Evidence for Reductive Genome Evolution and Lateral Acquisition of Virulence Functions in Two Corynebacterium pseudotuberculosis Strains

Ruiz JC, D'Afonseca V, Silva A, et al. Evidence for Reductive Genome Evolution and Lateral Acquisition of Virulence Functions in Two Corynebacterium pseudotuberculosis Strains. PLoS ONE. 2011;6(4): e18551.Background: Corynebacterium pseudotuberculosis, a Gram-positive, facultative intracellular pathogen, is the etiologic agent of the disease known as caseous lymphadenitis (CL). CL mainly affects small ruminants, such as goats and sheep; it also causes infections in humans, though rarely. This species is distributed worldwide, but it has the most serious economic impact in Oceania, Africa and South America. Although C. pseudotuberculosis causes major health and productivity problems for livestock, little is known about the molecular basis of its pathogenicity. Methodology and Findings: We characterized two C. pseudotuberculosis genomes (Cp1002, isolated from goats; and CpC231, isolated from sheep). Analysis of the predicted genomes showed high similarity in genomic architecture, gene content and genetic order. When C. pseudotuberculosis was compared with other Corynebacterium species, it became evident that this pathogenic species has lost numerous genes, resulting in one of the smallest genomes in the genus. Other differences that could be part of the adaptation to pathogenicity include a lower GC content, of about 52%, and a reduced gene repertoire. The C. pseudotuberculosis genome also includes seven putative pathogenicity islands, which contain several classical virulence factors, including genes for fimbrial subunits, adhesion factors, iron uptake and secreted toxins. Additionally, all of the virulence factors in the islands have characteristics that indicate horizontal transfer. Conclusions: These particular genome characteristics of C. pseudotuberculosis, as well as its acquired virulence factors in pathogenicity islands, provide evidence of its lifestyle and of the pathogenicity pathways used by this pathogen in the infection process. All genomes cited in this study are available in the NCBI Genbank database (http://www.ncbi.nlm.nih.gov/genbank/) under accession numbers CP001809 and CP001829

PCR-RFLP screening of polymorphisms associated with benzimidazole resistance in Necator americanus and Ascaris lumbricoides from different geographical regions in Brazil.

Ascaris lumbricoides and Necator americanus are soil-transmitted parasites with global geographic distribution, and they represent some of the most common and neglected infections in the world. Periodic treatment with mass drug administration (MDA) in endemic areas is the recommended action put forth by the World Health Organization. However, MDA can cause the selection of subpopulations that possess the genetic ability to overcome the mechanism of drug action. In fact, beta-tubulin gene mutations (codons 167, 198 and 200) are correlated with benzimidazole resistance in nematodes of veterinary importance. It is possible that these SNPs also have strong correlation with treatment resistance in the human geohelminths A. lumbricoides, Trichuris trichiura and hookworms. Here, we aimed to investigate the presence of some of these canonical molecular markers associated with parasite resistance to benzimidazole in N. americanus and A. lumbricoides collected from six Brazilian states. Nested-PCR and PCR-RFLP were used to detect mutations at codons 167 and 198 in 601 individual eggs of A. lumbricoides collected from 62 human stool samples; however, no mutations were found. Codons 198 and 200 were tested in 552 N. americanus eggs collected from 48 patients using the same methodology, which presented a relative frequency of 1.4% and 1.1%, respectively. The presence of these SNPs in N. americanus eggs is an important finding, indicating that with high benzimidazole drug pressure there is potential for benzimidazole resistance to be selected in this hookworm. However, at these low frequencies it does not indicate that there is at present any benzimidazole resistance problem. This is the first systematic study performed in South America, and the study yielded a landscape of the genetic variants in the beta-tubulin gene and anthelmintic resistance to soil-transmitted parasites detected by a simple, rapid and affordable genotyping assay of individual eggs

Update of the Gene Discovery Program in Schistosoma mansoni with the Expressed Sequence Tag Approach

Continuing the Schistosoma mansoni Genome Project 363 new templates were sequenced generating 205 more ESTs corresponding to 91 genes. Seventy four of these genes (81%) had not previously been described in S. mansoni. Among the newly discovered genes there are several of significant biological interest such as synaptophysin, NIFs-like and rho-GDP dissociation inhibito

CBC of hamsters performed on day 50 of the experiment.

<p>(A) Hemoglobin levels are listed in grams per deciliter; (B) Global count of erythrocytes per cubic millimeter. Negative control group (NN), control infected with <i>A. ceylanicum</i> (NI), malnourished negative (MN) and malnourished infected with <i>A. ceylanicum</i> (MI). Dotted line: physiological values for hamster according Mitruka and Rawnsley (1981). n = 5/6/10/7 hamsters per group, respectively. * = P<0.05, *** = P<0.001.</p

(A) Elimination of <i>A. ceylanicum</i> eggs of per gram of feces (EPG) from the 13th DAI (days post infection) until 21 DAI.

<p>n = 6/7 hamsters per group, respectively. * = P<0.05. (B) Number of adult <i>A. ceylanicum</i> worms recovered from the small intestine of each hamster at 22 DAI. Control groups infected (NI) and malnourished infected (MI).</p

(A) Weight change in grams of the average weight of the groups of hamsters subjected to control or low-protein diet during the experiment (over 50 days); (B) Visceral adiposity index (g) after 50 days of experiment; (C) Lean body mass index (g) after 50 days of experiment.

<p>Negative control group (NN), control infected with A. ceylanicum (NI), malnourished negative (MN) and malnourished infected with <i>A. ceylanicum</i> (MI). n = 5/6/10/7 hamsters per group, respectively. * = P<0.05, ** = P<0.01.</p

Biochemical parameters in plasma of hamsters on day 50 of the experiment.

<p>(A) Total protein in grams per deciliter; (B) Albumin gram per deciliter. Negative control group (NN), control infected with <i>A. ceylanicum</i> (NI), malnourished negative (MN) and malnourished infected with A. <i>ceylanicum</i> (MI). n = 5/6/10/7 hamsters per group, respectively. * = P<0.05.</p

Lipid content on day 50 of the experiment.

<p>(A) Triglycerides in plasma in milligrams per deciliter; (B) Cholesterol in plasma gram per deciliter (C) Triglycerides in the liver milligram per gram; (D) Cholesterol in the liver in milligrams per gram; (E) Triglyceride in cecal contents milligram per gram, (F) Cholesterol in cecal contents in milligrams per gram. Negative control group (NN), control infected with <i>A. ceylanicum</i> (NI), malnourished negative (MN) and malnourished infected with <i>A. ceylanicum</i> (MI). n = 5/6/10/7 hamsters per group, respectively. * = P<0.05, ** = P<0.01, *** = P<0.001.</p

Levels of total IgG in plasma of hamsters antigens were: (A) crude extract of <i>A. ceylanicum</i>; (B) ES products.

<p>Negative control group (NN), control infected with <i>A. ceylanicum</i> (NI), malnourished negative (MN) and malnourished infected with <i>A. ceylanicum</i> (MI). Dotted line: cut-off. Plasma obtained at 22 DAI. n = 5/6/10/7 hamsters per group, respectively. ** = P<0.01.</p

Experimental design.

<p>Vertical bars indicates blood collection; Grey circle indicates start of the low protein diet; Dark circle indicates <i>A. ceylanicum</i> inoculation and Open circle indicates animal's euthanasia.</p