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PubMed1977

[Selenium content in the blood cattle from Venezuela. I. Central and Portugueste zones].

Whole blood concentrations of selenium were determined in 776 dairy cows and calves from 28 farms located in three States (Aragua, Carabobo and Guárico) of the central zone of Venezuela and in Portuguesa State. Selenium levels largely varied according to both the geographic distribution and animals breed. Cattle from Guárico State showed the lowest average concentration (0.21 ppm) and those from Portuguesa the highest one (0.67 ppm). A group of animals from Turén (a District of Portuguesa State) showed the highest average concentration (1.64 ppm, range 1.02 +/- to 3.24 ppm). Concentrations of this magnitude in animals under grazing conditions could be related to high levels of selenium either in the soil or in the pasture. It is concluded that such animals are localized inaseleniferous zone (Turén). It must be noted that Jaffé et al. (op. cit.) found high levels of selenium in sesame seeds (Sesamum indicum) from this area and in blood and urine samples of children from Villa Bruzual, a little town of Turén. The results of this wok significantly differ from those obtained in other countries (of Europe and North America), where animals are managed under conditions very different from those of the tropical areas like Venezuela. The role this factor is discussed. This is the first report on blood levels in large animals of economical importance in Venezuela.

Analysis of Variance↗
PubMed1997

Cycles of malaria associated with El Niño in Venezuela.

CONTEXT: Malaria has been increasing globally, and epidemics tend to occur when weather conditions favor this vector-borne disease. Long-term meteorologic forecasting using El Niño Southern Oscillation (ENSO) may assist in anticipating epidemics and targeting scarce resources. OBJECTIVE: To determine whether malaria epidemics in Venezuela are related to ENSO and rainfall and to determine whether such a relationship could be used to predict outbreaks. DESIGN: Retrospective analysis of national malaria morbidity (1975-1995) and mortality (1910-1935) data in the coastal zone and interior of Venezuela in relation to El Niño events and rainfall. MAIN OUTCOME MEASURE: Correlation between malaria mortality and morbidity and sea surface temperatures (SSTs) in the Eastern Tropical Pacific, a parameter of ENSO. RESULTS: Malaria mortality and morbidity have increased by an average of 36.5% (95% confidence interval, 3.7%-69.3%; P=.004) in years following recognized El Niño events. A moderate correlation was found between Pacific tropical SST during a Niño event and malaria 1 year later (r=0.50, P<.001). Malaria mortality is more strongly related to drought in the year preceding outbreaks than to rainfall during epidemic years. CONCLUSIONS: Historic and recent data from Venezuela demonstrate that malaria increases by an average of about one third in the year following a Nino event; change in malaria risk can be predicted from Pacific SSTs in the previous year. Therefore, the occurrence of an El Niño event may help predict malaria epidemics in this part of South America.

Disease Outbreaks↗
PubMed2006

Heterologous expression of tylosin polyketide synthase and production of a hybrid bioactive macrolide in Streptomyces venezuelae.

Tylosin polyketide synthase (Tyl PKS) was heterologously expressed in an engineered strain of Streptomyces venezuelae bearing a deletion of pikromycin PKS gene cluster using two compatible low-copy plasmids, each under the control of a pikAI promoter. The mutant strain produced 0.5 mg/l of the 16-membered ring macrolactone, tylactone, after a 4-day culture, which is a considerably reduced culture period to reach the maximum production level compared to other Streptomyces hosts. To improve the production level of tylactone, several precursors for ethylmalonyl-CoA were fed to the growing medium, leading to a 2.8-fold improvement (1.4 mg/ml); however, switching the pikAI promoter to an actI promoter had no observable effect. In addition, a small amount of desosamine-glycosylated tylactone was detected from the extract of the mutant strain, revealing that the native glycosyltransferase DesVII displayed relaxed substrate specificity in accepting the 16-membered ring macrolactone to produce the glycosylated tylactone. These results demonstrate a successful attempt for a heterologous expression of Tyl PKS in S. venezuelae and introduce S. venezuelae as a rapid heterologous expression system for the production of secondary metabolites.

