Browsing by Author "Fox, Thomas G."

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    Osteomyelitis of the ribs in children: a rare and potentially challenging diagnosis
    (Springer, 2020) Crone, Allison M.; Wanner, Matthew R.; Cooper, Matthew L.; Fox, Thomas G.; Jennings, S. Gregory; Karmazyn, Boaz; Radiology and Imaging Sciences, School of Medicine
    Background Rib osteomyelitis is rare in children and can mimic other pathologies. Imaging has a major role in the diagnosing rib osteomyelitis. Objective To evaluate clinical presentation and imaging findings in children with rib osteomyelitis. Materials and methods We performed a retrospective (2009–2018) study on children with rib osteomyelitis verified by either positive culture or pathology. We excluded children with multifocal osteomyelitis or empyema necessitans. We reviewed medical charts for clinical, laboratory and pathology data, and treatment. All imaging modalities for rib abnormalities were evaluated for presence and location of osteomyelitis and abscess. We calculated descriptive statistics to compare patient demographics, clinical presentation and imaging findings. Results The study group included 10 children (6 boys, 4 girls), with an average age of 7.3 years (range, 3 months to 15.9 years). The most common clinical presentations were fever (n=8) and pain (n=5). Eight children had elevated inflammatory indices (leukocytosis, erythrocyte sedimentation rate [ESR], C-reactive protein [CRP]). Localized chest wall swelling was found initially in six children and later in two more children. Rib osteomyelitis was suspected on presentation in only two children. All children had chest radiographs. Rib lytic changes were found on only one chest radiograph, in two of the four ultrasound studies, and in four of eight CTs. Bone marrow signal abnormalities were seen in all eight MRIs. In nine children the osteomyelitis involved the costochondral junction. Six children had an associated abscess. Staphylococcus aureus was cultured in eight children. Osteomyelitis was diagnosed based on pathology in one child with negative cultures. Conclusion While rib osteomyelitis is rare, imaging findings of lytic changes at the costochondral junction combined with a history of fever, elevated inflammatory markers or localized soft-tissue swelling in the chest should raise suspicion for this disease.
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    Photo Quiz: Diarrhea and Fever in a Child Returning from Africa
    (American Society for Microbiology, 2015-04) Relich, Ryan F.; Manaloor, John J.; Fox, Thomas G.; Department of Pathology and Laboratory Medicine, IU School of Medicine
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    Photo quiz: Diarrhea and fever in a child returning from Africa. Answer to photo quiz: Enteric fever
    (American Society for Microbiology, 2015-04) Relich, Ryan F.; Manaloor, John J.; Fox, Thomas G.; Department of Pathology & Laboratory Medicine, IU School of Medicine
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    Proteolytic elimination of N-myristoyl modifications by the Shigella virulence factor IpaJ
    (Springer Nature, 2013) Burnaevskiy, Nikolay; Fox, Thomas G.; Plymire, Daniel A.; Ertelt, James M.; Weigele, Bethany A.; Selyunin, Andrey S.; Way, Sing Sing; Patrie, Steven M.; Alto, Neal M.; Pediatrics, School of Medicine
    Protein N-myristoylation is a 14-carbon fatty-acid modification that is conserved across eukaryotic species and occurs on nearly 1% of the cellular proteome. The ability of the myristoyl group to facilitate dynamic protein-protein and protein-membrane interactions (known as the myristoyl switch) makes it an essential feature of many signal transduction systems. Thus pathogenic strategies that facilitate protein demyristoylation would markedly alter the signalling landscape of infected host cells. Here we describe an irreversible mechanism of protein demyristoylation catalysed by invasion plasmid antigen J (IpaJ), a previously uncharacterized Shigella flexneri type III effector protein with cysteine protease activity. A yeast genetic screen for IpaJ substrates identified ADP-ribosylation factor (ARF)1p and ARF2p, small molecular mass GTPases that regulate cargo transport through the Golgi apparatus. Mass spectrometry showed that IpaJ cleaved the peptide bond between N-myristoylated glycine-2 and asparagine-3 of human ARF1, thereby providing a new mechanism for host secretory inhibition by a bacterial pathogen. We further demonstrate that IpaJ cleaves an array of N-myristoylated proteins involved in cellular growth, signal transduction, autophagasome maturation and organelle function. Taken together, these findings show a previously unrecognized pathogenic mechanism for the site-specific elimination of N-myristoyl protein modification.