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Principles and practice of Clinical parasitology - Gillespie S.

Gillespie S. Principles and practice of Clinical parasitology - Wiley publishing , 2001. - 675 p.
ISBN 0-471-97729-2
Download (direct link): principlesandpracticeofclin2001.pdf
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Staining films with specific, usually monoclonal, antibodies reacting only with T. vaginalis organisms is a technique with many theoretical advantages. Initial trials were very promising (Krieger et al., 1988) and the materials were made available in kit form by a number of manufacturers; however, it is not clear how widely used the method is in routine clinical practice.
At present, culture techniques are still regarded as the most sensitive and specific; they provide the ‘gold standard’ against which other methods are judged. Media vary in efficiency but Diamond’s TYM medium (Diamond, 1957) (sometimes with minor modifications) is amongst
the best (Schmid et al., 1989; Gelbart et al.,
1990). Most tubes will be positive within 48-hours but should be kept for 7-10 days before being finally discarded. A very convenient, but expensive, way of culturing specimens is the InPouch® system, which appears to be at least as sensitive as conventional tubed media (Borchardt et al., 1997; Borchardt and Smith, 1991).
Other Diagnostic Procedures and New Developments
A number of antigen diagnostic systems have been marketed; although still not in routine use and relatively expensive, they can combine the speed of the wet film with the sensitivity of culture methods (Carney et al., 1988). Immunological methods of diagnosis have been discussed in a recent review (Ackers and Yule, 1988).
Both DNA probe- and PCR-based tests have been developed; the former technique has not found widespread acceptance, but the sensitivity PCR-based methods offer exciting new possibilities for making an accurate diagnosis on specimens obtained in less invasive ways (Witkin et al., 1996; Heine et al., 1997), including selfadministered tampons (Paterson et al., 1998).
The 5-nitroimidazole drugs were introduced in 1960 and provided the first, and so far the only, group of effective chemotherapeutic agents. Metronidazole is the prototype and by far the most widely used member of this class of drugs, all of which have similar potencies and success rates but differ somewhat in their pharmacokinetics. Doses given here are for metronidazole and should be adjusted to give the equivalent amount of other compounds. Two regimens are commonly used:
1. A 7 day course comprising either 250 mg three times a day or 500 mg twice a day.
2. A single 1.6 or 2 g dose.
The advantages of the single-dose regimen include better compliance and less interference with the normal flora, but side-effects (nausea,
Table 11.4 Some possible alternative therapies for metronidazole-resistant T. vaginalis
Compound or preparation Proportion cured Reference
Lactobacillus immunotherapy 0/2 Van der Weiden et al., 1990
Mebendazole 0/2 Pattman et al., 1989
Tinidazole 1/1, 1/1 Hamed and Studemeister, 1992; Lewis et al., 1997
Local applications:
AVC pessaries* 8/45* du Bouchet et al., 1997
Acetarsol 1/1, 1/1, 0/1, 3/3 Lewis et al., 1997; Watson and Pattman, 1996; Walker et al., 1997; Chen et al, 1999
Clotrimazole 5/45*, 0/2 Lewis et al., 1997; du Bouchet et al., 1997
Gynalgin11 7/7 Sikorski et al., 1992
Nonoxynol-9 1/1, 3/17 Livengood and Lossick, 1991; Antonelli et al., 2000
Paromomycin* 0/1, 7/9, 1/1 Lewis et al., 1997; Nyirjesy et al., 1998; Poppe, 2001
Povidone-iodine 1/1, 3/3 Wong et al., 1990; Yu and Tak Yin, 1993
Active in vitro:
Butoconazole Bouree and Issoire, 1992
Benzoizothiazolinon derivatives Ziomko and Kuczynska, 1994
Furazolidone Narcisi and Secor, 1996
Geneticin (G418) Riley and Krieger, 1996
Benzimidazoles Katiyar et al., 1994
Niridazole Yarlett et al., 1987; Hof et al., 1987
Disulfiram and ditiocarb Bouma et al., 1998
*AVC pessaries contain sulphanilamide, aminacrine HCl and allantoin. *A single oral dose of 2g metronidazole cured 36/45 cases.
^Gynalgin contains metronidazole, chloroquine and citric acid.
*High incidence of local side effects.
metallic taste, disulfiram-like reaction to alcohol) may be more noticeable. Cure rates in women are similar (about 95%) with both regimens if male sexual partners are also treated, but appear to be lower with the single-dose regimen if they are not. Only the 7 day regimen has been extensively evaluated in males, where it is just as effective as in women.
The acute toxicity of metronidazole is low, but it is a mutagen and long-term, high-dose administration to mice can produce lung tumours. Follow-up of treated women has failed to show any malignancies and any risk from short-term treatment appears to be very small. Similarly, there is no evidence that the drug is teratogenic, but it does cross the placenta and it seems only prudent to avoid its use during the first trimester if at all possible. Local treatments or simple douching have very disappointing long-term cure rates but may be of value in controlling symptoms during pregnancy until metronidazole can be used.
Treatment failures with any of the 5-nitroimi-dazole drugs are uncommon and are usually due to non-compliance. Failure to absorb the drug and inactivation by vaginal flora are other, rare causes, but a small but slowly growing proportion
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