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

Abstract

To investigate the molecular epidemiology of pneumococcal nasopharyngeal carriage in Hanoi, Vietnam, we studied 84 pneumococcal strains retrieved from children with upper respiratory tract infections. Serotypes 23F (32%), 19F (21%), 6B (13%), and 14 (10%) were found most often. A significant number of strains were antibiotic resistant. Fifty-two percent of the strains were (intermediate) resistant to penicillin, 87% were (intermediate) resistant to co-trimoxazole, 76% were resistant to tetracycline, 73% were resistant to erythromycin, and 39% were (intermediate) resistant to cefotaxime. Seventy-five percent were resistant to three or 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 genetic clusters with 61 isolates (73%). The two largest clusters contained 24 and 12 isolates, and the isolates in those clusters were identical to the two internationally spreading multidrug-resistant clones Spain 23F-1 and Taiwan 19F-14, respectively. The remaining RFEL types were Vietnam specific, as they did not match the types in our reference collection of 193 distinct RFEL types from 16 countries. Furthermore, 57 of the 61 horizontally spreading isolates (93%) in the eight genetic clusters were covered by the seven-valent conjugate vaccine, whereas this vaccine covered only 43% of the isolates with unique genotypes. According to the serotype distribution of the nasopharyngeal pneumococcal isolates, this study suggests a high potential benefit of the seven-valent pneumococcal conjugate vaccine for children in Hanoi.

Molecular Epidemiology of Penicillin-Susceptible Non-β-Lactam-Resistant Streptococcus pneumoniae Isolates from Greek Children

“…So far, no other tetracycline resistance determinants have been on May 11, 2018 by guest http://jcm.asm.org/ described; therefore, the underlying mechanism remains unclear. Also in line with the Vietnamese study is the isolation of tet(M)-containing but tetracycline-susceptible strains in Greece, suggesting the presence of a nonfunctional or unexpressed tetracycline resistance gene (2,9). A similar phenomenon was seen for the PBP genes.…”

“…These data differ from previous findings made by Reinert and coworkers, who observed an almost equal distribution of erm(B) (43%) and mef(E) (56%) genes among erythromycin-resistant isolates in Germany (23). However, our data are in line with a recent study performed in Italy and Vietnam where the majority of the strains also displayed the erm(B) gene (2,19). In the four low-level erythromycin-resistant isolates displaying an identical RFEL genotype and serotype 11A, the erm(A) gene was previously identified (32).…”

“…This is in line with the Vietnamese study where the tet(M) gene was also exclusively observed (2). In contrast to other studies, the remaining tetracycline-resistant isolates did not harbor the tet(O) gene (16).…”

“…In order to discriminate between tet(M) and tet(O), a PCR-RFLP analysis was performed as described previously (2). In summary, a PCR mix was made of 25-l reaction buffer containing 0.5 U of thermostable DNA polymerase, diluted in the buffer supplied by the manufacturer (Integro, Leuvenheim, The Netherlands), 0.2 mM (each) deoxynucleoside triphosphate, 1.5 mM MgCl 2, 10 pmol of each primer, and 10 to 50 ng of pneumococcal DNA.…”

Immunization with a Combination of Three Pneumococcal Proteins Confers Additive and Broad Protection against Streptococcus pneumoniae Infections in Mice

“…As far as we know, 91 capsular polysaccharide serotypes have been identified in S. pneumoniae (33); among these, serotypes 23F, 19F, 14, and 6B are the four most epidemic strains worldwide (2,5,15,17,25,26,29). Moreover, and of recent concern, the widespread use of antibiotics, leading to the development of antibiotic resistance or multidrug resistance against S. pneumoniae, is increasing (9,12,26).…”