Streptococcus pneumoniae Causing Invasive Diseases in Children and Adults in Central Thailand, 2012-2016.

Longitudinal data regarding the serotype distribution and antimicrobial susceptibility of S. pneumoniae-causing invasive pneumococcal disease (IPD) in developing countries are limited. Our aim was to monitor the antimicrobial susceptibility, serotype distribution, and serotype coverage rates of the pneumococcal conjugate vaccines (PCVs) and emerging non-vaccine serotypes (NVT) between 2012 and 2016 in central Thailand. Pneumococcal isolates from sterile specimens of patients, collected within a long-standing collaborative hospital network in central Thailand between 2012 and 2016, were studied. The pneumococcal serotypes included in the 15-valent PCV were identified by the quellung reaction, while the non-PCV15 serotypes were identified by multiplex PCR. Antimicrobial susceptibilities were determined by the microbroth dilution or disk diffusion method. Of the 276 pneumococcal isolates, 129 (46.7%) were from children aged ≤5 years. Only 9.0% of patients with available data received the PCV prior to the onset of the IPD. The most common vaccine serotypes were 6B (17.4%), 19A (13.0%), and 14 (11.2%), respectively. Non-PCV15 serotypes were detected in 27.9%; the most common serotypes were 15B/C (5.1%), 15A/F (4.0%), and 23A (3.6%), respectively. The serotype coverage rates of PCV10 in children aged ≤5 years was 55.8%, and 53.3% across all ages. PCV13 provided similar coverage rates to that of PCV15, 71.3% in children aged ≤5 years, and 72.1% across all ages. High susceptibilities to cefotaxime (94.6%), ofloxacin (98.2%), linezolid (99.6%), and vancomycin (100.0%) were observed, while the susceptibility to erythromycin (50.0%), TMP-SMZ (41.3%), and tetracycline (27.2%) were low. The susceptibilities to penicillin, meropenem, and clindamycin were 85.9%, 85.9%, and 84.8%, respectively. Serotype 19A was associated with a lower susceptibility than the non-19A isolates for penicillin (75.0% vs. 87.5%, p = 0.045), meropenem (52.8% vs. 90.8%, p < 0.001), erythromycin (33.3% vs. 53.8%, p = 0.022), and TMP-SMZ (16.7% vs. 45.0%, p = 0.001). Although the majority of the pneumococcal serotypes causing IPD in central Thailand were covered by the currently available PCVs, 25% of IPD were caused by NVT. Several emerging NVT identified were 15B/C, 15A/F, and 23A. The high rates of resistance to penicillin, meropenem, erythromycin, TMP-SMZ, and tetracycline observed is a major concern. Serotype 19A was associated with lower antimicrobial susceptibilities in comparison to the non-19A serotypes.

Spread of genetically similar noroviruses in Bangkok, Thailand, through symptomatic and asymptomatic individuals.

Norovirus infection is a major cause of acute gastroenteritis, although some infected individuals are asymptomatic. GII.4 is the predominant genotype worldwide and, since 2000, has been the most prevalent in patients in Thailand with acute gastroenteritis. We screened stool samples for norovirus in 786 patients with acute gastroenteritis who were admitted to a hospital in Bangkok from 2017 to early 2019 and detected it in 136 specimens (17.3%). Eight and 124 specimens were positive for the GI and GII genogroups, respectively, and the remaining 4 specimens were double-positive. Nine genotypes (GI.3, GI.5, GII.2, GII.3, GII.4, GII.6, GII.8, GII.13, and GII.17) were identified from 140 strains, and 72 strains (51.4%) were GII.4. We had previously conducted a one-year survey of norovirus infection in residents of a community in Bangkok from May 2018 to April 2019 and found that a substantial portion of the residents were infected asymptomatically. The 9 genotypes identified in the patients were also commonly identified in the community residents. To investigate the relationship between noroviruses identified in the acute gastroenteritis patients and those identified in the community residents, phylogenetic tree analysis was conducted. Of the 9 genotypes, 8 showed similarities in both their genomic sequences and their deduced amino acid sequences. In addition, strain replacement of GI.3 was observed in both the patients and the community residents within the overlapping period. These results suggested that norovirus spreads efficiently to the community by simultaneously causing symptomatic and asymptomatic infections.

The dynamics of norovirus genotypes and genetic analysis of a novel recombinant GII.P12-GII.3 among infants and children in Bangkok, Thailand between 2014 and 2016.

Norovirus (NoV) is the leading cause of viral acute gastroenteritis among all age groups in the world. We performed a molecular epidemiological study of the NoVs prevalent in Bangkok between November 2014 and July 2016 to investigate the emergence of new NoV variants in Thailand. A total of 332 stool specimens were collected from hospitalized pediatric patients with acute gastroenteritis in Bangkok, Thailand. NoVs were detected by real-time PCR. The genome of the N-terminal/shell domain was amplified, the nucleotide sequence was determined, and phylogenetic analyses were performed. GII NoV was detected in 58 (17.5%) of the 332 specimens. GII.17, a genotype strain prevalent from 2014 to mid-2015, was hardly detected and replaced by the GII.3 genotype strain. Entire genome sequencing followed by phylogenetic analysis of the GII.3 genotype strains indicated that they are new recombinant viruses, because the genome encoding ORF1 is derived from a GII.12 genotype strain, whereas that encoding ORF2-3 is from a GII.3 genotype strain. The putative recombination breakpoints with the highest statistical significance were located around the border of 3Dpol and ORF2. The change in the prevalent strain of NoV seems to be linked to the emergence of new forms of recombinant viruses. These findings suggested that the swapping of the structural and non-structural proteins of NoV is a common mechanism by which new epidemic variants are generated in nature.

