Before any interventions were undertaken, the outbreak strain was isolated from nasopharyngeal specimens from 17 of the 74 residents tested (23 percent), including 3 in whom pneumonia subsequently developed, and 2 of the 69 employees tested (3 percent). All other pneumococcal isolates that were recovered were sensitive to penicillin
In the second nasopharyngeal-culture survey, conducted after the completion of chemoprophylaxis, serotype 23F was recovered from three residents and none of the employees. Five weeks later, two residents were still colonized. All multidrug-resistant isolates from blood, sputum, and nasopharyngeal specimens had identical patterns ofantimicrobial susceptibility ….
In the community, S. pneumoniae was isolated from nasopharyngeal specimens from 62 percent of 97 children tested. Two children, 18 and 20 months old, carried multidrug-resistant serotype 23F that was identical to the outbreak strain according to pulsed-field gel electrophoresis. However, they had no known contact with each other or with the nursing home. No invasive disease developed in any of the children participating in the nasopharyngeal survey.
In this explosive outbreak, a single multidrug-resistant pneumococcal strain was disseminated among nursing home residents and staff members. Our investigation suggests that several factors contributed to the high attack rate of disease, including a susceptible, unvaccinated population and a high prevalence of colonization with a virulent organism.’
Source: N Engl J Med 1998; 338:1861-1868
‘There has been little or no net change in the bacterial carriage prevalence.’
This is what a researcher wrote in a medical journal concerning carriage rates of seven types of pneumonia after the introduction of the original 7-valent vaccine.