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. 2023 Oct 30;17(10):e0011728.
doi: 10.1371/journal.pntd.0011728. eCollection 2023 Oct.

The seroincidence of childhood Shigella sonnei infection in Ho Chi Minh City, Vietnam

Nick K Jones  1 , Trang Nguyen Hoang Thu  2 , Ruklanthi de Alwis  2   3 , Corinne Thompson  2 , Ha Thanh Tuyen  2 , Tran Do Hoang Nhu  2 , Voong Vinh Phat  2 , Pham Duc Trung  2 , Phung Khanh Lam  2 , Bui Thi Thuy Tien  4 , Hoang Thi Diem Tuyet  4 , Lu Lan Vi  5 , Nguyen Van Vinh Chau  5 , Nhi Le Thi Quynh  2 , Stephen Baker  1   2
Affiliations

The seroincidence of childhood Shigella sonnei infection in Ho Chi Minh City, Vietnam

Nick K Jones et al. PLoS Negl Trop Dis. .

Abstract

Background: Shigella sonnei is a pathogen of growing global importance as a cause of diarrhoeal illness in childhood, particularly in transitional low-middle income countries (LMICs). Here, we sought to determine the incidence of childhood exposure to S. sonnei infection in a contemporary transitional LMIC population, where it represents the dominant Shigella species.

Methods: Participants were enrolled between the age of 12-36 months between June and December 2014. Baseline characteristics were obtained through standardized electronic questionnaires, and serum samples were collected at 6-month intervals over two years of follow-up. IgG antibody against S. sonnei O-antigen (anti-O) was measured using an enzyme-linked immunosorbent assay (ELISA). A four-fold increase in ELISA units (EU) with convalescent IgG titre >10.3 EU was taken as evidence of seroconversion between timepoints.

Results: A total of 3,498 serum samples were collected from 748 participants; 3,170 from the 634 participants that completed follow-up. Measures of anti-O IgG varied significantly by calendar month (p = 0.03). Estimated S. sonnei seroincidence was 21,451 infections per 100,000 population per year (95% CI 19,307-23,834), with peak incidence occurring at 12-18 months of age. Three baseline factors were independently associated with the likelihood of seroconversion; ever having breastfed (aOR 2.54, CI 1.22-5.26), history of prior hospital admission (aOR 0.57, CI 0.34-0.95), and use of a toilet spray-wash in the household (aOR 0.42, CI 0.20-0.89).

Conclusions: Incidence of S. sonnei exposure in Ho Chi Minh City is substantial, with significant reduction in the likelihood of exposure as age increases beyond 2 years.

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Conflict of interest statement

The authors have declared that no competing interests exist.

Figures

Fig 1
Fig 1. Counts of serum samples collected.
Bar charts showing the numer of serum samples collected during the study period. A, Total number of serum samples collected at each follow-up visit. B, Total number of serum samples collected from participants at each age, including those taken from participants with incomplete follow-up (n = 748). C, Total number of serum samples collected from participants at each age, restricted to those that completed follow-up (n = 634).
Fig 2
Fig 2. Variation in S. sonnei anti-O IgG titres and frequency of observed seroconversion by calander month of serum sampling.
Distributions of S. sonnei anti-O IgG titres and the freqeuncy of observed seroconversion at each calendar month of sampling. A, All S. sonnei anti-O IgG titres (log10-transformed EU), inclusive of seronegative samples and those from participants with incomplete follow-up. B, S. sonnei anti-O IgG titres (log10-transformed EU) in convalescent samples with evidence of seroconversion only, inclusive of samples taken from participants with incomplete follow-up. C, Frequency of observed seroconversion events in convalescent samples, inclusive of samples taken from participants with incomplete follow-up.
Fig 3
Fig 3. Variation in S. sonnei seroincidence by 6-month age group.
S. sonnei seroincidence in different 6-month age groups, shown as: A, Exposures per 100,000 population, with 95% confidence intervals. B, Seroincidence rate ratios, with the 12–18 month age period as a reference category.
See this image and copyright information in PMC

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