Origin of Organisms Infecting Ventricular Shunts

Results of preoperative skin cultures obtained prior to 413/505 operations for CSF diverting ventricular shunt placement or revision in a pediatric population during the time period from April 1980 to May 1983 are analyzed and compared to results of cultures from 20 subsequent shunt infections. Antibiotic sensitivities to 11 different antibiotics were determined for each isolate cultured. The total operative infection rate was 20/505 (4%) (Table). Gram negative bacilli alone accounted for 3/20 (15%) shunt infections. One gram negative bacillus/S. aureus infection occurred. Factors predisposing for gram negative bacillus shunt infection were found in all 4 cases. The majority of shunt infections were caused by typical resident skin organisms, Staphylococcus epi. alone 9/20 (45%), S. aureus alone 4/20 (20%), Corynebacte-rious sp. 1/20 (5%), alpha Streptococcus with 5. epidermidis 1/20 (5%), and Micrococcus with S. epidermidis 1/20 (5%). Only 4/20 (20%) of the shunt infections were infected with organisms identical to those originally grown from the skin. Another 4/20 (20%) appeared to be infected with a different strain of organism than initially recovered from the skin. The remaining 8/20 skin organism shunt infections may or may not have come from the patients skin. The data suggests that not all skin organism shunt infections arise from contamination by resident skin bacteria at the incision sites at the time of surgery. Alternate sources include the patients nasopharynx, medical personnel, contaminated instruments and environmental contamination. Combined resistance among S. epi. isolates to Oxacillin and Gentamicin was 16% for the whole study with 33% combined resistance for neonates and 55% resistance for patients hospitalized longer than 20 days.