Effect of childhood vaccination and antibiotic use on pneumococcal populations and genome-wide associations with disease among children in Nepal: an observational study.

BACKGROUND: Pneumococcal disease is a leading cause of bacterial pneumonia and invasive bacterial disease among children globally. The reason some strains of pneumococci are more likely to cause disease, and how interventions such as vaccines and antibiotics affect pneumococcal strains is poorly understood. We aimed to identify genetic regions under selective pressure and those associated with disease through the analysis of pneumococcal whole-genome sequences. METHODS: Whole-genome sequencing was performed on pneumococcal isolates collected between January, 2005, and May, 2018, in Kathmandu, Nepal, which included programmatic ten-valent pneumococcal conjugate vaccine (PCV10) introduction in 2015. Isolates were from three distinct cohorts: nasopharyngeal swabs of healthy community-based children, nasopharyngeal swabs of children admitted to hospital with pneumonia, and sterile-site cultures from children admitted to hospital. Across these cohorts we examined serotype distribution, antibiotic resistance, strain distribution, and regions of recombination to determine genes that were undergoing diversifying selection. Genome-wide association studies comparing pneumonia and sterile-site isolates with healthy carriage were used to determine novel variants associated with disease. FINDINGS: After programmatic introduction of PCV10, there was a decline in vaccine covered serotypes; however, strains that had expressed these serotypes continued to exist in the post-PCV population. We identified GPSC9 to be a strain of concern due to its high prevalence in disease, multidrug resistance, and ability to switch to an unencapsulated phenotype via insertion of virulence factor pspC into the cps locus. Antibiotic resistance loci to co-trimoxazole were found to be prevalent (pre-PCV10 78% vs post-PCV10 81%; p=0·27) and increasingly prevalent to penicillin (pre-PCV10 15% vs post-PCV10 32%; p<0·0001). Regions with multiple recombinations were identified spanning the surface protein virulence factors pspA and pspC and antibiotic targets pbpX, folA, folC, folE, and folP. Furthermore, we identified variants in lacE2 to be strongly associated with isolates from children with pneumonia and PRIP to be strongly associated with isolates from sterile sites. INTERPRETATION: Our work highlights the effect of pneumococcal conjugate vaccines, antibiotics, and host-pathogen interaction in pneumococcal variation, and the pathogen's capability of adapting to these factors at both population-wide and strain-specific levels. Ongoing surveillance of disease-associated strains and further investigation of lacE2 and PRIP as serotype-independent targets for therapeutic interventions is required. FUNDING: Gavi, The Vaccine Alliance; WHO; Bill & Melinda Gates Foundation; Wellcome Sanger Institute; and US Centers for Disease Control and Prevention.

Childhood Invasive Bacterial Disease in Kathmandu, Nepal (2005-2013).

BACKGROUND: Invasive bacterial disease (IBD; including pneumonia, meningitis, sepsis) is a major cause of morbidity and mortality in children in low-income countries. METHODS: We analyzed data from a surveillance study of suspected community-acquired IBD in children <15 years of age in Kathmandu, Nepal, from 2005 to 2013 before introduction of pneumococcal conjugate vaccines (PCV). We detailed the serotype-specific distribution of invasive pneumococcal disease (IPD) and incorporated antigen and PCR testing of cerebrospinal fluid (CSF) from children with meningitis. RESULTS: Enhanced surveillance of IBD was undertaken during 2005-2006 and 2010-2013. During enhanced surveillance, a total of 7956 children were recruited of whom 7754 had blood or CSF culture results available for analysis, and 342 (4%) had a pathogen isolated. From 2007 to 2009, all 376 positive culture results were available, with 259 pathogens isolated (and 117 contaminants). Salmonella enterica serovar Typhi was the most prevalent pathogen isolated (167 cases, 28% of pathogens), followed by Streptococcus pneumoniae (98 cases, 16% pathogens). Approximately, 73% and 78% of pneumococcal serotypes were contained in 10-valent and 13-valent PCV, respectively. Most cases of invasive pneumococcal disease (IPD) were among children ≥5 years of age from 2008 onward. Antigen and PCR testing of CSF for pneumococci, Haemophilus influenzae type b and meningococci increased the number of these pathogens identified from 33 (culture) to 68 (culture/antigen/PCR testing). CONCLUSIONS: S. enterica serovar Typhi and S. pneumoniae accounted for 44% of pathogens isolated. Most pneumococcal isolates were of serotypes contained in PCVs. Antigen and PCR testing of CSF improves sensitivity for IBD pathogens.

Effect of the of 10-valent pneumococcal conjugate vaccine in Nepal 4 years after introduction: an observational cohort study.

