Emergence of antibiotic-resistant non-vaccine serotype pneumococci in nasopharyngeal carriage in children after the use of extended-valency pneumococcal conjugate vaccines in Korea.

This study was performed to assess the serotype distribution and antibiotic nonsusceptibility of pneumococcal carriage isolates from children in Korea following the introduction of extended-valency pneumococcal conjugate vaccines (PCVs). From April to June 2014, nasopharyngeal swabs were collected from children who were attending daycare centers in Korea. The collection was conducted in accordance with the World Health Organization Pneumococcal Carriage Working Group standards. Isolates were identified based on colony morphology, the presence of alpha-hemolysis, and inhibition by optochin test. Serotype was determined by Quellung reaction and sequencing analysis (for serogroup 6). The E-test was performed to determine antibiotic susceptibility. A total of 267 pneumococcal isolates were collected from 734 children. Non-PCV13 serotypes accounted for 88.3% and 23A (12.6%), 15B (10.4%), and 15C (9.5%) were most common. Younger age was associated with higher carriage (65.6% vs. 31.2%, P<0.001), while completion of PCV vaccination was associated with lower carriage caused by PCV13 serotypes (7.4% vs. 20.8%, P=0.007). Overall, nonsusceptibility rates were 86.0% to penicillin and 90.5% to erythromycin, with a multidrug resistance rate of 81.5%. Among penicillin-nonsusceptible isolates, those caused by PCV13 serotypes were 11% and non-PCV13 serotypes were 89%. Frequent non-PCV13 serotypes (23A, 15B, and 15C) were all nonsusceptible to both penicillin and erythromycin except one. High rates of carriage caused by non-PCV13 serotypes such as 23A, 15B, and 15C that show nonsusceptibilities to penicillin and erythromycin were noted following the introduction of extended-valency PCVs in Korea.

Choe YJ ，Lee HJ ，Lee H ，Oh CE ，Cho EY ，Choi JH ，Kang HM ，Yoon IA ，Jung HJ ，Choi EH ... -  《-》

Changes in the Serotype Distribution among Antibiotic Resistant Carriage Streptococcus pneumoniae Isolates in Children after the Introduction of the Extended-Valency Pneumococcal Conjugate Vaccine.

This study investigated the serotype distribution and antimicrobial resistance of 3,820 nasopharyngeal Streptococcus pneumoniae isolates from infants and children who presented with respiratory symptoms at Seoul National University Children's Hospital from July 2010 to June 2015 after the introduction of the extended-valency pneumococcal conjugate vaccines (PCVs). Serotypes and antimicrobial susceptibility were determined using the Quellung reaction and E-test, respectively. S. pneumoniae was isolated from 397 (10.4%) specimens. The most common serotypes were 19A (14.0%), 23A (12.8%), 15B/C (10.7%), 11A (10.1%), 6C (7.8%), and 6A (6.3%) among the typeable pneumococci (n = 335). The PCV serotype proportions significantly decreased (59.1% in 2010/11 to 17.0% in 2014/15, P < 0.001), whereas the non-PCV serotype proportions significantly increased (40.9% in 2010/11 to 83.0% in 2014/15, P < 0.001). The non-susceptibility rates for penicillin (oral), penicillin (parenteral, non-meningitis), cefotaxime, and erythromycin were 97.8%, 22.8%, 27.7%, and 95.5%, respectively. The proportions of PCV serotypes responsible for non-susceptibility to penicillin (parenteral, non-meningitis) and multidrug resistance significantly decreased (80.8% to 21.1%, P < 0.001 and 64.3% to 12.3%, P < 0.001, respectively), whereas the non-PCV serotype proportions significantly increased (19.2% to 78.9%, P < 0.001 and 35.7% to 87.7%, P < 0.001, respectively). Serotypes 23A and 15B/C demonstrated significant proportional increase among the antibiotics resistant strains. Thus, the PCV serotype proportions decreased and the non-PCV serotype proportions increased among nasopharyngeal carriage pneumococci after the introduction of extended-valency PCVs in Korea. Antimicrobial non-susceptibility rates for penicillin and erythromycin remain high despite the decrease in the proportion of PCV serotypes responsible for antimicrobial resistance over time.

Lee JK ，Yun KW ，Choi EH ，Kim SJ ，Lee SY ，Lee HJ ... -  《-》

The impact of a pneumococcal conjugate vaccination program on the nasopharyngeal carriage, serotype distribution and antimicrobial resistance of Streptococcus pneumoniae among healthy children in Turkey.

