Hypothalamic-pituitary-adrenal axis in lethal canine Staphylococcus aureus pneumonia

The clinical significance and even existence of critical illness-related corticosteroid insufficiency is controversial. Here, hypothalamic-pituitary-adrenal (HPA) function was characterized in severe canine Staphylococcus aureus pneumonia. Animals received antibiotics and titrated life-supportive measures. Treatment with dexamethasone, a glucocorticoid, but not desoxycorticosterone, a mineralocorticoid, improves outcome in this model. Total and free cortisol, adrenocorticotropic hormone (ACTH). and aldosterone levels, as well as responses to exogenous ACTH were measured serially. At 10 h after the onset of infection, the acute HPA axis stress response, as measured by cortisol levels, exceeded that seen with high-dose ACTH stimulation but was not predictive of outcome. In contrast to cortisol, aldosterone was largely autonomous from HPA axis control, elevated longer, and more closely associated with survival in early septic shock. Importantly, dexamethasone suppressed cortisol and ACTH levels and restored ACTH responsiveness in survivors. Differing strikingly, nonsurvivors, sepsis-induced hypercortisolemia, and high ACTH levels as well as ACTH hyporesponsiveness were not influenced by dexamethasone. During septic shock, only serial measurements and provocative testing over a well-defined timeline were able to demonstrate a strong relationship between HPA axis function and prognosis. HPA axis unresponsiveness and high aldosterone levels identify a septic shock subpopulation with poor outcomes that may have the greatest potential to benefit from new therapies.

Toxic shock syndrome in a horse with Staphylococcus aureus pneumonia

A 3-year-old Thoroughbred gelding was examined because of clinical signs of pneumonia and shock. Mucous membrane petechiation and ventral edema were observed and considered to be a result of vasculitis. Epidermal necrosis developed on the distal portions of the limbs. The horse had a persistent high fever that was unresponsive to nonsteroidal anti-inflammatory treatment, and Staphylococcus aureus was isolated from a nasal swab specimen and 2 transtracheal wash fluid samples. Antimicrobial, anti-inflammatory, and supportive treatment resulted in clinical improvement. However, resolution of the pulmonary infection required long-term (42 days) antimicrobial administration. Staphylococcus aureus strains isolated from this horse were positive for the toxic shock syndrome toxin-1 gene and were shown to produce toxic shock syndrome toxin-1, the causative factor in toxic shock syndrome in humans. The horse's clinical signs were attributed to toxic shock syndrome secondary to pulmonary S. aureus infection.

Staphylococcus aureus pneumonia in turkey poults with gross lesions resembling aspergillosis

The present report describes a case of Staphylococcus (Staph.) aureus pneumonia in turkey poults. Initially, 3-day-old poults with a history of increased mortality were submitted for necropsy. The poults had severe bilateral consolidation of the lungs with miliary caseous nodules. The gross lesions in the lungs were highly suggestive of aspergillosis. The next day, postmortem examinations were performed on 60 dead poults at the farm, and all 60 had similar lung lesions. Histopathologic examination of affected lungs revealed severe subacute multifocal bronchopneumonia with intralesional bacteria. Tissue Gram stain of lung sections demonstrated gram-positive bacterial cocci. Gomori methenamine silver stain of the lungs failed to demonstrate fungal agents. The histologic distribution of the lesions suggested an aerogenous route of infection. Staphylococcus aureus was isolated in pure culture from affected lungs. Hatchery contamination was suspected because of the severity and early onset of the lesions. Bacterial monitoring at the hatchery demonstrated marked Staph. aureus contamination in two setters, a hatcher's air duct, and the poult room. Improved hatchery cleaning and disinfection prevented a reoccurrence of the problem.

Consolidating pneumonia and pneumothorax in a horse

A 3-year-old Thoroughbred mare with signs of acute abdominal pain and chronic pneumonia was found to have pneumothorax. A single application of suction was successful in resolving the pneumothorax. The underlying pneumonia was treated with long-term antibiotic administration selected on the basis of results of bacteriologic culture and antimicrobial susceptibility testing of a transtracheal aspirate. The pneumonia resolved, and the mare returned to competition as a show hunter.