Search

Epidemic meningococcal infection is generally caused by single clones; whether nonepidemic increases in infection are clonal is unknown. We studied the molecular epidemiology of meningococcal infection during a period that the incidence increased in two age groups. Serogroup C and Y meningococcal isolates were analyzed by pulsed-field gel electrophoresis and multilocus sequence typing. From 1992 to 1999, 96.4% (27/28) of serogroup C isolates from persons 15-24 years of age were in clonal group 1, compared with 65.6% (21/32) of isolates from persons < or =14 years, and 64.3% (9/14) of isolates from adults > or =25 years (p < or = 0.01). The proportion of clonal group 2 serogroup Y strains increased from 7.7% (1/13) in 1992 to 1993 to 52.0% (13/25) in 1998 to 1999 (p < 0.01). The nonepidemic age-specific increases in serogroup C meningococcal infection in Maryland were clonal in nature and the changes in serogroup Y incidence were associated with a shift in the genotypes of strains causing invasive disease.

The proportion of relapses and reinfections that are potentially preventable by vaccine in human immunodeficiency virus (HIV)-infected persons with recurrent pneumococcal disease is unknown. Isolates from HIV-infected individuals from Baltimore with recurrent pneumococcal invasive disease were collected from 1 January 1995 through 31 December 2000. Serotyping and pulsed-field gel electrophoresis were performed. From 1 January 1995 through 31 December 1998, 14.9% (404/2717) of those who had a pneumococcal infection were HIV infected. The recurrence rate among HIV-infected individuals was 6.4-fold higher than that among individuals without HIV infection (P<.01). Among recurrent infections in 41 individuals, there were 42 reinfections and 6 relapses. All relapses and 91% (70/77) of reinfections were due to serotypes covered by the 23-valent pneumococcal polysaccharide vaccine. Reinfection was more common than relapse among HIV-infected individuals with recurrent pneumococcal disease. Although a substantial proportion of recurrent pneumococcal infections was potentially preventable by vaccine, creating an effective vaccine may be challenging for this population.