a monophyletic group. In addition, isolates from
other countries formed a basal-positioning group
in relation to the American isolates (Figure 2).
These results were consistent with AZEVEDO
et al. (2012) and RIBEIRO et al (2017) that used
rDNA (ITS) and cytochrome c oxidase subunit II
as molecular markers and exo-1,3-β glucanase gene
in phylogenetic analyses of Brazilian P. insidiosum
isolates, respectively. Moreover, all isolates of
P. insidiosum from India, Japan and Thailand
were grouped in different clades as proposed by
SCHURKO et al. (2003 a,b) and lately supported by
SUPABANDHU et al. (2008).
According to RUJIRAWAT et al. (2017)
multiplex PCR targeting the three SNPs identified
in the rDNA (ITS) region were able to allocate
P. insidiosum to clade-I provided two amplicons
(approximately 490 and 660bp), whereas the cladesII and –III showed only one amplicon (approximately
660 and 800bp, respectively). The same results
were obtained in this study, allowing to assign
each American P. insidiosum isolates to clade I,
isolates from India, Japan, and Thailand to clade
II, and one Thai isolate to clade III. In addition, P.
aphanidermatum, P.torulosum, P.rhizo-oryzae and
P.pachycaule voucher were not amplified. Thus,
these results evidenced that this molecular biology
methodology is specific and sensitive for identification
and genotyping of P. insidiosum, in agreement with
RUJIRAWAT et al. (2017).
The genome sequences of P. insidiosum
recently available can be a useful genetic resource for
exploring aspects related the biology and evolution
Figure 1 - Agarose gel electrophoresis of PCR amplification of the rDNA sequences of Pythium insidiosum from
strains of each clade and controls. The amplicon size generated by SNP were: primers ITS1/R1 (~490bp)
+ primers ITS1/R2 (~660bp)=Clade I - 1: P. insidiosum 0-44, 2: P. insidiosum 138, 3: P. insidiosum 219,
4: P. insidiosum 247, 5: P. insidiosum 260, 6: P. insidiosum 152, 7: P. insidiosum 152, primers ITS1/R2
(~660bp)=Clade II - 8: P. insidiosum 1H, 9: P. insidiosum 2H, 10: P. insidiosum 6H, 11: P. insidiosum 7H,
primers ITS1/R3 (~800bp) = Clade III - 12: P. insidiosum 8H, 13: P. aphanydermatum, 14: P. tolurosum,
15: Negative control: ddH2o (PCR grade), 16: 100-bp DNA ladder marker.
Ciência Rural, v.49, n.1, 2019.
Weiblen et al.
4
Table 1 - Isolates of Pythium. insidiosum (n=36) and other species of Pythium (n=4) used for evaluation of the multiplex PCR assay and
their information of GenBank acession number of rDNA sequence, isolate source, geographic origin and phylogenetic clade.
Isolate
GenBank#
Isolate source
Geographic origin
Amplicon (bp)##
Clade
0-44
118
121
123
126
135
137
138
142
143
152
156
178
187
210
219
223
232
247
252
254
259
260
268
271
290
291
293
295
296
337
339
ATCC 58637
CBS 57485
3H - CBS 57685
4H- CBS 57585
1H-CBS 119453
2H-CBS 119455
6H- CBS 70283
7H- CBS 77784
8H- CBS 119454
P.aphanidermatum CBS 128995
P.torulosum
P.rhizo-oryzae
P.pachycaule voucher
MF767408
JN126280
JN126282
JN126283
JN126286
MH813295
MH813296
JN126289
MH813297
JN126290
MH813298
JN126293
JN126295
JN126296
JN126298
JN126299
JN126300
JN126302
JN126304
MH813299
MH813300
JN126306
JN126307
JX675977
MH813301
KJ176713
MH813302
MH813303
MH813304
MH813305
MH813306
MH813307
JN126310
AY598637
AB898106
AB971178
EF016853
EF016855
AY151170
AY151169
AB971185
JF412451
MH813308
MH813309
MH813310
Equine
Equine
Equine
Equine
Equine
Equine
Equine
Equine
Equine
Equine
Equine
Equine
Equine
Equine
Equine
Equine
Equine
Equine
Equine
Equine
Equine
Equine
Equine
Canine
Equine
Equine
Equine
Equine
Canine
Equine
Equine
Equine
Equine
Equine
Equine
Equine
Human
Human
Equine
Mosquito larva
Human
Human
Environmental
Environmental
Environmental
Uruguay
Jaguari*
Santa Maria*
Cachoeira do Sul*
Corumbá*
Corumbá*
Corumbá*
Corumbá*
Corumbá*
Corumbá*
Santa Maria*
Santa Maria*
Corumbá*
Jari*
Uruguaiana*
São Lourenço do Sul*
Cachoeira do Sul*
Uruguaiana*
Restinga Seca*
Uruguaiana*
Pelotas*
Santa Vitória do Palmar*
Santa Vitória do Palmar*
Canguçu*
Silveira Martins*
Santa Maria*
Pelotas*
Rio Grande*
Pelotas*
Pelotas*
Jaguari*
Uruguaiana
Costa Rica
Costa Rica
Costa Rica
Costa Rica
Thailand
Thailand
Japan
India
Thailand
Afghanistan
Capão do Leão*
Santa Vitória do Palmar*
