Graeme Clark Collection
Permanent URI for this collection
Search Results
1 - 3 of 3
-
ItemPneumococcal meningitis post-cochlear implantation: preventative measures.(Wiley, 2010-11)OBJECTIVE: Both clinical data and laboratory studies demonstrated the risk of pneumococcal meningitis post-cochlear implantation. This review examines strategies to prevent post-implant meningitis. DATA SOURCES: Medline/PubMed database; English articles after 1980. Search terms: cochlear implants, pneumococcus meningitis, streptococcus pneumonia, immunization, prevention. REVIEW METHODS: Narrative review. All articles relating to post-implant meningitis without any restriction in study designs were assessed and information extracted. RESULTS: The presence of inner ear trauma as a result of surgical technique or cochlear implant electrode array design was associated with a higher risk of post-implant meningitis. Laboratory data demonstrated the effectiveness of pneumococcal vaccination in preventing meningitis induced via the hematogenous route of infection. Fibrous sealing around the electrode array at the cochleostomy site, and the use of antibiotic-coated electrode array reduced the risk of meningitis induced via an otogenic route. CONCLUSION: The recent scientific data support the U.S. Food and Drug Administration recommendation of pneumococcal vaccination for the prevention of meningitis in implant recipients. Nontraumatic cochlear implant design, surgical technique, and an adequate fibrous seal around the cochleostomy site further reduce the risk of meningitis.
-
ItemPneumococcal meningitis post-cochlear implantation: potential routes of infection and pathophysiology.(Wiley, 2010-11)OBJECTIVE: This review describes the current concept of pneumococcal meningitis in cochlear implant recipients based on recent laboratory studies. It examines possible routes of Streptococcus pneumoniae infection to the meninges in cochlear implant recipients. It also provides insights into fundamental questions concerning the pathophysiology of pneumococcal meningitis in implant recipients. DATA SOURCES: Medline/PubMed database; English articles after 1960. Search terms: cochlear implants, meningitis, pneumococcus, streptococcus pneumonia. REVIEW METHODS: Narrative review. All articles relating to post-implant meningitis without any restriction in study designs were assessed and information extracted. RESULTS: The incidence of pneumococcal meningitis in cochlear implant recipients is greater than that of an age-matched cohort in the general population. Based on the current clinical literature, it is difficult to determine whether cochlear implantation per se increases the risk of meningitis in subjects with no existing risk factors for acquiring the disease. As this question cannot be answered in humans, the study of implant-related infection must involve the use of laboratory animals in order for the research findings to be applicable to a clinical situation. The laboratory research demonstrated the routes of infection and the effects of the cochlear implant in lowering the threshold for pneumococcal meningitis. CONCLUSION: The laboratory data complement the existing clinical data on the risk of pneumococcal meningitis post-cochlear implantation.
-
ItemPneumococcal meningitis: development of a new animal model( 2006)Hypothesis: The rat is a suitable animal to establish a model for the study of pneumococcal meningitis postcochlear implantation. Background: There has been an increase in the number of cases of cochlear implant-related meningitis. The most common organism identified was Streptococcus pneumoniae. Whether cochlear implantation increases the risk of pneumococcal meningitis in healthy subjects without other risk factors remains to be determined. Previous animal studies do not focus on the pathogenesis and risk of pneumococcal meningitis postimplantation and are based on relatively small animal numbers, making it difficult to assess the cause-and-effect relationship. There is, therefore, a need to develop a new animal model allowing direct examination of the pathogenesis of meningitis in the presence of a cochlear implant. Methods: Eighteen nonimplanted rats were infected with 1 x 10[to the power of 6] and 1 x 10[to the power of 8] colony-forming units (CFU) of a clinical isolate of S. pneumoniae via three different inoculation routes (middle ear, inner ear, and i.p.) to examine for evidence of meningitis during 24 hours. Six implanted rats were infected with the highest amount of bacteria possible for each route of inoculation (4 x 10[to the power of 10] CFU i.p., 3 x 10[to the power of 8] CFU middle ear, and I x 106 CFU inner ear) to examine for evidence of meningitis with the presence of an implant. The histological pattern of cochlear infections for each of the three different inoculating routes were examined. Results: Pneumococcal meningitis was evident in all 6 implanted animals for each of the three different routes of inoculation. Once in the inner ear, bacteria were found to enter the central nervous system via either the cochlear aqueduct or canaliculi perforantes of the osseous spiral lamina, reaching the perineural and perivascular space then the internal acoustic meatus. The rate, extent, and pattern of infection within the cochleae depended on the route of inoculation. Finally, there was no evidence of pneumococcal meningitis observed in 18 nonimplanted rats inoculated at a lower concentration of S. pneumoniae when observed for 24 hours postinoculation. Conclusion: Meningitis in implanted rats after inoculation with a clinical isolate of S. pneumoniae is possible via all three potential routes of infection via the upper respiratory tract. The lack of meningitis observed in the 18 nonimplanted rats suggests that longer postinoculation monitoring periods are required to ensure whether or not meningitis will develop. Based on this work, we have developed a new animal model that will allow quantitative risk assessment of meningitis postcochlear implantation, and the assessment of the efficacy of potential interventional strategies in future studies.