Molecular Epidemiology of Pneumococcal Carriage among Children with Upper
Respiratory Tract Infections in Hanoi, Vietnam
D. Bogaert,1 N. T. Ha,2 M. Sluijter,1
N. Lemmens,3 R. de Groot,1 and P. W. M. Hermans1*
Department of Pediatrics, Sophia Children's Hospital,1 Department
of Medical Microbiology and Infectious Diseases, Dijkzigt Hospital, Erasmus
Medical Center Rotterdam, Rotterdam, The Netherlands,3 Department of
Bacteriology and Immunology, National Institute of Hygiene and Epidemiology,
Hanoi, Vietnam2
Received 15 March 2002/ Returned for modification 6 May 2002/ Accepted 4
August 2002
To investigate the molecular epidemiology of pneumococcal
nasopharyngealcarriage in Hanoi, Vietnam, we studied 84 pneumococcal
strainsretrieved from children with upper respiratory tract
infections.Serotypes 23F (32%), 19F (21%), 6B (13%), and 14 (10%)
werefound most often. A significant number of strains were
antibioticresistant. Fifty-two percent of the strains were
(intermediate)resistant to penicillin, 87% were (intermediate)
resistant toco-trimoxazole, 76% were resistant to tetracycline, 73%
wereresistant to erythromycin, and 39% were (intermediate) resistantto cefotaxime. Seventy-five percent were resistant to threeor
more classes of antibiotics. A high degree of genetic heterogeneity
among the penicillin resistance genes was observed. In addition,the
tetracycline resistance gene tet(M) and the erythromycin
resistance gene erm(B) were predominantly observed among the
isolates. Molecular analysis of the 84 isolates by restriction
fragment end labeling (RFEL) revealed 35 distinct genotypes.Twelve
of these genotypes represented a total of eight geneticclusters with
61 isolates (73%). The two largest clusters contained24 and 12
isolates, and the isolates in those clusters wereidentical to the
two internationally spreading multidrug-resistantclones Spain 23F-1
and Taiwan 19F-14, respectively. The remainingRFEL types were
Vietnam specific, as they did not match thetypes in our reference
collection of 193 distinct RFEL typesfrom 16 countries. Furthermore,
57 of the 61 horizontally spreadingisolates (93%) in the eight
genetic clusters were covered bythe seven-valent conjugate vaccine,
whereas this vaccine coveredonly 43% of the isolates with unique
genotypes. According tothe serotype distribution of the
nasopharyngeal pneumococcalisolates, this study suggests a high
potential benefit of theseven-valent pneumococcal conjugate vaccine
for children inHanoi.
* Corresponding author. Mailing address: Laboratory of
Pediatrics, Room Ee1500, Erasmus Medical Center Rotterdam, P.O. Box 1738, 3000
DR Rotterdam, The Netherlands. Phone: 31-10-4088224. Fax: 31-10-4089486. E-mail:
hermans@kgk.fgg.eur.nl.
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