Anti-Bacterial Agents↗
PubMed2002

Generation of multiple bioactive macrolides by hybrid modular polyketide synthases in Streptomyces venezuelae.

The plasmid-based replacement of the multifunctional protein subunits of the pikromycin PKS in S. venezuelae by the corresponding subunits from heterologous modular PKSs resulted in recombinant strains that produce both 12- and 14-membered ring macrolactones with predicted structural alterations. In all cases, novel macrolactones were produced and further modified by the DesVII glycosyltransferase and PikC hydroxylase, leading to biologically active macrolide structures. These results demonstrate that hybrid PKSs in S. venezuelae can produce a multiplicity of new macrolactones that are modified further by the highly flexible DesVII glycosyltransferase and PikC hydroxylase tailoring enzymes. This work demonstrates the unique capacity of the S. venezuelae pikromycin pathway to expand the toolbox of combinatorial biosynthesis and to accelerate the creation of novel biologically active natural products.

Amino Acid Sequence↗
PubMed1998

Hydroxylation of macrolactones YC-17 and narbomycin is mediated by the pikC-encoded cytochrome P450 in Streptomyces venezuelae.

BACKGROUND: . Streptomyces venezuelae produces two groups of antibiotics that include the 12-membered ring macrolides methymycin and neomethymycin, and the 14-membered ring macrolide pikromycin. Methymycin and pikromycin are derived from the corresponding precursors, YC-17 and narbomycin, respectively, by hydroxylation of the tertiary carbon position (C-10 in YC-17 or C-12 in narbomycin) on the macrolactone ring. In contrast, neomethymycin is derived from YC-17 by hydroxylation of the secondary carbon (C-12) of the propionyl starter unit sidechain. RESULTS: . Using a genetic and biochemical approach we have characterized a single P450 hydroxylase (PikC) in the methymycin/pikromycin biosynthetic gene cluster (pik) from S. venezuelae. Inactivation of pikC abolished production of all hydroxylated macrolides, with corresponding accumulation of YC-17 and narbomycin in the culture medium. The enzyme was produced efficiently and purified as a His-tagged protein from recombinant Escherichia coli cells. Purified PikC effectively converts YC-17 into methymycin and neomethymycin and narbomycin into pikromycin in vitro. CONCLUSIONS: . These results demonstrate that PikC is responsible for the conversion of YC-17 to methymycin and neomethymycin, and narbomycin to pikromycin in S. venezuelae. This substrate flexibility is unique and represents the first example of a P450 hydroxylase that can accept 12- and 14-membered ring macrolides as substrates, as well as functionalize at two positions on the macrolactone system. The broad substrate specificity of PikC provides a potentially valuable entry into the construction of novel macrolide- and ketolide-based antibiotics.

Amino Acid Sequence↗
PubMed1995

Inactivation of chloramphenicol by O-phosphorylation. A novel resistance mechanism in Streptomyces venezuelae ISP5230, a chloramphenicol producer.

Plasmid pJV4, containing a 2.4-kilobase pair insert of genomic DNA from the chloramphenicol (Cm) producer Streptomyces venezuelae ISP5230, confers resistance when introduced by transformation into the Cm-sensitive host Streptomyces lividans M252 (Mosher, R. H. Ranade, N. P., Schrempf, H., and Vining, L. C. (1990) J. Gen. Microbiol. 136, 293-301). Transformants rapidly metabolized Cm to one major product, which was isolated and purified by reversed phase chromatography. The metabolite was identified by nuclear magnetic resonance spectroscopy and mass spectrometry as 3'-O-phospho-Cm, and was shown to have negligible inhibitory activity against Cm-sensitive Micrococcus luteus. The nucleotide sequence of the S. venezuelae DNA insert in pJV4 contains an open reading frame (ORF) that encodes a polypeptide (19 kDa) with a consensus motif at its NH2 terminus corresponding to a nucleotide-binding amino acid sequence (motif A or P-loop; Walker, J. E., Saraste, M., Runswick, M. J., and Gay, N. J. (1982) EMBO J. 1, 945-951). When a recombinant vector containing this ORF as a 1.6-kilobase pair SmaI-SmaI fragment was used to transform S. lividans M252, uniformly Cm-resistant transformants were obtained. A strain of S. lividans transformed by a vector in which the ORF had been disrupted by an internal deletion yielded clones that were unable to phosphorylate Cm, and exhibited normal susceptibility to the antibiotic. The results implicate the product of the ORF from S. venezuelae as an enzymic effector of Cm resistance in the producing organism by 3'-O-phosphorylation. We suggest the trivial name chloramphenicol 3'-O-phosphotransferase for the enzyme.

