How has childhood shigellosis in Vietnam changed over 14 years?
Over 14 years the dominant cause of childhood dysentery in southern Vietnam switched from S. flexneri to S. sonnei, resistance to key drugs like ceftriaxone rose, and admitted children appeared more severely ill.
Source
A changing picture of shigellosis in southern Vietnam: shifting species dominance, antimicrobial susceptibility and clinical presentation
Study at a glance
- Design
- Cross-sectional — Serial comparison of three independent hospital studies (1995-96, 2000-02, 2006-08) with re-tested stored isolates and pooled clinical records
- N
- N=279 · 279 children with culture-confirmed shigellosis had clinical data (63, 113 and 103 across the three periods); 297 Shigella strains were analysed microbiologically
- Population
- Children under 14 admitted with diarrhoea or dysentery to a tropical-diseases hospital in Ho Chi Minh City and a provincial hospital in southern Vietnam
- Outcome
- Shigella species mix, antimicrobial susceptibility profiles, and clinical features of disease across the three periods
Structured fields used in claim comparison tables when every cited study has a complete layer.
What they did
The researchers combined data from three separate hospital studies of children with diarrhoea or dysentery in southern Vietnam, run in 1995-96, 2000-02 and 2006-08. Stored Shigella isolates were re-identified and re-tested against seven antibiotics using disk diffusion and E-test MICs. Clinical details recorded on standard forms (age, symptoms, blood counts, stool microscopy, length of stay) were compared across the periods and between species.
What they found
S. sonnei rose from 29% of isolates in the first period to 78% in the last, replacing S. flexneri as the dominant species. Resistance to nalidixic acid, ofloxacin and ceftriaxone climbed step by step (by the last period 23% were ceftriaxone-resistant and 68% nalidixic-acid-resistant), while resistance to older drugs like ampicillin and chloramphenicol fell. Children in later periods were older, had more watery diarrhoea, abdominal pain and febrile convulsions, higher white-cell counts and longer hospital stays, suggesting more severe disease, although the two species produced only subtly different clinical pictures.
The limits
What it doesn't show
The three source studies had different aims and entry criteria (the middle one enrolled any diarrhoea rather than dysentery, and its treatment was not controlled), so changes across periods may partly reflect who was enrolled rather than true change in the disease. Only hospitalised children at referral hospitals were included, so the authors say they cannot estimate incidence or the wider community picture. The link between rising severity and the switch to S. sonnei is a temporal association, not a demonstrated cause, and the explanation that antibiotic use drives resistance is the authors' interpretation rather than something measured.
Key terms
- Shigellosis
- Bacterial dysentery caused by Shigella species, spread by the faecal-oral route and causing fever and bloody or mucoid diarrhoea.
- Species shift
- A change over time in which bacterial species causes most infections in a population, here from S. flexneri to S. sonnei.
- Minimum inhibitory concentration (MIC)
- The lowest antibiotic concentration that stops visible bacterial growth; higher values mean the organism is less susceptible.
- Multidrug resistance
- Resistance to several antibiotics at once; here, resistance to three or more of the seven drugs tested.
- Selective pressure
- The way antibiotic use favours the survival and spread of resistant bacteria over susceptible ones.
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Quiz yourself
What was the main species change observed between 1995-96 and 2006-08?
Common questions
Why would resistance to ampicillin and chloramphenicol go down?
The authors suggest these older drugs are now rarely used for gut infections in the community, so there is less selective pressure keeping resistant strains common, while newer drugs in current use (quinolones, ceftriaxone) saw resistance rise.
Does this prove S. sonnei causes worse disease?
No. Severity rose over the same years that S. sonnei took over, but when the species were compared directly the differences were subtle, and the study periods also differed in enrolment criteria.
Why does the species mix matter for vaccines?
Infection gives mostly serotype-specific immunity, so a vaccine designed around the locally dominant species or serotypes may miss others; a shifting mix argues for multivalent vaccines.
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