Publications by authors named "Khalil Yousef Mohamad"

7 Publications

  • Page 1 of 1

Host adaptation of Chlamydia pecorum towards low virulence evident in co-evolution of the ompA, incA, and ORF663 Loci.

PLoS One 2014 1;9(8):e103615. Epub 2014 Aug 1.

INRA, UR1282 Infectiologie Animale et Santé Publique, Nouzilly, France.

Chlamydia (C.) pecorum, an obligate intracellular bacterium, may cause severe diseases in ruminants, swine and koalas, although asymptomatic infections are the norm. Recently, we identified genetic polymorphisms in the ompA, incA and ORF663 genes that potentially differentiate between high-virulence C. pecorum isolates from diseased animals and low-virulence isolates from asymptomatic animals. Here, we expand these findings by including additional ruminant, swine, and koala strains. Coding tandem repeats (CTRs) at the incA locus encoded a variable number of repeats of APA or AGA amino acid motifs. Addition of any non-APA/AGA repeat motif, such as APEVPA, APAVPA, APE, or APAPE, associated with low virulence (P<10-4), as did a high number of amino acids in all incA CTRs (P = 0.0028). In ORF663, high numbers of 15-mer CTRs correlated with low virulence (P = 0.0001). Correction for ompA phylogram position in ORF663 and incA abolished the correlation between genetic changes and virulence, demonstrating co-evolution of ompA, incA, and ORF663 towards low virulence. Pairwise divergence of ompA, incA, and ORF663 among isolates from healthy animals was significantly higher than among strains isolated from diseased animals (P≤10-5), confirming the longer evolutionary path traversed by low-virulence strains. All three markers combined identified 43 unique strains and 4 pairs of identical strains among all 57 isolates tested, demonstrating the suitability of these markers for epidemiological investigations.
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http://journals.plos.org/plosone/article?id=10.1371/journal.pone.0103615PLOS
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC4118914PMC
April 2015

Recent advances in the understanding of Chlamydophila pecorum infections, sixteen years after it was named as the fourth species of the Chlamydiaceae family.

Vet Res 2010 May-Jun;41(3):27. Epub 2009 Dec 10.

Institut National de la Recherche Agronomique (INRA), UR1282, Infectiologie Animale et Santé Publique, F-37380 Nouzilly (Tours), France.

Chlamydophila pecorum found in the intestine and vaginal mucus of asymptomatic ruminants has also been associated with different pathological conditions in ruminants, swine and koalas. Some endangered species such as water buffalos and bandicoots have also been found to be infected by C. pecorum. The persistence of C. pecorum strains in the intestine and vaginal mucus of ruminants could cause long-term sub-clinical infection affecting the animal's health. C. pecorum strains present many genetic and antigenic variations, but coding tandem repeats have recently been found in some C. pecorum genes, allowing C. pecorum strains isolated from sick animals to be differentiated from those isolated from asymptomatic animals. This review provides an update on C. pecorum infections in different animal hosts and the implications for animal health. The taxonomy, typing and genetic aspects of C. pecorum are also reviewed.
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http://dx.doi.org/10.1051/vetres/2009075DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC2820232PMC
June 2010

Recombinant 35-kDa inclusion membrane protein IncA as a candidate antigen for serodiagnosis of Chlamydophila pecorum.

Vet Microbiol 2010 Jul 6;143(2-4):424-8. Epub 2009 Dec 6.

Institut National de la Recherche Agronomique (INRA), UR1282, Infectiologie Animale et Santé Publique, F-37380 Nouzilly (Tours), France.

Chlamydophila pecorum strains are commonly found in the intestine and vaginal mucus of asymptomatic ruminants and may therefore induce a positive serological response when the animals are tested for C. abortus. They have also been associated with different pathological diseases in ruminants, swine and koala. The aim of this study was to identify specific C. pecorum immunodominant antigens which could be used in ELISA tests allowing to distinguish between animals infected with C. pecorum and those infected with other chlamydial species. A gene encoding 35-kDa inclusion membrane protein incA of C. pecorum was isolated by immunoscreening of the C. pecorum DNA library using ovine anti-C. pecorum antibodies. The recombinant IncA protein did not react with a murine serum directed against C. abortus but did react with a specific monoclonal antibody of C. pecorum and toward several ovine serum samples obtained after experimental infection with different C. pecorum strains. This protein could be a good candidate for specific diagnosis of C. pecorum infection.
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http://dx.doi.org/10.1016/j.vetmic.2009.11.017DOI Listing
July 2010

Zoonotic potential of Chlamydophila.

Vet Microbiol 2010 Jan 13;140(3-4):382-91. Epub 2009 Mar 13.

INRA, UR1282 Infectiologie Animale et Santé Publique, F-37380 Nouzilly, France.

The purpose of this article is to present the diseases induced in humans and animals by the different species of Chlamydophila, after providing an overview on the history of these infectious agents and their taxonomy. The route of transmission and the available methods for prevention and control in the different animal species are reviewed.
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http://dx.doi.org/10.1016/j.vetmic.2009.03.014DOI Listing
January 2010

Genotyping of Chlamydophila abortus strains by multilocus VNTR analysis.

Vet Microbiol 2009 Jun 24;137(3-4):335-44. Epub 2009 Jan 24.

