Pleisiomonas shigelloides bacteremia after catfish injury.

This case of Pleisimonas shigelloides bacteremia resulting after a catfish barb injury highlights an unusual presentation of a common condition that requires alternative therapy for successful treatment. An otherwise healthy male in his early 40s presented to the emergency department with sepsis and rapidly spreading cellulitis shortly after a catfish injury at a freshwater lake. His broad-spectrum antibiotics were narrowed to ciprofloxacin when P. shigelloides grew from his blood culture. The case presents a unique mode of bacteremia, as usually P. shigelloides bacteremia develops in immunocompromised hosts after bowel wall translocation. The venomous nature of catfish barbs also contributed to the severity and rapidity of his presentation secondary to the local tissue effects of envenomation. With proper antibiotics and supportive care, he made a full recovery.

Mutation in the mitochondrial tRNA(Val) causes mitochondrial encephalopathy, lactic acidosis and stroke-like episodes.

An m.1630A>G mutation in the mitochondrial tRNA(Val) (MTTV) was identified in a patient with hearing impairment, short stature and new onset of stroke. This mutation has previously been identified in a patient with the mitochondrial neurogastrointestinal encephalopathy syndrome (MNGIE). The mother of the proband also had high levels of the m.1630A>G allele present in blood and other tissues, without symptoms. To confirm the pathogenicity of this mutation, we created cybrid cell lines with various mutation loads. The m.1630A>G mutation impairs oxygen consumption, affects the stability of the MTTV and reduces the levels of subunits of the electron transport chain.

Neutral mitochondrial heteroplasmy and the influence of aging.

The development and maintenance of mitochondrial heteroplasmy has important consequences for both health and heredity. Previous studies using pathogenic mutations have shown considerable variability between maternally related individuals and studies of several D-loop polymorphisms have suggested a relationship between heteroplasmy and somatic aging. To broadly explore the variation of human heteroplasmy and to clarify the dynamics of somatic heteroplasmy over the course of lifespan, we analyzed mitochondrial sequence variation across a range of ages. We utilized array-generated single-nucleotide polymorphism data that were well correlated with independent measures of heteroplasmy. Significant levels of heteroplasmy were identified at 0.24% of sites evaluated. By examining mother-child pairs, we found that heteroplasmy was inherited (30%) but could occur de novo in offspring or, conversely, be present in mothers but eliminated in their children (70%). Cumulatively, mitochondrial heteroplasmy across the genome increased significantly with advanced age (r = 0.224, P =8 × 10(-30)). Surprisingly, changes in heteroplasmy were not uniform with some sites demonstrating a loss of variation (increased homoplasmy) with aging. These data suggest that both mutation and selective pressure affect blood mitochondrial DNA sequence over the course of the human lifespan and reveal the unexpectedly dynamic nature of human heteroplasmy.