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Memórias do Instituto Oswaldo Cruz
Fundação Oswaldo Cruz, Fiocruz
ISSN: 1678-8060 EISSN: 1678-8060
Vol. 92, Num. 2, 1997, pp. 251-252
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Mem Inst Oswaldo Cruz, Rio de Janeiro, Vol. 92(2),
Mar/Apr 1997, pp.251-252
RESEARCH NOTE
In vitro responses of Plasmodium falciparum isolates to five antimalaria
drugs in French Guiana during 1994 and 1995
Jean-Marc Reynes/+, Josiane Fargette*, Pascal Gaborit*, Steve Yarde*
Institut Pasteur du Cambodge, BP 983, Phnom Penh, Cambodia
*Laboratoire d'Arbovirologie et Entomologie Médicale, Institut Pasteur de
Guyane, Avenue Pasteur, BP 6010, 97 306 Cayenne, French Guiana
+Corresponding author. Fax: +855-23-725.606
Received 27 May 1996
Accepted 10 December 1996
Code Number:OC97049
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Key words: Plasmodium falciparum - drug susceptibility -
French Guiana
In vitro susceptibility of Plasmodium falciparum has been
studied in French Guiana in the late 80's by JP Dedet et al. (1988 Bull
Soc Path Ex 81: 88-93) and F Gay et al. (1992 XXII congres SMAGF
Cayenne 7-11 avril: 32-33). Since this period epidemiological changes
occurred in the Maroni valley, region with the higher level of endemicity,
because of the desorganization of the health centers on the Suriname side
and the increase of goldminer settlements which are not well controlled on
both sides. With this point of view and considering the evolution of the
susceptibility of P. falciparum in French Guiana, in
vitro test were carried out with five drugs commonly used in the
treatment of malaria: chloroquine, amodiaquine, quinine, mefloquine and
halofantrine.
Blood samples (10 ml) were collected in Sodium Heparinate tubes from
patients who attended a medical center or a hospital in French Guiana and
in whom the diagnosis of P. falciparum infection was microscopically
established. Then blood samples were sent to our Institute in Cayenne.
These patients included mild and severe cases, according to DA Warrell et
al.'s case definitions (1990 Trans R Soc Trop Med Hyg 84 (Suppl 2):
1-65).
The in vitro tests were carried out according to RE Desjardins et
al. (1979 Antimicro Agents Chemother 16: 710-718) technique,
modified by P Brasseur et al. (1986 Am J Trop Med Hyg 35: 711-716).
The test consists of a one step isotopic 48 hr microtest. Five antimalarial
drugs were used: chloroquine diphosphate (Sigma, France), amodiaquine
hydrochloride since March 1995 (Laboratoire Roussel, France), quinine
hemisulfate (Sigma, France), mefloquine hydrochoride (Produits Roche,
Suisse), halofantrine hydrochloride (Laboratoire SK&F, France). The
final two fold dilutions in the wells of each drug (as base) ranged from
1,875 to 7.3 nM, 843 to 1.65 nM, 3,700 to 14.45 nM, 793 to 3.1 nM and 32 to
0.0625 nM, respectively. The 50% effective concentrations (EC50) were
calculated using log dose response probit analysis. Drug resistances of
a P. falciparum isolate were established if EC50 >100 nM for
chloroquine base, EC50 > 60 nM for amodiaquine base, EC50 > 500 nM for
quinine base, EC50 > 30 nM for mefloquine base, EC50 > 6 nM for
halofantrine base and drug susceptibility was established if EC50 < 80 nM
for chloroquine base, EC50 < 40 nM for amodiaquine base, EC50 < 300 nM for
quinine base, EC50 < 15 nM for mefloquine base, EC50 < 4 nM for
halofantrine base (Brasseur et al. loc. cit., R Thor et al. 1994
Bull Epid Hebdo 38: 1-3).
Our Institut received 44 samples in 1994 and 36 samples in 1995. Twelve
samples were discarded in 1994 and 9 in 1995 (too old samples, low
parasitemia, mixed infestation with P. vivax). Therefore 32 and 26
tests were carried out in 1994 and 1995 respectively. Sixteen tests in 1994
and 5 in 1995 were not valid. The explanations are numerous: poor condition
of the sample (too old, bad cold storage), antimalarial treatment before
blood sampling, low parasitemia, etc.
The results of the 16 valid tests in 1994 and the 22 in 1995 showed that
only one isolate was susceptible to chloroquine and 100% of the isolates
were susceptible to mefloquine and halofantrine. 14% and 26% of the
isolates were resistant and intermediate respectively to quinine in 1995,
while all the isolates were susceptible in 1994. Seventeen of the 18
isolates tested were susceptible to amodiaquine. Published data concerning
the susceptibility of P. falciparum in French Guiana are not
numerous. Dedet et al. (loc. cit.) carried out in vitro tests
in French Guiana in 1988: 91% of the 32 isolates, obtained between 1983 and
1987, were resistant to chloroquine; 40% were resistant to amodiaquine and
17% resistant to quinine, while all the isolates were susceptible to
mefloquine. Gay et al. (loc. cit.) carried out in vitro tests
in 1987: the valid tests showed that 66% of 77 isolates were susceptible to
chloroquine. 96% of the isolates were susceptible to quinine and
mefloquine. Eight years later in 1995, our study showed that in
vitro resistance to chloroquine had increased: only 3% of the isolates
were susceptible. Considering this result and the increasing number of
failures of treatment with chloroquine, a consensus conference held in
Cayenne in October 1995 did not recommend chloroquine for the treatment of
falciparum malaria. Now the recommended drugs are mefloquine, halofantrine
or quinine associated with doxycycline, when these drugs are not
contra-indicated.
The different strains have been also classified according to their
origin and the stage of the disease (severe and mild cases). All the
regions where transmission occurs in French Guiana are represented.
However, most of the isolates (24 of the 38) came from the Maroni valley
and it was not possible to compare the susceptibility of the isolates
according to their origin because of the lack of collection in the other
areas of transmission. No significant difference was observed between
percentages of suceptibility to quinine in severe or mild cases. Only one
isolate was susceptible to chloroquine which came from a severe case.
Frequently, the complications of the case are not a consequence of the
antimalaria treatment failure because all the cases were rapidly cleared of
the parasites.
Further studies are under way to determine the genetics of these
strains. The strains will be compared genetically according to the results
of the in vitro tests, the severity of the cases and the origin of
the strains. On the other hand, a new survey is organized to follow the
evolution in Oyapock and Maroni valley. Self-medication at subcurative
levels with halofantrine as presumptive treatment is widespread among
gold-diggers. The Maroni valley situation can change in worse if the level
of transmission becomes higher.
Acknowledgements -
To Dr M Joubert and Dr F Rémy (Centre de Santé de Maripasoula), Dr C Penaud
and Dr F Ariey (Hopital de Sant Laurent du Maroni), Dr A Hulin and Dr D
Hommel (Centre Hospitalier General de Cayenne) for sending blood samples to
our laboratory. To Dr Chretienne (laboratoire Roussel), Dr Xerry
(laboratoire SK & F), Produits Roche for providing with amodiaquine,
halofantrine and mefloquine.
Copyright 1997 Fundacao Oswaldo Cruz
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