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Bacterial colonization of amniotic fluid in the presence of ruptured membranes
Abstract:
Amniotic fluid (AF) was collected from 37 selected patients by amniocentesis, aspiration through a pressure catheter, or aspiration at the time of cesarean section. The unspun AF was examined directly by Gram stain for bacteria and white blood cells (WBC) and was cultured. Thirteen AF cultures were positive, defined as growth on primary plating media which corresponded to greater than 10(2) colony-forming units (CFU) per milliliter. Almost equal numbers of aerobic and anaerobic bacteria were isolated. The presence of bacteria, but not WBC, on Gram stain of AF correlated significantly with a positive culture, which indicated that microscopic examination of AF would usually predict the culture result. Growth of greater than 10(2) CFU/ml from AF was significantly associated with clinical chorioamnionitis, but colonization also was observed in five afebrile patients, four of whom were in premature labor. In patients delivered by cesarean section, bacteria on Gram stain and a positive culture from AF each were significantly correlated with postpartum endometritis.
Insights
Microscopic examination of amniotic fluid (AF) can predict bacterial culture results, aiding in the diagnosis of chorioamnionitis and postpartum endometritis in pregnant patients.
Area of Science:
- Obstetrics and Gynecology
- Microbiology
- Clinical Diagnostics
Background:
- Amniotic fluid infection is a significant complication in pregnancy.
- Accurate and timely diagnosis of intra-amniotic infection is crucial for maternal and fetal outcomes.
Purpose of the Study:
- To evaluate the diagnostic utility of Gram stain and bacterial culture of amniotic fluid.
- To correlate amniotic fluid findings with clinical diagnoses of chorioamnionitis and postpartum endometritis.
Main Methods:
- Amniotic fluid samples were collected from 37 patients via amniocentesis, catheter aspiration, or cesarean section.
- Samples were analyzed by Gram stain for bacteria and white blood cells (WBC) and subjected to aerobic and anaerobic cultures.
- Positive cultures were defined as >10(2) colony-forming units (CFU)/mL.
Main Results:
- Thirteen (35%) amniotic fluid cultures were positive.
- Presence of bacteria on Gram stain significantly correlated with positive cultures.
- Amniotic fluid bacterial growth (>10(2) CFU/mL) was associated with clinical chorioamnionitis, including in some afebrile patients.
- In cesarean section deliveries, Gram stain and positive cultures correlated with postpartum endometritis.
Conclusions:
- Gram stain of amniotic fluid is a reliable predictor of culture results.
- Bacterial presence in amniotic fluid is linked to intra-amniotic infection and postpartum complications.
- Microscopic examination of amniotic fluid aids in diagnosing pregnancy-related infections.