Two temperature-sensitive (ts) strains, 1B and 1H, were obtained after nitrosoguanidine treatment of the wild-type virulent abortive ovine strain Chlamydia psittaci AB7. Optimum growth temperature on McCoy cells was 38 degrees C for the three strains, but at the restrictive temperature, 39.5 degrees C, ts strains differed from the parental strain in their total infective yield of chlamydiae, th...

The bacterial canker of kiwifruit by Pseudomonas syringae pv. actinidiae is an emblematic example of a catastrophic disease of fruit crops. In 2008 a new, extremely virulent form of the pathogen emerged and rapidly devastated many Actinidia spp. orchards all over the world. In order to understand differences in populations within this pathovar and to elucidate their diffusion and movements on w...

Contagious agalactia affects goats and sheep. In most infected sheep, the causal agent, Mycoplasma agalactiae, induces mastitis and/or agalactia, keratoconjunctivitis and arthritis. However, a few strains of M. agalactiae were isolated from tank milk from flocks without any clinical signs. The present study was undertaken to compare these apparently "asymptomatic" strains to classical virulent ...

A total of 118 fluorescent pseudomonads associated with hazelnut decline, which has been occurring for many years in different areas of northern Greece and Italy, were assessed by performing a repetitive PCR analysis with enterobacterial repetitive intergenic consensus, box element, and repetive extragenic palindromic primer sets, sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-P...

Comparison of DNA from virulent strains of bacterial pathogens with DNA from less virulent or avirulent close relatives allows the identification of those genomic regions that are present only in virulent strains. Such regions are often associated with pathogenicity islands (PIs) and their characterisation can lead to a greater understanding of the pathogenesis of infectious diseases. There is ...

Toxoplasma gondii is an opportunistic parasite with avirulent cystogenic and highly virulent non-cystogenic isolates. Although non-cystogenic strains are considered the most virulent, there are also marked genetic and virulence differences among these strains. Excretory-secretory antigens (ESAs) of T. gondii are critical for the invasion process and the immune response of the host. To better un...

Hemocytes from two adult bivalves, Pecten maximus and Crassostrea gigas, were exposed to 12 different bacterial strains including 2 Alteromonas spp. (U1 and T413), 2 type strains of vibrios (V. anguillarum ATCC 19264 and V. alginolyticus ATCC 17749), 1 vibrio (S322) pathogenic to C. gigas larvae, 2 vibrios (V110 and V117) virulent to Ostrea edulis larvae, and 5 different strains of a same Vibri...

Strains of the Beijing genotype family of Mycobacterium tuberculosis are a cause of particular concern because of their increasing dissemination in the world and their association with drug resistance. Phylogenetically, this family includes distinct ancient and modern sublineages. The modern strains, contrary to the ancestral counterparts, demonstrated increasing prevalence in many world region...