Amino Acid Sequence↗
PubMed1986

Conjugational fertility and location of chloramphenicol biosynthesis genes on the chromosomal linkage map of Streptomyces venezuelae.

In Streptomyces venezuelae fertility, defined as chromosomal gene recombination, was enhanced over 1000-fold when one parent in a biparental conjugational cross lacked the physically-undetected plasmid SVP1, as compared with crosses in which both parents carried SVP1. The existence of SVP1 and at least two other fertility plasmids, SVP2 and SVP3, was detected in S. venezuelae by 'lethal zygosis' elicited by a plasmid-plus mycelium in contact with a plasmid-minus mycelium. Conjugational crosses were used to construct a linkage map of S. venezuelae which was highly consistent with the map of analogous loci in S. coelicolor A3(2). A cluster of genes governing chloramphenicol biosynthesis was located near arg, cys and pdxB genes at a position roughly equivalent to the 1-2 o'clock region of the S. coelicolor A3(2) map.

Chloramphenicol↗
PubMed1990

Chloramphenicol resistance in Streptomyces: cloning and characterization of a chloramphenicol hydrolase gene from Streptomyces venezuelae.

A 6.5 kb DNA fragment containing a chloramphenicol-resistance gene of Streptomyces venezuelae ISP5230 was cloned in Streptomyces lividans M252 using the high-copy-number plasmid vector pIJ702. The gene was located within a 2.4 kb KpnI-SstI fragment of the cloned DNA and encoded an enzyme (chloramphenicol hydrolase) that catalysed removal of the dichloroacetyl moiety from the antibiotic. The deacylated product, p-nitrophenylserinol, was metabolized to p-nitrobenzyl alcohol and other compounds by enzymes present in S. lividans M252. Examination of the genomic DNA from several sources using the cloned 6.5 kb SstI fragment from S. venezuelae ISP5230 as a probe showed a hybridizing region in the DNA from S. venezuelae 13s but none in the DNA from another chloramphenicol producer, Streptomyces phaeochromogenes NRRLB 3559. The resistance phenotype was not expressed when the 6.5 kb SstI fragment or a subfragment was subcloned behind the lac-promoter of plasmid pTZ18R in Escherichia coli.

Amidohydrolases↗
PubMed1990

Sporulation of Streptomyces venezuelae in submerged cultures.

Shaken cultures of Streptomyces venezuelae ISP5230 in minimal medium with galactose and ammonium sulphate as carbon and nitrogen sources, respectively, showed extensive sporulation after 72 h incubation at 37 degrees C. The spores formed in these cultures resembled aerial spores in their characteristics. The ability of the spores to withstand lysozyme treatment was used to monitor the progress of sporulation in cultures and to determine the physiological requirements for sporulation. In media containing ammonium sulphate as the nitrogen source, galactose was the best of six carbon sources tested. With galactose S. venezuelae ISP5230 sporulated when supplied with any of several nitrogen sources; however, an excess of nitrogen source was inhibitory. In cultures containing galactose and ammonium sulphate, sporulation was suppressed by a peptone supplement. The onset of sporulation was accompanied by a drop in intracellular GTP content. When decoyinine, an inhibitor of GMP synthase, was added to a medium containing starch and ammonium sulphate, a slight increase in sporulation was seen after 2 d. The suppression of sporulation by peptone in liquid or agar cultures was not reversed by addition of decoyinine. A hypersporulating mutant of S. venezuelae ISP5230 was altered in its ability to assimilate sugars. In cultures containing glucose the mutant sporulated more profusely than did the wild-type and did not acidify the medium to the same extent. However, the suppressive effect of glucose on sporulation was not merely a secondary result of acid accumulation.

