An experimental in-vivo canine model for adult shunt infection

Hydrocephalus was induced in seven dogs (Canis familiaris) by fourth ventricle obstruction. Four weeks later they were shunted using a Hakim Precision valve. Four of the dogs received shunts whose ventricular catheter had been inoculated with Staphylococcus epidermidis, and three were uninoculated controls. Four weeks after shunting the dogs were sacrificed and necropsy was performed. Removed shunts and tissue samples were examined microbiologically and isolates were subjected to detailed identification and genomic comparison.All the dogs remained well after shunting. Examination of removed shunt components revealed S. epidermidis in the brain and throughout the shunt system in the four inoculated animals, but in two of these Staphylococcus intermedius was also found. S. intermedius was also isolated from all three "negative" controls. There were slight differences between S. intermedius strains suggesting endogenous infection rather than cross- infection from a point source.Shunt infection was established in the canine model, and had the experiment been extended beyond four weeks the typical microbiological, pathological and clinical features might have appeared. The occurrence of unplanned shunt infections in control animals due to canine normal skin flora reflects human clinical experience and underlines the usual source of bacteria causing shunt infection.The introduction of cerebrospinal fluid (CSF) shunts revolutionized the treatment of hydrocephalus and greatly decreased mortality rate. However, over subsequent decades, difficulties in shunt maintenance and problems resulting from infection or occlusion have persisted [1]. Today, shunt failure rates range from 25% to 40% in the first few months after surgery [2,3]. After this critical period, the risk remains at 4% – 5%. As a result, some patients may have numerous shunt revisions during their lifetime, representing a major medical risk. Infections have been a leading cause of shunt failure with infection rat