BACKGROUND: In Nepal, Streptococcus pneumoniae (pneumococcus) is a common cause of bacterial pneumonia in children, and is a major health concern. There are few data on the effect of vaccination on the disease or colonisation with pneumococci in the nasopharynx of children in this setting. The 10-valent pneumococcal conjugate vaccine (PCV10) was introduced into the routine infant immunisation schedule in Nepal in 2015. We aimed to investigate the effect of the introduction of PCV10 on pneumococcal carriage and disease in children in Nepal. METHODS: We did an observational cohort study in children in Nepal. The hospital surveillance study took place in Patan Hospital, Kathmandu, and community studies in healthy children took place in Kathmandu and Okhaldhunga district. For the surveillance study, all children admitted to Patan Hospital between March 20, 2014, and Dec 31, 2019, aged between 2 months and 14 years with clinician-suspected pneumonia, were eligible for enrolment. For the community study, healthy children aged 0-8 weeks, 6-23 months, and 24-59 months were recruited from Kathmandu, and healthy children aged 6-23 months were recruited from Okhaldhunga. We assessed the programmatic effect of PCV10 introduction using surveillance for nasopharyngeal colonisation, pneumonia, and invasive bacterial disease from 1·5 years before vaccine introduction and 4·5 years after vaccine introduction. For the surveillance study, nasopharyngeal swabs, blood cultures, and chest radiographs were obtained from children admitted to Patan Hospital with suspected pneumonia or invasive bacterial disease. For the community study, nasopharyngeal swabs were obtained from healthy children in the urban and rural settings. Pneumonia outcomes were analysed using log-binomial models and adjusted prevalence ratios (aPR) comparing each calendar year after the introduction of the vaccine into the national programme with the pre-vaccine period (2014-15), adjusted for calendar month, age, and sex. FINDINGS: Between March 20, 2014, and Dec 31, 2019, we enrolled 2051 children with suspected pneumonia, and 11 354 healthy children (8483 children aged 6-23 months, 761 aged 24-59 months, and 2110 aged 0-8 weeks) to assess nasopharyngeal colonisation. Among clinical pneumonia cases younger than 2 years, vaccine serotype carriage declined 82% (aPR 0·18 [95% CI 0·07-0·50]) by 2019. There was no decrease in vaccine serotype carriage in cases among older unvaccinated age groups. Carriage of the additional serotypes in PCV13 was 2·2 times higher by 2019 (aPR 2·17 [95% CI 1·16-4·05]), due to increases in serotypes 19A and 3. Vaccine serotype carriage in healthy children declined by 75% in those aged 6-23 months (aPR 0·25 [95% CI 0·19-0·33]) but not in those aged 24-59 months (aPR 0·59 [0·29-1·19]). A decrease in overall vaccine serotype carriage of 61% by 2019 (aPR 0·39 [95% CI 0·18-0·85]) was also observed in children younger than 8 weeks who were not yet immunised. Carriage of the additional PCV13 serotypes in children aged 6-23 months increased after PCV10 introduction for serotype 3 and 19A, but not for serotype 6A. The proportion of clinical pneumonia cases with endpoint consolidation on chest radiographs declined from 41% in the pre-vaccine period to 25% by 2018, but rose again in 2019 to 36%. INTERPRETATION: The introduction of the PCV10 vaccine into the routine immunisation programme in Nepal has reduced vaccine serotype carriage in both healthy children and children younger than 2 years with pneumonia. Increases in serotypes 19A and 3 highlight the importance of continued surveillance to monitor the effect of vaccine programmes. This analysis demonstrates a robust approach to assessing vaccine effect in situations in which pneumococcal disease endpoint effectiveness studies are not possible. FUNDING: Gavi, the Vaccine Alliance and the World Health Organization.

Antibiotic Use and Treatment Outcomes among Children with Community-Acquired Pneumonia Admitted to a Tertiary Care Public Hospital in Nepal.

In the era of growing antimicrobial resistance, there is a concern about the effectiveness of first-line antibiotics such as ampicillin in children hospitalized with community-acquired pneumonia. In this study, we describe antibiotic use and treatment outcomes among under-five children with community-acquired pneumonia admitted to a tertiary care public hospital in Nepal from 2017 to 2019. In this cross-sectional study involving secondary analysis of hospital data, there were 659 patients and 30% of them had a history of prehospital antibiotic use. Irrespective of prehospital antibiotic use, ampicillin monotherapy (70%) was the most common first-line treatment provided during hospitalization followed by ceftriaxone monotherapy (12%). The remaining children (18%) were treated with various other antibiotics alone or in combination as first-line treatment. Broad-spectrum antibiotics such as linezolid, vancomycin, and meropenem were used in less than 1% of patients. Overall, 66 (10%) children were required to switch to second-line treatment and only 7 (1%) children were required to switch to third-line treatment. Almost all (99%) children recovered without any sequelae. This study highlights the effectiveness of ampicillin monotherapy in the treatment of community-acquired pneumonia in hospitalized children in a non-intensive care unit setting.