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Chorioamnionitis caused by gram-negative bacteria as an etiologic factor in preterm birth
D J Sherman1, J Tovbin, T Lazarovich
1Department of Obstetrics and Gynaecology, Tel Aviv University, Assaf Harofeh Medical Centre, Zerifin, Israel.
Abstract:
The role and microbiological causes of infection and inflammation of the chorioamnion were studied in 85 patients with spontaneous preterm deliveries (< 37 weeks) and in 85 control patients with full term deliveries. Microorganisms were isolated from the freshly separated chorioamnion in 55% of preterm and 26% of term deliveries (p < 0.001). Isolation rates of gram-negative enteric bacteria were significantly higher in preterm deliveries than in term deliveries (p < 0.001), whereas differences in the isolation of other bacterial species were not significant. Histological chorioamnionitis was noted in 49% of preterm and 14% of term deliveries (p < 0.001), and was strongly associated with a positive chorioamniotic culture in both groups (p < 0.001). Histological chorioamnionitis was noted in 94%, 54%, and 4% of membranes with gram-negative rods, other microbial species and negative cultures, respectively (p < 0.001). Preterm deliveries were also associated with significantly higher rates of bacterial vaginosis (38% vs. 14%) and isolation of vaginal pathogens (85% vs. 65%). In the case of the majority (88%) of chorioamniotic isolates the same species was isolated in the vagina. The findings suggest that gram-negative enteric rods are important placental pathogens responsible for sub-clinical chorioamnionitis and possibly preterm birth. The findings support the concept that microorganisms ascending from the lower genital tract produce local inflammation, which may result in preterm labour and delivery.
Insights
Gram-negative enteric bacteria are linked to chorioamnionitis, a placental infection causing preterm birth. Ascending vaginal microorganisms trigger inflammation, leading to premature labor and delivery.
Area of Science:
- Obstetrics and Gynecology
- Infectious Diseases
- Perinatal Medicine
Background:
- Chorioamnionitis, infection and inflammation of the fetal membranes, is a known complication of pregnancy.
- The microbiological causes and role of chorioamnionitis in preterm birth require further elucidation.
Purpose of the Study:
- To investigate the microbiological etiology of chorioamnionitis in spontaneous preterm deliveries.
- To compare the prevalence of microorganisms and histological chorioamnionitis in preterm versus term deliveries.
Main Methods:
- A case-control study involving 85 patients with spontaneous preterm deliveries and 85 with term deliveries.
- Microbiological cultures of freshly separated chorioamnion and histological examination for chorioamnionitis.
- Assessment of bacterial vaginosis and vaginal pathogen isolation.
Main Results:
- Microorganisms were isolated from chorioamnion in 55% of preterm and 26% of term deliveries (p < 0.001).
- Gram-negative enteric bacteria were significantly more prevalent in preterm deliveries (p < 0.001).
- Histological chorioamnionitis was strongly associated with positive cultures, particularly gram-negative rods (p < 0.001).
Conclusions:
- Gram-negative enteric rods are significant placental pathogens contributing to sub-clinical chorioamnionitis and preterm birth.
- Ascending microorganisms from the lower genital tract likely induce local inflammation, precipitating preterm labor.
- Findings support the role of ascending vaginal infections in the pathogenesis of preterm delivery.