Outbreak of Pseudomonas aeruginosa in Neurosurgical Patients Associated with a Contaminated Methylene Blue Solution

METHOD: A case was defined as patients with clinical symptomatology of infection and cultures yielding Pseudomonas aeruginosa, between December 1997 and August 1998. Outbreak investigation was done with the classical methodology and case-control studies were conducted, with three controls hospitalized in that period. Cultures were obtained from patients, surfaces, and solutions. Isolates were confirmed by polymerase chain reaction (PCR). RESULTS: A total of 21 cases were identified in the period. (7 meningitis, 5 ventriculitis, 3 osteomyelitis, and 6 wound infections). Attack rate was 5.9% and mortality 9.5%. This outbreak appeared in two phases, with a first cluster in summer and the second in winter. All cases were associated with neurosurgical procedures (p=0.00057). Besides patients, Pseudomonas aeruginosa was isolated from methylene blue solution used for painting the skin surrounding the surgical area. All strains isolated had identical PCR banding patterns. Following replacement of methylene blue solution by a disposable pencil marker, the outbreak ceased. CONCLUSION: This outbreak was related to methylene blue solution contaminated with Pseudomonas aeruginosa. This outbreak reminds us that solutions can be contaminated by negative-gram bacilli like Pseudomonas. The detection and modification of wrong practices are essentials for controlling and preventing the appearance of similar situations.