Optimization of random amplified polymorphic DNA techniques for its use in genetic studies of Trichomonas vaginalis isolates

Mycoplasma hominis in Cuban Trichomonas vaginalis isolates: association with parasite genetic polymorphism

Trichomonas vaginalis can be naturally infected with intracellular Mycoplasma hominis. This bacterial infection may have implications for trichomonal virulence and disease pathogenesis. The objective of the study was to report the presence of M. hominis in Cuban T. vaginalis isolates and to describe the association between the phenotype M. hominis infected with RAPD genetic polymorphism of T. vaginalis. The Random Amplified Polymorphic DNA (RAPD) technique was used to determine genetic differences among 40 isolates of T. vaginalis using a panel of 30 random primers and these genetic data were correlated with the infection of isolates with M. hominis. The trees drawn based on RAPD data showed no relations with metronidazole susceptibility and significantly association with the presence of M. hominis (P=0.043), which demonstrates the existence of concordance between the genetic relatedness and the presence of M. hominis in T. vaginalis isolates. This result could point to a predisposition of T. vaginalis for the bacterial enters and/or survival.

Molecular typing of the actin gene of Trichomonas vaginalis isolates by PCR-restriction fragment length polymorphism

Human trichomoniasis, caused by the protozoan Trichomonas vaginalis, is a highly prevalent sexually transmitted infection. However, little is known about the degree of strain variability of T. vaginalis. A reliable classification method for T. vaginalis strains would be a useful tool in the study of the epidemiology, pathogenesis and transmission of T. vaginalis. A PCR-restriction fragment length polymorphism typing method was designed and evaluated using T. vaginalis isolates obtained after culture of vaginal specimens collected in the Democratic Republic of Congo and in Zambia. The variation of the actin gene of T. vaginalis was determined for three ATCC reference strains and 151 T. vaginalis isolates. Eight different types were identified, on the basis of the digestion patterns of the amplified actin gene, with each of the restriction enzymes HindII, MseI and RsaI. It was determined that the ATCC reference strains 30001, 30240 and 50141 were of actin genotypes G, H and E, respectively. The actin genotype type E was more common in the Democratic Republic of Congo, whereas type G was the commonest type in Zambia. Translation of the nucleotide sequence showed up to three amino acid substitutions. We developed a reproducible, sensitive and specific typing method for T. vaginalis, and were able to distinguish at least eight T. vaginalis actin genotypes. Further studies are needed to evaluate the method using clinical specimens and to determine the utility of the typing method for the genotypic characterization of T. vaginalis.

PCR fingerprinting of Blastocystis isolated from symptomatic and asymptomatic human hosts

Genomic DNA from 16 Blastocystis hominis isolates comprising of eight asymptomatic isolates (A1-A8) and eight symptomatic isolates (S1-S8) was amplified by arbitrarily primed polymerase chain reaction (AP-PCR) using 38 arbitrary 10-mer primers. Six primers (A10, B5, C20, D1, F6, and F10) generated reproducible DNA fingerprints. AP-PCR amplification revealed similar DNA fingerprints among all symptomatic isolates (S1-S8) with common bands at 850 bp using primer A10, 920 bp using primer B5, and 1.3 kbp using primer D1. Isolates A1, A3, A4, A5, A6, and A7 showed similar DNA banding patterns and all asymptomatic isolates (A1-A8) shared a major band at 1 kbp using primer B5. Isolates A2 and A8 showed distinct DNA banding patterns that differed from the remainder of the isolates. The results of the phylogenetic analyses showed that all symptomatic isolates (S1-S8) formed a clade with >70% similarity among the isolates and which were clearly separate from asymptomatic isolates A1, A3, A4, A5, A6, and A7. Asymptomatic isolates A2 and A8 formed two distinct and separate clades. AP-PCR revealed higher genetic variability within the asymptomatic isolates than within the symptomatic isolates. The present study suggests that AP-PCR can be a valuable method for differentiating between isolates of B. hominis and our results support the hypothesis that our asymptomatic and symptomatic B. hominis isolates may represent two different strains/species with varying pathogenic potential.