Adenosine↗
PubMed2001

Cloning and functional analysis of a phosphopantetheinyl transferase superfamily gene associated with jadomycin biosynthesis in Streptomyces venezuelae ISP5230.

Sequence analysis of a XhoI/SacI fragment of chromosomal DNA downstream of jadL in the Streptomyces venezuelae ISP5230 gene cluster for jadomycin biosynthesis detected a partial ORF similar in its deduced amino acid sequence to the hetI product involved in synthesizing a regulator of heterocyst spacing in ANABAENA: By probing a phage library of S. venezuelae DNA with the XhoI/SacI fragment, the authors identified and isolated a hybridizing clone. The nucleotide sequence of its DNA contained three complete ORFs (jadM, N and X) and one incomplete ORF (jadO). The jadM ORF lay immediately downstream of, and partially overlapped, jadL. It contained 786 nucleotides encoding an amino acid sequence like those of enzymes in the phosphopantetheinyl transferase family. The jadN ORF contained 1794 nucleotides and encoded an amino acid sequence resembling acyl-CoA decarboxylases, thus suggesting a role in polyketide condensation reactions. The jadX ORF was not identified, but the partial jadO showed marked similarities in its deduced amino acid sequence to NDP-hexose-2,3-dehydratases, indicating a role in forming the sugar component of jadomycin B. Expression of jadM in Escherichia coli and examination of the product by SDS-PAGE established that the ORF encoded a 29.1 kDa protein, corresponding in size to the 262 amino acid polypeptide deduced from the jadM sequence. Evidence from a Northern hybridization indicated that jadM expression is correlated with jadomycin B synthesis. Cultures of S. venezuelae ISP5230 disrupted in jadM produced only 2-5% of the wild-type titre of jadomycin B, but grew well and produced chloramphenicol normally. The authors conclude that jadM encodes a holo-ACP synthase needed primarily for jadomycin B biosynthesis.

Amino Acid Sequence↗
PubMed2002

Biosynthesis of the dideoxysugar component of jadomycin B: genes in the jad cluster of Streptomyces venezuelae ISP5230 for L-digitoxose assembly and transfer to the angucycline aglycone.

Eight additional genes, jadX, O, P, Q, S, T, U and V, in the jad cluster of Streptomyces venezuelae ISP5230, were located immediately downstream of jadN by chromosome walking. Sequence analyses and comparisons implicated them in biosynthesis of the 2,6-dideoxysugar in jadomycin B. The genes were cloned in Escherichia coli, inactivated by inserting an apramycin resistance cassette with a promoter driving transcription of downstream genes, and transferred into Streptomyces venezuelae by intergeneric conjugation. Analysis by HPLC and NMR of intermediates accumulated by cultures of the insertionally inactivated Streptomyces venezuelae mutants indicated that jadO, P, Q, S, T, U and V mediate formation of the dideoxysugar moiety of jadomycin B and its attachment to the aglycone. Based on these results and sequence similarities to genes described in other species producing deoxysugar derivatives, a biosynthetic pathway is proposed in which the jadQ product (glucose-1-phosphate nucleotidyltransferase) activates glucose to its nucleotide diphosphate (NDP) derivative, and the jadT product (a 4,6-dehydratase) converts this to NDP-4-keto-6-deoxy-D-glucose. An NDP-hexose 2,3-dehydratase and an oxidoreductase, encoded by jadO and jadP, respectively, catalyse ensuing reactions that produce an NDP-2,6-dideoxy-D-threo-4-hexulose. The product of jadU (NDP-4-keto-2,6-dideoxy-5-epimerase) converts this intermediate to its L-erythro form and the jadV product (NDP-4-keto-2,6-dideoxyhexose 4-ketoreductase) reduces the keto group of the NDP-4-hexulose to give an activated form of the L-digitoxose moiety in jadomycin B. Finally, a glycosyltransferase encoded by jadS transfers the activated sugar to jadomycin aglycone. The function of jadX is unclear; the gene is not essential for jadomycin B biosynthesis, but its presence ensures complete conversion of the aglycone to the glycoside. The deduced amino acid sequence of a 612 bp ORF (jadR*) downstream of the dideoxysugar biosynthesis genes resembles many TetR-family transcriptional regulator sequences.