Changing trends in serotype distribution and antimicrobial susceptibility of Streptococcus pneumoniae causing invasive diseases in Central Thailand, 2009-2012.

To describe the trends in serotype distribution and antimicrobial susceptibility of S. pneumoniae causing invasive pneumococcal diseases (IPD) we tested 238 pneumococci isolates from normally sterile sites between 2009 and 2012 and compared these findings with previous data collected within our network. Serotyping was performed for 15 serotypes contained in the 7-,10-, 13-, and experimental 15-valent pneumococcal conjugate vaccines (PCV). The most common serotypes found were 6B (13.9%), 19A (12.6%), 14 (8.0%), 18C (5.9%), and 6A (3.8%); and 39.9% were non-PCV15 serotypes. One of 81 patients with available data had breakthrough infection with vaccine serotype (19F). There was a significant increase of serotype 19A among children ≤5 years (5.6% in 2000-2009 vs 18.3% in 2009-2012, P = 0.003). The all-age serotype coverage was 36.4%, 41.5%, 59.3%, and 59.7% for PCV7, PCV10, PCV13, and PCV 15, respectively. The corresponding coverage in children ≤5 years were 46.4%, 48.8%, 73.2%, and 73.2% respectively. High susceptibilities to penicillin (89.7%), cefotaxime (95.7%), cefditoren (90.2% by Spanish breakpoints), ofloxacin (97.9%), and levofloxacin (100%), but low to cefdinir (50.0%), cefditoren (45.1% by US-FDA breakpoints), macrolides (<50%), clindamycin (67.7%), tetracycline (41.4%), and trimethoprim-sulfamethoxazole (32.4%) were observed. Serotype 19A was less susceptible to penicillin (80.0 vs 91.2%, P = 0.046), cefditoren (66.7 vs 95.5% by Spanish breakpoints, P = 0.004), and tetracycline (9.1 vs 45.5%, P = 0.024) than non-19A isolates. These data emphasize the need for continued surveillance to monitor changes in serotypes as well as antimicrobial susceptibilities in order to guide strategies for prevention and treatment.

Serotype distribution and antibiotic susceptibility of invasive Streptococcus pneumoniae isolates in patients aged 50 years or older in Thailand.

As the 13-valent pneumococcal conjugate vaccine (PCV13) has been approved for use in adults aged 50 y and older, we evaluated vaccine-serotype coverage rate in Thai adult patients with invasive pneumococcal infections before the vaccine was widely used. Of the 157 S. pneumoniae isolates from normal sterile sites during January 2005 to September 2012, 150 (95%) from blood, mean patients' age 69.6 (range 50-89) years, the overall serotype coverage by PCV13 was 58%. The vaccine covered 50%, 56%, 59%, and 68% of the invasive isolates from patients aged 50-59, 60-69, 70-79, and ≥80 y, respectively. The most common vaccine serotypes were 6B (17%), 19A (9%), 18C (5%), and 23F (4%). The susceptibility rates of penicillin and ceftriaxone were 95% and 96% for nonmeningitis criteria; and 46% and 92% for meningitis criteria, respectively. The susceptibilities to other antibiotics were: chloramphenicol 76%, clindamycin 80%, erythromycin 57%, levofloxacin 100%, ofloxacin 94%, tetracycline 39%, trimethoprim/sulfamethoxazole 37%, linezolid 99%, and vancomycin 100%, respectively. These data served as a reference for monitoring of vaccine serotype coverage with future increased vaccine utilization.

Serotype coverage of pneumococcal conjugate vaccine and drug susceptibility of Streptococcus pneumoniae isolated from invasive or non-invasive diseases in central Thailand, 2006-2009.

The serotype of 172 S. pneumoniae isolates obtained from normally sterile sites from January 2006 to February 2009 in Thai patients was evaluated. The most common serotypes were 6B, 23F, 14, 19F, and 19A in patients <5 year-old, and 6B, 19A, 23F, 4, 9V in patients >65-year old. Seven-valent pneumococcal conjugated vaccine (PCV-7) covered 70.3%, 43.6%, and 43.5% of patients <5, 5-64 and > or = 65 years of age, respectively, while PCV-13 covered 81.2%, 59.7%, and 60.9%, respectively. PCV-9, PCV-10, PCV-11 had very similar coverage as PCV-7. The antibiotic susceptibility rates of the isolates from sterile sites were 88.7-95.7% for penicillin, 90.6-98.4% for cefotaxime, 92.2-100% for ofloxacin and 100% for ciprofloxacin. PCV-7 covered 83% and 100%, respectively, of penicillin and cefotaxime non-susceptible isolates in patients <5-year old.

Serotype distribution and antimicrobial susceptibility of S. pneumoniae causing invasive disease in Thai children younger than 5 years old, 2000-2005.

In order to predict the potential benefit of pneumococcal conjugate vaccines (PCV), we evaluated the serotype coverage of the 7-, 9-, 11- and 13-valent PCV over the isolates causing invasive pneumococcal disease (IPD) in Thai children. One hundred and fifteen Streptococcus pneumoniae isolates from sterile sites in children younger than 5 years old between 2000 and 2005 were serotyped. The coverages of 7-, 9-, 11-, and 13-valent PCV were 69%, 73.8%, 73.8% and 85.7% in children younger than 2 years, and 73.9%, 77.4%, 77.4% and 87.8% in children younger than 5 years of age, respectively. 69.6% and 22.6% of the isolates were non-susceptible to penicillin and cefotaxime. 7-valent PCV covered 89% and 100% of penicillin and cefotaxime non-susceptible isolates.