Different Behavior and Response of Staphylococcus Epidermidis and Streptococcus Pneumoniae to a Ventriculoperitoneal Shunt: An in vitro Study

Abstract

Background: Pneumococcal shunt infection is a rare event. There is no consensus on the therapeutic management of this kind of shunt infection according to literature reviews, and it seems to be different from infection with Staphylococcus epidermidis. We studied 2 shunted patients with pneumococcal meningitis, both of whom were treated with only antibiotics. The management of these cases seems to be different from that of shunt catheter infection due to these bacteria. We conducted a laboratory study to show the different behavior of pneumococcus compared to S. epidermidis regarding shunt catheter colonization.

Materials and methods: S. epidermidis and Streptococcus pneumoniae bacteria isolated from the cerebrospinal fluid of meningitis patients were incubated in sterile media. Forty-five segments of shunt catheter from silicone material were placed in 45 separate media of S. epidermidis and pneumococcus. Then each catheter was washed and cultured in blood chocolate agar growth medium in separate petri dishes via the roll plate method. The dishes were extracted from the incubator and the colony count was calculated after 72 h.

Results: The colony count was obviously different between the 2 bacteria groups, with a higher count related to S. epidermidis dishes. The colony count of the pneumococcal petri dishes was 25-35,000 (mean 14,337) and for dishes with S. epidermidis it was 14,000-100,000 (mean 50,125) (p = 0.001).

Conclusion: The adherence of pneumococcus to shunt catheters seems to be much less than that of S. epidermidis, which produced a very low colony count when incubated with the catheter in the medium culture. S. pneumoniae meningitis in shunted patients can be managed successfully with only antibiotics. This approach can prevent problems related to the several additional surgeries required for shunt removal, a new shunt insertion, and the management of high intracranial pressure.

Keywords: Colonization; Infection; Staphylococcus epidermidis; Streptococcus pneumoniae; Treatment; Ventriculoperitoneal shunt.