Amino Acid Sequence↗
PubMed2004

Biosynthesis of the dichloroacetyl component of chloramphenicol in Streptomyces venezuelae ISP5230: genes required for halogenation.

Five ORFs were detected in a fragment from the Streptomyces venezuelae ISP5230 genomic DNA library by hybridization with a PCR product amplified from primers representing a consensus of known halogenase sequences. Sequencing and functional analyses demonstrated that ORFs 11 and 12 (but not ORFs 13-15) extended the partially characterized gene cluster for chloramphenicol (Cm) biosynthesis in the chromosome. Disruption of ORF11 (cmlK) or ORF12 (cmlS) and conjugal transfer of the insertionally inactivated genes to S. venezuelae gave mutant strains VS1111 and VS1112, each producing a similar series of Cm analogues in which unhalogenated acyl groups replaced the dichloroacetyl substituent of Cm. 1H-NMR established that the principal metabolite in the disrupted strains was the alpha-N-propionyl analogue. The sequence of CmlK implicated the protein in adenylation, and involvement in halogenation was inferred from biosynthesis of analogues by the cmlK-disrupted mutant. A role in generating the dichloroacetyl substituent was supported by partial restoration of Cm biosynthesis when a cloned copy of cmlK was introduced in trans into VS1111. Complementation of the mutant also indicated that inactivation of cmlK rather than a polar effect of the disruption on cmlS expression had interfered with dichloroacetyl biosynthesis. The deduced CmlS sequence resembled sequences of FADH2-dependent halogenases. Conjugal transfer of cmlK or cmlS into S. venezuelae cml-2, a chlorination-deficient strain with a mutation mapped genetically to the Cm biosynthesis gene cluster, did not complement the cml-2 lesion, suggesting that one or more genes in addition to cmlK and cmlS is needed to assemble the dichloroacetyl substituent. Insertional inactivation of ORF13 did not affect Cm production, and the products of ORF14 and ORF15 matched Streptomyces coelicolor A3(2) proteins lacking plausible functions in Cm biosynthesis. Thus cmlS appears to mark the downstream end of the gene cluster.

Amino Acid Sequence↗
PubMed1994

Cloning and sequence analysis of a recA-like gene from Streptomyces venezuelae ISP5230.

When genomic DNA fragments from Streptomyces venezuelae ISP5230 were probed at moderate stringency with recA from Mycobacterium tuberculosis, a 2.0-kb SmaI fragment was identified. The fragment was isolated by cloning a BamHI digest of S. venezuelae DNA in pHJL400 and screening the plasmids in Escherichia coli by Southern hybridization using a sib-selection technique. Sequencing the hybridizing region located an open reading frame encoding 377 amino acids. Its deduced amino acid sequence resembled that of recA genes from other bacteria. The cloned S. venezuelae gene conferred partial resistance to ethyl methanesulfonate when expressed in E. coli from the lacZ promoter.

Amino Acid Sequence↗
PubMed2001

Characterization and analysis of the PikD regulatory factor in the pikromycin biosynthetic pathway of Streptomyces venezuelae.

