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Author Spotlight: Advancements in Understanding and Combatting Shigella Infections
Published on: February 9, 2024
Shigella PCR-positive Gastroenteritis in Children: Insights From a Comparison Between Culture-positive and
Yehonatan Beeri1, Itamar Ben Shitrit2,3, Guy Hazan2,4
1From the Pediatric Department A, Saban Children's Hospital, Soroka University Medical Center.
Insights
Polymerase chain reaction (PCR) detects Shigella rapidly, but culture results help distinguish infection from carriage. Culture-positive Shigella cases in children indicate more severe illness and lower cycle threshold values.
Area of Science:
- Medical Microbiology
- Infectious Diseases
- Molecular Diagnostics
Background:
- Polymerase chain reaction (PCR) offers rapid and sensitive detection of Shigella in stool.
- Distinguishing between disease-associated Shigella and asymptomatic carriage remains a challenge.
- This study compared PCR-positive children with and without positive stool cultures.
Purpose of the Study:
- To compare clinical characteristics of children with Shigella detected by PCR.
- To differentiate between Shigella infection and carriage using stool culture results.
- To assess the correlation between PCR cycle threshold (Ct) values and disease severity.
Main Methods:
- Analysis of stool samples from children (<18 years) tested by multiplex PCR.
- Shigella PCR-positive samples underwent culture for species identification and antimicrobial susceptibility.
- Vesikari scale assessed disease severity; logistic regression and ROC analysis evaluated Ct values and culture results.
Main Results:
- Of 39,777 stools, 5.1% were Shigella PCR-positive; 43.9% of these were culture-positive.
- Culture-positive cases showed significantly lower Ct values (23 vs. 30) and higher rates of severe disease (71% vs. 54%).
- A Ct value of 28 predicted culture-positivity, and 27 predicted severe disease.
Conclusions:
- In children with Shigella PCR-positive results, culture-positive samples are associated with increased disease severity.
- Lower PCR cycle threshold (Ct) values correlate with culture-positivity and severe Shigella infection.
- Stool culture remains crucial for confirming active Shigella infection and assessing severity.
Background:
Detection of Shigella in stool by polymerase chain reaction (PCR) is rapid and highly sensitive but presents challenges in distinguishing between disease-associated and asymptomatic Shigella carriage. This study compared children with gastroenteritis who had Shigella identified in their stool by PCR-testing and a positive stool culture to those with Shigella identified by PCR-testing but a negative culture.
Methods:
All stool samples of outpatients and inpatients (<18 years) tested by multiplex-PCR at the Soroka University Medical Center laboratory between January 2020 and July 2024 were analyzed. Shigella PCR-positive samples underwent culture for species identification and antimicrobial susceptibility testing. The Vesikari scale was used to determine disease severity. Logistic regression assessed associations between culture-positivity and clinical findings, while receiver operating characteristic analysis evaluated the relationship between cycle threshold (Ct) values, culture-positivity and disease severity.
Results:
Among 39,777 stools tested by multiplex PCR, 2041 (5.1%) were Shigella -positive, of which 897 (43.9%) were also culture-positive. Among culture-positive cases, 77% grew S. sonnei and 18% S. flexneri . Antibiotic susceptibility testing showed 36% sensitivity to ceftriaxone and 77% to azithromycin. Culture-positive cases had lower Ct values than culture-negative cases [23 (95% confidence interval [CI]: 20-26) vs. 30 (95% CI: 25-36), P < 0.001]. Among 395 hospitalized children with Shigella PCR-positive samples, 167 (42%) had positive stool cultures. Severe disease was more common in culture-positive cases (71% vs. 54%, P < 0.001). A Ct value of 28 predicted culture-positivity (adjusted odds ratios = 6.97, 95% CI: 5.62-8.68; P < 0.001) and 27 predicted severe disease (adjusted odds ratios = 1.93, 95% CI: 1.20-3.12; P = 0.007).
Conclusions:
Among children with Shigella -positive PCR results, those with culture-positive samples exhibited greater disease severity and lower Ct values.
