43rd ICAAC
A meeting of the American Society for Microbiology

September 14-17, 2003, Chicago, IL

 

For more information on any presentation at the 43rd ICAAC contact Jim Sliwa, ASM Office of Communications at jsliwa@asmusa.org

 

NOTE:  ALL NEWS REPORTS ARE EMBARGOED UNTIL DATE AND TIME OF PRESENTATION

EMBARGOED UNTIL:  Wednesday, September 17, 9:00 a.m.

(Session 210, Paper G-2047)

M. Catherine McEllistrem
Univ. of Pittsburgh
Pittsburgh, PA,
Phone: 412-648-6401

mcellistremc@msx.dept-med.pitt.edu


The licensure of the 7-valent pneumococcal conjugate vaccine (PNC7) in 2000 has resulted in a dramatic reduction in invasive disease due to Streptococcus pneumoniae. The PNC7 contains the serogroups most often associated with drug-resistant infections and pediatric invasive infections (serotypes 4, 6B, 9V, 14, 18C, 19F, 23F). The effect of this vaccine on ear infections is not well-known. An increase in the frequency of ear infections due to serogroups of S. pneumoniae not included in the vaccine occurred from 1/1/99-12/31/02. The overall recovery of penicillin nonsusceptible pneumococcal strains causing ear infections did not significantly change over time; however, the proportion of penicillin nonsusceptible isolates derived from serogroups contained in the vaccine did increase.

Abstract: The licensure of the 7-valent pneumococcal conjugate vaccine (PNC7) in 2000 has resulted in a dramatic reduction in invasive disease due to Streptococcus pneumoniae. The frequency of penicillin nonsusceptible strains and PNC7 serogroups of S. pneumoniae causing cases of acute otitis media (AOM) due to S. pneumoniae was determined from 1/1/99-12/31/02 at the Children’s Hospital of Pittsburgh. In addition, a serogroup-specific analysis of the strains was performed.

Overall, the recovery of pneumococcal serogroups contained in PNC7 decreased over time, especially serogroups 6 and 23 (Table). In contrast, the serogroup 19 strains [of which 88% (15/17) were serotype 19F in 2002], increased. Among the serogroup 19 strains, 47% (9/19) of the 2001 strains compared to 6% (1/17) of the 2002 strains were variants of the Spanish 23F International Clone as determined by pulsed-field gel electrophoresis and multi-locus sequence typing (p < 0.01). Among the non-PNC7 serogroups, serotype 3 significantly increased over time. Increases of nonvaccine serogroups 15 and 35 were observed in 2001 but disappeared in 2002.

The overall recovery of penicillin nonsusceptible strains of middle ear isolates of S. pneumoniae did not significantly differ over time; however, the proportion of penicillin nonsusceptible isolates derived from serogroups contained in PNC7 serogroups did increase. Although limited by the small numbers, the data suggest this rise was partially due to an increase in penicillin nonsusceptible serogroup 19 strains. Continuous monitoring of the epidemiology of pneumococcal infections is critical for future vaccine development.

CHANGES IN THE SEROGROUP DISTRIBUTION AMONG CHILDREN WITH AOM (%), 1999-2002

YEAR (number unless otherwise indicated)

1999 (n=88)

2000 (n=76)

2001 (n=63)

2002 (n=44)

PNC7 SEROGROUPS
(p <0.01)

85
 

83
 

63
 

64
 

SEROGROUP 6
(p< 0.01)

23
 

20
 

11
 

7
 

SEROGROUP 19
(p< 0.01) 

15

33
 

30
 

39
 

SEROGROUP 23
(p< 0.01)

20
 

9
 

8
 

2
 

SEROGROUP 3
(p< 0.01)

3
 

1
 

8
 

20
 

SEROGROUP 15
(p=NS)

1

5

8

0

SEROGROUP 35
(p=NS)

3

1

5

0

PENICILLIN NONSUSCEPTIBLEa(p=NS)

44

51

49

58

PENICILLIN NONSUSCEPTIBLE
AMONG PNC7 SEROGROUPSb
(p< 0.01)

47

60

65

85

PENICILLIN NONSUSCEPTIBLE
AMONG SEROGROUP 6c
(p=NS)

40

21

43

67

PENICILLIN NONSUSCEPTIBLE
AMONG SEROGROUP 19d
(p=0.02)

54

79

79

94

PENICILLIN NONSUSCEPTIBLE
AMONG SEROGROUP 23e
(p=NS)

50

57

60

0

a Number of strains per year were: 1999-88; 2000-73; 2001-63; 2002-40

b Number of strains per year were: 1999-75; 2000-60; 2001-40; 2002-27

c Number of strains per year were: 1999-20; 2000-14; 2001-7; 2002-3

d Number of strains per year were: 1999-13; 2000-24; 2001-19; 2002-16

e Number of strains per year were: 1999-18; 2000-7; 2001-5; 2002-1

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