The Streptomyces venezuelae pikD gene from the pikromycin biosynthetic cluster was analyzed, and its deduced product (PikD) was found to have amino acid sequence homology with a small family of bacterial regulatory proteins. Database comparisons revealed two hypothetical domains, including an N-terminal triphosphate-binding domain and a C-terminal helix-turn-helix DNA-binding motif. Analysis of PikD was initiated by deletion of the corresponding gene (pikD) from the chromosome of S. venezuelae, resulting in complete loss of antibiotic production. Complementation by a plasmid carrying pikD restored macrolide biosynthesis, demonstrating that PikD is a positive regulator. Mutations were made in the predicted nucleotide triphosphate-binding domain, confirming the active-site amino acid residues of the Walker A and B motifs. Feeding of macrolide intermediates was carried out to gauge the points of operon control by PikD. Although the pikD mutant strain was unable to convert macrolactones (10-deoxymethynolide and narbonolide) to glycosylated products, macrolide intermediates (YC-17 and narbomycin) were hydroxylated with high efficiency. To study further the control of biosynthesis, presumed promoter regions from pik cluster loci were linked to the xylE reporter and placed in S. venezuelae wild-type and pikD mutant strains. This analysis demonstrated that PikD-mediated transcriptional regulation occurs at promoters controlling expression of pikRII, pikAI, and desI but not those controlling pikRI or pikC.

Amino Acid Sequence↗
PubMed1964

Purification of Streptomyces venezuelae phage.

Kolstad, R. A. (University of Minnesota, Minneapolis), and S. G. Bradley. Purification of Streptomyces venezuelae phage. J. Bacteriol. 87:1157-1161. 1964.-Streptomyces venezuelae phage MSP8 was concentrated and purified by a combination of methods including dialysis against polyethylene glycol, partitioning between the two phases of aqueous polymer systems, gel filtration, chromatography on ECTEOLA-cellulose, and differential centrifugation. S. venezuelae phage MSP8 is 57% deoxyribonucleic acid and 43% protein. Its head is 55 by 70 mmu, and its tail is 10 by 150 mmu. Its dry weight is 250 mg per 10(15) plaqueforming units, and its density is 1.4. Phage MSP8 contains 15 mug of phosphorus and 40 mug of nitrogen per 10(12) particles. The ratio of light absorbancy at 260 to 280 mmu is 1.5. A mixture of two actinophages, MNP3 and MVP7, was separated by use of ECTEOLA-cellulose. In one fraction, 99% of the phage was MNP3; in another fraction, 99% of the phage was MVP7.

Bacteriophages↗
PubMed2001

Molecular and antigenic comparison of Ehrlichia canis isolates from dogs, ticks, and a human in Venezuela.

We previously culture isolated a strain of Ehrlichia canis, the causative agent of canine ehrlichiosis, from a human in Venezuela. In the present study, we examined whether dogs and ticks are infected with E. canis in Venezuela and, if so, whether this is the same strain as the human isolate. PCR analysis using E. canis-specific primers revealed that 17 of the 55 dog blood samples (31%) and all three pools of four Rhipicephalus sanguineus ticks each were positive. An ehrlichial agent (Venezuelan dog Ehrlichia [VDE]) was isolated and propagated in cell culture from one dog sample and was further analyzed to determine its molecular and antigenic characteristics. The 16S rRNA 1,408-bp sequence of the new VDE isolate was identical to that of the previously reported Venezuelan human Ehrlichia isolate (VHE) and was closely related (99.9%) to that of E. canis Oklahoma. The 5' (333-bp) and 3' (653-bp) sequences of the variable regions of the 16S rRNA genes from six additional E. canis-positive dog blood specimens and from three pooled-tick specimens were also identical to those of VHE. Western blot analysis of serum samples from three dogs infected with VDE by using several ehrlichial antigens revealed that the antigenic profile of the VDE was similar to the profiles of VHE and E. canis Oklahoma. Identical 16S rRNA gene sequences among ehrlichial organisms from dogs, ticks, and a human in the same geographic region in Venezuela and similar antigenic profiles between the dog and human isolates suggest that dogs serve as a reservoir of human E. canis infection and that R. sanguineus, which occasionally bites humans residing or traveling in this region, serves as a vector. This is the first report of culture isolation and antigenic characterization of an ehrlichial agent from a dog in South America, as well as the first molecular characterization of E. canis directly from naturally infected ticks.