Optimization of random amplified polymorphic DNA techniques for use in genetic studies of Cuban triatominae

Random amplified polymorphic DNA (RAPD) technique is a simple and reliable method to detect DNA polymorphism. Several factors can affect the amplification profiles, thereby causing false bands and non-reproducibility of assay. In this study, we analyzed the effect of changing the concentration of primer, magnesium chloride, template DNA and Taq DNA polymerase with the objective of determining their optimum concentration for the standardization of RAPD technique for genetic studies of Cuban Triatominae. Reproducible amplification patterns were obtained using 5 pmoL of primer, 2.5 mM of MgCl2, 25 ng of template DNA and 2 U of Taq DNA polymerase in 25 µL of the reaction. A panel of five random primers was used to evaluate the genetic variability of T. flavida. Three of these (OPA-1, OPA-2 and OPA-4) generated reproducible and distinguishable fingerprinting patterns of Triatominae. Numerical analysis of 52 RAPD amplified bands generated for all five primers was carried out with unweighted pair group method analysis (UPGMA). Jaccard's Similarity Coefficient data were used to construct a dendrogram. Two groups could be distinguished by RAPD data and these groups coincided with geographic origin, i.e. the populations captured in areas from east and west of Guanahacabibes, Pinar del Río. T. flavida present low interpopulation variability that could result in greater susceptibility to pesticides in control programs. The RAPD protocol and the selected primers are useful for molecular characterization of Cuban Triatominae.

The use of RAPD in ecotoxicology

Toxic compounds may interfere with the genetic constitution of populations, either directly through mutagenic activity, or indirectly via population-mediated processes (i.e. selection, bottleneck). These processes are initiated when toxic compounds reduce the survival and/or fecundity of exposed organisms, either through the accumulation of unfavorable mutations or when they adversely affect the physiology of an organism and/or the environment in which it has to survive. In this review, we describe how the RAPD technique can be applied in an ecotoxicological context, providing information on all direct and indirect routes through which toxicants may affect the genetic structure of populations. Based on RAPD band intensity, gain/loss and band numbers, three major types of RAPD fingerprint analyses are discussed, yielding diagnostic, phenetic and genetic information. Ecotoxicological literature examples demonstrate that, under strictly standardized conditions, the RAPD technique can be a useful tool to preliminary assess toxicological population genetic effects, particularly since this technique is relatively inexpensive and yields information on a large number of loci without having to obtain sequence data for primer design. However, currently only a small fraction of its potential is used in ecotoxicology. Statistical tools and parameters, as used in other RAPD studies, should be applied in ecotoxicological research as well in order to fully exploit the potential of this technique. Finally, due to their random nature, RAPD data often must be considered as preliminary until they are further documented by cloning, sequencing and probing techniques.

Genetic variability between Trichomonas vaginalis isolates and correlation with clinical presentation

The random amplified polymorphic DNA (RAPD) technique was used to determine genetic differences among isolates of Trichomonas vaginalis and these genetic data were correlated with patient records. A panel of 10 random primers was used to determine the type and extent of intraspecific polymorphism in 40 isolates of T. vaginalis. All primers detected DNA polymorphism among isolates. Numerical analysis of 124 RAPD amplified bands generated by these 10 primers were carried out with the unweighted pair group methods analysis (UPGMA) using Jaccard's Similarity Coefficient and data were used to construct a dendrogram. Four main groups can be distinguished by RAPD data, these groups coincide with four different patient categories (asymptomatic and symptomatic: light, moderate, and severe infection). These patients did not have any concomitant vaginal infection. Each of the four groups can be characterized by specific genetic markers, but a specific 490bp marker was found to be specific for all symptomatic isolates, not the asymptomatic isolates. This is the first description of a possible virulence marker for T. vaginalis. Further studies will be necessary to ascertain the importance and function of this genetic marker in clinical infection.