Santa Vitória do Palmar*
~490 and 660pb
~490 and 660pb
~490 and 660pb
~490 and 660pb
~490 and 660pb
~490 and 660pb
~490 and 660pb
~490 and 660pb
~490 and 660pb
~490 and 660pb
~490 and 660pb
~490 and 660pb
~490 and 660pb
~490 and 660pb
~490 and 660pb
~490 and 660pb
~490 and 660pb
~490 and 660pb
~490 and 660pb
~490 and 660pb
~490 and 660pb
~490 and 660pb
~490 and 660pb
~490 and 660pb
~490 and 660pb
~490 and 660pb
~490 and 660pb
~490 and 660pb
~490 and 660pb
~490 and 660pb
~490 and 660pb
~490 and 660pb
~490 and 660pb
~490 and 660pb
~490 and 660pb
~490 and 660pb
~660
~660
~660
~660
~800
NA
NA
NA
NA
I
I
I
I
I
I
I
I
I
I
I
I
I
I
I
I
I
I
I
I
I
I
I
I
I
I
I
I
I
I
I
I
I
I
I
I
II
II
II
II
III
-
#
GenBank acession number corresponding to rDNA (ITS) sequences. ##Amplicon size generated by SNP (base pair) using: Primers
ITS1/R1 (~490 bp) + Primers ITS1/R2 (~660bp)=Clade I; Primers ITS1/R2 (~660bp)=Clade II; Primers ITS1/R3 (~800bp)=Clade III;
and no amplification)=No P. insidiosum genotype. =This isolate does not belong to P. insidiosum clade. *Municipality of Brazil.
Ciência Rural, v.49, n.1, 2019.
Genotyping of South American clinical isolates of Pythium insidiosum based on single nucleotide polymorphism-based multiplex PCR. 5
Figure 2 - Neighbor-joining tree based on sequence analysis of the rDNA ITS showing relationships among clinical isolates of P.
insidiosum from South America (Brazil (BR) and Uruguay (Uy) and standard strains of Costa Rica (CR), India (IN), Japan
(JP) and Thailand (TH), as well as P. aphanidermatum and environmental Pythium spp. (P. pachycaule voucher, P. rhizo
oryzae and P. torulosum isolates). Bootstrap values expressed in percentages based on 10,000 replicates are present at their
corresponding clades.
P.insidiosum and other oomycetes since
independently assessed genes may not provide
much information when compared to genomes.
However, genome analyses are still recent, expensive
and laborious when compared to the available
molecular analyses (RUJIRAWAT et al., 2015;
TANGPHATSORNRUANGA et al., 2016).
For the first time, a P. insidiosum isolate
from Uruguay were included in phylogenetic analysis.
A single case of equine pythiosis has been reported by
the Laboratorio Regional Este de DILAVE (2012). It
is of note there is still little knowledge about pythiosis
in Uruguay. However, we are aware of other cases of
equine pythiosis in that country (unpublished data).
Additionally, MACHADO et al. (2018) suggested
that P. insidiosum is a generalist pathogen that has
the potential to move between the borders of southern
Brazil, e.g., RS (the southernmost state in Brazil)
Ciência Rural, v.49, n.1, 2019.
Weiblen et al.
6
and Uruguay. P. insidiosum isolate from Uruguay
was grouped in clade I, together with isolates from
Brazil. This was evidenced by both multiplex PCR
and phylogenetic analysis, proving that the South
American isolates are grouped in the same clade, as
previously suggested (SCHURKO et al., 2003a,b;
KAMMARNJESADAKUL et al., 2011; AZEVEDO
et al., 2012; RIBEIRO et al., 2017).
CONCLUSION
The
SNP-based
multiplex-PCR
methodology has benefits (i.e., fast, simple, and lowcost) and was possible to carry out the identification
and genotyping of the South American isolates of
P. insidiosum. For the first time a P. insidiosum
isolate from equine in Uruguay was identified
and genotyped. Furthermore, the American P.
insidiosum isolates evaluated showed similar
genetic characteristics.
ACKNOWLEDGMENTS
The authors are grateful to Conselho Nacional de
Desenvolvimento Científico e Tecnológico (CNPq: 442020/2014-7),
Fundação de Amparo à Pesquisa do Estado do Rio Grande do Sul
(PqG/FAPERGS: 27293.414.15435.20062017) and Coordenação de
Aperfeiçoamento de Pessoal de Nível Superior (CAPES) (finance
code 001) for scientific, financial support and student’s scholarships.
DECLARATION
INTERESTS
OF
CONFLICTING
The authors declare no conflict of interest. The
founding sponsors had no role in the design of the study; in the
collection, analyses, or interpretation of data; in the writing of the
manuscript, and in the decision to publish the results.
AUTHORS’ CONTRIBUTIONS
The authors contributed equally to the manuscript.
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