Animals↗
PubMed2005

The detection and PCR-based characterization of the parasites causing trypanosomiasis in water-buffalo herds in Venezuela.

The usefulness of PCR-based assays for detecting trypanosomiasis in water buffaloes and other livestock was explored, under field conditions, in Venezuela. The sensitivity and specificity of the assays, which were based on established primer pairs (21-mer/22-mer and ILO1264/ILO1265), were evaluated, partly by comparison with the results of parasitological tests (stained bloodsmears and microhaematocrit centrifugation) and immunological assays (IFAT) run in parallel. The optimised PCR-based assays showed a sensitivity of 10 pg DNA. The use of the 21-mer/22-mer primer pair gave a test that was specific for species in the subgenus Trypanozoon (including Trypanosoma evansi), whereas use of ILO1264/ILO1265 produced a test that was specific for T. vivax. The results of a hybridization assay using T. evansi-DNA and T. vivax-DNA probes indicated no cross-hybridization between the T. evansi and T. vivax PCR products.The results of the bloodsmear examinations, microhaematocrit centrifugations (MHC) and IFAT indicated that 23 (6.7%), 39 (11.4%) and 135 (39.5%) of the 342 blood samples investigated (including 316 from water buffaloes) contained trypanosomes, respectively. The results of the PCR-based assays indicated that 68 (19.9%) of the same blood samples contained T. vivax (or at least T. vivax DNA), and that none contained T. evansi or any other member of the subgenus Trypanozoon. For the detection of trypanosomes, the assay therefore appeared almost twice as sensitive as the MHC. These results are the first on the molecular characterization of the trypanosomes infecting water buffaloes in Venezuela. When the results of the MHC (which is the most practical, and frequently used, alternative detection method) were used as the gold standard, the PCR-based assay for T. vivax was found to have 100% sensitivity, 90.4% specificity, a positive predictive value of 0.57, a positive likelihood ratio of 10.45, and a negative likelihood ratio of 0.00. The assay therefore appears a reasonable choice for detecting T. vivax in the mammalian livestock of Venezuela and elsewhere.

Animals↗
PubMed1998

[Mortality trends for acute rheumatic fever and chronic rheumatic heart disease in Venezuela, 1955-1994]

This study reports on deaths due to acute rheumatic fever (ARF) and chronic rheumatic heart disease (CRHD) in Venezuela from 1955 to 1994. Census publications and other official sources provide the population data. Yearly age -and sex- specific mortality rates per 100,000 inhabitants were calculated and adjusted by the direct method to the WHO's standard population. The RF-adjusted mortality rate (AMR) declined: total from 7.68 to 1.08 (-85.9%); male from 7.53 to 0.84 (-88.8%); and female from 7.83 to 1.33 (-83.0%). In all cases female RF-AMRs were higher than male. There was a reduction of 88.5% in the ratio of RF deaths to cardiovascular deaths (ICD-6330-334,400-447; ICD-7330-334,400-447; ICD-8 390-438; ICD-9 390-438). ARF-AMR declined (-93.5%) as did CRHD-AMR (-85.1%). Proportional death by ARF and CRHD in patients 45 years old and younger increased. Venezuela experienced a continuous decline in RF-AMR from 1955 to the l980s, followed by a period of stabilization lasting until l994. The reduction could be the consequence of improvement in socioeconomic status and of RF prevention with penicillin, a standard practice in the health care system. The 1980s and 1990s RF-AMR stabilization could be associated with economic setbacks in Venezuela and changes in the agent's virulence patterns.

Journal Article↗