Unité Zoonoses Bactériennes, Agence Française de Sécurité Sanitaire des Aliments (Lerpaz), 94706 Maisons-Alfort cedex, France.

Chlamydophila (C.) abortus is the causative agent of ovine enzootic abortion with zoonotic potential whose epidemiology has been held back because of the obligate intracellular habitat of the bacterium. In the present study, we report on a molecular typing method termed multiple loci variable number of tandem repeats (VNTR) Analysis (MLVA) for exploring the diversity of C. abortus. An initial analysis performed with 34 selected genetic loci on 34 ruminant strains including the variant Greek strains LLG and POS resulted in the identification of five polymorphic loci, confirming the widely held notion that C. abortus is a very homogeneous species. Analysis of additional 111 samples with the selected five loci resulted in the classification of all strains into six genotypes with distinct molecular patterns termed genotypes [1] through [6]. Interestingly, the classification of the isolates in the six genotypes was partly related to their geographical origin. Direct examination of clinical samples proved the MLVA to be suitable for direct typing. Analysis of the genomic sequences in six C. abortus prototypes of amplicons generated with each of the five selected VNTR primers revealed that variation between genotypes was caused by the presence or absence of coding tandem repeats in three loci. Amplification of Chlamydophila psittaci reference strains with the five selected VNTR primers and of the six C. abortus prototype strains with the eight VNTR primers established for the typing of C. psittaci [Laroucau, K., Thierry, S., Vorimore, F., Blanco, K., Kaleta, E., Hoop, R., Magnino, S., Vanrompay, D., Sachse, K., Myers, G.S., Bavoil, P.M., Vergnaud, G., Pourcel, C., 2008. High resolution typing of Chlamydophila psittaci by multilocus VNTR analysis (MLVA). Infect. Genet. Evol. 8(2), 171-181] showed that both MLVA typing systems were species-specific when all respective VNTR primer sets were used. In conclusion, the newly developed MLVA system provides a highly sensitive, high-resolution and easy-to-perform tool for the differentiation of C. abortus isolates of different origin, which is suitable for molecular epidemiological studies.
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http://dx.doi.org/10.1016/j.vetmic.2009.01.029DOI Listing
June 2009

Preliminary phylogenetic identification of virulent Chlamydophila pecorum strains.

Infect Genet Evol 2008 Dec 29;8(6):764-71. Epub 2008 Jul 29.

INRA, UR1282 Infectiologie Animale et Santé Publique, F-37380 Nouzilly, France.

Chlamydophila pecorum is an obligate intracellular bacterium associated with different pathological conditions in ruminants, swine and koala, which is also found in the intestine of asymptomatic animals. A multi-virulence locus sequence typing (MVLST) system was developed using 19 C. pecorum strains (8 pathogenic and 11 non-pathogenic intestinal strains) isolated from ruminants of different geographical origins. To evaluate the ability of MVLST to distinguish the pathogenic from the non-pathogenic strains of C. pecorum, the sequences of 12 genes were analysed: 6 potential virulence genes (ompA, incA, incB, incC, mip and copN), 5 housekeeping genes (recA, hemD, aroC, efp, gap), and the ORF663 gene encoding a hypothetical protein (HP) that includes a variant 15-nucleotides coding tandem repeat (CTR). MVLST provided high discriminatory power (100%) in allowing to distinguish 6 of 8 pathogenic strains in a single group, and overall more discriminatory than MLST targeting housekeeping genes. ompA was the most polymorphic gene and the phylogenetic tree based only on its sequence differentiated 4 groups with high bootstrap values. The number of CTRs (rich in serine, proline and lysine) in ORF663 detected in the pathogenic strains was generally lower than that found in the intestinal strains. MVLST appears to be a promising method for the differential identification of virulent C. pecorum strains, and the ompA, incA and ORF663 genes appear to be good molecular markers for further epidemiological investigation of C. pecorum.
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http://dx.doi.org/10.1016/j.meegid.2008.06.009DOI Listing
December 2008

Identification and characterisation of coding tandem repeat variants in incA gene of Chlamydophila pecorum.

Vet Res 2008 Nov-Dec;39(6):56. Epub 2008 Jul 25.

INRA, UR1282, Infectiologie Animale et Santé Publique, Centre de recherche de Tours, F-37380 Nouzilly, France.

Bacteria of the family Chlamydiaceae are obligate intracellular pathogens of human and animals. Chlamydophila pecorum is associated with different pathological conditions in ruminants, swine and koala. To characterize a coding tandem repeat (CTR) identified at the 3' end of incA gene of C. pecorum, 51 strains of different chlamydial species were examined. The CTR were observed in 18 of 18 tested C. pecorum isolates including symptomatic and asymptomatic animals from diverse geographical origins. The CTR were also found in two strains of C. abortus respectively isolated from faeces from a healthy ewe and from a goat belonging to asymptomatic herds, but were absent in C. abortus strains isolated from clinical disease specimens, and in tested strains of C. psittaci, C. caviae, C. felis and C. trachomatis. The number of CTR repeats is variable and encode several motifs that are rich in alanine and proline. The CTR-derived variable structure of incA, which encode the Chlamydiaceae-specific type III secreted inclusion membrane protein, IncA, may be involved in the adaptation of C. pecorum to its environment by allowing it to persist in the host cell.
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http://dx.doi.org/10.1051/vetres:2008032DOI Listing
January 2009
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