Molecular Epidemiology of Pneumococcal Carriage among Children with Upper Respiratory Tract Infections in Hanoi, Vietnam

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http://jcm.asm.org/cgi/content/abstract/40/11/3903

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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. Hermans^1*

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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