Nasopharyngeal Carriage Rate and Serotypes ofStreptococcus pneumoniaeand Antimicrobial Susceptibility in Healthy Korean Children Younger than 5 Years Old: Focus on Influence of Pneumococcal Conjugate Vaccination

Abstract

BackgroundEven after pneumococcal vaccination introduction, Streptococcus pneumoniae (pneumoccocus) is still an important cause of respiratory and invasive severe infection. Pneumococcus is resided in nasal mucosa and local or systemic infection begins with the nasal mucosa damage. We studied the indirect effect of pneumococcal conjugate vaccine (PCV) on pneumococcal nasopharyngeal carriage rates, serotypes and antimicrobial susceptibility between vaccinate and non-vaccinated children.Materials and MethodsFrom January 2010 to October 2010, 379 healthy children under 5 years old from three university hospitals were recruited. Fully vaccinated children over 3 time doses of PCV and children with no vaccination history of PCV were enrolled, and nasopharyngeal aspirations were obtained from these children. Serotypes using multibead serotyping assay with multiplex PCR and antimicrobial susceptibility was analyzed. Antimicrobial susceptibilities were determined by the CLIS guideline.ResultsTwo hundred seventy six children were received pneumococcal vaccination while 103 were not. 137 pneumococci were isolated from nasopharyngeal aspiration specimens. Nasal carriage rate was significantly low in vaccinated group (P-value; 0.001). Nasopharyngeal carriage rate was 28.6% (79/276) in vaccinate group and 56.3% (58/103) in non-vaccinated group. Among those vaccinated group, 13.0% (36/276) of the serotypes were vaccine or vaccine related type with the most common type 19F. In contrast, 31.1% (32/103) of the serotypes in non vaccinated group were vaccine or vaccine related type with the most common type 6A. The resistant rate of penicillin was 90.5%. For antimicrobial susceptibility, amoxicillin and amoxicillin/clavulanate showed high susceptibility (73.0%), but 19F and 19A serotypes were all resistant against amoxicillin.ConclusionsHigh nasopharyngeal carriage rate in non vaccinated group corresponded to the result of past study. However, 19F and 19A still came up as problematic serotypes with a high carriage rate and antimicrobial resistance in both vaccinated and non vaccinated groups. Also, this study showed that the resistance rate of primary oral antimicrobial agents was increased in compared to past. For solving these problems, the selective antimicrobial use with establishment of high dose amoxicillin/clavulanate regimen and active PCV immunization should be needed. Furthermore, pneumococcal carriage and serotype study concerning with antimicrobial susceptibility should be conducted in the future in 10 or 13-valent PCV received children.

Pneumococcal carriage in young children after introduction of PCV13 in Hong Kong

“…The significant reduction in vaccine serotypes in nasopharyngeal colonization was consistent with findings from other post-PCV surveillance studies and reflects the effectiveness of immunization [12,13,[14][15][16][17]24,25]. Our surveillance was conducted in 2013-2014 which was around 18 months after introduction of PCV13 into the CIP.…”

“…Serotype replacement in pneumococcal carriage in these children was evident with the emergence of serogroup 15 and serotype 6C. Local prevalence of pneumococcal carriage as shown by our study was low when compared with data from other countries which show carriage rates of 28.8-35% in children under 2 years old [12,14,15,[23][24][25]. Previous local surveillance studies have also shown lower pneumococcal carriage rates than Caucasian and other Asian populations [12,14-17,23-26], which may explain the lower IPD burden in Hong Kong than other countries [27].…”

“…All subjects in our cohort were vaccinated appropriately for age with PCV13 while in some other cohorts, the reported PCV uptake rates were lower (13.7-39.9%) [12,23]. While some studies found a reduction in overall nasopharyngeal pneumococcal colonization after introduction of PCV [17,24,28], others did not report similar findings [14,25]. When compared with PCV7, reduced acquisition of antibiotic non-susceptible pneumococcus with the use of PCV13 was recently reported [29].…”

The Changing Epidemiology of Childhood Pneumococcal Disease in Korea

“…In one hospital, among 842 hospitalized children with lower respiratory infections tested between 2009 and 2010, the pneumococci serotypes were determined using multiplex polymerase chain reaction tests, which reported among 167 specimens from which pneumococcal DNA was detected a predominance of serotypes 19A (23.4%), 6A/B (16.2%), 19F (11.4%), and 15A (5.4%) [63]. A hospital-based study reported that among pneumococci isolated from the nasopharynx of healthy children, 19F (13.9%) and 34 (11.4%) were the major serotypes among children with vaccination records, while 6A (15.5%) and 6D (12.1%) were the main serotypes identified among children with no vaccination records [64]. …”

“…PCV7, serotypes included in 7-valent pneumococcal conjugate vaccine (4, 6B, 9V, 14, 18C, 19F, 23F); PCV10, serotypes included in 10-valent pneumococcal conjugate vaccine (4, 6B, 9V, 14, 18C, 19F, 23F, 1, 5, 7F); PCV13, serotypes included in 13-valent pneumococcal conjugate vaccine (4, 6B, 9V, 14, 18C, 19F, 23F, 1, 5, 7F, 3, 6A, 19A); NT, nontypable pneumococci. a Nontypable pneumococci were excluded from analysis in Cho et al [42], while Kim et al [62], Ahn et al[63], and Lee et al [64] included the nontypable pneumococci. b In the Cho et al1997-1998 and 2001-2002 study periods [42], differentiation of serotypes 6C/6D from 6A/6B was not carried out; in Ahn et al [63], differentiation between serotypes 6A and 6B was not carried out; in Lee et al [64], differentiation between serotypes 9A and 9V was not carried out; therefore only the estimated vaccine types are described.…”