The 7-valent conjugate pneumococcal vaccine (PCV7) was introduced by the Turkey National Immunization Program in 2008 and replaced by the PCV13 in 2011. We assessed the impact of PCV vaccination on the nasopharyngeal (NP) carriage, serotype distribution and antimicrobial resistance of Streptococcus pneumoniae (SP) among healthy Turkish children. A prospective surveillance study was performed between September 2011 and September 2013 in Istanbul, Turkey. NP swabs, demographic data, and vaccination statuses were obtained from 2165 healthy children aged 0-18years. Pneumococcal carriage was defined by a positive culture; serotyping was performed via multiplex conventional PCR, and the antibiotic susceptibilities of the isolates were determined based on the minimum inhibitory concentration (MIC) values of the Clinical Laboratory Standards Institute (CLSI). The prevalence of pneumococcal carriage was 6.4%. The carriage rates were 8%, 7%, and 5% in the following age groups: 0-24months, 25-60months, and >60months, respectively. The carriage rate was significantly higher in the 0-24month age group than in the >60months age group (p=0.03). Sixty percent of the children were not vaccinated with any PCV; 4%, 2%, and 4% received at least 1, 2 or 3 doses and 30% children received the full schedule (4 doses) of either PCV7 or PCV13. Among the isolated S. pneumoniae strains, 45% were of the non-vaccine type (NVT) and 55% were of the vaccine type (VT). The children who received at least a single PCV dose had significantly lower odds of colonization via VT serotypes than the non-vaccinated children [odds ratio: 0.61 (95% confidence interval=0.41-0.91), p=0.01]. The percentages of the serotypes covered by PCV7 and PCV13 were 51% and 56%, respectively. The most frequently isolated serotypes were 6A/B/C (n=22, 16.5%), 19F (n=18, 13.5%), 23F (n=15, 11.2%), serotype 9V/A (n=10, 7.5%), 12F (n=5, 4.5%), 15A/F (n=7, 4.5%) and 22 A/F (n=6, 4.5%). Using the meningitis criteria and the MIC, 62% of the isolates were resistant to penicillin and 13% were non-sensitive to ceftriaxone. Erythromycin and clindamycin resistance were 43% and 31%, respectively. We shown that following nation-wide PCV vaccination, S. pneumoniae NP carriage was decreased.

Soysal A ，Karabağ-Yılmaz E ，Kepenekli E ，Karaaslan A ，Cagan E ，Atıcı S ，Atınkanat-Gelmez G ，Boran P ，Merdan S ，Hasdemir U ，Söyletir G ，Bakır M ... -  《-》

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

Pneumococcal conjugate vaccine (PCV) has been included in Hong Kong's Childhood Immunization Programme since 2009. This study aimed to assess nasopharyngeal pneumococcal carriage rate, serotypes and antimicrobial resistance pattern in young children after the introduction of 13-valent PCV (PCV13). A community-based, cross-sectional surveillance study was performed on healthy infants attending eleven Maternal and Child Health Centres across different parts of Hong Kong. Nasopharyngeal swabs were obtained from healthy children aged 2, 12 and 18months during their visit to the centers for immunization from June 2013 to June 2014. Pneumococcal isolates were serotyped and tested for antimicrobial resistance. Details of the demographics, family composition, vaccination history and medical history was obtained through interview of the guardians. 1541 children were recruited. The overall carriage rate was 5.5%. Children aged 12 and 18months were more likely to have pneumococcal colonization (12months OR: 2.88; 95% CI: 1.41-5.87 and 18months OR: 2.19, 95% CI: 1.05-4.57). Recent respiratory symptoms and presence of siblings younger than 6years were independently associated with pneumococcal carriage. Eighty-four pneumococcal isolates were serotyped. The most prevalent serogroup/types were 15 (15B/C, 16.7%; 15A/F, 9.5%), 6C (15.5%) and 23A (13.1%). Overall, 2.4% of the isolates were heptavalent PCV serotypes, 10.7% were PCV13 serotypes and 89.3% were non-PCV13 serotypes. The proportions of penicillin, cefotaxime and erythromycin non-susceptible isolates were 7.3%, 13.4% and 79.3% respectively. The rate of pneumococcal carriage was low in young children in Hong Kong and compared to previous local studies there appears to have been an overall reduction in the carriage rate after the introduction of PCV. Likely serotype replacement was noted with a predominance of non-vaccine serotypes in pneumococcal carriage with the emergence of serogroup/type 15 and 6C.

Chan KC ，Subramanian R ，Chong P ，Nelson EA ，Lam HS ，Li AM ，Ip M ... -  《-》

Nasopharyngeal Pneumococcal Carriage among Healthy Children in Cyprus Post Widespread Simultaneous Implementation of PCV10 and PCV13 Vaccines.

Hadjipanayis A ，Efstathiou E ，Alexandrou M ，Panayiotou L ，Zachariadou C ，Petrou P ，Papaevangelou V ... -  《PLoS One》